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BM 210: Introduction to Biochemistry > Block D Part 1: Absorptive State > Flashcards

Block D Part 1: Absorptive State Flashcards

1
Q

What are the 5 types of food group?

A

Carbohydrates
Proteins
Vitamins and minerals
Roughage and water
Fats
(Lecture 1, Slide 4)

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2
Q

What is glycolysis?

A

The sequence of reactions that metabolises 1 molecule of glucose into 2 molecules of pyruvate with the production of 2 molecules of ATP
(Lecture 1, Slide 5)

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3
Q

What is the full equation of glycolysis?

A

D-glucose + 2 NAD+ + 2 ADP + 2Pi —> 2 Pyruvate + 2 ATP + 2 NADH + 2H+ + 2 H2O
(Lecture 1, Slide 5)

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4
Q

What 3 reactions does the glycolysis pathway involve?

A

2 Phosphorylation reactions forming fructose 1,6-bisphosphate
Cleavage of each fructose 1,6-bisphosphate to 2 triose phosphate
A series of molecular rearrangements
(Lecture 1, Slide 6)

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5
Q

Is glycolysis performed in aerobic or anaerobic conditions?

A

Anaerobic
(Lecture 1, Slide 6)

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6
Q

What in the cell needs to be maintained during glycolysis?

A

The redox balance
(Lecture 1, Slide 8)

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7
Q

How and why is NAD+ regenerated?

A

NAD+ is regenerated through the metabolism of pyruvate and needs to be regenerated as without it glycolysis will stop
(Lecture 1, Slide 8)

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8
Q

What are the 2 roles of the glycolysis pathway?

A

Degradation of glucose to generate ATP
Provision (Supplying) of building blocks for synthetic reactions
(Lecture 1, Slide 9)

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9
Q

What can be potential sites of control in glycolysis?

A

Enzymes catalysing irreversible reactions
(Lecture 1, Slide 9)

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10
Q

What are the 3 controls sites in glycolysis?

A

Hexokinase
Phosphofructokinase
Pyruvate kinase
(Lecture 1, Slide 9)

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11
Q

What inhibits hexokinase in glycolysis?

A

It’s product glucose 6-phosphate
(Lecture 1, Slide 9)

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12
Q

What inhibits and activates phosphofructokinase in glycolysis?

A

It’s inhibited by ATP, low pH, citrate and is activated by AMP and fructose 2,6-biphosphate
(Lecture 1, Slide 9)

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13
Q

What inhibits and activates pyruvate kinase in glycolysis?

A

ATP and alanine inhibit and fructose 1,6-biphosphate activates
(Lecture 1, Slide 9)

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14
Q

What is fructose 2,6-biphosphate generated by?

A

Phosphofructokinase 2
(Lecture 1, Slide 10)

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15
Q

What is phosphofructokinase 2?

A

A bifunctional enzyme responsible for the synthesis and hydrolysis of fructose 2,6-biphosphate
(Lecture 1, Slide 11)

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16
Q

What is a bifunctional enzyme?

A

An enzyme that can process 2 distinct catalytic activities, usually in the same pathway, within 1 polypeptide chain
(Lecture 1, Slide 11)

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17
Q

How is phosphofructokinase regulated?

A

Reciprocal control by phosphorylation of serine 460 by protein kinase A - which activates it (it is deactivated when dephosphorylated again)
(Lecture 1, Slide 11)

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18
Q

What are the 2 fates of pyruvate in conditions when there is a lack of oxygen?

A

Either gets converted to lactate in mammals or acetaldehyde which then gets converted ethanol in yeast
(Lecture 1, Slide 12)

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19
Q

What is the fate of pyruvate in conditions with sufficient oxygen?

A

It gets converted to Acetyl CoA which then gets oxidised further in the TCA cycle and electron transport chain
(Lecture 1, Slide 12)

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20
Q

How is lactate (lactic acid) produced by the body?

