Plasma membrane

Question 1

What is the plasma membrane?

Answer 1

The plasma membrane is the active boundary of a cells.

Question 2

Describe the structure of the plasma membrane.

Answer 2

2D fluid composed of a phospholipid bilayer with embedded proteins.

Question 3

What force allows phospholipids to move freely?

Answer 3

Weak dispersion forces allows the phospholipids to move freely, like a fluid.

Question 4

Describe structure of phospholipid. (4)

Answer 4

• phosphate head: hydrophilic (polar)

- Fatty acid tail: hydrophobic tail (non polar)

Question 5

What is the difference between the two hydrophobic tails in a phospholipid?

Answer 5

One is saturated (single bonds) and one is unsaturated (double bond present)

Question 6

What is a glycocalyx?

Answer 6

Coating of outer layer of PM with carbohydrate chains.

Gives cell identity by contributing to communication, cell to cell recognition, adhesion and protects from damage.

Question 7

What are the two types of proteins found in plasma membrane?

Answer 7

• intergral: embedded into membrane, penetrate hydrophobic region
• peripheral: anchored to exterior, don’t penetrate hydrophobic region

Question 8

What are the functions of the plasma membrane? (4)

Answer 8

• protective boundary providing selective permeability
• separates internal contents from external contents of cell
• glycoproteins allow for cell identity
• communicates and interacts with external environment and other cells to maintain and balance internal conditions

Question 9

Want is the function of cholesterol in the plasma membrane?

Answer 9

Stabilises the plasma membrane by loosening membrane and reducing movement.
Assists with temp fluctuations.

Question 10

What are the functions of peripheral proteins? (2)

Answer 10

• cellular communication

- ancor cells

Question 11

What are the functions of integral proteins? (3)

Answer 11

• transport of materials across PM
• regulate movement of substance
• performs functions in and out of the cell

Question 12

What are the 4 types of proteins found in the plasma membrane?

Answer 12

• receptor
• recognition
• transport
• adhesion

Question 13

What are lipids responsible for in the plasma membrane? (4)

Answer 13

• flexibility
• repair
• shape change
  growth

Question 14

What factors allow some substances to cross the PM? (4)

Answer 14

• size
• charge
• solubility in lipid solvents (polarity)
• direction of concentration gradient

Question 15

What is simple diffusion?

Answer 15

Movement of a substance from an area of high conc. to an area of low conc.

Question 16

What are the features of simple diffusion? (3)

Answer 16

• does not require an input of energy
• moves with conc. gradient
• crosses directly through the plasma membrane

Question 17

What substances can cross the plasma membrane via simple diffusion?

Answer 17

O2(g)

CO2(g)

Question 18

What is osmosis?

Answer 18

The passive net movement of water fro an area of high water conc. to an area of low water conc. across a semipermeable membrane.

Question 19

What are the features of osmosis? (3)

Answer 19

• does not require energy
• moves with conc. gradient
• often uses aqua porin

Question 20

What 3 terms can describe the comparison between a cell and its external environment?

Answer 20

• hypotonic
• isotonic
• isotonic

Question 21

What is a hypotonic solution?

Answer 21

When there is a lower conc. of solute outside the cell.

Water will move into cell.

Question 22

What is a hypertonic solution?

Answer 22

When there is a higher conc. of solute inside of the cel rather than out.
Water will move out of the cell.

Question 23

What is an isotonic solution?

Answer 23

When there is an equal solute conc. in and out of the cell.

Question 24

How does a hypotonic solution affect a plant and animal cell?

Answer 24

• animal: burst

- plant: swell becoming turgid

Question 25

How does a hypertonic solution affect a plant and animal cell?

Answer 25

- animal: shinks | - plant: shrivels away from cell wall

Question 26

What is facilitated diffusion?

Answer 26

Passive net movement of a substance from an area of high conc. to an area of low conc. via a protein channel/ carrier.

Question 27

What are the features of facilitated diffusion?

Answer 27

- protein mediated transport - does not require energy - moves with conc. gradient

Question 28

How do the rates of diffusion of facilitated and simple diffusion compare?

Answer 28

- simple: linear, always room for molecules to move across - facilitated: begins fast as there are many channels available, eventually plateaus due to all channels being occupied and no more molecules can be transported until they're unoccupied

Question 29

What substances can cross the plasma membrane via facilitated diffusion?

Answer 29

- glucose

Question 30

What is active transport?

Answer 30

The active net movement of a substance from an area of low conc. to an area of high conc.

Question 31

What are the features of active transport?

Answer 31

- requires an input of energy - goes against conc. gradient - requires a protein pump

Question 32

What are the types of bulk transport?

Answer 32

- exocytosis - endocytosis - pinocytosis - phagocytosis - receptor mediated transport

Question 33

Define exocytosis.

Answer 33

Materials exported out of the cell via secretory vessels.

Question 34

Define endocytosis?

Answer 34

Materials transported into the cell via three ways.

Question 35

Define pinocystosis.

Answer 35

When a fluid is transported in the cell

Question 36

Define phagocytosis.

Answer 36

When macromolecules are transported into the cell.

Question 37

Define receptor mediated transport.

Answer 37

A trigger has to occur before a receptor will assist the entry of material into a cell.

Question 38

What factors effect permeability?

Answer 38

- temperature: denatures protein or speeds up molecules - SA:V: higher SA:V increases rate of dissuasion - PH: - ethanol: dissolves the lipid components of the membrane.