2.5 Protiens In Membranes

Question 1

How much of a cell membrane do proteins make up?

Answer 1

45% by mass (can vary from 25% to 75%)

Question 2

What are intergral proteins?

Answer 2

Proteins that span the whole width of the membrane

Question 3

What are other names for intergral proteins?

Answer 3

Intrinsic

Transmembrane

Question 4

What are peripheral proteins?

Answer 4

Proteins confined to the inner or outer membrane surface

Question 5

What is another name for peripheral proteins?

Answer 5

Extrinsic

Question 6

What are many intergral proteins?

Answer 6

Carrier molecules of channels

Question 7

What do intergral carrier molecules or channels help do?

Answer 7

Transport may substances such as ions, sugars and amino acids that cannot diffuse across the membrane but are still vital to a cells functioning

Question 8

What are other intergral proteins that are not channel or carrier molecules?

Answer 8

Receptors for hormones and neurotransmitters
Or
Enzymes for catalysing reactions

Question 9

Where are intergral proteins found?

Answer 9

Embedded through both layers of the membrane

Question 10

How are intrinsic proteins kept in place?

Answer 10

They have amino acids with hydrophobic R groups in their external surfaces which interact with the hydrophobic core of the membrane, keeping them in place

Question 11

What do channel proteins do?

Answer 11

They provide a hydrophilic channel allowing passive movement of polar molecules and ions down a concentration gradient through membranes

Question 12

What do carrier proteins play an important role in?

Answer 12

Passive and active transport into cells

Question 13

Where are peripheral proteins found?

Answer 13

Free on the membrane surface or bound to intergral proteins

Question 14

What do peripheral proteins on the extra cellular side of the membrane act as?

Answer 14

Receptors for hormones and neurotransmitters or are involved in cell recognition

Question 15

What are many peripheral proteins on the extra cellular side of the membrane?

Answer 15

Glycoproteins (conjugated)

Question 16

What are peripheral proteins on the cytosolic side of the membrane involved in?

Answer 16

Cell signalling or chemical reactions

Question 17

What can peripheral proteins on the cytosolic side of the membrane do?

Answer 17

Dissociate from the membrane and move into the cytoplasm

Question 18

Give an example of a peripheral protein that is an enzyme:

Answer 18

ATPase in the mitochondria

Question 19

Where are extrinsic/peripheral proteins present?

Answer 19

In only one side of the bilayer, they are able to move between layers

Question 20

What do peripheral proteins have on their outer surfaces and what do they do?

Answer 20

Hydrophilic r groups on their outer surfaces that interact with the polar heads of the phospholipids or with intrinsic proteins

Question 21

What is ATPase and where is it found?

Answer 21

An enzyme involved in the production of ATP it is found in the inner membrane of the mitochondria

Question 22

What are glycoproteins?

Answer 22

Intrinsic proteins embedded in the cell surface membrane with a carbohydrate chain attached

Question 23

What are recognition proteins?

Answer 23

Proteins on the extra cellular side of the cell acting as receptors for hormones or neurotransmitters approaching the cell