A

Lactate is produced by muscles when the body cannot supply enough oxygen
(Lecture 1, Slide 14)

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21
Q

Why can Erythrocytes (red blood cells) not fully oxidise glucose?

A

As they lack mitochondria
(Lecture 1, Slide 14)

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22
Q

What is oxygen debt?

A

The term that refers to the bodies need to produce more oxygen post-exercise in order to convert the body back into it’s pre-exercise state
(Lecture 1, Slide 14)

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23
Q

Why does the body need to take in extra oxygen post-exercise?

A

To oxidise lactate
(Lecture 1, Slide 14)

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24
Q

Why does lactate need to be converted back into pyruvate?

A

As it’s a dead end in metabolism
(Lecture 1, Slide 14)

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25
Q

What are 2 ways in which lactate can be converted back into pyruvate?

A

Cardiac muscles cells oxidise lactate into pyruvate
Liver cells convert lactate into pyruvate which is then followed by gluconeogenesis to produce glucose
(Lecture 1, Slide 14)

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26
Q

What is the first reaction to convert pyruvate into acetyl CoA?

A

Decarboxylation of pyruvate (3 carbons) to a 2-carbon alcohol
(Lecture 1, Slide 15)

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27
Q

What is the 2nd reaction to convert pyruvate to acetyl CoA?

A

Oxidation of the alcohol to acetic acid with reduction of NAD+ to NADH
(Lecture 1, Slide 15)

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28
Q

What is the 3rd reaction to convert pyruvate to acetyl CoA?

A

Esterification to coenzyme A > acetyl CoA > TCA cycle
(Lecture 1, Slide 15)

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29
Q

What does glycogen function as?

A

A reserve of glucose when metabolic demand for glucose outpaces the cell’s ability to obtain it from extracellular sources
(Lecture 1, Slide 18)

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30
Q

How does glycogen maintain blood glucose level?

A

Controlled release of glucose from glycogen
(Lecture 1, Slide 18)

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31
Q

What 2 muscles is glycogen mainly stored in?

A

Liver and skeletal muscle
(Lecture 1, Slide 18)

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32
Q

In liver hepatocytes, what percentage of fresh weight can glycogen make up?

A

up to 8-10% of fresh weight (100-120g in adults)
(Lecture 1, Slide 18)

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33
Q

What percentage of muscle mass can be glycogen?

A

1-2%
(Lecture 1, Slide 18)

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34
Q

Why is glycogen stored in the uterus during pregnancy?

A

To nourish the embryo
(Lecture 1, Slide 18)

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35
Q

How is glycogen different to amylopectin of starch?

A

It has a branch every 10th glucose
(Lecture 1, Slide 19)

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36
Q

What does anabolism mean?

A

Synthesis
(Lecture 1, Slide 20)

37
Q

How and what catalyses the initiation stage of glycogen anabolism?

A

In an autocatalytic synthesis by glycogenin
(Lecture 1, Slide 20)

38
Q

What catalyses the elongation stage of glycogen anabolism?

A

Glycogen synthase in co-operation with the branching enzyme
(Lecture 1, Slide 20)

39
Q

What is glycogenin?

A

An enzyme involved in glycogen biosynthesis
(Lecture 1, Slide 21)

40
Q

What classification of enzyme is glycogenin?

A

Glycosyl-transferase
(Lecture 1, Slide 21)

41
Q

How does glycogenin result in further glucose monomers being added?

A

By acting as a primer
(Lecture 1, Slide 21)

42
Q

What 2 things does glycogenin bind together to act as an autocatalyst?

A

It binds glucose from UDP-glucose (Uridine di-phosphate glucose) to a hydroxyl group of tyrosine 194
(Lecture 1, Slide 21)

43
Q

What is glycogen synthase?

A

The main enzyme involved in glycogen polymerization
(Lecture 1, Slide 23)

44
Q

What condition must be met for glycogen synthase to be able to add to existing chain of glucose?

