Chapter 11: Glycolysis Flashcards
1
Q
Glycolysis (sugar-splitting Grk)
A
- Either in presence or absence of oxygen
- Happens in cytoplasm
- Irreversible
2
Q
Key pathway of carbohydrate metabolism in red blood cells
A
- Glycolysis
3
Q
Two parts to glycolysis
A
- First part: priming phase/input (energy investment)
- Second part: payoff phase/output (energy harvesting)
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
5
Q
Substrate phosphorylation
A
- Important in glycolysis
- Doesn’t require ETC (oxidative phosphorylation does req oxygen)
6
Q
Substrate level phosphorylation
A
- Glycolysis in cytosol
- Pyruvate (via translocase into mitochondria)
- Uses high energy molecules (not using the ETC)
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+
8
Q
1 NADH produces
A
- 2.5 ATP for a total of 5 ATP
9
Q
Periods of starvation, we have to go around pyruvate
A
- It is irreversible
10
Q
Glycolytic production under aerobic conditions
A
- Pyruvate > Acetyl-SCoA (enters CAC)
- Leads to more complete oxidation of glucose
11
Q
PFK-1
A
- Allosteric enzyme
- Catalyzes the first irreversible step in glycolysis
12
Q
Second most well known protein deficiency in humans
A
- Pyruvate kinase
13
Q
Most well known protein deficiency in humans
A
- Phosphofructokinase 1
14
Q
All intermediates in the input phase of glycolysis
A
- Are hexose sugars
15
Q
First stage of glycolysis
A
- 6 carbon hexose is activated
- Cleaved to two 3 carbon fragments
- 2 ATP are consumed
16
Q
Enzymes involved in first stage of glycolysis
A
- Hexokinase
- Phosphoglucose isomerase
- Phosphofructokinase-1
- Aldolase
- Triose phosphate isomerase
17
Q
Hexokinase depends on
A
- ATP dependent
- Mg++ dependent phosphorylation of glucose > glucose-6-phosphate
- First irreversible pathway
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
19
Q
Hexokinase IV
A
- High Km glucokinase in liver
20
Q
Phosphofructokinase-1 utilizes
A
- Uses a second ATP molecule
- Converts fructose-6-phosphate > fructose-1,6-bisphosphate (symmetrical molecule)
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
22
Q
Fructose-1,6-bisphosphatase (F-1,6-BPase) of gluconeogenesis
A
- Hydrolytic enzyme
- Opposes PFK-1
23
Q
Phosphoglucose isomerase
A
- Converts aldose to ketose in step 2
- Near equilibirum reversible isomerization (not control point)
24
Q
Aldolase function
A
- Reversible cleavage of a symmetrical hexose between C3 and C4 in step 4
- Products are rapidly removed
25
Triose phosphate isomerase converts
- Near equilibrium reaction
| - Converts dihydroxyacetone (ketose) to glyceraldehyde-3-phosphate (aldose)
26
Triose phosphatate isomerase produces
- Two glyceraldehyde-3-phosphate molecules after reaction 5
| - Only glyceraldehyde-3-phosphate continues in the pathway
27
Investing phase overall products
- Two glyceraldehyde-3-phosphates
28
Glycolysis energy investing phase free energy change
- Endergonic reaction (consumes energy)
29
Second stage of glycolysis
- The two glyceradlehyde-3-phosphate > 2 molecules of pyruvate (3C)
- 4 molecules of ATP are produced and (NADH) is generated
30
NADH in the presence of oxygen can be used
- Generates more ATP from the mitochondrial ETC
31
All energy payoff phase intermediates
- Triose sugars
32
Enzymes of stage two
- Glyceraldehyde-3-phosphate dehydrogenase
- 3-phosphoglycerate kinase
- Phosphoglycerate mutase
- Enolase
- Pyruvate kinase
33
Glyceraldehyde-3-phosphate dehydrogenase
- Oxidation of GAP producing 1,3-BPG with production of NADH
