Energy Storage - Glycogen And Fat Flashcards
What tissues have an absolute requirement for glucose as an energy source ?
1) red blood cells
2) neutrophils
3) inner most kidney medulla
4) lens of the eye
What is the normal concentration of plasma glucose ?
5mM
Can the brain utilise ketone bodies during extreme periods of stress ?
Yes
When blood plasma levels of glucose drops below 0.6mmol/L what are the consequences ?
Brain damage or death . This is because the blood brain barrier utilises GLUT1 transporter for the transport of glucose. The GLUT1 transporter has a km of 0.6 so if it drops below that level , can no longer transport glucose to the brain
What occurs when the blood glucose levels drops below 2.8mm/L ?
Confusion
What occurs when the blood glucose levels drops below 1.7mm/L ?
Weakness , nausea
What occurs when the blood glucose levels drops below 1.1 mm/L?
Muscle cramps
How is glycogen stored ?
As granules in skeletal muscle and the liver
Roughly how many grams of glycogen is stored in skeletal muscle ?
300 g
Roughly how many grams of g,glycogen is stored in the liver ?
100 g
Describe the structure of glycogen
- polymer consisting of chains of glucose residues
- chains are organised like branches originating from a dimer of the protein glycogenin
- glucose residues are linked by 1,4 and 1,6 glycosidic bonds forming branch points at every 8-10 residues
How is the structure of glycogen related to its function ?
1) branches which allows enzymes to react at many points , this increased the speed at which energy is released.
2) glycogen is insoluble so it does not have no osmotic effect on other cells
3) it is a compact molecule so can store a lot of energy in a small space
Define glycogenesis
Glycogen synthesis from glucose
Does the synthesis of glycogen require energy?
Yes
Outline the steps of glycogenesis
1) glucose is converted into glucose-6-phosphate by hexokinase. This in turn converts ATP into ADP.
2) glucose 6 phosphate is converted into glucose 1-phosphate by phosphoglucomutase.
3) glucose 1 phosphate is then converted into UDP-glucose by G1P uridylytransferase. Glucose -1-phosphate + UDP + H20 = UDP glucose + 2PPi
4) glycogen ( n residues ) is combined with UDP glucose which adds additional glucose residues to the chain. This releases UDP. Glycogen synthase is used to make the 1,4 bonds and branching enzyme is used to make 1,6 bonds
Define glycogenolysis
Pbreakdown of glycogen
Outline the steps of glycogenolysis
1) Gkycogen(n residues) +Pi = glucose 1 phosphate +glycogen (n-1 residues). This is with the aid of glycogen phosphorylase or Debranching enzyme.
2) glucose -1- phosphate is converted into glucose -6-phosphate by phosphoglucomutase.
3) glucose 6-phosphate is then used by muscle for energy production , but released by liver into blood for other tissues.
What occurs to glucose-6 - phosphate in the liver ?
Glucose 6 phosphate is converted back into glucose by glucose -6-phosphatase.
- the glucose is then expected to blood.
What occurs to glucose 6 phosphate in the muscle ?
Glucose 6phpshaye will enter glycolysis in the muscle and produce energy. REMAINS IN THE MUSCLE
What energy store of glycogen is used as a buffer for blood glucose levels ?
Glycogen storage in the liver
How comes the g,Yvonne in muscle is only used for muscle cells and not for other tissues around the body ?
Because muscle does not contain the enzyme glucose -6- phosphatase to convert glucose -6-phosphate into glucose. So it remains trapped in the muscle cells.
Under what regulation is liver glycogen metabolism under?
Hormonal regulation