Carbohydrate Metabolism Flashcards Preview

MCM Exam 1 > Carbohydrate Metabolism > Flashcards

Flashcards in Carbohydrate Metabolism Deck (93):
1

Deficiency enzyme in lactose intolerance?
Symptoms?

Lactase (Age dependent)
Gas, belly pain, bloating

2

What are the three steps in Glycogenesis?

1. Trapping and activation
Gluco/hexokinase phosphorylate glucose to g-6-p.
Phosphoglucomutase then isomerizes G-6-P to G-1-P. UDP-Glucose pyrophosphorylase then puts a UTP on to make UDP Glucose.
2. Glycogen synthase then elongates the glycogen primer using udp-glucose.
3. Glucosyl (4:6) transferase breaks off parts of chain and adds to other parts.

3

What are the two broad categories of glycogen storage diseases? What does the first kind lead to?

Disorders affecting breakdown. Lead to hepatomegaly and hypoglycemia.
Disorders affecting synthesis.

4

What is hemolytic anemia? Name a few of the causes? What are the two biochemical markers

Destruction of RBC's
Defects in glycolysis enzymes, nutritional deficiencies
Unconjugated bilirubin (heme protein), elevated lactate dehydrogenase (because rbc's use glycolysis and use this to regenerate NAD+)

5

Free energy equations

ΔG=ΔG* + RTlnQ
ΔG*= -RTlnKeq

6

What are 4 precursors of gluconeogenesis?

Glycerol, Propionate, Alanine, Amino acids (except leucine and lysine)

7

What is GSD 6/ Hers disease?

Deficiency in liver glycogen phosphorylase. Prevents breakdown in liver, accumulates causing hepatomegaly

8

Is glycolysis activated or deactivated during Exercise? What causes this on what enzyme?

Stimulated during exercise to have more energy. Low ATP to AMP ratio on PFK.

9

What are the two Galactosemia diseases?

Deficiency in Glucose 1p Uridyltransferase (GALT) - (Accumulation of galactitol)
Deficiency in Galactokinase (accumulation of galactose and galactitol)

10

Glycolysis step.
Glyceraldehyde 3 Phosphate to _____
Enzyme that does this?
What gets used?

1-3 Bisphosphoglycerate
Glyceraldehyde 3-p Dehydrogenase
NAD+ to NADH, and an inorganic phosphate

11

Purpose of Gluconeogenesis?
Glucose needs per day-
Whole body:
Brain
Glucose in body fluids?
Glucose readily in glycogen?
Are direct glucose reserves enough for a day?

Create glucose from other molecules
160g
120g
20g
190g
Yes

12

What is the cause of Tauri disease? What are some symptoms

Deficient in PFK-1
Hemolitic anemia, high bilirubin and jaundice, exercise cramps and weakness

13

What is the structure of glycogen? How are chain molecules linked together? How are branch points linked together? What are at the non-reducing ends? What are at the reducing ends? Which end is Glycogen degraded and extended from?

Long chain homopolymer of glucose.
alpha 1-4 glycosidic———-alpha 1-6 glycosidic
Non-reducing ends: terminal glucose with free hydroxyl group at carbon 4————-Reducing end: glucose monomer connected to glycogenin protein. ———-Degraded-extended from non-reducing end.

14

Red blood cells lack ____ so they cannot do aerobic respiration

Mitochondria

15

What is lysosomal glycogenolysis

A small amount of glycogenolysis is done in lysosome by alpha 1-6 glucosidase. Not having this is called Pompe disease

16

What are the things Glucose 6 Phosphate can be eventually converted to?

Glucose, Pyruvate, Glycogen, Ribose/NADPH in the Pentosephosphate Pathway

17

What is Fanconi Bickel Syndrome? What are the biochemical effects?

Mutation in GLUT 2 transporter. Unable to take up glucose, galactose, and fructose.

18

What is the rate limiting enzyme in Glycolysis? What is it activated by? What is it inhibited by? It is active in its ____ form. What hormones influence it and how?

PFK-1
AMP, F2-6BP (the latter is made from PFK-2/FBPase-d
ATP, Citrate from TCA Cycle
Active when dephosphorylated, inactive when phosphorylated

Insulin stimulates, causes PFK-2/FBPase-2 to produce F2,6BP, so it activates PFK-1
Glucagon inhibits, causes PFK-2/FBPase-2 to phosphorylate PFK-1, which reduces the activity.

19

What hormones orchestrate fed state vs fasting state? Which of these pertains to gluconeogenesis and glycogenolysis?

Insulin/Glucagon
Fasting increased gluconeogenesis and glycogenolysis

20

Glycolysis Step.
1-3 Bisphosphoglycerate to ____
Enzyme:
Regulatory Step?

