Brainscape's Knowledge GenomeTM

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


See full index

MEH > 3 MEH > Flashcards

3 MEH Flashcards

1
Q

By which organ is most alcohol metabolised?

A

> 90% is metabolised by the liver

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

The alcohol not metabolised by the liver is excreted passively by…

A

Urine and breath

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

What is the final product of alcohol metabolism?

A

acetyl-CoA

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

Which two major enzymes are involved in alcohol oxidation?

A
  1. Alcohol dehydrogenase

2. Aldehyde dehydrogenase

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

Describe alcohol metabolism pathway. (3 molecules, 2 enzymes)

A 
1. Alcohol (ethanol)
... alcohol dehydrogenase ...
2. Acetaldehyde
... aldehyde dehydrogenase ...
3. Acetate
Acetate is then conjugated to coenzyme A to give acetyl-CoA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which moleucle is associated with the feling of “hangover”?

A

Acetaldehyde (produced by covnersion of enthanol by alcohol dehydrogenase)

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

Why is alcohol metabolism detrimental to the liver?

A

Because the 2 enzymes responsible for alcohol metabolism use NAD and produce NADH

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

Why it is useful that alcohol metabolism gives acetyl-CoA as a final product?

A

Acetyl-CoA is the central molecule to metabolism and will be able to enter TCA cycle or be utilised for fatty acid synthesis

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

What can you say abiut aldehyde dehydrogenase’s Km, and what impact does it have on the liver?

A

aldehyde dehydrogenase has a LOW Km. This means that it will work at a high rate, so keep on top of the production of acetaldehyde which is very toxic for the liver.
But in excessive consuption context, acetaldehyde dehydrogenase can’t cope with all the acetaldehyde and it builds up causing liver damage.

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

Which molecules (involved in alcohol metabolism) cause changes in liver metabolism if present in excessive amounts?

A
  • excessive NADH

- excessive Acetyl-CoA

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

What is corrhosis?

A

Cirrhosis means scarring. It is the fibrosis in the liver associated with scarring.

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

Why is it a problem that alcohol metabolism uses NAD? (3 consequences)

A
  1. Inadequate NAD for comversion of lactate into pyruvate so lactic acid builds up = lactic acidosis
  2. Inadequate NAD for glycerol metabolism - deficit in gluconeogenesis and so hypoglycaemia
  3. Inadequate NAD for fatty acid oxidation - increased synthesis of triacylglycerol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What impact does lactic acid build up have on the kidneys (eg. when lactate can’t be converted to pyruvate for lack of NAD)

A

Lactate inhibits excretion of uric acid becasue they use the same mechanism. So if there is accumulation of uric acid, there can be appearance of gout.

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

How is gout associated with alcohol oxidation?

A

Alcohol oxidation necessitates 2 enzymes: alcohol DH and aldehyde DH. Both these enzymes use NAD that they convert to NADH. But by using NAD they deplete the store needed to convert lactate into pyruvate. So lactate will accumulate. But lactate and uric acid use the same mechanism to be excreted by the kidney, so the excess lactate will block uric acid excretion. So there is build up of uric acid which could form cristals (monosodium urate) which deposit especially in big toe joint causing gout.

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

How does alcohol oxidation cause hypoglycaemia?

A

alcohol oxidation will reduce the NAD/NADH ratio, as the 2 enzymes involved in alcohol metabolism (alcohol DH and acetaldehyde DH) use NAD. Therefore, if there is excessive alcohol consumption, NAD stocks will be depleted, and inadequate NAD is available for glycerol metabolism and therefore there will be a deficit in gluconeogenesis causing hypoglycaemia.

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

What is disulfiram?

A

It is a drug given to wncourage alcohol addicts not to drink.

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

How does disulfiram work?

A

Disulfiram discourages from alcohol consumption as it increases the “hangover” feeling. Hangover feeling is caused by acetaldehyde, and by inhibiting aldehyde dehydrogenase, acetaldehyde will build up, therefore increasing “hangover” symptoms.
So basically disulfiram is an inhibitor of aldehyde DH.

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

What is oxidative stress?

A

Oxidative stress is an imbalance between cell damage (caused by reactive oxygen species and reactive nitrogen species) and cell defences (antioxidants).
It results in cell damage.

