Introduction to Biological Chemistry Flashcards

Comprehensive question-and-answer study flashcards covering key topics in introductory general, organic, and biological chemistry.

How is matter present in the human body across all three states of matter?

Matter is present as solids (such as bones and teeth), liquids (such as blood plasma and intracellular fluid), and gases (such as oxygen and carbon dioxide).

How many elements occur in the human body in greater than trace amounts?

12 elements occur in the body in greater than trace amounts.

Which four elements make up 96% of the body's total mass?

Oxygen, carbon, hydrogen, and nitrogen.

What is the definition of an atom?

An atom is the smallest unit of matter that retains the unique chemical properties of a chemical element.

What are the three subatomic particles, their locations within the atom, and their electrical charges?

1. Protons: Located in the nucleus, positive charge ($+1$).
2. Neutrons: Located in the nucleus, neutral/no charge ($0$).
3. Electrons: Located in electron shells orbiting the nucleus, negative charge ($-1$).

Why is an atom considered electrically neutral?

An atom is electrically neutral because the number of negatively charged electrons equals the number of positively charged protons.

What atomic characteristic differs between different elements?

Different elements have different numbers of protons (atomic number).

What is an isotope?

An isotope is an alternative form of an element that has the same number of protons but a different number of neutrons.

Do different isotopes of the same element have different chemical properties?

No, isotopes of the same element have the same chemical properties because they possess the same number of valence electrons.

What is a radioisotope?

A radioisotope is an unstable isotope that spontaneously breaks down (decays) and emits radiation.

What are some medical and scientific uses of radioisotopes?

Radioisotopes are used in diagnostic medical imaging (e.g., iodine-131 for thyroid scans), radiation therapy for cancer treatment, and biological research tracking.

What is the valence shell of an atom?

The valence shell is the outermost electron shell of an atom.

What determines whether an atom is chemically stable or chemically reactive?

Whether its valence shell is completely filled with electrons (chemically stable/unreactive) or incomplete (chemically reactive).

What is the octet rule?

The octet rule states that atoms tend to react or bond in ways that leave them with 8 electrons in their valence shell (except the first shell, which is full with 2).

Which type of chemical bond results from the complete transfer of electrons between atoms?

An ionic bond.

How does an ionic bond form, and what is a classic example?

An ionic bond forms when one atom transfers electrons to another, creating positively and negatively charged ions that attract each other (e.g., sodium chloride, $NaCl$).

What general term is usually used to describe ionic compounds?

Salts.

What are the definitions of an ion, a cation, and an anion?

An ion is an atom or group of atoms with an electrical charge; a cation is a positively charged ion; an anion is a negatively charged ion.

Which type of bond forms as a result of the sharing of electrons?

A covalent bond.

Which bond type is stronger and more common in biological molecules: ionic or covalent?

Covalent bonds are stronger and more common in human biological molecules.

How are single, double, and triple covalent bonds represented in structural formulas?

A single bond is indicated by a single solid line ($-$), a double bond by a double solid line ($=$), and a triple bond by a triple solid line ($\equiv$).

What is the difference between a polar covalent bond and a nonpolar covalent bond?

In a nonpolar covalent bond, electrons are shared equally between atoms; in a polar covalent bond, electrons are shared unequally, creating partial positive ($\delta+$) and partial negative ($\delta-$) charges.

Give an example of a polar molecule, state whether it dissolves in water, and give the term for its water affinity.

Water ($H_2O$) or glucose; polar molecules dissolve in water and are described as hydrophilic ("water-loving").

Give an example of a nonpolar molecule, state whether it dissolves in water, and give the term for its water affinity.

Triglycerides (fats/oils); nonpolar molecules do not dissolve in water and are described as hydrophobic ("water-fearing").

What does the term amphipathic mean?

Amphipathic describes a molecule that contains both polar (hydrophilic) and nonpolar (hydrophobic) regions.

Give an example of an amphipathic molecule and describe how it interacts with water.

Phospholipids; they do not completely dissolve, but instead self-assemble into structures like cell membranes where polar heads face water and nonpolar tails avoid water.

Which type of chemical bond results from an attraction between a partial positive charge on a hydrogen atom and a partial negative charge on another polar molecule?

A hydrogen bond.

How are hydrogen bonds visually represented in chemical diagrams?

Hydrogen bonds are indicated by a dotted line or dashed line.

Is an individual hydrogen bond strong or weak, and what is the biological significance of many hydrogen bonds working together?

An individual hydrogen bond is weak, but many hydrogen bonds acting together provide major collective structural support and stability (such as in DNA strands and protein folding).

Define solution, solvent, solute, and concentration.

