Topic 4-Exchange and transport

Question 1

Body mass and oxygen consumption

Answer 1

-Smaller animals consume more oxygen
-larger SA:V ratio
-lose more heat by respiration
-but need to maintain body temp

Question 2

Effect of temperature on membrane permeability

Answer 2

-permeability increase as temperature increase due to the kinetic energy increase of the molecule
-Phospholipids gain kinetic E leading to more movement so membrane more FLUID
-Proteins denature due to extreme temp so permeability decreases

Question 3

Requirements for active transport

Answer 3

Cell membrane, ATP, carrier protein

Question 4

Importance of phospholipids changing according to temperature

Answer 4

-membranes control permeability
-such as O2 uptake
-so they need to be fluid

Question 5

Effect of ethanol in cell membrane

Answer 5

-Disrupts phospholipid membrane
-Makes it more permeable

Question 6

Control in cell membrane practicals

Answer 6

-Same type/age/part of plant
-same core borer used
-control temp/ph
-same V of solution, conc, etc

Question 7

Diffusion of charged/uncharged particles

Answer 7

Uncharged-can diffuse through hydrophobic fatty acid tail
-Charged-facilitated diffusion

Question 8

Effect of sucrose and glucose

Answer 8

-osmotic potential of 3% sucrose is equal to 6% glucose
-As sucrose has double molecular mass
-it is the no. of molecules that determine osmotic potential

Question 9

Ψ=P+π equation

Answer 9

Water enters cell by osmosis:
-Ψ of cell <outside
-P increase until equal to π
-Ψ becomes equal to 0

Question 10

Osmotic potential-plants

Answer 10

-Can’t directly measure as it includes turgor pressure and water potential
-can only be measured through incipient plasmolysis
-which is when P=0

Question 11

Improvements in cell membrane practicals

Answer 11

-Full submerge plant in the solution so all surfaces are in contact
-control temperature
-use smaller intervals of concentration
-blot to remove excess solution
-repeat and calculate the mean excluding the anomalies

Question 12

Determining osmotic potential from a graph of conc against plasmolysis

Answer 12

1. Find conc with 50% plasmolysis
2. Use a graph to figure out

Question 13

Why are cells left for 10 mins

Answer 13

-to wait for water to move out
-so osmotic potential is accurate

Question 14

Cell membrane with charged substances

Answer 14

-polar molecules are charged
-phospholipids have hydrophilic head and hydrophobic tail
-charged particles can’t pass through tail
-so need carrier proteins

Question 15

How does membrane control movement

Answer 15

-Hydrophilic tail and hydrophobic head
-polar substances can’t pass through
-need carrier proteins