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ESA 2 - MEH > 1. Energy Reactions In Cells > Flashcards

1. Energy Reactions In Cells Flashcards

1
Q

What is metabolism?

A

Set of processes which:

  • derive energy and raw materials from food stuffs
  • and use them to support repair, growth and activity of the body tissues
  • to support life.
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2
Q

What is the difference between catabolic and anabolic pathways?

A

Catabolism:

  • break down larger molecules into smaller ones - intermediary metabolites
  • OXIDATIVE: release large amounts of free energy as H atoms - reducing power

Anabolism:

  • synthesis of large cellular components from intermediary metabolites
  • REDUCTIVE: use energy (H atoms) released from catabolism - ATP
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3
Q

What do fuel molecules provide when they are catabolised? What are these products used for?

A
  1. Building block materials: sugars, amino acids, fatty acids
    - turnover of cell components (dynamic state)
    - cell growth and division
    - repair
  2. Organic precursors: acetyl CoA
    - interconversion of building block materials
  3. Biosynthetic reducing power: NADH, NADPH
  4. Energy for cell function: ATP (adenosine triphosphate)
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4
Q

What is energy?

A

Capacity to do work

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5
Q

What sort of cellular work is energy required for?

A
  1. Biosynthetic work (anabolism)
    - synthesis of cellular components
  2. Transport work (across membranes)
    - maintenance of ion gradients (Na+, K+, Ca2+)
    - nutrient uptake
  3. Specialised functions, e.g.
    - mechanical work: muscle contraction
    - electrical work: nervous impulse conduction
    - osmotic work: kidney
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6
Q

What are the different forms of energy and which form is utilised in cells?

A

Heat, light, mechanical, electrical, osmotic, chemical bond (used in cells)

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7
Q

Why can Man not use heat energy for work?

A

Is isothermal

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8
Q

What is the difference between exergonic and endergonic chemical reactions?

A

Exergonic

  • release energy (mostly catabolic reactions)
  • reaction is spontaneous

Endergonic

  • require energy input (mostly anabolic reactions)
  • reaction isn’t spontaneous
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9
Q

What does G stand for? What is deltaG?

A 
G = Gibbs free energy - is energy that can be used
DeltaG = change in G
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10
Q

What is the result of a positive or negative deltaG value for a reaction?

A

If deltaG is negative, reaction is spontaneous. If it is positive, reaction is not spontaneous as requires energy input.

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11
Q

What is the difference between oxidation and reduction reactions?

A

Oxidation = removal of electrons (e-) OR removal of H atoms (H+ + e-).

Reduction = gain of e- or H+.

(OIL RIG : oxidation is loss, reduction is gain)

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12
Q

What happens to the electrons and protons released when fuel molecules are oxidised?

A

Transferred to carrier molecules

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13
Q

Name the major H carrier molecules.

A

Oxidised form Reduced form

NAD+ NADH + H+
NADP+ NADPH + H+
FAD FADH2

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14
Q

How does the concentration of oxidised and reduced forms of H carrier molecules change within a cell and what is the consequence of this?

A

Total concentration is constant so there must be a cycle between oxidative and reductive processes.

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15
Q

What do NADH + H+ and NADPH act as carrier of ‘reducing power’ for?

A

ATP production and biosynthesis (respectively)

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16
Q

How are H carrier molecules converted to reduced form?

A

Adding 2 H atoms ( 1 H+ dissociates into solution for NAD(P)H but not FADH2)

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17
Q

What do H carrier molecules contain?

A

B Vitamin components , e.g. FAD+ contains vitamin riboflavin B2

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18
Q

How can energy released as reducing equivalents be used to drive energy-requiring activities?

A

Directly: e.g. Use of NADPH in biosynthesis

Indirectly: e.g. Mitochondrial system to couple NADH to the production of an intermediate ‘energy currency’ molecule - ATP

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19
Q

What is ATP composed of?

