Untitled Flashcards Set

Flashcard 1
Front: What are the two most common atoms in biology, and why are they significant?
Back:

• Carbon: Central to biochemistry; forms the backbone of most organic molecules.

• Hydrogen: Abundant; present in nearly all biological molecules and compounds.

Flashcard 2
Front: Describe the basic structure of an atom.
Back:

• Nucleus: Contains nearly all the mass; composed of protons (p⁺) and neutrons (n⁰).

• Electron Cloud: Electrons (e⁻) orbit the nucleus; in a neutral atom, the number of electrons equals the number of protons.

Flashcard 3
Front: How is an element identified using its atomic and mass numbers?
Back:

• Atomic Number: The number of protons in the nucleus (defines the element and never changes).

• Mass Number: The sum of protons and neutrons (expressed in Daltons, D).

Flashcard 4
Front: What are isotopes, and how do they differ?
Back:

• Isotopes: Variants of the same element that differ in the number of neutrons.

• Example: Carbon-12 vs. Carbon-14—both have the same number of protons but Carbon-14 has two extra neutrons.

• Stability is often highest when the number of protons equals the number of neutrons.

Flashcard 5
Front: How is the periodic table organized, and what is the importance of valence electrons?
Back:

• Columns (Groups): Elements with similar chemical reactivity due to the same number of valence (outermost) electrons.

• Rows (Periods): Elements with the same number of electron shells, influencing atomic size.

Flashcard 6
Front: What is the difference between a molecular formula, structural formula, ball-and-stick model, and space-filling model?
Back:

• Molecular Formula: Lists the number and type of atoms (e.g., CH₄ for methane).

• Structural Formula: Shows how atoms are bonded (e.g., a tetrahedral arrangement for methane).

• Ball-and-Stick Model: Provides a visual of the molecule’s shape.

• Space-Filling Model: Illustrates the probable electron cloud distribution around nuclei.

Flashcard 7
Front: Define a covalent bond and state the basic rules governing covalent bonding.
Back:

• Definition: A chemical bond formed by sharing 2 electrons between atoms.

• Rules:

  1. Formed by sharing a pair of electrons.

  2. Electrons are shared between the atoms involved.

  3. Atoms continue to form bonds until their outermost electron shell is filled (typically aiming for 8 valence electrons).

Flashcard 8
Front: What distinguishes a nonpolar covalent bond from a polar covalent bond?
Back:

• Nonpolar: Electrons are shared equally (e.g., H–H, C–C).

• Polar: Electrons are shared unequally, creating partial charges due to differences in electronegativity (e.g., H₂O, where oxygen pulls electrons closer).

Flashcard 9
Front: Explain the concept of electronegativity and its trend among common elements.
Back:

• Electronegativity: A measure of an atom's ability to attract shared electrons.

• Trend: Generally increases with the number of protons.

  • Approximate values: H (2.1) < C (2.5) < N (3.0) < O (3.5) < F (4.0).

Flashcard 10
Front: Describe hydrogen bonding and its importance in water.
Back:

• Hydrogen Bond: A weak bond between a hydrogen atom covalently bonded to an electronegative atom (like O) and a neighboring electronegative atom.

• In Water:

  • Responsible for high surface tension, capillary action, and many unique water properties.

Flashcard 11
Front: What causes the meniscus formation in water, and how is it related to capillary action?
Back:

• Meniscus Formation: Occurs where water meets a solid surface due to:

  • Cohesion: Attraction between water molecules.

  • Adhesion: Attraction between water molecules and the solid surface.

• Capillary Action: Water rises in narrow tubes (capillaries) due to the balance of cohesive and adhesive forces, aided by evaporation from the top.

Flashcard 12
Front: Why is ice less dense than liquid water?
Back:

• Ice: Forms an open crystalline lattice via hydrogen bonds, increasing spacing between molecules.

• Result: Lower density, which allows ice to float and insulate aquatic life in frozen lakes.

• Note: Although this explanation is widely taught, it is acknowledged that it may not be completely supported by current research.

Flashcard 13
Front: Define an ionic bond and describe the process of ion formation.
Back:

• Ionic Bond: A bond formed through the complete transfer of electrons, resulting in the formation of ions.

• Ion Formation:

  • Cations: Positively charged (loss of electrons).

  • Anions: Negatively charged (gain of electrons).

• Commonly occurs in salts and crystals (e.g., NaCl, MgCl₂).

Flashcard 14
Front: Why is MgCl₂ considered stronger than NaCl?
Back:

• Explanation:

  • Magnesium chloride involves a divalent magnesium ion (Mg²⁺) which creates a stronger electrostatic attraction with chloride ions compared to the monovalent sodium ion (Na⁺) in sodium chloride.

  • This leads to a higher lattice energy and a more stable ionic structure.

Flashcard 15
Front: What is the continuum of bonding from nonpolar covalent to ionic bonds?
Back:

• Continuum:

  • Nonpolar Covalent Bonds: Equal sharing of electrons.

  • Polar Covalent Bonds: Unequal sharing resulting in partial charges.

  • Ionic Bonds: Full electron transfer creating fully charged ions.

Flashcard 16
Front: What defines hydrophilic and hydrophobic molecules?
Back:

• Hydrophilic (Water-Loving):

  • Polar molecules and ions that dissolve readily in water (e.g., salt in water).

• Hydrophobic (Water-Hating):

  • Nonpolar molecules that do not mix well with water (e.g., oil in vinaigrettes or chicken noodle soup).

Flashcard 17
Front: What is a hydrophobic interaction, and why is it thermodynamically favorable?
Back:

• Hydrophobic Interaction:

  • The tendency of water to force nonpolar molecules together to minimize disruption of its hydrogen bond network.

• Biological Role:

  • Essential for the formation of cellular membranes and proper protein folding.

  • More significant with larger nonpolar molecules.

Flashcard 18
Front: Define van der Waals interactions and their role in molecular behavior.
Back:

• Van der Waals Interactions:

  • Weak attractions due to transient (temporary) dipoles in all molecules, including nonpolar ones.

• Role:

  • Help to hold molecules such as methanol together, contributing to overall molecular cohesion.

Flashcard 19
Front: Rank the following interactions from strongest to weakest as emphasized in this course: Covalent, hydrogen, ionic, hydrophobic, and van der Waals.
Back:

1. Covalent Bonds

2. Hydrogen Bonds

3. Ionic Bonds (noting their role in proteins)

4. Hydrophobic Interactions

5. Van der Waals Interactions

Flashcard 20
Front: What is required to properly balance a chemical equation?
Back:

• Balancing Principle:

  • The number of atoms for each element must be equal on both the reactant and product sides of the equation.

