Unit 1 - Topic 3 - Membrane Proteins - Section A - Movement of molecules across membranes

Question 1

What is the fluid mosaic model

Answer 1

The fluid mosaic model describes the structure of the plasma membrane. The phospholipid bilayer can move so it is fluid and the different proteins are like small pieces of a mosaic.

Question 2

Describe the structure of the plasma membrane

Answer 2

The phospholipid is the basis of the system as it has a hydrophilic head and hydrophobic tails. The head is toward the aqueous cytoplasm and extracellular fluid while the tail is towards the inside of the bilayer.

Question 3

What do regions of hydrophobic R groups allow

Answer 3

Strong hydrophobic interactions that hold integral membrane proteins within the phospholipid bilayer

Question 4

Integral membrane proteins interact extensively with what

Answer 4

The hydrophobic region of membrane phospholipids.

Question 5

What are some integral membrane proteins

Answer 5

Transmembrane proteins

Question 6

Describe peripheral membrane proteins

Answer 6

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

Question 7

Many peripheral membrane proteins interact with what

Answer 7

The surfaces of integral membrane proteins

Question 8

What is the phospholipid bilayer

Answer 8

Is a barrier to ions and most uncharged polar molecules

Question 9

What molecules can pass through the bilayer by simple diffusion

Answer 9

Some small molecules, such as oxygen and carbon dioxide

Question 10

What is facilitated diffusion

Answer 10

Facilitated diffusion is the passive transport of substances across the membrane through specific transmembrane proteins

Question 11

To perform specialised functions what do different cell types have

Answer 11

Different cell types have different channel and transporter proteins

Question 12

What are most channel proteins in animals and plant cells

Answer 12

Highley selective

Question 13

What are channels

Answer 13

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

Question 14

What are some channels proteins

Answer 14

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

Question 15

What are ligand-gated channels controlled by

Answer 15

The binding of signal molecules, and voltage-gated channels are controlled by changes in ion concentration

Question 16

How do transporter proteins work

Answer 16

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

Question 17

What do transporter proteins alternate between

Answer 17

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

Question 18

What type of protein does active transport use

Answer 18

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

Question 19

What are pumps that mediate active transport

Answer 19

Pumps that mediate active transport are transporter proteins coupled to an energy source

Question 20

What is required for active transport

Answer 20

A source of metabolic energy

Question 21

What do ATPases do

Answer 21

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