biology - 1.3

Question 1

What hold integral membrane proteins within the phospholipid bilayer?

Answer 1

Regions of hydrophobic R groups allow strong hydrophobic interactions.

Question 2

What do integral membrane proteins interact extensively with?

Answer 2

The hydrophobic region of
membrane phospholipids.

Question 3

What are some integral proteins?

Answer 3

Transmembrane proteins.

Question 4

What do peripheral membrane proteins have?

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

What do many peripheral membrane proteins interact with?

Answer 5

The surfaces of integral membrane .

Question 6

What is the phospholipid bilayer?

Answer 6

A barrier to ions and most uncharged polar molecules.

Question 7

What pass through the bilayer by simple diffusion?

Answer 7

Some small molecules, such as oxygen and carbon dioxide.

Question 8

What is facilitated diffusion?

Answer 8

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

Question 9

To perform specialised functions, what do different cell types have?

Answer 9

Different channel and transporter proteins.

Question 10

What are most channel proteins in animal and plant cells?

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

What are some channel proteins?

Answer 12

Gated and change conformation to allow or prevent diffusion.

Question 13

What are ligand-gated channels controlled by?

Answer 13

The binding of signal molecules.

Question 14

What are voltage-gated channels controlled by?

Answer 14

Changes in ion concentration.

Question 15

What do transporter proteins do?

Answer 15

They bind to the specific
substance to be transported and undergo a conformational change to transfer the solute
across the membrane.

Question 16

Why do transporters alternate between two conformations?

Answer 16

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

Question 16

What does active transport use?

Answer 16

Pump proteins that transfer substances across the membrane against their concentration gradient.

Question 17

What are pumps that mediate active transport?

Answer 17

Transporter proteins coupled to an energy source.

Question 18

What is required for active transport?

Answer 18

A source of metabolic energy.

Question 19

What do some active transport proteins hydrolyse?

Answer 19

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

Question 20

What hydrolyse ATP?

Answer 20

ATPases.

Question 21

For a solute carrying a net charge, what do the concentration gradient and the electrical potential gradient do?

Answer 21

They combine to form the electrochemical gradient that determines the transport of the solute.

Question 22

When is a membrane potential, or an electrical potential difference, created?

Answer 22

When there is a difference in electrical charge on the two sides of the membrane.

Question 23

What do ion pumps, such as the sodium-potassium pump, use?

Answer 23

Energy from the hydrolysis of ATP to establish and maintain ion gradients.

Question 24

How does the sodium-potassium pump transport ions across a steep concentration gradient?

Answer 24

Using energy directly from ATP hydrolysis.

Question 25

What does the sodium-potassium pump actively transport?

Answer 25

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

Question 26

For each ATP hydrolysed, what is transported?

Answer 26

Three sodium ions are transported out of the cell and two potassium ions are transported into the cell.

Question 27

In the sodium-potassium pump, what does the transport of ions establish?

Answer 27

Both concentration gradients and an electrical gradient.

Question 28

Sodium-potassium pump: Step 1

Answer 28

The pump has high affinity for sodium ions inside the cell; binding occurs;

Question 29

Sodium-potassium pump: Step 2

Answer 29

Phosphorylation by ATP; conformation changes;

Question 30

Sodium-potassium pump: Step 3

Answer 30

Affinity for sodium ions decreases; sodium ions released outside of the cell;

Question 31

Sodium-potassium pump: Step 4

Answer 31

Potassium ions bind outside the cell;

Question 32

Sodium-potassium pump: Step 5

Answer 32

Dephosphorylation; conformation changes;

Question 33

Sodium-potassium pump: Step 6

Answer 33

Potassium ions taken into cell; affinity returns to the start.

Question 34

Where is the sodium-potassium pump found?

Answer 34

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

Question 35

In the small intestine, what does the sodium gradient created by the sodium-potassium pump drive?

Answer 35

The active transport of glucose.

Question 36

In intestinal epithelial cells, what does the sodium-potassium pump generate?

Answer 36

A sodium ion gradient across the plasma membrane.

Question 37

What does the glucose transporter responsible for this glucose support transport?

Answer 37

Sodium ions and glucose at the same time and in the same direction.

Question 38

How do sodium ions and glucose enter the cell?

Answer 38

Sodium ions enter the cell down their concentration gradient; the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient.