Summary AQA A Level Biology notes- Many proteins are enzymes Unit 1
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Course
Unit 1 - Biological molecules
Institution
AQA
Notes on many proteins are enzymes sub-topic within AQA A Level Biology Unit 1- Biological Molecules. These notes contain sub headings with different methods of note taking like tables, images from online videos and concise bullet points.
Introducing enzymes:
Organisms need to carry out metabolic reactions in order to survive.
〰️ Metabolism refers to all the reactions of the body.
e.g. chloroplast- photosynthesis, mitochondria- respiration.
These reactions need to happen quickly so that organisms can respond to the
changes in their environment.
Reactions can be sped up by:
Temperature- high temperatures can damage cells- melt lipids, denatures
proteins etc.
Using a catalyst.
〰️ A catalyst is a chemical that speeds up the rate of reaction and
remains unchanged and reusable at the end of the reaction.
Biological catalysts for metabolic reactions are enzymes.
To carry out metabolic reactions quickly, cells use proteins called enzymes
which take the reactants and turn them into products.
Any molecule that can have a reaction catalysed by an enzyme is called a
substrate.
The number of substrates an enzyme can catalyse in one minute is called the
enzyme’s turnover number.
Substrates bind to the reactive part of an enzyme- its active site.
Many proteins are enzymes 1
, A substrate will only bind with an active site if it is the correct shape.
〰️ Complementary binding refers to when two molecules fit together to
complete each other.
The ability of an enzyme to function is affeced by the 3D shape of its active
site.
The shape of the active site can be affected by:
pH
Temperature
The presence of inhibitors (inhibits the enzyme from working) or cofactors
(bind to the enzymes and make it better)
Key concepts in enzymes:
If the right molecules collide with suffieint energy, then a chemical reaction will
occur.
All reactions require a certain amount of kinetic energy to start- activaition
energy.
〰️ Activation energy- the amount of energy needed to start a reaction.
More molecules have enough energy = more successful collisions every
second.
A reaction with a lower activation energy will occur faster.
This is because there will be more molecules with sufficient energy to react.
The change in energy that occurs during a reaction can be shown in a graph:
Many proteins are enzymes 2
, Enzymes catalyse reactions by lowering the activation energy required for a
reaction to occur.
This form of catalysis allows reactions to occur at lower temperatures.
Active sites:
Enzymes can only catalyse a reaction if a substrate binds to the specific active
site.
Most metabolic reactions occur in a series of small steps- addition of water,
addition of ions, change in shape etc.
Many proteins are enzymes 3
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