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Agricultural Biochemistry > 2017 > Flashcards

2017 Flashcards

1
Q

What is catabolism?

A

Breaking down large molecules into smaller, simpler ones.

They release energy and are spontaneous

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2
Q

What is anabolism?

A

Synthesising large, complex molecules from small, simpler ones.
They require energy input

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3
Q

What is Gibbs free energy?

A

Change in enthalpy (heat) - temperature x change in entropy (structure)

This equation must have a negative answer for a reaction to occur

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4
Q

Why is equilibrium considered to be a dynamic state?

A

Both the forward and reverse reactions are constantly taking place, but the rates are equal, so no net change occurs in the concentration of the products or the reactants

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5
Q

What does the size of an equilibrium constant indicate about a system at equilibrium?

A

The size of the equilibrium constant indicates whether reactants or products are favoured.
(0.15-0.50 = intermediate)
Higher = product favoured
Lower = reactant favoured

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6
Q

What is a coupled reaction?

A

A reaction that releases energy, fuelling other processes.

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7
Q

What is an exergonic reaction?

A

A favourable reaction accompanied by release of energy

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8
Q

What is an endergonic reaction

A

An unfavourable reaction requiring absorption of energy

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9
Q

What is ATP?

A

Adenosine Triphosphate

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10
Q

What is ADP phosphorylation?

A

A non-spontaneous reaction as it requires an input of energy to proceed, which is sourced from acetyl CoA (combustion of food molecules).

ADP + Pi = ATP

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11
Q

What is liberated when a bond is formed?

A

Energy, the same amount is needed to break the bond

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12
Q

What is a covalent bond?

A

Strong, a negative electron is attracted to the positive nucleus on both atoms

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13
Q

What is a non-covalent bond?

A

4 types:

  • ionic: attraction between a negative and positive ion, therefore one atom is an electron donor (throne gaining is a negative ion)
  • hydrogen bond: hydrogen is bound to a highly electronegative atom (N,O,F)
  • Van der Waals: weak, neutral molecules attracted to one another
  • hydrophobic: non polar molecule aggregated in water
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14
Q

What does the pKa value represent?

A

The pH at which 50% dissociates (releasing H+)

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15
Q

What is a buffer?

A

Resists changes in pH if a solution

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16
Q

What is the role of protein

A

Transfer of genetic material, catalyse biochemical reactions, physical support and structure and transporting small molecules across membranes

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17
Q

What is a protein

A

3 base sequence of codons on the DNA

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18
Q

What does transcription do?

A

Edits to make mature mRNA

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19
Q

What does translation do?

A

Makes the matured mRNA into a protein

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20
Q

Is an enzyme a protein?

A

Yes

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21
Q

What do enzymes do?

A

Speed up the rate of reaction by reducing the activation energy without being consumed or used

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22
Q

What are the two models of enzymatic action?

A

Lock and key: shape of the enzyme active site is complementary to the substrate

Induced fit: enzyme folds itself around their substrate making a tight fit

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23
Q

What happens in a reaction with enzymes when the temperature is increased?

A

The rate of reaction increases and the enzymes denature

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24
Q

What is an inhibitor

A

A substrate that lowers or stops the rate of reaction

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25
Q

What are the 2 types of inhibitors?

A

Competitive: bind to active site therefore preventing the substrate from binding

Non-competitive: binds to the enzyme but not the active site and the binding can still happen but is less effective

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26
Q

What are co-factors?

A

‘Helper’ molecule for enzymes to facilitate reactions

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27
Q

When happens when you are in a starved state?

A

The peripheral tissues are hungry. Glucose and TAG is released by the liver and distributed to tissues around the body.

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28
Q

What happens during starvation when the muscles are wasting?

A

The wasting muscles release protein in the form of alanine and lactate by the combustion of glycogen and protein into the circulation. Liver then takes these as releases then a glucose by glucogenesis

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29
Q

What happens when the body is well fed?

A

Positive energy balance and the peripheral tissues are satisfied. Therefore the liver starts storing glucose in the form of glycogen and fat.

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30
Q

What is the purpose of metabolism?

A

To oxidise food to provide ATP.

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31
Q

What are the 3 generic steps for metabolism?

