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Biomolecules of Life > Week 8: Vitamins and metabolic energy > Flashcards

Week 8: Vitamins and metabolic energy Flashcards

1
Q

What are the classes of vitamins?

A

A, B, C, D, E and K

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2
Q

What are the types of B vitamins?

A

(1,2,3,5,6,7,9,12)

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3
Q

What is B2 also known as?

A

Riboflavin

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4
Q

What is B7?

A

Biotin

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5
Q

What are the two classifications of vitamins?

A

Water-soluble or lipid soluble

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6
Q

What vitamins are excreted via the urine?

A

B

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7
Q

What is an apoenzyme

A

Enzyme without its coenzyme

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8
Q

What vitamins are water soluble?

A
  • Vitamin C and B
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9
Q

Where are lipid soluble vitamins stored?

A

In the liver and adipose tissue

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10
Q

What is carotene?

A

The precursor (pro-vitamin) of vitamin A

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11
Q

How is carotene converted to vitamin A

A

β-carotene 15,15’-dioxygenase

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12
Q

What are the roles of vitamins?

A

-Converted into co-enzymes
-Act as hormones
-Act as antioxidants

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13
Q

What can vitamin C (ascorbic acid) act as?

A

A metal co-factor , it can move electrons. Hydroxylation of collagen – returns Fe to reduced state

It is present in cytochrome a & c of respiratory chain

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14
Q

What is the role of vitamin C in collagen production?

A

Vitamin C’s role is to help bind the Fe3 state to the oxygen and return to the reduced Fe4 state

If deficient the Fe 3 state cannot be reduced so no hydroxylation of collagen

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15
Q

What is the role of vitamin C in collagen production?

A

Vitamin C’s role is to help bind the Fe3 state to the oxygen and return to the reduced Fe4 state

If deficient the Fe 3 state cannot be reduced so no hydroxylation of collagen

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16
Q

What sources of food is B2 found in?

A

Eggs, meat, dairy and vegetables

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17
Q

What vitamin is present in the FAD structure?

A

B2

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18
Q

What binds to Protoporphyrin IX?

A

FAD

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19
Q

What vitamins are commonly known as the hormone vitamins?

A

Vitamin D and A

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20
Q

What type of hormone is vitamin D3 and what is its biologically active form

A

steroid hormone- calcitrol

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21
Q

What are the two routes that cells obtain energy from?

A

-Phototrophs
-Chemotrophs

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22
Q

What are the two types of metabolic pathways

A

Anabolic and catabolic

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23
Q

What are the two key characteristics of metabolic pathways

A
  • They are irreversible
    • The reaction must be highly favoured thermodynamically so that you do not get both products and reactants that will stop the flow of reaction pathways
  • They are very specific
    • The reactions must give only one particular product from the reactants. This allow regulation by enzymes etc
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24
Q

What does it mean if the value is closer to 1, less than 1 or more than 1

A

1= equal concentrations of reactants and products
>1= irreversible forward reaction
<1= irreversible reverse reaction

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25
Q

What causes a spontaneous reaction?

A

Reactions that give out energy + reactions that increase disorder

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26
Q

Why do reactions that are exergonic spontaneous?

A

Because the products they make are of lower energy, as they make many chemical bonds (the internal energy changes). We can measure and determine changes in internal energy or enthalpy (∆H) as a reaction proceeds

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27
Q

Why do reactions that increase entropy cause a spontaneous reaction?

A

∆G = ∆H - T∆S, because the gibbs free energy is more likely to be negative

28
Q

What is an exergonic reaction and an endergonic reaction?

A
  • Exergonic = When a reaction proceeds in a release of free energy
  • Endergonic = if the free energy of a reaction is negative
29
Q

Are catabolic or anabolic reactions more likely to be spontaneous?

A

Catabolic
- They are more likely to be spontaneous as you are breaking up molecules which leads to an increase in entropy.
- But you start with a very stable molecule, so the activation energy is high, which means the reaction may be reversible

30
Q

What is the BMR?

A

Basal metabolic rate
-Amount of energy the body needs to maintain normal functions such as breathing, steady heart, blood circulation, grow and repair of cells and tissue, and maintain healthy hormone levels.

31
Q

What is thermogenesis?

A

Describes the thermic effect of food. These include eating, swallowing, digest (chemically and mechanically breaking down of food as it moves along the GIT),

32
Q

What are activated carriers?

A
  • They are small molecules responsible for the storage of energy and electron transfer for energetically unfavourable reactions
  • These energies are either stored in bonds (bond formation) or as high energy electrons (released via oxidation reaction)
33
Q

In what form is energy stored in activated carriers?

A
  • These energies are either stored in bonds (bond formation) or as high energy electrons (released via oxidation reaction)
34
Q

Give an example of an activated carrier

A

Phosphoryl transfer, ATP acts as the activated carrier for the phosphoryl group

35
Q

What is the role of NAD

A

Nicotinamide adenine dinucleotide transfers electrons in aerobic respiration. Reduced form NADH

36
Q

What is the reactive group in coenzyme A?

A

The thioester group (C-S)

37
Q

What are the two major aspects of metabolism using activated carriers?

A
  • The metabolic reactions react slowly in absence of a catalyst
  • A wide range of metabolic tasks are accomplished by a small set of carriers
38
Q

What are the bonds called in ATP?

A

The triphosphate unit contains two phosphoanhydride bonds.

39
Q

What are the 6 classes of metabolic reactions?

