12.Glycolysis Flashcards
What is glycolysis?
the first step in the breakdown of glucose to extract energy for cellular metabolism
What are the two polymers of glucose?
starch and cellulose
Glucose
- the most important carbohydrate
- primary energy source
- oxidised to GOCOWE - glucose and oxygen to carbon dioxide, water and energy
- cells like erythrocytes, retina, Renal medulla use glucose as their only source of energy
- required for function of the brain
Glycolysis reaction
C6H1206 +O2 → CO2 + H2O + energy
State the two forms of glucose
straight chain and intermediate
What is the difference between alpha-glucose and b-glucose?
alpha- glucose - OH on aldehyde group points down
beta- glucose - OH on aldehyde group points up
What are the 3 stages of metabolism?
- Glycolysis
- Citric acid cycle
- Electron transfer chain
How can glucose be transported in the cell?
- via Na+/glucose symporters in the gut.
2. passive-facilitated diffusion through glucose transporters.
GLUT 1 tissue/characteristics
- brain
- low Km
GLUT 2 tissue/characteristics
- liver/pancreatic B cells
- high Km/ insulin independent
GLUT 3 tissue/characteristics
- brain
- low Km
GLUT 4 tissue/characteristics
- muscle/adipose tissue
- insulin dependent
GLUT 5 tissue/characteristics
- gut
- fructose transport
Describe the action of GLUT 1
- binding of glucose to the outside triggers a conformational change so that the binding site faces inwards
- glucose can be released in the cell
- conformational change regenerates binding site on the outside
Glycolysis reaction (glucose to pyruvate)
Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 Pyruvate + 2 ATP + 2 H20 + 2 NADH and 2 H+
Stages of Glycolysis
- Energy investing - glucose is trapped and destabilised
- Two 3 carbon molecules are formed
- Generation of ATP
What type of linkage is formed from the reaction between a-glucose and fructose? What product is formed and what is removed?
- a-1,2-glycosidic linkage (sucrose)
- water
What type of linkage is formed from the reaction between a-glucose and b-glucose? What product is formed and what is removed?
- a-1,4-glycosidic linkage (maltose)
- water
What type of linkage is formed from the reaction between b-glucose and b-glucose? What product is formed and what is removed
- b-1,4-glycosidic linkage (cellobiose)
What are the two main cellular requirements in Glycolysis?
- production of ATP
- provision of building blocks for synthetic reactions
What acts as control points In Glycolysis?
enzymes
Hexokinase
Glucose + ATP → Glucose-6-phosphate + ADP + H+
ΔG°= -33.5 KJ mol-1
Phosphofructokinase
Fructose-6-phosphate + ATP → Fructose-1,6- diphosphate + ADP +H+
ΔG°= -22.2 KJ mol-1
Pyruvate kinase
Phosphoenolpyruvate + ADP + H+ → Pyruvate and ATP
ΔG°= -16.7 KJ mol-1