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Biochemistry II > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

What is the function of glycolysis?

A

To break down glucose

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2
Q

What are the products of glycolysis?

A

ATP, NADH, pyruvate, lactate, and alanine

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3
Q

In aerobic organisms, glycolysis yields precursors to what?

A

The aerobic system

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4
Q

What is the first half of glycolysis characterized by?

A
  • Bringing glucose into the cell (Facilitated diffusion and adding a phosphate to prevent it from leaving)
  • Change glucose into an energy rich sugar (fructose 1, 6 bisphosphate)
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5
Q

What is the second half of glycolysis characterized by?

A
  • Getting ATP

- Creating an end product that can be further oxidized (pyruvate)

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6
Q

Where does glycolysis take place?

A

Cytosol

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7
Q

The first half of glycolysis begins with phosphorylation of glucose by hexokinase. What is the product of this reaction?

A

Hexokinase adds a phosphate group to glucose, which prevents it from leaving the cell. (glucose to glucose 6-phosphate)

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8
Q

Isomerization of glucose 6-phosphate by phosphoglucose isomerase is the second step in the first half of glycolysis. What is the product of this reaction?

A

It converts glucose 6-phosphate to fructose 6-phosphate (aldehyde to a ketone)

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9
Q

In the first half of glycolysis, there is a second round of phosphorylation by phosphofructokinase (PFK) after isomerization. What is the product of this reaction?

A

It converts fructose 6-phosphate to fructose 1, 6-bisphosphate

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10
Q

This term is used to describe the influencing of an enzyme activity by a change in the conformation of the enzyme, brought about by the noncompetitive binding of a nonsubstrate at a site (allosteric site) other than the active site of the enzyme.

A

Allosterism

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11
Q

This is an allosteric enzyme, very influential, and acts during the rate limiting step in glycolysis.

A

Phosphofructokinase (PFK)

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12
Q

In general, what reactions occur in the first half of glycolysis?

A
  • Phosphorylation (glucose to glucose 6-phosphate)
  • Isomerization (glucose 6-phosphate to fructose 6-phosphate)
  • Phosphorylation (fructose 6-phosphate to fructose 1,6-bisphosphate
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13
Q

In the second half of glycolysis there is a split that occurs. How does this happen and what molecules are involved?

A

Fructose 1,6-bisphosphate is split by aldolase into dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3 phosphate (G3P)

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14
Q

After the split in the second half of glycolysis, DHAP and G3P undergo isomerization via what enzyme? What is produced?

A

Triose phosphate isomerase. Two pyruvate molecules are made for every glucose broken down

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15
Q

After isomerization in the second half of glycolysis, G3P is converted to 1, 3-Bisphosphoglycerate via what reaction? What enzyme does this?

A

Oxidative phosphorylation via G3P dehydrogenase

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16
Q

After oxidative phosphorylation, ATP is created by converting 1,3-Bisphophoglycerate into ____ via ____.

A

3-Phosphoglycerate via phosphoglycerate kinase

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17
Q

This is the process by which a phosphate group is being provided by the initial substrate to help make ATP.

A

Substrate level phosphorylation

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18
Q

After ATP is created during the second half of glycolysis, 3-Phosphoglycerate is converted into ____ via ____. This process is known as what?

A

2-Phosphoglycerate via phosphoglycerate mutase. This process is known as mutation

19
Q

After mutation occurs in the second half of glycolysis, 2-Phosphoglycerate is converted into ___ via ___. This process is known as what?

A

Phosphoenolpyruvate via enolase. This process is known as dehydration

20
Q

After dehydration occurs in the second half of glycolysis, phosphoenolpyruvate is converted into ____ via ____. Is this reaction reversible or irreversible?

A

Pyruvate via pyruvate kinase. This is an irreversible reaction. ATP is produced at this step

21
Q

What are some other substances can enter into the glycolytic pathway?

