Enzymes and nucleic acids Flashcards
(17 cards)
A high concentration of galactose slows down the breakdown of lactose by lactase. Use your knowledge of competitive inhibition to suggest why
- galactose is a similar shape to lactose
- binds to active site
- prevents substrate from binding with active site
- Galactose is a similar shape to lactose
- Binds to active site
- Prevents substrate from binding with active site
Competitive inhibitors mimic the substrate’s structure, allowing them to bind to the enzyme’s active site.
Describe how a scientist produce a calibration curve of colorimeter reading against concentration of maltose on a graph
- Use maltose solutions of known concentrations
- Measure colorimeter value of each solution and plot calibration curve
- Find concentration of sample from calibration curve
Explain why the replication of DNA is described as semi-conservative?
- Each strand acts as a template
- Each molecule of DNA consists of one new and one old strand
How do you know that a virus contains single stranded DNA?
No base pairing
Explain the ratios of bases in DNA?
- A and T always pair as do C and G
- Number of A = T / C = G
How does a competitive inhibitor decrease the rate of an enzyme-controlled reaction?
- Similar size/shape, complementary to the enzyme’s active site
- Binds to the enzyme’s active site
- Prevents enzyme-substrate complex forming
describe how the structure of a protein depends on the amino acid it contains
- primary sequences of a protein depends on the amino acid it contains
- secondary structures fromed by hydrogen bonding
- tertiary structure formed by interactions
- creates active sites in enzymes
- quaternary structure formed by interactions between polypeptides
describe two ways in which dipeptides are similar and one way on which they may differ
- all have an amine group
- all have a carboxyl group
- variable R groups
How can two proteins have the same number and type of amino acids but different tertiary structures
- Different sequence of amino acids
- forms ionic/hydrogen/disulphide bonds in different places
why would a change at aino acid 300 have no effect on the rate of reaction catalysed by the enzyme, when the same change at amino acid 279 significantly reduced the rate of reaction catalysed by the enzyme
- both negatively charged to positively charged in amino acid
- change at amino acid 300 does not change the shape of active site
- amino acid 279 may have been involved in a bond and so the shape of the active site changes
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule
- condensation reaction
- between phosphate and deoxyribose
- By DNA polymerase
name the 2 scientists who proposed models of the chemical structure of DNA and of DNA replication
watson and crick
Use your knowledge of semi conservative replication to suggest the role of the single stranded DNA fragments
- act as a template
- determines order of nucleotides
Give two features of DNA and explain how each one is important in the semi-conservative replication of DNA
- weak hydrogen bonds easily broken between bases allowing two strands to separate
- two strands, so both can act as templates
why does DNA polymerase work in opposite directions of each strand on DNA
- DNA has anti-parallel strands
- Shape of the nucelotides is different
- Enzymes have active sites with specifc shape
- Only the 3’ end can bind with active sites of enzyme
explain what is meant by the term semi conservative replication?
- two identical copies
- each molecule of DNA consists of one old strand and one new strand due to moth strands acting as a template
