C1.1 Enzymes and Metabolism Flashcards
Define enzymes and their use
Enzymes are globular proteins that act as biological catalysts where they increase the rate of a reaction but remain unchanged.
What is the role of enzymes in metabolism?
- Metabolism: the complex network of interdependent and interacting chemical reactions occurring in living organisms.
- Each enzyme catalyses one or a group of specific reactions.
- Due to this enzyme specificity, living organisms require many different enzymes, and control over metabolism can be exerted through these enzymes.
Describe anabolic reactions
- Anabolic reactions build up smaller molecules into larger ones
- Examples:
– protein synthesis
– glycogen formation
– photosynthesis
Describe catabolic reactions
- Catabolic reactions break down larger molecules into smaller ones.
- Examples:
– hydrolysis of macromolecules into monomers in digestion
– oxidation of substrates in respiration
Active site of enzymes
The active site of enzymes only has a few AAs but the interactions between the AAs within the overall 3D structure of the enzyme ensure that it has the necessary properties for catalysis. Properties such as binding to the substrate molecule, holding onto it while the chemical reaction takes place, and lowering the energy of the transition state.
What is induced-fit binding?
Where both substrate and enzymes change shape when binding occurs.
What role does movement play in enzyme-substrate complexes?
Movement: result of the kinetic energy that the molecules have which allows an enzyme to collide with a substrate.
- It is needed for a substrate molecule and an active site to come together.
What happens during the denaturation of enzymes?
During denaturation, the bonds (e.g. hydrogen bonds) holding the enzyme molecule in its precise 3D shape start to break. This means the 3D shape of the enzyme changes. Therefore the shape of the active site is permanently changed, preventing the substrate from binding.
What is meant by enzyme-substrate specificity?
The specificity of an enzyme is a result of the complementary nature between the shape of the active site on the enzyme and its substrate(s). The active site of an enzyme has a specific shape to fit a specific substrate.
Explain the relationships between the structure of the active site, enzyme-substrate specificity and denaturation.
The active site is a precise 3D shape which ensures enzyme-substrate specificity. If an enzyme is denatured (due to high heat or extreme pH) then this specific shape is changed and a substrate can no longer bind with the enzyme.
What happens to enzyme activity at low temperatures?
Enzymes work slowly due to a lack of kinetic energy and collisions between the substrates and active sites.
How does increasing temperature towards the optimum temperature affect enzyme activity?
Increases enzyme activity as the molecules have more kinetic energy, leading to more collisions with substrate molecules and a faster rate of reaction.
What is the effect of heating enzymes beyond the optimum temperature?
Breaks the bonds that hold the enzyme together, causing it to lose its shape and become denatured.
Why does the rate of an enzyme-controlled reaction decrease as the pH level moves further from the enzyme’s optimum pH?
Rate of enzyme-controlled reaction decreases because extremes of pH breaks the bonds that hold the aa chain together, denaturing the active site and reducing rate of reaction.
What happens to the rate of enzyme activity when the concentration of substrate is increased?
The rate of enzyme activity increases because there are more substrate molecules to collide with the enzyme and occupy its active site.
What is activation energy?
Activation energy is the amount of energy needed by the substrate to become unstable enough for a reaction to occur and for new products to be formed.
What effect do enzymes have on activation energy?
Lowers the activation energy required for the reaction to take place.