3 Phosphoglycerate
Phosphoglycerate Kinase
ATP is created but NOT a irreversible step (one each 3 carbon chain so x2

21

What does NADPH regenerate? What does this product detoxify?

Glutathione
H2O2

22

Coupled reactions must share a common _____

Intermediate

23

Positive regulators of Gluconeogenesis?
Negative regulators?

Positive: Glucagon, citrate, cortisol, thyroxine, acetyl coA
Negative: ADP, AMP, Fru 2-6 bis

24

De novo synthesis is ___ and occurs at ___?

Gluconeogenesis
Liver

25

What is one of the only fuels to cross the blood brain barrier?
During starvation, what two processes help feed brain?

Glucose
Liver gluconeogenesis to give brain glucose, using ketone bodies

26

Where and how is glycogen stored? What else is contained in glycogen granules?

Stored in granules in the liver and muscle. These also contain enzymes needed for glycogen metabolism

27

What is the structure of glycogen? How are chain molecules linked together? How are branch points linked together? What are at the non-reducing ends? What are at the reducing ends? Which end is Glycogen degraded and extended from?

Long chain homopolymer of glucose.
alpha 1-4 glycosidic
alpha 1-6 glycosidic
Non-reducing ends: terminal glucose with free hydroxyl group at carbon 4
Reducing end: glucose monomer connected to glycogenin protein.
Degraded-extended from non-reducing end.

28

Glycolysis step
Last step in glycolysis creates _____
Enzyme:
Regulatory?

Pyruvate
Pyruvate Kinase
Yes, 1 ATP created per 3 carbon molecule

29

What is F1,6BP deficiency?

Disease associated with gluconeogenesis
Hypoglycemia, lactic acidosos, etc.

30

What is located in cell membrane to bring sugars in?

GLUTS, sugars cant get in on own

31

For enzyme, Ea is minimum amount of energy needed to convert ____ to _____.

Substrate to intermediate

32

Positive regulators of Glycolysis? (4)
Negative regulators ? (5)

Positive: Glucose, insulin, AMP, Fru 1-6 and 2-6 bisphosphate
Negative: Glucagon, ATP, Gluc and Fruc 6P, Citrate, Alanine

33

Glycolysis step
Immediately after creating two 3x carbon molecules, what occurs?
What are the names of the newly created molecules?

Glyceraldehyde 3 phosphate and DHAP
Isomerization of DHAP to make another Glyceraldehyde 3 phosphate so you have 2x of them

34

What are the deficiencies in galactose metabolism?

Deficiency in GALT: leads to accumulation ofgalactitol.
Deficiency in Galactokinase: Leads to accumulation of galactose and galactitol.

35

How are glycogen synthase and phosphorylase regulated? What are their active and inactive forms?

Phosphorylation.
Glycogen synthase active without P, inactive with P.
Glycogen phosphorylase is opposite. (The phosphorylase likes being phosphorylated)

36

What are the three irreversible Checkpoints in glycolysis and what are their enzymes? What 5 molecules influence these enzymes?

Glucose to Glucose 6 Phosphate. Hexokinase/Glucokinase. ATP used

Fructose 6 phosphate to Fructose 1-6 bisphosphate
Phosphofructokinase 1. ATP used

Creating Pyruvate
Pyruvate Kinase. 1 ATP generated

ATP, AMP, Glucose, Insulin, glucagon

37

What two main things does the Pentose Phosphate pathway produce? Does it produce energy?

Sugar in DNA/RNA, NADPH.
No energy

38

Equation for the Lineweaver Burk?

1/V = Km/(Vmax * S) + 1/Vmax

39

Where does PPP occur? What is the starting/ending of the pathway? What gets oxidized and what gets reduced?

Cytosol
Oxidation of G6P to Ribulose 5-P
Reduction of NADP+ to NADPH

40

Dietary fiber comes from

Plants

41

Overworked muscles that lack O2 must rely on ____

Glycolysis

42

Glycolysis step
Glucose 6 Phosphate to____
What type of reaction is this?
Regulatory?

Fructose 6 Phosphate
Isomerization
Not regulatory

43

Hemolytic Anemia:
What is this caused by
What happens to RBC ion gradients?

Destruction of RBC's
Caused by unable to do glycolysis because they dont have mitochondria to do aerobic so are fucked, dont even have ion gradients cause of no atp

44

What proteins are involved in Insulin regulation? What is the net result?

GLUT 4———-Protein Kinase B (PKB)———-Protein Phosphatase (PP1)
Glycogen synthase kinase 3 (GSK3)
Glycogen synthesis via activation of glycogen synthase and inactivation of glycogen phosphorylase

45

How is GLUT4 Sequestered? What brings it out?