A

Adenine, ribose and triphosphate

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20
Q

How are ATP, ADP and AMP created and what are the deltaG changes associated with this?

A

ATP + H2O = ADP + Pi (deltaG o’ = -31 kJ.mole-1)

ADP + H2O = AMP + Pi (deltaG o’ = -31 kJ.mole-1)

ADP + Pi = ATP + H2O (deltaG o’ = +31 kJ.mole-1)

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21
Q

Which signals indicate high and low energy levels in cells, and what pathways do these signals activate?

A

High energy signals: activate anabolic pathways

  • ATP
  • NADH
  • NADPH
  • FADH2

Low energy signals: activate catabolic pathways

  • ADP, AMP
  • NAD+
  • NADP+
  • FAD
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22
Q

Which enzyme converts 2 ADP to ATP + AMP?

A

Adenylate kinase

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23
Q

Which molecule acts as a reserve of high energy stores that can be used immediately when ATP levels are high? Which enzyme mediates this storage?

A

Phosphate bond energy can be stored as phosphocreatine. Involves addition of phosphate (ATP to ADP) to creatine by creatine kinase.

24
Q

What is creatine kinase a marker for and why?

A

Myocardial infarction (1 CK isoform combination specific to heart muscle)

CK is released from cardiac myocytes when damaged, appears in blood a few hours later.

25
Q

What is the product of normal spontaneous breakdown of creatine and phosphocreatine? When is this produced?

A

Creatinine

Produced by spontaneous reaction at a constant rate, unless muscle is wasting.

26
Q

How is creatinine used as a clinical marker?

A

Creatinine excreted via kidneys.

  1. Excretion per 24hrs is proportional to muscle mass of individual - measure of muscle mass.
  2. Concentration in urine is a marker of urine dilution - can be used to estimate true urinary loss of many substances (e.g. Hormones in pregnancy) as excreted at constant rate.
27
Q

What are the 4 different types of pathways of metabolism?

A
  1. Oxidative pathways
    • convert food into energy.
  2. Biosynthetic pathways
    • produce basic building blocks for cells.
  3. Fuel storage and mobilisation pathways
    • allow fuel to be mobilised when we are not eating or need increased energy
  4. Detoxification pathways
    • remove toxins
28
Q

What is the official SI unit of food energy?

A

Kilojoule (kJ)

29
Q

What is a Kcal?

A

1 kcal = amount of energy needed to raise temperature of 1 kg of water by 1 degree Celsius.

1 kcal = 4.2 kJ

30
Q

How much food does one eat per year?

A

~ 500 kg

31
Q

What are the essential components of the diet?

A
  1. Carbohydrates - mostly supply energy
  2. Proteins - energy and amino acids
  3. Fat - energy and essential fatty acids
  4. Minerals - essential
  5. Vitamins - essential
  6. Fibre - necessary for normal GI function
  7. Water - maintains hydration
32
Q

What is the general formula of carbohydrates? Which groups do these molecules contain?

A
  • (CH2O)n
  • Contain:
    • aldehyde (-C=OH) or keto (-C=O) group
    • multiple -OH groups
33
Q

How are carbohydrates classified according to unit number? Give examples of each type.

A
  1. Monosaccharide - single sugar unit, e.g. Glucose
  2. Disaccharide - 2 units, e.g. Sucrose
  3. Oligosaccharide - 3-12 units, e.g. Dextrin
  4. Polysaccharides - 10-1000s units, e.g. Glycogen, starch, cellulose
34
Q

How many carbon atoms can monosaccharides have? What are these called?

A

3-9 carbon atoms

  • Triose sugar = 3 carbons
  • Pentose sugar = 5 carbons
  • Hexose sugar = 6 carbons
35
Q

How many C atoms does glucose have?

A

6

36
Q

Name the major dietary carbohydrates.

