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Medicine year 1 > Metabolism > Flashcards

Metabolism Flashcards

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1
Q

Glycogenesis

A

synthesis of glycogen from glucose

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2
Q

Glycogenolysis

A

Breakdown of glycogen to form glucose

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3
Q

Gluconeogenesis

A

synthesis of glucose from metabolic precursors

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4
Q

how are glucose monomers attached in a glycogen polymer (2)

A

straight chain: α 1-4 glycosidic links
Branches: α 1-6 glycosidic links

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5
Q

Which protein is a glycogen primer bonded to

A

glycogenin

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6
Q

Which enzyme adds glucose molecules in a straight chain

A

glycogen synthase

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7
Q

What does glycogen synthase use to extend the glycogen chain

A

UDP glucose

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8
Q

What enzyme is used to introduce branches in glycogen molecules

A

transglycosylase

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9
Q

What regulates the activity of glycogen synthase (2)

A

insulin - activates glycogen synthase
Glucagon - inhibits glycogen synthase

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10
Q

What are the two types of glycogen

A

Liver
Muscle

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11
Q

Describe liver glycogen (3)

A

broken down between meals
Used to maintain blood glucose
Released to supply energy to tissues

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12
Q

Describe muscle glycogen (2)

A

not available for blood glucose maintenance
Provides energy via cellular respiration

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13
Q

Which is more likely to occur overnight: glycogenolysis or gluconeogenesis

A

gluconeogenesis as hepatic glycogen is depleted

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14
Q

what enzyme is involved in glycogenolysis

A

glycogen phosphorylase

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15
Q

What is glucose-1-phosphate converted to in glycogenolysis

A

Glucose-6-phosphate

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16
Q

What happens to liver glucose-6-phosphate (2)

A

It is de-phosphorylated
Glucose is released into bloodstream

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17
Q

what happens to muscle glucose-6-phosphate (2)

A

it cannot be de-phosphorylated
Used to provide energy via cellular respiration

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18
Q

When must new glucose be synthesised

A

during prolonged starvation

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19
Q

What are the precursors of gluconeogenesis (3)

