Cell and Molecular Biology Lecture Notes Review

Cells

• All organisms are made of cells, either single or trillions.
• Cells are responsible for structure and function.
• Cell Theory:
  • All living things are composed of one or more cells.
  • Cells are the basic structural and functional units of living things.
  • All cells come from pre-existing cells.
• Two types of cells: Animal and Plant.

Comparison of Plant and Animal Cells

• Plant cells are rectangular, have large/few vacuoles, chloroplasts, cell walls, and plastids.
• Animal cells are spherical, have small/many vacuoles, and lack chloroplasts, cell walls, and plastids.

Organelles and Their Functions

• Mitochondrion: Powerhouse of the cell, ATP production occurs here. The inner membrane is folded into projections called CRISTAE.
• Centrioles: Organize microtubules during mitosis and form bases of cilia and flagella.
• Vacuole: Storage of cell materials, especially water.
• Cytoplasm: Jelly-like fluid holding organelles in place.
• Nucleolus: Site of ribosome production.
• Nuclear Membrane: Protects the nucleus and controls the passage of materials.
• Nucleus: Controls all cell activities.
• Rough Endoplasmic Reticulum (RER): Transports materials throughout the cell; contains ribosomes.
• Golgi Body: Packages, modifies, and separates proteins for release.
• Microtubules: Support the cell and give it shape; form centrioles.
• Ribosomes: Sites of protein synthesis.
• Smooth Endoplasmic Reticulum (SER): Lipid and steroid production and lipid metabolism.
• Cell Membrane: Controls passage of materials into and out of the cell. Consists of a double phospholipid layer.

Cell Fractionation and Ultracentrifugation

• Cell fractionation: cells are placed in a cold, isotonic, buffered solution to:
  • reduce enzyme activity, prevent bursting, maintain pH.
• Ultracentrifugation: Separating fragments in filtered liquid using a centrifuge to create centrifugal force to isolate organelles.

Biological Molecules

• Four major classes: Carbohydrates, Lipids, Proteins, and Nucleic Acids.
• Polymers (except lipids) are built from monomers through covalent bonds.
• Monomers are linked by dehydration synthesis and they are split by hydrolysis.
• Lipids are "composite molecules."

Carbohydrates

• Comprised of carbon, hydrogen, and oxygen with the general formula Cx(H2O)_y.
• Functions: Energy metabolism and storage, structural material.
• Four major types:
  • Monosaccharides (one unit)
  • Disaccharides (two units connected by dehydration synthesis)
  • Oligosaccharides (3-10 units)
  • Polysaccharides (more than 10 units, energy storage and structural).
• Important Polysaccharides:
  • Starch (plant storage).
    • Amylose: unbranched glucose chain.
    • Amylopectin: branched glucose chains.
  • Glycogen (animal storage, branched glucose chains).
  • Cellulose (plant structural, unbranched).
  • Chitin (animal structural).

Lipids

• Insoluble in water, soluble in organic solvents. Excellent energy storage.
• Three major groups: Fats/Oils, Phospholipids, Steroids.
• Fats and Oils: Triglycerides formed from glycerol and 3 fatty acids.
  • Saturated: all single bonds.
  • Monounsaturated: one double bond.
  • Polyunsaturated: two or more double bonds.
• Phospholipids: Similar to fats but with a phosphate group instead of one fatty acid.
• Steroids: 4-ring carbon core.

Proteins

• Macromolecules containing carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur.
• Used for building structures and in chemical activities.
• Made of amino acids linked by peptide bonds (formed by dehydration synthesis).
• Amino Acid Structure:
  • Amino group (NH_2)
  • Carboxyl group (COOH)
  • Hydrogen atom (H)
  • R group (side chain; 20 different R groups).
• Protein Structure Levels:
  1. Primary
  2. Secondary
  3. Tertiary
  4. Quaternary

Enzymes

• Proteins that act as catalysts in biological systems.
• Lower activation energy.
• Enzyme Specificity is where enzyme only acts on specific substrate.
• Lock and Key Model vs. Induced-fit Model: Active site is flexible.
• Factors Affecting Enzyme Activity:
  • Temperature (optimal temperature 37oC).
  • pH (optimal pH).
  • Substrate Concentration.
  • Enzyme Concentration.
• Enzyme Inhibitors:
  • Non-Specific: Denature all enzymes.
  • Specific:
    • Competitive: Compete for active site.
    • Noncompetitive: Bind to allosteric site.

Nucleic Acids

• Store and transfer genetic information and control protein production.
• Polymers of nucleotides.
• Nucleotide Structure:
  • Pentose Sugar (Ribose or Deoxyribose)
  • Phosphate Group (PO_4)
  • Nitrogenous Base (Purine or Pyrimidine).
• Purines: Adenine, Guanine (2 rings).
• Pyrimidines: Uracil, Cytosine, Thymine (1 ring).
• Two Important Nucleic Acids:
  • DNA (Deoxyribonucleic Acid).
  • RNA (Ribonucleic Acid).
• DNA Structure:
  • Double helix.
  • Sugar-phosphate backbone.
  • Nitrogenous base pairing:
    • A bonds with T.
    • G bonds with C.

DNA vs RNA

Energy

• Defined as the ability to do work.
• Forms: heat, light, chemical, electrical.
• Two General Classifications:
  • Kinetic: energy of motion.
  • Potential: energy of position.
• Laws of Thermodynamics:
  • First Law: Energy can be converted but not created or destroyed.
  • Second Law: Systems tend towards disorder (entropy).
• Exothermic Reaction: Releases energy.
• Endothermic Reaction: Absorbs energy.
• Metabolism: Sum of all chemical reactions.
• Anabolic Reactions: Build larger molecules.
• Catabolic Reactions: Break down larger molecules.

Cellular Respiration

• Converts chemical energy stored in food (glucose) into ATP.
• Equation: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + ENERGY.
• Two Phases:
  • Anaerobic: Glycolysis (cytosol)
  • Aerobic: Krebs Cycle and Electron Transport Chain (mitochondrion).
• Glycolysis:
  • Glucose splits into two pyruvate molecules.
  • Net gain: 2 ATP, 2 NADH.
• Alcoholic Fermentation: Converts pyruvate to acetaldehyde, then to ethanol to regenerate NAD^+.
• Oxidative Decarboxylation: Pyruvate converted to Acetyl CoA.
• Krebs Cycle (Citric Acid Cycle):
  • Occurs in mitochondrial matrix.
  • Net gain per glucose molecule: 6 NADH, 2 ATP, 2 FADH_2.
• Electron Transport Chain (Oxidative Phosphorylation):
  • Occurs on cristae (inner) membrane of mitochondrion.
  • Involves complexes and electron carriers.
  • Chemiosmosis: H^+ gradient drives ATP synthesis.
  • ATP Synthase pump, 2H^+ activates enzyme (called ATPase) on the matrix side which catalyzes ADP to join with a P to form ATP!
  • Net production of 36 ATP molecules.
    *Each NADH produces approximately 3 ATP. \Each FADH_2 produces approximately 2 ATP.
• Lactic Acid Fermentation: Occurs during strenuous exercise due to lack of oxygen. Pyruvate + NADH ➔ NAD^+\