Glucose metabolism Flashcards
1
Q
What happens in the mouth when food is ingested?
A
Mechanical digestion ( chewing and swallowing) Chemical digestion of carbohydrates and fats
2
Q
What are the enzymes that are functioning in the mouth
A
Salivary Amylases
Lingual Lipases
3
Q
What molecules are not digested in the mouth
A
Proteins
4
Q
What is the benefit of chewing for the food digestion?
A
Breaking in smaller pieces
Bigger surface area for enzyme activity
5
Q
What happens in the stomach with food ingested?
A
Mechanical digestion ( peristalsis mixing and propulsion)
- Chemical digestion of proteins, fats
- Absorption of lipid soluble substances such as alcohol and aspirin
6
Q
What enzymes function in the stomach
A
Gastrin
Gastric lipase
HCl
Pepsin
7
Q
Where the enzymes in the stomach secreted
A
Gastric lipase and Pepsin (Chief cells)
HCl( Periatal cells)
8
Q
Where do lipids digest in the mouth
A
Lingual lipases are secreted in teeth
9
Q
What does pepsin do
A
Starts the digestion of proteins
10
Q
where is the most absorption in the small intestine
A
Duodenum
11
Q
What is done to the food in the small intestine
A
Mechanical digestion includes mixing and propulsion, primarily by segmentation
Chemical digestion of all molecules
Absorption of peptides, AA,glucose,fats,water,minerals, and vitamins
12
Q
What enzymes are secreted to duodenum and from what place
A
From the pancreas Trypsinogen Chymotrypsinogen Carboxypeptidase A and B Active enzymes target specific AA in proteins Pancreatic amylase/lipase
13
Q
What is happening in the large intestine?
A
Propulsion and mixing
No chemical digestion( except bacteria)
Absorption of ions, water, minerals, and organic molecules
14
Q
What is fisculated cow?
A
A cow that has a whole in the stomach, for the research
15
Q
Why glucose is an excellent fuel?
A
- Yields good amount of energy
- can be efficiently stores
- Many tissues can meet energy needs on glucose only
16
Q
Glucose is a versatile precursor for
A
- All AA
- membrane lipids
- nucleotides in DNA and RNA
- Cofactors in metabolism
17
Q
What is glycolysis
A
Glucose is degraded to puryvate
18
Q
What is glucoenogenesis
A
Glucose is formed from non-carbohydrate source
19
Q
What is glucogenesis
A
Glycogen is polymerized from glucose units
20
Q
What is glycogenolysis
A
Glycogen is degraded to glucose units
21
Q
What is the first step of glycolysis
A
Glucose->glucose 6-phosphate
Phosphate group is added OH, instead of H on carbon 6
22
Q
What enzyme does the first step of glycolysis and what does it use
A
Hexokinase
With the use of ATP, the hydrolysis of ATP is helped by Mg
23
Q
Why conversion of glucose to glucose 6-phosphate is important
A
It traps glucose inside the cell, thus lowering intracellular glucose to allow further uptake
24
Q
What kind of reaction is the reaction of hexokinase reversible/irreversible?
A
Irreversible
25
What is the second step in glycolysis
Glucose- 6 -phosphate is converted to fructose 6 -phosphate
| Isomerization reaction to make the first carbon free
26
What enzyme is used in the conversion of glucose 6-phosphate to fructose 6-phosphate
Phosphohexose isomerase with the help of Mg
27
What is the role of the reaction with phosphohexose isomerase
Makes the next step easier(C1 of fructose os easier to phosphorylate by PFK)
Allow for symmetrical cleavage by aldose
28
Is reaction with phosphohexose isomerase reversible/irreversible?
Reversible
29
What is the third step of glycolysis
Fructose 6-phosphate is converted to fructose 1,6-biphosphate by addition of PO3 to the first carbon
30
What is the other name for the third step of glycolysis and why
2nd priming phosphorylation, because ATP is used to give phosphate group. This hydrolyses is helped by Mg
31
What is the enzyme of the conversion of Fructose 6-phosphate to fructose 1,6-biphosphate?
