Lecture 10

Question 1

What are the 3 cellular energy considerations

Answer 1

1. ATP (adenosine triphosphate)
2. Exergonic vs. Endergonic reactions
3. Change in free energy

Question 2

What is the role of enzymes?

Answer 2

catalyze biochemical reactions in a living organism, usually a protein

Question 3

What are enzymes made of?

Answer 3

Enzymes are made from living cells, but could still remain and function, once the cells from which they were made were broken down

Question 4

What are proteins manufactured from

Answer 4

manufactured from genes through the process of protein synthesis

Question 5

Enzyme size and fit

Answer 5

Enzymes are larger than the substances (substrates) upon which they act. Enzymes have a location known as the active or catalytic site where the substrates will fit.

Question 6

Catalysts

Answer 6

improve the efficiency of reactions. They speed up reactions that would otherwise occur in nature very slowly without these enzymes.

Question 7

How do enzymes help metabolism in cells? 2 ways

Answer 7

a. Enzymes lower the activation energy that is necessary to initiate a reaction.
b. Enzymatic reactions allow for energy to be released in increments, thus allowing for a more
efficient capture and usage of the energy.

Question 8

Can enzymes be recycled?

Answer 8

Yes

Question 9

active or catalytic site

Answer 9

Enzymes come into a close and
intimate 3D contact with their substrates at the active or catalytic site- this specific interaction is
sometimes described by a lock and key type hypothesis and as complimentary steric specificity

Question 10

allosteric sites

Answer 10

Enzymes have sites for chemical bonding away from the active or catalytic site. These sites are
known as allosteric sites.

Question 11

Competitive inhibitors

Answer 11

act to compete with the substrate at the active site

Question 12

non-competitive inhibitors

Answer 12

act at allosteric sites

Question 13

apoenzyme

Answer 13

protein portion

Question 14

cofactor

Answer 14

nonprotein portion

Question 15

The apoenzyme and the cofactor together make up

Answer 15

the complete and active whole enzyme known as a holoenzyme

Question 16

The cofactor can be

Answer 16

a metal ion, or if it is a low molecular weight and complex organic molecule it is called a coenzyme

Question 17

Metal ion such as? bind where?

what do they do?

Answer 17

such as iron, zinc, magnesium and calcium will bind at allosteric sites
Metal ion cofactors will bind to allosteric sites and alter the configuration of the active sites.

Question 18

Coenzymes bind?

Answer 18

will bind at the active or catalytic site

Question 19

Coenzymes assist the enzymes by and are derived from?

Answer 19

by accepting atoms removed by the substrate or

by donating atoms required by the substrate. Many coenzymes are derived from vitamins.

Question 20

NAD (nicotinamide adenine dinucleotide)

Answer 20

transfers hydrogen pairs (2H) and is derived from

the B complex vitamin, niacin

Question 21

FAD (flavin adenine dinucleotide)

Answer 21

transfers hydrogen pairs (2H) and is derived from the B

complex vitamin, riboflavin.

Question 22

CoA (coenzyme A)

Answer 22

transfers a 2 carbon unit (acetyl group) and is derived from the B complex vitamin, pantothenic acid

Question 23

Folic acid-transfers carbon

Answer 23

derived from the vitamin called THFA (tetrahydrofolic acid)

Question 24

PABA (para-aminobenzoic acid)

Answer 24

Bacteria uniquely need PABA (para-aminobenzoic acid) to make folic acid. Antibiotics known as sulfanilamides will block the activity of PABA, preventing the synthesis of folic acid and thereby inhibiting bacterial metabolism

Question 25

Enzyme activity can be affected by

does size affect it?

Answer 25

enzyme concentration, substrate (reactant) concentration,
product concentration, temperature and pH. Actual size variations amongst different enzymes have little effect on enzyme activity

Question 26

oxidoreductase group

Answer 26

An enzyme class known as the oxidoreductase group is involved in oxidation and reduction reactions

Question 27

An oxidation reaction results in

Answer 27

the loss of hydrogens, loss of electrons, or the gain of oxygen

Question 28

A reduction reaction results in

Answer 28

the gain of hydrogens, gain of electrons or the loss of oxygen

Question 29

A dehydrogenase is a

Answer 29

type of oxidoreductase enzyme that removes hydrogen

Question 30

Enzyme control at the level of synthesis (formation)

Inducible enzymes

Answer 30

Some enzymes are only made in the presence of their substrates. These are known as inducible (adaptive) enzymes.

Question 31

Repressible enzymes

Answer 31

are no longer made when specific products of a reaction are present in appropriate amounts.

Question 32

Where are repressible and unducible enzymes controlled

Answer 32

Induced and repressed enzymes are controlled at the gene level.

Question 33

When are genes on and off

Answer 33

Genes are turned on (enzymes are made from protein synthesis process) to produce inducible enzymes, while genes are turned off (enzymes are not made from protein
synthesis process) to not produce repressible enzymes.

Question 34

Enzyme control of pre-synthesized (constitutive) enzymes

Answer 34

the activities of pre-synthesized (already present in the cell) enzymes can be controlled through competitive and noncompetitive inhibition.

Question 35

In competitive inhibition

Answer 35

the inhibitor is generally an organic compound that resembles the substrate. It will fight or compete for the active (catalytic) site. The effectiveness of the inhibitor is related to the concentration of the inhibitor, the concentration of the substrate and the relative affinity (ability to bind) of the enzyme to the substrate or the inhibitor

Question 36

In noncompetitive inhibition

Answer 36

the inhibitors react with the allosteric sites, and look
nothing like the original substrate. In feedback (end-product) inhibition, final products of a reaction will bind on allosteric sites of an original enzyme in the reaction chain to shut down a reaction. In branched pathways, the product will generally inhibit the activity of the first unique enzyme in the pathway. This will shut down the unneeded
branch.