MEH - Energy Storage (Glycogen And Fat) Flashcards Preview

CJ: UoL Medicine Semester Two (ESA2) > MEH - Energy Storage (Glycogen And Fat) > Flashcards

Flashcards in MEH - Energy Storage (Glycogen And Fat) Deck (33):
1

Which tissues/cells have an absolute requirement for glucose?

- red blood cells
- neutrophils
- innermost cells of kidney medulla
- lens of the eye

2

At what level should blood glucose be maintained?

Roughly 5 mmol/L

3

What happens when blood glucose falls below 2.8 mmol/L?

Confusion

4

What happens when blood glucose falls below 1.7 mmol/L?

Weakness, nausea

5

What happens when blood glucose falls below 1.1 mmol/L?

Muscle cramps

6

What happens when blood glucose falls below 0.6 mmol/L?

Brain damage, death

7

Where is glycogen stored in the body?

In muscles (to supply muscle) and in liver (to replenish plasma glucose conc.)

8

How does glycogen appear on imaging?

Small black granules

9

How is glycogen structured?

Glucose residues linked by alpha 1-4 glycosidic bonds (joining chains) and alpha 1.6 glycosidic bonds (forming branch points every 8-10 residues), surrounding a central protein called glycogenin

10

How is glycogen synthesised?

- glucose and ATP concreted to G6P and ADP by hexokinase
- G6P converted to G1P by phosphoglucomutase
- G1P converted to UDP-glucose by G1P uridylyltransferase
- UDP glucose converted to glycogen by glycogen synthase/branching enzyme

11

How is glycogen degraded?

Glycogen phosphorylase and phosphoglucomutase break down glycogen into G6P, so it can be used in glycolysis or be released by the liver into the blood.

12

What happens to glycogen stores in the liver?

G6P converted to glucose and exported to blood. Liver glycogen in a buffer of blood glucose levels.

13

What happens to glycogen stores in the muscle?

Muscle lacks the enzyme glucose-6-phosphatase. G6P enters glycolysis for energy production

14

What is the rate limiting enzyme of glycogen synthesis?

Glycogen synthase

15

What is the rate limiting enzyme of glycogen degradation?

Glycogen phosphorylase

16

What effect does glucagon have on muscle glycogen stores?

None

17

What effect does AMP have on muscle glycogen phosphorylase?

It is an allosteric activator, but does not work on liver form of enzyme

18

What are glycogen storage diseases?

Inborn errors of metabolism - inherited. They arise from deficiency/dysfunction of enzymes of glycogen metabolism. There are 11 types. Liver and/or muscle can be affected.

19

What are the consequences of incorrect levels of glycogen storage?

Excess glycogen storage can lead to tissue damage, diminished glycogen storage can lead to hypoglycaemia and poor exercise tolerance

20

What is deficient in von Gierke's disease?

Glucose-6-phosphatase

21

What is deficient in McArdle disease?

Muscle glycogen phosphorylase deficiency

22

Where does gluconeogenesis occur?

In liver and in kidney cortex

23

What are the main precursors of gluconeogenesis?

- Lactate (from anaerobic glycolysis in exercising muscle)
- glycerol (released from adipose tissue due to breakdown of triglycerides)
- amino acids (mainly alanine)

24

What are the three key enzymes involved with gluconeogenesis?

1) PEPCK
2) fructose 1,6-bisphosphatase
3) glucose-6-phosphatase

25

What effect does glucagon/cortisol have on gluconeogenesis?

- increases amount of PEPCK and fructose-1,6-bisphosphatase
- stimulates gluconeogenesis

26

What effect does insulin have on gluconeogenesis?

- decreases amount of PEPCK and fructose-1,6-bisphosphatase
- inhibits gluconeogenesis

27

At what point after eating does gluconeogenesis occur?

After a fast of 8-10 hours onwards

28

How is excess energy stored in the body?

As triacylglycerol in adipose tissue

29

True or false - adipocytes are a constant/unchanging size?

False - they expand as more fat is added. Can increase in size by about four times on weight gain before dividing and increasing total number of fat cells.

30

How do triacylglycerides get from intestinal epithelia cells to the blood?

Via the lymph fluid

31

Where does fatty acid synthesis mainly occur?

In the liver

32

How does lipgloss occur?

Hormone sensitive lipase (stimulated by gluconeogenesis/adrenaline, inhibited by insulin) causes break down of triacylglycerol into glycerol and free fatty acids in the blood

33

Outline fatty acid synthesis

- Pyruvate enters mitochondria and forms acetyl-CoA & OAA which then condense to form citrate
- Citrate enters cytoplasm and cleaved back to Acetyl-CoA & OAA
- Acetyl-CoA carboxylase (key regulator) produces
malonyl-CoA from Acetyl-CoA.
- Fatty acid synthase complex builds fatty acids by sequential addition of 2 carbon units provided by malonyl-CoA.

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