| - If NAD is depleted, this step will not occur
34
NAD in glycolysis
- Generated from ETC and exc m
| - Required to proceed in both aerobic and anaerobic conditions
35
Phosphoglycerate kinase reaction
- Reversible
| - Generates ATP by substrate level phosphorylation
36
High glycolytic energy intermediate
- Substrate level phosphorylation
37
Phosphoglycerate mutase
- Near equilibrium
| - Shifts phosphate group C3 --> C2
38
Enolase dehydration reaction
- Catalyzes dehydration without cleavage
- Near equilibrium, reversible
- Inhibited by F-
39
Fluoride
- Inhibits enolase activity
| - RBCs metabolize blood sugar, so fluoride inhibits glycolysis pathway (prevents blood sugar metabolism in RBCs)
40
Pyruvate kinase
- Produces one additional ATP per original G3P input, and the final product, pyruvate
- Irreversible, exergonic
41
Pyruvate kinase control
- Tightly controlled
- Allosteric control
- Covalent modification
42
Pyruvate kinase deficiency (2nd most common)
- Non-spherocytic hemolytic anemia
| - If mutated, RBC cannot metabolize sugar, but protected against malaria
43
Pyruvate under anaerobic conditions
- Converted to lactate
| - NADH produced cannot be reoxidized by O2
44
Lactate dehydrogenase (under anaerobic conditions) regenerates
- NAD+ as pyruvate > reduced
| - Allows glycolysis to continue (NAD+ used by G3PDh)
45
Pyruvate under aerobic conditions produces
- NADH that can enter the ETC
| - Regenerates NAD+
46
Major difference of aerobic vs. anaerobic conditions
- The amount of ATP formed
- 2.5 under aerobic conditions
- No ATP in anaerobic conditions
47
Lactic acid production from anaerobic glycolysis causes
- Generation of H+
48
Substrate level phosphorylation in payoff phase produces
- 4 ATP overall
- 2 ATPs from 3-phosphoglycerate kinase
- 2 ATPs from Pyruvate kinase
- Net = 2 ATPs (4 produced, 2 used for priming)
49
Oxidative phosphorylation produces
- Glyceraldehyde-3-phosphate DH (2 NADHs/glucose)
- Each NADH --> 2.5 ATPs
- Total of 5 ATPs and glucose
50
Glycolysis total energy production
- 7 ATPs
| - Glucose
51
Other sugars that can be metabolized in glycolysis
- Galactose
- Fructose
- Mannose
52
Galactose is phosphorylated by
- Galactokinase in the hepatocyte
53
Hexokinase in muscle phosphorylates
- Fructose in muscle cells
| - Directly enters glycolysis via G3P
54
Fructose in liver in phosphorylated by
- Fructokinase in liver
| - Enters glycolysis through longer pathway via G3P at end
55
Glycolytic enzyme deficiencies primarily effect
- Primarily effect RBC's
56
Hemolytic anemia typically caused by deficiency in these glyolytic enzymes
- PFK-1
- Phosphoglucose isomerase
- Triose phosphate isomerase
- Phosphoglycerate kinase
57
Tauri Disease
- Caused by Phosphofructokinase-1 deficiency in muscle cells
58
Non-spherocytic anemia
- Caused by deficiency of the pyruvate kinase enzyme in erythrocytes
59
Hereditary fructose intolerance
- Result of a deficiency in the hepatic aldolase-B enzyme
60
alpha-D-galactose-1-phosphate uridyltransferase enzyme results in
- Galactosemia when UDP-glucose is absent
61
- Epimerization of galactose by galactose 1-P uridyl transferase produces
- Glucose-1-Phosphate
62
- Phosphoglucomutase produces
- Glucose-6-phosphate
63
- Phosphoglycerate kinase reverse reaction
- Transfer of a phosphate group from an ATP to another molecule
64
Pyruvate kinase at the end of glycolytic pathway
- MAJOR regulatory branch point in the overall pathway