PFK-1 or phosphofructokinase-1
32
What is the purpose of conversion of fructose 6-phosphate to phosphate to fructose 1,6-biphosphate
Generation of a symmetrical 6-carbon molecule
33
The reaction with PFK is reversible/irreversible
Irreversible
34
What is the final reaction of investment stage
Fructose 1,6 -biphosphate is lysed to dihydroxyacetone phosphate(DHAP) and glyceraldehyde 3-phosphate (G3P). ^ carbon sugar to 2 3 carbon sugars
35
What enzyme breaks Fructose 1,6 -biphosphate
aldolase
36
What is the role of breaking Fructose 1,6 -biphosphate
Generating high energy phosphate sugars
37
What is triose phosphate interconversion
Conversion between DHAP and G3P by triose phosphate isomerase
38
Is aldose and triose phospahte isomerase reversible/irrevesible
Reversible
39
Why there is triose phosphate interconversion
Because only GAP (glyceraldehyde-3-phosphate) is used in pay-off phase
40
What is the first reaction of pay off phase
GAP is converted to 1,3-biphosphoglycerate with the addition of inorganic phosphate group to aldehyde end
41
What is the enzyme that converts GAP to 1,3-biphosphoglycerate
Glyceraldehyde 3-phospahte dehydrogenase (GAPDH)
42
What is used to perform the first reaction of pay-off phase
Inorganic phosphate
| Nad+->NADH+H+
43
Is the reaction with GAPDH reversible/irreversible
reversible
44
Why GAPDH can be used as measurement control when giving a treatment for example
Because it is very important and produced a lot by our cells and its concentration do not vary
45
What is the step of the first ATP production
1,3-biphosphoglycerate gives off the phosphate group in the aldehyde end to ADP to produce ATP and 3-phosphoglycerate
46
What is the enzyme that helps the transfer of phosphate group to first ADP of glycolysis
Phosphoglycerate kinase with the help of Magnesium
47
Atp in glycolysis is produced by
Substrate level phosphorylation
48
Is phosphoglycerate kinase reversible/irreversible
Reversible
49
What is the migration of the phosphate
the step in pay off phase , when 3-phosphoglycerate is converted to 2-phosphoglycerate
50
What enzyme catalyses the conversion of 3-phosphoglycerate to 2-phosphoglycerate
Phosphoglycerate mutase with the help of Mg
51
Explain the mechanism of phosphoglycerate mutase
the enzyme has histidine in its AA sequence. When histidine is phosphorylated , then the enzyme becomes active. The mutase gives off its phosphate to the second carbon of glycerate and at the same time takes the phosphate group from the third carbon
52
Is the mutase reversible/irrevesible?
Reversible
53
What is step after 3-phosphoglycerate is converted to 2-phosphoglycerate
2-phosphoglycerate (2-PG) is converted to phosphoenolpyruvate (PEP) by dehydrating 2-PG. OH from the third carbon and H from the second carbon is taken away and the double bond between carbon 2 and 3 is created
54
What is the enzyme of conversion 2-PG to PEP
Enolase
55
What is the role of enolase
Generation of a high-energy phosphate compound
56
Is the reaction with enolase reversible/ irreversible
Reversible
57
What is the second step when ATP is produced
PEP is converted to pyruvate, giving off phosphate group from carbon 2 to ADP
58
What is the enzyme for conversion of PEP to pyruvate
Pyruvate kinase with the help of Mg and K
59
what does the last step of glycolysis includes
Tautomerization -when molecules with the same molecular formula but different connectivity - constitutional isomers, in other words, can easily interchange
60
The reaction of pyruvate production is reversible/irreversible
Irreversible
61
Fate of pyruvate
1) Hypoxic or anaerobic conditions (2 ethanol+2 CO2)- fermentation to ethanol in yeast
2) In aerobic conditions pyruvate->acetyl-CoA->TCA->CO2 and H2O
3) Hypoxic or anaerobic conditions to 2 lactate
62
What enzyme converts pyruvate to lactate. Reversible/irreversible?
Lactate dehydrogenase- reversible
63
What happens when lactate is produced in muscles
Lactate goes to the liver, where it is converted back to pyruvate and glucose through gluconeogenetic pathway
64
What is the name of the process when pyruvate is converted to lactate in tissues and then in the liver lactate is converted back to pyruvate
Cori cycle
65
Erythtocytes convert ___ to ___
Puruvate to lactate
66
Various carbohydrates can be broken down to ___
Various carbohydrates intermediates of glycolytic pathway
67
Regulation of anaerobic glycolysis in hypoxic conditions is performed by
Hypoxia Inducible Factor (HIF) which is activated in hypoxic conditions
68
Explain the regulation of HIF
There is an enzyme prolyl hydroxylase (PHD-2), this is the protein that senses oxygen tension.
In normoxic conditions, it PHD-2 induces HIF ubiquitination and thus degradation
When muscles work vigorously-> hypoxia, PHD-2 does not function, HIF-1 alpha is not degraded, but stabilized. HIF-betacomes and become a functional dimer with alpha.
