Proteins in the membrane

Question 1

Cell membrane consists of

Answer 1

Phospholipids and proteins

Question 2

The cell membrane is (permeability)

Answer 2

Selectively permeable, allows smaller soluble molecule through but not large insoluble molecules

Question 3

How are molecules transported across the membrane

Answer 3

Molecules can be passed across by passive transport, moving down the concentration gradient - this does not require energy.
They can also move across by active transport moving up the concentration gradient requiring energy.

Question 4

What do enzymes do

Answer 4

Speed up cellular reactions and are unchanged in the process

Question 5

Fluid mosaic structure of the membrane

Answer 5

Made up of layer of phospholipids, which are constantly moving - why it is said to be fluid. It has larger proteins embedded in the phospholipids, which is why it is said to be mosaic

Question 6

Roles of membrane proteins

Answer 6

They act as enzymes and involved in cell communication, they are also essential for intracellular and extracellular transport

Question 7

Transport proteins - pores

Answer 7

Allow molecules to move across them by facilitated diffusion, they form pores to allow molecules to move passively across them

Question 8

Transport proteins - pumps

Answer 8

Active transport requires ions or molecules to be pumped against the concentration gradient, energy released from the breakdown of ATP need to change the shape of the protein and allow the molecules or ions to transport across the membranes
e.g. sodium - potassium pump.

Question 9

What factors affect how quickly a pump can operate

Answer 9

Temperature and availability of oxygen and glucose affect the rate of respiration and therefore the rate of active transport (since
this requires energy/ATP)

Question 10

Enzymes in the membrane

Answer 10

Some proteins in the membrane are enzymes which catalyse steps within cellular metabolic processes
e.g. ATP synthase