Flashcard 21
Front: Define a mole and explain how it is determined for any given molecule.
Back:

• Mole:

  • A measure that relates the mass of a substance (in grams) to its atomic or molecular weight (in g/mol).

  • Calculation:

    • Number of moles = mass (g) / molecular weight (g/mol).

Flashcard 22
Front: What is molarity, and how does solution dilution affect it?
Back:

• Molarity (M):

  • One mole of a solute dissolved in enough water to make 1 liter of solution.

• Dilution Note:

  • Adding extra solvent increases the volume, thus lowering the molarity of the solution.

Flashcard 23
Front: What distinguishes a strong acid from a weak acid in solution?
Back:

• Strong Acid:

  • Completely dissociates in solution (releases all available H⁺ ions).

• Weak Acid:

  • Partially and reversibly dissociates (common in biological systems).

Flashcard 24
Front: Describe the dissociation reaction of the carboxyl group (-COOH).
Back:

• Reaction:

  • -COOH → -COO⁻ + H⁺

• Significance:

  • The carboxyl group functions as a weak acid in biological compounds.

Flashcard 25
Front: How does a weak base, such as an amino group (-NH₂), behave in solution?
Back:

• Reaction:

  • -NH₂ + H⁺ → -NH₃⁺

• Note:

  • It partially and reversibly accepts hydrogen ions, classifying it as a weak base in biological contexts.

Flashcard 26
Front: What does the pH scale measure and how is it defined?
Back:

• pH Scale:

  • Measures the concentration of hydrogen ions (H⁺) in a solution.

• Definition:

  • pH = –log [H⁺]

  • A pH of 7 corresponds to an H⁺ concentration of 10⁻⁷ M, which is considered neutral.

Flashcard 27
Front: How do ionic bonds form, and what are the resultant stable configurations called?
Back:

• Ionic Bond Formation:

  • Involves the complete transfer of electrons between atoms.

• Stable Configurations:

  • The resulting ions (cations and anions) form stable arrangements in salts and crystalline structures.

Flashcard 28
Front: Explain why water’s hydrogen bonding is crucial for its unique properties such as high surface tension.
Back:

• Hydrogen Bonding in Water:

  • Creates strong cohesive forces between water molecules.

• Effects:

  • High Surface Tension: Supports insects on water surfaces.

  • Capillary Action: Facilitates the rise of water in narrow tubes and plant capillaries.

Flashcard 29
Front: What are the roles of cohesion and adhesion in the behavior of water?
Back:

• Cohesion:

  • The attraction between water molecules due to hydrogen bonding.

• Adhesion:

  • The attraction between water molecules and other surfaces, which contributes to phenomena like meniscus formation.

Flashcard 30
Front: In the continuum of bonding, what factors determine whether a bond is nonpolar, polar, or ionic?
Back:

• Nonpolar: Equal sharing of electrons due to similar electronegativities.

• Polar: Unequal sharing when there is a moderate difference in electronegativity, leading to partial charges.

• Ionic: Full transfer of electrons when there is a significant difference in electronegativity, resulting in charged ions.

Flashcard Set: Acid–Base Titration & Buffers

Flashcard 1
Q: What is the reaction equation for acetic acid titration?
A: CH₃COOH ⇌ CH₃COO⁻ + H⁺

Flashcard 2
Q: What does the half-equivalence point in a titration indicate?
A: It is the point where 50% of the acid has been neutralized, meaning [CH₃COOH] = [CH₃COO⁻] and pH = pKa.

Flashcard 3
Q: Define pKa and explain its significance.
A: pKa is the negative logarithm of the acid dissociation constant (Kₐ). It indicates the strength of an acid; at pH = pKa, the acid is 50% dissociated.

Flashcard 4
Q: How does the addition of OH⁻ affect the acetic acid equilibrium?
A: OH⁻ reacts with H⁺, shifting the equilibrium to the right (Le Chatelier’s principle), accelerating conversion of acetic acid to acetate and gradually increasing pH.

Flashcard 5
Q: What is a buffer and how does it function?
A: A buffer is a solution that resists changes in pH by neutralizing added acids or bases through its equimolar acid-base conjugate pair, typically most effective at the half-equivalence point.

Flashcard Set: Molecular Structure & Polymerization

Flashcard 6
Q: What distinguishes a linear molecule from a cyclic molecule in organic chemistry?
A: Linear molecules have carbon atoms linked in a straight chain (e.g., octane in gasoline), while cyclic molecules have carbons arranged in a ring (e.g., glucose).

Flashcard 7
Q: What is polymerization by condensation, and what is released during the process?
A: Polymerization (condensation reaction) is the formation of covalent bonds between monomers, releasing a water molecule with each bond formed.

Flashcard 8
Q: What is hydrolysis, and why is it important in biology?
A: Hydrolysis is the process of breaking covalent bonds by adding water, which releases energy; it is crucial for digesting polymers (proteins, starches) into monomers.

Flashcard 9
Q: Define a peptide bond.
A: A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another, releasing water in a condensation reaction.

Flashcard 10
Q: What is meant by the primary structure of a protein?
A: The primary structure is the linear sequence of amino acids linked by peptide bonds, which ultimately determines the protein’s higher-order structure and function.

Flashcard Set: Protein Secondary, Tertiary, and Quaternary Structures

Flashcard 11
Q: How are secondary structures in proteins typically characterized?
A: They include alpha helices and beta pleated sheets, stabilized by hydrogen bonds between backbone atoms, with specific proportions possible (e.g., 20% alpha helix, 50% beta sheet).

Flashcard 12
Q: What unique property does proline have, and how does it affect protein structure?
A: Proline’s side chain forms a cyclic structure attached to its amino nitrogen, limiting rotation and often marking the end of secondary structure elements.

Flashcard 13
Q: What factors primarily influence the tertiary structure of a protein?
A: Tertiary structure is driven by interactions among side chains, including hydrophobic interactions, ionic bonds, and disulfide bonds.

Flashcard 14
Q: Explain the role of disulfide bonds in protein structure.
A: Disulfide bonds form between the sulfhydryl groups of cysteine residues through oxidation, stabilizing the protein’s tertiary structure by linking distant regions.

Flashcard 15
Q: Describe an example where disulfide bonds play a crucial role in protein strength.
A: In keratin, which is rich in alpha helices and disulfide bonds, these covalent links provide mechanical strength and resistance to stress (they can be broken and reformed).

