Ion Channels and Cellular homeostasis

Question 1

what is the fluid mosaic model ?

Answer 1

• embedded proteins in phospholipid bilayer can float lipids

Question 2

what do structural proteins do in the plasma membrane ?

Answer 2

• Provide support and shape to the cell

Question 3

what is the role of receptor proteins in cell membranes?

Answer 3

• facilitate communication with external signals (e.g., hormones, neurotransmitters).

Question 4

what do channel proteins allow to pass through the cell membrane?

Answer 4

• allow passive flow of water, ions, and small molecules.

Question 5

what are glycoproteins, and what is their function?

Answer 5

• proteins with carbohydrate chains that aid in cell signalling and adhesion.

Question 6

how do hydrophobic substances move across the plasma membrane?

Answer 6

• they passively diffuse through the phospholipid bilayer.

Question 7

what do hydrophilic substances require for transport across the membrane?

Answer 7

• carrier proteins

Question 8

what substances can and cannot pass through membrane ?

Answer 8

• can = lipid soluble
• cannot = water soluble eg. glucose

Question 9

how does water diffuse through the plasma membrane?

Answer 9

• water diffuses easily via aquaporins, which are specialized proteins forming always-open pores.

Question 10

what is passive diffusion?

Answer 10

• the movement of molecules from high to low concentration without energy.

Question 11

what is active transport?

Answer 11

• the movement of molecules from low to high concentration using energy (ATP) through protein carriers.

Question 12

what is a hypertonic solution + what happens to cells ?

Answer 12

• has low water conc (high sugar conc) so water moves out of cell
• causes shell to shrink

Question 13

what is a hypotonic solution + what happens to cells ?

Answer 13

• has high water conc so water moves into cell
• causes cell to swell

Question 14

what is an isotonic solution + what happens to cells ?

Answer 14

• equal solute concentration to inside cells
• no net movement of water
• cell shape is normal / sam e

Question 15

How does the Na-K pump work ?

Answer 15

• uses ATP to actively pump 2 K+ in and 3Na + out of the cell

Question 16

What is the electrochemical driving force of Na⁺?

Answer 16

• chemical = higher conc of Na+ outside cell so wants to move in
• electrical = inside of the cell is slightly negative compared to the outside, attracting positively charged Na⁺ ions
• strong ECF provides source of potential energy

Question 17

Why does Na+ not move into cells if there is a large electrochemical driving force ?

Answer 17

• plasma membrane has low permeability to Na+

Question 18

What is secondary active transport?

Answer 18

• Na+ coupled simport allows cells to take up glucose
• Na+ and glucose move into cell
• uses energy from ECG

Question 19

what is facilitated diffusion?

Answer 19

• molecules move down conc gradient with channel /carrier protein

Question 20

what is electrochemical driving force on K+ ?

Answer 20

• high conc of K+ inside cell so wants to move to outside
• electrical force = K+ positive so still wants to move in since inside is slightly negative
• opposite forces

Question 21

What does the Ca2+ pump do?

Answer 21

• actively pumps Ca2+ out of the cell, maintaining a steep gradient
• using ATP

Question 22

What do ionotropic receptors do?

Answer 22

• allow Na+ and Ca2+ to flow into cells, evoking cellular responses.

Question 23

what is the direction of Ca2+ driving force ?

Answer 23

• inwardly directed
• higher conc outside so wants to enter cell