Transport across cell membranes

Question 1

Describe passive diffusion

Answer 1

Substances move down their electro or concentration gradient

Question 2

Describe active transport

Answer 2

When substance is moved against its electro or conc gradient with the assistance of energy

Question 3

Describe non mediated diffusion and what kind of transport it is

Answer 3

non mediated diffusion does not need the assistance of a transport protein

Passive transport

Question 4

Describe mediated transport

and what type of transport it is

Answer 4

substances needs the assistance of transport protein to cross the PM

Passive transport

Question 5

Describe mediated transport it more detail

Answer 5

• absorption of substances is associated with excretion and absorption

Transport is of hydrophobic non polar molecules
O2/ N2

Question 6

Describe mediated transport in more detail

Answer 6

Hydrophilic core H2O filled which shields the ions from the hydrophobic region

Transportation is fast as ions do not bind to the channel pore

Question 7

Describe the selectivity of a transport membrane

Answer 7

The channel has a specific amino acid lining- selectivity of the channel to ions

Selectivity= ability to harness energy due to the conc gradient

Question 8

Describe the properties of a gated ion channel

Answer 8

Gate can be either closed or open

Factors that open the ion are 
voltage 
phosphorylation
ph
Stretching (volume)
ligand binding

Question 9

Describe the ion channel gradient and its association with the electrochemical gradient

Answer 9

fluctuation within the electrochemical gradient represents the open and closing of the gate

Question 10

Describe mediated transport

Answer 10

Substrate directly interacts with the transport protein

Transport protein undergoes a confrontational change as the substrate binds.

= slower transportation

Question 11

describe in more depth mediated transport

Answer 11

Similar to enzyme but mediate transport across the cell membrane

They exhibit
Specificity 
Inhibition
Competition
Saturation

They engage in active and passive transport

Question 12

Describe facilitated diffusion of glucose

Answer 12

1. Glucose binds to transporter protein (GLUT)
2. glucose travels down the conc gradient
3. Glucose binds to kinase
   Kinases decreases the conc within the cell
4. glucose is turned into glucose-6-phosphate

Question 13

state a example of primary active transport

Answer 13

Na/K ATPase

Question 14

Describe the process of Na/KATPase and what this mechanism generates

Answer 14

1. 3 NA enter the cell membrane
2. Atp binds to the transporter protein -ATP goes to ADp. Phosphate group is left with the transporter cell
3. 2K enter the transport protein _Phosphate still attached
4. 2K is pushed into the cell
   - this mechanism generates a electrogenic gradient

Question 15

describe primary and secondary transport

Answer 15

primary- used hydrolysis of cell (30% of cells energy used

secondary- stores conc gradient= drive active transport of a molecule against its gradient

Question 16

What is Na/K known as

Answer 16

leaky pump

Question 17

Describe the importance of having a ionic gradient

Answer 17

resting cell membrane
electrical excitability
muscle contraction
cell volume
uptake of nutrients by secondary active transporters
maintenance of 
intracellular ph by 

secondary active transporters

Question 18

Describe secondary active transport and give 2 examples

Answer 18

Concentration gradient is established by the primary active transport (kinetic potential energy)

This energy is used to exchange Na into the cell for a Ca out of the cell.

This is used in a Na antipoter or

Na symporter will cause two ions Na and Ca to enter the cytoplasm.