C1.1 Enzymes Flashcards
(27 cards)
Define enzymes.
Enzymes are proteins that act as biological catalysts in cells and allow chemical reactions to occur at a suitable rate in the conditions found in living organisms.
What role do enzymes play in increasing rates of reactions in cells?
Enzymes ensure that substrate molecules are orientated correctly and close enough for a reaction to occur. Without the presence of enzymes, the rate of chemical reactions in organisms would be too slow to support life.
Outline the interaction between the enzyme and substrate.
Substrate Approaches: The substrate moves close to the enzyme’s active site.
Binding: The active site undergoes a slight conformational change to fit the substrate more snugly.
Catalysis: The enzyme lowers the activation energy, facilitating the conversion of the substrate into products.
Release: The products are released, and the enzyme returns to its original shape, ready to catalyse another reaction.
Why are enzymes essential in cells?
They speed up metabolic reactions
Metabolism consists of thousands of interconnected chemical reactions, divided into two main types:
* Anabolic reactions: Build larger molecules from smaller ones (e.g., protein synthesis).
* Catabolic reactions: Break down larger molecules into smaller ones (e.g., digestion).
Without enzymes, these reactions would occur too slowly to sustain life.
How do intracellular and extracellular enzymes work?
Intracellular enzymes: Operate within cells to catalyse metabolic reactions (e.g., enzymes in glycolysis).
Extracellular enzymes: Are secreted to work outside cells, such as in digestion (e.g., amylase breaking down starch in the mouth).
What are the key functions of metabolic reactions.
They provide a source of energy for cellular processes (growth, reproduction, etc.)
They enable the synthesis and assimilation of new materials for use within the cell
Define specificity in relation to enzyme structure and function.
Enzymes are highly specific, meaning each enzyme catalyses only one particular reaction or a group of closely related reactions.
This ensures that metabolic pathways are highly regulated and efficient.
This specificity arises from the unique shape and chemical properties of the enzyme’s active site, where the substrate binds.
Explain the control of metabolism through enzymes.
1. Regulation by Inhibitors and Activators
Enzymes can be regulated by inhibitors (molecules that decrease enzyme activity) or activators (molecules that increase enzyme activity).
2. Feedback Mechanisms
Feedback inhibition is a common way to control metabolic pathways. In this process, the end product of a pathway inhibits an enzyme early in the pathway to stop the process.
3. Environmental Regulation
Enzyme activity depends on environmental factors such as temperature and pH.
Organisms regulate these factors to optimize metabolic reactions.
Define what an anabolic reaction is.
An anabolic reaction is one that forms macromolecules from monomers by condensation reactions.
Define what a catabolic reaction is.
Catabolic reactions involve the formation of monomers from macromolecules.
What is an example of an anabolic reaction?
An example of an anabolic reaction include:
protein synthesis
glycogen formation
photosynthesis
What is an example of a catabolic reaction?
Examples of catabolic reactions include hydrolysis of macromolecules into monomers in digestion and oxidation of substrates in respiration.
What is an active site?
The enzyme’s active site is composed of only a few amino acids with a specific 3D shape to bind to a substrate molecule. The active site has the necessary properties for catalysis.
What is induced-fit binding?
Induced-fit binding is where both substrate and enzymes change shape when binding occurs.
What role does movement play in enzyme-substrate complexes?
Movement is needed for a substrate molecule and an active site to come together. Movement is the result of the kinetic energy that the molecules have which allows an enzyme to collide with a substrate.
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 is a substrate?
A substrate is a molecule that binds with an enzyme with the enzyme’s active site. Substrates bind to enzymes, forming a temporary enzyme-substrate complex. Some enzymes have two substrates that must each collide with a separate active site at the same time.
What happens to enzyme activity at low temperatures?
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?
Increasing the temperature towards the optimum 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?
Heating enzymes beyond the optimum temperature will break 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?
The rate of an enzyme-controlled reaction decreases as the pH level moves further from the enzyme’s optimum because extremes of pH break the bonds that hold the amino acid chain together, denaturing the active site and reducing the rate of reaction.
What happens to the rate of enzyme activity when the concentration of substrate is increased?
When the concentration of substrate is increased the rate of enzyme activity increases. This is because there are more substrate molecules to collide with the enzyme and occupy the active site.
