CH 3 - Glycolysis/Krebs, ETC

Question 1

Glycolysis Pathway

Answer 1

1. Hexosphase (2ATP –> 2PO4)
   a. Phosphorylation converts glucose to glucose 6 phosphate
   b. Isomerization converts glucose 6 phosphate to fructose 6-phosphate
   c. Fructose 6-phosphate is converted into fructose 1,6 biophosphate
   d. Fructose 6-phosphate is split into DHAP and (2)3 phosphorglyceraldehyde
   e. (2)3 phosphorglyceraldehyde converted into (2)1,3 biphosphoglycerate
   f. (2)1,3 biphosphoglycerate converted to (2)3 phosphoglycerate
   g. (2)3 phosphoglycerate converted into (2)phosphoglycerate
   h. (2)phosphoglycerate converted into (2)phosphoenolpyruvate
   i. (2) pyruvate
   j. (2) pyruvate converted into into lactate or krebs cycle

Question 2

How is ATP made? (2 ways)

Answer 2

1. anaerobic (no oxygen)
2. aerobic (oxygen present)

Question 3

Purpose of hexokinase

Answer 3

Traps glucose in the cytosole

Question 4

Purpose of phosphofructose kinase (POK)

Answer 4

Rate limiting enzyme

Question 5

Role of lactate dehydrogenase

Answer 5

converts pyruvate into lactate

Question 6

What is created in glycolysis?

Answer 6

2 net ATP made (2 produced, 4 consumed)
2NAD –> 2NADH + H+

Question 7

Is glycolysis catabolic or anabolic?

Answer 7

Glycolysis is catabolic because it is breaking down carbohydrates (sugar)

Question 8

Where does glycolysis take place? Does it need oxygen?

Answer 8

Takes place in the cytosol and does not need oxygen

Question 9

Why can you argue that Krebs INDIRECTLY needs oxygen?

Answer 9

Because oxidative phosphorylation is necessary for regeneration of the hydrogen free form of these coenzymes (NADHs), Krebs can only operate under aerobic conditions

Question 10

Where is ATP produced throughout the glycolysis-Krebs-oxidative phosphorylation pathway?

Answer 10

A net gain of two ATP molecules occurs by substrate level phosphorylation during glycolysis and two more are formed during the Krebs cycle from GTP, one from each of the two molecules of pyruvate entering the cyle. The majority of ATP molecules glucose catabolism produces - up to 34 ATP per molecule - from during oxidative phosphorylation from the hydrogens generated during glucose breakdown

Question 11

What is the purpose of lactate?

Answer 11

Lactate can diffuse out of the cell and will do so when the concentration of glucose rises

Question 12

What is the terminal compound of Glycolysis?

Answer 12

pyruvate

Question 13

What are two ways to get Acetyl CoA?

Answer 13

Pyruvate or from the breakdown of fatty acids and some amino acids

Question 14

What is the role of citrate syntase?

Answer 14

Produces carbon dioxide, intermediates that generate hydrogen atoms

Question 15

What comes first ? electrons bound to oxygen or protons through the ATPase

Answer 15

Protons through the ATPase

Question 16

Purpose of oxygen in ETC?

Answer 16

Oxygen is the final electron receptor that creates metabolic water and allows NAD to be oxidized. In the presence of oxygen, a cell breaks down glucose to yield carbon dioxide and water, and energy is released. The remainder of the energy is transferred to the nucleotide adenosine triphosphate (ATP).

Question 17

Purpose of Glycogen phosphorylase

Answer 17

Removes one glucose from glycogen and adds a phosphate to the glucose. Acts when there is a high concentration of ADP

Question 18

Difference between Gluconeogenesis and Glyconeogenesis

Answer 18

Gluconeogenesis = generation of new glucose from non-carbohydrate sources.
Glyconeogenesis = generation of glucose and glycogen from non-carbohydrate sources.

Question 19

How is glucose stored and why is it stored that way?

Answer 19

Stored as glycogen to save ‘space’ as glycogen molecules do not attract massive amounts of fluid (Le Chatelier’s principle) and therefore are efficient in storage. Glycogen is “one” molecule from the perspective of osmotic force while glucose is “many”

Question 20

If the weight of pyruvate is 88, what is the molecular weight of lactate?

Answer 20

90da because lactate has two more hydrogens than pyruvate

Question 21

How can a lack of oxygen compromise how enzymes work?

Answer 21

Lack of oxygen requires the cell to use the lactate pathway. When lactate begins to build up, the pH of the cell is impacted and, therefore compromises enzyme function

Question 22

Why is Krebs so important if it only makes a little bit of ATP?

Answer 22

You need to go through Krebs to get to oxidative phosphorylation, which then gives you a ton of ATP

Question 23

Role of glucokinase

Answer 23

Enzyme that helps regulate blood sugar levels by sensing blood glucose levels and stimulating insulin release

Question 24

What is the importance of citrate synthase?

Answer 24

Citrate synthase catalyzes the first step of the kreb cycle by using water to convert a 4 carbon molecule into acetylcoenzyme

Question 25

What is the goal of the Krebs cycle?

Answer 25

The goal of the Krebs cycle is to create ATP and release CO2.

Question 26

What is the goal of the electron transport chain? Where are the NADH and FADH2 coming from?

Answer 26

ETC uses the energy to create ATP. NADH and FADH2 are coenzymes that were produced in the Kreb’s cycle

Question 27

What is the importance of cytochrome oxidase? What happens if cytochrome oxidase is dysfunctional? No oxygen?

Answer 27

Cytochrome oxidase breaks up oxygen. If cytochrome oxidase is dysfunctional, metabolic water cannot be created. If there is no oxygen there will be a build up of lactate.

Question 28

What drives ATP synthesis and how do the cytochromes play a role in this?

Answer 28

The movement of hydrogens from the intermembrane space into the matrix through ATP synthase converts ADP to ATP. The cytochromes carry electrons from one membrane bound enzyme to another.

Question 29

What are the two enzymes that play a role in making glycogen or breaking down glycogen?

Answer 29

Glycogen phosphorylase (GP) which adds a phosphate and glycogen synthase (GS) which removes a phosphate

Question 30

Why do we store excess glucose as glycogen?

Answer 30

Glycogen is a storage of carbohydrates