Flashcard 16
Q: What is quaternary structure, and how is it exemplified in hemoglobin?
A: Quaternary structure refers to the assembly of multiple polypeptide chains into a larger complex; hemoglobin is a tetramer composed of two alpha and two beta subunits held together by non-covalent interactions.

Flashcard 17
Q: How can a single amino acid substitution affect protein function?
A: A substitution (e.g., replacing glutamic acid with valine in hemoglobin) can change charge and polarity, altering the protein’s shape and leading to diseases like sickle cell anemia.

Flashcard Set: Protein Folding, Stability, and Cellular Dynamics

Flashcard 18
Q: What happens to a protein during denaturation, and how can it sometimes refold?
A: Denaturation involves the unfolding of a protein (loss of secondary and tertiary structure) which can be reversible under ideal conditions, demonstrating that the primary structure encodes folding information.

Flashcard 19
Q: Why does protein denaturation in crowded cellular environments often lead to irreversible aggregation?
A: Denatured proteins may interact inappropriately with one another in a crowded environment, leading to misfolded aggregates as seen when cooking eggs or meat.

Flashcard 20
Q: What is protein turnover, and why is it significant?
A: Protein turnover is the continuous breakdown and resynthesis of proteins in cells, ensuring proper function and regulation through defined half-lives.

Flashcard 21
Q: What role do molecular chaperones play in protein folding?
A: Chaperones bind to newly synthesized or partially folded proteins to prevent improper interactions, allowing them time to achieve their correct three-dimensional structure.

Flashcard Set: Nucleic Acids – Structure and Polymerization

Flashcard 22
Q: What are the three basic components of a nucleotide?
A: A five-carbon sugar, a phosphate group (forming part of the backbone), and a nitrogenous base (which determines identity).

Flashcard 23
Q: How do ribose and deoxyribose differ, and where are they found?
A: Ribose (in RNA) has two hydroxyl groups, whereas deoxyribose (in DNA) lacks one oxygen, possessing only one hydroxyl group. They are numbered from 1′ to 5′.

Flashcard 24
Q: Differentiate between purines and pyrimidines.
A: Purines (adenine and guanine) have two aromatic rings, while pyrimidines (cytosine, thymine in DNA, and uracil in RNA) have one aromatic ring.

Flashcard 25
Q: Describe the polymerization process of DNA and RNA.
A: Polymerization occurs via a condensation reaction where the 3′ hydroxyl group of one nucleotide bonds to the 5′ phosphate group of the next, forming a phosphodiester linkage and releasing water.

Flashcard 26
Q: What is the significance of the 5′ to 3′ directionality in nucleic acids?
A: The 5′ to 3′ orientation creates the sugar-phosphate backbone of DNA and RNA, determining the direction in which enzymes synthesize and read the strand.

Flashcard 27
Q: How do complementary base pairs in DNA contribute to its stability?
A: Purine-pyrimidine pairing (A-T with two hydrogen bonds, G-C with three hydrogen bonds) maintains uniform spacing and stability; the antiparallel arrangement and inward-facing bases protect genetic information.

Flashcard 28
Q: What unique structural feature allows RNA to form complex shapes?
A: RNA can fold into loops and stem-loop structures due to intra-strand hydrogen bonding, enabling it to perform catalytic and regulatory functions similar to enzymes.

Flashcard 29
Q: Why is the sugar-phosphate backbone important in nucleic acids?
A: It not only provides structural stability but also places the nitrogenous bases on the interior, reducing exposure to the external environment and lowering mutation risks.

Flashcards: Energy, ATP, and Enzymes

1. Q: What are the two main types of metabolic reactions?
   A:

   • Anabolic reactions: Build complex molecules from simpler ones and require energy.

   • Catabolic reactions: Break down complex molecules into simpler ones and release energy.

2. Q: What is the significance of ATP in cellular energy transfer?
   A: ATP captures free energy from exergonic reactions, storing it in high-energy bonds, which can then drive endergonic reactions in the cell.

3. Q: Define free energy (ΔG) and its role in biochemical reactions.
   A: ΔG = ΔH – TΔS. A negative ΔG indicates a spontaneous (exergonic) reaction where energy is released, while a positive ΔG indicates a non-spontaneous (endergonic) reaction that requires energy input.

4. Q: How does the first law of thermodynamics apply to energy conversions in biology?
   A: It states that energy is conserved during any conversion process—the total initial energy equals the total final energy.

5. Q: What does the second law of thermodynamics imply about energy dispersal?
   A: Energy spontaneously disperses from a localized, ordered state to a more spread out, disordered state (increased entropy), which drives energy conversions.

6. Q: What is the function of enzymes in biochemical reactions?
   A: Enzymes act as catalysts by lowering the activation energy required for a reaction without being consumed in the process.

7. Q: Outline the three phases of an enzyme-catalyzed reaction.
   A:

   • Initiation: Substrates bind to the enzyme’s active site forming an enzyme–substrate complex.

   • Transition State Facilitation: The enzyme stabilizes the transition state, lowering the activation energy.

   • Termination: Products, which have lower affinity for the active site, are released, freeing the enzyme for another cycle.

8. Q: What are the three main catalytic mechanisms used by enzymes?
   A:

   • Orientation: Aligns substrates properly for reaction.

   • Characterized Environment: Creates a specific chemical milieu to favor the reaction.

   • Induced Strain: Distorts substrate bonds, lowering the energy barrier for the reaction.

9. Q: What are cofactors, and why are they important for enzyme activity?
   A: Cofactors are non-protein molecules (e.g., metal ions or organic molecules like heme) that are required by some enzymes for proper function.

10. Q: Explain enzyme saturation and turnover rate.
    A: When all enzyme active sites are occupied by substrates, the enzyme is saturated. The turnover rate is the maximum number of reactions an enzyme can catalyze per second, ranging from about 1 reaction/second (lysozyme) to millions/second (catalase).

Flashcards: Sugars and Carbohydrates

11. Q: What are the three classifications of carbohydrates?
    A:

    • Monosaccharides: Simple sugars.

    • Disaccharides: Formed by linking two monosaccharides.

    • Polysaccharides: Long chains of monosaccharide units (can be branched or unbranched).

12. Q: What is the general formula for carbohydrate monomers?
    A: Carbohydrates are typically a multiple of CH₂O. Aldoses have a carbonyl group at the end, while ketoses have the carbonyl group in the middle.

13. Q: How do hydroxyl groups influence the reactivity of sugars?
    A: All sugars contain multiple hydroxyl groups, making them easily convertible into alcohols and highly reactive in forming glycosidic bonds.

