Mock: Biological Molecules PT 1

Question 1

Why is sucrose classified as a carbohydrate?

Answer 1

Made of carbon, hydrogen and oxygen

INA 2:1 RATIO

Question 2

How are proteins suited for their roles as receptor molecules?

Answer 2

DIFFERENT SEQUENCE of AAs
Thus different 3 structures
With binding sites onto which a substrate can fit

Question 3

Why do glucose and maltose taste sweet, but not starch

Answer 3

Starch’s insoluble

Question 4

Why do saccharin, cyclamates and sucrose who are chemically different all taste sweet?

Answer 4

SIMILAR MOLECULAR SHAPE

Thus all bind to same receptors

Question 5

Why immobilise lactase in a reaction?

Answer 5

Allows continuous reaction

Question 6

Why is it necessary to pass milk through a reactor with lactase several times to reduce lactose amounts sufficiently?

Answer 6

↓temp
↓k.e.
↓ collisions w/ enzymes

Question 7

Explain enzyme graph w/ decreasing substrate over time (2 marks)

Answer 7

Fewer substrate molecules

↓ chance of ES complex forming

Question 8

Acid can be used to hydrolyse starch instead of alpha amylase, but it wasn’t. Why?

Answer 8

Alters pH

Question 9

Suggest 2 reasons why a test for glucose in urine based on glucose oxidase and peroxidase might be preferred to one using Benedict’s reagent

Answer 9

Quantitative result given

Specific to glucose

Question 10

How would you use the Benedict’s test to compare amount of reducing sugar in two solutions?

Answer 10

USE SAME TEST ON BOTH SOLUTIONS

With colorimeter, compare colour

Question 11

Explain why, unlike triglycerides, proteins are polymers

Answer 11

Triglyceride: 1X glycerol, 3X F.As

PROTEINS ARE POLYMERS OF AAs

Question 12

Explain how many different sorts of proteins can be made but only one sort of glycogen?

Answer 12

Different sorts of AAs

One sort of glucose

Question 13

Describe how molecular shape is important in explaining the way in which enzymes may be affected by inhibitors (6 marks)
4 points…

Answer 13

1. Substrate molecules fit into active sites (1 mark) with particular shapes (1 mark)
2. The change in the active site’s shape as they bind is the induced fit model of enzyme action (1 mark)
3. There are two types of inhibition: competitive and non-competitive (1 mark)
4. Competitive inhibitors have a similar shape to the substrate (1 mark)
5. Non-competitive fit at site other than active site (1 mark)

Question 14

Describe test for lipids

Answer 14

Dissolve food sample in ethanol THEN ADD WATER

White emulsion = +ve test for lipids

Question 15

Artificial membranes consist of phospholipid bilayers only. How come only plasma membranes allow glucose to pass through them?

Answer 15

Glucose is transported by proteins

BUT ARTIFICIAL MEMBRANE ONLY ALLOWS PASSAGE OF LIPID SOLUBLE MATERIALS THROUGH

Question 16

Give chemical formula of amine group

Answer 16

NH2

Question 17

What is the molecular formula of lactose?

Answer 17

C12 H22 O11

Question 18

What would you expect to see if a buret test gave a +ve result?

Answer 18

Purple

Question 19

How do AAs differ in structure form one another?

Answer 19

R-groups

Question 20

How does heat affect the 3 structure of a protein

Answer 20

3 bonds break

Denaturing protein

Question 21

Suggest why an LDL will only attach to certain areas on the plasma membrane of a cell

Answer 21

Only parts of membrane have appropriate receptors

Question 22

How would you us e Benedict’s solution to show that a ripe banana contained more reducing sugar than an unripe one

Answer 22

Banana + solution then heat
↑ reducing sugar = ↑ red precipitate
STANDARDISE TEST

Question 23

Explain what causes the water potential of the bona pulp to decrease as the fruit ripens?

Answer 23

More sugar

So concentration of water lower

Question 24

What causes starch hydrolysis to be slow in chilled bananas

Answer 24

Enzyme controlled reaction
↓ temp = ↓ KE
Fewer ES complexes formed

Question 25

How many oxygen molecules are there in a molecule of galactose?

Answer 25

6

Question 26

One advantage of milk-producing cells containing large numbers of mitochondria?

Answer 26

Active transport

Question 27

What is hydroxylation

Answer 27

Addition of hydroxyl group

Question 28

Breakdown of chitin leads to “death by osmosis” of fungi attacking the grain (lines 6 - 7). Explain how.