A
  1. Digestion and absorption: large molecules broken down into smaller ones
  2. Glycolysis and beta oxidation: numerous small molecules are degraded to simple units that play central metabolic roles
  3. TCA cycle and oxidative phosphorylation: final common pathway in mitochondria - ATP is made
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32
Q

What does brown fat do?

A

Oxidises food to generate heat

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33
Q

How is protein digested?

A

The stomach of pH 2 partially digests it (with pepsin) and then mostly digested and absorbed in the small cells.

Parietal cells in the stomach produce HCl = low pH

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34
Q

How are carbohydrates digested?

A

Starch is hydrolysed into glucose by pancreatic amylase

35
Q

How are fats digested?

A

Resynthesised into TAGs in the intestinal epithelial cells and sent into the lymphatic system which then enters the blood

36
Q

How are carbohydrates stored?

A

Polymerised and stored as glycogen in the liver and muscles

37
Q

How is glycogen stored

A

Stored in the liver as an energy reserve that can be metabolised quickly

38
Q

How is glucose stored?

A

It is readily converted into fat through the combustion of acetyl CoA

39
Q

How is fat stored?

A

TAG in adipose tissue which can be oxidised for energy

40
Q

How is protein stored?

A

Absorbed amino acids are used for protein synthesis and excess are broken down for ATP generation

41
Q

What are ketones?

A

Oxidised in TCA cycles for aerobic ATP production

42
Q

How does insulin work?

A

It is released when there is high blood glucose levels, which stimulates fat and glycogen storage

43
Q

How does glucagon work?

A

It is released when there is low glucose levels in the blood to stimulate the release of glucose from the liver and fatty acids from fat cells

44
Q

How does adrenaline work?

A

EPINEPHRINE. Stimulates glucose acquisition and burning by the masculature

45
Q

What is glycolysis?

A

‘Splitting of sugar’
Occurs in the cytosol (cell matrix), where it oxidises sugars and produces ATP and also NADH and pyruvate (these 2 can produce more ATP in oxidative phosphorylation)

46
Q

What is gluconeogenesis?

A

Making of sugar

47
Q

What conditions is glycolysis under?

A

Aerobic

48
Q

What happens to the NADH that is produced from glycolysis?

A

It is re-oxidised by transferring its electrons into the mitochondria yielding more ATP

49
Q

What happens to pyruvate that is produced from glycolysis?

A

It is funnelled into the mitochondria and converted into acetyl CoA for complete combustion (producing CO2 and H2O) and many more ATP

50
Q

What happens to the excess Acetyl CoA that has been made from pyruvate?

A

It Is stored as citrate and exported into the cytosol (matrix)

51
Q

How many ATP molecules are produced from NADH+ and FADH2?

A 
NADH+= 2.5 mol ATP
FADH2= 1.5 mol ATP
52
Q

Where does the TCA cycle happen?

A

Mitochondrial matrix

53
Q

What is the TCA cycle?

A

Series of reactions that oxidises acetyl CoA into CO2 to produce NADH and FADH2 (proton donors).

Main degenerative pathway for ATP production

54
Q

What is the ETC?

A

It uses redox to pimp protons from proton donors (NADH + FADH2) across the IMM and back again

55
Q

What does Acetyl CoA feed?

A

The TCA cycle in the mitochondrial matrix

56
Q

How does the ETC work?

A

Protons (H+) are pumped across IMM by complexes I-IV and creates an electrochemical gradient that can be coupled to make ATP. Protons then flow through the ATP synthase (complex V) to renormalise the gradient. This the. Spins the molecular motor and phosphorylation ADP

57
Q

What happens with ATP in a fast runner?

A

In anaerobic conditions, small amount of ATP is produced rapidly by reserves in muscle tissue. There is a high number of mitochondria

58
Q

What happens with ATP in a slow runner?

A

In aerobic conditions, large amount of ATP produced slowly and sustainably

59
Q

What are the three stored sources of muscle fuels?

A

Primary: fat from lipid droplets
Secondary: carbohydrate in the form of glycogen
Third: phosphocrearine, which provides immediate high energy phosphate for ADO phosphorylation in ATP synthesis

60
Q

When is fat combusted?

A

When a large supply of ATP is required and a slow rate

61
Q

What is beta oxidation?