14. Q: What are structural isomers and stereoisomers in the context of sugars?
    A:

    • Structural isomers: Same molecular formula but different arrangements of atoms (e.g., varying positions of the carbonyl group).

    • Stereoisomers (Optical isomers): Molecules with the same structural formula but different spatial arrangements, resulting in non-superimposable mirror images.

15. Q: Provide a mnemonic to distinguish α-glucose from β-glucose.
    A:

    • α-Glucose: “Alpha = Away” (the hydroxyl on the anomeric carbon is oriented away from the CH₂OH group).

    • β-Glucose: “Beta = Beside” (the hydroxyl on the anomeric carbon is on the same side as the CH₂OH group).

16. Q: What is a glycosidic linkage and why is it important?
    A: A glycosidic linkage is the bond formed between two monosaccharides via a dehydration reaction. It is crucial in forming disaccharides and polysaccharides.

17. Q: Compare the significance of α-1,4 and β-1,4 glycosidic linkages.
    A:

    • α-1,4 Linkages: Lead to the formation of starch (amylose in its unbranched form, amylopectin in its branched form) in plants and glycogen in animals.

    • β-1,4 Linkages: Form cellulose, a rigid, unbranched polymer with extensive hydrogen bonding, providing structural support in plant cell walls.

18. Q: What are oligosaccharides?
    A: Oligosaccharides are carbohydrates composed of approximately 20–30 sugar units, representing an intermediate complexity between disaccharides and polysaccharides.

Flashcards: Lipids

19. Q: What are the primary functions of lipids in biological systems?
    A: Lipids are involved in energy storage, forming cell membranes, capturing light energy (e.g., carotenoids), serving as hormones and vitamins (e.g., steroids), and providing thermal insulation.

20. Q: Describe the structure of a fatty acid and its amphiphilic nature.
    A: A fatty acid consists of a carboxyl group attached to a long hydrocarbon chain, making it amphiphilic—having both hydrophilic (carboxyl group) and hydrophobic (hydrocarbon chain) properties.

21. Q: How do soaps utilize the amphiphilic properties of fatty acids?
    A: The hydrophobic hydrocarbon chains attach to dirt (non-polar substances), while the hydrophilic carboxyl groups interact with water, enabling the removal of dirt.

22. Q: What constitutes a triglyceride?
    A: A triglyceride is formed by a glycerol molecule linked by ester bonds to three fatty acid molecules. They are synthesized via dehydration reactions.

23. Q: What is the structure and significance of phospholipids?
    A: Phospholipids consist of a glycerol backbone, two hydrophobic fatty acid tails, and one hydrophilic head group. They self-assemble into bilayers, forming the basic structure of cell membranes.

24. Q: How does temperature affect membrane fluidity, and what adaptations do cells employ?
    A: Lower temperatures cause membranes to become more rigid. Cells adapt by incorporating unsaturated fatty acids (with double bonds that create kinks), increasing spacing between phospholipids and enhancing membrane fluidity.

25. Q: What are isoprenes and steroids, and how do they relate to lipid structure?
    A:

    • Isoprenes: Basic five-carbon units that build up carotenoids like β-carotene, which can be split to form vitamin A.

    • Steroids: Lipids such as cholesterol, vitamin D₂, and cortisol, which serve various structural and signaling functions in the body.

Atomic Structure & Chemical Bonds

Flashcard 1
Q: What are the predominant atoms found in biological systems?
A: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, Sulfur, plus ionic components like Sodium, Magnesium, and Chlorine.

Flashcard 2
Q: Describe the basic structure of an atom.
A: An atom consists of a nucleus (containing protons and neutrons) and an electron cloud; electrical neutrality is achieved when the number of electrons equals the number of protons.

Flashcard 3
Q: How is the periodic table organized?
A: It is arranged into groups (columns) with similar valence electrons and periods (rows) that reflect trends such as atomic size based on electron shells.

Flashcard 4
Q: What are isotopes and why are they significant in biology?
A: Isotopes are atoms of the same element with different numbers of neutrons; they affect mass and stability without altering chemical identity.

Flashcard 5
Q: Define covalent, ionic, and hydrogen bonds.
A:

• Covalent bonds: Atoms share electrons to form strong connections (e.g., in methane).

• Ionic bonds: Electrons are transferred between atoms, resulting in charged ions.

• Hydrogen bonds: Weak attractions where a hydrogen atom bonded to an electronegative atom interacts with another electronegative atom (crucial in water).

Flashcard 6
Q: What distinguishes polar covalent bonds from non-polar covalent bonds?
A: Polar bonds share electrons unequally due to differences in electronegativity, creating partial charges, whereas non-polar bonds share electrons equally.

Flashcard 7
Q: How do hydrophilic and hydrophobic molecules differ?
A: Hydrophilic molecules are water-loving and typically polar, while hydrophobic molecules are water-repellent and non-polar.

Acid–Base Chemistry & pH

Flashcard 8
Q: What defines an acid and a base in biological systems?
A: Acids donate hydrogen ions (H⁺), while bases accept H⁺; for instance, acids often contain a carboxyl group and bases can have amino groups.

Flashcard 9
Q: How is the pH of a solution determined?
A: pH is based on the concentration of hydrogen ions; a pH of 7 is neutral, corresponding to an H⁺ concentration of 10⁻⁷ M.

Flashcard 10
Q: In an acid–base titration with acetic acid, what happens at the half equivalence point?
A: Half of the acetic acid is neutralized, so [CH₃COOH] equals [CH₃COO⁻], and the pH equals the pKa of acetic acid.

Flashcard 11
Q: What is the role of buffers in a biological system?
A: Buffers maintain pH by containing comparable amounts of a weak acid and its conjugate base, neutralizing added acids or bases.

Macromolecules & Polymerization

Flashcard 12
Q: What is polymerization in biological systems?
A: It is the process where monomers join together via covalent bonds (condensation reaction) with the release of water, requiring an energy input.

Flashcard 13
Q: How does hydrolysis differ from polymerization?
A: Hydrolysis is the reverse process where water is added to break covalent bonds between monomers, releasing energy.

Flashcard 14
Q: What is the primary structure of a protein?
A: It is the linear sequence of amino acids linked by peptide bonds from the amino to the carboxyl terminus.

Flashcard 15
Q: Why is the peptide bond unique?
A: It forms by condensation (releasing water) and has partial double bond character that restricts rotation, influencing protein structure.

