Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Presemester DENT > Essential Metabolism > Flashcards

Essential Metabolism Flashcards

1
Q

What important factors influence enzyme activity in the body?

A

Covalent modification (eg phosphorylation)

Synthesis/degradation (protein availability)

Temperature

pH (ionic interactions influence protein shape)

Substrate availability [S]

Compartmentalisation (allows incompatible reactions to take place simultaneously within the cell)

Activators and deactivators (regulatory molecules)

Cofactors/coenzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the difference between cofactors and coenzymes?

A

Coenzymes are organic molecules that act as cofactors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How is energy stored in cells?

A

ATP

NAD(P)H

FADH2

Acetyl CoA

High-energy linkage

Phosphate

Electrons and hydrogens

Acetyl groups

Energy can also be stored as ion gradients and high energy phosphate bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are redox reactions?

A

Reactions that involve electron transfer or can involve transfer of H enzymes are called dehydrogenases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the electron redox potential (aka E’)?

A

Measure of ability of one molecule to pass electrons to another.

More negative E’ indicates stronger reductant so more readily donates electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens to energy when electrons are donated?

A

When donated from compound with more negative redox potential to one that is less negative/more positive energy is released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What causes abnormal metabolism?

A

Abnormal metabolism results from nutritional deficiency, enzyme deficiency, or abnormal secretion of hormones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the main metabolic fuels?

A

Glucose and fats

Proteins can also be used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the pentose phosphate pathway?

A

A versatile pathway that does not make ATP but produces ribose 5-P for nucleotides

Supplies NADPH for reductive biosynthesis

Provides a pathway for metabolism of excess pentoses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why do red blood cells need NADPH?

A

To reduce glutathione which is important for RBC integrity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What sections does the pentose phosphate pathway consist of?

A

Oxidative section which gets ribose-5P and NADPH

Nonoxidative section which manipulates the ribose-5P based on cell’s needs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is considered when deciding the fate of the nonoxidative section of the Pentose Phosphate Pathway?

A

If the cell needs equal amounts of ribose-5P and NADPH oxidative PPP proceeds.

If the cell needs lots of NADPH but no ribose-5P then nonoxidative PPP converts excess ribose-5P to glucose-6P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the function of G6PDH?

A

It converts Glucose-6-phosphate to 6-phosphogluconate which is the first step of the oxidative phase of PPP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are some important functions of NADPH?

A

Reductive biosynthesis (form fatty acids, sterols, etc)

Glutathione production which allows cells to reduce oxidative damage by free radicals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens to glucose in the absence of oxygen?

A

Fermentation occurs, pyruvate is produced via glycolysis and then the pyruvate is converted to lactate via lactate dehydrogenase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What triggers the fermentation pathway?

A

Accumulation of NADH due to slowing down of electron transport chain due to lack of oxygen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is required for fermentation to take place?

A

Pyruvate and NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens to lactate that is produced?

A

It is acidic so it is exported via the cori cycle.

The lactate is exported into the blood and then processed by the liver and converted by LDH then gluconeognesis into glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which enzyme phosphorylates glucose?

A

Hexokinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which tissues use glucose preferentially?

A

Muscles and the brain (only fuel for brain under normal circumstances)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What do ketone bodies get produced from?

A

From acetyl CoA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the key enzymes of glycolysis?

A

Hexokinase (converts glucose to glucose-6-phosphate)

Phosphofructokinase (provides energy for glycolysis to proceed; producing fructose 1,6-bisphosphate)

Pyruvate kinase (produces pyruvate in final step)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is glycolysis regulated?

A

Citrate and ATP have a negative feedback action on phosphofructokinase and on pyruvate kinase.

Pyruvate kinase increases with more increase in fructose-1,6-bisphosphate to counteract the negative feedback of increased ATP and citrate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What feedback mechanisms act on phosphofructokinase-1 in glycolysis?

A

ADP and AMP increase rate

ATP and citrate decrease rate (inhibitory)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What feedback mechanisms act on hexokinase?

A

Pi’s increase activity

G6P inhibit hexokinase-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What feedback mechanisms act on pyruvate kinase?

A

ATP inhibits pyruvate kinase

Fructose-1,6-bisP increases its activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How much glucose is needed by the brain?

A

120g/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Where does most gluconeogenesis occur?

A

> 90% of gluconeogenesis occurs in the liver and the kidneys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does gluconeogenesis occur?

A

It is the reverse of glycolysis except 3 enzymes (pyruvate kinase, fructose-1,6-bisphosphate, and hexokinase) are not used and these steps are bypassed by 3 other enzymes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How do amino acids get converted into glucose?

A

They are converted to oxaloacetate and then undergo gluconeogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How do fatty acids get converted into glucose?

A

Glycerol is converted into dihydroxyacetone phosphate which undergoes gluconeogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Can acetyl-CoA be converted into glucose?

