4.4 Cofactors, coenzymes, and prosthetic groups

What do some enzymes need in order to carry out their function as biological catalysts?

Cofactors

What are cofactors?

a non-protein helper component

What may the cofactor help the enzyme by transferring?

atoms or groups from one reaction to another multistep pathway

Instead of this what may the cofactor actually form part of?

the active site of an enzyme

What is a coenzyme?

a cofactor that is an organic molecule

How are inorganic cofactors obtained?

via the diet as minerals

Examples of inorganic cofactors that obtained via the diet as minerals (4)?

iron, calcium, chloride and zinc ions

What does amylase catalyse?

the breakdown of starch

What cofactor does amylase contain?

a chloride ion

What is the chloride ion in the enzyme amylase necessary for?

the formation of a correctly shaped active site

What are many coenzymes derived from?

vitamins

What are vitamins?

a class of organic molecule found in the diet

What is the coenzyme Vitamin B3 used to synthesise (what does it convert into)?

NAD

NAD real term?

nicotinamide adenine dinucleotide

What is the coenzyme NAD responsible for?

the transfer of hydrogen atoms between molecules involved in respiration

What other coenzyme is derived from Vitamin B3?

NADP

NADP role?

plays a crucial role as an electron and hydrogen carrier in photosynthesis

What coenzyme is Vitamin B5 use to make?

coenzyme A

What is coenzyme A essential in?

the breakdown of fatty acids and carbohydrates in respiration

Prosthetic group in haemoglobin?

iron ion

What are prosthetic groups?

cofactors

Why are prosthetic groups cofactors?

they are required by certain enzymes to carry out their catalytic function

How are some cofactors bound to the enzyme protein in order to activate them?

loosely or temporarily bound

How are prosthetic groups bound to the enzyme protein in order to activate them?

tightly bound and form a permanent feature of the protein

What prosthetic group forms an important part of the structure of the enzyme carbonic anhydrase?

Zinc ions

What is carbonic anhydrase necessary for?

the metabolism of carbon dioxide

Inactive persecutor enzymes?

enzymes produced in an inactive form

What particular enzymes are produced in an inactive form?

ones that can cause damage within the cells producing them/to tissues where they are released or enzymes whose actions need to be controlled and only activated under certain conditions

What do inactive persecutor enzymes need to undergo to be activated?

a change in shape (tertiary structure) particularly to the active site

How can the change in shape to the inactive persecutor enzymes' active site be achieved?

by the addition of a cofactor

What is the persecutor enzyme called before the cofactor is added?

Apoenzyme

What is the persecutor enzyme called after the cofactor is added and it has become activated?

holoenzyme

How else is the change in the tertiary structure of the persecutor enzyme brought about?

by the action of another enzyme

How does protease change the tertiary structure/shape of active site of a persecutor enzyme?

cleaves certain bonds in the molecule

What last factor can result in a change in the tertiary structure of the persecutor enzyme and activate it?

conditions - e.g. pH or temperature

What are zymogens and proenzymes?

two terms for an inactive precursor of an enzyme that must undergo a biochemical change in order to become active

When inactive pepsinogen is released into the stomach to digest protein what enzyme is it turned into?

the active enzyme pepsin

When inactive pepsinogen is released into the stomach to digest protein what turns it into the active enzyme pepsin?

Hydrochloric acid - the acid pH

What does the change from the inactive pepsinogen to the active enzyme pepsin after it has been released into the stomach protect?

protects the body tissues against the digestive action of pepsin