2.1.4 Enzymes Flashcards
What are enzymes? What are their functions?
They are biological catalysts, globular proteins, and they control metabolic pathways.
Define the term ‘catalyst’
They are molecules that speed up the rate of chemical reactions without being used up or undergoing permanent change.
What are metabolic pathways?
Metabolic pathways in a living cell are a series of consecutive reactions where each step is catalysed by a specific enzyme that produces a specific product.
What are catabolic reactions?
Catabolic reactions break down large molecules and release energy. E.g. respiration.
What are anabolic reactions?
Give an example.
Anabolic reactions synthesise larger molecules from smaller ones. E.g. photosynthesis.
What are intracellular enzymes?
Enzymes that are produced and function inside the cell
Give one example of a intracellular enzyme.
Catalase
- Protects cells from damage from hydrogen peroxide by breaking it down into water and oxygen.
- Also, in eukaryotic cells, catalase is found inside small vesicles called peroxisomes. WBC ingest pathogens and use catalase to kill the microbe.
What are extracellular enzymes?
Enzymes that are secreted and function outside the cell.
Give two examples of extracellular enzymes.
Amylase
- Produced in the salivary glands/ pancreas and works in the mouth/ small intestine.
- Breaks down starch into maltose.
Trypsin
- Produced in the pancreas and works in the small intestine.
- Breaks down proteins into smaller peptides and amino acids via the hydrolysis of peptide bonds.
Why is digestion usually carried out by extracellular enzymes?
Because the macromolecules being digested are too large to enter the cell.
What does the tertiary structure of an enzyme do?
What is its importance?
The tertiary structure of an enzyme determines the shape the active site.
It is important, as the shape of the active site is complementary to the shape of the substrate molecule.
So, if the shape of the active site is incorrect/ has been changed due to a problem with the tertiary structure, then the enzyme would not function, and the person could develop a serious disease.
Describe how the shape of an enzyme is determined.
Enzymes are proteins that are formed from chains of amino acids held together by peptide bonds.
The order of amino acids determines the enzyme’s tertiary structure, which in turn determines the shape of the enzyme.
If the order of aa is altered, the resulting three-dimensional shape changes.
Explain what is meant by the ‘turnover number’ of an enzyme.
What does the term ‘specificity’ mean in relation to enzymes?
The specificity of an enzyme refers to its ability to catalyse just one reaction or type of reaction.
It is a result of the complementary nature between the shape of the active site on the enzyme and its substrate(s).
Describe the lock and key hypothesis.
The tertiary structure of an enzyme determines the shape of an active site that has a complementary shape to that of the substrate.
Through random movement, a substrate collides with the active site - forms enzyme-substrate complex (ES complex) - held together by temporary hydrogen bonds.
Substrate molecule is either built up, or broken down into the product molecule - forms an enzyme-product complex whilst still in the active site.
Product molecule leaves the site, and the enzyme is now able to form another ES complex.
