Membrane proteins

Question 2

What is a fluid mosaic model

Answer 2

A model that describes the structure of the cell membrane.

Question 3

What holds integral membrane proteins with the phospholipid bilayer

Answer 3

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

Question 4

What are transmembrane proteins

Answer 4

The protein spans the entirety of the cell membrane.

Question 5

What do peripheral membrane proteins have

Answer 5

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 6

Do peripheral membrane proteins interact with integral membrane proteins

Answer 6

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

Question 7

What is the phospholipid bilayer

Answer 7

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

Question 8

What can go through the phospholipid bilayer

Answer 8

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

Question 9

What is facilitated diffusion

Answer 9

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

Question 10

Why do different cell types have different channel and transporter proteins

Answer 10

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

Question 11

Are channel proteins highly selective

Answer 11

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

Question 12

How do channel proteins affect diffusion

Answer 12

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

Question 13

How are ligand-gated channels controlled

Answer 13

Ligand channels are controlled by the binding of signal molecules.

Question 14

How are voltage-gated channels controlled

Answer 14

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

Question 15

How do transporter proteins transfer solute across membranes

Answer 15

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

Question 16

What does active transport use to transfer substances across the membrane

Answer 16

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

Question 17

What is required for active transport

Answer 17

A source of metabolic energy.

Question 18

Why do some active transport proteins hydrolyse ATP

Answer 18

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

Question 19

What is the ATP that is hydrolysed by enzymes called

Answer 19

ATP that is hydrolysed by enzymes is called ATPases.

Question 20

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

Answer 20

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 21

What do ion pumps use to establish and maintain ion gradients

Answer 21

Ion pumps such as the sodium-potassium pump, use energy from the hydrolysis of ATP to establish maintenance gradients.

Question 22

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

Answer 22

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

Question 23

What does the sodium-potassium pump do

Answer 23

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

Question 24

How does the sodium-potassium pump work

Answer 24

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 25

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

Answer 25

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

Question 26

What drives the transport of glucose in the small intestine

Answer 26

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

Question 27

What is the glucose transporter responsible for

Answer 27

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