The Endomembrane System

Question 1

What is the plasma membrane primarily made of

Answer 1

• phospholipids
• cholestorol
• proteins

Question 2

What are the 3 main functions of the plasma membrane

Answer 2

• import and export molecules
• receive information
• capacity for movement and expansion

Question 3

What is the effect of unsaturated lipids on the membrane

Answer 3

more fluidity

Question 4

Outline phospholipids in the membrane

Answer 4

• amphipathic
• hydrophilic heads facing outwards
• hydrophobic tails facing inwards

Question 5

Why are phospholipids arranged in this manner

Answer 5

• energetically favourable
• water/charged molecules cannot pass the hydrophobic core easily
• makes a good barrier between the interior and exterior of the cell

Question 6

What are the different types of membrane proteins

Answer 6

• enzymes
• ion channel
• anchor
• receptors

Question 7

What molecules have high permeability through the plasma membrane

Answer 7

gases + steroids + hormones + non-polar molecules

Question 8

What molecules have low permeability through the plasma membrane

Answer 8

ions + large uncharged molecules (ex: glucose)

Question 9

Which type of molecules cannot pass through the membrane via diffusion

Answer 9

hydrophobic and non-polar molecules

Question 10

What is simple diffusion

Answer 10

Particles moving from a high to low concentration w/ no energy

Question 11

What is facilitated diffusion

Answer 11

molecules move from the region of higher concentration to the region of lower concentration with carrier or channel or aquaporin protein

Question 12

What type of molecules move via facilitated diffusion

Answer 12

polar molecules + ions

Question 13

Where are aquaporins found the most

Answer 13

kidney tubules

Question 14

What is the main function of aquaporins

Answer 14

highly specialised channel proteins that enable water to move very quickly across the membrane

Question 15

What is an example of facilitated diffusion with carrier protein

Answer 15

glucose uptake by GLUT4

Question 16

What is the function of GLUT4

Answer 16

facilitates transport of glucose into the cell

Question 17

Define uniporter

Answer 17

one substance in one direction

Question 18

Define symporter

Answer 18

2 different substances in the same direction

Question 19

Define antiporter

Answer 19

2 different substances in opposite directions

Question 20

Outline how glucose is transported into the cell

Answer 20

1. insulin binds to receptors
2. receptors phosphorylate
3. start signal cascade
4. allows GLUT4-containing vesicles to reach cell membrane and fuse
5. glucose can enter the cells through these transporters via facilitated diffusion

Question 21

What is primary active transport

Answer 21

it directly uses ATP to move molecules across a membrane against their concentration gradient

Question 22

What is secondary active transport

Answer 22

• does not directly use ATP to move molecules
• relies on the energy stored as an ion gradient created by primary active transport

Question 23

What are the 3 main mechanisms

Answer 23

nuclear transport
membrane transport
vesicle transport