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Biochem > Lecture1-CarbohydrateMetabolismandGlycolysis > Flashcards

Lecture1-CarbohydrateMetabolismandGlycolysis Flashcards

1
Q

What is a hexose and pentose carbohydrate? Give examples of both

A

Hexose (6 carbons),
-e.g. glucose, fructose, mannose, galactose
Pentose (5 carbons),
-e.g. ribose (in DNA, RNA, NADH, etc.)

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2
Q

What are the alpha and beta stereoisomer of carbohydrates

A

Alpha: OH below the plane

beta: OH above the plane

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3
Q

What are the two types of sugars? what are they an example of?

A

D-sugars and L-sugars

Enantiomers

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4
Q

What is the most common sugar in mammals

A

D-sugar

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5
Q

What sugar is in plants and microorganism ?

A

L sugar

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6
Q

What is disaccharides used for?

A

For storage

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7
Q

What are examples of disaccharides?

A

Lactose: galactose-glucose (milk sugar)
Sucrose: glucose-fructose (table sugar, saccharose)

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8
Q

What is lactose made of?

A

Lactose: galactose-glucose (milk sugar)

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9
Q

What is sucrose made of ?

A

Sucrose: glucose-fructose (table sugar, saccharose)

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10
Q

What are polysaccharides for ?

A

storage and structure

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11
Q

What are examples of polysaccharides

A

Glycogen (animals), starch (plants), dextran (yeast, bacteria), Cellulose (plants), Chitin (insects, crustacean)

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12
Q

What is polysaccharides have (glucose)n alpha linked?

A

glycogen
starch
dextran

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13
Q

What polysaccharide has (glucose)n Beta linked?

A

Cellulose

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14
Q

What polysaccharide has (N-acetyl glucosamine) Beta linked

A

Chitin

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15
Q

What is the function of glycolysis

A

The function of glycolysis is to convert glucose to three-carbon compounds with the formation of ATP

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16
Q

Where does glycolysis occur?

A

Glycolysis occurs in all the cells of the body and the enzymes are located exclusively in the cytosol.

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17
Q

What is the RLE of glycolysis?

A

Phophofructokinase

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18
Q

What is the net energy

A

There is an initial requirement for ATP but glycolysis results in a net production of 2 ATP.

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19
Q

How many oxidative steps are in glycolysis

A

There is one oxidative step in which NAD is oxidized to NADH.

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20
Q

Where do we use ATP in glycolysis

A

Glucose to Glucose-6-phosphate with hexokinase

Fructose-6-phosphate to Fructose 1,6 bisphosphate with phosphofructokinase

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21
Q

Where do we oxidize in glycolysis

A

glyceraldehyde to fructose 1,3 bisphosphate glycerate with glyceraldehyde phosphate dehydrogenase

NAD+ to NADH

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22
Q

where do we make ATP in glycolysis ?

A

1,3 bisphosphate glycerate to 3 phophoglycerate with phosphoglycerate kinase

phosphoenol pyruvate to pyruvate with pyruvate kinase

23
Q

what are the energy utilizing steps in glycolysis?

A

glucose to glucose-6-phosphate with hexokinase

Fructose 6 phosphate to Fructose 1,6 biphosphate with phosphofructokinase

24
Q

What are the energy production phases in glycolysis?

A

glyceraldehyde to fructose 1,3 bisphosphate glycerate with glyceraldehyde phosphate dehydrogenase

1,3 bisphosphate glycerate to 3 phophoglycerbte with phosphoglycerate

phosphoenol pyruvate to pyruvate with pyruvate kinase

25
Q

What are substrate level phosphorylation enzymes in glycolysis

A

1,3 bisphosphate glycerate to 3 phophoglycerate with phosphoglycerate kinase

phosphoenol pyruvate to pyruvate with pyruvate kinase

26
Q

How do we get back the NAD+ to keep glycolysis going

A

pyruvate to lactate with lactate dehydrogenase in anaerobic respiration

27
Q

what is the MAJOR point of control in glycolysis? why?