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

Which diseases are examples involving oxidative stress? (give 4)

A
  • multiple sclerosis
  • parkinson’s
  • pancreatitis
  • cancer
  • ischaemia/reperfusion injury
  • COPD
  • rhumatoid arthritis
  • Alzheimer’s
  • Crohn’s
  • CV disease
    So cellular damage caused by ROS & RNS is a significant component in a wide range of disease states
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are free radicals?

A

A free radical is an atom or molecule that contains one or more unpaired electrons and is capable of independent (“free”) existence.
These species will therefore want to steal an electron form another molecule in order to stabilise.
Therefore these free radicals are VERY REACTIVE. Reaction of a radical with a molecule typically generates a second radical thereby propagating damage! = chain reaction

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

How are free radicals denoted?

A

With a superscript dot after the atomical “name”

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

Which is the most reactive and damaging free radical that reacts with anything?

A

Hydroxyl radical, ie. OH⚫️

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

Which are the two RNS

reactive nitrogen species (one isnt technically speaking but it is a powerful oxidant that causes cellular damage)

A
  1. Nitric oxide NO⚫️

2. Peroxynitrite ONOO-

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

How is the RNS peroxynitrite produced?

A

Supoeroxide O2⚫️ can react with nitric oxide NO⚫️ to produce peroxynitrite ONOO-

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

How is superoxide produced?

A

By adding an electron to molecular oxygen O2 (normally has 2 freeeelctorms so happy, but if add on, then only 1 free, and unhalpy)

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

Which free radical can react with anything thus is very damaging?

A

Hydroxyl radical OH⚫️

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

Which two types of damage can ROS casue to DNA.

A
  1. ROS reacts with base - the midified base can lead to misoairing and mutation
  2. ROS reacts with sugar (ribose or deoxyribose) - can cause strand break and mutation on repair
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the link between reactive oxygen species and cancer?

A

ROS and react with DNA bases or sugars thus causing mispairing thus mutation or mutation on repair

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

With which 2 elements of a protein can ROS interact and therefore cause damage?

A
  1. Backbone - causing protein fragmentation

2. Sidechain - therefore changing an amino acid

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

A change in protein structure due to ROS can have which 3 consequences?

A
  1. Protein degradation
  2. Loss of function
  3. Gain of function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the link between ROS and disulphide bond formation?

A

If a ROS steals an electron from a cysteine residue, then this might cause inappropriate disulphide bond formation between cysteine residues.

  • misfolding
  • crosslinking
  • function disruption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Between which groups of which amino acid residues do disulphide bonds form?

A

disulphide bonds form between thiol groups of cysteine residues.

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

How do ROS damage lipids?

A

free radicals can extract hydrogen atom from a polyunsaturated fatty acid in membrane lipid.
A lipid radical is formed, which can then react with ixygen to form a lipid peroxyl radical.
a CHAIN REACTION occurs as lipid peroxyl radical extracts hydrogen from nearby fatty acid, etc.
=> hydrophobic environment of bilayer is disruoted and membrane integrity fails.

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

Give 3 sources of endogenous biological oxidants?

A
  1. Electron transport chain
  2. Nitric oxide synthases
  3. NADPH oxidases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How is the electron transport chain a source of ROS?

A

NADH and FADH2 supply electrons from metabolic substrates to the complexes of the electron transprot chain in the internal mitochondrial membrane.
e- pass along ETC and reduce oxygen to form H2O at the IVth complex.
BUT OCCASIONALLY, electron can accidently ESCAPE the chain and react with dissolved O2 to form superoxide,

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

What are nitric oxide synthases NOS?

A

NOS produces citrulline form arginine and releases NO Nitric Oxide.
There are 3 types of NOS, we just remember that they are a source of endogenous biological oxidants.

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

NO is involved in biological functions such as… (3)

A
  1. Signalling molecule
  2. Neurotransmission
  3. S-nitrosylation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is a respiatory burst?

A

It is rapid release of superoxide and H2O2 from phagocytic cells (eg. neutrophils and monocytes).
They are produced by NADPH oxidase (ie. source of endogenous oxidants).
- NADPH is a membrane bound compex in phagocyte membrane that oxidyses NADPH into NADP and transfers electron to O2, creating O2⚫️. This DELIBERATE production of superoxide can be converted into hydrogen peroxyde and then myeloperoxidase converts it into BLEACH.
- bleach = hypochlorite!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

In which cotnedt are ROS produced deliberately by the body, and by which cells?

