Membrane proteins

Question 1

What is a fluid mosaic model?

Answer 1

A model that describes the structure of the cell membrane.

Question 2

What holds integral membrane proteins with the phospholipid bilayer?

Answer 2

Regions of hydrophobic R groups allow strong hydrophobic interactions that hold integral membrane proteins in the phospholipid bilayer.

Question 3

What are transmembrane proteins?

Answer 3

The protein spans the entirety of the cell membrane.

Question 4

What do peripheral membrane proteins have?

Answer 4

Peripheral membrane proteins have hydrophilic R groups on their surface and are bound to the surface of membranes, mainly ionic and hydrogen bonding interactions.

Question 5

Do peripheral membrane proteins interact with integral membrane proteins?

Answer 5

Many peripheral proteins interact with the layers of the surfaces of integral membrane proteins.

Question 6

What is the phospholipid bilayer?

Answer 6

The phospholipid bilayer is a barrier to ions and most uncharged polar molecules.

Question 7

What can go through the phospholipid bilayer?

Answer 7

Some small molecules such as water and oxygen and carbon dioxide can pass through the bilayer by simple diffusion.

Question 8

What is facilitated diffusion?

Answer 8

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

Question 9

Why do different cell types have different channel and transporter proteins?

Answer 9

To perform specialised functions, different cell types have different channel and transporter proteins.

Question 10

Are channel proteins highly selective?

Answer 10

Channel proteins in animal and plant cells are highly selective. This means they let very few types of molecules pass through.

Question 11

How do channel proteins affect diffusion?

Answer 11

Some channel proteins are gated and change conformation to allow or prevent diffusion.

Question 12

How are ligand-gated channels controlled?

Answer 12

Ligand channels are controlled by the binding of signal molecules.

Question 13

How are voltage-gated channels controlled?

Answer 13

Voltage-gated channels are controlled by changes in ion concentration.

Question 14

How do transporter proteins transfer solute across membranes?

Answer 14

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

Question 15

What does active transport use to transfer substances across the membrane?

Answer 15

Active transport uses pump proteins that transfer substances across the membrane against their concentration gradient.

Question 16

What is required for active transport?

Answer 16

A source of metabolic energy.

Question 17

Why do some active transport proteins hydrolyse ATP?

Answer 17

Some active transport proteins hydrolyse ATP directly to provide the energy for the conformational change required to move substances across the membrane.

Question 18

What is the ATP that is hydrolysed by enzymes called?

Answer 18

ATP that is hydrolysed by enzymes is called ATPases.

Question 19

What determines the transport of the solute when a solute is carrying a net charge?

Answer 19

For a solute carrying a net charge, the concentration gradient and the electrical potential difference combine to form the electrochemical gradient that determines the transport of the solute.

Question 20

What do ion pumps use to establish and maintain ion gradients?

Answer 20

Ion pumps such as the sodium-potassium pump, use energy from the hydrolysis of ATP to establishing maintain ion gradients.

Question 21

Does the sodium-potassium pump go with or against the concentration gradient?

Answer 21

The sodium-potassium pump transports ions against a steep concentration gradient using energy directly from ATP hydrolyisis.

Question 22

What does the sodium-potassium pump do?

Answer 22

It actively transports sodium ions out of the cell and potassium into the cell.

Question 23

How does the sodium-potassium pump work?

Answer 23

The pump has a high affinity for sodium ions inside the cell.
Binding occurs and the pump is phosphorylated by ATP.
The conformation changes and the affinity for sodium ions decreases. This means the sodium ions are released outside the cell.
Potassium ions bind outside the cell.
Dephosphorylation occurs and the conformation of the protein changes.
Potassium ions are taken into the cell and the affinity returns to the start.

Question 24

Why do many organisms have a high proportion of the basal metabolic rate in many organisms?

Answer 24

The sodium-potassium pump is found in most aniimal cells, accounting for a high proportion of the basal metabolic rate in many organisms.

Question 25

What drives the transport of glucose in the small intestine?

Answer 25

The sodium gradient created by the sodium potassium pump drives the active transport of glucose

Question 26

What is the glucose transporter responsible for?

Answer 26

The glucose transporter is responsible for this glucose symport transports sodium ions and glucose and the same time and in the same direction.