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Biochemistry > Vitamins > Flashcards

Vitamins Flashcards

1
Q

What is a vitamin?

What are these?

A

Act as coenzymes or cofactors in enzyme catalysed reactions

Any non-protein substance required by a protein for a biological activity

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2
Q

What are the 2 classes of vitamins?

A

Water soluble

Fat soluble

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3
Q

What are the 9 water soluble vitamins?

A 
B1
B2
B6
B12
C
Choline
Folates
Niacin 
Pantothenic acid
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4
Q

What are the 4 fat soluble vitamins?

A

A
D
E
K

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5
Q

What is vitamin B1 also known as?

Where is it found?

A

Thiamine

> liver
fresh veg
husk of cereal grains e.g. rice

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6
Q

What is the name of the disease caused by vitamin B1 deficiency?

Where is this prevalent?

A

Beriberi

Communities that don’t eat husk of cereal grain

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7
Q

What is the active component in B1/thiamine?

What is this required by?

A

Thiamine pyrophosphate OR diphosphate

Pyruvate dehydrogenase

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8
Q

What is pyruvate dehydrogenase used for?

Give the word equation

A 
Converting Pyruvate (from glycolysis)
into Acetyl CoA

Pyruvate + CoASH + NAD+
–> Acetyl CoA + CO2 + NADH

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9
Q

Where does Acetyl CoA go?

Where is this ATP required most?

A

To the TCA/ Kreb’s cycle
to produce ATP

Muscles
Nerves

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10
Q

What is thiamine generally required as?

A

A cofactor in oxidative decarboxylation reactions

e.g. important in ATP production

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11
Q

What are the features of pyruvate dehydrogenase?

A

> located in mitochondria
links glycolysis & citric acid cycle
multi-enzyme complex w/ 3 subunits

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12
Q

What are the 3 subunits of pyruvate dehydrogenase?

A

> Pyruvate dehydrogenase

> Dihydrolipoyl transacetylase

> Dihydrolipoyl dehydrogenase

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13
Q

What is the cofactor for pyruvate dehydrogenase?

A

Thiamine pyrophosphate

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14
Q

What is the cofactor for Dihydrolipoyl transacetylase?

A

Lipoate

Coenzyme A

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15
Q

What is the cofactor for Dihydrolipoyl dehydrogenase?

A

FAD

NAD+

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16
Q

What does NAD stand for?

A

Nicotinamide adenine dinucleotide

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17
Q

Which tissues are most affected by Beriberi?

A

Those w/ high ATP demand

- muscle & nerve

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18
Q

What are the 2 types of beriberi?

What are the different symptoms?

A

Wet
- oedema & heart enlargement
(eventual heart failure)

Dry
- neuropathies

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19
Q

What is neuropathies?

A

Any disease affecting peripheral nerves causing weakness & numbness

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20
Q

What is Wernicke’s encephalopathy?

A

Any disease affecting the brain

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21
Q

What are the 3 characteristics of Wernicke’s encephalopathy?

A 
> nystagmus
= rapid eye movements side to side OR up & down 
> ophthalmoplegia
= paralysis of eye muscles
> ataxia
= unsteady gait/shaky movements
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22
Q

Who can get beriberi?

A

> alcoholics (w/ poor diet)

> communities subsisting on polished rice

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23
Q

What are the 5 common symptoms of beriberi?

A 
> parasthesia 
= pins & needles
> enlarged heart 
> wrist & foot drop
> muscle weakness & atrophy 
> digestive disturbances
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24
Q

What causes an enlarged heart in those with beriberi?

A

Decrease in ATP
–> reduction in blood vessel size
–> vasodilation
= reduced blood pressure & resistance in vessels

–> heart has to pump harder to get blood around vascular tubes
= heart gets bigger

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25
Q

What are the sources of niacin?

A

Liver
Legumes
Lean meats
Cereals

26
Q

What does Niacin form part of?

When is this involved in gluconeogenesis?

A

NAD

Lactate + NAD+ –> Pyruvate + NADH

(via lactate dehydrogenase)

27
Q

What is the deficiency in niacin known as?

A

Pellagra

28
Q

Where is pellagra endemic?

A

Remote areas

- green veg, fruit & animal protein are difficult to obtain

29
Q

How was pellagra reduced in Egypt?

A

Replacing maize w/ wheat

in maize nicotinic acid is bound tightly

30
Q

How was pellagra reduced in Mexico?

A

Washing maize w/ limewater

converts bound nicotinic acid –> free nicotinic acid

31
Q

What is nixtamalisation?