A

Phagocytes produce ROS deliberately for their antimicrobial power.

  • hydrogen peroxide H2O2 can be converted into BLEACH by myeloperoxidase
  • superoxide can be combined with nitric oxide to make peroxynitrite.

Hypochlortie (bleach) and peroxynitrite are both powerful antibacterials!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What does a genetic defect in NADPH ixdase compelx cause?

A

enhanced susceptibility to bacterial infections.
Why? Because NADPH oxidase is important in phagocyte membranes to produce superoxide and H2O2 for antimicrobial actions.
- atypical infections
- pneumonia
- abcesses
- impetigo
- cellulitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Which 4 types of compound defend us against ROS and RNS.

A
  1. Superoxide dismutase SOD
  2. Catalase
  3. Glutathione
  4. Free radical scavengers like Vitamins E and C
42
Q

Why do superoxide dismutase and catalase have to work together?

A

Because SOD converts superoxide OH- to hydrogen peroxide H2O2 and oxygen. But H2O2 is still a ROS.
So now need catalase to convert H2O2 into water and oxygen.

43
Q

Why is catalase an impotant defense enzyme against ROS.

A

Because it will convert H2O2 (hydrogen peroxide) into H20 and water.
It is a widespread enzyme, important in immune cells to protect against oxidative burst.

44
Q

Decline in which defense mechanism against ROS could explain grey hair?

A

A decline in catalase in hair follicules, which normally converts H2O2 (hydrogen peroxide) into water and oxygen, could explain grey hair.
=> hair is literally bleaching itself from the inside!!

45
Q

What is glutathione?

A

It is a cellular defense against ROS.

  • tripeptide synthesised by body to protect against oxidative stress
  • glutathione peroxidase requires selenium
  • exists in a reduced form and an oxidised form
  • glutathione works by giving an electron to H2O2 therefore producing H2O. It is willing to give e- and will then simply form a disulphide bond between its cysteine residues (oxidised form)
46
Q

Give the name of the defense molecule that is willing to give away an electron from its cysteine residue to protect from H2O2 (hydrogen peroxide) and will then form a disulphide bond.

A

Glutathione

47
Q

Selenium is an essential element for which defense mechanism against ROS?

A

glutathione

48
Q

What does glutathione reductase do?

A

It catalyses the reduction of GSSG back to 2GSH (= recycling) by transfering electrons from NADPH to NADP. Therefore NADPH that comes from the pentose pathway is essential! If no NADPH, then no recycling of glutathione (back to its reduced for, that can give away electon to H2O2) and so no protection against damage!

49
Q

Which is the rate limiting enzyme of the pentose pathway?

A

Glucose-6P DH (dehydrogenase)

50
Q

What is the substrate for the oentose pathway?

A

Glucose-6-phosphate

51
Q

What are the 2 important products of the pentose pathway? (1 actual end product, other is by-product)

A
  1. C5 ribose sugars for nucleotide and DNA/RNA synthesis

2. NADPH essential for maintaining pool of reduced glutathione (the form that is willing to give electron to H2O2)

52
Q

How do vitamin A and E work to defend from cellular damage by ROS?

A

They are called free radical scavengers.
They reduce free radical damage by donating hydrogen atom and its electron to free radicals in a NONENZYMATIC reaction.
- Vitamin E is a lipid soluble antioxidant.
- Vitamin E gives the free lipid radical an electron.
- Vitamin C is water soluble and will reduce Vitamin E back to its “pre-defense” reduced form.

53
Q

What is galactosaemia?

A

It is a rare genetic metabolic disorder that affects an individual’s ability to metabolize the sugar galactose properly. Galactosemia follows an autosomal recessive mode of inheritance that confers a deficiency in an enzyme responsible for adequate galactose degradation.

54
Q

Which are the 2 types of galactosaemia?

A

Type 1 = uridyl transferase deficiency
Type 2 = galactokinase deficiency
Type 3= UDP-gaalctose epimerase

55
Q

Which symptom is common to all types of galactosaemia?

A

Cataract

56
Q

Which tyoe of galactosaemia is the most severe?

A

Type 3. UDO-gaalctose epimerase deficiency.. Ineed even a galactose-free diet will not be abke to save these patients.

57
Q

Which is the most mild type of galactosaemia?

A

Type 2, galactokinase deficiency. The only symptom they will have is cataract.

58
Q

What is type 1 galactosaemia?

