What role do cofactors play in enzyme catalysed chemical reactions? Flashcards
1
Q
Why are cofactors important
A
- Some enzymes can only function with a cofactor present.
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2
Q
What is a cofactor
A
- A non protein molecule!
3
Q
What do co factors do
A
- The modify the the structure of the enzyme is some way so the enzyme can function more effectively
4
Q
What is an example of the way a co factor works
A
- Amylase catalyses the break down of starch to maltose
- This reaction can only occur if the co factor Chloride ions (CL-) ions are present
5
Q
What are the 3 types of co factors
A
- Prosthetic groups
- Coenzymes
- Activators
6
Q
What are prosthetic groups
A
- Prosthetic groups are molecules that form permanent attachments to an enzyme
7
Q
What is an example of a prosthetic group
A
- Haemoglobin
8
Q
What is haemoglobin
A
Haemoglobin has
- 4 polypeptide chains
- which are joined together by Disulfide bonds
- At the centre of each polypeptide chain is an iron containing group called haem (A prosthetic group)
- Each of these Haem prosthetic groups has an iron ion Fe2+
- As each Iron ion can bind with one molecule of oxygen (O2), there are 4 molecules of oxygen
- This protein combines with the prosthetic group forming a cojugated protein.
9
Q
What is the metabolic role of haemoglobin
A
- Haemoglobin picks up O2 in the lungs forming oxyhaemoglobin
- Oxyhaemoglobin is broken down (dissacociates) in the tissues giving up its oxygen, and then reverts back to haemoglobin.
10
Q
What cofactor does carbonic acid collaborate with
A
Carbonic anhydase collaborates with a zinc based co factor (ZN2+)
11
Q
What role does carbonic anhydrase play in the blood?
Car bon ic
An hy drase
A
- Carbonic anhydrase plays a critical function in the blood…
- Carbonic anhydrase catlyses the combination of water and dioxide
- Forming carbonic acid
- Which enables carbon dioxide to be transported in the blood
12
Q
What are co enzymes
A
- Co enzymes are smal nonprotein organic molecules are not permanently attached to the enzyme (Unlike prosthetic co factors)
13
Q
What do co enzymes do?
A
- Co enzymes help certain enzymes and substrates to bond with each other
- NB: Where a co enzyme is needed to catlyse a reaction, the enzyme can only function when it is present.
14
Q
What are many enzymes derived from
A
- Vitamins
- e.g. The coenzyme NAD is derived from the vitamin nicotinic acid
15
Q
A
16
Q
What is NAD the coenzyme for
A
- It is the coenzyme for a number of dehydrogenase enzymes
- It acts as a hydrogen receptor
17
Q
What are activators
A
- Activators are inogranic metal ions
- e.g. Magnesium Mg2+, Iron Fe2+, Calcium Ca2+
18
Q
What is the function of activators
A
- Activators form a temporary attachment to the enzyme…and change the active site….to increase the probability that a reaction will occur
19
Q
What are examples of activators
A
- Protein synthesis cannot occur without magnesium present as a co factor
- Muscle contraction and nerve impulses cannot happen without calcium present as a co factor
20
Q
Where do most metal activators come frome
A
- Diet
