Health Sciences HSF1000: Cell Membrane Quiz

Diploma of Health Sciences - Human Structure and Function (HSF1000)

• This course covers human structure and function, specifically focusing on how the body fuels itself at a molecular level.

• Important concepts include cell membranes, transport across membranes, diffusion, osmosis, and cellular respiration.

Cell Membrane

• Boundary of Cell: Encloses and supports cell contents, separating intracellular from extracellular materials.
• Material Attachment: Connects cells to each other and the surrounding matrix.
• Cell Communication: Allows cells to communicate with their environment.
• Selective Permeability: Determines what can move into and out of the cell, controlling the intra-and extracellular environment.
• Membrane Potential: Difference in charge across the membrane (more positive ions on the outside, more positive ions inside the cell).
• Fluid Mosaic Model: Appearance of the membrane. It is flexible and not rigid or static.
• Composition: Primarily composed of lipids (phospholipids and cholesterol), proteins (integral and peripheral), and carbohydrates. (only on outer surface)
• Lipid Bilayer: A core structure—Phospholipids and cholesterol, a highly impermeable barrier to most "charged," "non-lipid soluble," and "water" soluble substances. Integral proteins act as channels, pores, or carriers to help these substances cross.

Transport Across the Membrane

• Passive Transport: Does not require cellular energy (ATP).
  • Simple Diffusion: Through the lipid bilayer, for lipid-soluble substances.
  • Channel-mediated Diffusion: Through ion channels, for water-soluble substances.
  • Carrier-mediated Diffusion: Through carrier proteins, for water-soluble substances.
• Active Transport: Requires cellular energy (ATP).
  • Ions (like sodium and potassium) moved against their concentration gradient.
• Types of Transport Proteins:
  • Channel Proteins: Form channels through the plasma membrane, specific to certain molecules
    • Leak channels: always open.
    • Gated channels: opened/closed by stimuli (ligand, voltage).
  • Carrier Proteins: Integral proteins with specific binding sites, change shape to transport molecules (uniporters—one ion/molecule, symporters—two ions/molecules in the same direction, antiporters—two ions/molecules in opposite directions).

Diffusion & Osmosis

• Diffusion: The passive movement of molecules (or ions or other solutes) down a concentration gradient (from an area of high concentration to low).
• Osmosis: The passive movement of water across a selectively permeable membrane, from an area of low solute concentration to an area of high solute concentration. It's driven by differences in solute concentration.
• Solute: Dissolved substances in a solution (ions, glucose, etcetera).
• Solvent: The liquid that dissolves the solute (water).
• Solution: The mixture of solute and solvent.

Tonicity of Solutions

• Isotonic Solution: The solution has the same concentration of dissolved solutes as inside the cell. Water moves equally in both directions, maintaining cell shape.
• Hypertonic Solution: The solution has a higher concentration of solutes than inside the cell. Water moves out of the cell, causing the cell to shrink (crenate).
• Hypotonic Solution: The solution has a lower concentration of solutes than inside the cell. Water moves into the cell, causing the cell to swell and potentially burst.

Cellular Respiration

• The process that breaks down chemical bonds in food to produce energy stored as ATP.
• 1 glucose + 6O2 → 6H2O + 6CO2 + 36-38 ATP
• Stages of Respiration:
  • Glycolysis: Occurs in cytoplasm; anaerobic (no oxygen required), breaks down glucose to pyruvate, produces 2 ATP and 2 NADH.
  • Citric Acid Cycle (Krebs Cycle): Occurs in mitochondrial matrix; aerobic (requires oxygen); converts pyruvate to Acetyl CoA generating 2 NADH, 1 ATP, and 2 CO2 per glucose.
  • Electron Transport Chain (Oxidative Phosphorylation): Occurs in inner mitochondrial membrane; aerobic; produces 32 - 34 ATP, oxygen as the final electron acceptor.
• Alternate Energy Sources:
  • Fatty acids undergo beta oxidation to form Acetyl CoA to generate more energy.
  • Amino acids can be converted into intermediate compounds for further digestion.

Additional Key Terms

• ATP: Adenosine triphosphate—stores and releases energy needed by cells, produced via cellular respiration.
• ADP: Adenosine diphosphate—a lower energy form of ATP
• NADH/FADH2: Electron carriers that shuttle high-energy electrons from glycolysis and the citric acid cycle.
• Phosphorylation: Process of adding a phosphate group to a molecule, in this case glucose, which increases its energy level and makes it more reactive.
• Concentration Gradient: Difference in concentration of a substance between two areas, this difference drives the movement of the substance.