Forces Across Membranes

Question 1

What does it mean to say membranes are Dynamic?

Answer 1

Constantly formed, maintaines, dismantled or metabolised depending on the cells needs

Question 2

What makes cell membranes flexible?

Answer 2

The fatty acids

Question 3

What are the 2 classes of membrane protein?

Answer 3

Integral

Peripheral

Question 4

What makes an integral membrane protein?

Answer 4

• Cant be removed without disrupting the membrane

- Amphipathic & oriented the same way as the phospholipids

Question 5

What are the 4 types of integral membrane protein?

Answer 5

• Channels
• Carriers
• Enzymes
• Receptors

Question 6

What are peripheral proteins important for?

Answer 6

Cell shape & motility

Question 7

What makes up schwann cell membranes?

Answer 7

18% protein

Mainly lipid for insulation against electrical nerve signals

Question 8

How much protein is in the average cell?

Answer 8

Around 50%

Question 9

What factors aid diffusion?

Answer 9

Large surface area
High Permeability
High conc. gradient

Question 10

What characteristics must a molecule have to diffuse through the lipid bilayer?

Answer 10

• Small
• Uncharged
• Hydrophobic (lipophilic)

Question 11

What is a protein channel?

Answer 11

A trans-membranous IMP that act as an aqueous route for ion diffusion

Question 12

Name the protein channels through which water goes?

Answer 12

Aquaporins

Question 13

What are the two types of ‘gated’ channel?

Answer 13

Voltage gated

Ligand Gated

Question 14

In general what is the electrical gradient across cell membranes?

Answer 14

USually the inside is relatively negative to the outside

Question 15

How do carrier mediated transport systems work?

Answer 15

A solute binds to a transmembranous protein
The protein changes coniguration
Solute is now exposed to the other side of the membrane
Solute detaches into the cell

Question 16

What are the two types of carrier mediated transprot systems?

Answer 16

Facilitated transport

Active Transport

Question 17

Difference between facilitated & active transport?

Answer 17

Facilitated requires no energy

Active goes against conc. gradient

Question 18

Why are active transport pumps called ATPases?

Answer 18

They get their energy from ATP.

Question 19

What is osmolarity?

Answer 19

The measure of osmoles of solute per litre of solvent.

Question 20

Osmolarity example:

Answer 20

1M glucose has an osmolarity of 1 osmole/L

Question 21

Define osmotic pressure:

Answer 21

The pressure required to prevent water movement from high->low conc.

Question 22

Explain hypo-,hyper-,iso- osmotic?

Answer 22

Isostomic solutions have same total number of solute particles
Hyperosmostic solution has more solute particles than the ECF
Hypoosmotic have fewer solute molecules than the ECF

Question 23

What is tonicity?

Answer 23

Number of non-penetrating particles in solution.

Question 24

Why does only tonicicty determine water movement?

Answer 24

Penetrating solutes will move across the membrane to equal concs.
Non-penetrating cant so the water will have to move to compensate.

Question 25

Define endocytosis?

Answer 25

Invagination of membrane
Vesicle forms around target
Seperates from membrane on cytoplasmic side
Migrates within cell to destination

Question 26

Exocytosis?

Answer 26

Endo but in reverse m8