Cells and Processes - Transport Across Cell Membranes

Question 1

What are the 5 different transport methods?

Answer 1

Non-Mediated Transport 
Mediated Transport
Passive Transport
Active Transport
Vesicular Transport

Question 2

What is the difference between non-mediated and mediated transport?

Answer 2

Non-mediated transport = Transport protein used

Mediated Transport = NO transport protein

Question 3

What is non-mediated transport?

Answer 3

Does not directly use a transport protein

Molecules are permeable across the hydrophobic corse of the phospholipid bi-layer

Question 4

What is mediated transport?

Answer 4

Moves materials with the help of a transport protein

Question 5

Passive transport

Answer 5

Moves substances down their concentration or electrochemical gradients with only their kinetic energy
Ie: ALWAYS going from a high to low gradient

Question 6

What is a passive transport scenario?

Answer 6

When the ball rolls down the stairs of the lecture theatre

This is because it just rolls down its gradient using the kinetic energy

Question 7

Active Transport

Answer 7

Uses energy to drive substances against their concentration or electrochemical gradients

Question 8

What is a scenario of active transport?

Answer 8

The process of walking the ball up the stairs of the lecture theatre requires energy

This is because kinetic energy is used to bring the ball up the stairs

Question 9

What is the definition of vesicular transport?

Answer 9

The movement of materials across membranes in small vesicles either by exocytosis or endocytosis.

Question 10

What is non-mediated transport important for?

Answer 10

Absorption of nutrients, excretion of wastes

Question 11

What types molecules undergo non-mediated transport?

Answer 11

Non-polar, hydrophobic molecules

Ie: They can interact with the hydrophobic core

Question 12

What is the function of ion channels?

Answer 12

Mediate the movement of ions down their electrochemical gradient

Question 13

What is formed in the centre of an ion channel and what are its functions

Answer 13

A water filled pore that shield the ions from the hydrophobic core of the lipid bi-layer

Question 14

What determines what ions can pass through an ion channel (ionic selectivity)

Answer 14

Certain amino acids lining the pore determine this

Question 15

What is ionic selectivity?

Answer 15

Ion channels only allow certain ions to flow through

Question 16

What is the result of channels being ion selective?

Answer 16

The channel can harness the energy stored n the different ion gradients.

Question 17

Why can ion channels NOT be open all the time?

Answer 17

It would diminish the ion gradient

Question 18

What do ion channels contain to control the passage of ions?

Answer 18

Gates

Question 19

Examples of stimuli that control channel gate opening and closing

Answer 19

Voltage, ligand binding, cell volume (stretch), pH, phosphorylation

Question 20

What is a patch clamp?

Answer 20

A sensitive voltage clamp method that permits the measurements of ionic currents flowing through individual ion channels

Question 21

Number of ions that are able to diffuse through one ion channel per second?

Answer 21

1 million

Question 22

The current through a single ion channel

Answer 22

10^-12 amps

Question 23

How does carrier mediated transport work?

Answer 23

The substrate to be transported directly interacts with the transporter protein

Question 24

Is carrier mediated transport faster or slower than ion channels and why

Answer 24

Slower

Because the transporter undergoes a conformation change

Question 25

What is the general function of carrier mediated transport?

Answer 25

To take one molecule from one side of the membrane to the other

Question 26

Carrier proteins exhibit these 4 properties?

Answer 26

Specificity
Inhibition
Competition
Saturation

Question 27

Is carrier mediated transport active or passive?

Answer 27

It can be both

Question 28

What does saturation mean for carrier mediated transporters?

Answer 28

They only have a certain number of binding pockets so they cannot intake anymore molecules than their binding pockets allow

Question 29

Does increasing concentration increase uptake with carrier mediated proteins?

Answer 29

To a point, eventually, a point is reached where uptake is saturated

Question 30

Name of protein that uptakes glucose?

Answer 30

Glucose Transporter Protein (GLuT)

Question 31

Amount of glucose in blood?

Answer 31

5

Question 32

Process of glucose moving into a cell?

Answer 32

Glucose BINDS to the the transport channel protein
Binding causes a conformational change in the shape of the protein
Allows glucose to then move into the cell

Question 33

Does glucose move down its concentration gradient in facilitated diffusion?

Answer 33

Yes

Question 34

What is glucose converted into in the cell by a kinase enzyme?

Answer 34

Glucose-6-phosphate

Question 35

Why is glucose converted into glucose-6-phosphate?

Answer 35

To maintain the glucose concentration gradient

Question 36

What cells do facilitated diffusion of glucose?

Answer 36

Muscle, nervous, fat cells

Question 37

What is Glut NOT called?

Answer 37

Do NOT call this a glucose channel that is doing passive diffusion.

Glut is a carrier protein and undergoes passive, facilitated diffusion

Question 38

Process of sodium and potassium ATPase

Answer 38

1. Na+ binds
2. ATP is split and Na+ is pushed out of the cell
3. K+ binds and phosphate is released
4. K+ is pushed in

Question 39

With a Na/KATPase, how many Na+ are removed?

Answer 39

3 Na+ ions are removed from the cell

Question 40

With a Na/KATPase, how many K+ are brought into the cell?

Answer 40

2 K+ ions are brought into the cell

Question 41

What is the result of a Na/KATPase?

Answer 41

Pump generates a net current and is electrogenic