Lecture 10: Redox Reactions and Glycolysis

Question 1

What is end product inhibition?

Answer 1

When the end product of a metabolic pathway is the allosteric inhibitor, that binds to and inhibits the first enzyme of the metabolic pathway.

Question 2

What is competitive inhibition?

Answer 2

-When a molecule that looks similar to a substrate binds to the active site and blocks the binding of the substrate that is meant to bind to the active site.

Question 3

What does competitive inhibition do?

Answer 3

• Inhibits the catalysis of the substrate

Question 4

When does competitive inhibition occur?

Answer 4

When you take DRUGS

Question 5

What is allosteric regulation?

Answer 5

-When a regulatory molecule binds to an enzyme on a spot other than the active site and induces a conformational change to the enzyme preventing it from catalyzing reactions further

Question 6

Why is allosteric regulation more effective than competitive inhibition?

Answer 6

-If you have an enzyme with allosteric inhibition you only need one inhibitor per enzyme. Also molecules can be a variety of shapes and do not need to replicate the shape of the substrate.
- With competitive inhibition you need the same number of competitive inhibitors as there are enzymes in order for it to stop catalyzing

Question 7

Why is feedback inhibition good?

Answer 7

-Prevents the waste and over production of products
-Allows cells to control the amount of a specific compound

Question 8

Why is it beneficial to regulate the first enzyme of the metabolic path?

Answer 8

The first enzyme is the one that is regulated to avoid a waste of resources or producing any unnecessary intermediates, also avoids waste of energy and resources

Question 9

What is cooperativity with enzymes?

Answer 9

-Occurs with two or more identical enzyme subunits forming an enzyme complex

Question 10

How does cooperativity with enzymes occur?

Answer 10

-When an inhibitor binds to the first enzyme and changes the first enzyme’s conformation this conformational change influences the other subunits of the enzyme to undergo a partial conformation change making the inhibitor of the other enzymes more easily able to bind .
-This helps rapidly shut down the enzyme

Question 11

What type of curve does the cooperativity of enzymes produce?

Answer 11

A sigmoid curve

Question 12

Why are the first enzymes in metabolic pathways usually made up of multiple subunits?

Answer 12

First enzymes are usually multiple subunits and regulated by cooperative allostery because when there are more subunits the enzyme is able to be inhibited more rapidly

Question 13

What is the equation for the metabolism of glucose?

Answer 13

C6H12O6 + 6O2 —– 6CO2 + 6H2O + Free Energy

Question 14

Why is glycolysis split into multiple steps?

Answer 14

-In order to harvest some of the energy in the form of ATP
-If it was done in one step the energy would all be released as heat

Question 15

How much energy is harvested into ATP during glycolysis and how much is released as heat?

Answer 15

-About half of the energy that is released during the oxidation of glucose is converted into ATP
-The other half is still released as heat

Question 16

What is the heat released from glycolysis used for?

Answer 16

-To help drive each step of glycolysis

Question 17

What is the most important reaction in glycolysis?

Answer 17

Redox reaction

Question 18

What is reduction?

Answer 18

molecules gains an electron or hydrogen molecule

Question 19

What is oxidation ?

Answer 19

molecule loses an electron or hydrogen molecule

Question 20

How to recognize oxidation reactions?

Answer 20

-Oxidation occurs whenever a C-H bond is lost

Question 21

what molecules are often oxidized? and why?

Answer 21

-Fats
- Oils
-Fossil Fuels
Because they are made up of many C-H bonds and have lots of energy

Question 22

What molecule is fully oxidized?

Answer 22

Carbon dioxide

Question 23

What is NAD and its function?

Answer 23

• An essential electron carrier in cellular redox reactions
• Stores and Carries electrons

Question 24

What is the oxidized and reduced version of NAD?

Answer 24

Oxidized: NAD+
Reduced: NADH

Question 25

Why are energy carrier used?

Answer 25

Allows the process of glycolysis to be broken down into multiple steps and for energy to be released more gradually so that it is more easily harnessed.

Question 26

How is NADH oxidized after glycolysis?

Answer 26

With O2 as an electron acceptor

Question 27

What is redox potential?

Answer 27

The tendency of a molecule to lose/gain electrons

Question 28

What do redox potential tables show?

Answer 28

-Where electrons will flow to

Question 29

What does higher on the redox table mean?

Answer 29

Higher on the table means that the electron will flow to that molecule -Oxygen is highest on the table which is why electrons flow from sugar to oxygen

Question 30

What is the first step of cellular respiration?

Answer 30

Glycolysis

Question 31

Where does glycolysis occur?

Answer 31

Cytoplasm

Question 32

What are the two phases of glycolysis and what steps do they include?

Answer 32

Phase 1(Steps 1-5): Energy investment phase Phase 2(Steps 6-10): Energy payoff phase

Question 33

What is the final molecule of the energy investment phase?

Answer 33

G3P

Question 34

How is ATP created during glycolysis?

Answer 34

Substrate-level phosphorylation

Question 35

How many ATP molecules are invested in glycolysis and how many are made and net total?

Answer 35

Invested: Two ATPs Created: Four ATPs Net Total: Two ATPs

Question 36

What is the end product of glycolysis?

Answer 36

Two pyruvate molecules

Question 37

What are all of the products of glycolysis?

Answer 37

-2 Pyruvate -2 NADH -2 ATP

Question 38

What is the key step of glycolysis?

Answer 38

-The reduction of NAD+ to NADH

Question 39

Steps 2-3 and 4-5 have a positive delta G but no ATP is invested, how do they occur?

Answer 39

-For sequential reactions the delta G values are additive -FBP to G3P step 4-5 is very unfavorable but since step 5-6 that directly follows G3P to BPG is very favorable and takes away all of the G3P molecules(lowers concentration). It reduces the concentration so much so that the step 4-5 actually becomes favorable. -Metabolic reactions are generally pulled by one reaction that is favorable and pulls all of the other reactions along because it takes away the products of the previous reaction

Question 40

How much energy total(heat and captured) is released from the complete oxidation of glucose?

Answer 40

-686 kcal/mol

Question 41

What happens to C-H and C-O bonds during oxidation?

Answer 41

C-H bonds: decrease C-O bonds: increase

Question 42

What is used to generate the phosphate bond in ATP?

Answer 42

Hydrolysis of the "higher-energy phosphate bonds" is used to generate the phosphate bond in ATP

Question 43

Why is it called substrate level phosphorylation?

Answer 43

Because the phosphate is transferred from the substrate directly to ADP

Question 44

What is oxidative phosphorylation?

Answer 44

Where free phosphate is combined with ADP by the ATP synthase enzyme

Question 45

What does pyruvate become?

Answer 45

Acetyl CoA

Question 46

Why is acetyl CoA considered an energy carrier?

Answer 46

It contains a C-S bond which is a "high energy bond"

Question 47

Why is acetyl-coA such an important molecule?

Answer 47

Sugars, fats and man amino acids are all broken down into acetyl-coA -Acetyl-coA is the building block for making fats and other metabolites