Cell Membrane and Transport

Question 1

Structure

Answer 1

trilaminar, with two layers of phospholipids and cholesterol interspersed with proteins

Question 2

phospholipid bilayer

Answer 2

consists of hydrophilic heads and hydrophobic tails

Question 3

semi-permeable membranes

Answer 3

allows some substances to pass through according to size

Question 4

simple diffusion

Answer 4

the random mixing of solute particles in a solution

Question 5

Simple diffusion

Answer 5

the flow of solute particles from high to low concentration in order to equalise concentrations

Question 6

Diffusion through a membrane

Answer 6

1. lipid soluble substances (alcohol, steroids, fatty acids, O2, CO2) move through bilipid layer - no protein involved
2. small, water-soluble substances move through membrane channels - protein channel involved (simple diffusion)

Question 7

Facilitated diffusion (passive)

Answer 7

molecules that are too large to move through protein channels bind to carrier protein
carrier protein changes shape, moving the molecule to the other side of the membrane

Question 8

Active transport

Answer 8

the movement of particles against the concentration gradient
the concentration differences are maintained/increased
active transport can be endocytosis, exocytosis, via protein carriers

Question 9

Endocytosis

Answer 9

moving materials into the cell
pinocytosis - liquids
phagocytosis - solids

Question 10

osmosis

Answer 10

movement of water molecules across a semi-permeable membrane

Question 11

Factors affecting the rate of diffusion

Answer 11

molecule size, molecule shape, concentration, charge, lipid solubility, temperature, surface are to volume ratio

Question 12

Plasma membrane

Answer 12

surrounds the cell and organelles

thin, flexible lipid and protein barrier that regulates the movement of substances into and out of the cell