Flashcard 16
Q: How do complementary base pairing and antiparallel orientation contribute to DNA stability?
A: A pairs with T (or U in RNA) and G with C via hydrogen bonds, and the antiparallel arrangement maximizes these interactions within the double helix.

Flashcard 17
Q: What components make up a nucleotide?
A: A five-carbon sugar, a phosphate group, and a nitrogenous base.

Flashcard 18
Q: How do RNA and DNA differ regarding their sugar components?
A: RNA contains ribose (with two hydroxyl groups) while DNA contains deoxyribose (lacking one hydroxyl group).

Flashcard 19
Q: What defines monosaccharides, disaccharides, and polysaccharides?
A:

• Monosaccharides: Simple sugars.

• Disaccharides: Two monosaccharides linked by dehydration reactions.

• Polysaccharides: Long chains of monosaccharide units that can be linear or branched.

Flashcard 20
Q: How do glycosidic linkages differ in starch versus cellulose?
A: Starch features α-1,4 linkages (allowing a more flexible, helical structure), while cellulose has β-1,4 linkages that create a rigid, linear structure.

Flashcard 21
Q: What structural change occurs when a sugar forms a cyclic structure?
A: A hydroxyl group reacts with the carbonyl group to form a ring, creating an anomeric center with either an alpha (α) or beta (β) configuration.

Flashcard 22
Q: What are the key functions of lipids in cells?
A: They serve as energy storage, structural components in cell membranes, and participate in hormone synthesis and thermal insulation.

Flashcard 23
Q: Describe the structure and role of phospholipids in membrane formation.
A: Phospholipids consist of a glycerol backbone, two fatty acid tails (hydrophobic), and one head group (hydrophilic), and they self-assemble into bilayers with heads facing water and tails inward.

Flashcard 24
Q: How do unsaturated fatty acids affect membrane fluidity?
A: Double bonds in unsaturated fatty acids introduce kinks, increasing spacing between phospholipids and enhancing fluidity, especially at lower temperatures.

Energy, ATP & Enzymes

Flashcard 25
Q: What is the difference between anabolic and catabolic reactions?
A: Anabolic reactions build complex molecules from simpler ones and require energy, while catabolic reactions break down complex molecules and release energy.

Flashcard 26
Q: State the First Law of Thermodynamics as it applies to biological systems.
A: Energy is conserved in all reactions; the total energy before and after a process remains constant.

Flashcard 27
Q: What does the Second Law of Thermodynamics state about energy dispersal?
A: Energy spontaneously disperses from concentrated regions to more uniform distributions, increasing entropy.

Flashcard 28
Q: Write and explain the free energy equation used in biochemistry.
A: ΔG = ΔH – TΔS, where ΔH is the change in enthalpy, T is the absolute temperature, and ΔS is the change in entropy. A negative ΔG indicates a spontaneous, exergonic reaction.

Flashcard 29
Q: How does ATP function as the universal energy currency?
A: ATP stores energy in its high-energy bonds; hydrolysis of ATP (to ADP + Pi) releases energy that drives cellular processes.

Flashcard 30
Q: What is activation energy and why are enzymes important in overcoming it?
A: Activation energy is the minimum energy required to initiate a reaction; enzymes lower this barrier to increase reaction rates without being consumed.

Flashcard 31
Q: Define catalysis and the role of enzymes in catalyzing biochemical reactions.
A: Catalysis is the process of speeding up a chemical reaction via a catalyst (commonly an enzyme) that lowers the activation energy by stabilizing the transition state.

Flashcard 32
Q: What are cofactors and how do they support enzyme function?
A: Cofactors are non-protein molecules or ions (like metal ions or coenzymes) that assist enzymes in achieving optimal activity. 

Section I. Membrane Structure, Fluidity, and Transport

1. Q: What is the basic structure of a phospholipid?
   A: It has a hydrophilic (polar) head and one or more hydrophobic (nonpolar) fatty acid tails.
   
   

2. Q: How do phospholipids arrange themselves in water?
   A: They spontaneously form a bilayer, with polar heads facing the aqueous environment and hydrophobic tails packed in the interior.
   
   

3. Q: What is the role of van der Waals forces in membranes?
   A: They stabilize the interactions among hydrophobic fatty acid tails in the inner core of the bilayer.
   
   

4. Q: How do saturated fatty acids affect membrane rigidity?
   A: Saturated fatty acids pack tightly, resulting in a more rigid and less permeable membrane.
   
   

5. Q: What effect do unsaturated fatty acids have on membranes?
   A: Their kinks prevent tight packing, which increases membrane fluidity and permeability.
   
   

6. Q: Describe the fluid mosaic model.
   A: It portrays the membrane as a dynamic, fluid structure with lipids and proteins moving laterally, while proteins are embedded as a mosaic.
   
   

7. Q: What distinguishes integral membrane proteins from peripheral ones?
   A: Integral proteins span the membrane (often via α-helices) and are embedded in the lipid core, whereas peripheral proteins associate loosely with the surface.
   
   

8. Q: Why can integral proteins diffuse laterally but not “flip-flop”?
   A: Their fixed orientation is maintained by hydrophilic regions that would not energetically favor crossing the hydrophobic core.
   
   

9. Q: What is freeze-fracture electron microscopy used for?
   A: It is used to split the bilayer along the weakly interacting lipid leaflets, revealing protein distributions and bilayer organization.
   
   

10. Q: How do artificial membrane experiments help determine permeability?
    A: By separating two compartments with a lipid bilayer and tracking the diffusion of solutes, researchers can assess membrane permeability.
    
    

11. Q: What molecules can readily pass through a typical lipid bilayer?
    A: Small, nonpolar molecules like O₂, CO₂, and even water.
    
    

12. Q: What role do channel proteins play in passive transport?
    A: They form aqueous pores for ions and small molecules, often gating in response to stimuli.
    
    

13. Q: How does carrier-mediated facilitated diffusion work?
    A: Carrier proteins bind a specific substrate and undergo a conformational change to transport it across the membrane.
    
    

14. Q: What is the primary difference between passive and active transport?
    A: Passive transport moves substances down their concentration gradient without energy input, whereas active transport uses energy to move substances against their gradient.
    
    

15. Q: How does primary active transport differ from secondary active transport?
    A: Primary active transport directly uses ATP (e.g., Na⁺/K⁺ pump), while secondary active transport uses the energy stored in ion gradients.
    
    

16. Q: What is osmosis?
    A: The diffusion of water across a selectively permeable membrane from high to low water concentration.
    