A

It is a deficiency in Uridyl transferase enzyme that converts galactose 1P into glucose 1P.
These patients will have accumulation of galactose-1P in tissues such as liver, kidneys, GIT and brain damage.
The treatment is simply a galactose free diet, and they will be fine.

59
Q

What is type 2 galactosaemia?

A

It is a deficiency in galactokinase.
These patients will then have build up of galactose. Increased levels of galactose activate aldose reductase which produces galactitol from galactose.
But aldose reductase uses NADPH from this conversion, therefore compromising the stock of NADPH used to protect against ROS damage.
Kndeed NADPH is essential to reduce glutathione back to its form that is willing to give electron to H2O2 (hydrogen peroxide)

60
Q

Why do cataract occur in people with galactosaemia?

A

Because all types of gaalctosaemia induce build up of gaalctose. Increased levels of galactose activate aldose reductase.
Aldose reductase uses NADPH to convert galactose into galatitol.
So aldose reductase depletes stock of NADPH.
The defenses against ROS are compromised.
Crystallin protein of the eye lens is denatured by ROS.
= cataract

61
Q

How can one discriminate between type 1 and 3 of galactosaemia?

A

Type 1 will be helped by galactose-free diet, but type 3 will develop other problems due to lack of galactose that they cant

62
Q

What is G6PDH deficiency?

A

It is a deficiency in the enzyme Glucose-6-phosphate dehydrogenase.
It is an enzyme of the pentose pathway.
Decreased amount of G6PDH activity limits amounts of NADPH.
Indeed, G6PDH converts glucose 6P into 6-phosphogluconate, transferring H to NADP, thus creating NADPH.
And NADPH will be used to reduce glutathione GSSG back to its form able to defend against H2O2 (hydrogen peroxide), said GSH form.

63
Q

What are Heinz bodies?

A

They are aggregates of cross-linked haemoglobin that are seen within red blood cells. They resukt form precipitated haemoglobin.
They bind to cell membrane and alter rigidity.
Zhey induce increased mechanicla stress when cells squeeze thriugh small capillaries.
The spleen removes bound Heinz bodies resulting in blister cells.
They are a clinical sign of G6PDH deficiency!

64
Q

What is a typical clinical signof G6PDH?

A

Heinz bodies in red blood cells!They result form damaged haemoglobin proteins that aggregate.

65
Q

At prescribed dosage, paracetamol can be safely metabolised by conjugation with … or …

A

a) Glucuronide

b) Sulphate

66
Q

What is the molecular name for paravetamol?

A

acetaminophen

67
Q

Which toxic metabolite accumulates if high levels of paracetamol are taken?

A

NAPQI

68
Q

Waht us the antidote to paracetamol OD.

A

Acetylcysteine

69
Q

How does the oxidative damage occur from paracetamol OD?

A

NAPQI accumulates. it is a toxic metabolite of paracetamol.

  1. NAPQI causes direct liver damage
  2. The liver tries to compensate by using glutathione. But this depletes the stocks, and so we have less protection against oxidative damage.
    - lipid peroxidation
    - damage to proteins
    - damage to DNA
70
Q

What is creatinine?

A

Breakdown product of creatine and creatine phosphate in muscle.
It is produced at a constant rate depending on muscle mass.
Filtered into urine via the kidneys.
Creatinine urine excretion over 24 hours is proportional to muscle mass! for this reason it is a useful CLINICAL MARKER. It provides an estimate of muscle mass!
Also commonly used as an indicator of renal function (raised levels if nephron damage)

71
Q

Creatinine is a useful clinical marke rof what?

A

Muscle mass! as it is found in urine proportionately to muscle mass.
Indicator of renal function - raised on damage to nephrons.

72
Q

What is the “nitrogen balance”?

A

The input and output of nitrogen are usually equal. Ie. there is no change in total body protein, this is the nirmal state in an adult.

73
Q

What does a positive nitrogen balance indicate?

A

Intake>output
So an increase in total body protein.
Thus is normal in growth, and lregnancy or in adults recovering from malnutrition.

74
Q

In which cases can a positive nitrogen balance be normal?

A
  1. Pregnancy
  2. Growth
  3. Adult recovering from malnutrition
75
Q

What does a negative nitrogen balance indicate?

A

Net loss of body protein

76
Q

Are there physiological situations in which a negative nitrogen balance observed?

