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Biology Past Paper Question > Mock: Biological Molecules PT 1 > Flashcards

Mock: Biological Molecules PT 1 Flashcards

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1
Q

Why is sucrose classified as a carbohydrate?

A

Made of carbon, hydrogen and oxygen

INA 2:1 RATIO

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2
Q

How are proteins suited for their roles as receptor molecules?

A

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

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3
Q

Why do glucose and maltose taste sweet, but not starch

A

Starch’s insoluble

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4
Q

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

A

SIMILAR MOLECULAR SHAPE

Thus all bind to same receptors

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5
Q

Why immobilise lactase in a reaction?

A

Allows continuous reaction

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6
Q

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

A

↓temp
↓k.e.
↓ collisions w/ enzymes

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7
Q

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

A

Fewer substrate molecules

↓ chance of ES complex forming

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8
Q

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

A

Alters pH

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9
Q

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

A

Quantitative result given

Specific to glucose

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10
Q

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

A

USE SAME TEST ON BOTH SOLUTIONS

With colorimeter, compare colour

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11
Q

Explain why, unlike triglycerides, proteins are polymers

A

Triglyceride: 1X glycerol, 3X F.As

PROTEINS ARE POLYMERS OF AAs

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12
Q

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

A

Different sorts of AAs

One sort of glucose

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13
Q

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

A
  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)
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14
Q

Describe test for lipids

A

Dissolve food sample in ethanol THEN ADD WATER

White emulsion = +ve test for lipids

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15
Q

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

A

Glucose is transported by proteins

BUT ARTIFICIAL MEMBRANE ONLY ALLOWS PASSAGE OF LIPID SOLUBLE MATERIALS THROUGH

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16
Q

Give chemical formula of amine group

A

NH2

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17
Q

What is the molecular formula of lactose?

A

C12 H22 O11

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18
Q

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

A

Purple

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19
Q

How do AAs differ in structure form one another?

A

R-groups

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20
Q

How does heat affect the 3 structure of a protein

A

3 bonds break

Denaturing protein

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21
Q

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

A

Only parts of membrane have appropriate receptors

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22
Q

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

A

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

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23
Q

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

A

More sugar

So concentration of water lower

24
Q

What causes starch hydrolysis to be slow in chilled bananas

A

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

25
Q

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

A

6

26
Q

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

A

Active transport

27
Q

What is hydroxylation

A

Addition of hydroxyl group

28
Q

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

A

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

29
Q

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

A

Change the AAs

To make more disulphide bridges

30
Q

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

A 
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);
31
Q

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

A

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

32
Q

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

A

DIFFERENT SEQUENCE OF AAs

Diff. shape

33
Q

Why doesn’t the skin actively transport toxins

A

Skin cells dead
No respiration
No necessary proteins

34
Q

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

A

Diff sequence of bases

35
Q

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

A

Triglycerides are oils

Preventing hard layer of fat forming under skin

36
Q

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

A
  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
37
Q

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

A

Cutting releases sugar

B/c ↑ S.A. from which it can be released

38
Q

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.

A

Polysaccharide broken down

To transport sugar to new shoots for growth

39
Q

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.

A

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

40
Q

What is the biochemical test that identifies starch

A

Iodine solution

Blue/black colour

41
Q

Is galactose a reducing sugar

A

Yes

With more precipitate

42
Q

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

A

AAs for 3 structure

Held w/ disulphide bridges

43
Q

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

A

Dipeptidase

44
Q

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

A

No ATP formed

So no active transport of galactose

45
Q

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

A

Protein synthesis

therefore vesicle formation

46
Q

How do chylomicrons lead the epithelial cells and thus why

A

Exocytosis

B/c too big for other molecules

47
Q

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

A

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

48
Q

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

A

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)

49
Q

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

A

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

50
Q

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

A

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

51
Q

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

A
  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
52
Q

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

A

Stops osmotic effects

53
Q

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

A

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

54
Q

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

A

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]

55
Q

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

A

More enzymes for ATP production /oxidative phosphorylation;

Muscle cells use more ATP

Biology Past Paper Question (6 decks)

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