Cellular Metabolism and Genetic Information Essentials

Metabolism: Sum of all chemical reactions in the body.
Cellular Metabolism: Sum of all chemical reactions in a cell, typically in pathways.
Anabolism (Synthesis): Small molecules built into larger ones; requires energy.
- Example: Dehydration synthesis, where $H_{2}O$ is produced to form polysaccharides, proteins, triglycerides.
Catabolism (Decomposition): Larger molecules broken down into smaller ones; releases energy.
- Example: Hydrolysis, which uses $H_{2}O$ to split substances, reversing dehydration synthesis.

Enzymes: Globular protein catalysts that increase chemical reaction rates by lowering activation energy.
Substrate specific, bind at their active site, not consumed.
Factors altering conformation: Excess heat, radiation, electricity, specific chemicals, extreme pH, some poisons.
Denaturation: Irreversible change in enzyme shape, leading to inactivation.
Metabolic Pathways: Sequence of enzyme-controlled reactions.
- Enzyme names often contain substrate name and end in "-ase" (e.g., lactase, protease).
- Rate-limiting enzyme: Controls entire pathway, often inhibited by the end product (negative feedback).
Cofactor: Non-protein substance activating an enzyme (ion, element, coenzyme).
Coenzyme: Organic cofactor, often a vitamin.

Energy: Capacity to change something or do work.
Cellular Respiration: Process transferring energy from molecules for cellular use.
ATP (Adenosine Triphosphate): Main energy-carrying molecule.
- Composed of Adenine, Ribose, and 3 phosphates.
- High-energy bonds link 2nd and 3rd phosphates.
- Energy is stored converting ADP + P to ATP, and released when ATP breaks down to ADP + P.
- Energy transfer: $40\%$ chemical energy, $60\%$ released as heat (maintains body temperature).

Overall equation: $C{6}H{12}O{6} + 6O{2} \to 6CO{2} + 6H{2}O + \text{energy (32-36 ATP, heat)}$ .
Requires glucose and $O_{2}$ .
Aerobic reactions: Require $O_{2}$ , produce most ATP.
Anaerobic reactions: Do not require $O_{2}$ , produce little ATP.
Stages: 1. Glycolysis (anaerobic), 2. Citric Acid Cycle (aerobic), 3. Electron Transport Chain/Oxidative Phosphorylation (aerobic).

First stage of glucose breakdown; 10 enzymatic steps.
Occurs in cytosol; anaerobic.
Glucose (6-carbon) is broken down into 2 pyruvic acid (3-carbon) molecules, 2 net ATP, and high-energy electrons.
If no $O_{2}$ , pyruvic acid converts to lactic acid, decreasing ATP production.
If $O_{2}$ is present, pyruvic acid enters mitochondria for aerobic pathways.

Pyruvic acid moves from cytosol to mitochondria and is used to produce Acetyl CoA.
Citric Acid Cycle (Krebs Cycle):
- Occurs in mitochondria.
- Acetyl Co-A is broken down into $CO_{2}$ , 2 ATP (per glucose), and high-energy electrons.
Electron Transport Chain/Oxidative Phosphorylation:
- Occurs in the inner mitochondrial membrane.
- Energy from electrons is transferred to ATP synthase, catalyzing ADP phosphorylation to ATP.
- $H_{2}O$ is formed; oxygen is the final electron acceptor.
- Produces 32-36 ATP per glucose molecule.
- Proteins and fats can also be broken down by aerobic respiration.

DNA (Deoxyribonucleic acid): Genetic material storing instructions for protein synthesis; remains in nucleus.
Genetic information: Instructions for protein construction, stored in DNA sequence.
Gene: Portion of DNA coding for 1 protein.
Genome: Complete genetic information in a cell.
Exome: Portion of genome coding for proteins.

Double helix structure.
Building blocks: Nucleotides (deoxyribose sugar, phosphate group, nitrogenous base).
Bases: Adenine (A), Cytosine (C), Guanine (G), Thymine (T).
Complementary base pairing: A-T and C-G, held by hydrogen bonds.
DNA wraps around histone proteins to form chromosomes.

Process producing an exact copy of a DNA molecule; occurs during interphase (S phase).
Hydrogen bonds between base pairs break, strands unwind and separate.
New nucleotides pair with exposed bases, directed by DNA polymerase; enzymes connect the sugar-phosphate backbone.

Genetic Code: Triplet code (3 nucleotides) represents an amino acid or start/stop signal.
RNA (Ribonucleic acid): Single strand of nucleotides; contains ribose, phosphate, and bases (A, G, C, Uracil (U) instead of T); shorter than DNA.
Transcription: Process of copying DNA sequence onto an RNA sequence; occurs in nucleus.
- mRNA (Messenger RNA): Carries genetic code from DNA to ribosome.
- RNA Polymerase: Enzyme catalyzing mRNA formation from DNA.
Translation: Process of converting mRNA genetic code into a protein (amino acid sequence); occurs in cytoplasm on ribosomes.
- mRNA binds to ribosome; tRNA (transfer RNA) brings specific amino acids based on mRNA codons.