Mock: Biological Molecules PT 1 Flashcards
Pre 2015 wrong qs from this topic
Why is sucrose classified as a carbohydrate?
Made of carbon, hydrogen and oxygen
INA 2:1 RATIO
How are proteins suited for their roles as receptor molecules?
DIFFERENT SEQUENCE of AAs
Thus different 3 structures
With binding sites onto which a substrate can fit
Why do glucose and maltose taste sweet, but not starch
Starch’s insoluble
Why do saccharin, cyclamates and sucrose who are chemically different all taste sweet?
SIMILAR MOLECULAR SHAPE
Thus all bind to same receptors
Why immobilise lactase in a reaction?
Allows continuous reaction
Why is it necessary to pass milk through a reactor with lactase several times to reduce lactose amounts sufficiently?
↓temp
↓k.e.
↓ collisions w/ enzymes
Explain enzyme graph w/ decreasing substrate over time (2 marks)
Fewer substrate molecules
↓ chance of ES complex forming
Acid can be used to hydrolyse starch instead of alpha amylase, but it wasn’t. Why?
Alters pH
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
Quantitative result given
Specific to glucose
How would you use the Benedict’s test to compare amount of reducing sugar in two solutions?
USE SAME TEST ON BOTH SOLUTIONS
With colorimeter, compare colour
Explain why, unlike triglycerides, proteins are polymers
Triglyceride: 1X glycerol, 3X F.As
PROTEINS ARE POLYMERS OF AAs
Explain how many different sorts of proteins can be made but only one sort of glycogen?
Different sorts of AAs
One sort of glucose
Describe how molecular shape is important in explaining the way in which enzymes may be affected by inhibitors (6 marks)
4 points…
- Substrate molecules fit into active sites (1 mark) with particular shapes (1 mark)
- The change in the active site’s shape as they bind is the induced fit model of enzyme action (1 mark)
- There are two types of inhibition: competitive and non-competitive (1 mark)
- Competitive inhibitors have a similar shape to the substrate (1 mark)
- Non-competitive fit at site other than active site (1 mark)
Describe test for lipids
Dissolve food sample in ethanol THEN ADD WATER
White emulsion = +ve test for lipids
Artificial membranes consist of phospholipid bilayers only. How come only plasma membranes allow glucose to pass through them?
Glucose is transported by proteins
BUT ARTIFICIAL MEMBRANE ONLY ALLOWS PASSAGE OF LIPID SOLUBLE MATERIALS THROUGH
Give chemical formula of amine group
NH2
What is the molecular formula of lactose?
C12 H22 O11
What would you expect to see if a buret test gave a +ve result?
Purple
How do AAs differ in structure form one another?
R-groups
How does heat affect the 3 structure of a protein
3 bonds break
Denaturing protein
Suggest why an LDL will only attach to certain areas on the plasma membrane of a cell
Only parts of membrane have appropriate receptors
How would you us e Benedict’s solution to show that a ripe banana contained more reducing sugar than an unripe one
Banana + solution then heat
↑ reducing sugar = ↑ red precipitate
STANDARDISE TEST
Explain what causes the water potential of the bona pulp to decrease as the fruit ripens?
More sugar
So concentration of water lower
What causes starch hydrolysis to be slow in chilled bananas
Enzyme controlled reaction
↓ temp = ↓ KE
Fewer ES complexes formed
How many oxygen molecules are there in a molecule of galactose?
6
One advantage of milk-producing cells containing large numbers of mitochondria?
Active transport
What is hydroxylation
Addition of hydroxyl group
Breakdown of chitin leads to “death by osmosis” of fungi attacking the grain (lines 6 - 7). Explain how.
Water enters fungus (by osmosis); which increases pressure inside fungus
Cell wall no longer strong enough to withstand this
How can protein engineering make enzymes more stable and less prone to heat denaturation
Change the AAs
To make more disulphide bridges
Describe how the sequence of amino acids in proteins could enable this protein to act as an enzyme inhibitor. (6 marks)
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);
How do sulphur-containing amino acids help to give keratin molecules their characteristic strength
Chemical bonds formed between sulphur-containing groups R-groups
Stronger bonds
Why do differences in primary structure result in keratins w/ different properties?
DIFFERENT SEQUENCE OF AAs
Diff. shape
Why doesn’t the skin actively transport toxins
Skin cells dead
No respiration
No necessary proteins
How is it possible for diff proteins to have the same relative formula mass
Diff sequence of bases
50% of fatty acids are unsaturated- why is this an advantage to the body?
Triglycerides are oils
Preventing hard layer of fat forming under skin
Explain how the structure of fibrous proteins is related to their function
- Long AA chains
- Folded into pleated sheets
- Several polypeptides chains bonded together
- Forms fibres as there’s hydrogen bonding between parallel chains
- This provides strength
Why does the concentration of sugars increase as cylinder roots are further chopped up
Cutting releases sugar
B/c ↑ S.A. from which it can be released
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.
Polysaccharide broken down
To transport sugar to new shoots for growth
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.
↓ Ea
Molecules brought close together
Substrate fits into active site, straining bonds
What is the biochemical test that identifies starch
Iodine solution
Blue/black colour
Is galactose a reducing sugar
Yes
With more precipitate
How do “far apart” AAs get held close together within he active site of an enzyme
AAs for 3 structure
Held w/ disulphide bridges
Name a digestive enzyme, other than lactase, that is located in the plasma membrane of cells lining the ileum
Dipeptidase
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
No ATP formed
So no active transport of galactose
Describe the role played by the RER in the formation of chylomicrons
Protein synthesis
therefore vesicle formation
How do chylomicrons lead the epithelial cells and thus why
Exocytosis
B/c too big for other molecules
Two clear areas were observed in two agar petri dishes, A & B
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
Describe how sugars are absorbed form the ileum into the blood of a mammal
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)
Describe how maltose in the small intestine is digested, absorbed and transported to the liver as glucose (7 marks)
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
Describe how carbohydrate eaten as starch is digested to produce glucose (4 marks)
Starch digested to maltose by amylase;
Found in saliva;
Maltase converts maltose to glucose;
Found in membranes of cells lining small intestine;
Describe and explain the roles of diffusion, facilitated diffusion and active transport in the absorption of digested food by the ileum
- movement along / down concentration gradient; monoglycerides / micelles/fatty acids move into epithelial cells;
- movement along / down concentration gradient;
amino acids move into epithelial cells; - movement against concentration gradient;
reference to co-diffusion e.g. glucose and NaCl
During cell fractionation why is the tissue placed in an isotonic solution
Stops osmotic effects
Why would blood glucose concentration stay constant in a lactose intolerant man
No lactase
No digestion
No glucose absorption so blood conc. same
How is starch broken down in the digestive system (5 marks)
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]
Mitochondria in muscle cells have more cristae than mitochondria in skin cells. Explain the advantage of mitochondria in muscle cells having more cristae.
More enzymes for ATP production /oxidative phosphorylation;
Muscle cells use more ATP
