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Biochem 6200 > Lecture 6 Carbs > Flashcards

Lecture 6 Carbs Flashcards

1
Q

D-glucose to L-lactate

A

2 ADP + phosphate –> 2 ATP. 10-11 steps. 6 carbons to 3 carbons.

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2
Q

RBC blood amount

A

40% of blood, 3% total body mass, about 20g of glucose per day (10% body metabolism). 90% of glucose metabolized via glycolysis (lots of lactate).

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3
Q

Key points of glycolysis to know

A

Know:
step 1: Glucose to Glucose-6-phosphate. Gives glucose - charge, prevents glucose from leaving cell easily. Know step product/reactant names.

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4
Q

Glycogen

A

Stored Gluc-6-phos

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5
Q

Glyceraldehyde-3-phosphate

A

Know this molecule.

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6
Q

Pentose Phospha

A

precursor for forming DNA/RNA

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7
Q

NADPH

A

Degrade/process drugs, antioxidant.

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8
Q

Glucose

A 
Break down for energy
Build up reserve energy (glycogen)
Build lipids
Build carbs for DNA/RNA
Produce NADPH (oxidative stress defense).
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9
Q

Phosphofructo Kinase

A

PFK-1 - rate limiting enzyme for breaking glucose. fructose-6-P + ATP fructose-1,6-bisP + ADP. Highly regulated.

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10
Q

GAPDH

A

Glyceraldehyde 3- phosphate dehydrogenase. Forms NADH+

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11
Q

Phosphoglycerate Kinase

A

Takes phosphate group and adds it to ADP (first energy formation in glycolysis).

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12
Q

Glycolysis location

A

Cytosol of cells - Glucose enters the Glycolysis pathway by conversion to glucose-6-phosphate.
Initially there is energy input corresponding to cleavage of two P bonds of ATP.

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13
Q

Hexokinase

A

ATP binds to the enzyme as a complex with Mg++. Forms G-6-P

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14
Q

Mg++

A

Mg++ interacts with negatively charged phosphate oxygen atoms, providing charge compensation & promoting a favorable conformation of ATP at the active site of the Hexokinase enzyme.

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15
Q

Aldolase

A

Forms Glyceraldehyde 3 phosphate from fructose 1-6 bisphosphate. Aldol cleavage, reverse of aldol condensation.

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16
Q

Phosphoglycerate Kinase

A

1,3-bisphosphoglycerate + ADP
3-phosphoglycerate + ATP
First ATP return.

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17
Q

Pyruvate Kinase

A

PEP (phosphoenolpyruvate) +ADP –> pyruvate + ATP. Spontaneous transfer.

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18
Q

Balance sheet for glycolysis

A

2 ATPs used, 4 ATP produced. 2 overall gained.

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19
Q

Aerobic

A

Pyruvate fed into Krebs cycle (oxidized to CO2). NADH produced and used in electron transfer chain.

20
Q

Fermentation

A

Anaerobic orgs. Must reoxidize NADH, as NAD+ is required for GAPDH reaction. Reoxidized as pyruvate is converted to a more reduced compound. Skeletal muscles ferment, resulting lactate used in brain or heart for energy.

21
Q

Astrocytes

A

surround and protect neurons in the brain, ferment glucose to lactate and release it.

22
Q

Hexokinase inhibition

A

Inhibited by Glucose-6-phosphate

23
Q

PFK-1 inhibition

A

Inhibited by ATP, activated by AMP

24
Q

Pyruvate Kinase inhibition

A

Activated by Fructose 1-6 BP

25
Q

Build it up and break it to…

A

2x G3P. Precursor for yield stage. Know ATP using/generating enzymes.

26
Q

Pentose Phosphate Path

A

6 to 5 carbon - base for DNA/RNA. In the process you generate NADPH Later on you can reform molecule for G3P for glycolysis.
Glucose 6 phosphate dehydrogenase oxidizes gluc-6-p to create NADPH. Important antioxidant molecule in body.

27
Q

NADPH

A

Important antioxidant. Forms fro G-6-P from G6PDH.

28
Q

GSH/GSSG Slide/relationship

A

Many oxidative species. Glutathione peroxidase takes the brunt of this, simultaneously reducing GSSG from GSH, where NADPH oxidizes this. **LOOK AT THIS SLIDE

29
Q

Glycogen

A

1300 calories stored, only 40 cal glucose on hand (used constantly). Glucose molecules linked together via alpha 1-4 glycosidic bonds. Can bifurcate to form branches. At branches you have alpha 1-6 links. UDP-glucose is the intermediate building block for glycogen.

30
Q

UDP-glucose

A

Building block intermediate for glycogen formation.

31
Q

UTP+glucose-1-phosphate

A

UDP-glucose

32
Q

Glycogenin

A

Link 1 UDP glucose to another glucose (lose UDP during this process. Initiates chain formation.

33
Q

Glycogen Synthase

A

Catalyzes elongation of glycogen chains initiated by glycogenin

34
Q

Where would you expect to find glycogenin in cell?

A

Most of the Glycogenin is found associated with glycogen particles (branched glycogen chains) in the cytoplasm.

35
Q

Reciprocal control

A

Both synthesis & breakdown of glycogen are spontaneous.
If both pathways were active simultaneously in a cell, there would be a “futile cycle” with cleavage of one ~P bond per cycle (in forming UDP-glucose).
To prevent such a futile cycle, Glycogen Synthase and Glycogen Phosphorylase are reciprocally regulated, by allosteric effectors and by phosphorylation.

36
Q

Glycogen phosphorylase

A

In muscle, subject to allosteric reg by AMP, ATP, G6P. Seperate isozyme of phosphorylase expressed in liver is less sensitive to these allosteric controls:

 AMP (present significantly when ATP is depleted)
activates Phosphorylase, promoting the relaxed
conformation.
 ATP & glucose-6-phosphate, which both have binding
sites that overlap that of AMP, inhibit Phosphorylase, promoting the tense conformation.
 Thus glycogen breakdown is inhibited when ATP and
glucose-6-phosphate are plentiful.

Break down by 1 glucose at a time.

37
Q

Glycogen Phosphorylase dimer

A

Homodimer - we have drugs that inhibit this enzyme. Why \would an inhibitor of glycogen phosphorylase be a suitable treatment for diabetes? Making breakdown of glucose harder, helping alleviate the large amount of glucose.

38
Q

Debranching enzyme

A

Takes branch away so you can break down more of glycogen molecule.

39
Q

From Glycogen

A

G1P to G6P - can be used in glycolysis or stripped of phosphate and put into blood. Similar in liver.

40
Q

Epinephrine

A

Increases glucose to blood.

41
Q

Glucagon pathway

A

Terminated quickly. G-protein can be destroyed or cAMP can be destroyed. Protein phosphatase activity can also be halted.

42
Q

Muscle vs. Liver glycogen

A

Liver glucose gets shipped out to other places. Muscle stays and is used immediately.

43
Q

Insulin

A

Too much glucose in blood. Absorb and build glucose to glycogen. Anabolic hormone. Anti-glucagon effects.

44
Q

Gluconeogenesis

A

Take breakdown material and form glucose. Not reversible at fructose 1-6- bisphosphatase step.

45
Q

Glycolysis and Gluconeogenesi9s

A

Reciprocally regulated. Local control - includes reciprocal allosteric regulation by adenine nucleotides.

46
Q

Local control

A

Phosphofructokinase (Glycolysis) is inhibited by ATP
and stimulated by AMP.
 Fructose-1,6-bisphosphatase (Gluconeogenesis) is
inhibited by AMP.

Biochem 6200 (18 decks)

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