A

No, they can only be converted to ketone bodies if not in the TCA cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How is the reaction of pyruvate kinase reversed in gluconeogenesis?

A

2 reactions:

Pyruvate -> oxaloacetate via pyruvate carboxylase

Oxaloacetate -> Phosphoenolpyruvate via phosphoenol pyruvate carboxylase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What other substrate is required for Pyruvate -> oxaloacetate reaction?

A

ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What other substrate is required for Oxaloacetate -> Phosphoenolpyruvate reaction?

A

GTP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What enzyme catalyses the reverse reaction to phosphofructose kinase in gluconeogenesis?

A

Fructose-1,6-bisphosphatase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What enzyme catalyses the reverse reaction to hexokinase in gluconeogenesis?

A

Glucose-6-phosphatase

38
Q

What is the overall reaction for gluconeogenesis?

A

2pyruvate + 4ATP + 2GTP + 2NADH + 6H2O -> glucose + 4ADP + 2GDP +6Pi +2NAD+ + 2H+

39
Q

Where does glycolysis occur?

A

In the cytosol

40
Q

Where does gluconeogenesis occur within the cell?

A

Pyruvate carboxylase - mitochondria

Phosphoenolpyruvate carboxykinase (GTP) - cytoplasm

Fructose-1,6-bisphosphatase - cytoplasm

Glucose 6-phosphatase - ER

41
Q

Where is glucose-6-phosphatase located? why?

A

Glucose-6-phosphatase is only located in tissues responsible for maintaining blood glucose (liver and kidneys)

This is to ensure that the liver and kidneys store the glucose and don’t use it up.

42
Q

What kind of control is G6phosphatase subject to?

A

Substrate level (i.e more substrate = faster reaction)

43
Q

How many proteins is the glucose 6-phosphatase complex composed of?

A

5 proteins

Stabilising protein necessary for function

T1, 2, and 3 act as transporters in the ER

44
Q

How are gluconeogenesis and glycolysis regulated relative to each other?

A

They are reciprocally regulated. Molecules that inhibit gluconeogenesis often activate glycolysis and vice versa

45
Q

What molecules are important for regulation of gluconeogenesis?

A

Fructose 2,6-bisphosphate

AMP

ATP and citrate

46
Q

What is fructose 2,6-bisphosphate?

A

A potent allosteric regulatory molecule which activates phosphofructokinase and inhibits fructose-1,6-bisphosphatase thus activating glycolysis and inhibiting gluconeogenesis

47
Q

What does a high concentration of AMP indicate?

A

Cell’s energy charge is low and signals a need for ATP

48
Q

What does high ATP and citrate indicate about a cell?

A

Cell’s energy charge is high and intermediates are abundant

49
Q

What substrates can enter gluconeogenesis?

A

Pyruvate and molecules that can be converted into pyruvate

Lactate

TCA intermediates

Glycerol

Amino acids (most)

Galactose and fructose (all other monosaccharides can enter through these)

50
Q

What molecules can not be substrates for gluconeogenesis?

A

Acetyl CoA

Fatty acids

Lysine and Leucine

51
Q

What happens to the amino groups of amino acids after they are converted into substrates of glycolysis/gluconeogenesis?

A

They are converted into alpha ketoglutarate

52
Q

Lactate and alanine are glucogenic. What does glucogenic mean?

A

Can be metabolised into glucose

53
Q

What is the reaction that takes place between pyruvate and glutamate?

A

pyruvate + glutamate

alanine + α-ketoglutarate

54
Q

Are amino acids glucogenic or ketogenic?

A

They can be glucogenic, ketogenic, or both

55
Q

Which amino acids are glucogenic?

A

All but lysine and leucine are partly glucogenic

56
Q

Which amino acids are ketogenic and glucogenic?

A

Aromatic AAs

57
Q

Which amino acids are ketogenic but not glucogenic?

A

Leucine and lysine

58
Q

What happens to fatty acids in metabolism?

A

They are converted to acetyl CoA which means they can’t be converted to glucose

59
Q

What enzyme produces glycogen?

A

Glycogen synthase

60
Q

How is glycogen formed from glucose?

A

UDP-glucose is formed containing uracil which helps extend the growing chain of glucose subunits

61
Q

Where is pyruvate broken down into acetyl CoA?

A

in the matrix of the mitochondria

62
Q

Which molecules can be converted into acetyl-CoA?

A

Glycogen

Fatty acids

Amino acids

63
Q

How is pyruvate oxidised into Acetyl-CoA?

A

Via a multi-enzyme complex called pyruvate dehydrogenase

64
Q

What regulation happens in high energy to pyruvate dehydrogenase?

A

ATP

Acetly CoA (molecule inhibits its own production)

NADH

65
Q

What regulation happens in low energy to pyruvate dehydrogenase?

A

Pyruvate increases PDH activity

ADP also increases PDH activity

66
Q

How is pyruvate dehydrogenase regulated covalently?

