exam 1 patho redemption

Transport Mechanisms

• Transport Identification: Understanding transport mechanisms is crucial for cellular physiology.

  • Uniport: A single substance moves across the membrane.

  • Symport: Two substances move in the same direction.

  • Antiport: Two substances move in opposite directions.

  • Facilitated Diffusion: Movement along the concentration gradient without energy.

  • Primary Active Transport: Movement against the concentration gradient using ATP.

  • Secondary Active Transport: Movement against the gradient using energy from primary active transport.

Intracellular Anionic Proteins

• Transport Limitations: Large anionic intracellular proteins face significant barriers.

  • Size: Too large to pass through the phospholipid bilayer or transport proteins.

  • Charge: Negative charge repels them from the negatively charged inner membrane.

Second Messengers in Signal Transduction

• Key Second Messengers: Important in cellular signaling processes.

  • cAMP: Activates protein kinases, initiating cellular responses.

  • IP3: Triggers release of calcium from intracellular stores.

Equilibrium Potential Differences

• Potassium vs. Sodium: Variances in equilibrium potential.

  • Potassium: Higher concentration inside the cell leads to a more negative equilibrium potential (~ -90 mV).

  • Sodium: Higher concentration outside creates a positive equilibrium potential (~ +60 mV).

Action Potential Voltage Changes

• Phases of Action Potential:

  • Depolarization: Membrane potential moves towards zero or becomes positive due to Na+ influx.

  • Repolarization: Membrane returns to resting potential due to K+ efflux.

  • Hyperpolarization: Potential becomes more negative than resting potential.

  • Ion Channel Dynamics: Voltage-gated Na+ channels open during depolarization, then inactivate; K+ channels open during repolarization.

Magnitude of Stimulus and Graded Potential

• Graded Potential Relationship: Correlation between stimulus magnitude/duration and graded potential.

  • Greater Stimulus Strength: Results in a larger graded potential.

  • Longer Duration: Sustains a graded potential.

Transport Mechanism Analysis

• Direction of Solute Movement: Helps determine transport type.

  • Uniport Example: Glucose transport via GLUT.

  • Symport Example: Sodium-glucose co-transporter.

  • Antiport Example: Na+/K+ pump.

Carrier Competition Issues/Solutions

• Nutrient Uptake: Similar substrates can compete for carriers, leading to decreased nutrient transport.

  • Example: High levels of one amino acid inhibit transport of others.

  • Solutions: Adjust dietary intake or use supplements to restore balance.

General Mechanisms Summary

• Transport Mechanism Analysis:

  • Uniport, symport, antiport classification.

  • Importance of energy and concentration gradients.

  • Large molecules require specific transport mechanisms not available to them.

Membrane Potential and Equilibrium Potential Effects

• Factors Influencing Membrane Potential:

  • Charge distribution alters membrane potential.

  • Increased Na+ concentration outside leads to more positive membrane potential.

  • Conversely, a higher concentration of K+ inside leads to a more negative equilibrium potential.

Summary of Action Potentials

• Generate Action Potential: Summation of graded potentials can lead to threshold potential and, subsequently, action potentials.

  • Temporal/Spatial Summation: Combining signals to reach depolarization threshold.

Transport Mechanisms Overview

1. Transport Identification

• Uniport: A single substance moves across the membrane.

• Symport: Two substances move in the same direction.

• Antiport: Two substances move in opposite directions.

• Facilitated Diffusion: Movement along the concentration gradient without energy.

• Primary Active Transport: Movement against the concentration gradient using ATP.

• Secondary Active Transport: Movement against the gradient using energy from primary active transport.

2. Transport Limitations for Large Anionic Proteins

• Size: These proteins are too large to pass through the phospholipid bilayer or transport proteins.

• Charge: Their negative charge repels them from the negatively charged inner membrane, preventing effective transport.

3. Carrier Competition Issues/Solutions

• Nutrient Uptake: Similar substrates can compete for carriers, leading to decreased nutrient transport.

  • Example: High levels of one amino acid can inhibit the transport of others.

  • Solutions: Adjust dietary intake or use supplements to restore balance.

4. Key Second Messengers in Signal Transduction

• cAMP: Activates protein kinases, initiating cellular responses.

• IP3: Triggers the release of calcium from intracellular stores.

5. Equilibrium Potential Analysis

• Analyze the concentration gradients of ions to determine impact on equilibrium potential;

  • A higher concentration inside the cell results in a more negative equilibrium potential for potassium (~ -90 mV), whereas a higher concentration outside for sodium creates a positive equilibrium potential (~ +60 mV).

6. Potassium vs. Sodium Equilibrium Potential

• The equilibrium potential of potassium is higher in negativity than sodium because potassium's higher intracellular concentration leads to more negativity (~ -90 mV) compared to sodium which is more positive (~ +60 mV).

7. Membrane Potential Magnitude

• Changes in the distribution of positive and negative charges across the membrane affect the membrane potential's magnitude.

• Increased Na+ concentration outside the cell leads to a more positive membrane potential, whereas a higher concentration of K+ inside leads to a more negative equilibrium potential.

8. Action Potential Voltage Changes

• Depolarization: Membrane potential moves towards zero or becomes positive due to Na+ influx.

• Repolarization: Membrane returns to resting potential due to K+ efflux.

• Hyperpolarization: Potential becomes more negative than resting potential.

• Ion Channel Dynamics: Voltage-gated Na+ channels open during depolarization and then inactivate; K+ channels open during repolarization.

9. Graded Potentials and Action Potential Generation

• Graded potential strength can be assessed based on hypothetical scenarios; more substantial or prolonged graded potentials result in a higher likelihood of reaching action potential thresholds, especially through temporal/spatial summation.

10. Stimulus Magnitude/Durations Relationship

• A greater stimulus strength results in a larger graded potential, while a longer duration sustains that graded potential, emphasizing the direct relationship between stimulus characteristics and graded potential outcomes.