2.4 - Enzymes Flashcards
1
Q
What are enzymes?
A
- biological catalysts - speed up the rate of chemical reactions without being used up
- globular proteins with complex tertiary structures
- affect metabolism on a cellular and whole organism level
2
Q
What are intracellular/extrcellular enzymes?
A
- intracellular - produced and function inside the cell
* extracellular - produced and secreted by cells, function outsode of cells
3
Q
What is catalase?
A
- intracellular enzyme
- hydrogen peroxide is produced as a by-product of many metabolic reactions
- it is harmful to cells
- catalase converts hydrogen peroxide to water and oxygen, preventing damage to tissues/cells
4
Q
What is amylase?
A
- extracellular enzymes
- secreted by salivatory glands and the pancreas into mouth and small intestine
- involved in carbohydrate digestion - hydrolyses starch into maltose
- digestion is usually done extracellularly as macromolecules are too large to enter the cell
5
Q
What is trypsin?
A
- extracellulaar protein
- secreted by pancreas into small intestine
- catalyses the digestion of proteins into peptides and amino acids
6
Q
What is metabolism?
A
The sum of all of the reactions and reation pathways happening in a cell or organism
7
Q
What is enzyme specificity?
A
- property of enzyme which describes how selective an enzyme is to its substrate
- a result of the complementary nature between the shape of the active site on the enzyme and its substrate
8
Q
What is the active site of an enzyme?
A
- the site on an enzyme where the substrate will bind to it
- complementary in shape to the enzyme
- the shape of the active site is determined by the tertiary structure
9
Q
What determines the shape of the active site of an enzyme?
A
- dna determines the order of amino acids in a polypeptide chain (primary structure)
- the order of amino acids determines the secondary and complex tertiary structure of the protein
- if the primary structure is altered, the shape of the active site changes
10
Q
What are the 2 hypotheses for how enzymes work?
A
- lock and key hypothesis
* induced fit hypothesis
11
Q
What is the lock and key hypothesis?
A
- the active site is complementary in shape to the specific substrate
- substrate collides with the enzyme at the correct speed and orientation
- the substrate fits into the active site of the enzyme (like a lock and key) sorming an enzyme-substrate complex
- the substrate/s react and an enzyme-product complex is formed
- the product/s are released and the enzyme remains unchanged for another reaction to take place
12
Q
What is the induced fit hypothesis?
A
- the enzyme’s active site (and sometimes substrate) can change shape slightly as the substrate enters the enzyme - these are conformational changes
- the initial interaction between the substrate and the enzyme is weak, but they rapidly induce changes to the enzymes tertiary structure
- the changes put strain on the substrate molecule, weakening the bonds and loweringteh activation energy
13
Q
How do enzymes catalyse reactions?
A
They lower the activation energy for the reactions
14
Q
What are the factors that affect enzyme activity?
A
- pH
- temperature
- enzyme concentration
- substrate concentration
15
Q
How does temperature affect the activity of enzymes?
A
- very low temperatures slow/prevent reactions
- higher temperatures speed up reactions
- very high temperatures cause enzymes to denature
