Cell Membranes

Question 1

Name 3 roles of membranes within and at the surface of cells?

Answer 1

Act as a partially permeable barrier between the cell and its environment and also between organelles and the cytoplasm within organelles

Site of chemical reactions

Site of cell communication

Question 2

What is the structure and function of the phospholipid bilayer?

Answer 2

Hydrophilic phosphate heads on outside, hydrophobic tails on inside

Central hydrophobic section doesn’t allow water soluble substances to pass through easily = barrier

Question 3

What is the structure and function of cholesterol?

Answer 3

Cholesterol is a lipid with hydrophobic and hydrophilic end

Binds in between phospholipids (to tails) so they’re closer together making the membrane more fluid and stronger

Question 4

What is the structure and function of glycolipids?

Answer 4

Lipid on membrane with carbohydrate chain attached

Stabilise membrane by forming h bonds with surrounding water

Receptors where drugs hormones and antibodies bind

Receptors in cell signalling

Antigens- recognise as self

Question 5

What is the structure and function of a glycoproteins?

Answer 5

And extrinsic protein with carbohydrate chain attached

For cohesion of cells

Receptors for cell signalling

Receptors for drugs hornmones and antibodies

Question 6

What do proteins do in the cell membrane?

Answer 6

Intrinsic proteins - channel and carrier proteins transport molecules across the membrane

Extrinsic proteins - on one side of the bilateral

Question 7

What is the effect of temperature on membrane permeability?

Answer 7

Phospholipids gain kinetic energy = move more

This increases fluidity of membrane and it loses structure
= increase permeability

Channel and carrier proteins denature
- increases permeability

Question 8

What is the effect of solvents on membrane permeability?

Answer 8

Organic solvents can dissolve the lipids in membranes as they are less polar than water
= more permeability

Question 9

How can you investigate membrane permeability?

Answer 9

Using betroot
More pigment released = higher permeability

Higher absorbency on colorimeter

Question 10

Define diffusion

Answer 10

The net movement of particles from an area of high concentration to an area of lower concentration

Question 11

What is facilitated diffusion?

Answer 11

Diffusion across a methane through channel protein (polar substances as inside of Chanel proteins are polar)

Question 12

Define active transport

Answer 12

The movement of molecules from an area of low concentration to high concentration requiring energy ATP
Using carrier proteins

Question 13

1. A molecule or ion binds to a _______ in a protein on the cell membrane
2. Inside the cell _____ binds to the carrier protein and is hydrolysed to __________ and ____
3. ______ binds to the carrier protein and changes it’s ________
4. Molecule is _______ into cell
5. ________ released and recombined with _____ to make _____
6. Carrier protein returns to original state

Answer 13

Receptor
Phosphate 
ADP
Phosphate 
Shape
Released
Phosphate 
ADP 
ATP

Question 14

Describe endocytosis

Answer 14

Phagocytosis (solids) or pinocytosis(liquids)

Membrane invaginates

Membrane enfolds material until it fuses to form a vesicle

Vesicle pinches off and moves to cytoplasm

Question 15

Describe exocytosis

Answer 15

Vesicles formed at the Golgi

Vesicles move to and fuse with cell surface membrane

Contents released outside cell

Question 16

What happens when an animal cell is placed in a hypotonic solution?

Answer 16

It undergoes cytolysis

It bursts

Question 17

What happens when you place and animal cell in a hypertonic solution?

Answer 17

In becomes crenated

Question 18

What happens when you place a plant cell in a hypotonic solution

Answer 18

It becomes turgid

Doesn’t burst as cell wall is strong and prevents more water entering

Question 19

What happens when you place a plant cell in a hypertonic solution?

Answer 19

It becomes plasmolysed
The protoplast ( cell surface menrahe) pulls away from the cell wall

Question 20

How do you investigate diffusion?

Answer 20

Using agar jelly as model cells

Question 21

describe the structure of the cell surface membrane

Answer 21

phospholipid bilayer containing proteins

hydrophillic heads facing outwards

hydrophobic tails facing inwards

intrinsic-across full width of membrane including carrier and channel rproteins and extrinsic proteins which are on one side of the membrane such as glycoproteins

glycoproteins and glycolipids that are extrinsic and stick out of the membrane

cholesterol between phospholipids

Question 22

what is cell signalling?

Answer 22

communication between cells

chemicals released from one cell attaches to and causes change in another cell

Question 23

how are vesicles moved around the cell?

Answer 23

by the cytoskeleton

move along the microfilaments which extend or breakdown to move them

uses ATP