exam revisions - membranes

Question 1

Function of membrane

Answer 1

controls the flow of materials both into and out of the cells. It is semi or selectively permeable

Question 2

Structure of membrane

Answer 2

The structure of the cell membrane allows movement of material to occur using a number of methods. It is been described by the fluid mosaic model.

Question 3

What is the fluid mosaic model?

Answer 3

describes the structure of the plasma membrane. ‘Fluid’ describes the hydrophobic tails and phospholipids which give the structure an oily, fluid like movement. The term ‘mosaic’ describes how the external surface appears with the proteins embedded in the phosphate background.

Question 4

What is a glycoprotein

Answer 4

plays an important role in cellular recognition and immune responses. They help stabilise the membrane structure.

Question 5

What is a glycolipid

Answer 5

act as surface receptors and stabilise the membrane, also have a role in helping cells to aggregate in formation of tissues

Question 6

What is a peripheral protein

Answer 6

some proteins are stuck to the surface of the membrane

Question 7

What is an integral protein

Answer 7

some proteins completely penetrate the phospholipid bilayer. These proteins may control the movement of specific molecules into and out of cell.

Question 8

What is cholesterol in the membrane

Answer 8

Cholesterol in the membrane disturbs the close packing of the phospholipids and keeps the membrane more fluid.

Question 9

What is diffusion

Answer 9

diffusion is the movement of molecules/ substances across a plasma membrane. The substance moves down their concentration gradients and passively through the membrane.

Question 10

Types of diffusion

Answer 10

Simple diffusion
Facilitated diffusion
Active transport

Question 11

What is simple diffusion and examples of substances which use this process

Answer 11

Passive transport is the process of movement of substance across a membrane from a region of high concentration to a region of low concentration.
examples include; small water molecules, steroids, alcohol, carbon dioxide, oxygen.

Question 12

what is facilitated diffusion and examples of substances which use this process

Answer 12

Is the movement of molecules across membranes which cannot pass the hydrophilic bilayer, so instead travel through a protein channel. This does not require energy to occur, the molecules move down their concentration gradient.

Question 13

what is osmosis

Answer 13

osmosis is defined as the net movement of water molecules across a partially permeable membrane from a region of high to low concentration.

Question 14

What is an isotonic solution

Answer 14

when two solutions contain the same concentration of the solute

Question 15

What is a hypotonic solution

Answer 15

having a lower solute concentration than the cells contents

Question 16

What is a hypertonic solution

Answer 16

having a higher solute concentration than the cells contents

Question 17

What is active transport

Answer 17

active transport processes require energy expenditure because materials must move against their concentration gradient. It is performed by specific carrier proteins.

Question 18

What are the types of bulk transport processes

Answer 18

Endocytosis - getting in

Exocytosis - getting out

Question 19

What is endocytosis

Answer 19

the process which allows solid particles to be taken into a cell. Part of the plasma membrane encloses the material then pinches off to form a vesicle which move into the cytosol.
Two types
- phagocytosis (solid material)
- pinocytosis (fluid material)

Question 20

What is exocytosis

Answer 20

the process which allows solid particles to be removed from a cell. Vesicles formed within a cell fuse with plasma membrane, contents are released from the cell.