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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
What are the sources of niacin?
Liver Legumes Lean meats Cereals
26
What does Niacin form part of? When is this involved in gluconeogenesis?
NAD Lactate + NAD+ --> Pyruvate + NADH (via lactate dehydrogenase)
27
What is the deficiency in niacin known as?
Pellagra
28
Where is pellagra endemic?
Remote areas | - green veg, fruit & animal protein are difficult to obtain
29
How was pellagra reduced in Egypt?
Replacing maize w/ wheat | in maize nicotinic acid is bound tightly
30
How was pellagra reduced in Mexico?
Washing maize w/ limewater | converts bound nicotinic acid --> free nicotinic acid
31
What is nixtamalisation?
Washing maize w/ limewater
32
What are the 4 Ds that pellagra is categorised by?
Dermatitis Diarrhoea Dementia Death
33
What is dermatitis?
An inflammatory condition of the skin cause by an outside agent
34
What is dermatitis caused by?
A decrease in production of urocanic acid | - produced in body & acts as sunblock
35
What are the different locations for dermatitis?
``` Face = butterfly rash Hands = gauntlet Feet = boot Between anus & urethra = perineal lesions ```
36
What is B12 also known as?
Cobalamin | contains cobalt
37
What are the sources of B12?
NOT plants Fish Meat Poultry
38
What does B12 absorption require?
GIF = gastric intrinsic factor - a glycoprotein - produced by parietal cells of stomach (also produce acid) - mw = 50Kda
39
Why are B12 deficiencies so rare?
Body only requires v low concs
40
How does B12 bind to GIF?
As a complex (tetramer) | - 2 molecules of GIF bind to 2 molecules of B12
41
What does stomach acid do to food?
Helps to release nutrients via hydrolysis
42
How is B12 absorbed?
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
What can cause B12 deficiencies?
Barrett's metaplasia
44
Describe what happens in Barrett's metaplasia
``` Acid reflux --> acid moves up into oesophagus from stomach = damages oesophagus --> cells replaced by intestinal cells = predisposes to cancer ```
45
What is the treatment of Barrett's metaplasia? How can this cause a B12 deficiency?
Achlorhydria = drug that reduces acid production Reduced GIF production
46
What are the 2 main symptoms of B12 deficiencies?
``` Megaloblastic anaemia (Pernicious anaemia is the type of anaemia caused by B12 deficiency) ``` Neurological disorders e.g. paraesthesia
47
What is megaloblastic anaemia? What are the symptoms?
V large red blood cells + decrease in the number of those cells Pallor Fatigue Breathlessness
48
How is pernicious anaemia different to megaloblastic? What is it associated with?
Can't be treated w/ iron supplements Chronic diseases that cause diarrhoea e.g. tropical sprue, cholera, celiac = prevents B12 absorption
49
What is Vitamin A also known as? What is it found in? When is it important?
Retinoic acid Carrots In pregnancy - for brain formation
50
Vit A is a teratogen. What is this? Give examples
An agent or factor which causes malformation of an embryo e.g. thalidomide, alcohol
51
What was thalidomide used to treat? How did it affect newborn babies?
Morning sickness + sleeping trouble Abnormal limb development - usually absence of upper limb = phocomelia
52
What can alcohol cause when drank by pregnant women?
Foetal alcohol syndrome | = growth + mental retardation
53
What are the physical defects due to foetal alcohol syndrome?
> flat bridge of nose > epicanthal folds > flat philtre > rail road ears
54
What is vitamin A important for?
Visual pigments - especially rhodopsin (needed for low-level light)
55
Why is the anaemia in cobalamin deficiency referred to as megaloblastic anaemia?
There're abnormally large numbers of megaloblasts in the blood
56
What are megaloblasts?
Large, nucleated immature progenitors
57
What are progenitors?
Cells that have a tendency to differentiate into a specific type of cell
58
What are the anaemia + neurological symptoms of B12 deficiency due to?
The lack of methionine | an amino acid
59
Why do megaloblasts accumulate in the blood on the anaemic?
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
How do erythrocytes form from bone marrow?
Bone marrow - > stem cells - > megaloblasts - > erythroblasts - > erythrocytes
61
What are the 2 main forms of vitamin 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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