topic 1 ppqs Flashcards
describe how mRNA is produced in the nucleus of a cell [6]
- DNA helicase
- breaks hydrogen bonds
- only one DNA acts as a template
- RNA nucleotides attracted to exposed bases
- attraction according to base pairing rule
- RNA polymerase joins RN nucleotides together
- pre-mRNA sliced to remove introns
describe the structure of proteins [5]
- polymer of amino acids
- joined by peptide bonds
- formed by condensation
- primary structure is order of amino acids
- secondary structure is folding of polypeptide chain due to hydrogen bonding
- tertiary structure is 3D folding due to hydrogen, ionic and disulfide bonds
- quaternary structure is two or more polypeptide chains
describe how proteins are digested in the human gut [4]
- hydrolysis of peptide bonds
- endopeptidases break polypeptides into smaller peptide chains
- exopeptidases remove terminal amino acids
- dipeptidases hydrolyse dipeptides into amino acids
explain how starch molecules are adapted for their function in plant cells
- insoluble so doesn’t affect water potential
- helical so compact
- large molecule so cannot leave cell
explain how cellulose molecules are adapted for their function in plant cells [3]
- long straight chains
- become linked together by many hydrogen bonds to form fibrils
- provide strength to cell wall
explain how a sports drink could provide an energy boost when running [3]
- drink contains carbohydrates so raises blood glucose concentration quickly
- contains salt so glucose more rapidly absorbed
- increases glucose to muscles for respiration
- faster respiration so faster energy release
explain why maltase only breaks down maltose and allows this reaction to take place at normal body temperature [5]
- teritary structure of enzyme means
- active site is complementary to maltose
- description of induced fit
- enzyme is catalyst so lowers activation energy required for reaction
- by forming enzyme-substrate complex
explain why hydrogen bonds are important in cellulose molecules [2]
- forms cross links between chains, providing strength to cell wall
- hydrogen bonds are strong in large numbers
use figure 1 and figure 2 and your knowledge of enzyme action to explain why the arrows (which show the directions in which each new DNA strand is being produced) point in opposite directions [4]
- figure 1 shows DNA has antiparallel strands
- figure 1 shows shape of the nucleotides are different
- enzymes have active sites with specific shape
- only 3’ end can bind with active site of the enzyme DNA polymerase
explain the importance of maintaining a constant blood pH [3]
- enzyme in blood affected by change in pH
- results in change of tertiary structure
- so less oxygen binds with haemoglobin as fewer enzyme-substrate complexes are formed
explain the advantage of mitochondria in muscle cells having more cristae [2]
- more cristae means larger surface area which means more enzymes for ATP production through oxidative phosphorylation
- muscle cells use more ATP than skin cells
when glucose is respired what happens to the energy which is not
incorporated into ATP?
it is released as heat
humans synthesise more than their body mass of ATP each day. explain why it is necessary for them to synthesise such a large amount of ATP [2]
- ATP cannot be stored so is an immediate source of energy
- ATP only releases a small amount of energy at a time
