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Introduction to Metabolism and Pharmacology > Glycolysis 1 and 2 > Flashcards

Glycolysis 1 and 2 Flashcards

1
Q

What does Metabolism describe ?

A

It describes the integrated set of chemical reactions occur in the body and compromises both anabolism and catabolism

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2
Q

What is Anabolism ?

A

This is the synthesis of complex molecules from simpler ones (e.g. glycogen from glucose) with the energy necessary for synthesis being usually derived from ATP

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3
Q

What is Catabolism ?

A

This is the breakdown of energy-rich molecules (carbohydrate/lipid/protein) to simpler ones (CO2, H20 and NH3) with the energy released being “conserved” as adenosine triphosphate (ATP), for use in anabolic reactions

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4
Q

Catabolic and anabolic pathways together constitute ?

A

The cell’s metabolism

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5
Q

Define Oxidoreductases and give an example ?

A

Transfer of electrons

- Dehydrogenases

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6
Q

Define Transferases and give an example ?

A

Transfer of functional groups (Pi)

- Kinases

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7
Q

Define Hydrolases and give an example ?

A

Hydrolysis reactions

- Trypsin / Lipase

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8
Q

Define Lyases and give an example ?

A

Cleavage of C-C, C-N and other bonds, often forming a double bond

  • Isocitrate lyase
  • Pyruvate decarboxylase
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9
Q

Define Isomerases and give an example ?

A

Transfer of groups within a molecule

- Triose-phosphate isomerase

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10
Q

Define Ligases (synthetases) and give an example ?

A

Bond formation coupled to ATP hydrolysis

- Pyruvate carboxylase

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11
Q

What are the 3 main parts of Glycolysis ?

A
  1. Energy investment
  2. Cleavage
  3. Energy generation
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12
Q

What are many metabolic reactions controlled by ?

A

The energy status of the cell

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13
Q

What is the Energy charge (EC) ?

A

It is an index used to measure the energy status of a cell and is related to the cellular concentrations of the adenylate nucleotides (AMP / ADP / ATP)

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14
Q

Explain the reaction ΔG<0 ?

A
  • The reaction is spontaneous
  • Products have less free energy than reactants and so are more stable than the reactants
    Their formation is considered to be “ downhill “ (spontaneous)
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15
Q

Explain the reaction ΔG>0 ?

A

Reaction is not spontaneous

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16
Q

What is Glycolysis ?

A

Metabolic pathway in which glucose is transformed to pyruvate with production of a small amount of energy in the form of ATP or NADH

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17
Q

What kind of process is Glycolysis ?

A

An anaerobic respiration (it does not require oxygen)

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18
Q

Glycolysis pathway is used by ?

A

Anaerobic as well as aerobic organisms

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19
Q

What happens in Glycolysis ?

A

One molecule of glucose is converted into two molecules of pyruvate

20
Q

In eukaryotic cells, glycolysis takes place in?

A

The cytosol

21
Q

What does it yield ?

A

2 ATP and 2 NADH per glucose

22
Q

Explain Location and Glucose Affinity for GLUT 1 ?

A
  • Erythrocytes, other tissues

- High glucose affinity

23
Q

Explain Location and Glucose Affinity for GLUT 2 ?

A
  • Liver, pancreatic B cells

- Low glucose affinity

24
Q

Explain Location and Glucose Affinity for GLUT 3 ?

A
  • Brain, other tissues

- High glucose affinity

25
Q

Explain Location and Glucose Affinity for GLUT 4 ?

A
  • Muscles, adipose

- Low glucose affinity

26
Q

Briefly explain the uptake of glucose ?

A
  1. The transport protein has a binding site for glucose that is open to the outside of the cell
  2. Glucose binds to the binding site
  3. This binding causes the protein to change shape, exposing glucose to the inside of the cell
  4. Glucose passes into the cell and protein returns to its original shape
27
Q

Give an overview of Glycolysis ? (Energy-Investment Stage)

A
  1. Glucose is phosphorylated by ATP to form glucose 6-phosphate
  2. The atoms of glucose 6-phosphate are rearranged to form fructose 6-phosphate. Fructose 6-phosphate is phosphorylated by ATP to form fructose 1,6-biphosphate
  3. Fructose 1,6-biphosphate is divided to form glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP)
  4. DHAP is rearranged to form another G3P
28
Q

What is Hexokinase inhibited by ?

A

High levels of G6P inhibit (allosterically)

29
Q

Why is this inhibition important ?

A

It’s a control step; it prevents over consumption of cellular ATP to form G-6-P when glucose is not limiting

30
Q

In liver and pancreatic β-cells, Hk is replaced by ?

A

Gk (glucokinase)

31
Q

Gk has higher Km than Hk. How is it activated ?

A

By high blood glucose and insulin but NOT inhibited by G6P

32
Q

So what does Glucokinase allow the liver to remove ?

A

Excess glucose for glycogen synthesis and minimise, after eating, hyperglycemia

33
Q

What does Phosphoglucose Isomerase (PGI) convert ?

A

G6P into a fructose-based molecule through acid-base catalysis

34
Q

What Phosphofructokinase transfer ?

A

A phosphate group from ATP to fructose-6-phosphate. This makes fructose-6-biphosphate

35
Q

What can Phosphofructokinase-1 (PFK-1) be allosterically inhibited by and how can it be reversed ?

A

PFK-1 is allosterically inhibited by ATP (-) and this is reversed by AMP (+)

36
Q

What effects does Citrate have on PFK-1 ?

A

Inhibits PFK-1 (high citrate signals sufficient TCA cycle intermediates so not necessary to metabolise any more glucose via PFK-1)

37
Q

What effect does F2, 6-BP have on PFK-1 ?

A

It activates PFK-1

38
Q

What effects does H+ have on PFK-1 ?

A

Inhibit PFK-1 when pH falls preventing excessive formation of lactic acid (prevents acidosis)

39
Q

Explain the Energy-Conserving Stage ? (Continued cycle from Energy-Investing Stage)

A
  1. Inorganic phosphates are added to the two G3P, and two NAD+ are reduced.
  2. Two ADP are phosphorylated by substrate-level phosphorylation to form two ATP
  3. The remaining phosphates are moved to the middle carbons. A water molecule is removed from each substrate
  4. Two ADP are phosphorylated by substrate-level phosphorylation to form two ATP. Two pyruvic acid are formed
40
Q

Pyruvate kinase is the last enzymatic reaction in glycolysis. What does it aid ?

A

It aids in the conversion of phosphoenolpyruvate (PEP) to pyruvate, thereby producing ATP

41
Q

What happens when Pyruvate kinase is deficient ?

A
  • Sufficient amounts of ATP are not available for red blood cell survival
  • Red cells are removed by the reticuloendothelial cells, particularly the spleen
  • Build up of 2,3-DPG occurs which aids in oxygen off loading into tissues
42
Q

Explain Pyruvate Kinase Deficiency ?

A
  • No ATP for Na/K pumps to maintain cell shape

- RBC’s lack mitochondria; rely on glycolysis for ATP

43
Q

Briefly explain Hemolytic anemia ?

A

Red blood cells swell and lyse

44
Q

What process is involved in the Cori cycle ?

A

Gluconeogenesis - process of making glucose

Glycolysis - breakdown of glucose by enzymes

45
Q

What catalyses the reaction of Pyruvate into Acetyl-CoA ?

A

Pyruvate Dehydrogenase Complex

46
Q

What is Pyruvate inhibited by ?

A

Its products - Acetyl-CoA and NADH

Introduction to Metabolism and Pharmacology (16 decks)

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