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Summary structure and function of enzymes
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quick summary on details of enzymes including structure and function following the OCR A specification
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ENZYMES: Enzymes- protein molecules- biological catalyst
They speed up the rate of reactions without being used up or undergoing permanent
changes.
Globular protein- 3D shape due to tertiary structure
Metabolic pathways are controlled by enzymes- every metabolic reaction in a living
organism= uses an enzyme catalyst
Enzymes lower activation energy: cellular reactions can take place quickly at body temp and
small amounts of enzyme can catalyse many reactions.
ACTIVATION ENERGY- minimum sufficient energy required to break or form bonds
SITE OF ACTION OF ENZYMES
1. Enzymes= proteins= produced via protein synthesis inside cells
2. Some remain in cells others are secreted out
3. So, they can be intracellular or extracellular
4. Intracellular are produced and function in cells- CATALASE
5. Extracellular are secreted by cells to catalyse outside- AMYLASE and TRYPSIN
MECHANISM OF ENZYME ACTION:
Enzymes have a specific shape active site where a specific shaped substrate will fit to form- ENZYME
SUBSTRATE COMPLEX
The enzyme substrate complex is temporary as after catalysation, products are released, and
enzyme will return to its original state
Extreme heat and PH= denature= change shape of active site so substrate can’t bind
Substrates collied with active site= needs correct orientation and speed for reaction
ENZYME SPECIFICITY:
Enzyme and substrate are complementary
The specific shape of enzyme is determined by complex tertiary structure
LOCK AND KEY MECHANISM:
Enzymes and substrate are rigid structures that bind/ lock and splits the substrate into 2 products.
Given the right circumstances, the enzyme can reverse the reaction and reform the substrate.
Doesn’t explain lowering of activation energy to speed up rate of reaction.
, INDUCED FIT MECHANISM:
Modification of the lock and key
The enzyme and substrate interact as the enzyme and its active site changes shape
(conformational changes)
The substrate is held in place in the active site by temporary bonds between the substrate
and r-groups of the enzyme’s amino acids. – destabilises bonds (stress) in substrate making
them easier to be broken
The enzyme will return to its original shape after.
Enzymes provide an alternate energy pathway with a lower activation energy.
Without enzymes extremely high temps/ pressure would be required= extreme conditions will kill
cells
Metabolism- the total of all the chemical reactions in an organism= use enzymes
Can either be:
1. Catabolic pathways- involves breakdown/ degradation of large biological molecules with the
release of energy.
e.g., starch maltose
2. Anabolic reactions- involves construction of biological molecules using energy.
e.g., nucleotides DNA
this means enzymes may influence both structure and function of cells and tissues.
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