Study_Guide_for_Exam_2_2025

Study Guide for Exam 2

Saturated and Unsaturated Fats

• Saturated fats:

  • Characteristics: Solid at room temperature, straight-chain fatty acids, no double bonds between carbon atoms.

  • Examples: Butter, lard.

  • Behavior at low temperature: Remain solid and do not gel easily.

• Unsaturated fats:

  • Characteristics: Liquid at room temperature, contain one or more double bonds causing kinks in the chain.

  • Examples: Olive oil, fish oil.

  • Behavior at low temperature: Remain liquid and do not crystallize easily.

Levels of Structure of a Protein

• Primary Structure:

  • Sequence of amino acids in a polypeptide chain.

• Secondary Structure:

  • Regular patterns (alpha helices and beta sheets) formed by hydrogen bonds between backbone atoms.

• Tertiary Structure:

  • 3D shape formed due to interactions between R groups, including hydrogen bonds, ionic bonds, and disulfide bridges.

• Quaternary Structure:

  • Assembly of multiple polypeptide chains into a functional protein.

Polysaccharides: Starch, Cellulose, Glycogen, Chitin

• Monomers: Glucose.

• Bonds: Glycosidic bonds.

• Functions:

  • Starch: Energy storage in plants.

  • Cellulose: Structural component in plant cell walls.

  • Glycogen: Energy storage in animals.

  • Chitin: Structural component in fungal cell walls and exoskeletons of arthropods.

• Characteristics:

  • Starch: Branched structure, easy to digest.

  • Cellulose: Linear, not easily digestible by humans.

  • Glycogen: Highly branched.

  • Chitin: Tough and flexible.

Comparison Between Dehydration and Hydrolysis

• Dehydration Synthesis: Forming larger molecules from monomers by removing water.

  • Used to build polysaccharides, proteins, and nucleic acids.

• Hydrolysis: Breaking down larger molecules by adding water.

  • Used to digest polysaccharides, proteins, and nucleic acids into monomers.

Types of Sugars

• Monosaccharides: Simple sugars; e.g., glucose, fructose.

• Disaccharides: Two monosaccharides; e.g., sucrose (glucose + fructose).

• Polysaccharides: Long chains of monosaccharides; e.g., starch, glycogen.

• Triacylglycerol: Glycerol + three fatty acids; represents a storage form of fat.

Biological Macromolecules

• Lipids:

  • Composition: Glycerol and fatty acids.

  • Function: Energy storage, membrane structure.

  • Characteristics: Hydrophobic (non-polar).

• Proteins:

  • Composition: Amino acids.

  • Function: Catalysts, structural support, signaling.

  • Characteristics: Can be polar or non-polar based on R groups.

• Carbohydrates:

  • Composition: Sugars (monosaccharides).

  • Function: Energy source, structural roles.

  • Characteristics: Polar due to hydroxyl groups.

• Nucleic Acids:

  • Composition: Nucleotides.

  • Function: Store and transmit genetic information.

  • Characteristics: Polar due to phosphate groups.

Amino Acids

• Common Parts: Amino group, carboxyl group, hydrogen, and R group.

• Distinctive Parts: The R group varies among different amino acids.

• Asymmetric Carbon: Also called alpha carbon, the central carbon atom is asymmetric.

• Bonds Between Amino Acids: Peptide bonds.

• R Group Classes: Non-polar, polar, and charged.

Denaturation and Renaturation

• Denaturation: Loss of protein structure due to environmental factors (e.g., heat, pH), leading to loss of function.

• Renaturation: Process by which a denatured protein returns to its functional shape under appropriate conditions.

Purpose of DNA, RNA, and Protein

• DNA: Stores genetic information.

• RNA: Plays a role in protein synthesis and gene expression.

• Proteins: Essential for structure, function, and regulation of cells and organisms.

Nucleotides

• Components: Nitrogenous base, 5-carbon sugar, phosphate group.

• Base Pair Matches: A-T (DNA), C-G (DNA), A-U (RNA).

DNA Structure and Characteristics

• Backbone: Sugar-phosphate backbone connected by covalent bonds.

• Hydrogen Bonds: Between nitrogenous bases in complementary pairs.

• Differences between RNA and DNA: RNA has ribose sugar and uracil instead of thymine, and is usually single-stranded.

Central Dogma

• Process: DNA -> RNA -> Protein

Cell Organelles

• Nucleus: Contains DNA and is the control center of the cell.

• Ribosome: Site of protein synthesis.

• Mitochondria: Powerhouse of the cell, site of ATP production.

• Cytoskeleton: Provides structural support, facilitates cellular movement.

• Cilia & Flagella: Motility structures.

• Endoplasmic Reticulum (ER): Synthesizes proteins (rough ER) and lipids (smooth ER).

• Golgi Body: Modifies and packages proteins for secretion or delivery.

• Cell Membrane: Semi-permeable barrier controlling entry and exit of substances.

• Lysosome: Contains enzymes for digestion of waste materials.

• Vesicles: Transport materials within the cell.