A

Phosphofructokinase since it is the first enzyme unique to glycolysis

28
Q

What are the 3 points of control for glycolysis

A

AT IRREVERSIBLE REACTIONS

Phosphofructokinase

hexokinase

pyruvate kinase

29
Q

What does phosphofructokinase response to

A

Energy state of the cell (high ATP levels inhibit)

H+ concentration (high lactate levels inhibit)

Availability of alternate fuels such as fatty acids, ketone bodies (high citrate levels inhibit)

Insulin/glucagon ratio in blood (high fructose 2,6-bisphosphate levels activate)

30
Q

What is an activator of glycolysis and what does it do?

A

F-2,6-BP is a strong activator of glycolysis
(increases phosphofructokinase’s substrate affinity)

31
Q

How do we regulate pyruvate kinase in glycolysis

A

We phosphorylate pyruvate kinase to make it less active

We dephosphorylate pyruvate kinase to make it more active

32
Q

What activates dephosphorylated pyruvate kinase and what is the outcome?

A

F-1,6-BP, low ATP, High Blood sugar

INCREASE glycolysis

33
Q

What activates phosphorylated pyruvate kinase and what is the outcome?

A

high ATP, alanine, low blood sugar

LESS glycolysis

34
Q

Glucose homeostasis relies critically on what?

A

detection of variations in blood glucose concentrations by pancreatic beta cells and their timely release of an appropriate amount of insulin.

35
Q

Where does insulin secretion occur?

A

Pancreatic Beta cells

36
Q

What is the rate controlling step in glucose stimulated insulin secretion?

A

phosphorylation of glucose by glucokinase

37
Q

What causes type 2 diabetes?

A

type 2 diabetes is caused by a mutation in the glucokinase gene.

38
Q

How is glucose taken up by beta cells?

A

a low affinity, high- capacity glucose transporter called GLUT2.

39
Q

What is the affinity and capacity of GLUT 2

A

a low affinity, high- capacity

40
Q

Each hormone produced by a different subset of cells in the ____ __ _____

A

Islets of Langerhans.

41
Q

What trips on the ATP dependent switch in Beta cells leading to insulin release

A

Elevated blood glucose

42
Q

Explain how insulin is released in beta cells?

A

Increase glucose–> trigger ATP dependent switch–> close KATP channel–> membrane depolarization–> actives VDCC to push Ca2+ in the cell–> insulin release

43
Q

What is wrong with T2D patients beta cell that does not allow release of insulin

A

The KATP channel does not close to cause membrane depolarization

44
Q

How do we help T2D patient’s beta cells

A

antidiabetic drugs: sulfonylurea and repaglinide

Close the ATP gated K channel

45
Q

What are the anti diabetic drugs?

A

sulfonylurea and repaglinide

46
Q

What causes insulin levels to rise in the body prior to food uptake?

A

Mechanisms by which acetylcholine stimulates insulin secretion in the preabsorptive phase in food intake.

47
Q

What causes insulin levels to rise in the body as we uptake food?

A

Mechanisms by which acetylcholine stimulates insulin secretion in the absorptive phase in food intake.

48
Q

What receptor is used for the released of insulin?

A

m3

49
Q

What is the cori cycle

A

The Cori cycle involves the recycling of lactate produced by metabolism of glucose to lactate in the muscle or erythrocytes and the conversion of lactate back to glucose in the liver via gluconeogenesis.

50
Q

What is the alanine cycle

A

The alanine cycle involves the recycling of alanine produced by metabolism of glucose to pyruvate and alanine in the muscle and the conversion of alanine back to glucose in the liver via pyruvate and gluconeogenesis

51
Q

What are the disease of related to glycolysis

A

Pyruvate kinase deficiency and cancer

52
Q

Explain pyruvate kinase deficiency

A

leading to chronic hemolytic anemia

Autosomal dominant or recessive disease, resulting in deformed spiny red blood cells (“echinocytes”).

Second most common cause of enzyme-deficient hemolytic anemia (following glucose-6-phosphate dehydrogenase deficiency that affects PPP).

53
Q

Explain cancer

A

Malignant rapidly growing tumor cells typically have a glycolytic rate up to 200-fold higher than in normal cells of the same tissue. Frequently accompanied by overexpression of plasma-membrane glucose transporters of the GLUT family, allowing for higher glucose uptake rates.

High glycolytic rate of tumor cells is used for PET (positron emission tomography) imaging in oncology: measurement of uptake of 2-18F-2-deoxyglucose (FDG), a radioactive, modified hexokinase substrate

Biochem (17 decks)

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