Topic 2 Practicals

Question 1

Beetroot Practical: How would you keep temperature constant when you are investigating the effect of ethanol concentration on membranes? State a suitable temp.

Answer 1

Using a water bath at room temperatures (0-20)

Question 2

Beetroot Practical: State and justify a control, when investigating the effect of ethanol concentration of membrane permeability.

Answer 2

Use a solution with 0% ethanol, water, for comparison

Question 3

Beetroot Practical: How many repeats should be carried out when investigating the effect of temperature on membrane permeability? What should be repeated?

Answer 3

At least 5 per temperature

Question 4

Beetroot Practical: How can pH be controlled during the beetroot practical?

Answer 4

using a buffer solution

Question 5

Beetroot Practical: Name a suitable control when investigating the effect of temperature on membrane permeability

Answer 5

Room temperature solution with set pH using a buffer

Question 6

Beetroot Practical: Give control variables for the beetroot pieces that are used in the practical?

Answer 6

• size, surface area
• species
• same plant
• part of beetroot
• storage conditions
• age

Question 7

Beetroot Practical: What is the pigment that beetroot contains?

Answer 7

betalains

found in call vacuole

Question 8

Beetroot Practical: Explain membrane permeability below 0*c

Answer 8

• low kinetic energy so less movement of betalians
• phospholipids have low energy so are rigid
• water inside the cell will freeze and expand. this puts pressure on the membrane.
• frozen ice crystals may pierce the membrane
• membrane is very permeable when thawed

Question 9

Beetroot Practical: Explain membrane permeability between 0c and 45c

Answer 9

• phospholipids can move and aren’t packed as tightly so membrane is partially permeable
• as temp increases the phospholipids will move more and increase the membrane permeability

Question 10

Beetroot Practical: Explain membrane permeability above 45*c

Answer 10

• phospholipids start to melt so membrane becomes more permeable
• water expands, putting pressure on the cell membrane
  -Channel proteins denature so can’t control what enters and leaves the cell
• increased membrane permeability

Question 11

Beetroot Practical: What effect does alcohol concentration have on membrane permeability? Why?

Answer 11

an increase in alcohol concentration will increase membrane permeability as alcohol will dissolve the the lipids in the membrane causing the membrane to lose its structure

Question 12

Beetroot Practical: What does abs mean?

Answer 12

absorbance

Question 13

Beetroot Practical: What is the absorbance wavelength for betalains?

Answer 13

Abs 490 nm - green
this is the opposite of the red betalains

Question 14

Beetroot Practical: What equipment is needed?

Answer 14

• colorimeter with cuvettes
• boiling tubes
• stop clock
• pipettes

Question 15

Beetroot Practical: Name suitable procedural variable that should be controlled

Answer 15

• volume of liquid
• incubation time

Question 16

Beetroot Practical: What is the independent variable?

Answer 16

Temperature or alcohol conc.

Question 17

Beetroot Practical: What is the dependent variable?

Answer 17

The absorbance of 490nm
- membrane permeability

Question 18

Enzyme Practical: If you were investigating the effect of enzyme concentration on protein hydrolysis, how many different enzyme concentrations should you use?

Answer 18

at least 5 plus a control

Question 19

Enzyme Practical: If you were investigating the effect of enzyme concentration on protein hydrolysis, what should be repeated and how many repeats should be carried out?

Answer 19

Repeat at least 5 times for each different enzyme concentration

Question 20

Enzyme practical: What enzyme is used?

Answer 20

Trypsin

Question 21

Enzyme practical: What substrate is used?

Answer 21

Casein

Question 22

Enzyme practical: What absorbance is used?

Answer 22

440nm

Question 23

Enzyme practical: How are the trypsin solutions made?

Answer 23

Serial dilution