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Biochemistry > Biochem Exam 2: Glycolysis And Gluconeogenesis > Flashcards

Biochem Exam 2: Glycolysis And Gluconeogenesis Flashcards

1
Q

What two organs use glucose only

A

RBC and brain

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2
Q

Sources of glucose in diet?

A

Starch
Glycogen
Disaccharides (sucrose and lactose)

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3
Q

GLUT1

A

Ubiquitous but high in RBC and brain

High affinity for glucose

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4
Q

GLUT 2

A

Transporter in liver

Low affinity

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5
Q

GLUT 3 neurons

A

High affinity

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6
Q

GLUT 4 skeletal muscles, heart, adipose tissue

A

Insulin dependent

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7
Q

Low KM means what for glucose?

A

High affinity

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8
Q

High KM means what for glucose?

A

Low affinity

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9
Q

In stage one, the first enzyme to break glucose down to glucose 6-phosphate is what?

A

Hexokinase

In liver it is glucokinase

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10
Q

Glucose 6-phosphate is broken down to fructose 6-phosphate by what enzyme?

A

Phosphoglucose isomerase

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11
Q

Fructose 6-phosphate is broken down to Fructose 1,6 bisphosphate by what enzyme?

A

Phosphofructokinase

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12
Q

What is the strategy of phase one in glycolysis?

A

To trap glucose and for a compound that can be readily cleaved into 2 phosphorylated 3 carbon units

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13
Q

What is the committed step for stage one of glycolysis?

A

Glucose 6-phosphate to fructose 6-phosphate (phosphoglucose isomerase)

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14
Q

Enzyme that breaks down F1,6 BP to glyceraldehyde 3 phosphate is what?

A

Aldolase

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15
Q

What enzyme isomerizes DHAP?

A

Triode phosphate isomerase

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16
Q

G3P is oxidized to 1,3 BPG by what enzyme and what carrier molecule?

A

Enzyme glyceraldehyde 3-phosphate dehydrogenase

Carrier molecule NAD+ reduced to NADH

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17
Q

1,3 BPG is converted to 3-PG by what enzyme

And what does it make?

A

Phospholycerate kinase

Makes ATP

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18
Q

3-phosphoglycerate is converted to 2-phosphoglycerate via what enzyme?

A

Phosphoglycerate Mutase

Changes the phosphate to the 2 orientation instead of the 3

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19
Q

2-PG is converted to PEP (phosphoenolpyruvate) by what enzyme?

A

Enolase (produces water- dehydration)

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20
Q

PEP is converted to pyruvate by what enzyme?

A

Pyruvate kinase transfer

This step is irreversible

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21
Q

Pyruvate can be converted into 3 things considering the oxygen level what are these three things? And how does it occur?

A

Further oxidation with oxygen present after getting ride of CO2 and becoming Acetyl CoA

It can become lactate by taking back the hydrogen on NADH

It can create ethanol by getting rid of CO2 AND taking back the hydrogen on NADH

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22
Q

By pyruvate becoming lactate, what is regenerated?

A

NAD+

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23
Q

Glucose + fructose creates what

A

Sucrose

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24
Q

Glucose + galactose create what?

