Biochemistry intro 2 - Energy and thermodynamics Flashcards

1
Q

Name 4 examples of major classes of biomolecules and state their building blocks

A
  1. Peptides and proteins - building blocks are amino acids
  2. Lipids - building blocks are triglycerides, phospholipids, steroids
  3. Nucleic acids - building blocks are DNA and RNA
  4. Carbohydrates - building blocks are mono-, di- and polysaccharides
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2
Q

Name 5 functions of biomolecules and give some examples for each

A
  1. Information storage (such as DNA)
  2. Structural function (such as teeth, bones, cartilage)
  3. Energy generation (such as citric acid cycle, electron transport chain, glycolysis)
  4. Energy storage (such as ATP)
  5. Recognition/communication/specificity (such as receptors, hormones, enzymes)
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3
Q

How are disaccharides formed and why are they important?

A

Disaccharides are formed by covalent bonds between either carbon 1+4 or carbon 1+2. Disaccharides are important because they provide your body with a rapid source of energy because the oxygen atom linking the two monosaccharides is readily reduced to generate readily metabolised monosaccharides

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4
Q

What are polysaccharides?

A

These are chains of many monosaccharides such as glycogen or cellulose

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5
Q

What is meant by thermodynamics?

A

Thermodynamics is the biophysical discipline which deals with the question of whether a process is energetically favourable

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6
Q

Explain the first two laws of thermodynamics

A

The 1st law of thermodynamics: Energy is neither created nor destroyed - This means that when energy is converted from one form to another, the total energy before and after the conversion remains the same

The 2nd law of thermodynamics: When energy is converted from one form to another, some of that energy becomes unavailable to work - This means that no energy transformation is 100% efficient

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7
Q

What is meant by the term enthalpy?

A

A measure of change in heat content (ΔH)

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8
Q

What is meant by the term entropy?

A

A measure of change in disorder/randomness (ΔS). To impose order on a system, energy is required so unless energy is applied to a system, it will be randomly disordered

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9
Q

How do you calculate free energy change for reactions involving changes in thermodynamic quantities?

A

To calculate free energy change (ΔG) = ΔH - TΔS
So free energy change is ΔG = (energy of products) - (energy of reactants)
Where T is temperature in Kelvin

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10
Q

What are exergonic reactions?

A

Exergonic reactions (think of exothermic) are reactions in which the total free energy of the products is LESS than the total free energy of the reactants. Therefore, this means that ΔG will be NEGATIVE and so such reactions CAN occur spontaneously (doesn’t require energy to happen)

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11
Q

What are endergonic reactions?

A

Endergonic reactions (think of endothermic) are reactions in which the total free energy of the products is MORE than the total free energy of the reactants. Therefore, ΔG is positive and so such reactions CANNOT occur spontaneously (does require energy to happen)

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12
Q

What does ΔG°’ mean?

A

This is the symbol for the change in free energy under STANDARD CONDITIONS (in the body)

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13
Q

What is meant by standard conditions in biochemistry?

A
In biochemistry, standard conditions are:
• T = 298K
• 1 atmosphere of pressure
• 1M concentration of reactants
• pH = 7
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14
Q

What formula can be used to calculate ΔG for a given reaction (in equilibrium)?

A

ΔG = ΔG°’ + RTln([C][D]/[A][B])
Where R is the universal gas constant (8.3 JK-1mol-1)
and T is the absolute temperature (in degrees Kelvin)
The unit for this reaction is kJ/mol

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15
Q

True or False: The further towards completion the point of equilibrium is, the more free energy is released

A

True

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16
Q

What does it mean when ΔG values are near zero?

A

This means that the reaction is readily reversible and nor the products or the reactants are favoured - so the system is at equilibrium (the forward and backwards reactions are balanced)

17
Q

How do you calculate the equilibrium constant?

A

Equilibrium constant (Keq) = [C][D]/[A][B] which is equal to [Products]/[Reactants]

18
Q

How do many reactions occur within the body?

A

Many reactions within the body use the coupling process where an unfavourable reaction (one with a positive ΔG) is coupled with a very favourable reaction (one with a negative ΔG)

19
Q

What are anhydride bonds?

A

These are high energy bonds

20
Q

Explain what is meant by strain in relation to the structure of ATP

A

The negative charges close together in ATP put a strain on the molecule (known as electrostatic repulsion) which makes it less stable than ADP. Strain can be partially relieved by removing one or more phosphate groups from an ATP molecule

21
Q

Why is ATP constantly regenerated?

A

This is because cells do not store large amounts of ATP and also some cells, such as active muscle cells, use ATP at a high rate

22
Q

Metabolism is all the reactions taking place in the body. It is divided into two parts called…?

A
  1. Catabolism - The breaking down of complex molecules into smaller ones
  2. Anabolism - The synthesis of complex molecules out of smaller ones
23
Q

True or False: Reactions with large negative ΔG values are useful control points in metabolic pathways

A

True

24
Q

How are carbohydrates composed and how do they provide energy?

A

Carbohydrates are composed of carbon chains that are primarily linked to hydrogen and oxygen atoms. Their oxidation through metabolic pathways provides an important source of energy release

25
Q

What is the point in coupling processes?

A

Coupled reactions allow energetically unfavourable reactions to reach completion