A

lactate
Amino acids
Glycerol

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20
Q

What converts lactate to glucose

A

the liver

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21
Q

How are amino acids obtained for gluconeogenesis

A

derived from muscle protein by proteolysis

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22
Q

How is glycerol obtained for gluconeogenesis

A

derived from triglycerides by lipolysis

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23
Q

What is the main site of gluconeogenesis

A

the liver

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24
Q

Why is gluconeogenesis not the reverse of glycolysis

A

Energetically unfavourable steps in glycolysis must be overcome

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25
How does gluconeogenesis alter energy distribution
Reduces liver energy to distribute glucose to other tissues
26
How is gluconeogenesis regulated (2)
by hormones Regulation by insulin is dominant
27
What does increased fat intake without increased energy expenditure lead to (2)
Increased number and size of adipocytes
28
What controls energy storage in adipose tissue (2)
Genetic and environmental factors
29
What is fat required for (3)
energy Essential fatty acids, membranes, and vesicles Transport of fat-soluble vitamins
30
What are the types of lipids (3)
Simple Compound Steroids
31
What do triglycerides consist of
one glycerol unit and three fatty acids
32
What types of fatty acids exist
saturated, unsaturated, or polyunsaturated
33
Which compound is the main energy storage form in adipose tissue
Triglycerides
34
What is the structure of fatty acids generally like
straight chain, aliphatic
35
How do the states of plant and animal fats compare
animal fats are generally solid, plants fats are generally liquid
36
What must happen to fatty acids before they are oxidised
they must be converted to CoA derivatives in the cytoplasm
37
where does further oxidation of fatty acids (after conversion to CoA derivatives) take place
Matrix of mitochondria
38
What is the significance of the carnitine shuttle (2)
A carrier mechanism that transports molecules into the mitochondrial matrix for further oxidation Results in acyl-CoA inside the matrix
39
B oxidation (4)
Cycle of reactions resulting in oxidation of fatty acids Occurs in mitochondrial matrix Requires enzymes Yields ATP
40
What are the products of β oxidation (4)
1 acetyl-CoA 1 FADH2 1 fatty acyl-CoA 1 NADH + H+
41
Where does fat absorption occur
Into mucosal cells of the intestine
42
What are the main products of fat absorption (3)
glycerol Fatty acids Monoglycerides
43
One absorbed by the intestine, where do fatty acids go
shorter chain - portal blood Longer chain (+monoglycerides) - enter lymph then blood stream
44
Once in muscle/adipose tissue, what occurs to chylomicrons
The lipids are cleaved by lipoprotein lipases
45
What are free fatty acids used for in muscle
oxidation to provide energy
46
What are free fatty acids used for in adipose tissue
Re synthesis to triaglycerols
47
How are ketone bodies formed (3)
in mitochondria of liver cells From acetyl-CoA By β oxidation
48
once produced, where do ketones go (2)
blood stream Peripheral tissues
49
Why are ketones important (2)
for energy metabolism of heart muscle and the renal cortex They can be converted back to acetyl-CoA
50
what does fatty acid oxidation produce under normal circumstances
acetyl-CoA
51
In cases of starvation/diabetes, what happens to oxaloacetate
Used for gluconeogenesis
52
How can acidosis arise in cases of starvation/diabetes (3)
fatty acids are oxidases to acetyl-CoA Acetyl-CoA is converted to ketone bodies Ketone bodies accumulate
53
What is a sign of acidosis
acetone smell on breath
54
How can acidosis be managed in cases of starvation/diabetes
starvation - sugar Diabetes - insulin
55
lipogenesis
synthesis of fatty acids
56
What can lead to fatty acid synthesis (2)
excess energy intake Excess carbohydrate intake
57
What occurs during excess carbohydrate intake (3)
Excess carbohydrates are converted to fatty acids and triglycerides Free fatty acids are bound to albumin and transported in plasma Triglycerides are transported to adipose tissue for storage
58
What transports triglycerides to adipose tissue for storage
VLDL
59
What is required for fatty acid synthesis and why
electrons It is a reductive process
60
Describe transport of acetyl-CoA for lipogenesis (2)
acetyl-CoA is synthesised in the mitochondria Citrate transports acetyl-CoA to the cytoplasm for lipogenesis
61
What is the first step required for lipogenesis (2)
activation of acetyl-CoA to malonyl-CoA Catalysed by acetyl-CoA carboxylate
62
Where is acetyl-CoA carboxylate generally expressed (2)
liver Adipose tissue
63
What catalyses the synthesis of fatty acids from Malonyl-CoA
Fatty acid synthase
64
What are the four steps of fatty acids synthesis
condensation Reduction Dehydration Reduction and release
65
Unregulated forms of fatty acid synthase is associated with what condition
cancer
66
What protein does fatty acid synthase contain (among others)
acyl-carrier protein
67
What is the longest fatty acid created by fatty acid synthase
palmitic acid 16 carbons
68
What does each cycle of reactions in lipogenesis require and why
NADPH as an electron donor
69
In lipogenesis, what is each growing acyl chain attached to
ACP
70
When is fatty acid synthesis maximal (2)
Abundant carbohydrates and energy Scarce fatty acids
71
How does insulin affect lipid metabolism
by stimulating the storage of fuels and protein synthesis
72
How does citrate affect lipogenesis
allosterically stimulates acetyl-CoA carboxylate
73
How does palmitoyl-CoA affect lipogenesis
antagonises acetyl-CoA carboxylate when fatty acids are in excess
74
What compound is required for triglyceride synthesis and what is used to produce it
Glycerol-3-phosphate is required Liver uses glycerol to produce it Adipose tissue uses glucose to produce it
75
When does adipose tissue production of triglycerides occur (2)
during a fed state When insulin stimulates adipose uptake of glucose
76
What type of reaction is involved in triglyceride synthesis
esterification
77
What does breakdown of amino acids produce (2)
ammonium Ammonia ions
78
How can nitrogen be excreted
Urea Uris acid Creatinine Ammonium ions
79
What are the three steps involved in synthesis of urea
transanimation De-animation Urea cycle
80
What occurs in the transamination step of urea synthesis
aminotransferases move the amino group from α amino acids to α keto acids Produces glutamate
81
What are the two possible routes after glutamate has been produced (transanimation)
Amino group on glutamate is transferred to pyruvate, producing alanine Or glutamine synthase adds an ammonium ion to glutamate, creating glutamine
82
What is the function of alanine and glutamine
to carry nitrogen from the blood to the liver
83
Where does deanimation occur
liver
84
What happens during de-animation
The amino group of glutamate/alanine is converted to a free ammonium ion
85
What is generated as an end product of urea synthesis
fumarate
86
How can carbon be transported back to the mitochondrial matrix after synthesis of urea in the cytoplasm (2)
fumarate is converted to malate Carbon is transported via the malate-aspartame shuttle
87
What can ketogenic amino acids give rise to (3)
acetyl-CoA or acetoacetyl-CoA Ketone bodies Fatty acids
88
What can glycogenic amino acids be degraded to form
pyruvate or TCA cycle intermediates
89

Medicine year 1 (35 decks)

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