8.1 Metabolism

Question 1

What is the site called on an enzyme where non-competitive inhibitors can bind to?

Answer 1

Allosteric

Question 2

What do metabolic pathways consist of?

Answer 2

chain reactionsand cycles and enzyme-catalysed reactions

Question 3

How do most chemical changes occur?

Answer 3

Through a metabolic pathway in a sequence of small steps where some form organic compounds (anabolic) and some break down (catabolic)

Question 4

What is an example of a metabolic chain reaction?

Answer 4

glycolysis: chain of 10 enzyme controlled reactions, converts glucose to pyruvate

Question 5

Give an example of a metabolic pathway that forms a cycle

Answer 5

Krebs cycle (respiration); Calvin Cycle (photosynthesis)

Question 6

What is activation energy?

Answer 6

energy needed for a reaction to occur, so that substrates pass a certain transition state to form products;

Question 7

How does an enzyme catalyse a reaction?

Answer 7

substrate binds to active site;
substrate is altered by breaking or weakening bonds of substrates;
lowering activation energy;
reaches transition state faster;
converts to product and released;
rate of reaction increases;

Question 8

In most biological reactions, is the energy released greater or smaller?

Answer 8

greater (products are most stable)

Question 9

When does the conformation of an enzyme change?

Answer 9

As substrate binds to active site, conformation alters/shape of active site becomes complementary to substrate;
when substrate is released enzyme returns to original conformation

Question 10

What are inhibitors?

Answer 10

chemical substances that bind to enzymes to reduce the activity

Question 11

What are competitive inhibitors?

Answer 11

substrate and inhibitor are chemically similar;
inhibitor binds to active site of enzyme;
blocks substrate from binding to active site;
enzyme activity is prevented until inhibitor dissociates

Question 12

What are non-competitive inhibitors?

Answer 12

substrate and inhibitor are not similar;
inhibitor binds to allosteric site (not active);
changes conformation of enzyme;
enzyme may stop catalysing/catalyse slower

Question 13

How is rate of reaction of an enzyme affected by competitive inhibitor as substrate concentration increases.

Answer 13

as substrate concentration increases, substrates become increasingly more likely to bind to active site because inhibitor only blocks the site temporarily

Question 14

How is rate of reaction of an enzyme affected by non-competitive inhibitor as substrate concentration increases.

Answer 14

Substrate cannot prevent the binding of inhibitor (even at high concentration); same proportion of enzymes is inhibited at all substrate concentrations

Question 15

What are allosteric interactions?

Answer 15

enzymes regulated by inhibitors binding to special sites on the enzyme away from the active site

Question 16

What is end-product inhabitation?

Answer 16

when in a metabolic pathway, product of last reaction of pathway inhibits enzyme that catalysis first reaction;
negative feedback loop

Question 17

What is the advantage of end product inhabitation?

Answer 17

if there is excess of end product the whole pathway is switched off with no intermediates (to reach equilibrium)

Question 18

Example of end product inhabitation

Answer 18

amino acid threonine is converted to isoleucine; when isoleucine builds up it acts as inhibitor

Question 19

What is bioinformatics?

Answer 19

approach whereby multiple research groups can add information to database enabling other groups to query the database

Question 20

Example of bioinformatic technique for metabolic pathway research

Answer 20

chemogenomics