A

PDH kinase and phosphatase

67
Q

Where does the TCA cycle take place and what happens in cells that don’t undergo the TCA cycle much?

A

In the mitochondria. Cells with little or no mitochondria rely on glycolysis primarily

68
Q

What are the products of the TCA cycle?

A

One turn of the cycle produces 3 NADH, 1 GTP, and 1 FADH2

Releases 2 CO2

69
Q

Which tissue is the most important tissue for metabolism?

A

Liver is the only tissue in which all metabolic processes occur significantly

70
Q

What is fumarase deficiency?

A

Fumarase deficiency is an autosomal recessive disorder causing severe neurological impairment, encephalopathy and dystonia

71
Q

What abnormalities can affect the TCA cycle?

A

Very few genetic (incompatible with life)

TCA is aerobic so anoxia or hypoxia lead to total or partial inhibition of the cycle

4 B vitamins have precise roles in TCA cycle. Riboflavin (FAD), Niacin (NAD), Thiamine (alpha-KG) and pantothenic acid (CoA)

72
Q

How many complexes are in the electron transport chain?

A

5, 4 electron transporters and ATP synthase

73
Q

How do electrons get carried by complexes?

A

They have haem groups

74
Q

What does the proton gradient do?

A

Voltage gradient drives ADP-ATP exchange

pH gradient drives pyruvate entry into mitochondria and phosphate import

75
Q

How is oxidative phosphorylation regulated?

A

Cellular energy demands dictate ETC.

Intracellular [ADP]
& ratio of [ATP] : ([ADP][Pi]). When the cell needs more
ATP, the ETC is activated by high [ADP] & [Pi].

[ATP] & [ADP] set the rate of e- transfer through
ETC via a series of coordinated controls on respiration,
including glycolysis & TCA cycle.

76
Q

What do carbon monoxide and cyanide do?

A

Binds to Fe of cytochrome oxidase (Complex IV) preventing electron transport and thus preventing ATP production via oxidative phosphorylation

77
Q

What does antimycin A do?

A

blocks electron transport to cytochrome c1

78
Q

What does rotenone do?

A

Blocks NADH from binding to complex 1

79
Q

What are the mechanisms of disease in metabolism?

A

Accumulation of toxin

Energy deficiency

Deficient production of essential metabolite/structural component

80
Q

How are inherited metabolic disorders detected?

A

Heterozygote carriers are often found during screening of family members of an affected individual.

Prenatal diagnosis (eg cystic fibrosis)

Neonatal screening (Eg PKU)

Neonate developing symptoms in first few weeks

Adult onset (huntington’s disease)

81
Q

What kind of genetic defects are most commonly seen in inherited metabolic disorders?

A

All feature a genetic defect (often a result of single base substitution or deletion), reduced synthesis or absence of particular protein or D in 1° structure.

More than 4000 disorders involving single genes.
Most inherited disorders are autosomal recessive,
heterozygotes usually normal.

Many diseases have a defective enzyme that causes the disorder

82
Q

True or False:

Most Inborn Errors of Metabolism (IEM) diseases are recessive and so a negative family history is not reassuring

A

True

83
Q

How are IEM disorders investigated?

A

Consanguinity, ethnicity

Neonatal deaths, foetal deaths

Maternal family history:

Males - X linked disorders

All - mitochondrial DNA is maternally inherited

84
Q

True or False:

A positive family history may be helpful.

A

True

85
Q

What kind of disorders are IEMs most commonly?

A

Enzyme deficiencies

86
Q

What are possible consequences of enzyme deficiency?

A

Decrease in product

Accumulation of metabolite

Increased formation of other metabolites

87
Q

What are the symptoms of inherited disorders of metabolism?

A

Non-specific symptoms include:

Vomiting, lethargy

Failure to thrive, feeding difficulties

Respiratory distress

Hypotonia, seizures

Hypothermia

Other “telling”signs include:

Ocular findings

Hepatosplenomegaly

Cardiomyopathy

Abnormal odour,

Unusual skin &/or hair

88
Q

What enzyme is absent in classical galactosaemia?

A

UDP - glucose:galactose 1-P uridyltransferase

89
Q

How is galactose metabolised?

A

Milk -> Lactose -> Glucose + Galactose -> Galactose - 1-P —(UDP-glucose:Galactose-1-P uridyltransferase)—> Glucose-1-P -> Glucose-6-P -> Pyruvate

90
Q

How is classical galactosaemia treated?

A

Galactose free diet and opthalmology and developmental follow up

91
Q

What are the symptoms of classical galactosaemia?

A

Mental retardation

Jaundice

Hepatomegaly

Cirrhosis

Infantile cataracts

Hepatic failure and death

92
Q

What are the other causes of galactosaemia?

A

Galactokinase deficiency (galactitol is produced which causes infantile cataracts

Galactonate production

Presemester DENT (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions