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Biochemistry I > Chapter 11: Glycolysis > Flashcards

Chapter 11: Glycolysis Flashcards

1
Q

Glycolysis (sugar-splitting Grk)

A
  • Either in presence or absence of oxygen
  • Happens in cytoplasm
  • Irreversible
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2
Q

Key pathway of carbohydrate metabolism in red blood cells

A
  • Glycolysis
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3
Q

Two parts to glycolysis

A
  • First part: priming phase/input (energy investment)

- Second part: payoff phase/output (energy harvesting)

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4
Q

Second phase production

A
  • 4 molecules of ATP
  • 2 molecules of NADH
  • Net yield of 2 molecules of ATP from ADP and Pi
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5
Q

Substrate phosphorylation

A
  • Important in glycolysis

- Doesn’t require ETC (oxidative phosphorylation does req oxygen)

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6
Q

Substrate level phosphorylation

A
  • Glycolysis in cytosol
  • Pyruvate (via translocase into mitochondria)
  • Uses high energy molecules (not using the ETC)
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7
Q

Throughout the 10 steps of glycolysis

A
  • Glucose is split in two
  • Produces pyruvate (3C sugars)
  • Transfers energy to ATP and NADH/ H+
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8
Q

1 NADH produces

A
  • 2.5 ATP for a total of 5 ATP
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9
Q

Periods of starvation, we have to go around pyruvate

A
  • It is irreversible
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10
Q

Glycolytic production under aerobic conditions

A
  • Pyruvate > Acetyl-SCoA (enters CAC)

- Leads to more complete oxidation of glucose

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11
Q

PFK-1

A
  • Allosteric enzyme

- Catalyzes the first irreversible step in glycolysis

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12
Q

Second most well known protein deficiency in humans

A
  • Pyruvate kinase
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13
Q

Most well known protein deficiency in humans

A
  • Phosphofructokinase 1
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14
Q

All intermediates in the input phase of glycolysis

A
  • Are hexose sugars
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15
Q

First stage of glycolysis

A
  • 6 carbon hexose is activated
  • Cleaved to two 3 carbon fragments
  • 2 ATP are consumed
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16
Q

Enzymes involved in first stage of glycolysis

A
  • Hexokinase
  • Phosphoglucose isomerase
  • Phosphofructokinase-1
  • Aldolase
  • Triose phosphate isomerase
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17
Q

Hexokinase depends on

A
  • ATP dependent
  • Mg++ dependent phosphorylation of glucose > glucose-6-phosphate
  • First irreversible pathway
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18
Q

Hexokinase function/mechanism

A
  • Nonionic glucose > anion (trapped in the cell)
  • Glucose is activated (can be further metabolized)
  • May also phosphorylate fructose > fructose-6-phosphate
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19
Q

Hexokinase IV

A
  • High Km glucokinase in liver
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20
Q

Phosphofructokinase-1 utilizes

A
  • Uses a second ATP molecule

- Converts fructose-6-phosphate > fructose-1,6-bisphosphate (symmetrical molecule)

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21
Q

Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate by PFK-1

A
  • Reaction is not readily reversible
  • Second priming step
  • Major committed step
  • Irreversible steps cannot be used in glycogenolysis
  • First irreversible step that is unique to glycolysis
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22
Q

Fructose-1,6-bisphosphatase (F-1,6-BPase) of gluconeogenesis

A
  • Hydrolytic enzyme

- Opposes PFK-1

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23
Q

Phosphoglucose isomerase

A
  • Converts aldose to ketose in step 2

- Near equilibirum reversible isomerization (not control point)

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24
Q

Aldolase function

A
  • Reversible cleavage of a symmetrical hexose between C3 and C4 in step 4
  • Products are rapidly removed
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25
Q

Triose phosphate isomerase converts

A
  • Near equilibrium reaction

- Converts dihydroxyacetone (ketose) to glyceraldehyde-3-phosphate (aldose)

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26
Q

Triose phosphatate isomerase produces

A
  • Two glyceraldehyde-3-phosphate molecules after reaction 5

- Only glyceraldehyde-3-phosphate continues in the pathway

27
Q

Investing phase overall products

A
  • Two glyceraldehyde-3-phosphates
28
Q

Glycolysis energy investing phase free energy change

A
  • Endergonic reaction (consumes energy)
29
Q

Second stage of glycolysis

A
  • The two glyceradlehyde-3-phosphate > 2 molecules of pyruvate (3C)
  • 4 molecules of ATP are produced and (NADH) is generated
30
Q

NADH in the presence of oxygen can be used

A
  • Generates more ATP from the mitochondrial ETC
31
Q

All energy payoff phase intermediates

A
  • Triose sugars
32
Q

Enzymes of stage two

A
  • Glyceraldehyde-3-phosphate dehydrogenase
  • 3-phosphoglycerate kinase
  • Phosphoglycerate mutase
  • Enolase
  • Pyruvate kinase
33
Q

