Enzymes

Question 1

Enzymes

Answer 1

Catalytic proteins which allow many chemical reactions within homeostasis constraints of a living system

Most are proteins except RNA

Catalyst doesn’t impact delta G, impacts free energy of activation at a moderate temperature (activation energy, Ea, energy that must be overcome for the reaction to take place)

Without enzymes, chemical traffics of various pathways of metabolism would become totally blocked

Ends often in “ase”

Are substrate specific.

Question 2

Why is activation barrier essential for life

Answer 2

Proteins, DNA, etc are rich in free energy (G). Without Ea, everything would react (Ex ATP into ADP) fall apart

Question 3

Enzyme reactions

Answer 3

Binds on the substrate or substrates

While they are joined, catalytic actions of the enzyme converts substrate to product

Question 4

Induced fit

Answer 4

Substrate fitting in enzyme induces a conformation change in the enzyme

Enzyme (proteins) can move thanks to H bonds

Activation energy is lowered

Substrates are converted into products, which don’t fit so well in the enzyme and are released

Question 5

Cofactors

Answer 5

Non protein component of enzyme, inorganic

Usually metal ions (Fe, Mg, Zn (all 2+ )

Does not bind to active site

Question 6

Coenzyme

Answer 6

is Organic

Bind to Part of the active site

Derived from vitamins

Question 7

Enzyme activity depends on

Answer 7

1. Cofactors
2. Substrate concentration
3. The enzyme’s intrinsic affinity for the substrate (Km)
4. Temperature
5. pH
6. Regulation

Question 8

Concentration of enzyme and substrates

Answer 8

More enzymes means faster reaction

More substrate will go faster until it plateaus, enzymes are saturated

All active sites are occupied

Plateau is called v max

Question 9

Km and vmax

Answer 9

Vmax is the plateau rate

Km is half the poteau rate

Low km has high affinity for the substrate, will often be saturate, so variation of substrate concentration will not vary a lot
And opposite, if high km, low affinity and substarte concentration will matter more

Question 10

Physical conditions that influence enzyme activity

Answer 10

Anything that affects the bond (hydrogen, salt bridge, etc) that holds the substrate and the enzyme will affect enzyme activity

Each enzyme has optimal pH, temperature, and depends on where enzymes functions

Question 11

Thermal enzymes

Answer 11

Responsible for distribution of colour in Siamese cats

Enzymes are only active at a certain temperature (so nose gets dark)

Question 12

pH

Answer 12

Optimal pH

Changes enzyme activity because of denatures (low ph, carbonyl groupe gains an H, high ph, amino group lose ph

Question 13

Irreversible inhibition:

Answer 13

Competitive inhibition that doesn’t unbind, ex penicillin

Question 14

Allosteric control

Answer 14

molecule causes a change in enzyme shape by bonding to the enzyme at a location other than active site, activates or deactivates enzyme

Binds away from active site

Inhances or dehances, all have quaternary structure

Fixes enzyme in catalycally active or inactive position

Can be finely regulated

ex: Atp to adp is constantly changing , so ratio of atp/adp is always changing, so high adp levels causes adp to bind to enzyme which changes catalyser to activates it to produce atp, not necessary at the moment so no energy wasted

Cooperatively:

Bonding of 1 out of 4 oxygens in hemoglobin will help the binding of the second, and the third, and etc

Question 15

Concentration enzyme

Answer 15

Regulating of enzyme activity by changing enzymes concentration or maintaining a stock of inactive enzymes and activating them when needed

Pool of enzyme that is activated when needed

Question 16

Competitive inhibition:

Answer 16

molecule similar in size and shape or substrate competes with the substrate for the active sire. Takes mores substrate to reach v max, doesnt affect km

Question 17

Non competitive inhibition:

Answer 17

an inhibitor binds to the enzyme away from the active site altering the conformation of the active site so it no longer functions as good

increases km, lowers vmax

Question 18

susbtrate meaning

Answer 18

reactant an enzyme acts on

Question 19

types of mechanisms of enzyme action

Answer 19

1- two or more reactants, enzyme will act as a template in order to bring the substrates together in a p specific orientation to encourage a reaction between them

2-enzyme bends and stretches bonds to be broken, making them break easier, reducsing amount of themal energy it must be absorbed to get the reactants to transition state

3-enzyme provides a microenvironment to a particular type of reaction (ex acidic environment in a neutral cell)

Question 20

Regulation of enzyme

Answer 20

Non competitive, competitive inhibitor
allosteric control