Vesicles in cells
Insulin causes vesicle membrane fusion

46

For Non competitive inhibitors, what happens to KM and Vmax

Vmax down, KM same

47

What is the function of liver glycogen? Muscle glycogen?

Liver glycogen: regulate blood glucose levels
muscle glycogen: provide glucose reservoir for physical activity

48

Why is glycogen regulated? (2) Are they regulated together or seperate? What are the rate limiting enzymes of glycogen synthesis and degradation?

Maintain blood sugar and provide energy for muscle.
Seperate.
Glycogen synthase, glycogen phosphorylase.

49

What is GSD4/Andersen disease?

Deficiency in glycosyl (4:6) transferase (branching enzyme)

50

Where does gluconeogenesis occur?
What molecule is converted to glucose?
What are the main precursors to this?

Liver, kidney, small intestine
Pyruvate
Lactate, amino acids, glycerol

51

Does glucagon work on muscle?
Is cellular calcium high or low duringe exercise?

No
high

52

3 types of membrane proteins? Subgroup of the first type?

1. Integral membrane proteins (firmly embedded): Subtype polytopic transmembrane proteins (multiple passes)
2. Peripheral proteins
3. Lipid anchored

53

Gluconeogenesis enzymes to bypass rate limiting steps of glycolysis
Hexokinase/Glucokinase?
PFK-1?
Pyruvate Kinase?

Glucose 6 Phosphatase
Fructose 1-6 bisphosphatase
PEP carboxykinase and Pyruvate carboxylase

54

Where does the PPP occur? Oxidation of G-6-P to ____. Reduction of NADP+ to ___. Irreversible and Reversible steps

Cytosol.
Ribulose 5-p
NADPH

55

Glycolysis step.
Glucose -->_____
Purpose:
Enzymes:
Regulatory step?

Glucose 6 phosphate
Trap glucose in cell
Hexokinase (all) Glucokinase (liver, pancreatic B cells)
Yes regulatory, uses ATP (Sub level phos)

56

What is sucrose and what cleaves it? What is lactose and what cleaves it? What uptakes fructose? What uptakes Galactose and glucose?

Sucrose: fructose + glucose, cleaved by sucrase.
Lactose: Galactose + glucose, cleaved by lactase.
Fructose uptake: GLUT5
GAL/GLC uptake: SGLT1

57

Net reaction of glycolysis

1 Glucose goes to 2 Pyruvate, 2 ATP, 2 NADH

58

GLUT 1-4 Location, Affinity, Which is regulated?

1 Everywhere, high
2 Liver and Pancreas, low,
3 Neurons, high
4 Skeletal muscle, adipose, heart, Regulated by insulin

59

For uncompetitive inhibitors, what happens to KM and Vmax

Vmax down, Km down

60

What is GSD3/Cori disease?

Deficiency in a 1-6 glucosidase (debranching enzyme)

61

For competitive inhibitors, what happens to KM and VMAX?

Vmax same, Km up

62

What is Fructose 1-6 Bisphosphatase? Why is it more important than the others?

Gluconeogenesis enzyme.
It is the rate limiting step.

63

What is Diabeties characterized by?
Type 1 is loss of _____
Type 2 is because of ____

Hyperglycemia
Pancreatic B cells, immune system disruption
Insulin resistance, loss of B cell function

64

What are the three phases of glyocolysis?

Investment, splitting, recoup/payoff

65

2 Regulators of blood glucose?
Ranges of blood glucose
Normal/Fasting?
Fed?
Diabetus fasting?
Diabetes fed?
Amount to make convulsions, coma, brain damage?

Insulin, Glucagon
70-100 mg/dl
100-140
>126
>199
<40

66

What condition do most innefective glycolysis defects cause?

Hemolytic anemia

67

Pyruvate Carboxylase
What is it?
Where is it found vs the others?
What is its function?
What is its prosthetic group?

The first Gluconeogenesis enzyme
In mitochondria, others are not
Carboxylates Pyruvate to oxaloacytate
Biotin

68

3 phases of glycolysis?

Investment: 2 ATP put in
Splitting: 6 Carbon to two 3 Carbon molecules
Recoup: 4 ATP get out

69

What is GSD 0?

Deficiency in glycogen synthase

70

3 Types of Membrane Lipids? 2 Subtypes of Phospholipids?

1. Phospholipids: Glycerophospholipids, Sphingolipids
2. Glycolipids: Sphingosine backbone
3. Cholesterol

71

What is the purpose of the Polyol Pathway? What are the two steps and enzymes? What happens if the second enzyme is not present?

Convert Glucose into Fructose.
Glucose reduced to Sorbitol by Aldol Reductase.
Sorbitol oxidized to fructose by sorbitol dehydrogenase.
If no Sorbitol dehydrogenase (Kidneys, lens, retina, schwan cells), these cells can accumulate sorbital which brings in water and swells. This causes cataracts.

