Chapter 9: Glycolysis Flashcards
What is metabolism?
The collective biochemical reactions in a living organism that converts chemical energy into work.
- Catabolic and anabolic pathways
What is a catabolic pathway?
A process leading to the degradation of macro molecules and nutrients to capture chemical energy
What is an anabolic pathway?
A process which uses energy available from ATP hydrolysis and oxidation of reducing equivalents to synthesize biomolecules
What is metabolic flux?
- The rate at which substrates and products are interconverted
- Determined by two factors
- Level of enzyme activity
- Bioavailability of substrate
What are 4 major biomolecules?
- Proteins
- Nucleic Acids
- Carbohydrates
- Lipids
What is the free energy equation under equilibrium?
How do unfavorable reactions occur
They may be coupled to make them more favorable
What determines if a reaction proceeds or reverses?
Concentration(ratio of product to substrate)
- Exception if ΔG° is very negative/positive (25kJ/mol)
Find the ΔG
What is a monosaccharide
A sugar containing an aldehyde or ketone
What are aldoses?
Aldehyde containing sugars (11)
- Glucose
What are ketoses?
Ketone containing sugars(11)
- Fructose
Describe the structure of a simple sugar.
- Linear
- Cyclic
- Not planar
- Chair or boat conformation
Where is the C=O in Aldose? what about Ketose?
- First position in aldose
- Second position in ketose
What are trioses, tetroses, pentoses, hexoses, and heptoses
- Triose (3c)
- important metabolite and smallest carbs
- Tetroses (4c)
- Pentoses (5c) DNA, RNA
- Hexoses (6c) most common carb
-Heptoses (7c)
What relation do D and L sugars have to eachother
They are enantiomers
- D is -OH on right and L is -OH on left
How is D or L determined in carbs
Assignment is based on furthest chiral carbon from C=O
What are epimers?
When two monosaccharides differ by the position of one -OH group
How does an aldehyde become a hemiacetal?
Alcohol + R group
How does a ketone become a hemiketal?
Alcohol + R group
What does glucose become when it undergoes an intramolecular reaction?
Pyranose: 6 member ring (5C 1O)
What does fructose become when it undergoes an intramolecular reaction?
Furanose: 5 member ring
What is the glucose concentration in blood?
5mM or 90 mg/dL
- Diabetes if resting glucose levels are >7.2mM or >126 mg/100 mL
What hormones regulate glucose levels in the blood?
Insulin decreases and glucagon increases
How are simple sugars broken down?
Simple sugars can be oxidized or reduced based on their function groups
- Reducing agent may be Cu2+ and they need a reducing end
What is Benedict’s Test
- Cu2+ is changed into Cu+ coupled to H2O2 in second product to make colored product
- Can be personally monitored by patient
How are two monosaccharides joined together?
- O-glycosidic bond
- Formed through condensation
What are the outcomes of glycolysis?
1 molecule of glucose —> 2 pyruvates
What are three irreversible changes during glycolysis?
- Hexokinase (Glucose -> Glucose 6 P
- Phosphofructokinase 1 (Fructose 6 P -> Fructose 1,6 BP)
- Pyruvate kinase (phosphoenolpyruvate -> pyruvate)
What happens in the first step of glycolysis?
Hexokinase is used to phosphorylate (ATP -> ADP) Glucose which becomes Glucose-6-P
What happens in the second step of glycolysis?
Phosphoglucoisomerase is used to transform Glucose-6-P to Fructose-6-P. The six member ring changes to a five member ring (8)
What happens in the third step of glycolysis?
Phosphofructokinase-1 is used to phosphorylate (ATP -> ADP) Fructose-6-P to Fructose-1,6-BP (9)
What is the fourth step of glycolysis?
Aldolase is used to cleave Hexose into two trioses. The reaction uses Schiff base as an intermediate (10)
What is the fifth step of glycolysis?
Triose phosphate isomerase makes Dihydroxyacetone-P into an enediol intermediate which can be turned to Glyceraldehyde-3-P (14)
What is the sixth step of glycolysis?
Glyceraldehyde-3-phosphate dehydrogenase is used to generate NADH from NAD+ and Pi and turns Glyceraldehyde-3-p to 1,3 bisphosphoglycerate (15)
What is the seventh step of glycolysis?
Phosphoglycerate kinase is used to phosphorylate ADP -> ATP and turns 1,3 Bisphosphoglycerate into 3-phosphoglycerate
What is the eighth step in glycolysis?
Phosphoglycerate mutase causes a phosphoryl shift causing 3-Phosphoglycerate to become 2-Phosphoglycerate
What is the ninth step in glycolysis?
Enolase dehydrates 2-Phosphoglycerate causing it to become Phosphoenolpyruvate
What is the tenth step in glycolysis?
Pyruvate kinase turns Phosphoenolpyruvate into Pyruvate by phosphorylating ADP and turning it to ATP
What is the tenth step in glycolysis?
Pyruvate kinase turns Phosphoenolpyruvate into Pyruvate by phosphorylating ADP and turning it to ATP
What three things can happen to pyruvate after it is synthesized?
Aerobic conditions:
- ATP produced via citrate cycle and ETC
Anaerobic conditions:
- Production of lactate
- Ethanol production
How can 1,3 Bisphosphoglycerate become 2,3 Bishphosphoglycerate?
- 2,3 Bisphosphoglycerate is an inhibitor of Hemoglobin
- Bisphosphoglycerate mutase
What does the direction of metabolic flux depend on?
- Metabolite concentration
- Controlled by allosteric enzymes in irreversible reactions
What does glucokinase in the liver do?
- Traps extra glucose that can make glycogen for later use
- Acts as glucose sensor to stimulate insulin release in Pancreatic beta cells
What is the difference in PFK-1 in its active vs inactive form?
R-state (active):
- AMP or ADP bound
- Increased affinity for F6P
T-state (inactive):
- ATP is bound
- Decreased F6P affinity
Why is NAD+ regenerated and where does it occur?
- NAD+ regeneration is required to maintain flux through GAPDH
- Regenerated in cytoplasm