A

Fatty acids are degraded to small compound (Acetyl CoA) in the mitochondrial matrix, which is then oxidises in the TCA cycle producing large amounts of NADH and FADH2.

62
Q

How are carbohydrates metabolised in the rumen?

A
  1. Cellulose and hemicellulose are digested to make glucose, which microbes use the energy liberated
  2. Simple sugars are combusted by glycolysis, microbes make pyruvate and use the energy liberated
  3. VFA from pyruvate, microbes don’t use pyruvate so they are then available for the host absorption and use therefore VFA Is the main end product for rumen fermentation
63
Q

What are the 3 major VFAs?

A

Acetate, propionate and butyrate

64
Q

Why are VFA important for ruminants?

A

Complex carbs cannot be digested by the host, so the microbes change it into VFA which can be used

65
Q

What is excess carbohydrates converted to ?

A

Fat, once the glycogen stores have been filled

66
Q

What are fatty acids synthesised from?

A

Acetyl CoA

67
Q

What do carbohydrates give rise to?

A

Pyruvate, which is then irreversible converted into Acetyl CoA

68
Q

What is the Acetyl CoA shuffle?

A

Acetyl-CoA is produced in the mitchondrial matrix, but it needs to be in the cytosol to be used for fatty acid synthesis. Acetyl-CoA reacts with oxaloacetate to make citrate, and the citrate gradient allows it to go from the matrix into the cytosol. In the cytosol, citrate reacts with Coenzyme A to get acetyl-CoA and oxaloacetate (requires ATP and citrate lyase). Oxaloacetate can’t diffuse back into the mitochondria.

69
Q

What is fatty acid biosynthesis?

A

Fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. This process takes place in the cytoplasm of the cell. Most of the acetyl-CoA which is converted into fatty acids is derived from carbohydrates via the glycolytic pathway.

70
Q

What is the Pentode Phosphate Pathway (PPP)?

A

Starts with glucose-6-phosphate in the cytoplasm and produces NADPH for fatty acid synthesis (NADPH is the reducing agent). It is parallel to glycolysis and oxidase glucose forming molecules such as nucleic acid

71
Q

What is gluconeogenesis?

A

Sugars created from non carb sources and amino acids, mainly happening in the liver and distributes glucose via circulation.

Almost the reverse of glycolysis

72
Q

How are amino acids broken down?

A

Protein -> A.A via hydrolysis

73
Q

Where does the fresh supply of amino acids come from for protein synthesis?

A

During amino acid breakdown, some are released within the cell during hydrolysis and are oxidised to then be completely degraded producing the fresh supply

74
Q

Where does excess amino acids go?

A

They get oxidised and serve as a source of carbon precursors for ATP

75
Q

How is amino acid oxidised (combusted)?

A
  1. The amino group is removed
  2. Transamination- Converts essential A.A into non-essential A.A
  3. Oxidative transamination- ammonia is released from the A.A, ammonia is toxic therefore it is excreted out after passing through the liver
  4. Can make intermediates for pyruvate, Acetyl CoA or completely oxidised into CO2 yielding ATP or used for gluconeogenesis
76
Q

What are the two amino acid precursors

A

Glucogenic: 3 or more C atoms -> oxaloacetate -> glucose
Ketogenic: forms Acetyl CoA

77
Q

What is ketosis?

A

In the liver, when oxaloacetate supply is insufficient and does not allow mitochondrial Acetyl CoA to enter the TCA cycle

78
Q

What is a genome?

A

Physical structure of the genetic code

79
Q

What is a gene?

A

Protein coding component of the genome

80
Q

What is gene expression

A

process by which information from a gene is used in the synthesis of a functional gene product. These products are often protein

81
Q

In hibernation, how is the pyruvate converted to Acetyl CoA

A

This is done via the phosphorylation of PDH which is inhibited by PDK-4. Reducing the combustion of CHO so cats can behaved instead

82
Q

By what mechanism is ATP produced by in hibernation?

A

Beta oxidation of fat

83
Q

What is pyruvate dehydrogenase?

A

Control of Acetyl CoA production from pyruvate, rate of CHO and protein combustion

84
Q

What is the PDK4

A

Inhibits the pyruvate dehydrogenase (PDH) therefore encouraging Acetyl CoA supply to come silt from beta oxidation of fat

Agricultural Biochemistry (3 decks)

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