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YEAR 2 HUMAN BIOCHEMISTRY > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

Glycolysis is the central pathway for what?

A

Carbohydrate metabolism

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2
Q

What are 3 examples of organisms that use glycolysis

A

Mammals, bacteria and plants

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3
Q

Is glycolysis an anaerobic or aerobic process?

A

It is an anaerobic process

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4
Q

How many phases are involved in glycolysis

A

There are 2 phases in glycolysis

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5
Q

How many carbons does glucose have?

A

Glucose has 6 carbons (C6)

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6
Q

Glycolysis involves the breakdown of glucose (C6) into what? And what is the result of this?

A

Breakdown of glucose into 2 molecules of pyruvate
Results in a net production of 2 ATP molecules

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7
Q

How many carbons does a Pyruvate molecule have?

A

3 carbons

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8
Q

Where does glycolysis occur in mammalian cells?

A

Glycolysis occurs in the cytosol of mammalian cells

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9
Q

How many reactions does glycolysis consist of?

A

Consists of 10 reactions

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10
Q

Describe what is involved in phase 1 of glycolysis

A
  • Converts glucose to two glyceraldehyde 3-phosphate molecules
  • energy requiring phase (catabolic, or energy investment)
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11
Q

Describe what is involved in phase 2 of glycolysis

A
  • Generates two pyruvate molecules
  • Energy producing phase (anabolic, or energy payoff)
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12
Q

What are the 4 products of glycolysis?

A

•2x Pyruvate
•4x ATP
•2x NADH
•2x H2O

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13
Q

What are the 3 irreversible reactions in the glycolysis pathway?

A

•Hexokinase
•Phosphofructokinase
•Pyruvate kinase

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14
Q

What happens in reaction 1 of glycolysis?

A

Reaction 1 = Hexokinase
- Glucose is irreversibly phosphorylated into Glucose-6-phosphate
- Powered by the hydrolysis of ATP

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15
Q

What is the transfer of a phosphate group from ATP onto another molecule called? And why is it important?

A
  • Transfer of a phosphate group from ATP onto another molecule is called a phosphoryl transfer
  • Important to trap Glucose inside the cells
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16
Q

What are the names in order of reactions 1-10 in glycolysis

A

1= Hexokinase
2= Phosphoglucose isomerase
3= Phosphofructokinase
4=Aldolase
5= Triose phosphate isomerase
6= Glyceraldehyde 3-phosphate dehydrogenase
7= Phosphoglycerate kinase
8= Phosphoglyceromutase
9= Enolase
10= Pyruvate kinase

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17
Q

What is involved in reaction 2 of ** glycolysis **

A
  • isomerisationof glucose-6-phosphateto fructose-6-phosphate​
  • the reaction is the conversion of analdosesugar intoaketosesugar
  • reaction 2 = Phosphoglucose isomerase

Aldose = Aldehyde group
Ketose = Ketone group

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18
Q

What is involved in reaction 3 of glycolysis?

A
  • Reaction 3= Phosphofructokinase
  • Fructose-6-phosphate isphosphorylatedagain to generatefructose-1,6-bisphosphate​
  • This is the second phosphoryl transfer reaction of glycolysis
19
Q

What 2 things is Phosphofructokinase described as?

A

Phosphofructokinase is an isoenzyme and allosteric

20
Q

Describe the term allosteric

A
  • Enzymes that have an additional binding site for effector molecules other than the active site
    -ATP is an allosteric effector​
  • high levels inhibit the enzyme, low levels activate
21
Q

Isoenzymesare a combination of what subunits?

A
  • M4, M3, M2L2, ML3, L4
22
Q

What does phosphofructokinase exit as?

A
  • Exists as a tetramer
    -The tetramer is composed of L and M subunits​
23
Q

What are muscles and the liver rich in?

A

Muscles are rich in M4; the liver is rich in L4​

24
Q

What is involved in reaction 4 of glycolysis?