A

The chain must be at least 8 glucose residues long (elongation stage)
(Lecture 1, Slide 23)

45
Q

What 2 things regulate the activity of glycogen synthase?

A

Covalent modifications and an allosteric mechanism
(Lecture 1, Slide 23)

46
Q

What 2 things is glycogen synthase phosphorylated by?

A

Protein kinase A and glycogen synthase kinase 3 (GSK3)
(Lecture 1, Slide 23)

47
Q

What effect does phosphorylation of glycogen synthase have on it?

A

It converts the active a form into an inactive b form
(Lecture 1, Slide 23)

48
Q

Under what condition is the inactive b form of glycogen synthase still active?

A

When a high level of the allosteric activator glucose 6-phosphate is present
(Lecture 1, Slide 23)

49
Q

What is uridine diphosphate glucose?

A

An activated form of glucose which is the immediate precursor for glycogen synthesis
(Lecture 1, Slide 24)

50
Q

What is UDP-glucose formed from?

A

It’s formed from glucose-1-phosphate
(Lecture 1, Slide 25)

51
Q

What are the 3 equations for the formation of UDP-glucose?

A

glucose-1-phosphate + UTP <> UDP-glucose + PPi

PPi + H2O > 2Pi (inorganic pyrophosphatase)

Overall:
glucose-1-phosphate + UTP > UDP-glucose + 2Pi
(Lecture 1, Slide 25)

52
Q

Why is the overall reaction of UDP-glucose formation irreversible?

A

As spontaneous hydrolysis of the P bond in pyrophosphate (PPi) drives the overall reaction making it irreversible
(Lecture 1, Slide 25)

53
Q

What is the only energy cost for glycogen synthesis?

A

Cleavage of PPi
(Lecture 1, Slide 25)

54
Q

Where are glucose residues added to glycogen?

A

To non-reducing terminal residues of glycogen
(Lecture 1, Slide 26)

55
Q

What is the substrate in glycogen synthesis and what is released?

A

UDP-glucose is the substrate and UDP is released as a reaction product
(Lecture 1, Slide 26)

56
Q

What linkage does glycogen contain?

A

An α-1,4-glycosidic linkage
(Lecture 1, Slide 26)

57
Q

What is amylo (1,4—> 1,6) transglycosylase?

A

A branching enzyme
(Lecture 1, Slide 28)

58
Q

What does amylo (1,4 —> 1,6) transglycosylase do?

A

Transfer a block from the non-reducing end of the chain to a more interior site
(Lecture 1, Slide 28)

59
Q

What 2 conditions does the block transferred by amylo (1,4 —> 1,6) transglycosylase need to meet?

A

Usually 7 residues long, must include the non-reducing terminus
(Lecture 1, Slide 28)

60
Q

Where and how does amylo (1,4 —> 1,6) transglycosylase attach the block it moves to?

A

By an α-(1,6) linkage at least 4 linkages from the nearest branch point
(Lecture 1, Slide 28)

61
Q

What are 3 reasons that branching is so important in glycogen?

A

Answers include:

It increases its solubility

Allows generation of a large osmotically inactive storage form of glucose

It creates a large number of terminal residues which are the site of action of glycogen phosphorylase and glycogen synthase

It increases the rate of glycogen synthesis and degradation
(Lecture 1, Slide 29)

62
Q

Where are fatty acids synthesised?

A

In the cytoplasm
(Lecture 1, Slide 32)

63
Q

What state must a cell be in to synthesise a carbohydrate and why?

A

The “fed” state (after meeting a meal) when more carbohydrate is available than needed for the TCA cycle
(Lecture 1, Slide 32)

64
Q

What is required to build new fatty acids?

A

ATP
(Lecture 1, Slide 32)

65
Q

What remains bound to the intermediates in fatty acid biosynthesis?

A

An acyl-carrier protein (ACP)
(Lecture 1, Slide 32)

66
Q

How does the fatty acid chain grow?

