Biology Lecture Notes: Cellular Transport and Metabolism

Sugars: Key role in energy storage and structure.
Fatty Acids: Composed of long hydrocarbon chains, essential for energy storage and membrane structure.

Primary Structure: Linear chain of amino acids in a protein.
Secondary Structure: Hydrogen bonds form alpha helices and beta sheets.
Tertiary Structure: Three-dimensional folding of a protein.
Quaternary Structure: Assembly of multiple polypeptide chains into a functional protein.

Phospholipids: Form the fundamental bilayer of cell membranes with hydrophilic heads and hydrophobic tails.
- Key functional roles in membrane fluidity and permeability.
Proteins: Integral and peripheral proteins serve diverse functions in cellular processes.
- Integral Proteins: Span the membrane, involved in transport and communication.
- Peripheral Proteins: Loosely attached to the membrane, serve roles in signaling and maintaining the cell’s shape.
Cholesterol: Modulates membrane fluidity and stability in animal cell membranes.

Diffusion: Movement of molecules from high concentration to low concentration.
- Facilitated Diffusion: Movement of molecules across membranes via specific transport proteins.
- Stages in Transport: 5 stages identified in detailed processes of molecular movement across membranes.
Active Transport: Movement against the concentration gradient, requiring energy (ATP).

Glycolysis: Anaerobic process of converting glucose into pyruvate, yielding energy in the form of ATP.
- Involves multiple stages and produces reduced cofactors (e.g., NADH) and ATP.
Fermentation: Anaerobic process utilizing glycolysis products in energy production.
Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondria, oxidizes acetyl-CoA to produce energy carriers (NADH, FADH₂) and CO₂.
- Chemical reactions include the conversion of acetyl-CoA into citric acid.
Electron Transport Chain: Series of protein complexes that transfer electrons and pump protons to create a gradient for ATP synthesis.
- Molecular formula: O₂ + 4 e− → 2 H₂O in the final electron transfer reaction.

Osmolarity: Measure of solute concentration in a solution.
- Hypertonic: Higher solute concentration outside the cell causing the cell to lose water.
- Isotonic: Equal solute concentrations inside and outside the cell, leading to no net water movement.
- Hypotonic: Lower solute concentration outside the cell, causing the cell to swell as water enters.

The interconnected pathways of glycolysis, citric acid cycle and oxidative phosphorylation demonstrate the coupling of energy production and usage in biological systems.