TEST 1!!

Cellular Biochemistry & Metabolism

• Autotrophs: Self-feeders (plants); create food from inorganic material via photosynthesis ($CO<em>2 + H</em>2O \rightarrow C<em>6H</em>{12}O<em>6 + O</em>2$).

• Heterotrophs: Other-feeders (animals); obtain food by consuming other organisms.

• Metabolism: Sum of chemical processes in a cell.

  • Catabolism: Breaking down larger molecules into smaller ones, releases energy.

  • Anabolism: Building larger molecules from smaller ones, requires energy.

• Cells act as a factory, producing energy via catabolism and products via anabolism.

• Hydrolysis: First step in nutrient processing, often outside the cell (gut).

• Cytoplasm: Site of initial catabolic processing, anaerobic respiration (produces Acetyl-CoA).

• Mitochondria: Site of aerobic respiration, produces ATP.

• ATP (Adenosine Triphosphate): Primary energy currency of the cell, energy liberated from covalent bonds (e.g., in glucose).

• Anaerobic: Metabolic reactions not requiring oxygen.

• Aerobic: Metabolic reactions requiring oxygen.

• Enzymes: Biological catalysts (metabolic bosses), control reactions, highly specific, named for their substrate with "-ase" suffix (e.g., lactase), accelerate reactions.

• Substrate: Molecule an enzyme acts upon; binds to the enzyme's active site.

Carbohydrate Metabolism

• Sources: Diet, stored glycogen (liver).

• Forms: Monosaccharides (glucose), Disaccharides (sucrose), Polysaccharides (cellulose).

• Glucose: Primary carbohydrate, used by all cells, essential for RBCs/brain.

• Glycolysis (Anaerobic Respiration): First stage of glucose catabolism in cytoplasm.

  • Glucose converted to pyruvate.

  • Net gain of $2$ ATP molecules.

• Pyruvate Fates:

  • Oxygen-poor environment: Converted to lactic acid (low energy yield).

  • Oxygen-rich environment: Enters mitochondria for aerobic respiration.

• Aerobic Respiration:

  • Pyruvate converted to Acetyl-CoA, enters Krebs Cycle.

  • Electron Transport System produces water and $CO_2$.

  • Generates $36$ ATP; total $38$ ATP per glucose molecule (counting glycolysis).

• Gluconeogenesis: Glucose generation from non-carbohydrates.

• Glycogenesis: Glucose stored as glycogen.

• Glycogenolysis: Glycogen converted back to glucose.

Lipid Metabolism

• Functions: Energy source/storage, hormones, protection, temperature regulation.

• Types: Neutral fats (triglycerides), Phospholipids (cell membranes), Steroids (hormones).

• Site: Primarily the liver (lipolysis).

• Triglycerides: Broken down into glycerol and fatty acids.

  • Glycerol can make glucose or enter Krebs cycle.

  • Fatty acids converted to Acetyl-CoA (enters Krebs cycle) or ketone bodies.

• Energy Yield: Very high (e.g., up to $148$ ATP from one fatty acid chain).

• Essential Fatty Acids: Cannot be synthesized by the body, must be acquired through diet.

Protein Metabolism

• Abundance: Most abundant organic molecule in the body (keratin, collagen, enzymes, etc.).

• Building Blocks: Amino acids linked by peptide bonds form peptide chains.

• Sources: Primarily recycling of tissue proteins; dietary sources provide a small percentage.

• Protein Digestion: Proteases and peptidases break dietary proteins into amino acids.

• Protein Catabolism:

  • Amino acids processed in mitochondria to produce ATP.

  • Toxic ammonia ($NH_3$) byproduct is converted to non-toxic urea in the liver.

• Protein Anabolism (Synthesis):

  • Process of acquiring coded instructions from DNA to create a unique sequence of amino acids.

  • Determines cell function.

• Essential Amino Acids: Cannot be synthesized, must be in the diet (e.g., taurine for cats).

Protein Synthesis

• Crucial cellular activity, most cellular machinery dedicated to it.

• DNA (Deoxyribonucleic Acid): Double-stranded, found in nucleus, deoxyribose sugar, bases A, T, G, C.

• RNA (Ribonucleic Acid): Single-stranded, made in nucleus and migrates to cytoplasm, ribose sugar, bases A, U, G, C.

• Nucleotide: Repeating unit of nucleic acid (nitrogenous base, sugar, phosphate group).

• Triplet: $3$ DNA bases in a row.

• Codon: $3$ complementary RNA bases in a row (corresponds to a specific amino acid).

• Transcription: DNA information copied to mRNA in the nucleus.

• Translation: mRNA instructions decoded into a protein (sequence of amino acids) in the cytoplasm.

• RNA Polymerase: Enzyme that aids in transcription.

• Types of RNA: mRNA (messenger), tRNA (transfer), rRNA (ribosomal).

• Peptide Bonds: Link amino acids together to form proteins.

• Errors: Misplaced codons can lead to serious consequences (e.g., Sickle Cell disease).

Cellular Division

• Purpose: Replaces damaged/worn cells, increases cell number, organism reproduction.

• **Types:

  • Meiosis: Reproductive cells (egg/sperm).

  • Mitosis: Somatic (body) cells.

• DNA Replication: DNA reproduces itself before division to pass genetic material to new cells.

• **Somatic Cell Division Components:

  • Mitosis: Division of the nucleus.

  • Cytokinesis: Division of the cytoplasm and organelles.

• Cell Cycle: Sequence of changes a cell goes through.

  • Interphase: Cell replicates its DNA, prepares for division, not actively dividing.

  • Mitotic Phase: Active cell division (Mitosis + Cytokinesis).

• Stages of Mitosis:

  • Prophase: Chromatin condenses into chromosomes (two sister chromatids), nuclear envelope disintegrates, mitotic spindle forms.

  • Metaphase: Chromosomes align at the metaphase plate (equator).

  • Anaphase: Sister chromatids separate and move to opposite poles, becoming individual chromosomes; cell elongates.

  • Telophase: Chromosomes decondense, nuclear parts reassemble, spindle disassembles, cytoplasm divides (cytokinesis).

• Cell Differentiation: Identical cells become specialized; involves selective activation/inhibition of genes to dictate cell shape and function.