Cell Physiology Part 4

Question 1

What mediates intercellular communication in signal transduction?

Answer 1

Chemical messengers such as hormones, neurotransmitters, and cytokines.

Question 2

What are the main pathways of cell membrane signal transduction?

Answer 2

1. G-protein-linked receptor
   
   2. Ionotropic receptor
   3. Enzyme-linked receptor

Question 3

What happens in G-protein-linked receptor signal transduction?

Answer 3

The receptor activates a G-protein, which in turn activates effector enzymes, leading to second messenger production and cellular response.

Question 4

Name some G protein effector enzymes

Answer 4

Adenylyl cyclase (AC), Phospholipase C (PLC), Guanylyl cyclase (GC), Phosphodiesterase (PDE)

Question 5

Name some common second messengers.

Answer 5

cAMP, IP3, DAG, cGMP, Ca²⁺

Question 6

What are two key G-protein pathways?

Answer 6

• Receptor-G protein-AC
• Receptor-G protein-PLC

Question 7

How do ionotropic receptors work?

Answer 7

They act as ion channels that open/close in response to specific signals (voltage, ligands, or intracellular messengers).

Question 8

What are the types of ionotropic channels based on their activation?

Answer 8

• Voltage-gated
• Ligand-gated (extracellular signal)
• Signal-gated (intracellular

Question 9

What is special about enzyme-linked receptors?

Answer 9

They have intrinsic enzyme activity and directly trigger enzyme signaling pathways.

Question 10

Name types of enzyme-linked receptors.

Answer 10

• Tyrosine kinase receptor
• Guanylyl cyclase receptor
• Serine/threonine kinase receptor
• Non-receptor protein tyrosine kinase

Question 11

Name five important ligands involved in cell signaling.

Answer 11

• Insulin
• Vascular Endothelial Growth Factor (VEGF)
• Platelet-Derived Growth Factor (PDGF)
• Epidermal Growth Factor (EGF)
• Macrophage Colony-Stimulating Factor (M-CSF)

Question 12

What types of cells generate rapidly changing electrical impulses?

Answer 12

Nerve and muscle cells

Question 13

What are local potential changes used for?

Answer 13

To transmit signals and control the function of cells

Question 14

Do all cells have an electrical potential difference across their membrane?

Answer 14

Yes, all cells exhibit a membrane potential.

Question 15

How is the membrane potential of a nerve fiber measured?

Answer 15

Using a microelectrode inserted into the nerve fiber

Question 16

What are the origins of the resting membrane potential?

Answer 16

•Unequal concentrations of Na⁺, K⁺, and Cl⁻ between extracellular and intracellular fluids
• different membrane permeabilities, with higher permeability to K⁺ than Na+at resting condition.

Question 17

What are the two components of the electrochemical driving force?

Answer 17

Concentration difference and electrical potential difference

Question 18

In electrochemical gradients, how do the concentration and electrical driving forces relate directionally?

Answer 18

They act in opposite directions

Question 19

When is the electrochemical driving force equal to zero?

Answer 19

When the chemical and electrical driving forces are equal and opposite — this is the equilibrium potential (Eₖ)

Question 20

What is the Nernst equation for calculating the equilibrium potential of potassium (K⁺)?

Answer 20

Eₖ = (RT / zF) × ln([K⁺]₀ / [K⁺]ᵢ)

Question 21

What does a larger concentration gradient result in for an ion’s equilibrium potential?

Answer 21

A larger equilibrium potential

Question 22

What determines how much an ion contributes to the resting membrane potential?

Answer 22

Its membrane permeability — the more permeable, the more influence

Question 23

Which types of cells are considered excitable and can generate action potentials?

Answer 23

Nerve, muscle, endocrine, immune, and reproductive cells

Question 24

What is polarization in terms of membrane potential?

Answer 24

The resting state of the membrane, typically around -70 mV

Question 25

What is depolarization?

Answer 25

A decrease in membrane potential (inside becomes less negative, often due to Na⁺ influx) than the resting level .

Question 26

What is repolarization?

Answer 26

Return of the membrane potential to resting state (mainly due to K⁺ efflux) after depolarization

Question 27

What is hyperpolarization?

Answer 27

Membrane potential becomes more negative than the resting potential

Question 28

What is an action potential?

Answer 28

rapid; large alterations in the membrane potential that spread rapidly along the nerve membrane

Question 29

What is a threshold potential?

Answer 29

membrane potential at which an action potential is initiated

Question 30

What is the absolute refractory period?

Answer 30

The excitability of cells undergoes a series of alteration after an action potential initiates. During the action potential a second stimulus ,no matter how strong will not produce a second action potential and the membrane is said to be in its absolute refractory period.

Question 31

What is the relative refractory period?

Answer 31

The interval during which a second action potential can be produced but only if the stimulus strength is considerably greater than usual .

Question 32

Describe resting membrane potential?

Answer 32

All cells under resting conditions have a potential difference across their plasma membranes with the inside of the cell negatively charged with respect to the outside

Question 33

List the important factors in the establishment of the normal resting potential

Answer 33

Selective Permeability of the Membrane Sodium-Potassium Pump (Na⁺/K⁺ ATPase) Concentration Gradients of Ions Negatively Charged IntracellularProteins Equilibrium Potential of Potassium (K⁺)

Question 34

Explain the all or none principle

Answer 34

Once a stimulus reaches the threshold level (usually around –55 mV in neurons), a full action potential is triggered. If the stimulus is below the threshold, no action potential occurs. The size or strength of the action potential does not change with the strength of the stimulus — it is either all (full response) or none (no response).