A

Lactose

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25
The important rate limiting step in glycolysis is what enzyme?
Phophofructose
26
Why is fructose bad for us?
It skips the rate limiting step when found in the liver (enters in the DHAP or GAP entry of stage 1) Fructose is quickly turned to fat in times of high energy Can give us a fatty liver, type diabetes, obesity, and insulin insensitivity
27
Where does galactose enter?
G-6p
28
Where does fructose from adipose tissue enter?
F-6P
29
Major regulators of glycolysis include these 3 enzymes
Hexokinase Phosphofructokinase Pyruvate kinase
30
What negative feedbacks on hexokinase?
G-6P
31
What is g-6p converted to when the muscle is at rest?
Glycogen
32
What negatively feedbacks on PFK?
Pyruvate kinase
33
When the muscle is active and glycolysis is stimulated, what are two positive feedback loops?
1. Decreased ATP causes PFK to reactive teens | 2. Increase in F 1,6-B causes pyruvate kinase to activate
34
In the liver what two enzymes are regulated and by what?
Phosphofructokinase is activated by F 2,6 BP Inhibited by citrate ``` And glucokinase (no hexokinase) Not regulated! Glucose is trapped ``` Pyruvate kinase is regulated by allosteric effectors and covalent modification (phosphorylated -less active and dephosphoralated -more active)
35
Low glucokinase means what for the liver and glucose?
Glucokinase is inhibited (glucose doesnt want to be trapped)
36
Gluconegogenesis definition
Synthesis of glucose from non-carbohydrate precursors
37
What are three major precursors in creating glucose?
Lactate, amino acids (alanine), and glycerol
38
Is gluconeogenesis the reversal of glycolysis?
No
39
Where does gluconeogenesis occur in the body?
Liver and kidney
40
What does gluconeogenesis do with pyruvate?
Coverts it to glucose
41
What four enzymes help to reverse the irreversible step in glycolysis?
1. Pyruvate carboxylase 2. Phosphoenolpyruvate (PEP) carboxykinase 3. Fructose 1,6-BPase 4. Glucose 6-phosphatase
42
What enzyme that helps to bypass the irreversible steps of glycolysis is found in the mitochondria?
PC (pyruvate carboxylase)
43
How is oxaloacetate transferred to the cytoplasm?
Malate shuttle
44
Where is glucose 6-phosphatase located
In the lumen of the endoplasmic reticulum | And it removes the phosphate so glucose can leave the liver
45
How are gluconeogenesis and glycolysis regulated together?
As reciprocals
46
Positive regulators for gluconeogenesis are....
``` Glucagon Citrate Cortisol Thyroxine Acetyl CoA ```
47
Can lactate become pyruvate?
Yes, in the liver
48
What is the cori cycle?
Where we take lactate to pyruvate to glucose and glucose to pyruvate and to lactate
49
Characteristics of glycogen
12 layers of glucose Branches Linked together via alpha-1,4 glycosidic bonds A branch forms ever 12 residues via alpha-1,6 glycosidic bonds Non-reducing end contain a terminal glucose with a free hydroxal at C4 Reducing wend has glucose Capp protein called glycogenin
50
Where is glycogen stored?
Liver, muscles, and other tissues
51
How is glycogen present in cells?
As granules
52
How is glycogen metabolism regulated
Allosteric control Covalent modification through reversible phosphorylation of key enzymes Hormonal control
53
How is glycogen storage build? Glucogenesis?
1. Take glucose to glucose 6-P. Then enzyme mutase changes it to G1-P. G1-P is phosphorylated to UDP-G. 2. UDP-G is added to a primer using glycogen synthase. ( Rate limiting step) and forms alpha 1,4 glycosidic bond between molecules of glucose. 3. When glycogen reaches the 11 residue, a fragment of changing is broken off at an alpha 1,4 link and reattached via a alpha 1,6 linkage by glucosyl tranferase
54
The more branches the faster glycogen can be degraded, true or false?
True
55
Glycogen synthase is active in what form?
Non-phosphorylated “a” form
56
Glycogen synthase is inactive in what form?
Phosphorylated “b” form
57
How is glycogen synthase phosphorylated?
By glycogen synthase kinase (GSK) Protein kinase A (PKA) Hormonal control
58
How is glycogen synthase de phosphorylated?
Protein phosphatase I (PPI)
59
How is glycogen synthase allostericly regulated?
Gluc-6-phosphate
60
Glycogenolysis, how many steps?
2
61
What is step one in glycogenolysis?
Chain shortening (release of Glu-1-P)
62
What is the rate limiting step of glycogenolysis?
Glycogen phosphorylated (GP)
63
What is the cofactors of glycogen phosphorylated? (GP)
B6 (pyridoxal phosphate)
64
How far will glycogenolysis go on for?
Within 4 residues of a alpha 1,6 linkage
65
What is step 2 of glycogenolysis?
Branch transfer and release of glucose
66
What enzyme is used to debranch glycogen?
Debranching enzyme (transferase 4:4)
67
GP exist in 2 forms an active and inactive. What is its active form?
Relaxed state in liver “a” | Phospho form
68
GP has an inactive state, what is it?
“B” form (tense state) in muslce Dephospho
69
Phosphorylation of single serine residue converts b to a how is this conversion initiated and what enzyme carries this action out?
``` Hormones Phosphorylase kinase (PK) ```
70
Does glucagon act on mucscles?
NO
71
What acts on muscles to release glycogenolysis?
Epinephrine
72
What cells of pancreas release glucagon?
Alpha cells
73
What cells of pancreas release insulin?
Beta
74
Free glucose inhibits glycogen phophorylaase in liver but not muscles true or false
True
75
In liver cells what is the glucose sensor?
Glycogen phosphorylase
76
Glycogen storage disease | Disorder to affect synthesis:
Autosomal recessive | Patients need to be dependent on glucose rather than glycogen
77
Glycogen storage disease disorders that effect breakdown:
Lead to hepatomegaly | Lead to hypoglycemia
78
I von Gierke
Defective: glucose 6-phosphatase or transport system Causes disorder in breakdown Liver and kidneys
79
II pompe
Defective alpha 1,4 glucosidase (lysosomal) All organs Increase in amount of glycogen Death by cardiorespiratory failure by 2
80
III corti
Alpha 1,6 glucosidase (debranching) Muscle and liver Increased amount of glycogen Like type 1
81
IV Andersen
Branching enzyme Liver and spleen Normal amount glycogen (very long) Progressive cirrhosis of liver Liver failure by age 2
82
V McArdle
Phosphorylase Muscle Moderately increased amount of glycogen Limited ability to perform strenuous exercise
83
VI hers
Phosphorylase Liver Increased amount of glycogen Like type I

Biochemistry (9 decks)

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