A

By the sequential addition of two-carbon units derived from acetyl CoA
(Lecture 1, Slide 32)

67
Q

What is the activated donor of two-carbon atoms used to grow a fatty acid chain?

A

Malonyl-ACP
(Lecture 1, Slide 32)

68
Q

What is the transfer of 2 carbon units derived from acetyl CoA to grow a fatty acid chain driven by?

A

A decarboxylation reaction releasing CO2
(Lecture 1, Slide 32)

69
Q

What are fatty acids stored as?

A

Triacylglycerides (TGs)
(Lecture 1, Slide 32)

70
Q

How is Palmitate made?

A

1 acetyl CoA + 7 malonyl CoA = Palmitate (C16)
2 carbon units are added successively to a growing hydrocarbon chain
(Lecture 1, Slide 34)

71
Q

What is a transacylase?

A

An enzyme that that catalyses the transfer of an acyl group
(Lecture 1, Slide 36)

72
Q

What is the reaction of Acetyl-CoA and Malonyl-CoA with a transacylase?

A

Acetyl-CoA + ACP —> Acetyl-ACP + CoA
Malonyl-CoA + ACP —> Malonyl-ACP + CoA
(Lecture 1, Slide 36)

73
Q

What type of pathway is Acetyl ACP + Malonyl ACP reacting to eventually give Butyryl AC?

A

A spiral pathway
(Lecture 1, Slide 37)

74
Q

How is the pathway of Acetyl ACP + Malonyl ACP reacting to eventually give Butyryl ACP a spiral pathway?

A

As Butyryl ACP goes back up to react with another malonyl ACP
(Lecture 1, Slide 37)

75
Q

What is triacylglycerol?

A

A compact, high-energy storage molecule
(Lecture 1, Slide 39)

76
Q

What are triacylglycerols made from?

A

3 fatty acid groups + glycerol-3 phosphate
(Lecture 1, Slide 40)

77
Q

What are 3 tissues that triacylglycerols synthesised in?

A

Liver, adipose tissue and intestinal tract
(Lecture 1, Slide 40)

78
Q

How are triacylglycerols synthesised in the liver?

A

From fatty acids made using glucose or amino acid side chains
(Lecture 1, Slide 40)

79
Q

When are triacylglycerols made in intestines and adipose tissue?

A

During transport of dietary fat
(Lecture 1, Slide 40)

80
Q

Can triacylglycerols cross cell membranes?

A

No
(Lecture 1, Slide 40)

81
Q

What must happen for triacylglycerols to be able to cross cell membranes?

A

It has to be broken down with the help of lipases to get in and out of cells
(Lecture 1, Slide 40)

82
Q

How are triacylglycerols carried around the body?

A

By lipoproteins in the plasma
(Lecture 1, Slide 40)

83
Q

What 2 lipoproteins transport triacylglycerols around the body?

A

Very low density lipoprotein (VLDL)
Chylomicrons
(Lecture 1, Slide 40)

84
Q

Where do very low density lipoprotein (VLDL) transport triacylglycerols?

A

From the liver to peripheral tissues
(Lecture 1, Slide 40)

85
Q

Where does chylomicrons transport triacylglycerols?

A

From the intestine to peripheral tissues
(Lecture 1, Slide 40)

86
Q

What needs to happen before triacylglycerols are synthesised?

A

Each fatty acids needs to be activated
(Lecture 1, Slide 42)

87
Q

How is each fatty acid activated before triacylglycerol synthesis?

A

The thiol group (R-S-H) of CoA forms a high energy thioester bond with the carboxylic acid group of the fatty acid
(Lecture 1, Slide 42)

88
Q

What is the reaction which activates fatty acid synthesis before triacylglycerol synthesis driven by?

A

ATP (as 2 high energy bonds are used)
(Lecture 1, Slide 42)

89
Q
A

BM 210: Introduction to Biochemistry (12 decks)

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