    

17. Q: What happens to a cell in a hypertonic solution?
    A: Water exits the cell, causing it to shrink.
    
    

18. Q: What occurs when a cell is placed in a hypotonic solution?
    A: Water enters the cell, possibly causing swelling.
    
    

19. Q: How do membranes maintain selective permeability?
    A: Through the chemical nature of the bilayer and the use of specific transport proteins.
    
    

20. Q: What is lateral mobility in membranes?
    A: The movement of lipids and proteins sideways within the plane of the membrane.
    
    

Section II. Energy Metabolism, Glycolysis, and Redox Reactions

21. Q: What is the overall net yield of ATP from glycolysis per molecule of glucose?
    A: Glycolysis produces a net gain of 2 ATP molecules.
    
    

22. Q: How many NADH molecules are produced during glycolysis per glucose?
    A: 2 NADH molecules.
    
    

23. Q: What are the two phases of glycolysis?
    A: The energy investment phase and the energy harvesting (payoff) phase.
    
    

24. Q: What enzyme catalyzes the first step of glycolysis?
    A: Hexokinase, which phosphorylates glucose to trap it in the cell.
    
    

25. Q: How is fructose-1,6-bisphosphate formed?
    A: Via phosphorylation of fructose-6-phosphate by phosphofructokinase-1 (PFK-1).
    
    

26. Q: What is substrate-level phosphorylation?
    A: The direct transfer of a phosphate group from a high-energy substrate to ADP, forming ATP.
    
    

27. Q: Why is the oxidation of glyceraldehyde-3-phosphate (G3P) crucial in glycolysis?
    A: It produces NADH and a high-energy intermediate (1,3-BPG) that drives ATP synthesis.
    
    

28. Q: How does coupling reactions drive glycolysis?
    A: Unfavorable steps are pulled forward by coupling with strongly exergonic reactions or ATP hydrolysis.
    
    

29. Q: What is NAD⁺’s role in metabolism?
    A: NAD⁺ acts as an electron carrier, becoming reduced to NADH during glycolysis and other pathways.
    
    

30. Q: What is the significance of redox potential (E°)?
    A: It indicates a molecule’s tendency to gain or lose electrons and relates directly to the free energy change (ΔG).
    
    

31. Q: Describe the purpose of the citric acid cycle.
    A: It fully oxidizes acetyl-CoA to CO₂ while generating NADH, FADH₂, and GTP/ATP for use in oxidative phosphorylation.
    
    

32. Q: How many NADH and FADH₂ molecules are generated per acetyl-CoA in the citric acid cycle?
    A: 3 NADH and 1 FADH₂ per acetyl-CoA.
    
    

33. Q: What is the main function of the electron transport chain (ETC)?
    A: To oxidize NADH and FADH₂, pump protons to create a gradient, and drive ATP synthesis via ATP synthase.
    
    

34. Q: Which complex in the ETC is responsible for oxidizing NADH?
    A: Complex I (NADH:Ubiquinone oxidoreductase).
    
    

35. Q: What is the role of ubiquinone in the ETC?
    A: It shuttles electrons between Complexes I/II and Complex III.
    
    

36. Q: What drives ATP synthesis in mitochondria?
    A: The proton gradient (proton motive force) established by the ETC.
    
    

37. Q: How does ATP synthase produce ATP?
    A: Protons flow through its F₀ channel, rotating the F₁ catalytic unit, which synthesizes ATP from ADP and Pi.
    
    

38. Q: What is fermentation and why is it important?
    A: Fermentation regenerates NAD⁺ in the absence of oxygen, allowing glycolysis to continue.
    
    

39. Q: What is the difference between lactic acid and alcoholic fermentation?
    A: Lactic acid fermentation reduces pyruvate to lactate, while alcoholic fermentation converts pyruvate to ethanol and CO₂.
    
    

40. Q: How are redox reactions coupled to ATP production in aerobic respiration?
    A: The oxidation of NADH and FADH₂ drives electron transport, which pumps protons and establishes a gradient used by ATP synthase.
    
    

Section III. Photosynthesis

41. Q: What is the overall chemical reaction for photosynthesis?
    A: 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂.
    
    

42. Q: Where do the light reactions of photosynthesis take place?
    A: In the thylakoid membranes of the chloroplasts.
    
    

43. Q: What is the main pigment in photosynthesis?
    A: Chlorophyll a, which absorbs blue and red light.
    
    

44. Q: How do light-harvesting antenna complexes function?
    A: They collect photons and transfer excitation energy via resonance energy transfer to the reaction center.
    
    

45. Q: What happens in Photosystem II (PSII)?
    A: PSII absorbs light (exciting P680), catalyzes water splitting to produce O₂, and initiates electron transport.
    
    

46. Q: What is the function of Photosystem I (PSI)?
    A: PSI absorbs light (exciting P700) and re-excites electrons for the reduction of NADP⁺ to NADPH.
    
    

47. Q: What is cyclic electron transport in photosynthesis?
    A: It recycles electrons from PSI back to the ETC to produce additional ATP without forming NADPH.
    
    

48. Q: What role does the Calvin cycle play in photosynthesis?
    A: It uses ATP and NADPH from the light reactions to fix CO₂ into sugars.
    
    

49. Q: How does Rubisco contribute to the Calvin cycle?
    A: Rubisco catalyzes the fixation of CO₂ to RuBP, forming 3-phosphoglycerate (3-PGA).
    
    

50. Q: What are the main differences between chloroplast and mitochondrial membranes?
    A: Chloroplasts have thylakoid membranes arranged in grana for light reactions, whereas mitochondria have highly folded inner membranes (cristae) for ATP production.
    
    

51. Q: How do the light reactions generate a proton gradient?
    A: By pumping protons from the stroma into the thylakoid lumen during electron transfer.
    
    

52. Q: Why do plants appear green?
    A: Chlorophyll absorbs blue and red light, reflecting and transmitting green wavelengths.
    
    

53. Q: What is photorespiration and why is it considered wasteful?
    A: It occurs when Rubisco binds O₂ instead of CO₂, leading to a loss of fixed carbon and energy.
    
    

54. Q: What adaptations help plants reduce photorespiration?
    A: Mechanisms like C₄ metabolism and CAM pathways concentrate CO₂ at the site of Rubisco.
    
    

Section IV. Cell Division and the Cell Cycle

55. Q: What is the purpose of the cell cycle?
    A: To ensure that a cell duplicates its components, including DNA, exactly once before division.
    
    

56. Q: What are the main phases of interphase?
    A: G1 (cell growth), S (DNA replication), and G2 (preparation for mitosis).
    