Once they dimerize, they enter the nucleus and bind to HRE
69
what isomer of HIF is regulated and ubiquinated
Alpha
70
What another TF come with HIF alpha and beta
p300/CBP (cAMP response element Binding Protein)
71
CBP is regulated by
GPCR signaling
72
HIF target genes
```
GLUT 1/3
Hexokinase
PFK
Aldolase
GAPDH
Phosphoglycerate Kinase
Phosphoglycerate Mutase
Enolase
Lactate dehydrogenase
```
73
What tissues mainly depend on glucose
```
Brain
RBC
testes
renal medulla
embryo
```
74
How we can get glucose from inorganic sources
Lactate->pyruvate->PEP->glucose
GLucogenic AA->TCA->PEP->glucose
FA->glycerol->GAP->Glucose
CO2 fixation->3-phosphoglycerate->glucose
75
Recovery after vigorous exercise involves
gluconeogensis
76
where does gluconeogenesis occur ( tissues)
mainly liver (80%)
Intestinal epithelium
Renal cortex
77
Which three enzymes can drive glycolysis only forward?
Hexokinase
Phosphofructokinase-1
Pyruvate kinase
78
What is the last enzyme of glucoenogenesis
Glucose 6-phosphatase. It removes phosphate group from glucose
79
What enzyme does the reverse reaction of phosphofructokinase-1
Fructose 1,6-biphosphotase-1
80
Which step requires 2 enzymes in glcucoenogenesis
from pyruvate to phosphoenolpyruvate
It requires two enzymes: pyruvate carboxylase to transform pyruvate to oxaloacetate and PEP carboxykinase from oxaloacetate to phosphoenolpyruvate
81
What is needed to convert pyruvate to glucose
4 enzymes from glucoenogenesis + 7 reversible enzymes of glycolysis + 6 ATP+ 2 NADHs
82
Pyruvate To be converted to oxaloacetate needs to
Come inside mitochondria
| Pyruvate combines with bicarbonate with the help of pyruvate carboxylase->oxaloacetate
83
Where oxaloacetate can be converted to phosphoenolpyruvate
In cytosol or in mitochondria
84
What is used to convert oxaloacetate to phosphoenolpyruvate
GTP, but not ATP
| PEP carboxykinase
85
What is the alternative fate of G6P
Pentose phosphate pathway ( hexose monophosphate pathway)
86
hexose monophosphate pathway is more common in ( what type of cells)
Highly proliferative cells ( cancer cells, small intestinal cells)
- Cells with FA biosynthesis
- Cells that synthesis sterols ( cholesterol and steroids)
- Cells with oxidative stress
87
Why leucine and lysine do not contribute to intermediates of glucose synthesis
They are converted to acetyl-CoA, which is immediately converted to a ketone.
88
Two phases of pentose phosphate pathway
Non-oxidative phase and oxidative phase
89
What enzyme start pentose phosphate pathway and how
G6P is converted to 6-phosphogluconate with the help of G6P dehydrogenase that uses NADP+ to NADPH
90
What does phospho-pentose isomerase do
Converts Ribulose 5-phosphate to ribose 5-phosphate
91
Why phospho-pentose isomerase is important
Because ribose 5-phosphate is the precursor for multiple things (Nucelotides,coenzymes, DNA, RNA)
92
Another reason why phospho pentose isomerase and G6P dehydrogenase are important
They produce important reducing power NADPH
93
What enzymes and where are dependent on NADPH
FA synthesis in liver, kidney and lactating mammary gland
Cholesterol/steroid synthesis in liver,adrenal and gonads
Glutathionine reductase uses NADPH in tissues exposed to high O2 (cornea and RBC) and thus oxidative damage
94
What is the pathway of oxidative damage
O2->( mitochonsrial respirationmsulfa drugs,etc.)->Superoxide radical->hydrogen peroxide->Hydroxyl free radical
Hydroxyl free radical makes damage to lipids, proteins and DNA
95
What is the prevention of oxidative stress
Hydrogen peroxide is converted to water with the enzyme glutathione peroxidase. This enzymes requires 2 hydrogens from glutathion (GSH)
96
How GSH is regenerated
NADPH from pentose phosphate pathway donates hydrogens to GSSG (oxidized form) with the help of glutathione reductase
97
Describe non-oxidative phase of pentose phosphate pathway
Ribose 5-phosphate to Glcuose 6 phosphate in a big picture
ribose 5-phosphate is converted to xylulose 5-phosphate. Transketolase and transaldolases just convert one molecule to another without the addition of carbons or deletion, ultimetely leading to fructose 6-phosphate or Glyceraldehyde 3-phosphate
98
What reactions are reversible in non-oxidative phase
Practically all of them, except for fructose 1,6 biphosphatese
99
Where transketolases and transaldolases are over expressed
In cancer cells
100
How pentose phosphate pathway is regulated
NADPH which is generated can inhibit the reaction that generate NADPH
If the cell needs ATP, G6P will go through glycolysis
If the cell is exposed to oxidative stress or if cell needs a lot of nucleotide synthesize, it will undergo pentose phosphate pathway