A solution is a homogeneous mixture; the solvent is the dissolving substance (usually liquid); the solute is the dissolved substance; concentration is the amount of solute present in a given volume of solution.

Which general category of biological molecules lacks carbon (with few exceptions) and consists of simple structures?

Inorganic compounds.

What are four major types of inorganic compounds?

Water, acids, bases, and salts.

What happens to an acid, a base, and a salt when dissolved in water?

1. Acid: Dissociates to release hydrogen ions ($H^+$).
2. Base: Dissociates to release hydroxide ions ($OH^-$) or absorb $H^+$ ions.
3. Salt: Dissociates into cations and anions, neither of which is $H^+$ or $OH^-$ .

What does the pH scale measure, what is its numeric range, and how much does concentration change per unit?

The pH scale measures hydrogen ion concentration ($[H^+]$); its range is 0 to 14; each unit change represents a 10-fold (1000%) change in $[H^+]$.

What are the pH ranges for acids, bases, and neutral substances?

Acids: pH less than 7 ($\text{pH} < 7$); Bases: pH greater than 7 ($\text{pH} > 7$); Neutral: pH equal to 7 ($\text{pH} = 7$; e.g., pure water).

What is the normal pH range of human blood?

The normal pH range of human blood is 7.35 to 7.45.

Why is acid/base balance critical in the body, and what is a buffer?

pH balance is critical because changes in pH alter molecular shapes and disrupt body functions; a buffer is a chemical compound or system that resists rapid changes in pH by binding or releasing $H^+$ ions.

How does an electrolyte form, and what are its key properties?

An electrolyte forms when an inorganic salt, acid, or base dissociates into ions in water; electrolytes can conduct electrical currents in solution.

Which two ions in body fluids are critical for generating electrical signals in nerve cells and muscle cells?

Sodium ions ($Na^+$) and potassium ions ($K^+$).

Which category of chemical compounds contains carbon, is usually large and complex (macromolecules)?

Organic compounds.

What are the four main types of organic compounds in the body?

Carbohydrates, lipids, proteins, and nucleic acids.

Define polymer and monomer.

A monomer is a small, repeating molecular subunit; a polymer is a large macromolecule composed of many covalently linked monomers.

What is a carbon skeleton?

The carbon skeleton is the chain or ring of carbon atoms that forms the basic structural framework of an organic molecule.

What are the four types of lipids discussed in lecture, along with an example and function of each?

1. Triglycerides: e.g., body fat; functions in long-term energy storage and thermal insulation.
2. Phospholipids: e.g., lecithin; forms cell membrane bilayers.
3. Steroids: e.g., cholesterol; serves as membrane component and hormone precursor.
4. Eicosanoids: e.g., prostaglandins; functions in inflammatory responses and signaling.

What are the three main subtypes of carbohydrates based on size, and which subtype do glucose, lactose, and glycogen belong to?

Subtypes: Monosaccharides, disaccharides, and polysaccharides.

• Glucose: Monosaccharide
• Lactose: Disaccharide
• Glycogen: Polysaccharide

What is the general function of nucleic acids, two main types, and their monomer unit?

Function: Store and express genetic information. Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Monomer: Nucleotide.

What are the three basic chemical components of a nucleotide?

1. A 5-carbon pentose sugar (ribose or deoxyribose)
2. A phosphate group
3. A nitrogenous base

How does the structure of DNA differ from RNA?

DNA is double-stranded, contains deoxyribose sugar, and uses thymine ($T$); RNA is single-stranded, contains ribose sugar, and uses uracil ($U$).

Why is ATP called the "energy currency of the cell" and how does it differ from a standard nucleotide?

ATP contains three phosphate groups (instead of one); breaking its high-energy phosphate bonds releases energy directly usable by cellular processes.

What is the monomer unit of proteins, and what type of bond joins them together?

The monomer unit is an amino acid, and monomers are joined by covalent peptide bonds.

How many different amino acids occur in significant quantities in the human body?

20 different amino acids.

What is a generic name given to a molecule consisting of three amino acids linked together?

A tripeptide.

What determines the specific three-dimensional structure and overall function of each protein?

The specific sequence of amino acids in the polypeptide chain.

Describe the four structural levels of a protein.

1. Primary: Linear sequence of amino acids.
2. Secondary: Local structural patterns like alpha-helices and beta-pleated sheets stabilized by hydrogen bonds.
3. Tertiary: Overall 3D folded shape of a single polypeptide chain.
4. Quaternary: Shape formed by two or more polypeptide chains joined together.

What is protein denaturation, what factors cause it, and what is its biological outcome?

Denaturation is an irreversible change in a protein's 3D shape caused by extreme heat or pH shifts; it destroys structural folding and results in complete loss of biological function.