A

Washing maize w/ limewater

32
Q

What are the 4 Ds that pellagra is categorised by?

A

Dermatitis
Diarrhoea
Dementia
Death

33
Q

What is dermatitis?

A

An inflammatory condition of the skin cause by an outside agent

34
Q

What is dermatitis caused by?

A

A decrease in production of urocanic acid

- produced in body & acts as sunblock

35
Q

What are the different locations for dermatitis?

A 
Face = butterfly rash 
Hands = gauntlet 
Feet = boot
Between anus & urethra 
= perineal lesions
36
Q

What is B12 also known as?

A

Cobalamin

contains cobalt

37
Q

What are the sources of B12?

A

NOT plants

Fish
Meat
Poultry

38
Q

What does B12 absorption require?

A

GIF = gastric intrinsic factor

  • a glycoprotein
  • produced by parietal cells of stomach (also produce acid)
  • mw = 50Kda
39
Q

Why are B12 deficiencies so rare?

A

Body only requires v low concs

40
Q

How does B12 bind to GIF?

A

As a complex (tetramer)

- 2 molecules of GIF bind to 2 molecules of B12

41
Q

What does stomach acid do to food?

A

Helps to release nutrients via hydrolysis

42
Q

How is B12 absorbed?

A

GIF-B12 complex binds to brush border of absorptive cells in the intestine

–> binds to transcobalamin + is transported to 2 main tissues:
bone marrow
nerves

43
Q

What can cause B12 deficiencies?

A

Barrett’s metaplasia

44
Q

Describe what happens in Barrett’s metaplasia

A 
Acid reflux
--> acid moves up into oesophagus from stomach
= damages oesophagus 
--> cells replaced by intestinal cells
= predisposes to cancer
45
Q

What is the treatment of Barrett’s metaplasia?

How can this cause a B12 deficiency?

A

Achlorhydria = drug that reduces acid production

Reduced GIF production

46
Q

What are the 2 main symptoms of B12 deficiencies?

A 
Megaloblastic anaemia
(Pernicious anaemia is the type of anaemia caused by B12 deficiency)

Neurological disorders e.g. paraesthesia

47
Q

What is megaloblastic anaemia?

What are the symptoms?

A

V large red blood cells + decrease in the number of those cells

Pallor
Fatigue
Breathlessness

48
Q

How is pernicious anaemia different to megaloblastic?

What is it associated with?

A

Can’t be treated w/ iron supplements

Chronic diseases that cause diarrhoea
e.g. tropical sprue, cholera, celiac
= prevents B12 absorption

49
Q

What is Vitamin A also known as?

What is it found in?

When is it important?

A

Retinoic acid

Carrots

In pregnancy - for brain formation

50
Q

Vit A is a teratogen. What is this?

Give examples

A

An agent or factor which causes malformation of an embryo

e.g. thalidomide, alcohol

51
Q

What was thalidomide used to treat?

How did it affect newborn babies?

A

Morning sickness + sleeping trouble

Abnormal limb development
- usually absence of upper limb = phocomelia

52
Q

What can alcohol cause when drank by pregnant women?

A

Foetal alcohol syndrome

= growth + mental retardation

53
Q

What are the physical defects due to foetal alcohol syndrome?

A

> flat bridge of nose
epicanthal folds
flat philtre
rail road ears

54
Q

What is vitamin A important for?

A

Visual pigments
- especially rhodopsin
(needed for low-level light)

55
Q

Why is the anaemia in cobalamin deficiency referred to as megaloblastic anaemia?

A

There’re abnormally large numbers of megaloblasts in the blood

56
Q

What are megaloblasts?

A

Large, nucleated immature progenitors

57
Q

What are progenitors?

A

Cells that have a tendency to differentiate into a specific type of cell

58
Q

What are the anaemia + neurological symptoms of B12 deficiency due to?

A

The lack of methionine

an amino acid

59
Q

Why do megaloblasts accumulate in the blood on the anaemic?

A

DNA synthesis + protein synthesis are required to convert megaloblasts –> erythrocytes

Cobalamin is a cofactor of methionine synthase which is involved in DNA + protein synthesis

Not enough Cobalamin –> not enough DNA + protein for cell differentiation

60
Q

How do erythrocytes form from bone marrow?

A

Bone marrow

  • > stem cells
  • > megaloblasts
  • > erythroblasts
  • > erythrocytes
61
Q

What are the 2 main forms of vitamin A?

A

Retinol

  • can be converted into retinoic acid
  • found in liver & eggs

Retinal (provitamin A)

  • can be converted in to retinol
  • found in carrots & spinach

Biochemistry (14 decks)

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