A

Sucrose (glucose and fructose) and Lactose (glucose and galactose)

22
Q

Fructose can be phosphorylated into ____ by ____.

A

Fructose 6P by hexokinase

23
Q

After fructose is phosphorylated, it could enter glycolysis, but it doesn’t happen much. Why?

A

Hexokinase’s affinity for glucose is 20 times higher than its affinity for fructose

24
Q

What are the steps of the fructose 1-phosphate pathway?

A
  • Fructose is converted to fructose 1P by fructokinase
  • Fructose 1P is broken down into glyceraldehyde and dihydroxyacetone phosphate by fructose 1P aldolase
  • Glyceraldehyde is then converted to glyceraldehyde 3P by triose kinase
25
Q

How is galactose converted into glucose 6P?

A
  1. Galactose + ATP–>galactose 1P and ADP (galactokinase)
  2. Galactose 1P + UDP (uridine diphosphate) Glucose –> UDP-Galactose + Glucose 1P (transferase
  3. UDP Galactose –> UDP Glucose (epimerase)
  4. Glucose 1P –> Glucose 6P (mutase)
26
Q

How is phosphofructokinase inhibited?

A
  • Binding of ATP decreases its activity
  • Decreased pH
  • Citrate
27
Q

How does fructose 2,6-bisphosphate influence phosphofructokinase (PFK)?

A

It is made from fructose 6P and activates PFK and subsequent glycolysis. In addition to this it inhibits gluconeogenesis

28
Q

What is the main role of hexokinase in glycolysis?

A

It is the enzyme that catalyzes the first step in glycolysis

29
Q

What enzyme inhibits hexokinase?

A

Phosphofructokinase

30
Q

This is an alternative form of hexokinase that is found in liver and Beta cells of the pancreas. It also makes G6P only if glucose is abundant.

A

Glucokinase

31
Q

What are the differences between glucokinase and hexokinase?

A

Glucokinase: found in the liver, high Km, not inhibited by glucose 6P, stimulated by insulin and fructose
Hexokinase: found in the muscle, low Km, inhibited by glucose 6P

32
Q

What are the four important things to know about glucokinase?

A
  • Stimulated by insulin
  • Stimulated by fructose
  • High Km (takes more reactant to make it go faster)
  • It is not inhibited by its product (glucose 6P)
33
Q

This enzyme catalyzes the third “irreversible” step in glycolysis, its stimulated by fructose 1, 6 BP, and it is feedforward to allow it to keep up with the oncoming intermediates.

A

Pyruvate kinase

34
Q

This amino acid is one reaction away from becoming pyruvate.

A

Alanine

35
Q

Pyruvate kinase is stimulated by ____ and inhibited by ____.

A

Stimulated by fructose 1,6-bisphosphate

Inhibited by ATP or alanine

36
Q

This hormone is secreted when blood glucose is low and is used to elevate blood glucose.

A

Glucagon

37
Q

How is lactic acid produced?

A

Pyruvate is converted into lactate by lactate dehydrogenase and the conversion of NADH + H+ to NAD+

38
Q

What is the important reaction that lactate dehydrogenase is utilized in?

A

Pyruvate + NADH —> Lactate + NAD+

39
Q

This substance is produced when glycolysis runs fast.

A

Lactic acid

40
Q

A moderate production of lactate does what to glycolysis? A large production?

A

Moderate: speeds up glycolysis
Large: inhibits glycolysis

41
Q

This process is characterized by the conversion of glucose to lactic acid in the presence of oxygen (Warburg effect) and is uniquely observed in cancers.

A

Aerobic glycolysis

42
Q

By running glycolysis fast, what type of intracellular and pericellular conditions are created?

A

Acidic conditions

43
Q

This is an ATP-generating process in which organic compounds act as both donors and acceptors of electrons. This process can occur in the absence of oxygen.

A

Fermentation

Biochemistry II (16 decks)

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