1.3 membrane proteins

Question 1

Types of membrane protein

Answer 1

Integral and peripheral proteins

Question 2

Integral proteins

Answer 2

Proteins which interact with the hydrophobic tails of the plasma membranes phospholipid bi layer.

Question 3

Peripheral proteins

Answer 3

Proteins attached to the phospholipid hydrophilic head in the plasma membrane.

Question 4

Fluid mosaic model

Answer 4

Shows the arrangement and structure of the plasma membrane.

Question 5

Transmembrane proteins

Answer 5

Proteins which span the entire width of the plasma membrane.
(Some integral proteins are transmembrane.)

Question 6

How are integral proteins held in the phospholipid bi layer

Answer 6

By hydrophobic interactions between the integral proteins R groups and the hydrophobic tail of the phospholipid.

Question 7

How are peripheral proteins held on the surface of the bi layer

Answer 7

By ionic and hydrogen bonding interactions with the hydrophilic head of the phospholipid bi layer.

Question 8

Interaction between integral and peripheral proteins

Answer 8

They interact on the surface exterior of the phospholipid bi layer.

Question 9

Phospholipid bi layer characteristics

Answer 9

The head is hydrophilic
The tail is hydrophobic

Question 10

Rule for molecules passing through the bi layer.

Answer 10

Small molecules can pass through the bi layer (carbon dioxide and oxygen)

Uncharged polar molecules and ions cannot pass through the bi layer due to ionic head.

Question 11

Facilitated diffusion definition

Answer 11

The passive transport of a substance across a membrane through specific transmembrane proteins.

Question 12

How do specialised plasma membrane functions take place

Answer 12

Different cell types will have unique transporter and channel proteins.

Question 13

Channel proteins

Answer 13

Highly selective multi subunit proteins with subunits arranged to form water filled pores that extend across the membrane.

Question 14

Types of channel proteins

Answer 14

Ligand gates and voltage gated

Question 15

Ligand gated channel proteins

Answer 15

Channel proteins controlled by the binding of a signal molecule which allows for a conformational change, which will open the channel and allow specific molecules down the concentration gradient into the cell.

Question 16

Voltage gated channel proteins

Answer 16

Channel proteins controlled by changes in ion concentration, which undergo a conformational change when the membrane potential changes.

Question 17

Transporter proteins

Answer 17

Proteins which bind to a specific substance, which will cause the protein to undergo a conformational change and transfer the molecule across the membrane.

Question 18

Specific feature of transporter proteins

Answer 18

They will alternate between two conformations so that the binding site is on opposite sides of the plasma membrane.

Question 18

Pump proteins

Answer 18

Transmembrane proteins which actively transport molecules across the membrane against the concentration gradient

Question 19

Active transport

Answer 19

The movement of molecules against a concentration gradient using protein pumps and requiring energy.

Question 20

ATPases

Answer 20

A type of protein pump which directly hydrolyses ATP to produce the energy needed for active transport.

Question 21

Electrochemical gradient definition

Answer 21

The concentration gradient and the electrical potential difference.

Question 22

Electrical potential difference

Answer 22

Also called membrane potential - the difference in electrical charge of inside and outside a cell.

Question 23

Concentration gradient

Answer 23

How molecules move from high to low concentration.

Question 24

Normal potential difference in extra cellular fluid

Answer 24

-70mV

Question 25

Sodium concentration inside cell

Answer 25

Low

Question 26

Sodium concentration outside cell

Answer 26

High

Question 27

Potassium concentration inside cell

Answer 27

High

Question 28

Potassium concentration outside cell

Answer 28

Low.

Question 29

Sodium potassium pump process

Answer 29

3 sodium ions will bind to the inside of the pump due to high affinity.
ATP is hydrolysed breaking down into ADP and Pi, Pi phosphorylates the sodium potassium ATPase
Conformational change will occur allowing for sodium to be released outside cell.
2 Potassium will then bind to sites outside the cell due to high affinity.
The sodium potassium ATPase will then be de-phosphorylated
This will allow conformational change to occur which will allow 2 potassium ions to be pumped into the cell.

Question 30

Reason for sodium potassium pump

Answer 30

To maintain sodium and potassium ion gradients.

Question 30

How does sodium enter the cell

Answer 30

By facilitated diffusion by voltage gated channel proteins.

Question 31

How does potassium leave the cell

Answer 31

By facilitated diffusion by voltage gated channel proteins.

Question 32

Type of transport for sodium potassium pump

Answer 32

Active transport

Question 33

What percentage of energy is used by sodium potassium ion pump

Answer 33

25% basal metabolic rate
(High)

Question 34

Uses of sodium potassium pump

Answer 34

Small intestine epithelial cells
Neurone firing.

Question 35

Number of sodium out of cells in sodium potassium pump

Answer 35

3 ions

Question 36

Number of potassium into cells in sodium potassium ion pump.

Answer 36

2 ions

Question 37

Sodium potassium pump process in intestinal epithelial cells

Answer 37

Low concentration of sodium in intracellular fluid is pumped into high sodium concentration extracellular fluid.
The sodium then undergoes facilitated diffusion back inside the cell along with the transport of a glucose molecule.

Question 38

Symport definition

Answer 38

Where two molecules are transported across the membrane by the same transporter protein.

Question 39

Symporter definition

Answer 39

A transmembrane protein which transports two different molecules across the plasma membrane at the same time.