    

57. Q: What is the primary event during the S phase?
    A: DNA replication, resulting in two identical sister chromatids.
    
    

58. Q: What occurs during mitosis?
    A: The nuclear division, where chromosomes condense, align, separate, and are allocated to daughter nuclei.
    
    

59. Q: What are the key stages of mitosis?
    A: Prophase, Prometaphase, Metaphase, Anaphase, and Telophase.
    
    

60. Q: How does cytokinesis differ in animal and plant cells?
    A: Animal cells form a contractile ring (actin-myosin) to pinch off, while plant cells form a cell plate that matures into a new cell wall.
    
    

61. Q: What is the spindle assembly checkpoint?
    A: A control mechanism that ensures all chromosomes are correctly attached to the spindle before anaphase begins.
    
    

62. Q: How does meiosis contribute to genetic diversity?
    A: By halving the chromosome number and incorporating crossing over and independent assortment, which creates novel allele combinations.
    
    

63. Q: What is the difference between meiosis I and meiosis II?
    A: Meiosis I is reductional, separating homologous chromosomes; meiosis II is equational, separating sister chromatids.
    
    

64. Q: What is a karyotype and how is it used?
    A: A karyotype is an organized profile of an organism’s chromosomes used to study their number, size, and structure.
    
    

65. Q: What is the Law of Segregation?
    A: It states that each individual carries two alleles for a trait and these alleles segregate into gametes so that each gamete carries only one allele.
    
    

66. Q: How do cell cycle checkpoints prevent errors in cell division?
    A: They verify conditions such as DNA replication completeness and proper chromosome attachment before the cell proceeds to the next phase.
    
    

67. Q: What role do cyclins and CDKs play in the cell cycle?
    A: They regulate progression through the cell cycle by activating or inhibiting key processes at checkpoints.
    
    

68. Q: Why is random chromosome segregation unlikely in mitosis?
    A: Because the probability of each of 46 chromosomes segregating correctly by chance is astronomically low, necessitating precise control mechanisms.
    
    

69. Q: How does non-disjunction affect cell division?
    A: It causes unequal distribution of chromosomes, leading to aneuploidy and potential developmental disorders.
    
    

Section V. Mendelian Genetics and Heredity

70. Q: What did Mendel’s pea plant experiments demonstrate?
    A: That traits are inherited as discrete units (genes) with dominant and recessive alleles, following predictable ratios.
    
    

71. Q: Define genotype and phenotype.
    A: Genotype is the genetic makeup (alleles) of an organism; phenotype is the observable trait resulting from the genotype.
    
    

72. Q: What is a homozygous genotype?
    A: When both alleles for a trait are the same (e.g., RR or rr).
    
    

73. Q: What does heterozygous mean?
    A: When an organism has two different alleles for a trait (e.g., Rr).
    
    

74. Q: What is the typical phenotypic ratio in the F₂ generation of a monohybrid cross?
    A: Approximately 3:1 (dominant:recessive).
    
    

75. Q: Explain the Law of Independent Assortment.
    A: Genes for different traits segregate independently during gamete formation, leading to diverse trait combinations.
    
    

76. Q: How can a test cross determine an organism’s genotype?
    A: By crossing an organism with a dominant phenotype with a homozygous recessive individual, revealing hidden recessive alleles by the appearance of recessive offspring.
    
    

77. Q: What is an allele?
    A: A variant form of a gene.
    
    

78. Q: How did Mendel’s work lay the foundation for modern genetics?
    A: It demonstrated that inheritance follows specific patterns and is based on discrete units (genes), later supported by molecular evidence.
    
    

79. Q: What role does probability play in predicting genetic outcomes?
    A: Punnett squares and probability rules (multiplication and addition) predict the likelihood of genotypes and phenotypes in offspring.
    
    

80. Q: Why is discrete variation important in Mendelian genetics?
    A: It allows traits to be clearly categorized (e.g., round vs. wrinkled peas), facilitating predictable inheritance patterns.
    
    

Section VI. Chemical Bonds and Molecular Structure

81. Q: What are covalent bonds and why are they important in biology?
    A: Covalent bonds involve the sharing of electrons between atoms, forming the strong bonds that hold together biological macromolecules.
    
    

82. Q: How do atoms achieve a stable electron configuration in covalent bonding?
    A: They share electrons to complete their valence electron shells, often achieving an octet.
    
    

83. Q: What is electronegativity?
    A: A measure of an atom's ability to attract electrons in a bond.
    
    

84. Q: Give an example of a polar covalent bond.
    A: The bond between oxygen and hydrogen in water, where oxygen is more electronegative, creating partial charges.
    
    

85. Q: What are ionic bonds?
    A: Bonds formed by the complete transfer of electrons from one atom to another, resulting in oppositely charged ions.
    
    

86. Q: How do hydrogen bonds differ from covalent bonds?
    A: Hydrogen bonds are weaker interactions that form when a hydrogen atom bonded to an electronegative atom is attracted to another electronegative atom.
    
    

87. Q: What is the significance of hydrogen bonding in water?
    A: It gives water its high surface tension, cohesive and adhesive properties, and plays a critical role in its solvent abilities.
    
    

88. Q: How do hydrophobic interactions contribute to protein folding?
    A: Nonpolar amino acid side chains aggregate to avoid water, driving the formation of a hydrophobic core in proteins.
    
    

89. Q: What is a disulfide bond and why is it important for protein structure?
    A: A covalent bond between the sulfhydryl groups of two cysteine residues that stabilizes tertiary or quaternary structure.
    
    

90. Q: Define van der Waals interactions.
    A: Weak, transient attractions between molecules due to temporary dipoles.
    
    

91. Q: How does the periodic table organization relate to chemical bonding?
    A: Elements in the same group have similar valence electron configurations, leading to similar bonding properties.
    
    

92. Q: What are isotopes and why are they significant in biology?
    A: Atoms of the same element with different numbers of neutrons; some isotopes (like Carbon-14) are used in dating and metabolic studies.
    
    

93. Q: How does water’s high surface tension benefit living organisms?
    A: It allows insects to walk on water and helps in capillary action in plants.
    
    

94. Q: What is capillary action and what forces are involved?
    A: The ability of water to flow in narrow spaces against gravity, driven by cohesion and adhesion.
    
    

Section VII. Acids, Bases, and pH

95. Q: What defines an acid in solution?
    A: An acid donates hydrogen ions (H⁺) when dissolved in water.
    
    

96. Q: How do strong acids differ from weak acids?
    A: Strong acids completely dissociate in water, while weak acids only partially dissociate.
    
