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Gastrointestinal Block > GI Biochemistry > Flashcards

GI Biochemistry Flashcards

(73 cards)

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1
Q

glycogen is a _____ consisting of ____ molecules

A

polymer

glucose

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2
Q

glycogen is the main storage form of glucose in which cells? (2)

A

liver

muscle

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3
Q

when is liver glycogen broken down?

A

between meals to release glucose into the blood

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4
Q

is liver or muscle glycogen responsible for maintaining homeostatic levels of blood glucose?

A

liver glycogen

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5
Q

when is muscle glycogen broken down?

A

to provide energy for muscles via glycolysis and the TCA cycle

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6
Q

what is glycogenesis?

A

the synthesis of glycogen from glucose

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7
Q

[GLYCOGENESIS] where does glycogenesis take place? (2)

A

liver

skeletal muscle

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8
Q

[GLYCOGENESIS] what is needed for glucose to be added to existing glycogen?

A

a primer which is covalently attached to glycogenin (a protein)

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9
Q

[GLYCOGENESIS] what catalyses the phosphorlyation of glucose to glucose-6-phosphate?

A

hexokinase

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10
Q

[GLYCOGENESIS] what converts glucose-6-phosphate into glucose-1-phosphate?

A

phosphoglucomutase

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11
Q

[GLYCOGENESIS] what converts glucose-1-phosphate to UDP-glucose?

A

UDP-glucose pyrophorylase

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12
Q

[GLYCOGENESIS] what adds UDP-glucose to glycogen?

A

glycogen synthase

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13
Q

[GLYCOGENESIS] glucose synthase:

adds ___ glucose molecule to glycogen at a time

A

one

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14
Q

[GLYCOGENESIS] can glucose synthase start new glucose molecules? (true/false)

A

false it can only extend existing glycogen molecules

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15
Q

[GLYCOGENESIS] glucose synthase cannot introduce branches into glycogen? (true/false)

A

true

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16
Q

[GLYCOGENESIS] glycogen synthase is the rate-limiting enzyme of glycogenesis? (true/false)

A

true

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17
Q

[GLYCOGENESIS] what enzyme introduces branches into glycogen?

A

transglycosylase

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18
Q

what is glycogenolysis?

A

breakdown of glycogen to form glucose

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19
Q

[GLYCOGENOLYSIS] generally, what happens in the process of glycogenolysis?

A

1 glucose molecule is cleaved off the ends of the glycogen at a time

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20
Q

[GLYCOGENOLYSIS] what is the rate limiting step of glycogenolysis?

A

glycogen + phosphate converting into glucose-1-phosphate+glycogen

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21
Q

[GLYCOGENOLYSIS] what converts glycogen + phosphate into glucose-1-phosphate+glycogen?

A

glycogen phosphorylase

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22
Q

[GLYCOGENOLYSIS] what converts glucose-1-phosphate into glucose-6-phosphate?

A

phosphoglucomutase

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23
Q

[GLYCOGENOLYSIS] what converts glucose-6-phosphate into glucose?

A

glucose-6-phosphatase

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24
Q

[GLYCOGENOLYSIS] in skeletal muscle why can’t glucose-6-phosphate be dephosphorylated into glucose?