Answer 28

Water enters fungus (by osmosis); which increases pressure inside fungus Cell wall no longer strong enough to withstand this

Question 29

How can protein engineering make enzymes more stable and less prone to heat denaturation

Answer 29

Change the AAs | To make more disulphide bridges

Question 30

Describe how the sequence of amino acids in proteins could enable this protein to act as an enzyme inhibitor. (6 marks)

Answer 30

``` Shape of tertiary structure Is similar shape to substrate; Competes for active site; or Fits at site other than active site; Distorting active site; Therefore substrate will not fit (active site); ```

Question 31

How do sulphur-containing amino acids help to give keratin molecules their characteristic strength

Answer 31

Chemical bonds formed between sulphur-containing groups R-groups Stronger bonds

Question 32

Why do differences in primary structure result in keratins w/ different properties?

Answer 32

DIFFERENT SEQUENCE OF AAs | Diff. shape

Question 33

Why doesn't the skin actively transport toxins

Answer 33

Skin cells dead No respiration No necessary proteins

Question 34

How is it possible for diff proteins to have the same relative formula mass

Answer 34

Diff sequence of bases

Question 35

50% of fatty acids are unsaturated- why is this an advantage to the body?

Answer 35

Triglycerides are oils | Preventing hard layer of fat forming under skin

Question 36

Explain how the structure of fibrous proteins is related to their function

Answer 36

1. Long AA chains 2. Folded into pleated sheets 3. Several polypeptides chains bonded together 4. Forms fibres as there's hydrogen bonding between parallel chains 5. This provides strength

Question 37

Why does the concentration of sugars increase as cylinder roots are further chopped up

Answer 37

Cutting releases sugar | B/c ↑ S.A. from which it can be released

Question 38

In autumn the shoots of the plants die, leaving the root as a storage organ in the soil. New shoots grow from the storage organ in spring. When the storage organs were tested after the shoots had died in late autumn, they were found to contain large amounts of storage polysaccharide and very little reducing sugar. When tested in spring as the new shoots were developing, much higher concentrations of reducing sugar were found. Suggest an explanation for the high concentration of reducing sugar in the spring.

Answer 38

Polysaccharide broken down | To transport sugar to new shoots for growth

Question 39

Many reactions take place in living cells at temperatures far lower than those required for the same reactions in a laboratory. Explain how enzymes enable this to happen.

Answer 39

↓ Ea Molecules brought close together Substrate fits into active site, straining bonds

Question 40

What is the biochemical test that identifies starch

Answer 40

Iodine solution | Blue/black colour

Question 41

Is galactose a reducing sugar

Answer 41

Yes | With more precipitate

Question 42

How do "far apart" AAs get held close together within he active site of an enzyme

Answer 42

AAs for 3 structure | Held w/ disulphide bridges

Question 43

Name a digestive enzyme, other than lactase, that is located in the plasma membrane of cells lining the ileum

Answer 43

Dipeptidase

Question 44

The absorption of galactose from the small intestine is reduced if the absorbing cells are treated with a respiratory inhibitor, e.g. cyanide. Suggest an explanation for this

Answer 44

No ATP formed | So no active transport of galactose

Question 45

Describe the role played by the RER in the formation of chylomicrons

Answer 45

Protein synthesis | therefore vesicle formation

Question 46

How do chylomicrons lead the epithelial cells and thus why

Answer 46

Exocytosis | B/c too big for other molecules

Question 47

Two clear areas were observed in two agar petri dishes, A & B

Answer 47

Enzymes secreted; Reference to diffusion (of enzyme into agar); Starch digested; Into maltose/glucose; Smaller molecules absorbed into fungus So B must have greater production of enzyme/more active enzyme

Question 48

Describe how sugars are absorbed form the ileum into the blood of a mammal

Answer 48

Thin epithelium; So short diffusion pathway; Capillary network absorbs amino acids / sugars; Lacteal for absorption of digested fats; Mitochondria supply ATP / energy for active transport; carrier proteins (in membranes)

Question 49

Describe how maltose in the small intestine is digested, absorbed and transported to the liver as glucose (7 marks)

Answer 49

Maltase enzymes in membranes of epithelial cells of small intestine Maltase hydrolyses maltose Glucose absorbed via diffusion In association with uptake of sodium ions Involving active transport And carrier molecules Aided by villi which increases surface area for the carrier molecules

Question 50

Describe how carbohydrate eaten as starch is digested to produce glucose (4 marks)

Answer 50

Starch digested to maltose by amylase; Found in saliva; Maltase converts maltose to glucose; Found in membranes of cells lining small intestine;

Question 51

Describe and explain the roles of diffusion, facilitated diffusion and active transport in the absorption of digested food by the ileum

Answer 51

1. movement along / down concentration gradient; monoglycerides / micelles/fatty acids move into epithelial cells; 2. movement along / down concentration gradient; amino acids move into epithelial cells; 3. movement against concentration gradient; reference to co-diffusion e.g. glucose and NaCl

Question 52

During cell fractionation why is the tissue placed in an isotonic solution

Answer 52

Stops osmotic effects

Question 53

Why would blood glucose concentration stay constant in a lactose intolerant man

Answer 53

No lactase No digestion No glucose absorption so blood conc. same

Question 54

How is starch broken down in the digestive system (5 marks)

Answer 54

Amylase (1 mark) hydrolyses (1 mark) starch into to maltose(1 mark) Maltase (1 mark) hydrolyses maltose to glucose (1 mark) [Both enzymes hydrolyse glycosidic bonds]

Question 55

Mitochondria in muscle cells have more cristae than mitochondria in skin cells. Explain the advantage of mitochondria in muscle cells having more cristae.

Answer 55

More enzymes for ATP production /oxidative phosphorylation; | Muscle cells use more ATP