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Biological Molecules Exam Questions and Answers
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Biological Molecules Exam Questions and Answers
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Biological Molecules Exam Questionsand Answers
Explain how cellulose molecules are adapted for their function in plant cells (3) -
Answer-- Long and straight chains
- Become linked together by many hydrogen bonds to form fibrils
- Provide strength (to cell wall)
Describe the structure of proteins (5) - Answer-- Polymer of amino acids
- Joined by peptide bonds;
- Formed by condensation reaction
- Primary structure is order of amino acids;
- Secondary structure is folding of polypeptide chain due to hydrogen bonding;
- Tertiary structure is 3-D folding due to hydrogen, ionic and disulfide bonds;
- Quaternary structure is two or more polypeptide chains.
In humans, the enzyme maltase breaks down maltose to glucose.
This takes place at normal body temperature.
Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature (5) - Answer-- Tertiary
structure (means)
- Active site complementary to maltose
- Description of induced fit: the active site changes shape slightly to bind to the
substrate, putting stress on the bonds
- Enzyme is a catalyst
- By forming enzyme-substrate complexes
Describe competitive and non-competitive inhibition of an enzyme (5) - Answer--
Inhibitors reduce binding of enzyme to substrate
Competitive inhibition:
- Inhibitor similar shape to substrate
- Binds in to active site of enzyme
- Inhibition can be overcome by more substrate
Non-competitive inhibition:
- Inhibitor binds to site on enzyme other than active site;
- Prevents formation of active site
- Cannot be overcome by adding more substrate
Describe and explain the link between oxygen concentration, rate of respiration and rate
of uptake of potassium ions (4) - Answer-- greater rate of oxygen consumption leads to
greater rate of respiration and greater rate of uptake
- (b/c) oxygen is required for respiration
- (and) respiration produces ATP / releases energy
, - (so) potassium ions taken up by active transport
Describe the structure of a cellulose molecule and explain how cellulose is adapted for
its function in cells (6) - Answer-- made from β-glucose;
- joined by condensation reaction
- hydrogen bonds linking chains
- cellulose makes cell walls strong
- can resist turgor/osmotic pressure
- bond difficult to break;
- resists digestion / action of microorganisms / enzymes
Contrast the structures of DNA and mRNA molecules to give three differences (3) -
Answer-- Complementary bases pair pairing
- DNA polymerase;
- Nucleotides join together (to form new strand
Describe how ATP is resynthesised in cells (2) - Answer-- From ADP and phosphate
- By ATP synthase;
- During respiration/photosynthesis;
Give two ways in which the hydrolysis of ATP is used in cells (2) - Answer-- To provide
energy for other reactions/named process;
- To add phosphate to other substances and make them more reactive
Describe the induced-fit model of enzyme action (2) - Answer-- active site not
complementary to/does not fit substrate
- Shape of active site changes as substrate binds
- Stressing bonds
Describe the structure of glycogen (2) - Answer-- Polysaccharide of α-glucose
- Joined by glycosidic bonds
Describe the function of each of these enzymes.
DNA Helicase & DNA Polymerase (2) - Answer-DNA helicase - (unwinding DNA and)
breaking hydrogen bonds
DNA polymerase - joins (adjacent) nucleotides
Contrast the structures of ATP and a nucleotide found in DNA to give two differences
(2) - Answer-- ATP has ribose and DNA nucleotide has deoxyribose
- ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group
- ATP base always adenine and in DNA nucleotide base varies
Give three properties of water that are important in biology (3) - Answer-- Is a metabolite
- Is a solvent
- Has a (relatively) high heat capacity
- Has a (relatively) large latent heat of vaporisation / evaporation
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