Water and Movement Across the Membrane

Question 1

What does amphipathic mean?

Answer 1

• A molecule containing an area of hydrophobic and of hydrophilic nature

Question 2

How do water soluble molecules arrange themselves in solution?

Answer 2

• Water- water H bonding of the water is replaced by

- Water- solute bonding

Question 3

What do water soluble molecules arrange themselves like this?

Answer 3

• Water-solute hydrogen bonding is more favourable

Question 4

How do uncharged molecules arrange themselves in water?

Answer 4

In such a way that will bring the least amount of disruption to the water-water bonds

Question 5

What are uncharged molecules said to form in solution?

Answer 5

Cages

Question 6

What do phospholipids form to minimise water disruption?

Answer 6

• Micelles

- Bilayers

Question 7

What are buffers?

Answer 7

Solutions of weak acids that dissociate to form a conjugate acid-base

Question 8

What 3 things aid diffusion?

Answer 8

• Large surface area
• High permeability
• High conc. gradient

Question 9

What 3 properties do molecules need to have to diffuse across the membrane?

Answer 9

• Small
• Uncharged
• Lipophobic

Question 10

What 2 elements can cross the membrane easily?

Answer 10

• N2
• O2
  Because they are small and uncharged (symmetry)

Question 11

What two waste compounds can easily cross the membrane?

Answer 11

• Urea

- CO2

Question 12

What are the 2 classes of membrane proteins?

Answer 12

• Integral

- Peripheral

Question 13

4 types of integral proteins?

Answer 13

• Channels
• Carriers
• Enzymes
• Receptors

Question 14

What happens to the plasma membrane if integral proteins are removed?

Answer 14

It is disrupted

Question 15

Relative “amphipathicness” of integral and peripheral proteins

Answer 15

Integral = amphipathic
Peripheral = not

Question 16

Where are peripheral proteins found?

Answer 16

Inner side of the membrane

Question 17

What do peripheral proteins tend to be?

Answer 17

Enzymes

Question 18

What do peripheral proteins play a key role in?

Answer 18

Cell shape and motility

Question 19

What is an example of a peripheral protein that is important for cell shape and motility (hint: the gene for its coding is lost in duchennes dystrophy)

Answer 19

Dystrophin

Question 20

Name two cells and their membrane protein percentage to show how different membranes can be

Answer 20

• Schwann cells (18%)

- Mitochondria (75%)

Question 21

What protein does water use to enter/exit the cell?

Answer 21

Aquaporin

Question 22

What are the 2 types of gated channels

Answer 22

• Voltage gated

- Ligand gated

Question 23

How does voltage changes cause voltage gated channels to open??

Answer 23

• It acts on charged regions of the protein

- Causes a conformational change

Question 24

Define osmolarity

Answer 24

• Number of osmoles of solute per litre of solution

Question 25

Define osmolality

Answer 25

• Number of osmoles of solute per kg of solvent

Question 26

Osmolarity of 1M of glucose?

Answer 26

1 osmol/L

Question 27

Osmolarity of 1M of NaCl

Answer 27

2osmol/L

Question 28

What determines the tonicity?

Answer 28

Conc of non penetrating solutes on 2 sides of the membrane

Question 29

What happens if the ECF has a higher tonicity than the ICF?

Answer 29

• Cell is hypotonic

- Cell will swell as water enter

Question 30

What happens if the ECF has a lower tonicity than the ICF?

Answer 30

• Cell is hypertonic

- Cell will shrink as water leaves

Question 31

What is an isosmotic solution?

Answer 31

Equal number of both penetration and non penetrating solutes on either side of the membrane

Question 32

Isotonic?

Answer 32

Equal number of non penetrating solutes on each side