Membranes

Question 1

What are membranes made out of?

Answer 1

Phospholipid bilayer

Question 2

What are the properties of membranes?

Answer 2

Dynamic, flexible, insulating, selective permeability and act as binding sites for chemical recognition

Question 3

What provides membranes with flexible properties?

Answer 3

Fatty acids

Question 4

What provides membranes with insulating properties?

Answer 4

Hydrocarbon tails

Question 5

What does dynamic mean?

Answer 5

Always being made and destroyed depending on the needs of the cell

Question 6

What type of cell has the most protein?

Answer 6

Mitochondria

Question 7

What are the 2 types of membrane proteins?

Answer 7

Integral and Peripheral

Question 8

What is a peripheral membrane protein?

Answer 8

A protein that can be removed without disturbing the membrane. It is non-amphiphatic and its binding sites are on the IC side of the membrane. They can act as enzymes and are important for cell size and motility

Question 9

What is an integral membrane protein?

Answer 9

A protein that can’t be removed without disturbing the membrane. It is amphipathic and its has the same orientation as the phospholipids and may span the membrane. They can act as channels, carriers, enzymes and receptors

Question 10

Why do membrane proteins act as channels?

Answer 10

Allows ions to cross the membrane

Question 11

Why do membrane proteins act as carriers?

Answer 11

Allows substances to be transported across the membrane

Question 12

Why do membrane proteins act as enzymes?

Answer 12

To provide binding sites on the membrane surface

Question 13

Why do membrane proteins act as receptors?

Answer 13

To provide recognition sites for chemicals

Question 14

Where does diffusion occur?

Answer 14

Between compartments

Question 15

What is the process of diffusion?

Answer 15

Movement form high -> low concentrations

Question 16

What are the requirements for diffusion?

Answer 16

Permeable to the membrane, small, uncharged and lipophilic (hydrophobic)

Question 17

What helps diffusion?

Answer 17

Large surface area, high permeability and high concentration gradient

Question 18

What are protein channels?

Answer 18

They are trans-membranous IMPs that act as an aq route for the diffusion of ions

Question 19

How does water pass thorough the membrane?

Answer 19

Through aquaporins which are always open

Question 20

What is the name of changels that are not always open?

Answer 20

Gated

Question 21

What are the 2 types of gated channels?

Answer 21

Voltage and Ligand

Question 22

What are ligand gated channels?

Answer 22

When a certain chemical binds to the channel, its configuration changes which causes the channel to open/close

Question 23

What is an example of a ligand gated channel?

Answer 23

ACh receptors

Question 24

What is a voltage gated channel?

Answer 24

Channels open/close due to a change in electrical potential which causes a change in configuration

Question 25

What is an example of a voltage-gated channel?

Answer 25

Na+ in nerve cells

Question 26

How are electrochemical gradients formed?

Answer 26

Generated by the membrane potential. The inside of the cell is -ve due to a separation of charge across cell membranes

Question 27

What is an electrochemical gradient needed for?

Answer 27

Ion diffusion

Question 28

What uses carrier mediated transport systems?

Answer 28

Ions that can't cross the channel and uncharged molecules e.g. glucose

Question 29

What are the 2 ways that carrier mediated transport systems work?

Answer 29

Facilitated diffusion and active transport

Question 30

What do carrier mediated proteins contain?

Answer 30

Binding sites for ions that can't pass through the channel and uncharged molecules

Question 31

What is the process by which carrier mediated proteins operate?

Answer 31

They bind to the solute which causes a change in configuration which exposes the site on the other side of the membrane. This allows the solute to diffuse into the cell and then the protein returns to its normal shape

Question 32

What is facilitated diffusion?

Answer 32

The process by which solutes are transported down their concentration gradient, with no direct energy source needed

Question 33

What is active transport?

Answer 33

The process by which substances move against their concentration gradients. ATP is required and it is caused by ATP synthase. An electrogenic pump is used which creates a net -ve charge. This takes up 40% or resting body energy

Question 34

What is released by active transport?

Answer 34

3x Na+

Question 35

In active transport, what is taken up by each molecule of hydrolysed ATP?

Answer 35

2x K+

Question 36

What is osmolarity?

Answer 36

The measure of solute concentration

Question 37

What is the osmolarity of 1M of glucose?

Answer 37

1 osmole/L

Question 38

What is the osmolarity of 1M of NaCl?

Answer 38

2 osmole/L

Question 39

What determines tonicity?

Answer 39

Cell volume, which depends on the concentration of non-penetrating solutes on either side of the membrane

Question 40

What is a hypertonic solution?

Answer 40

ECF has a higher tonicity than ICF, which causes cells to shrink as water leaves the cell by osmosis to compensate

Question 41

What is a hypotonic cell?

Answer 41

ICF has a higher tonicity than ECF, which causes the cells too swell as water enters the cell

Question 42

What is an isosmotic solution?

Answer 42

A solution with equal numbers of both penetrating and non-penetrating solutes on either side of the membrane

Question 43

What is an isotonic solution?

Answer 43

A solution with equal numbers of non-penetrating particles on either side of the membrane

Question 44

What is the process of endocytosis?

Answer 44

The membrane is turned inside out then a vesicle forms around the target substance. The vesicles then separate from the membrane on the cytoplasmic side and migrate within the cell to its destination

Question 45

What is exocytosis?

Answer 45

The opposite of endocytosis