• Chloroplasts: Site of photosynthesis in plant cells.

• Vacuole: Storage and maintenance of turgor pressure in plant cells.

• Endomembrane System: Network of membranes involved in transport and communication within the cell.

Microscopy Techniques

• Light Microscopy: Uses light to observe samples, limited resolution.

• Electron Microscopy: Uses electrons for higher resolution imaging of cell structures.

Prokaryotes vs Eukaryotes

• Prokaryotes: Simple, single-celled organisms without a nucleus (e.g., bacteria).

• Eukaryotes: Complex cells with a nucleus and membrane-bound organelles (e.g., plants, animals).

Cell Structure Labels

• Be able to label a diagram of an animal cell, including mitochondria, nucleus, ER, and Golgi body.

Cytoskeleton

• Types: Microfilaments, intermediate filaments, microtubules.

• Proteins: Actin (microfilaments), tubulin (microtubules).

Cell Junctions

• Plasmodesmata: Channels in plant cells allowing substance flow between cells.

• Tight Junctions: Seal epithelial cells together to prevent leakage.

• Gap Junctions: Allow communication between neighboring cells.

• Desmosomes: Provide mechanical stability by anchoring cells together.

Membrane Fluidity

• Cell membrane fluidity affected by temperature, cholesterol content, and fatty acid composition.

Transport Mechanisms

• Osmosis: Movement of water across a semipermeable membrane.

• Passive Transport: Movement of substances across membranes without energy input (diffusion, facilitated diffusion).

• Active Transport: Movement of substances against their gradient, requires ATP.

• Diffusion: Spontaneous movement of particles from high to low concentration.

Cell Membrane

• Structure: Phospholipid bilayer, embedded proteins.

• Function: Protects and organizes cell components; regulates transport.

• Cholesterol: Helps maintain membrane fluidity.

Fluid Mosaic Model

• Describes the flexible nature of the phospholipid bilayer and movement of proteins within the membrane.

Membrane Proteins

• Integral Proteins: Embedded within the lipid bilayer, often spanning it.

• Peripheral Proteins: Loosely attached to the surface of membranes.

• Transmembrane Proteins: Type of integral protein that extends across the membrane.

Phospholipid Properties

• Parts: Hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails.

Water Passage

• Water crosses cell membranes through aquaporins or by simple diffusion due to concentration gradients.

Membrane Potential

• Voltage difference across a cell membrane due to distribution of ions.

Potassium Movement

• Movement of potassium across cells requires energy, often through active transport mechanisms.

Exocytosis and Pinocytosis

• Exocytosis: Process of expelling materials from the cell.

• Pinocytosis: Cellular uptake of fluids and molecules.

Facilitated Diffusion

• Passive transport enabled by transport proteins for larger or polar molecules.

Tonicity

• Hypertonic: Higher solute concentration outside cell, causes cell to shrink.

• Hypotonic: Lower solute concentration outside cell, causes cell to swell.

• Isotonic: Equal solute concentration, results in no net movement of water.

Sodium-Potassium Pump

• Active transport mechanism maintaining cell potential by moving sodium out and potassium into the cell, requiring ATP.

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Membrane Receptor Functions

• Signal Direction: Receptors facilitate communication between cells and their environment.

Proteins Role

• Functions:

  • Join cells together: intracellular joining functions.

  • Cell recognition: identifying self from non-self.

  • Transport: assist in moving substances across membranes.

Active Transport and ATP

• Active transport relies on ATP to move substances against their concentration gradient.

Amino Acid Behavior in Water

• Ionization of amino acids in water results in amphipathic behavior, acting as both an acid and a base.

Stages of Cell Signaling

• Three Stages: Reception, Transduction, Response.

  • Characteristics:

    • Reception: Detection of signaling molecule by receptor.

    • Transduction: Conversion of the signal into a cellular response.

    • Response: Result of signaling pathway activation (e.g., enzyme activation, gene expression).

Types of Receptors

• Different types exist including G protein-coupled receptors, receptor tyrosine kinases, and ion channel receptors, each with specific binding mechanisms.

Ligand Definition

• Ligand: A molecule that binds to a receptor to initiate a biological response.

Steroid Hormones and Receptor Interaction

• Steroid hormones pass through cell membranes and bind to intracellular receptors to influence gene expression.

G Protein Signaling Pathway

• Example: Epinephrine activates a G protein-coupled receptor, leading to an intracellular signaling cascade.

Receptor Tyrosine Kinase Signaling Pathway

• Example: Growth factors bind to receptor tyrosine kinases, causing dimerization and phosphorylation, activating multiple signaling pathways.

Ion Channel Receptor Signaling Pathway

• Example: Neurotransmitters bind to ion channels, causing them to open and allowing ions to flow across membranes, influencing neuronal activity.

Types of Cell Signaling

• Local Signaling: Communication between nearby cells (e.g., paracrine signaling).

• Long-Distance Signaling: Involves hormones traveling through the bloodstream to distant targets (e.g., endocrine signaling).