A

glucose-6-phosphatase is a hepatic enzyme and is not present in skeletal muscle

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25
[GLYCOGENOLYSIS] what is the fate of glucose-6-phosphate in skeletal muscle?
used in glycolysis and the TCA cycle to generate energy
26
what is gluconeogenesis?
the synthesis of glucose within the body from non-carbohydrate substrates
27
[GLUCONEOGENESIS] when is gluconeogenesis important?
during periods of fasting
28
[GLUCONEOGENESIS] why is gluconeogensis energetically expensive?
ATP is needed to drive unfavourable reactions
29
[GLUCONEOGENESIS] where does gluconeogensis take place? (2)
majority takes place in the liver | some takes place in the kidneys
30
[GLUCONEOGENESIS] how many irreversible reactions are present in glycolysis?
3
31
[GLUCONEOGENESIS] why is gluconeogenesis not the reverse of glycolysis
because not all the reactions in glycolysis are reversible
32
[GLUCONEOGENESIS] how are the 3 irreversible reactions of glycolysis reversed in gluconeogenesis?
by specific enzymes
33
[GLUCONEOGENESIS] what is the enzyme pyruvate carboxylase responsible for?
converts pyruvate into oxaloacetate
34
[GLUCONEOGENESIS] what is the enzyme PEP carboxykinase responsible for?
converts pyruvate into phosphoenol pyruvate (PEP)
35
[GLUCONEOGENESIS] what is the enzyme fructose 1,6 -bisphosphatase responsible for?
converts fructose1,6-bisphosphate into fructose-6-phosphate
36
[GLUCONEOGENESIS] what is the enzyme glucose-6-phosphatase responsible for?
converts glucose-6-phosphate into glucose
37
[GLUCONEOGENESIS] name the 4 gluconeogenic enzymes
Pyruvate carboxylase PEP carboxylase Fructose -1,6 -bisphosphatase Glucose-6-phosphatase
38
[GLUCONEOGENESIS] name some of the precursors used in gluconeogenesis (4)
pyruvate lactate (from skeletal muscle) amino acids (from protein) glycerol (from adipose tissue)
39
[GLUCONEOGENESIS] how is lactate converted into glucose? (3 steps)
- blood transports lactate to the liver - liver converts lactate into pyruvate in the cori cycle - pyruvate is then used to generate glucose
40
[GLUCONEOGENESIS] how are amino acids converted into glucose? (4 steps)
- amino acids are degraded into TCA cycle intermediates - converted into oxacloacetate - converted into pyruvate - pyruvate is used to generate glucose
41
in glycolysis what effects do glucagon and insulin have on phosphofructokinase?
glucagon inhibits | insulin stimulates
42
in gluconeogenesis what effects do glucagon and insulin have on fructose-1,6-bisphosphatase?
insulin inhibits | glucagon stimulates
43
in glycogenesis what effects do glucagon and insulin have on glycogen synthase?
glucagon inhibits | insulin stimulates
44
in glycogenolysis what enzymes stimulate glycogen phosphorylase and what enzyme inhibits?
insulin inhibits | glucagon, adrenaline and cortisol stimulate
45
High AMP and ADP stimulate ____ and inhibit ____
glycolysis | gluconeogenesis
46
high ATP inhibits ____
glycolysis
47
fructose 2,6-bisphosphate is __ in fed state and __ in starved state
high (stimulates glycolysis and inhibits gluconeogenesis) | low (stimulates gluconeogenesis and inhibits glycolysis)
48
where is fat stored?
adipose tissue
49
fats are a subgroup of ____ called _____
lipid | triglyceridesd
50
what are the uses of fat? (3)
energy store gain essential fatty acids metabolism of fat-soluble vitamins
51
what makes up triglycerides?
glycerol | 3 fatty acids
52
what variation between fatty acids can effect their function within the body?
melting point
53
what are the products of fat (triglyceride) digestion that need to be absorbed? (3)
glycerol fatty acids monoglycerides
54
which product of fat digestion is readily absorbed in intestinal epithelial cells?
glycerol
55
what kind of fatty acids enter portal blood and go to the liver?
short and medium length fatty acids
56
what is re-synthesised into triglycerides?
monoglycerides | fatty acids
57
in the enterocytes what are the triglycerides packaged into?
chlyomicrons
58
where does the chylomicron take the triglycerides?
lymph then blood stream then muscle and adipose tissue
59
how are the fatty acids released from the triglycerides in the muscle and adipose tissue?
lipoprotein lipase
60
how do fatty acids generate energy?
they are oxidised
61
what does the fatty acid have to be converted to in order to be activated?
acyl-CoA
62
__ ATP are used to convert fatty acids into acyl-CoA
2
63
how is acyl-CoA transported into the mitochondria for further oxidation?
carnitine shuttle
64
what compounds are involved in the carnitine shuttle?
acyl carnitine | carnitine
65
where does beta oxidation of fatty acids take place?
mitochondrial matrix
66
what is produced in beta oxidation and how are they used?
1 acetyl-CoA (used in the TCA cycle) 1 FADH2 (used in oxidative phosphorlyation) 1 NADH + H+ (used in oxidative phosphorlyation) 1 fatty acyl-CoA shortened by 2 carbons
67
why is acyl-CoA shortened by 2 carbons in beta oxidation?
acetyl-CoA (which has 2 carbons) has been removed from it
68
glycerol is broken down into glycerol-3-phosphate by _______ _______
glycerol kinase (which is found in the liver and kidneys)
69
glycerol-3-phosphate is further broken down into _________ ________
dihydroxyacetone phosphate (which is a normal intermediate for carbohydrate metabolism
70
ketone bodies are formed in the ______ mitochondria from _____ produced from beta oxidation
liver | acetyl-CoA
71
ketone bodies are important for energy production in the ____ _____ and the ____ ____ where they are converted back into acetyl-CoA
heart muscle | renal cortex
72
what is ketosis?
raised levels of ketone bodies in the blood
73
in what conditions are ketone bodies produced by the liver? (3)
starvation alcoholism diabetes

Gastrointestinal Block (8 decks)

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