A
  • Fructose-1,6-bisphosphate iscleavedinto two 3-carbonfragments​
  1. Dihydroxyacetonephosphate – aketose​
  2. Glyceraldehyde 3-phosphate – an aldose
25
What is involved in reaction 5 of glycolysis?
- reaction 5= Triose phosphate isomerase - The subsequent reaction uses only glyceraldehyde 3-phosphate​ - Dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde-3-phosphate - When glyceraldehyde 3-phosphate is used, the equilibrium is restored by conversion of DHAP to glyceraldehyde 3-phosphate​  ​
26
Summarise phase 1 of glycolysis
- Phase 1= involves reactions 1 to 5 - Catabolic, energy investment phase - 2 molecules of ATP have been used - Glucose is converted to two molecules of glyceraldehyde 3-phosphate -The key intermediate in this series of reactions is fructose-1,6-bisphosphate. The enzyme that catalyses this reaction, phosphofructokinase, is subject to allosteric control
27
What is involved in reaction 6 of glycolysis?
- Reaction 6= Glyceraldehyde 3-phosphate dehydrogenase - The first reaction that begins the conversion to pyruvate - involves the oxidation of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate.​ - This reaction involves addition of an inorganic phosphate group (Pi). ​ -NAD+ is reduced to NADH
28
What is involved in reaction 7 of glycolysis?
- Reaction 7=Phosphoglycerate kinase - 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate by Phosphoglycerate kinase.​ -This step involves another reaction in which ATP is produced  - ATP is produced by phosphorylation of ADP​ -1,3-bisphosphoglycerate transfers a phosphate group to ADP.  - known as substrate-level phosphorylation​ - Reaction is catalysed by phosphoglycerate kinase and “pays off” the ATP debt created by the priming reactions in the first phase.
29
What is involved in reaction 8 of glycolysis?
- Reaction 8= Phosphoglyceromutase - The next step involves the isomerization of 3-phosphoglycerate to 2-phosphoglycerate​ - A “mutase” catalyses migration of a functional group within a substrate.
30
What is involved in reaction 9 of glycolysis?
- Reaction 9= Enolase - Enolase = Phosphopyruvate hydratase - 2-phosphoglycerate loses one molecule of water, producing Phosphenolpyruvate​ - Enolase catalyses the reaction and requires a Mg2+ cofactor​
31
What are the 3 isoenzymes involved in reaction 9 of glycolysis and give key features of all 3
1. αα or non-neuronal enolase (NNE) - Found in a variety of tissues, including liver, brain, kidney, spleen, adipose -Present at some level in all normal human cells 2. ββ or muscle-specific enolase (MSE) - this enzyme is largely restricted to muscle -where it is present at very high levels 3. γγ or neuron-specific enolase (NSE): - Expressed at very high levels in neurons and neural tissues - can account for as much as 3% of total soluble protein - expressed at much lower levels in most mammalian cells.
32
What is involved in reaction 10 of glycolysis?
- Reaction 10= pyruvate kinase - Phosphoenolpyruvate contains a high energy bond - Transfers its phosphate group to ADP, producing ATP and pyruvate. - Another example of substrate level phosphorylation​ - Reaction is catalyzed by pyruvate kinase
33
Summarise phase 2 of glycolysis
- Phase = Reactions 6-10 - Anabolic - energy producing phase - Two molecules of pyruvate are produced for each molecule of glucose that entered the pathway. - These reactions involve the production of 2 molecules of NADH, and the net production of 2 ATP for each molecule of glucose.
34
What are the metabolic fates of NADH and pyruvate in mammals after being produced by glycolysis?
- NADH can be recycled via aerobic or anaerobic pathways:​ - In aerobic conditions (O2 is available), NADH is re-oxidized in the electron transport pathway, making ATP in oxidative phosphorylation. - 3 molecules of ATP can be made from one molecule of NADH.​ - In anaerobic conditions (O2 is not available), NADH is re-oxidized by lactate dehydrogenase (LDH) which provides NAD+ for more glycolysis.
35
Under anaerobic conditions: eg. Actively contracting muscle. What is the most important pathway for the regeneration of NADH+ ?
The most important pathway for the regeneration of NAD+ is reduction of pyruvate to lactate.
36
What is the goal of aerobic metabolism of pyruvate?
- Goal is to get pyruvate into the citric acid cycle  -where the products of glucose can be completely oxidised, leading to the production of many ATP molecules.​ 2 steps required to achieve this:​ Convert pyruvate into acetyl-CoA​ Put the acetyl CoA into the citric acid cycle. 
37
What part of the cell contains the enzymes that perform glycolysis?
Cytosol
38
Complete the following: In the glycolytic pathway, one molecule of the 6-carbon compound, ---------- is converted into 2 molecules of the 3-carbon compound, -------------.
1. glucose 2. Pyruvate
39
Before glycolysis can occur, glucose must be trapped inside the cell. Explain how this is achieved
Glucose is phosphorylated to glucose 6-phosphate by hexokinase.
40
Name two glycolytic reactions that involve phosphoryl transfers.
Hexokinase and phosphofructokinase
41
Name one glycolytic reaction that is an example of substrate level phosphorylation.
The one catalysed by phosphoglycerate kinase or pyruvate kinase
42
Glyceraldehyde 3-phosphate is oxidised during glycolysis. Choose the option below which best explains what happens to the hydrogen atom and the electron that are removed during oxidation. a. They reduce NAD+ b. They oxidise NAD+ c. They are transferred to ATP d. They are eliminated as methane
a. They reduce NAD+
43
Glycolysis is a pathway which occurs: a. Eukaryotic cells only b. Prokaryotic cells only c. Most muscle cells d. Virtually all cells
d. Virtually all cells
44
If 1NADH yields 3ATP molecules by oxidative phosphorylation, how many ATP molecules are made from one molecule of glucose undergoing glycolysis?
8

YEAR 2 HUMAN BIOCHEMISTRY (12 decks)

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