KA 3

Question 1

What is the fluid mosaic model of cell membranes?

Answer 1

The fluid mosaic model is a widely accepted model of the plasma cell membrane structure, which describes the membrane as a fluid lipid bilayer embedded with a mosaic of components including phospholipids, cholesterol, proteins and carbohydrates that can move laterally within the membrane giving it the fluid structure.

Question 2

What do regions of hydrophobic R groups allow?

Answer 2

Strong hydrophobic interactions that hold integral membrane proteins within the phospholipid bilayer Integral membrane proteins interact extensively with the hydrophobic region of membrane phospholipids.

Question 3

Some integral membrane proteins are…

Answer 3

Transmembrane proteins

Question 4

Peripheral membrane proteins have what on their surface? What are these bound to?

Answer 4

Hydrophilic R groups on their surface and are bound to the surface of membranes, mainly by ionic and hydrogen bond interactions

Question 5

Many peripheral membrane proteins interact with what?

Answer 5

The surfaces of integral membrane proteins

Question 6

What is the phospholipid bilayer a barrier to?

Answer 6

A barrier to ions and most uncharged polar molecules

Question 7

Small molecules, such as oxygen and carbon dioxide pass through? By?

Answer 7

Pass through the phospholipid bilayer, by simple diffusion

Question 8

Facilitated diffusion is?

Answer 8

The passive transport of substances across the membrane through specific transmembrane proteins

Question 9

To perform specialised functions, different cell types have?

Answer 9

Different channel and transporter proteins

Question 10

Most channel proteins in animal and plant cells are?

Answer 10

Highly selective

Question 11

What are channels?

Answer 11

Multi-subunit proteins with the subunits arranged to form water-filled pores that extend across the membrane.

Question 12

Some channel proteins are?

Answer 12

Gated and changed conformation to allow or prevent diffusion.

Question 13

Ligand-gated channels are controlled by?

Answer 13

The binding of signal molecules

Question 14

Voltage gated channels are controlled by?

Answer 14

Controlled by changes in ion concentration

Question 15

Controlled by changes in ion concentration

Answer 15

The specific substance to be transported and undergo a conformational change to transfer the solute across the membrane

Question 16

Transporters alternate between two? So what can happen?

Answer 16

Conformations so that the binding site for a solute is sequentially exposed on one side of the bilayer, then the other.

Question 17

Active transport uses pump proteins which?

Answer 17

Transfer substances across the membrane against their concentration gradient

Question 18

Pumps that mediate active transport are what?

Answer 18

Transporter proteins coupled to an energy source

Question 19

A source of metabolic energy is required for?

Answer 19

Active transport

Question 20

Some active transport proteins hydrolyse what? To provide energy for?

Answer 20

ATP directly to provide the energy for the conformational change required to move substances across the membrane ATPases hydrolyse ATP.

Question 21

For a solute carrying a net charge, what combine? to form what? Which determines…

Answer 21

The concentration gradient and the electrical potential difference combine to form the electrochemical gradient that determines the transport of the solute

Question 22

When is a membrane potential created?

Answer 22

(an electrical potential difference) is created when there is a difference in electrical charge on the two sides of the membrane.

Question 23

Ion pumps, such as the sodium-potassium pump, use energy from?

Answer 23

The hydrolysis of ATP to establish and maintain ion gradients

Question 24

The sodium-potassium pump transports ions against?

Answer 24

A steep concentration gradient using energy directly from ATP hydrolysis

Question 25

The sodium-potassium pump actively transports what in and out of the cell?

Answer 25

Sodium ions out of the cell and potassium ions into the cell

Question 26

Describe the action of the sodium potassium pump? (12 points)

Answer 26

Pump has high affinity for sodium ions inside the cell; binding occurs; phosphorylation by ATP; conformation changes; affinity for sodium ions decreases; sodium ions released outside of the cell; potassium ions bind outside the cell; dephosphorylation; conformation changes; potassium ions taken into cell; affinity returns to start; For each ATP hydrolysed, three sodium ions are transported out of the cell and two potassium ions are transported into the cell.

Question 27

What does the sodium potassium pump establish?

Answer 27

This establishes both concentration gradients and an electrical gradient.

Question 28

Where is the sodium-potassium pump found? What does this account for?

Answer 28

In most animal cells, accounting for a high proportion of the basal metabolic rate in many organisms

Question 29

In the small intestine, what is the sodium gradient created by?

Answer 29

The sodium-potassium pump which drives the active transport of glucose

Question 30

What does the sodium potassium pump generate in intestinal epithelial cells? Across what?

Answer 30

The sodium potassium pump generates a sodium ion gradient across the plasma membrane.

Question 31

The glucose transporter responsible for this glucose symport transports? What does this do?

Answer 31

Sodium ions and Sodium ions into the cell down their concentration gradient; the simultaneous glucose at the same time and in the same direction transport of glucose pumps glucose into the cell against its concentration gradient.