Plasma Membrane and Organelles

Question 1

5 functions of a cell

Answer 1

1. manufacture cellular materials
2. obtain raw materials
3. remove waste
4. generate the required energy
5. control all of the above

Question 2

plasma membrane

Answer 2

semi-permeable, lipid bilayer barrier that separates the cell from the outside and controls the movement of substances in and out of the cell

Question 3

3 factors that influence the plasma membrane and how

Answer 3

1. Saturation
   - saturated: packed tightly together and less fluidity
   - unsaturated: tails prevent tight packing and more fluidity
2. Temperature
   - high temp = more fluidity
   - low temp = less fluidity
3. Cholesterol
   - stabilises membrane fluidity

Question 4

5 plasma membrane protein functions

Answer 4

1. signal transduction: relay messages from the body (or environment) into the cell
2. cell recognition: often involves glycoproteins
3. intercellular joining: some proteins from long lasting connections between cells
4. linking cytoskeleton and extracellular matrix: allows the cell to physically connect with protein structures outside the cell
5. membrane transport: allows small amounts of molecules to move across the membrane

Question 5

passive transport

Answer 5

no energy is needed as molecules move down the concentration gradient

Question 6

active transport

Answer 6

energy is needed as molecules are forced to move against their concentration gradient

Question 6

diffusion through the cellular membrane

Answer 6

membranes are permeable to lipid soluble (hydrophobic) molecules and require no energy as they move down their concentration gradient

Question 7

facilitated diffusion through the cellular membrane

Answer 7

movement of hydrophilic molecules require membrane proteins (channels and carriers) to aid the movement of specific substance across the membrane, down their concentration gradient (still requires no energy)

Question 8

osmosis through the cellular membrane

Answer 8

movement of water across the membrane through channels called aquaporins, down their concentration gradient

Question 9

why do cells osmoregulate

Answer 9

to prevent swelling or shrinking under varying conditions

Question 10

why do cells use active transport

Answer 10

allows the cell to have an internal concentration of a substance that is different from its surroundings

Question 11

co-transport through the cellular membrane

Answer 11

one substance is pumped across the membrane (using membrane proteins) and its concentration gradient is used to power the movement of a second substance against its concentration gradient

Question 12

why do organelles have membranes (5)

Answer 12

1. provide special conditions for specific processes
2. keep incompatible processes apart
3. allow specific substances to be concentrated
4. form concentration gradient
5. package substances for transport or export