Lecture 5

Question 1

What does a plasma membrane do?

Answer 1

1.Protects and separates a cell from its environment
2. It is selectively permeable (so it lets in the right things and not the wrong things)

Question 2

Why does the phospholipid bilayer not need to be bonded together?

Answer 2

Because the phospholipids want to form a layer with the tails on the inside and the heads on the outside.

Question 3

Why is it important that the phospholipid bilayer is not bonded together?

Answer 3

Because it allows it to be flexible and allows things to go in and out of the cell.

Question 4

What is the fluid mosaic model?

Answer 4

The model where proteins float in or on the fluid phospholipid bilayer.

Question 5

What are 4 components of cellular membranes?

Answer 5

1. Phospholipid bilayer
2. Transmembrane proteins (proteins in membrane)
3. Interior protein network (proteins on inside)
4. Cell surface markers (proteins on the outside)

Question 6

Types of proteins in membrane?

Answer 6

1. Transporters
2. Enzymes
3. Cell-surface receptors
4. Cell-surface identity markers
5. Cell-to-cell adhesion proteins
6. Attachments to the cytoskeleton

Question 7

What are anchoring molecules?

Answer 7

Modified lipids that have nonpolar regions that insert into the lipid bilayer and chemical bonding domains that link to proteins.

Question 8

What are 2 types of membrane proteins?

Answer 8

1. Integral membrane proteins - go all the way through the lipid bilayer
2. Transmembrane domain - spans the lipid bilayer

Question 9

What types of things can move freely through the lipid bilayer?

Answer 9

1. nonpolar molecules
2. small polar molecules

Question 10

What are 3 types of transport through the plasma membrane (cell membrane)?

Answer 10

1. Passive transport - no energy is required
2. Active transport
3. Bulk transport

Question 11

What are 2 types of passive transport?

Answer 11

1. Diffusion
2. Osmosis

Question 12

What is diffusion?

Answer 12

When molecules move through a semipermeable membrane to where there is more space (lower concentration).

Question 13

What is osmosis?

Answer 13

When water moves through a semipermeable membrane to an area with a higher solute concentration.

Question 14

What is osmotic pressure?

Answer 14

pressure required to oppose osmosis.

Question 15

What is tonicity?

Answer 15

relative concentration of solutes in two fluids.

Question 16

What is isontonic?

Answer 16

When extracellular and intracellular solute concentrations are equal and there is no net movement of water.

Question 17

What are 3 types of tonicity?

Answer 17

1. Hypertonic
2. Hypotonic
3. Isotonic

Question 18

What is hypertonic?

Answer 18

When the concentration of solutes outside a cell is higher than inside the cell. It causes the cell to shrink.

Question 19

What is hypotonic?

Answer 19

When the concentration of solutes outside a cell is lower than inside the cell. It causes the cell to swell.

Question 20

What are aquaporins?

Answer 20

Specialized channels for water in cell membrane that facilitate osmosis.

Question 21

Is energy required for passive transport?

Answer 21

no.

Question 22

What are 3 ways that diffusion can occur?

Answer 22

1. Directly through the lipid bilayer
2. Through protein channels
3. Through facilitated transport

Question 23

What are 2 types of proteins that can be involved in facilitated transport?

Answer 23

1. Channel proteins
2. Carrier proteins

Question 24

What are three conditions that determine the direction that molecules move through channel proteins?

Answer 24

1. Concentration on either side of the membrane
2. Voltage differences across membrane
3. whether the gated channel is open or closed

Question 25

Are carrier proteins specific or nonspecific?

Answer 25

They are specific to the molecule they transport and bind to it.

Question 26

Does active transport require energy?

Answer 26

yes.

Question 27

Does passive transport move molecules to where there is higher concentration or lower concentration?

Answer 27

Lower concentration.

Question 28

Does active transport move molecules to where there is higher concentration or lower concentration?

Answer 28

Higher concentration.

Question 29

What is an example of active transport?

Answer 29

Sodium-potassium pump.

Question 30

What are 2 types of bulk transport?

Answer 30

1. Endocytosis
2. Exocytosis

Question 31

What is endocytosis?

Answer 31

It brings substances into a cell by surrounding it in a membrane bound vesicle.

Question 32

What is exocytosis?

Answer 32

It expels substances from the cell by surrounding it with a membrane bound vesicle and fusing to the membrane.

Question 33

How is information transferred through a plasma membrane?

Answer 33

Receptor proteins span membrane and transfers information.