8.1 (Metabolism)

Question 1

Define metabolism.

Answer 1

The sum total of all chemical reactions that occur within an organism

Question 2

What are metabolic pathways?

Answer 2

Cycles or chains of enzyme catalysed reactions

Question 3

What is activation energy?

Answer 3

The initial input of energy that is required to trigger a chemical reaction.

Question 4

How do enzymes lower the activation energy of a reaction?

Answer 4

• The substrate binds to the enzymes’ active site and the active site is altered to reach the transition state.
• Due to the binding the bonds in the substrate molecule are stressed/become less stable.
• The binding lowers the overall energy level of the transition state.
• The activation energy of the reaction is therefore reduced.

Question 5

What is an inhibitor?

Answer 5

• A molecule that binds to an enzyme and slows down or stops the enzyme’s function.

Question 6

What is compettiive inhibition?

Answer 6

• Fits in the active site preventing the substrate from entering.
• The higher the concentration of the inhibitor, the slower the rate of reaction.

Question 7

What is non-competitive inhibition?

Answer 7

• Fits into an allosteric site causing a conformational change in the active site so the substrate cannot attach to react.
• As the concentration of inhibitor increases, the rate of reaction decreases as there are fewer functional active sites available for reaction.
• The maximum rate of reaction is also reduced

Question 8

Outline an example of competitive inhibition.

Answer 8

Alcoholism:

• Antabuse competes with the aldehyde oxidase and prevents the acetaldehyde from being converted to acetic acid
• A build up of acetaldehyde follows, resulting in a strong feeling of nausea ad other strong hangover symptoms- a good deterent from drinking
• Antabuse is administered as a daily pill so its efficacy relies on the patient’s own motivation- if they stop taking it, they can drink again

Question 9

Outline an example of non-competitive inhibition.

Answer 9

ACE Inhibitors:

• The RAA system causes vasoconstriction (tightening of blood vessels) when blood pressure drops (such as after heavy bleeding)
• In people with hypertension or heart failure, the action of angiotensin II can make their problem worse
• ACE inhibitors are medications that inhibit angiotensin converting enzymes- they prevent increased blood pressure

Question 10

What is feedback inhition?

Answer 10

• Bacteria synthesize isoleucine from threonine in a series of five enzyme-catalysed steps
• As the concentration of isoleucine increases, some of it binds to the allosteric site of threonine deaminase
• Isoleucine acts as a non-competitive inhibitor to threonine deaminase
• The pathway is then turned off, regulating isoleucine production.
• If the concentration of isoleucine later falls (as a result of its use) then the allosteric sites of threonine deaminase are emptied and the enzymes recommences the conversion of threonine to isoleucine takes place.

Question 11

What is bioinformatics?

Answer 11

An approach whereby multiple research groups can add information to a database enabling other groups to query the database.
* Sometimes when a chemical binds to a target site, it can significantly alter metabolic activity.
* Massive libraries of chemicals are tested individually on a range of related organisms.
For each organism a range of target sites are identified.
* A range of chemicals which are known to work on those sites are tested.