SUMMARY QUESTIONS - Biological molecules Flashcards
Large molecules often contain carbon, Explain why
Carbon atoms readily link to one another to form a chain
State the general name for a molecule that is made up of many similar repeating units
Polymer
Explain why Benedict’s reagent turns red when heated with a reducing sugar
Sugar donates electrons that reduce blue copper (II) sulfate to orange copper (I) oxide
Suggest a way, other than comparing colour changes, in which different concentrations of reducing sugar could be estimated
- Dry the precipitate in each sample and weigh it.
- the heavier the precipitate = the more reducing sugar present
Explain why it isn’t possible to distinguish between very concentrated samples, even when their concentrations are different
Once all the copper (II) sulfate has been reduced to copper (I) oxide, further amounts of reducing sugar cannot make a difference
Identify which one, or more monomer units make up each of the following carbohydrates
A: lactose
B: sucrose
C: starch
A - glucose + galactose
B - glucose + fructose
C - alpha glucose only
Glucose (C6H12O6) combines with fructose (C6H12O6) to form the disaccharide sucrose. From your knowledge of how disaccharides are formed, deduce the formula of sucrose
C12H22O11
- because: (C6H12O6) + (C6H12O6) - H20 (form removal of water to form glycosidic bond)
To hydrolyse a disaccharide it can be boiled with hydrochloric acid but if hydrolysis is carried out by an enzyme a much lower temp (40’C) is required. Explain why
Enzymes are denatured at higher temps and this prevents them functioning / enzymes lower the activation energy required
What will ‘stain blue with iodine solution’
Starch
What ‘is known as “animal starch”’
Glycogen
What saccharide is found in plants
- alpha and beta glucose
- starch
- cellulose
Fill the gap:
Fats and oils make up a group of lipids called (A) which, when hydrolysed, form (B) and fatty acids. A fatty acid with more than one carbon-carbon double bond is described as (C). In phospholipid the number of fatty acids is (D); these are described as (E) because they repel water
A - triglycerides
B - glycerol
C - polyunsaturated
D - two
E - hydrophobic
List 2 differences between a triglyceride molecule and a phospholipid molecule
- Triglyceride: 3 fatty acids / no phosphate group / nonpolar
- Phospholipids: 2 fatty acids + 1 phosphate group / hydrophilic ‘head’ and hydrophobic ‘tail’
Organisms that move, e.g. animals, and parts of organisms that move, e.g. some plant seeds, use lipids rather than carbohydrates as an energy store. Suggests one reason why
- lipids provide 2x as much energy as carbohydrate when they are oxidised
- if fat is stored, the same amount of energy can be provided for less than half the mass
- therefore its a lighter storage product — a major adv if the organism is motile
Name the type of bond that joins amino acids together
Peptide bond
State the type of reaction involved in joining amino acids together
Condensation reaction
List 4 different components that make up amino acids
- amino group (—NH2)
- carboxyl group (—COOH)
- hydrogen atom (—H)
- R group
Define a catalyst
A substance that alters the rate of a chemical reaction without undergoing permanent change
Explain why enzymes are effective in tiny quantities
They aren’t used up in the reaction and so can be used repeatedly
Outline why changing one of the amino acids that make up the active site could prevent the enzyme from functioning
The changed amino acid may no longer bind to the substrate, which will then not be positioned correctly, if at all, in the active site
Explain why changing certain amino acids that aren’t taking part of the active site also prevents the enzyme from functioning
- The changed amino acid may be one that forms hydrogen bonds with other amino acids
- if the new amino acid doesn’t form hydrogen bonds the tertiary structure of the enzyme will change, including the active site, so that the substrate nay no longer fit
Explain why enzymes function less well at lower temps
- To function, enzymes must physically collide with their substrate
- lower temps decrease the kinetic energy of both enzyme and substrate molecules, which then move around less quickly
- they hence collide less often and therefore react less frequently
Explain how high temps may completely prevent enzymes from functioning
- The heat causes hydrogen and other bonds in the enzyme molecule to break
- The tertiary structure of the enzyme molecule changes, as does the active site
- the substrate no longer fits in the active site
Enzymes produced by microorganisms are responsible for spoiling food. using this fact and your knowledge of enzymes, deduce why each of the following procedures are carried out:
A - food is heated to a high temp before being canned
B - Some foods, such as onions, are preserved in vinegar
A - High temps denature the enzymes and so they can’t spoil food
B - Vinegar is very acidic and the very low pH will denature the enzymes and so preserve the food
Calculate the pH of a solution that has a hydrogen ion concentration of 0.0001 M
- pH = 4
Different conditions affect how enzymes work. Name one that might vary between one organelle and another
- pH / substrate conc. (not temp)
Suggest why enzymes are attached to the inner membrane of an organelle ‘in a very precise sequence’
- in a metabolic pathway
- the product of 1 reaction acts as the substrate for the next reaction
- By having the enzymes in appropriate sequence there is a greater chance of each enzyme coming into contact with its substrate than if enzymes are floating freely in the organelle
- this is a more efficient means of producing the Ned product
If an end product inhibits enzyme B rather than enzyme A, predict what would be:
A - the initial effect on the concentration of intermediate 1
B- the overall longer term effect on the concentration of the end product
A - it would increase
B - it would be unchanged
Suggest one advantage of end-product inhibition being non-competitive rather than competitive. relate your answer to how the two types of inhibition take place
ADV - the level of the end product doesn’t fluctuate with changes in the level of substrate
Explanation:
- Non-competitive inhibition occurs at a site on the enzyme other than active site
- Hence its not affected by the substrate conc.
- therefore changes in level of substrate doesn’t affect the inhibition of the enzyme, nor the normal level of the end product
- If it were competitive, changes in level of substrate would affect end product molecules combining with active site, resulting in fluctuating of the degree of inhibition AND level of end product
Distinguish between a competitive and a non-competitive inhibitor
Competitive inhibitors occupy the active site of an enzyme while non-competitive inhibitors attach to the enzyme at a site other than the active site
An enzyme-controlled reaction is inhibited by substance X. Suggest a simple way in which you could tell whether substance X is acting as a competitive or a non-competitive inhibitor
- Increase the substrate conc.
- if the degree of inhibition is reduced = competitive inhibitor
- if it stays the same = non-competitive inhibitor
