Macromolecules and Cellular Respiration: Study Notes for Anatomy & Physiology

CARBOHYDRATES

Overview of Carbohydrates

• Carbohydrates are sugars, starches, and related compounds that serve as a primary energy source for cells.

• They also have structural roles (e.g., in cell membranes and receptors) and contribute to dietary fiber.

• General formula: (CH2O)n; they are hydrates of carbon.

Monosaccharides

• Single sugar units (monomers) such as glucose, dextrose, fructose, galactose.

• Common formulas: Glucose (C6H12O6), Fructose, Galactose.

• Hexoses (6-carbon sugars) and Pentoses (5-carbon sugars) are important types.

Disaccharides

• Composed of two monosaccharides joined by a glycosidic bond.

• Examples:

  • Sucrose: glucose + fructose (table sugar)

  • Lactose: glucose + galactose (milk sugar)

  • Maltose: glucose + glucose

• Disaccharides are broken down by hydrolysis and formed by dehydration synthesis.

Polysaccharides

• Polymers of monosaccharides; serve as energy storage or structural molecules.

• Glycogen: main storage form in animals (liver, muscle).

• Starch: storage form in plants; digestible by humans.

• Cellulose: structural component in plants; indigestible by humans, provides dietary fiber.

LIPIDS

Overview of Lipids

• Contain C, H, and O (sometimes P or N); hydrophobic and insoluble in water.

• High energy content: ~9 kcal/g.

• Include fats, oils, waxes, phospholipids, steroids, and eicosanoids.

Fatty Acids

• Long hydrocarbon chains with a terminal carboxylic acid group.

• Types:

  • Saturated fatty acids: no double bonds; solid at room temperature; found in animal fats.

  • Unsaturated fatty acids: one or more double bonds; liquid at room temperature; found in plant oils and fish.

  • Trans fats: artificially hydrogenated oils; increase risk of heart disease.

Triglycerides (Neutral Fats)

• Composed of three fatty acids bonded to glycerol.

• Main function: energy storage, insulation, and protection.

Phospholipids

• Contain a phosphate group; amphipathic (hydrophilic head, hydrophobic tails).

• Major component of cell membranes; form bilayers.

Steroids

• Lipids with a four-ring structure; includes cholesterol, steroid hormones (e.g., estrogen, cortisol), and vitamin D precursor.

• Cholesterol is essential for membrane structure and hormone synthesis.

Eicosanoids

• Derived from arachidonic acid; includes prostaglandins, thromboxanes, leukotrienes.

• Regulate inflammation, blood flow, and other functions.

NUCLEIC ACIDS

Structure and Function

• Polymers of nucleotides; include DNA and RNA.

• Each nucleotide: nitrogenous base (adenine, guanine, cytosine, thymine/uracil), pentose sugar (ribose or deoxyribose), and phosphate group.

• Functions:

  • Genetic material (DNA)

  • Energy transfer (ATP, GTP)

  • Signaling (cAMP)

DNA and RNA

• DNA: double helix, stores genetic information.

• RNA: single-stranded, involved in protein synthesis and gene regulation.

PROTEINS

Structure and Types

• Polymers of amino acids (contain C, H, O, N, S).

• Functions: enzymes, structural support, transport, signaling, immune defense.

• Amino acids have an amino group, carboxylic acid group, and R group (side chain).

• Levels of protein structure:

  • Primary: sequence of amino acids

  • Secondary: alpha helices and beta sheets (hydrogen bonding)

  • Tertiary: overall 3D shape (folding)

  • Quaternary: arrangement of multiple polypeptide subunits

• Stabilized by ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bridges.

Protein Denaturation

• Loss of structure and function due to heat, pH changes, or chemicals.

• Denatured proteins cannot perform their biological roles.

Enzymes

• Biological catalysts that speed up chemical reactions by lowering activation energy.

• Highly specific for substrates; often named with the suffix "-ase" (e.g., lactase, DNA polymerase).

• Work via the enzyme-substrate complex mechanism (lock-and-key or induced fit models).

• Enzyme activity can be regulated by inhibitors (competitive, non-competitive, allosteric) and environmental factors (temperature, pH).

METABOLISM & CELLULAR RESPIRATION

Metabolic Pathways

• Metabolism: sum of all chemical reactions in the body.

• Pathways are regulated by enzymes and feedback inhibition.

• Catabolic pathways break down molecules to release energy; anabolic pathways build molecules.

Cellular Respiration

• Process by which cells extract energy from nutrients to form ATP.

• Divided into:

  • Anaerobic respiration: does not require oxygen; produces 2 ATP per glucose (glycolysis and fermentation).

  • Aerobic respiration: requires oxygen; produces 30-32 ATP per glucose (Krebs cycle, electron transport chain).

The ATP/ADP Cycle

• ATP is hydrolyzed to ADP, releasing energy for cellular processes.

• ADP is recycled back to ATP using energy from cellular respiration.

• ATP is used for mechanical work, transport, and chemical synthesis.

Key Equations

• General formula for carbohydrate: $C_n(H_2O)_n$

• ATP hydrolysis: $ATP + H_2O \rightarrow ADP + P_i + \text{energy}$

• Cellular respiration (aerobic): $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}$

Additional info:

• Some details (e.g., specific page references, figures) are omitted for clarity and focus on core concepts.

• Tables and diagrams referenced in the original notes are described in text for accessibility.