A

No! a negative nitrogen balance is never nirmal!

77
Q

In which cases does one see a negative nitrogen balance?

A
  • trauma
  • infection
  • malnutrition
78
Q

What oercentage of protein is nitrogen?

A

16%

79
Q

Which are the two constituents of a free amino acid?

A
  1. Carbon skeleton - potential energy

2. Amino group

80
Q

Amino acids can potentially be a siurce of energy. Which two pathways will amino acids follow to give energy?

A
  1. Glucogenic - gluconeogenesis

2. Ketogenic

81
Q

Under which form is the amino group of an amino acid broken diwn for energy excreted?

A

Amino groups are transformed into urea and excreted in urine.

82
Q

Give an example of glucogenic amino acids

A 
alanine
cysteine
glycine
serine
aspartate
asparagnie
arginine
proline
histidine
glutamine
methionine 
valine
glutamate

All aas starting with an A are glucogenic

83
Q

Give an example of a ketogenic amino acid.

A

Lysine
Leucine
All aas that start with an L are ketogenic

84
Q

Give an example of an amino acid that can be both keto- or glucogenic

A 
Threonine
Tryptophan
Tyrosine
Phenylalanine
Isoleucine

All aas starting with a T are both gluco and ketogenic

85
Q

What is the effect of insulin or growth hormone on protein synthesis?

A

Increases protein synthesis

86
Q

What is the effect of insulin and growth hormone on protein degradation?

A

Insulin and growth hormone decrease protein degradation

87
Q

What effect do glucocorticosteroids (cortisol) have in protein synthesis?

A

Glucocorticosteroids decrease protein synthesis.

88
Q

What effect do glucocorticosteroids have on protein degradation?

A

Glucocorticosteroids increase protein degradation.

89
Q

In which disease can excessive protein breakdown occur?

A

In cushings syndrome (excessive cortisol). this will weaken skin structure leading to striae formation.

90
Q

Which are the 9 essential amino acids?

A 
Isoleucine
Histidine
Threonine
Lysine
Leucine
Methionine
Phenylalanine
Tryptophan
Valnie
91
Q

Why is protein of animal origin considered to be “high quality”?

A

Because they contain all essential amino acids

92
Q

Why are proteins of plant origin generally considered “lower quality”?

A

because most of them are deficient in one or more essential amino acids.

93
Q

Which amino acid is essential for glutathione production? (and so for protection against oxidative stress)

A

Cysteine!

94
Q

Tyrosine is an important amino acid for the synthesis of which 3 products?

A
  1. Catecholamines
  2. Melanin
  3. Thyroid hormones
95
Q

Which two main pathways facilitate removal of nitrogen from amino acids?

A
  1. Transamination
  2. Demanination
    need to understand the distinction!
  • transamination is the exchange of amine group of amino acid with the O of a keto acid. This produces a different amino acid, typically glutamate or aspartate. This requires an aminotransferase, which in turn requires the coenzyme pyridoxal phosphate which is a Vitamin B6 derivative.
96
Q

Which two key aminotransferases are routinely measured as part of tion tests?

A
  1. ALT - alanine aminotransferase, it converts alanine to glutamate
  2. AST - it converts glutamate to aspartate
97
Q

In which clinical situation will AST and ALT be particularly high?

A
  1. Viral hepatitis
  2. Autoimmune liver disease
  3. Toxic injury

= conditions that cause extensive cellular necrosis

98
Q

What is deamination?

A

liberates amino group of a,ino acids as free ammonia.
Can ONLY occur where the urea cycle is able to run, so in the liver and kidney! otherwise would have accumualtion of ammonia.
- also important in deamination of dietary D-amino acids. They are those found in plants and microorganisms.

99
Q

What is ammonia?

A

Ammonia occurs from amino acid breakdown. It is very toxic and must be removed. It is ultimately converted to urea or excreted directly in urine.

100
Q

Which 3 enzymes can deaminate amino acids?

A
  1. Amino acid oxidases
  2. Glutaminase
  3. Glutamate dehydrogenase
101
Q

4 characteristics of urea?

A
  1. High nitrogen content
  2. Non-toxic
  3. Extremely water soluble
  4. Chemically inert in humans (bacteria can break it down to release NH3)
  5. Most urea is excreted in urine via the kidneys
  6. Also performs useful osmotic role in kidney tubules

MEH (4 decks)

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