Final: Chapter 9 Glycolysis Flashcards
What does flux refer to?
The rate that substrates and products (metabolites) are interconverted
What two primary factors determine flux?
Level of enzyme activity and bioavailability of substrates
When might reactions be coupled?
When the overall Gibbs free energy is unfavorable/nonspontaneous (positive)
What is the structure of a monosaccharide?
One sugar containing an aldehyde (aldoses) or a ketone (ketoses)
What are epimers?
Two monosaccharides that differ in the -OH position around one chiral carbon
Simple sugars go through an intramolecular reaction to form what two types of rings?
Pyranose or furanose rings which increase structural stability
What determines whether a simple sugar is oxidized or reduced?
Their functional groups
What are reducing sugars?
Carbohydrates that react with oxidizing agents to promote oxidation
What are disaccharides?
Two monosaccharides linked together through an O-glycosidic bond
What type of reaction forms disaccharides?
Condensation reaction
What are the three most common disaccharides?
Lactose, sucrose, and trehalose
What’s one reason why shared intermediates are used effectively in coupled reactions?
Some metabolic enzymes are components of large multiprotein complexes. This is a type of close physical interaction that limits product diffusion and functions to “channel” shared intermediates from one enzyme to the next
What are nonreducing sugars?
Sugars that cannot reduce Cu2+. Examples include sucrose and trehalose
What is lactase?
A hydrolytic enzyme that is expressed in high levels in infants to aid in the digestion of lactose. Levels of lactase decline in adults
Under what conditions does glycolysis generate ATP?
Anaerobic conditions
In general, what is glycolysis?
The “splitting” of 1 molecule of glucose into 2 molecules of pyruvate
How many enzymatic reaction comprise glycolysis?
10 reactions
(1-5) ATP investment
(6-10) ATP production
What is the first step of glycolysis and what enzyme is involved?
- Glucose is phosphorylated by hexokinase or glucokinase to form glucose-6-P
- Mg2+ required
- ATP converted to ADP (ATP hydrolysis)
- Hexokinase is for all cells (broad range of substrate specificities), glucokinase (specific for glucose in the liver and pancreas)
What enzyme is used for glucose monitoring?
Glucokinase
What is the second step of glycolysis and what enzyme is involved?
Glucose-6-P undergoes isomerization using phosphoglucoisomerase to form fructose-6-P
What is the third step of glycolysis and what enzyme is involved?
- Fructose-6-P is phosphorylated by phosphofructokinase-1 to form fructose-1,6-BP
- ATP hydrolysis
- This is the rate-limiting step!
What is the fourth step of glycolysis and what enzyme is involved?
- Fructose-1,6-BP is cleaved with aldolase to form dihydroxyacetone-P
- Uses Schiff base as an intermediate
What is the fifth step of glycolysis and what enzyme is involved?
DHAP (dihydroxyacetone-P) undergoes isomerization using triose phosphate isomerase to form glyceraldehyde-3-P . This is the end of the ATP investment stage.
What is the sixth step of glycolysis and what enzyme is involved?
- Glyceraldehyde-3-P uses glyceraldehyde-3-P dehydrogenase (GAPDH) to transfer a phosphoryl group to it and form 1,3-biphosphoglycerate
- Produces 2 NADH
What is the seventh step of glycolysis and what enzyme is involved?
- Phosphoglycerate kinase phosphorylates (substrate-level phosphorylation) 1,3-biphosphoglycerate to form 3-phosphoglycerate
- 2 ATP produced
What is the eight step of glycolysis and what enzyme is involved?
Phosphoglyceromutase is used which causes a phosphoryl shift in 3-phosphoglycerate to form 2-phosphoglycerate
What is the ninth step of glycolysis and what enzyme is involved?
Enolase dehydrates 2-phosphoglycerate to form phosphoenolpyruvate
What is the tenth step of glycolysis and what enzyme is involved?
- Pyruvate kinase phosphorylates (substrate-level phosphorylation) phosphoenolpyruvate to form pyruvate
- Produces 2 ATP
How is phosphofructosekinase-1 regulated?
- AMP and ADP indicate low energy charge in the cell, ATP indicates high energy charge of the cell (if there is high ATP levels, then glycolysis is not needed)
- Citrate inhibits this enzyme when there is high levels of citrate (indicates that glycolysis is not needed right now to produce pyruvate)
What is the relationship between glucose levels and production of insulin?
When glucose levels are high, insulin is released
What are the three ways pyruvate is metabolized depending on availability of oxygen?
Aerobic conditions: ATP production (Citrate Cycle and ETC)
Anaerobic conditions: Production of lactate and ethanol production
Why is NAD+ regenerated and where is it regenerated?
- NAD+ is required to maintain flux through GAPDH (enzyme in the step of glycolysis that produces 2 NADH)
- Regenerated in the cytoplasm
Why are NAD+ levels inadequate in someone who has lactate dehydrogenase deficiency?
Lactate dehydrogenase is an enzyme that converts pyruvate to lactate and also converts NADH to NAD+. If this enzyme is deficient, the enzyme is not functional and therefore, lower levels of NAD+
An example of an anabolic pathway is _____________.
A) smaller amino acids being linked together to make a protein
B) the tendency to gain or lose weight
C) the burning of fat by exercise
D) a protein being broken down into smaller amino acids
E) none of the above
A) smaller amino acids being linked together to make a protein
*anabolic is building :)))
Tarui’s disease is a disorder in which
phosphofructosekinase-1 deficiency occurs.
Which of the following would most likely be
observed in patients with this disorder?
A) Fructose-6-P levels increase.
B) Fructose-1,6-P levels decrease.
C) ATP levels increase.
D) A and B
E) A and C
A and B
