ISA

Question 1

The dialysis tubing represented the phospholipid bilayer. What are the problems with this?

Answer 1

No proteins

Not a double layer

No cholesterol

No fluid

Question 2

Why did iodine diffuse, not starch?

Answer 2

Iodine is smaller - fits through pores of membrane - DIFFUSES through tubing

Starch too large

Question 3

What factors affect diffusion across the bilayer?

Answer 3

Lipid solubility

Charge

Shape - may require a carrier/channel protein

Question 4

Why did we have to wash the dialysis tubing?

Answer 4

To ensure there was no starch on the outside of the tubing - would react immediately with iodine - solution would turn blue/black quicker

Question 5

What factors affect diffusion?

Answer 5

Concentration gradient

Temperature - we remained in same environment

Length of diffusion pathway - used same dialysis tubing

Surface area

Question 6

Why did the time taken for the solution to turn blue/black change?

Answer 6

The concentration of iodine solution changed - the bigger the gradient the faster diffusion - the more iodine diffuses the more reacts with starch so the faster the solution turns blue/black.

Question 7

How did we keep the same perspective of the cross disappearing?

Answer 7

Had the same background

Eye level

Question 8

Why would you leave things for the same amount of time?

Answer 8

For comparison purposes - to compare X AND Y

Question 9

Describe starch

Answer 9

Insoluble - a storage molecule

Hydrolysed by amylose to glucose/sugars

Predominantly found in plants:

Insoluble so no osmotic effect

Doesn’t easily diffuse out of cells

Coiled so is compact

Branched so easily hydrolysed

Question 10

What happens when starch is hydrolysed?

Answer 10

Tastes sweet

The more hydrolysis the sweeter it will be

More hydrolysis - less starch - less colour change when iodine added

Question 11

As fruit ripens it gets softer due to more sugars. It may also rot/go mouldy if lots of sugars. What does this mean?

Answer 11

Don’t want full of starch - not sweet enough

Don’t want full of sugar - too sweet/soft

Need balance - need right time to stop reaction so the fruit is sellable

REFER TO NUMBERS/FIGURES

Question 12

How do you calculate percentage difference?

Answer 12

Difference/original x 100

Question 13

What is standard deviation?

Answer 13

Value + or - SD

Question 14

An example of SD is 1 + or - 2. (People). What does this show?

Answer 14

More spread above mean than below - 0-3

Sometimes no people

Question 15

You want to make a 10ml solution in total. If you want a 50% solution how do you calculate water and iodine amount?

Answer 15

Iodine - 5 cm3 (50% of total)

Water - 5cm3

Question 16

You want to make a 10ml solution in total. If you want a 5% solution how do you calculate water and iodine amount?

Answer 16

Iodine - 0.5cm3 (5% of total)

Water - 9.5cm3

Question 17

How do pathogens affect the body?

Answer 17

Attack/damage cells

Produce toxins

Question 18

Summarise the phospholipid bilayer

Answer 18

Hydrophobic tails of both layers point in, hydrophilic heads point out

Allow lipid soluble substances to enter/leave cell

Prevents water soluble substances entering/leaving cell

Makes membrane flexible

Proteins - provide structural support and act as carriers

Cholesterol - more cholesterol - less fluid - less permeable