Enzymes part 2 Flashcards
(41 cards)
What does latic acid dissociate into
H+ and lactate
What does pyruvic acid dissociate into
H+ and pyruvate
What is a buffer
A buffer is something that resists change in pH so the pH of the blood remains at about 7.4
How does a buffer work
- a buffer donates or accepts hydrogen ions
- some proteins such as haemoglobin can also donate or accept protons and act as buffers
How does pH affect the bonds in molecules
- a hydrogen ion is attracted to the negative charged ions or molecules or parts of molecules,
- excess hydrogen ions interfere with the hydrogen bonds and ionic forces holding the tertiary structure of the enzyme together therefore the enzymes tertiary structure changes and the active site changes shape meaning that the substrate can no longer fit into the active site lowering the rate of reaction
- increasing the concentration of hydrogen ions will also alter the charges on the active site of enzyme molecules because more proteins cluster around the negatively charged group which interferes with the binding of the substrate molecules onto the active site
why is pH so important to enzymes
enzymes work with a narrow change in pH
- small changes either side of the optimum pH slows the rate of reaction as the active site is disrupted
- if normal pH is restored then the enzyme can form hydrogen bonds again and the tertiary structure is formed again so the active site is restored
- at extremes of pH the active site is permanently changed and the enzyme is denatured and can no longer catalyse the reaction
Draw the pH graph for enzymes
DRAW IT
Draw the temperature graph for enzymes
DRAW IT
What is the pH of intracellular enzymes
they have an optimum pH that is close to 7
What is the pH of extracellular enzymes
they have optimum pH values which are different from pH 7,
For example amylase in the mouth works best at pH 6.8
What is the pH of the stomach
between 1 and 2 as this is what pepsin works best in
what is the pH in the small intestine
7.8 as this is the optimal for protein digesting enzymes such as trypsin and enterokinase so digest peptides into amino acids
What is the effect of increasing substrate concentration on the rate of reaction
if you increase the concentration of substrate the rate of reaction increases
- more enzyme substrate complexes can form
- more product molecules are formed
- substrate concentration is limiting in the reaction because as it increases the rate of reaction increases therefore it is a limiting factor
The reaction will reach its maximum amount when the substrate is increased even further then this happens…..
- adding more substrate molecules to increase substrate concentration will not increase the reaction
- all the enzymes active sites are occupied by substrate molecules
- if more substrate molecules are added then they cannot successfully collide and fit into the enzymes active site
Draw the effect of changing enzyme concentration graph
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What is the effect of enzyme concentration on the rate of reaction
As the enzyme concentration increases the rate of reaction increases this is because
- more active sites of the enzyme become available
- more successful collisions between the enzyme and substrate occur
- more enzyme-substrate complexes can form per unit time so the rate of reaction increases
- enzyme concentration is the limiting factor as it increases and so does the rate of reaction
What happens when the substrate concentration is fixed and you try to increase the rate of reaction by increasing the enzyme concentration
- the reaction would have reached the maximum rate
- so if the enzyme concentration has increased further then there will be no increase in the rate of reaction because the active site of the extra enzyme molecules will not be occupied by substrate molecules
- the enzyme concentration is no longer the limiting factor as enzyme concentration increases the rate of reaction increases
- substrate concentration is now the limiting factor as lack of substrate molecules is preventing the rate of reaction from increasing
What is enzyme synthesis
this is when depending on the cells needs, genes for synthesising particular enzymes can be switched on o r off
What is enzyme degradation
cells are continuously degrading old enzyme molecules to their component amino acids and synthesising new enzyme molecules from amino acids
What are the advantages for enzyme degradation
- elimination of abnormally shaped proteins that might otherwise accumulate and harm the cell
- the regulation of metabolism in the cell by eliminating any superfluous enzymes
it is important in order for a cell to regulate its metabolism properly
DRAW graph for enzyme concentration on the rate of reaction
DRAW IT
Describe how the rate of reaction catalysed by an enzyme progresses over time
- At the beginning of the reaction, enzyme and substrate molecules are in high concentration and are moving randomly this means that there is a greater chance of a substrate molecule colliding with an enzymes active site
- as the reaction goes on the substrate molecules are used up as they are converted to products therefore the concentration of the substrate drops
- therefore the frequency of the collisions between enzymes and substrate molecules decreases because enzymes may collide with product molecules therefore the rate of the reaction decreases
- the initial rate is the maximum rate
what are inhibitors
they are substance that reduces or stops a reaction by reducing the activity of an enzyme
How do inhibitors work
they collide with an enzyme molecule in a way which effects how the substrate binds to the enzymes r effects the enzymes turnover number
- some block the active site while others change the shape of the active site
what are competitive inhibitors
this is where the enzyme has a similar shape to that of the substrate molecule and competes with the substrate molecules for the enzymes active site, it blocks the active site and prevents the formation from enzyme-substrate complex
