pack 2b proteins and enzymes

Question 1

what elements in a protein

Answer 1

carbon hydrogen oxygen and nitrogen

Question 2

conjugated proteins

Answer 2

have other chemicals within their structures example haemoglobin

Question 3

what are amino acids made of

Answer 3

• an amine group NH2
  -a carboxyl group COOH
• variable group R

Question 4

primary structure

Answer 4

• this is determined by the sequence of amino acids in a polypeptide chain

Question 5

secondary structure

Answer 5

• the folding og the polypeptide chain in localised regions due to the formation of many weak hydrogen bonds
• producing particular secondary structures - helix and beta pleated sheet

Question 6

tertiary structure

Answer 6

• this is further folding where the whole chain folds into a specific shape
• primarily involves bonding between the R groups
• stabilised by ionic bonds, hydrogen bonds, disulphide bonds

Question 7

quaternary structure

Answer 7

• protein containing more than one polypeptide chain
• further folding between subunits

Question 8

molecular shape of proteins

Answer 8

• fibrous proteins form long chains running parallel to each other with cross-bridges between the chains. this produces very stable molecules.
• collagen
• fibrous proteins tend to have structural roles in organisms
• globular proteins such as enzymes and haemoglobin carry out metabolic functions

Question 9

chromatography

Answer 9

• can be used to separate mixtures of monosaccharides and amino acids
• this is because the molecules have different molecular sizes and have different solubilites
• the smaller and more soluble the molecule the further it will be moved in the solvent
• to identify the spots that appear on the chromatogram, their Rf values must be calculated. enabling a comparison between different chromatograms run with the same solvent

Rf value = distance from origin to spot / distance from origin to solvent front (top)

Question 10

what is an enzyme

Answer 10

-biological catalyst and acts by lowering the amount of activation energy needed to make the reaction proceed
- all metabolic reactions in living organsims are catalysted by enzymes

Question 11

the induced fit model

Answer 11

• this model suggests that a substrate and its active site are not fully complementary to begin with
• the shape of the active site changes as the substrate binds and the amino acids of the active site are moulded around the substrate to form an enzyme- substrate complex
• the active site changes shape to become complementary
• this puts strain on the substrate and distorts the bonds thus reducing the activation energy neede to break the bonds

Question 12

measuring the rate of reactions

Answer 12

• amount of product / time taken
• the steeper the line, the faster the rate

Question 13

factor that effecting enzyme activity

Answer 13

• temperature
  -pH
  -

Question 14

temperature effect on enzymes

Answer 14

• very low- inactive but undamaged
• low temp - enzyme and substrate move around slowly, so as they collide only rarely.
• as temp increases, enzymes and substrates molecules gain more kinetic energy so move about more quickly
• collide more frequently and so a greater number of enzyme-substrate complexes are formed
• increase rate of reaction
• the rate of reaction reaches a maximum level and this is known as its optimum temp

Question 15

pH effect on enzymes

Answer 15

• pH refers to the concentration of hydrogen ions present in a solution
• the greater the concentration of h+, the lower the pH

Question 16

how to calculate the pH of a solution

Answer 16

calculator
press -
log
the aqueous h+ in brackets

Question 17

change in pH affects function of enzyme

Answer 17

• alters the charge on the amino acids- makes up the as
• this change in h+ ions affects this bonding, causing the hydrogen and ionic bonds that maintain the enzymes tertiary structure to break and reform in different places
• these changes can alter the shape of the active site and the substrate may no longer be complementary
• as a result no enzyme substrates can be formed
• the enzyme has been denatured

Question 18

enzyme concentration

Answer 18

• enzymes can be reused and work very efficiently even in low concentrations
• as long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction

Question 19

competitive inhibitors

Answer 19

• molecules of a competitive inhibitor have a similar shape to that of the enzymes substrate
• this allows it to compete with the substrate as it binds to the active site of the enzyme
• active sites which are blocked by the competitive inhibitors cannot be occupied by substrates, fewer enzyme-substrate complexes are formed
• the rate of reaction is therefore reduced

Question 20

non- competitive inhibitors

Answer 20

• don not combine with the enzymes active site, as their shape is not similar to the substrate
• it binds to another region of the enzyme (allosteric site)
• this results in change in tertiary shape of the enzyme, so changing the shape of the active site, so that the substrate cannot bind
• fewer enzyme- substrate complexes are formed and so reaction rate decreases
• the effect of a non competitive inhibitor is not dependent on its concentration relative to the substrate
• once added the non-competitive inhibitor inactivates the enzyme
• a few molecules may remain unaffected and the reaction rate may proceed at a slow rate