ENZYMES OCR BIOLOGY

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  • Created by: Davina1st
  • Created on: 06-12-20 14:29
What are enzymes?
Biological catalysts, globular proteins that interact with the substrate to react much faster, bu in a less harsh environment. They lower the activation energy by increasing the amount of collisions, but don't get used up themselves.
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What does the term biological catalyst mean?
Inside the body, changing rate of reaction
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What is an anabolic reaction?
Small molecules assembled into large ones, requires energy. e.g Protein synthesis
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What is a catabolic reaction?
Large molecules breaking down into small ones, releases energy. e.g ATP broken down to ADP
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What is activation energy?
The amount of energy needed to be supplied for a reaction to start.
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Describe the lock and key hypothesis
The active site which is specific to the substrate, will only fit the substrate. When the substrate is bound tot the active site, an ESC is formed, the products formed are am EPC. The products are released leaving the enzyme unchanged.
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Describe the induced fit hypothesis
The active site of the enzyme slightly changes as the substrate enters,
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How does an induced fit lower the activation energy?
The weak interactions between the enzyme and substrate rapidly induce changes in the enzymes tertiary structure that strengthen binding, putting strain on the substrate. This can weaken bond/s in the substrate lowering activation energy.
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What is an intracellular enzyme?
An enzyme that acts within cells. e.g Catalase is an intracellular enzyme that speeds up the breakdown of harmful hydrogen peroxide .
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What is an extracellular enzyme?
Extracellular enzymes are enzymes that are released from cells to break down large nutrient molecules into smaller molecules.
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How is protein digested?
Trypsin is a protease, in catalyses the digestion of proteins into smaller peptides which can be broken down to amino acids. Produced in the pancreas and released with pancreatic juice into small intestine. Amino acids absorbed into DS into blood
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Describe the breakdown of starch
Starch polymers are broken down into maltose, which is a disaccharide, amylase is the enzyme involved. maltose is broken down into glucose, maltase is this enzyme in the small intestine. Glucose is small enough to be absorbed by cells in the DS
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What is the effect of temperature on enzyme activity?
Increased temp= increased kinetic energy= more successful collisions.
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What happens to an enzyme when the temperature becomes too high?
At high temperature, the bonds holding the protein together break, which results in the active site of the enzyme changing shape. This means the substrate can no longer fit and the enzyme will no longer function as a catalyst.
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What is the optimum temperature?
(Vmax) The temperature at which the enzyme has the highest rate of activity. Most ESC formed.
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What is the effect of pH on enzyme activity?
At optimum pH, there are the most successful collision, greatest ESC. As pH changes, the charge around the active site changes so less attraction between the enzyme and substrate, less ESC. pH increases more so denaturation as ionic bond break.
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What is the effect of enzyme concentration on enzyme activity?
Assuming substrate is unlimited, increase in enzyme conc=increase in rate. If substrate is limited, rate is lowed down and stays the same. More ESC to no further ESC being formed, active sites left with no work to do.
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What is the effect of substrate concentration on enzyme activity?
As substrate conc increases so does rate of reaction. After point of saturation, increasing conc doesn't affect reaction rate. No more ESC, and enzyme conc becomes limiting factor
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What is an inhibitor?
Molecules that prevent enzymes from carrying out their normal function of catalysis. There are two types, Competitive and non-competitive
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What is competitive inhibition? Describe it
The competitive inhibitor and substrate have similar shapes, inhibitor fits into active site. This means the substrate cannot gain access to the active site and no ESC formed. The effect is reversible, over come by increasing substrate conc.
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How does competitive inhibition affect rates of reaction?
Does not change Vmax, but does reduce rate. If substrate conc is increased, there will be more substrate than inhibitor so original Vmax is reached.
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What is non-competitive inhibition? Describe it
Inhibitor binds to the allosteric site on an enzyme, which changes the shape of the active site, this means the substrate no longer fits/complimentary. Permanently denatured active site.
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How does non-competitive inhibition affect rates of reaction?
Vmax is significantly lower, as less ESC formed as the active site is denatured and substrate cannot bind. Increasing substrate or enzyme conc will not change rate of reaction.
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Give an example of a non-competitive inhibitor
Proton Pump inhibitors (PPI's) are used to treat digestion. Irreversibly block an enzyme system responsible for secreting H+ into stomach. Which makes them effective in reducing acid in the stomach. If left=stomach uslers
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What is end product inhibition?
Enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it. Acts as a control mechanism for the reaction. Excess products not made/wasted.
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What is the difference between co factors and coenzyme?
Co factors are inorganic non protein which help enzymes to carry out their function as biological catalysts. Whereas coenzyme are organic
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Give an example of a co factor
Amylase which catalyses the breakdown of starch, contains a chloride ion responsible for the correctly shaped active site.
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Give an example of a coenzyme
Vitamins, Vitamin B5 is used to make coenzyme A which is essential in the breakdown of fatty acids and carbohydrates in respiration
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Are prosthetic groups co factors or co enzymes?
Cofactors, they are required by some enzymes to carry out their functions. Prosthetic groups are a permanent part of the protein.
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Describe precursor activation
Inactive enzymes need to undergo a change in shape, in the active site to be activated. Adding a co factor achieves the correct active site shape.
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What is the precursor activation sequence?
Inactive apoenzyme + cofactor ------> active holoenzyme
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Give an example of precursor activation
Inactive pepsinogen is released into the stomach to digest proteins, the acid pH brings about the change into active enzyme pepsin. This prevents the digestion of your own tissues.
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Card 2

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What does the term biological catalyst mean?

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Inside the body, changing rate of reaction

Card 3

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What is an anabolic reaction?

Back

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Card 4

Front

What is a catabolic reaction?

Back

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Card 5

Front

What is activation energy?

Back

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