Plasma membrane LO2

Question 1

The plasma membrane

Answer 1

• selectively permeable: allows certain substances to pass
  while restricting the movement of others

Question 2

Phospholipid bilayer

Answer 2

• phosphate heads - hydrophilic (“love water”)
• lipid tails - hydrophobic (“hate water”)

Question 3

peripheral proteins

Answer 3

not embedded throughout the plasma membrane
- attach loosely to integral proteins or float free
- function: plasma membrane support, enzymes or motor functions

Question 4

Integral proteins:

Answer 4

embedded within the membrane and span entire membrane
- substance specific
- act as enzymes or receptors

Question 5

Channel proteins

Answer 5

Leakage channels
- always open at both ends
- substances that use channel proteins: water, Na+ and K+
Gated channels
- open at one end and can open and close at the other end
3 types of gated channel
- voltage gated
- chemically gated
- mechanically gated
- substances that use: ions Na+, K+ & Ca2+

Question 6

Carrier Proteins

Answer 6

transform shape to allow substances to pass
Include: lipid insoluble
substances or substances too large to use channel proteins

Question 7

Diffusion

Answer 7

the movement of substance from an area of high concentration to an area of low concentration (down / along / with concentration gradient)
substances move in a net direction to achieve equilibrium

Question 8

Factors that affect rate of movement

Answer 8

1. concentration gradient: the larger the concentration gradient the faster the substances will move
2. size of the substance: smaller substances move faster than larger
   substances
3. temperature: warmer environments increase the rate of movement

Question 9

Passive transport

Answer 9

• concentration gradient
• requires no energy
• includes simple diffusion,
  facilitated diffusion and osmosis

Question 10

Active transport

Answer 10

• substances move up
  concentration gradient
• requires ATP
• includes primary active
  transport with Na+
  /K+ ATPase pump

Question 11

Simple Diffusion

Answer 11

the unassisted transport of lipid soluble or very small
substances, across a plasma membrane, down its
concentration gradient

Question 12

Facilitated Diffusion

Answer 12

the assisted transport of large or lipid insoluble substances,
from an area of high concentration to low concentration, across
a plasma membrane, using an integral protein

Question 13

Osmosis

Answer 13

• osmosis is the movement of water (solvent) across the
  plasma membrane
• water molecules move down concentration gradient, from an area of high water concentration to low water concentrtion
• can move directly though the phospholipid bilayer

Question 14

Exocytosis and Endocytosis

Answer 14

• exocytosis – out of the cell
• endocytosis – into
  the cell

Question 15

Tonicity

Answer 15

• is the ability of a solution (fluid outside the cell) to affect the shape of a cell
  by altering the cells internal water volume (ICF)
• the tonicity of the solution that surrounds the cell is determined by its
  concentration relative to ICF

Question 16

Tonicity: Isotonic

Answer 16

the same concentration as the ICF for both:
- substances/solutes
- water
- isotonic solutions cause no change in cell volume or shape (no water shift)

Question 17

Tonicity: Hypertonic

Answer 17

• higher concentration of impermeable solutes
  than the ICF …therefore a lower amount of water than the cell
• cells in a hypertonic solution will lose
  water → shrink (crenate)

Question 18

Tonicity: Hypotonic

Answer 18

• lower concentration of impermeable solutes
  than the ICF …therefore a higher amount of water than the cell
• cells in a hypotonic solution will gain
  water → swell → burst or lyse