Chapter 4

  • Created by: Sydneyxx
  • Created on: 03-02-19 13:56
What is an enzyme?
Biological catalyst. Globular proteins that interact with a substrate causing them to react at much faster rates.
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What is an anabolic reaction?
Building up reaction - catalysed by enzymes.
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What is a catabolic reaction?
Breaking down reaction - catalysed by enzymes.
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What is the lock and key hypothesis?
Specific substrate will fit the active site of enzyme. Enzyme-substrate complex formed and create an enzyme-product complex. Enzyme is unchanged.
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What is the induced-fit hypothesis?
Enzyme changes shape slightly as substrate enters. Initial interaction is weak but induce change so in tertiary structure and lowers activation energy.
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What is an intracellular enzyme?
Act within cells. Catalase breaks hydrogen peroxide down into oxygen and water.
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What is an extracellular enzyme?
Enzymes released from cells to break down large molecules into smaller molecules. Work outside cell. Smaller molecules can then be absorbed by cells. Mostly in digestion (amylase and trypsin).
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Describe the digestion of starch?
Amylase (in saliva) breaks it down to maltose. Maltase (in small intestine) breaks it down to glucose. Glucose is small enough to be absorbed in blood stream.
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Digestion of proteins?
Protease breaks proteins into polypeptides then amino acids.
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How does temperature affect enzymes?
Increasing temperature increase kinetic energy so enzyme and substrate collide more frequently. At higher temps the bonds vibrate more and break changing tertiary structure and denaturing enzyme. No longer complementary.
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What is meant by the optimum temperature?
Temperature at which the enzyme has the highest rate of activity. Varies between organisms.
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How does pH affect enzymes?
If there are more than or less then the correct concentration of hydrogen ions the active site will not be the correct shape as bonds will break changing the tertiary structure and denature.
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How does enzyme and substrate concentration affect the rate?
Increased number of particles leads to increased rate of reaction. Only goes up to Vmax where all active sites are occupied by substrate particles so no more enzyme-substrate complexes can be made.
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What is an inhibitor?
Molecules that prevent enzymes from carrying out their normal function of catalysis.
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What is a competitive inhibitor?
Molecule that has a similar shape to substrate and binds to active site. Blocks substrate from active site preventing catalyzing reaction. Compete with substrate and slow reaction down. It is temporary and reversible.
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What is a non-competitive inhibitor?
Binds to the allosteric site. Changes tertiary structure meaning active site changes shape so substrate can't bind as its no longer complementary. Usually non-reversible and leads to denaturing.
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What is end-product inhibition?
Occurs when a product of a reaction acts as an inhibitor to the enzyme that produces it.
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What is a co-factor?
Non-protein component that may help transfer atoms or groups from one reaction to another in a multi-step pathway or may form part of active site to help enzymes carry out their function. An organic co-factor is called a co-enzyme.
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Where are inorganic co-factors and organic co-factors (co-enzymes)?
Inorganic co-factors are obtained via the diet. Co-enzymes are derived from minerals.
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What are prosthetic groups?
Co-factors that are required by certain enzymes. Tightly bound to enzyme to form a permanent part of the protein.
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What is a precursor enzyme?
Inactive when they cause damage in the cells producing them or to tissues where they are released or enzymes whos action needs to be controlled. Undergoes a change in tertiary structure and co-factor is added to form an holoenzyme.
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Card 2


What is an anabolic reaction?


Building up reaction - catalysed by enzymes.

Card 3


What is a catabolic reaction?


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Card 4


What is the lock and key hypothesis?


Preview of the front of card 4

Card 5


What is the induced-fit hypothesis?


Preview of the front of card 5
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