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BIOC 221 - Metabolism > Glycolysis and PPP > Flashcards

Glycolysis and PPP Flashcards

1
Q

Why is glucose phosphorylated in the first step?

A

To trap glucose in the cell and prevent it from leaving

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2
Q

What are 2 ways glucose can be stored?

A

glycogen in the muscles and fat in adipose tissue

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3
Q

What makes a reaction favorable/unfavorable in terms of deltaG, deltaH, keq?

A 
Favorable = - deltaG, - deltaH, >1.0 keq, catabolic usually
Unfavorable = +deltaG, +deltaH, <1.0 keq
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4
Q

Why do cancer cells take up so much glucose?

A

Cancer cells occur in anaerobic tissues. They do not have as many mitochondria (cite of CAC and ETC). Because they cannot run CAC or ETC, which produce a lot of energy for cells, they have to get all of their energy from glycolysis. This means they will perform a LOT of glycolysis and 10x faster than most cells to get the energy they need.

Cancer cells are also rapidly reproducing and growing, which means insane amount of energy is constantly required.

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5
Q

Where does glycolysis occur?

A

The Cytoplasm of cells, in all cells

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6
Q

An enzyme that phosphorylates is called a ___________?

A

Kinase

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7
Q

Which reactions in glycolysis are regulated?

A

Irreversible kinase reactions, where phosphorylation occurs (and ADP –> ATP).
There are 4 of these in glycolysis.

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8
Q

What charge does aldolase (a Schiff base) have?

A

Positive. It acts as an electron sink when opening the Fruc. 1,6-bisP ring.

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9
Q

Why is substrate channeling faster?

A

Eliminates diffusion of products/substrate. Seen in steps 6 and 7 (stuck together = allows for favourable reaction). Don’t have to wait for a molecule to diffuse through a membrane.

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10
Q

If deltaG is close to 0, what drives a reaction?

A

Mass action, Q, Keq

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11
Q

Match the following:

Catabolism and anabolism
to
Oxidation and reduction

A

Catabolism –> Oxidation
Anabolism –> Reduction

(Remember LEO says GER)

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12
Q

H+ plus 2 e-

A

Hydride

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13
Q

H+

A

Proton

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14
Q

H+ plus e-

A

Hydrogen

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15
Q

NAD+ plus _____ = NADH

A

H- or hydride

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16
Q

2 NADH = how many e- ?

A

2 NADH = 4 e-

because 2 NAD+ plus 2 H- (2H- = 2H+ plus 4e-)

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17
Q

What happens to the 2 NADH that gets produced in glycolysis?

A

the 2 NADH drops off 4e- in the ETC (aerobic) which regenerates 2 NAD+

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18
Q

How much energy, out of the total energy of glucose, does glycolysis yield?
Where is the rest of it stored?

A

5%, the rest of glucose’s energy remains in pyruvate. We will see the rest of glucose’s energy in reactions like CAC and ETC.

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19
Q

Where does lactate go after it’s produced in the muscle?

A

Lactate goes to the liver to be dealt with. This takes time. Lactate will turn back into 1/2 glucose in the liver.

20
Q

What is the aerobic fate of pyruvate?

A

Pyruvate goes through the PDH to yield Acetyl-CoA (NADH and CO2 are produced in the process)

21
Q

What are the anaerobic fates of pyruvate?

A

Pyruvate —Lactate dehydrogenase—–> Lactate
(NAD+ produced in the process)
Pyruvate —–pyruvate decarboxylase—> Acetaldehyde —-alcohol dehydrogenase—> ethanol
(CO2 and NAD+ produced in the process)

22
Q

What is a redox reaction?

A

A transfer of electrons between two species/molecules

23
Q

What do we call enzymes that perform redox reactions?

A

Dehydrogenase

24
Q

Why is acetaldehyde so toxic?

A

Can react with amino groups, proteins, compete for vitamin uptake carriers

25
Q

When does the pentose phosphate pathway perform Non-oxidative (anaerobic) cycle?

A

When NADPH is needed

26
Q

When does the pentose phosphate pathway present the oxidative (catabolic) pathway?

A

To form nucleotides, coenzymes, DNA, RNA

27
Q

How does the cell prevent the waste of energy (3):

A
  1. Substrate concentrations
  2. Reciprocal regulation
  3. Compartmentalization
28
Q

Define reciprocal regulation

A

Spontaneous reactions that use specific enzymes to ensure that futile cycling does not occur so that catabolism and anabolism don’t occur at the same time (see glycolysis and gluconeogenesis)

29
Q

Which regulation method is the fastest, which is the slowest?

A

Fastest: Substrate availability (nanoseconds)
Slowest: Second messenger signalling (mins to hrs) = hormone regulation

Allosteric regulation takes microseconds

30
Q

Why does a cell need regulation? (2)

A
  1. Cell requires constant [ATP] and [precursors] for biosynthesis
  2. Anabolism and catabolism use the same enzymes reversibly. Regulating enzymes (enzymes not used in both reactions, just one) allow only one process to occur at a time = reciprocal regulation. To prevent futile cycling
31
Q

Where are regulatory enzymes found? (2)

A
  1. Enzymes that catalyze irreversible reactions (Spontanious)
  2. Metabolic branchpoints
32
Q

Which enzymes are good candidates for glycolytic regulation?

A

Kinases. (phosphoryl group transfer)

33
Q

Which glycolytic enzymes are good candidates for regulation?

A

Those that catalyze favourable reactions!

Unfavourable reactions run bc they’re coupled with favourable reactions

Reactions close to equilibrium run by mass action/substrate availability

34
Q

How much free energy does ATP yield? (ADP –> ATP costs how much?)

A

30.5 kJ/mol per ATP

35
Q

Why is phosphoglycerate kinase NOT a regulatory enzyme?

A

Because it is used to drive glyceraldehyde 3-phosphate dehydrogenase (NAD+ –> NADH) (which is an unfavourable reaction and cannot run without a favourable reaction)

36
Q

How does Glucose 6-phosphate impact Hexokinase in step 1 of glycolysis?

A

Negatively inhibits hexokinase via product inhibition.

37
Q

Which enzyme is considered the “Committing enzyme” that commits the molecule to glycolysis?

A

PFK-1 (Phosphofructokinase-1)

38
Q

Which enzyme in glycolysis is the Schiff base?

A

Hexosphosphate isomerase

39
Q

Coordinated allosteric regulation

A

As one rxn is turned up (glycolysis) the reciprocal rxn is turned down (gluconeogenesis)

40
Q

A positive deltaE means what?

A

Favorable reaction, -deltaG

41
Q

If you are reducing a molecule, does the reducing potential (E) become more pos or less pos?

A

More positive. Reducing is gaining electrons = additional electric / electron flow so voltage/E increases.

42
Q

Generally, anabolism is convergent and catabolism is divergent. (T/F)

A

False, catabolic pathways are typically convergent and anabolic pathways are divergent.

43
Q

Which of the following is the fastest way to regulate an enzyme?

A

Substrate availability

44
Q

What reaction is the following:

H2O –> H+ + OH-

A

Ionization

45
Q

What reaction is the following:

CH2=CH-OH –> CH3-CH=O

A

Isomerization stabilizing product

BIOC 221 - Metabolism (6 decks)

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