A
  • Oxidation-reduction reactions
    -Ligation reactions
    -Isomerization reaction
  • Group transfer reactions
    -Hydrolytic reactions
    -Addition or removal of functional groups to form double bonds
40
Q

Give an example of a reaction for both FAD and NAD+

A

Succinate + FAD -> Fumarate + FADH2
Malate + NAD+ -> Oxaloacetate + NADH + H+

41
Q

Give an example of a ligand reaction

A

The formation of C-C bonds in the formation of oxaloacetate from pyruvate

42
Q

Give an example of an isomerization reaction

A

Conversion of citrate to isocitrate

43
Q

Name 3 ways to regulate metabolism

A

By controlling:
- Amount of enzyme
-Catalytic activity
- Accessibility of substrate

44
Q

What are the 3 stages in the generation of energy from food?

A

Stage 1: large molecules in food are broken down into smaller units through a process of digestion

Stage 2: these numerous small molecules are degraded to a few simple units that play a central role in metabolism.

Stage 3: ATP is produced from the complete oxidation of the acetyl unit of acetyl CoA.

45
Q

What is the structure of haemoglobin

A

tetrameric protein with 2
identical alpha subunits and 2 identical beta
subunits
Structure has a α2β2 configuration
Each globin subunit contains a Haem (Heme)

46
Q

What does the haem group have?

A

Haem cofactor is a Tetrapyrrole ring
molecule in association with an Fe2+ ion

47
Q

What occurs when oxygen binds to haem group

A

Fe2+ lies outside plane of tetrapyrrole ring
On binding Fe2+ moves into plane of ring to become flat

A distal Histidine residue helps to stabilize the
bound O2 by forming a hydrogen bond

48
Q

What are the differences and similarities between the myoglobin and haemoglobin oxygen binding curve?

A
  • Myoglobin has the highest affinity (higher Km)
  • Both have the same Vmax (all oxygenated haemoglobin or myoglobin)
  • Haemoglobin has a S-shaped curve - which is characteristic to an allosteric binding protein. This is important for the unloading of the oxygen
  • Haemoglobin releases oxygen more readily
49
Q

What are the differences and similarities between the myoglobin and haemoglobin oxygen binding curve?

A
  • Myoglobin has the highest affinity (higher Km)
  • Both have the same Vmax (all oxygenated haemoglobin or myoglobin)
  • Haemoglobin has a S-shaped curve - which is characteristic to an allosteric binding protein. This is important for the unloading of the oxygen
  • Haemoglobin releases oxygen more readily
50
Q

Why does the myoglobin need to have a higher affinity for oxygen than haemoglobin?

A

Because in the muscle tissue the haemoglobin needs to release the oxygen to the myoglobin

51
Q

Why is haemoglobin a more efficient oxygen carrier?

A

Due to cooperative binding to O2 to Haemoglobin
- Binding of O2 Haem in one subunit increases affinity of O2 to others
Cooperativity also applies to O2 unloading

52
Q

What subunit changes in oxygen binding to haemoglobin?

A

O2 causes change in tertiary structure
α1β1 dimers rotate relative to α2β2 by 15°

53
Q

What is the deoxygenated state of haemoglobin called?

A

The Tense (T) state - low oxygen affinity

54
Q

What is the oxygenated state of haemoglobin called?

A
  • In R state O2 binding sites are open and are more able to bind O2
55
Q

What are the 2 models used to explain cooperative O2 binding?

A
  • Concerted model
  • Sequential model
56
Q

What is the difference between the concerted model and sequential model

A

In the concerted model all o2 bound forms either T and R states, whereas sequential model describes the idea that individual subunits shift. Allows neighbouring subunit to bind O2 with slightly higher affinity

57
Q

Does pure haemoglobin bind more or less strongly to O2 than haemoglobin in the blood?

A

Pure haemoglobin binds more strongly
- This is because when haemoglobin is in the blood it still needs to be able to release the oxygen
- Important that T-state must be stabilised or
Haemoglobin would never release O2

58
Q

What is 2,3 Bisphosphoglycerate (2,3 BPG)?

A

-An allosteric regulator
-2,3 BPG binds to T form and stabilises it, reduces the oxygen binding capacity. Stops the haemoglobin holding to the oxygen too tightly

59
Q

Does foetal haemoglobin have a high or low affinity for 2,3 BPG?

A

‼️Low affinity for 2,3 BPG, more haemoglobin in the relaxed state
Increased oxygen affinity compared to mother

60
Q

What is the Bohr effect?

A

Respiring tissues produce CO2, lower pH (from the carbonic acid and lactic acid breakdown) - more oxygen is needed- they decrease the oxygen affinity to haemoglobin

61
Q

What is the effect of CO2 and Increased pH

A

Tense state is stabilized

62
Q

How does a decreased pH affect the T state?

A

Stabilizes it by allowing formation of salt bridges within globin subunits
As the pH drops the proton binds onto the histidine ring (pKa of histidine is 6- pH), forms hydrogen bond and stabilizes it

63
Q

What are the 2 ways that CO2 can affect haemoglobin ?

A

Increased CO2 leads to decreased pH through
action of carbonic anhydrase
CO2 also directly effects quaternary structure of haemoglobin

64
Q

How does CO2 directly affect the quaternary structure of haemoglobin?

A

Reacting with amino termini to form negatively charged carbamate

Amino termini of subunits lie at αβ interface
Carbamate groups allow formation of salt bridges that stabilize T state

65
Q

What is the Haldane effect?

A

Reverse of the Bohr effect,

The more oxygenated the environment is the less binding affinity it has to bind with carbon dioxide

66
Q

What form of carbon dioxide is found the most in the blood?

A
  • In bicarbonate (around 70%)
  • 23% in carbaminohemoglobin
  • 7% Dissolved in solution
  • None in the carbonic acid state because it deprotonates to bicarbonate at physiological pH

Biomolecules of Life (1 decks)

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