Unit 1 - Cells and Proteins - 1.3 Membrane Proteins

Question 1

(a) Movement of molecules across
membranes

Answer 1

a+

Question 2

What is the model of cell membranes?

Answer 2

Fluid mosaic

Question 3

What is the fluid mosaic model of the cell membrane?

Answer 3

The cell membrane is double-layered layered consisting of fats (phospholipids) and
proteins.

Phospholipids have a hydrophilic head and a hydrophobic tail.

We say the cell membrane is selectively permeable.

Question 4

What about the phospholipid bilayer?

Answer 4

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

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

Question 5

What can proteins in the cell membrane either be?

Answer 5

Peripheral - on one side of the membrane

Integral - held inside the lipid bilayer

Question 6

What about peripheral membranes?

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

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

Question 7

What about integral membranes?

Answer 7

Regions of hydrophobic R groups allow 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 8

What are some integral membrane proteins?

Answer 8

transmembrane proteins, as they go from one side of the membrane to the other

e.g. protein pores, protein pumps, enzymes.

Question 9

What are the types of transport that involve proteins?

Answer 9

Facilitated Diffusion
Active Transport

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

What is active transport?

Answer 11

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

Question 12

What about the types of proteins?

Answer 12

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

Question 13

What are the different types of membrane proteins?

Answer 13

Channel Proteins
Gated Channel
Transporter (Carrier) Proteins
Protein Pumps