72

How many atp are generated in glycolysis? How about ox phosphorylation?

2, 34-36

73

What happens to Glu-1-p in liver? In Muscle?

Glu-1-P converted to Glu-6-P, then to Glu by glucose-6-phosphatase.
Muscle cels dont have glucose-6-phosphatase, cant hydrolyze G-6-P so just use it in glycolysis.

74

What is Von Gierke disease?

Deficiency in glucose 6-phosphatase, the final enzyme in gluconeogenesis and glycogenolysis. Hypoglycemia, lactic acidosis, etc.

75

Glycolysis Step
Fructose 6 Phosphate to _____
Enzyme:
Regulatory step? Why is this more important than others?

Fructose 1-6 bisphosphate
Phosphofructokinase-1
Yes, uses 2nd ATP. In fact, it is the rate limiting step of glycolysis.

76

Amino acids can generate ATP in what cycle?
Amino acids are key components in ___ tissue?

TCA Cycle
connective

77

Branching Order for Glycogen, Starch and Cellulose?

CSG lower to higher

78

For the following Gluconeogenesis precursors, state the source and point of entry of precursor. Glycerol, propionate, alanine, Amino acids(Except leucine and lycine)

Glycerol: Lipid degradation, DHAP
Propionate: Degradation of odd numbered fatty acids, TCA cycle intermediate (succinyl coA, which is converted to malate)
Alanine: Pyruvate
Amino acids: TCA Cycle intermediates, which are converted to malate

79

Does glucagon act on muscle?

No

80

What activates Pyruvate Kinase? What inactivates it? Does PK phosphorylation activate it (1.) or deactivate it (2.) and what hormone causes this and vice versa?

F1-6BP, Insulin
ATP, Alanine, Glucagon
Insulin, Dephosphorylates PK, activating it
Glucagon, Phosphorylates PK, inhibiting it

81

What is Glucose 6-Phosphatase?
What does it do?
Where is it found?

Gluconeogenesis enzyme
Desphosphorylation to finally form glucose
Liver, kidneys, small intestine, pancreas

82

At what temperature is the membrane fluidity best?

Slghtly above Tm, the melting temperature.

83

What are the two steps of glycogenolysis

1. Chain shortening: Glycogen phosphorylase uses vitamin B6 as cofactor and cleaves glucose off as G-1-P. Stops when it gets within 4 residues of a alpha 1-6 branch point.
2. Debranching enzyme transfers 3 of the 4 remaining glucose to non-reducing end of main chain. Then cleaves the alpha 1-6 bond to release a free glucose.

84

What is the purpose of the Cori Cycle?
Where does it occur?

Links lactate to gluconeogenesis, (also prevents lactate accumulation, creates more glucose)
In the liver

85

Components and bond
Sucrose
Lactose
Maltose

Glucose Fructose Alpha 1-2, B-2
Glucose Galactose Beta 1-4
Glucose Glucose Alpha 1-4

86

Gallblader stores ____? Non ideal composition of this substance is ____, which can lead to what conditions?

Bile to break down lipids
Too much cholesterol, not enough bile salts
Malabsorption, fat soluble vitamin deficiencies

87

What is Phosphoenlolpyruvate Carboxykinase (PEPCK)?

Second Gluconeogenesis enzyme

88

What is GSDV/Mcardle disease?

Deficiency in muscle glycogen phosphorylase, rate limiting step of glycogen breakdown

89

Glycolysis Step
Fructose 1,6 Bisphosphate to _____
What kind of reaction is this?

Two 3 Carbon Molecules
Cleavage

90

Hexokinase/Glucokinase
Location:
Affinity:
Vmax
Substrate
Strength of G6P inhibition?

All cells / Liver and Pancreatic B cells
High affinity / Low affinity
Low / High
Glucose and others / Just Glucose
Inhibited by G6P / Weakly inhibited by G6P

91

What happens to the Glu-1-p from Glycogenolysis in the liver?
What happens to G-6-P in muscle?

In liver, Glu-1-p converted to G-6-P, then to Glu by Glucose-6-phosphatase.
In muscle, they lack G-6-P Phosphatase and so cant hydrolyze GlU-6-P. Use it to generate energy via glycolysis and TCA cycle.

92

What are the four fates/processes for Pyruvate?

Reduced to lactate (creates NAD+) -Humans
Converted to ethanol (yeast)
Oxidized in TCA cycle to acetyl-COA then CO2
Converted to Alanine (gluconeogenesis and protein synthesis

93

Why is fructose metabolism faster than glucose?

It inserts into glycolysis after pfk-1, skipping a check. This gets converted into fat more efficiently.