Glyceraldehyde-3-phosphate dehydrogenase

A
  • Oxidation of GAP producing 1,3-BPG with production of NADH

- If NAD is depleted, this step will not occur

34
Q

NAD in glycolysis

A
  • Generated from ETC and exc m

- Required to proceed in both aerobic and anaerobic conditions

35
Q

Phosphoglycerate kinase reaction

A
  • Reversible

- Generates ATP by substrate level phosphorylation

36
Q

High glycolytic energy intermediate

A
  • Substrate level phosphorylation
37
Q

Phosphoglycerate mutase

A
  • Near equilibrium

- Shifts phosphate group C3 –> C2

38
Q

Enolase dehydration reaction

A
  • Catalyzes dehydration without cleavage
  • Near equilibrium, reversible
  • Inhibited by F-
39
Q

Fluoride

A
  • Inhibits enolase activity

- RBCs metabolize blood sugar, so fluoride inhibits glycolysis pathway (prevents blood sugar metabolism in RBCs)

40
Q

Pyruvate kinase

A
  • Produces one additional ATP per original G3P input, and the final product, pyruvate
  • Irreversible, exergonic
41
Q

Pyruvate kinase control

A
  • Tightly controlled
  • Allosteric control
  • Covalent modification
42
Q

Pyruvate kinase deficiency (2nd most common)

A
  • Non-spherocytic hemolytic anemia

- If mutated, RBC cannot metabolize sugar, but protected against malaria

43
Q

Pyruvate under anaerobic conditions

A
  • Converted to lactate

- NADH produced cannot be reoxidized by O2

44
Q

Lactate dehydrogenase (under anaerobic conditions) regenerates

A
  • NAD+ as pyruvate > reduced

- Allows glycolysis to continue (NAD+ used by G3PDh)

45
Q

Pyruvate under aerobic conditions produces

A
  • NADH that can enter the ETC

- Regenerates NAD+

46
Q

Major difference of aerobic vs. anaerobic conditions

A
  • The amount of ATP formed
  • 2.5 under aerobic conditions
  • No ATP in anaerobic conditions
47
Q

Lactic acid production from anaerobic glycolysis causes

A
  • Generation of H+
48
Q

Substrate level phosphorylation in payoff phase produces

A
  • 4 ATP overall
  • 2 ATPs from 3-phosphoglycerate kinase
  • 2 ATPs from Pyruvate kinase
  • Net = 2 ATPs (4 produced, 2 used for priming)
49
Q

Oxidative phosphorylation produces

A
  • Glyceraldehyde-3-phosphate DH (2 NADHs/glucose)
  • Each NADH –> 2.5 ATPs
  • Total of 5 ATPs and glucose
50
Q

Glycolysis total energy production

A
  • 7 ATPs

- Glucose

51
Q

Other sugars that can be metabolized in glycolysis

A
  • Galactose
  • Fructose
  • Mannose
52
Q

Galactose is phosphorylated by

A
  • Galactokinase in the hepatocyte
53
Q

Hexokinase in muscle phosphorylates

A
  • Fructose in muscle cells

- Directly enters glycolysis via G3P

54
Q

Fructose in liver in phosphorylated by

A
  • Fructokinase in liver

- Enters glycolysis through longer pathway via G3P at end

55
Q

Glycolytic enzyme deficiencies primarily effect

A
  • Primarily effect RBC’s
56
Q

Hemolytic anemia typically caused by deficiency in these glyolytic enzymes

A
  • PFK-1
  • Phosphoglucose isomerase
  • Triose phosphate isomerase
  • Phosphoglycerate kinase
57
Q

Tauri Disease

A
  • Caused by Phosphofructokinase-1 deficiency in muscle cells
58
Q

Non-spherocytic anemia

A
  • Caused by deficiency of the pyruvate kinase enzyme in erythrocytes
59
Q

Hereditary fructose intolerance

A
  • Result of a deficiency in the hepatic aldolase-B enzyme
60
Q

alpha-D-galactose-1-phosphate uridyltransferase enzyme results in

A
  • Galactosemia when UDP-glucose is absent
61
Q
  • Epimerization of galactose by galactose 1-P uridyl transferase produces
A
  • Glucose-1-Phosphate
62
Q
  • Phosphoglucomutase produces
A
  • Glucose-6-phosphate
63
Q
  • Phosphoglycerate kinase reverse reaction
A
  • Transfer of a phosphate group from an ATP to another molecule
64
Q

Pyruvate kinase at the end of glycolytic pathway

A
  • MAJOR regulatory branch point in the overall pathway

Biochemistry I (34 decks)

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