Chapter 4: Enzymes and Energy

Question 1

Discuss enzymes.

Answer 1

• biological catalysts that increase rate of chemical rxns by lowering energy required for rxn to take place
• have highly ordered 3D shape that allows substrates to come in and produce a products
• have pockets called activation sites into which substrates fit and form an enzyme-substrate complex
• Rxn occurs; products dissociate; enzyme is unaltered!
• The rate at which enzymes works depends on several factors such as temp and pH
• They have optimal temp and pH ranges and that usually correlates to norms of the body (i.e. temp 98.6; pH depends on where in the body they are working)
• Enzyme names end in “-ase”
• sometimes you’ll have a cofactor bind to help change the shape of the active site to aid in temporary bonding between enzyme and substrate

Question 2

Discuss the effect of substrate concentration.

Answer 2

• Rate of production formation increases as substrate concentration increases until rxn reaches a plateau at which time the enzyme is said to be “saturated”
• Plateau occurs because at some point all the enzymes are busy at the same time so substrate has to wait until an enzyme is free

Question 3

Discuss the Law of Mass Action.

Answer 3

• direction of rxn is from side of equation where concentration is higher to side where concentration is lower until equilibrium is reached.
• if you increase the amount of stuff on the left side of the rxn it will drive it to the right but if you increase the ant of stuff on the right side of the equation it will drive it left.

H2O + CO2 H2CO3

Question 4

Discuss end-product inhibition.

Answer 4

• one pathway becomes favored over another
• You have a branched metabolic pathway and one pathway accumulates enough product so it sends a signal to the point where the pathway branches and causes the enzyme to change shape so the rxn will favor the other pathway (this is how negative feedback look works)

Question 5

Discuss metabolic pathways.

Answer 5

-Sequences of enzymatic rxns that begin with an initial substrate, progress through intermediates, and end with a final product

Question 6

Discuss the 1st and 2nd laws of thermodynamics.

Answer 6

1st law: energy cannot be created nor destroyed

2nd law: energy transformations increase entropy (degree of disorganization of a system)

Question 7

Discuss the difference between endergonic and exergonic reactions.

Answer 7

Endergonic Rxns:

• require INPUT OF ENERGY to proceed
• creates less (decreases) entropy
• formation of ATP

Exergonic Rxns:

• RELEASE energy as the proceed
• creates more (increases) entropy

Question 8

Discuss Oxidation and Reduction.

Answer 8

• Reduced if molecule GAINS an electron
• Oxidized if molecule loses an electron
• Reducing agent donates electron
• Oxidizing agent accepts electron (oxygen great at this)
• Oxidation and Reduction are always coupled runs
• Many molecules can be both a reducing agent and an oxidizing agent in chain rxn where e- are passed along
• NAD (as oxidizing agent) becomes reduced when it accepts e- (or H+)
• NADH (as reducing agent) becomes oxidized when it donates e- (or H+)

Question 9

Discuss coenzymes.

Answer 9

• work to transport Hydrogen atoms and other small molecules from one enzyme to the next to facilitate enzyme activity
• examples of coenzymes: NAD and FAD

Question 10

NAD and FAD

Answer 10

• from B vitamins
• NAD can accept 2 e- and 1 proton = NADH+H+
• FAD can accept 2 e- and 2 protons = FADH2