Biochemistry Part 5 Flashcards
What is our primary energy source?
Oxidised to CO2 and H20
Which cell types require glucose?
Erythrocytes Retina Renal Medulla Brain All cancer cells
Name some dissacharides
Lactose
Maltose
Sucrose
Cellobiose
Name some polysaccharides
Cellulose
Glycogen
What are the fates of glucose?
Storage
- glycogen, starch, sucrose
- conversion to lipids
Oxidation through the pentose phosphate pathway
Fermentation by anaerobic glycolysis
Oxidation through aerobic glycolysis
What is the outcome of the pentose phosphate pathway?
Formation of ribose-5-phosphate
What is the outcome of oxidation though anaerobic glycolysis?
Formation or Pyruvate
What is the outcome of fermentation by anaerobic glycolysis?
Formation of lactate
What is ribose-5-phostphate?
Precursor for nucleotide synthesis and DNA repair
Essential for growth
What is Lactate?
Rapid, inefficient ATP production
What is pyruvate?
Efficient ATP production by oxidative metabolism
How is glucose transported into cells?
Via Na+/glucose symporters
Via passive facilitated diffusion glucose transporters
Where is GLUT 1 found?
Brain
Low Km
Where is GLUT 2 found?
Liver B cells
High Km, insulin dependant
Where is GLUT 3 found?
Brain
Low Km
Where is GLUT 4 found?
Muscle
Adipose tissue
Insulin-dependant
Where is GLUT 5 found?
Gut
Fructose transport
Describe the action of GLUT 1?
Binding of glucose to the outside triggers a conformational change
Binding site faces inwards
Glucose can be released in the inside
Conformational change regenerates the binding site on the outside
What is the overall reaction for glycolysis?
Glucose + 2ADP + 2 Pi + 2NAD+
=
2 pyruvate + 4ATP + 2 H2O + 2NADH + 2H+
How many ATP is used in the conversion of Glucose to fructose-1,6-bisphosphate?
2
How many ATP are generated in the conversion of 2 triode phosphates to 2 pyruvates?
4
2 NAD+ are degraded to 2NADH and 2H+
Describe glycolysis stage 1?
Glucose is trapped and destabilised
Describe glycolysis stage 2?
Two interconvertible three-carbon molecules are formed
Describe glycolysis stage 3?
Generation of ATP
What are the 3 control points in glycolysis?
- Hexokinase- substrate entry
- Phosphofructokinase- rate of flow
- Pyruvate kinase- product exit
What are the activators of phosphofructokinase?
AMP
Fructose 2,6 bisphosphate
What are the inhibitors of PFK?
ATP
(will slow glycolysis if energy abundant)
Citrate
(TCA cycle intermediate. Slows downstream energy of pyruvate into TCA cycle if energy abundant)
H+
(slows glycolysis if too much lactic acid is being produced)
What is the energy charge?
The ATP/AMP ratio
When is the cell fully charged and discharged?
Fully charged= all adenylate nucleotides are in the shape of ATP
Discharged= if the cell only contains AMP and Pi
Why is AMP and not ADP the positive regulator?
If ATP is rapidly used up then adenylate kinase can salvage some of the energy in ADP
(2ADP = ATP + AMP)
What is the fate of pyruvate?
Carbon to fuel TCA cycle in mitochondria
What is the fate of electrons?
Electron transport chain and ATP synthesis
What happens if mitochondrial metabolism is inhibited by lack of O2?
NADH is used to ferment pyruvate into lactic acid
NADH is re-generated at beginning of stage 3
What is the warburg effect?
Cancer cells produce energy by high rate of glucose metabolism to lactate (anaerobic glycolysis)
-cancer cells have low Km Hexokinase
What are the advantaged of the warburg effect?
> Rapid energy production
>Supports other pathways for nucleotide synthesis (needed for growth)
> Supports rapid cell growth (proliferation)
What are the disadvantages of the warburg effect?
> Produces H+ and lactate as end products
> Very inefficient ATP synthesis
> High glucose consumption demand
> Cancer patients lose weight
What could be used to treat cancer by targeting glycolysis?
2-deoxyglucose
2-Bromopyruvate
Dichloroacetate
