Lecture 11. Glycolysis Flashcards
Where would you find the glucose transporter GLUT3 and what is an important feature ?
- Brain
- Low Km allows relatively constant rate of glucose uptake independent of extracellular concentration over the normal range
What are 8 factors that effect the control of the glycolytic flux ?
- Enzyme abundance
- Enzyme kinetics
- Thermodynamic favorability
- Covalent modification eg. phosphorylation of pyruvate kinase
- Compartmentalisation eg. cytosol verses mitochondria
- Redox state eg. NAD+ /NADH2
- Physiological situation eg. starvation or adrenalin
- Isoenzyme eg. glucokinase
What happens when there is hypoxia ?
- HIF -1 activated
- Metabolic adaptation (increase in glycolytic enzymes)
- Blood vessel growth
Where is the hypoxia inducible factor highly expressed ?
Tumours
What is hypoxia inducible factor ?
A transcription factor that is turned on when there is no oxygen
What effect does alanine have on enzymes ?
Makes them less active
What are the energy requirements in the glycolytic pathway ?
- ATP production
- ATP consumption
- NADH2 prouction
What is NADPH2 associated with ?
Anabolism
What does the enzyme pyruvate kinase do ?
- Covalent modification
- Product inhibition
- Allosteric modulation
- Abundance sensitive to insulin/glucagon ratio and hypoxia inducible factor
What is phosphofructokinase sensitive to ?
- ATP
- Fructose-2,6-biphosphate
- Citrate
Abundance sensitive to insulin/glucagon ratio and hypoxia inducible factor
What is an allosteric enzyme ?
Has sites on enzymes other than active site which allow enzyme to modulate function
What type of enzyme is phosphofructokinase ?
An allosteric enzyme
Why is phosphofructokinase a controlling step in flux down pathway ?
Its sensitive to environment and the metabolites its in. Its irreversible
Why is hexokinase a controlling step in the flux down pathway ?
Has a low Vmax
What type of ring does Fructose 6-phosphate have ?
Furano ring of fructose
What type of ring does Glucose 6-phosphate have ?
Pyran ring of glucose
What does glucokinase respond to ?
The ratio of insulin/glucagon and the hypoxia inducible factor
Where is glucokinase found ?
Liver
What enzyme is insensitive to Glucose-6-phosphate ?
Glucokinase
What are the three key enzymes involved in the glycolytic pathway ?
- Hexokinase
- Phosphofructokinase
- Pyruvate kinase
What does glycolysis convert pryuvate to under anaerobic conditions ?
lactate
What do red blood cells convert pyruvate to ?
Lactate
Why can red blood cells only perform glycolysis ?
They have no mitochondria
What is the end products of glycolysis ?
Two pyruvate molecules
Where does glycolysis occur ?
Cytoplasm
How does Glut 4 transporter work ?
Insulin recruits vesicles containing Glut 4 and causes them to be translocated to the cell surface where Glut 4 functions as a pore for glucose entry
What type of transport moves glucose to the blood by Glut 2
Passive transport
What drives glucose uptake ?
Sodium gradient
Where would you find the glucose transporter SGLT1 and what is an important feature ?
- Duodenum, jejunum, renal tubules
2. The sodium glucose co-transporter of the small intestine
Where would you find the glucose transporter GLUT5 and what is an important feature ?
- Jejunum
2. Probably responsible for fructose uptake from the intestine
Where would you find the glucose transporter GLUT4 and what is an important feature ?
- Muscle, adipose tissue
2. The insulin sensitive glucose transporter
Where would you find the glucose transporter GLUT2 and what is an important feature ?
- Liver, kidney, intestine, pancreatic B-cell
2. High Km allows glucose to equilibrate across
Where would you find the glucose transporter GLUT1 ?
Erythrocytes, fetal tissue, placenta, brain
Why cant cellulose be broken down easily ?
The angle of the bonds makes it difficult
How does glucose form rings ?
Reacts with itself
