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Biochemistry Flashcards

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1
Q

Definition of glycogenesis

A
  • synthesis of glycogen from glucose
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2
Q

Define glycogenolysis

A
  • breakdown of glycogen to form glucose
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3
Q

Define gluconeogenesis

A
  • new synthesis of glucose from metabolic precursors
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4
Q

What is the main storage form of glucose in liver and muscle cells?

A
  • glycogen
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5
Q

Glycogen is a ______

monosaccharide or polysaccharide?

A
  • polysaccharide
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6
Q

what is the purpose of liver glycogen?

A
  • broken down between meals and released to maintain blood glucose levels for red blood cells and brain
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7
Q

what is the purpose of muscle glycogen?

A
  • provides energy via glycolysis and the TCA during bursts of physical activity
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8
Q

what carbons are linked between glucose molecules in glycogen?

A
  • a 1-4 glycosidic links
  • branches by a 1-6 glycosidic links

*** exam

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9
Q

What is required to add glucose to an existing glycogen chain?

A
  • a glycogen primer [at least 4 glucose residues]
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10
Q

What is the name of the protein a glycogen primer binds to?

A
  • glycogenin
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11
Q

What is the enzyme that converts glucose-1-phosphate to UDP-glucose?

A
  • UDP - glucose pyrophosphorylase
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12
Q

Name of enzyme that converts UDP-glucose to glycogen?

A
  • glycogen synthase
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13
Q

What is UDP - glucose?

A
  • activated intermediates

- activated form of glucose

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14
Q

What is the role of glycogen synthase?

A
  • synthesis of glycogen from UDP-glucose
  • adds 1 glucose molecule to glycogen at a time
  • rate limiting enzyme
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15
Q

What is the name of the enzyme that adds a branch to the 1-6 glycosidic branch in glycogen?

A
  • transglycosylase
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16
Q

What is glycogenolysis catalysed by?

A
  • glycogen phosphorylase
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17
Q

What are 3 precursors that can be used to generate glucose in gluconeogenesis?

A
  • lactate
  • amino acids
  • glycerol
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18
Q

Gluconeogenesis is essentially the reverse of glycolysis

True or False

A

FALSE

  • if it was simply in reverse you would need to overcome chemically challenging energy steps
  • it employs 3 unique enzymes to over come these barriers
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19
Q

What is the last intermediate in the TCA (4 carbon?)

A
  • oxaloacetate
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20
Q

How many liver enzymes are required in gluconeogenesis?

A
  • 3 enzymes
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21
Q

What is the role of PEP CK

PEP carboxykinase

A

rate limiting gluconeogenesis

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22
Q

What is the cori cycle?

A
  • process of recovering lactate that is generated in the skeletal muscle
  • converted back to glucose, through the gluconeogenesis pathway
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23
Q

2 functions of insulin

A
  • burns of glucose –> glycolysis

- activates glycogen synthesis

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24
Q

what are fats important for?

A
  • as an energy source
  • essential fatty acids
  • for fat-soluble vitamins
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25
What are the 3 different lipid compounds?
- simple lipids - compound lipids - steroids
26
What is the structure of a triglycerides?
- glycerol and 3 fatty acids
27
Fatty acids are mainly bent structures true/false?
- FALSE | - mainly straight chains
28
What is a cis group?
- the 2 R groups are on the same side of the double bond | - cis --> think sisters (same side)
29
What are the 3 main products of fat digestion?
- glycerol - fatty acids - monoglycerides
30
What are chylomicrons?
- transport lipids absorbed from the intestine to adipose
31
Define lipolysis?
- breakdown of lipids | - by hormone sensitive lipases
32
Where is fat stored?
- in adipose tissue
33
Fatty acids are converted to ________ in the cytoplasm
- fatty acids oxidised to generate energy | - they are converted into CoA derivatives
34
Name a rate limiting step for the process of energy conversion of lipids to be metabolised
- carnitine shuttle
35
What is the carnitine shuttle?
- acyl- CoA transferred to carnitine | - facilitates acyl-CoA transport into the mitochondrial matrix
36
What is a rate limiting precursor for the TCA?
- Acetyl CoA
37
What is the end product of beta oxidation?
- Acetyl CoA
38
Where are ketone bodies formed?
- liver mitochondria
39
When does the formation of ketone bodies usually occur?
- in starvation and diabetes
40
How many cycles of oxidation is involved in beta oxidation for an even saturated fat?
(C2n) | n-1 oxidation occurs for complete catalysis
41
Malonyl CoA?
- precursor of the synthesis of fatty acids | - lipid anabolism
42
Define lipogenesis?
- fatty acid synthesis - occurs mainly in the liver - mainly takes place during excess energy intake
43
Where is Acetyl-CoA generated?
- in the mitochondria
44
What makes Acetyl-CoA, what enzyme?
- pyruvate dehydrogenase complex
45
Fatty acid synthase job?
- catalyses synthesis of saturated long-chain fatty acids from malonyl-CoA, acetyl-CoA and NADPH
46
4 Steps of fatty acid synthesis?
- condensation - reduction - dehydration - reduction and release
47
What carries the synthesised lipid after it is made?
- acyl-carrier protein (ACP)
48
What does insulin signal?
- fed state | - stimulates storage of fuels and synthesis of proteins
49
What does glucagon signal?
- starved state
50
What does epinephrine signal?
- requirement for energy | - mobilise glycogen
51
Where are the glycerols for triglycerides synthesised?
- liver | - adipose tissue
52
What is a major site of amino acid degradation?
- liver
53
What is protein turnover?
- tightly regulated - different rates - damaged proteins have to be removed
54
Nitrogen containing excretory molecules?
- urea - uric acid - creatinine - ammonium ion
55
Where is urea formed?
- the liver
56
What happens to glutamic acid during the formation of urea?
- de-amination
57
What are aminotransferases involved in?
- moving the amino group from the a-amino acids to a a-keto acid - transamination
58
Where does deamination/urea cycle occur?
- in the liver
59
What occurs during deamination?
- amino group of glutamate is converted to free ammonium ion
60
What is an end product of the urea cycle?
- fumarate | - end-product in the cytosol
61
3 different inherited disorders of amino acid degradation
- alcaptonuria - maple syrup urine disease - phenylketonuria
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