2.1 - Energy Storage Flashcards
Where is glycogen stored?
In granules in liver and skeletal. Muscle. The large size of the molecule means that many glucose molecules can be stored with minimal osmotic effect.
What are the typical energy stores in a 70kg man?
Triacylglycerols = 15 kg
Glycogen = 0.4 kg
Muscle protein = 6 kg .
Describe the pathway of glycogenesis.
1) glucose + ATP = glucose 6-p + ADP
- Catalysed by hexokinase (glucokinase)
2) glucose 6-p glucose 1-p
- catalysed by phosphoglucomutase
3) glucose 1-p + UTP + h20 -> UDP-glucose + 2Pi
NB: UDP glucose = a highly activated form of glucose
4) glycogen + UDP glucose —> glycogen + UDP
Describe the process of glycogenolysis.
1) glycogen + Pi —> glucose-1-phosphate + glycogen
Done by glycogen phosphorylase.
2) glucose 1 phosphate glucose 6 phosphate
Catalysed by phosphoglucomutase
3) IN THE LIVER BUT NOT MUSCLE
Glucose 6 phosphate + h20 -> glucose + Pi
What are the major features of a glycogen storage disease?
- increased or decreased amounts of glycogen which may cause
1) tissue damage if excessive storage
2) fasting hypoglycaemia
3) poor exercise tolerance - glycogen structure may be abnormal
- usually liver and or muscle are affected
How long is the glucose stored as liver glycogen sufficient for after eating?
8-10 hours. After, run out so gotta do gluconeogenesis which mainly occurs in the liver
What could be used for gluconeogenesis?
- pyruvate, lactate and glycerol
- essential and non essential amino acids
What is the process of gluconeogenesis from pyruvate?
Involves some of the steps from glycolysis.
Overall
2 pyruvate + 4 atp + 2gtp + 2nadh —> glucose + 2NAD + 4adp + 2gdp +6Pi + 2H+
Intermediates you get are amino acids that can be used to make the glucose.
How is gluconeogenesis regulated?
Under hormonal control
Main control sites are
- PEPCK
- Fructose 1-6 bisphosphatase
(activity increased by glucagon and cortisol, decreased by insulin)
How are triglycerides an efficient energy storage molecule in adipose tissue?
Can be stored in a bulk anhydrous form
How are fatty acids synthesised?
From acetyl coA using ATP (from oxidative phosphorylation) and NADPH (from the pentose phosphate pathway)
Steps are carried out by fatty acid synthase complex enzyme.
What enzymes controls The rate of fatty acid synthesis and how is it regulated?
Acetyl coA carboxylase. Regulated allosterically (citrate activates and AMP inhibits) and covalent modification of protein structure (phosphorylation/dephosphorylation).
Insulin activates enzyme (promotes dephosphrylation) , glucagon (and adrenaline inhibit (promote phosphorylation)
Give 4 differences between fatty acid oxidation and fatty acid synthesis.
- oxidation removes C2, synthesis adds C2
- oxidation produces acetyl CoA, synthesis consumes it
- insulin inhibits oxidation, insulin stimulates synthesis
- glucagon and adrenaline stimulate oxidation, where’s they inhibit synthesis