    

97. Q: What is a base and how does it function in solution?
    A: A base accepts hydrogen ions and often releases hydroxide ions (OH⁻) in solution.
    
    

98. Q: What does the pH scale measure?
    A: The concentration of hydrogen ions in a solution, indicating its acidity or basicity.
    
    

99. Q: How is pH calculated?
    A: pH = –log[H⁺], where [H⁺] is the molarity of hydrogen ions.
    
    

100. Q: What is a buffer system and why is it important?
     A: Buffers resist changes in pH upon addition of small amounts of acid or base, maintaining a stable environment in biological systems.
     
     

Section VIII. Polymerization, Proteins, and Nucleic Acids

101. Q: What is a condensation (polymerization) reaction?
     A: A reaction where monomers are joined to form a polymer with the release of water.
     
     

102. Q: What is hydrolysis?
     A: The process of breaking bonds in a polymer by adding water, releasing monomers.
     
     

103. Q: How are peptide bonds formed?
     A: By a condensation reaction between the carboxyl group of one amino acid and the amino group of another.
     
     

104. Q: What is the primary structure of a protein?
     A: The linear sequence of amino acids in the polypeptide chain.
     
     

105. Q: What stabilizes the secondary structure of proteins?
     A: Hydrogen bonds between backbone C=O and N–H groups, forming alpha helices and beta sheets.
     
     

106. Q: What is the tertiary structure of a protein?
     A: The overall three-dimensional folding of a single polypeptide chain, driven by hydrophobic interactions, ionic bonds, and disulfide bridges.
     
     

107. Q: What is quaternary structure?
     A: The assembly of multiple polypeptide chains into a functional protein complex.
     
     

108. Q: How does the structure of proline affect protein folding?
     A: Proline’s cyclic structure restricts backbone flexibility and often terminates alpha helices or beta sheets.
     
     

109. Q: What are nucleotides and what are their components?
     A: The building blocks of nucleic acids, composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.
     
     

110. Q: What is the difference between DNA and RNA nucleotides?
     A: DNA contains deoxyribose (lacking one hydroxyl group) and uses thymine, while RNA contains ribose and uses uracil.
     
     

111. Q: How do nucleotides polymerize into nucleic acids?
     A: Through a condensation reaction forming phosphodiester bonds between the 3′ hydroxyl of one nucleotide and the 5′ phosphate of the next.
     
     

112. Q: What is complementary base pairing?
     A: In DNA, adenine pairs with thymine (A–T) via two hydrogen bonds, and guanine pairs with cytosine (G–C) via three hydrogen bonds.
     
     

113. Q: Why is the double helix structure of DNA important?
     A: It provides stability through hydrogen bonding and a protective sugar-phosphate backbone on the outside.
     
     

114. Q: What role do ribozymes play?
     A: They are RNA molecules with catalytic activity, supporting the hypothesis of an RNA world.
     
     

Section IX. Energy, ATP, and Enzymes

115. Q: What is metabolism?
     A: The sum of all chemical reactions in a cell, divided into anabolic (building) and catabolic (breaking down) processes.
     
     

116. Q: What does the first law of thermodynamics state?
     A: Energy is conserved in any conversion; it is neither created nor destroyed.
     
     

117. Q: What drives energy transformations in cells according to the second law of thermodynamics?
     A: The spontaneous dispersal of energy, leading to an increase in entropy.
     
     

118. Q: Define free energy (ΔG).
     A: ΔG = ΔH – TΔS, representing the energy available to do work in a reaction.
     
     

119. Q: What indicates a spontaneous reaction?
     A: A negative ΔG, meaning the reaction releases energy.
     
     

120. Q: How is ATP hydrolysis linked to cellular energy?
     A: Hydrolysis of ATP to ADP and Pi releases about –12 kcal/mol, providing energy for various cellular processes.
     
     

121. Q: What is the role of enzymes in metabolic reactions?
     A: Enzymes lower the activation energy, increasing the reaction rate without being consumed.
     
     

122. Q: How do enzymes achieve substrate specificity?
     A: Through precise active site geometry that only fits specific substrates.
     
     

123. Q: What is meant by enzyme saturation?
     A: When all active sites of an enzyme are occupied, the reaction rate reaches a maximum.
     
     

124. Q: What are cofactors and why are they important?
     A: Non-protein molecules (such as metal ions or coenzymes) that assist enzymes in catalysis.
     
     

125. Q: Why are activation energy barriers significant in biology?
     A: They prevent uncontrolled reactions; enzymes lower these barriers to enable life-sustaining processes at moderate temperatures.
     
     

Section X. Sugars, Lipids, and Their Roles

126. Q: What is the general formula for carbohydrates?
     A: They often follow a formula that is a multiple of CH₂O.
     
     

127. Q: What distinguishes monosaccharides from disaccharides and polysaccharides?
     A: Monosaccharides are simple sugars, disaccharides are formed by two linked monosaccharides, and polysaccharides are long chains of monosaccharides.
     
     

128. Q: What is the difference between aldoses and ketoses?
     A: Aldoses have a terminal carbonyl group, while ketoses have the carbonyl group in the middle of the molecule.
     
     

129. Q: How does glucose cyclize to form a ring structure?
     A: The hydroxyl group on carbon 5 reacts with the carbonyl carbon (C1), forming a hemiacetal ring.
     
     

130. Q: What are anomers in cyclic sugars?
     A: They are isomers that differ in the configuration at the anomeric carbon (alpha or beta).
     
     

131. Q: What type of glycosidic linkage is found in starch?
     A: α-1,4 glycosidic bonds.
     
     

132. Q: What distinguishes cellulose from starch structurally?
     A: Cellulose is composed of β-1,4 glycosidic bonds, which lead to a rigid, linear polymer.
     
     

133. Q: What are fatty acids and what is their structure?
     A: Fatty acids consist of a long hydrocarbon chain with a terminal carboxyl group.
     
     

134. Q: How do phospholipids self-assemble into bilayers?
     A: Their amphiphilic nature causes the hydrophobic tails to avoid water while the hydrophilic heads interact with water, forming a bilayer.
     
     

135. Q: What determines membrane fluidity in lipid bilayers?
     A: The degree of saturation of fatty acids and the presence of cholesterol can modulate fluidity.
     
     

136. Q: How do triglycerides form?
     A: By esterification of glycerol with three fatty acids, releasing water in a condensation reaction.
     
     

137. Q: What role do lipids play in energy storage?
     A: They provide a dense, long-term energy store because they are high in energy per unit mass.