A
  1. Glucose (predominant sugar in human blood)
  2. Glycogen (glucose polymer, carbohydrate storage molecule in animals)
  3. Sucrose (table sugar, glucose-fructose disaccharide)
  4. Lactose (milk sugar, galactose-glucose disaccharide)
  5. Fructose (fruit sugar, monosaccharide)
  6. Maltose (glucose-glucose disaccharide)
  7. Starch (glucose polymer, carbohydrate storage molecule in plants)
37
Q

How are larger carbohydrates converted to monosaccharides in the body?

A

Digestion (enables absorption into the blood)

38
Q

What are proteins composed of?

A

Amino acids joined by peptide bonds to form linear chains

39
Q

What is the effect of digestion on protein?

A

Breaks protein into constituent amino acids which enter blood.

40
Q

How many amino acids are used for protein synthesis in the body? How many cannot be synthesised and must therefore be obtained from diet?

A
  • 20

- 9 essential amino acids

41
Q

Name the 9 essential amino acids.

A

If Learned This Huge List May Prove Truly Valuable

Isoleucine, Lysine, Threonine, Histidine, Leucine, Methionine, Phenylalanine, Tryptophan, Valine.

42
Q

What are conditionally essential amino acids?

A

Children and pregnant women have high rates of protein synthesis. Require dietary source of arginine, tyrosine and cysteine (as can’t synthesise enough to match growth).

43
Q

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

A

Most are deficient in 1 or more essential amino acids.

44
Q

What is fat?

A

Lipids composed of triacylglycerols = 3 fatty acids esterified to 1 glycerol.

3 forms: saturated (no double bond), unsaturated (-C=C-) and trans.

45
Q

Do fats yield more or less energy than carbs/proteins? Why?

A

Contain much less oxygen than carbs or proteins - more reduced so yield more energy when oxidised.

46
Q

Why are fats important dietary components?

A
  1. Required for absorption of fat-soluble vitamins (A, D, E & K) from the gut.
  2. Provide essential fatty acids, e.g. Linoleic and linolenic acids, which cannot be synthesised in body.
47
Q

Why are electrolytes important in the body? Name some examples.

A
  • Establish ion gradients across membranes and maintain water balance.
  • E.g. Sodium, potassium, chloride.
48
Q

How much water and electrolytes is given to someone on IV fluids (routine maintenance).

A
  • Water = 30 ml/kg/day

- Na+, K+, Cl- = 1 mol/kg/day each

49
Q

Why are minerals important in the body? Name some examples.

A
  1. Essential for structure (bones and teeth)
    • calcium and phosphorus
  2. Important signalling molecule
    • calcium
  3. Enzyme co-factors
    • iron, magnesium, manganese, cobalt, copper, zinc and molybdenum
  4. Haemoglobin component
    • iron
50
Q

What are the 2 main types of vitamin and how much do we require?

A
  • Fat or water soluble

- Micro- or milligram quantities

51
Q

Which diseases occur as a result of fat-soluble vitamin deficiencies?

A
  • VitA: xerophthalmia
  • VitD: rickets
  • VitE: neurological abnormalities
  • VitK: defective blood clotting
52
Q

Give examples of diseases occurring as a result of water-soluble vitamin deficiencies.

A
  • VitB12: anaemia
  • VitC: scurvy
  • Folate: neural tube defects, anaemia
  • Niacin: pellagra
53
Q

Where is dietary fibre found? Name examples.

A

Found in cereal foods (e.g. Bread, beans, fruit and veg).

E.g. Cellulose, lignin, pectins, gums.

54
Q

What is cellulose? Why can we not digest it?

A
  • Glucose polymer (like starch and glycogen).

- Don’t produce the required enzyme to break down the beta-1,6 cellulose linkages.

55
Q

Why is dietary fibre important? What is the recommended average intake?

A
  • Cannot be broken down by human digestive enzymes but essential for normal functioning of GI tract.
  • Low fibre intake associated with constipation and bowel cancer.
  • High fibre diet shown to reduce cholesterol and diabetes risk.
  • Recommended average intake for adults = 18g/day (but average intake is below this).

ESA 2 - MEH (42 decks)

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