Glycolysis

Question 1

what occurs in glycolysis

Answer 1

Glucose (sugar transported in the blood – 6 carbon) -> two 3 carbon units (pyruvate and ATP

Question 2

catabolism and anabolism

Answer 2

• Metabolic pathways can be categorised as anabolic or catabolic

Question 3

catabolism

Answer 3

• degradative path ways
• Usually energy yielding
• Converge to a few end products

Question 4

anabolism

Answer 4

• biosynthetic pathways
• Energy-requiring
• Diverge to synthesize many biomolecules

Question 5

where does the energy for anabolism come from

Answer 5

• Solar energy- photoautotrophs

- Catabolism- heterotrophs

Question 6

linking anabolism and catabolism

Answer 6

ATP

• Produced by light (phototrophs) or catabolism (heterotrophs)
• Used to drive biosynthetic reactions (anabolism) motility etc.

Question 7

what is ATP

Answer 7

is the energy ‘currency’ of the cell

ATP = adenosine triphosphate

Question 8

oxidation/reduction in metabolism

Answer 8

• Catabolism is oxidative. Substrates lose reducing equivalents, usually H- ions (H+ ions plus electrons) or NAD+ collects electrons released in catabolism
• Anabolism is reductive. Substrates gain reducing equivalents
  NAD(P)H provides the electrons for anabolic processes
  NAD(P)+/NAD(P)H can be viewed as a redox energy currency

Question 9

NAD(P)H

Answer 9

provides the electrons for anabolic processes

Question 10

NAD(P)+/NAD(P)H

Answer 10

can be viewed as a redox energy currency

Question 11

releasing energy from glucose

Answer 11

• Potential energy in glucose is contained in the reduced hydrocarbon bonds

To use this energy glucose must be oxidised to co2 and water

• Arises in the blood from- breakdown of poly or di- saccharides & Syntheses form from non- carbohydrate sources
• Enters cell by specific glucose transporters
• Enzymes involved in glycolysis located in cytosol- glucose (6C) -> two 3c units (pyruvate) and ATP

Question 12

3 stages of glycolysis

Answer 12

1. Glucose is destabilised (requires energy- energy investment)
2. The hexose molecule is cleaved into 2 three carbon molecules
3. ATP (energy) Is generated
   (2 and 3 may be combined in some schemes)

Question 13

Phosphofructokinase

Answer 13

catalyses the committed step in glycolysis, is the most important control site. Rate limiting step. If you don’t need ATP then you inactivate the phosphofructokinase. Once you add it at that stage you are committed and cant go back to glucose.

Question 14

overall reaction of glycolysis

Answer 14

GLUCOSE + 2NAD+ + 2ADP + 2Pi  2NADH + 2PYRUVATE + 2ATP + 2H2O + 2H+

• NAD+ IS THE MAIN OXIDISING AGENT IN GLYCOLYSIS, IT MUST BE REGENERATED
• ANAEROBIC CONDITIONS – PYRUVATE REDUCED TO LACTATE GENERATES NAD+ FROM NADH
• IN AEROBIC CONDITIONS, NADH OXIDISED IN THE MITOCHONDRIA TO YIELD ATP

Question 15

metabolic posioning

Answer 15

aresenic poisoning

Question 16

he two forms of inorganic arsenic

Answer 16

reduced (trivalent As (III)) and oxidized (pentavalent As(V)), can be absorbed, and accumulated in tissues and body fluids.

Question 17

The poison Arsenic (As[V])is structurally very similar to what?

Answer 17

• phosphate, the P part of ATP (the molecule that cells use as immediate energy)

Question 18

arsenic poisoning

Answer 18

• Arsenic poisoning can either be acute (from one big dose), or chronic (the old something-in-the-nightly-cocoa routine).
• Arsenic has the same effect on insects, so it’s used in agricultural insecticides, and in treated-wood (like on a deck).
  It takes the place of what?
• phosphate, blocking the step in ATP formation that traps the energy from respiration.

Question 19

In normal conditions (arsenic poisoning)

Answer 19

• glyceraldehyde-3-phosphate (3C) is converted to 1,3-bisphosphoglycerate.
• 1,3 bi(s)phosphoglycerate is then converted to 3-phosphoglycerate, releasing one molecule of ATP.
• However, when there is an arsenate,
• glyceraldehyde-3-phosphate is converted to 1-arseno-3-phosphoglycerate, an analogue of 1,3-bi(s)phosphoglycerate.
• This analogue hydrolyses non-enzymatically into
  3-phosphoglycerate to release arsenate back with no release of ATP.
• The overall result is that no net ATP is formed.
• Normally, 4 molecules of ATP are formed per glucose molecule; 2 ATP molecules at the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate and 2 ATP molecules at the conversion of phosphoenolpyruvate to pyruvate.
• However, two molecules of ATP are used; one at phosphorylation of glucose molecule and one at phosphorylation of fructose-6-phosphate.