What is an example of a globular protein that is also an enzyme?
Pepsin
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What is pepsin?
An enzyme which catalyses the digestion of proteins.
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Where is pepsin found?
The stomach
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Why is it relevant that pepsin is found in the stomach?
As the stomach is an acidic environment with a low pH.
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Why do most enzymes denature at low pHs?
Because they contain amino acids with basic R groups that act as a base, meaning they accept hydrogen ions. They then become positively charged. This affected the ionic bonds and hydrogen bonds in the protein. This results in the enzyme denaturing and therefore alters its function.
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Why are basic R-groups positively charged?
Because they accept hydrogen ions.
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Why is pepsin not affected by the low pH?
Because the primary structure of pepsin has few basic R-groups, which prevents the tertiary structure to be affected by the low pH.
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How is the tertiary structure of pepsin kept stable?
By the hydroegn bonds and disulphide links.
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What are the properties of fibrous proteins?
Long polypeptide chains with repeating sequences of amino acids Insoluble in water Strong
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Why are fibrous proteins insoluble in water?
Because the amino acids have non-polar R-groups.
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Why are fibrous proteins insoluble in water?
Because the amino acids have non-polar R-groups.
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Why are fibrous proteins strong?
Because the polypeptide chains are able to form fibers which makes the proteins strong.
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Examples of fibrous proteins.
Collagen Keratin Elastin
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What is the structural role of collagen?
It forms tendons.
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What is the structural role of keratin?
It hardens fingernails.
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What is the structural role of elastin?
It makes tissues stretchy.
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Define fibrous protein.
It is a very long, strong and insoluble protein which often has a structural role in organisms.
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Where is collagen found?
In the artery walls In bones In the tendons
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What functions does collagen have whilst in the artery walls?
They prevent vessels from bursting from high pressure
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