C1.1 Enzymes Flashcards
C1.1.1 Enzymes as catalysts
A catalyst:
* increases the rate of a chemical reaction
* is not changed by the reaction
* can catalyse a reactions many times
Enzymes = biological catalysts. They are made by living cells to speed up biochemical reactions.
Substrate(s) + enzyme(s) → product(s)
C1.1.2 Role of enzymes in metabolism
Almost all metabolic reactions are catalysed by an enzyme. Enzymes catalyse specific/group (of) reaction.
This allows organisms to control metabolism, as making more/less of an enzyme, cells control rate of a reaction.
C1.1.3 Anabolic reactions
Anabolic reactions use energy from ATP to produce macromolecules from monomers. They are condensation reactions.
- protein synthesis (translation) by ribosomes
- photosynthesis
C1.1.3 Catabolic reactions
Catabolic reactions break down larger molecules into smaller ones, releasing energy. This energy can be captured by coupling the reaction to ATP synthesis.
* digestion of food
* cell respiration
C1.1.4 Enzymes as globular proteins with an active site for catalysis
- Enzymes are globular proteins.
- substrate(s)+ active site shape and chemical properties match each other.
Active site amino acids are often apart in the PP but brought together by folding. 3D structure = crucial; alteration may change AS + prevent catalysis.
C1.1.5 Interactions between substrate and active site to allow induced-fit binding
The substrate binds, altering bond angles and lengths of S + AS in induced-fit binding.
Changes to substrate(s) make it easier for bonds within them to break/form.
Product(s) detach, active site to return to its original state and repeats the catalytic cycle.
C1.1.6 How do substrate-active site collisions occur?
Substrates and enzymes move randomly. When close enough to interact, the E’s chemical properties attract S to AS. Substrate–active site collision occurs = binding.
Happens more w/ higher substrate/enzyme concs or inc temperature.
C1.1.6 How does molecular motion vary between substrates and enzymes?
- In cytoplasm: both are dissolved = free to move. Often, substrate is smaller, moves more.
- Substrates = large, don’t move much. Enzyme moves in relation to substrate (transcribe DNA).
- Enzymes embedded in membranes = immobilized. Substrate does the movement.
C1.1.7 Relationships between the structure of the active site, enzyme–substrate specificity and denaturation
This is called Enzyme–substrate specicity allows specific binding. Enzyme’s 3D shape is determined by AA interactions, affected by heat/acidity. AS changes can prevent substrate catalysis + denaturation.
C1.1.8 Effects of temperature on the rate of enzyme activity
Liquid is heated→particles gain kinetic energy. Enzyme + substrate molecules move quicker, collision chance increases.
Heating enzymes = bonds to vibrate more, increasing chance of bond breakage. Alters active site → denaturation.
