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biochemistry > Protein and amino acid metabolism > Flashcards

Protein and amino acid metabolism Flashcards

1
Q

Which substances lead to Acetyl CoA?

A
  • Pyruvate (from amino acids and glucose)
  • Ethanol
  • Acetoacetate (ketone body)
  • Palmitate (fatty acid)
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2
Q

Can amino acids be stored?

A

No

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3
Q

How are surplusses of amino acids used?

A
  • Energy production (Nitrogen excreted)
  • Fat production
  • Protein synthesis if needed
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4
Q

How is pepsin activated?

A

From pepsinogen by H+

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5
Q

How is trypsin activated?

A

From trypsinogen by enteropepsidase

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6
Q

Which enzymes does trypsin activate?

A
  • Chymotrypsin
  • Elastase
  • Carboxypeptidases
  • Lipase
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7
Q

How is the proteolysis of zymogens regulated to prevent damage in the digestive system?

Zymogens are dangerous pro-enzymes

A

Trypsin inhibits the production of itself

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8
Q

How is a peptide bond formed?

A

Amino group + carboxylate group

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9
Q

How are amino acids taken up by the liver?

A
  1. Amino acids enter the serosal cell along Na+
  2. Na+ is actively transported out and potassium is taken up
  3. Amino acids enters the portal vein by transporters
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10
Q

How do gut cells use amino acids?

A

To produce energy

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11
Q

How do levels of amino acids in the blood change?

A
  • Dietary protein
  • Endogenous protein
  • Protein synthesis
  • Nitrogen products excreted into urine
  • Amino acids produced from glucose
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12
Q

How are amino acids used during gluconeogenesis?

A
  • Carbon skeletons for glucose synthesis
  • Nitrogen excreted in form of NH4+
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13
Q

What is the simplest route from amino acid to energy, glucose or fat?

A

From Alanine to pyruvate by alanine aminotransferase

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14
Q

What is a transamination reaction?

A

Amino acid is added to ketoacids to form new amino acids

Transamination reactions are used for synth. and degr. for new AA

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15
Q

Which amino acids lead to pyruvate?

A
  • Alanine
  • Serine
  • Cysteine
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16
Q

Which amino acids lead to oxaloacetate?

A
  • Aspartate
  • Asparagine
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17
Q

How does aspartate lead to oxaloacetate?

A

Transamination reaction

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18
Q

How does aspartate convert to asparagine?

A

By glutamine to glutamate by asparagine synthetase

With 1 ATP

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19
Q

How can asparagine convert to aspartate?

A

With H20 to NH4+ by asparaginase

Asparagine loses an amine group

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20
Q

Which amino acids lead to alpha-ketoglutarate?

A
  • Arganine
  • Histidine
  • Glutamine
  • Proline
  • Glutamate

The 4 AA’s lead to glutamate which leads to a-ketoglutarate

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21
Q

Which AA’s lead to succinyl CoA

Succinyl CoA is metabolite after a-ketoglutarate in TCA

A
  • Valine
  • Threonine
  • Isoleucine
  • Methionine
22
Q

Which AA’s lead to Fumarate

Fumarate is metabolite in TCA

A
  • Aspartate
  • Tyrosine
  • Phenylalanine
23
Q

Which AA’s can be comverted to acetyl CoA?

A
  • Threonine
  • Lysine
  • Isoleucine
  • Tryptophan
24
Q

How are ketone bodies formed from acetyl CoA?

A

Acetyl CoA+Acetoacetyl CoA to HMG CoA to acetoacetate (ketone body)

25
Q

Which amino acid converts into HMG CoA?

A

Leucine

26
Q

Which AA’s convert to acetoacetate (ketone body)

A
  • Phenylalanine
  • Tyrosine
27
Q

Which two AA’s are only ketogenic?

A
  • Leucine
  • Lysine

Look at slide 32 for all amino acids

28
Q

How are newborns screened for deficiencies in AA degradation?

A

Heelprick

29
Q

How are non-essential amino acids synthesised?

A

Transamination reactions

These are reversible

30
Q

Which vitamin is needed for transamination reactions?

Look at slide 35!!!

A

B6

PLP is an active complex of B6

31
Q

Which AA is increased when there is a surplus of other AA’s?

A

Glutamate

Glutamate can be produced from a-ketoglutarate (TCA)

32
Q

How can glutamate be converted to a-ketoglutarate?

A
  • Transamination
  • Deamination by glutamate deaminase

Byproduct NH4+

33
Q

How can surplus nitrogen be secreted through glutamate?

A
  1. Transamination from a-ketoglutarate to glutamate
  2. Deamination by glutamate dehydrogenase
34
Q

Where does the urea cycle take place?

A

Liver

35
Q

Which enzyme converts pyruvate to acetyl CoA?

A

Pyruvate dehydrogenase

Lipogenesis

36
Q

Which enzyme converts pyruvate to oxaloacetate?

Gluconeogenesis

A

Pyruvate carboxylase

37
Q

What is negative nitrogen balance?

A

If more nitrogen is lost than put in

38
Q

Which tissue is lost during fasting?

A

Muscle tissue

Because amino acids are the source of glucose and not fat

39
Q

What is the glucose-alanine cycle?

A
  1. Alanine from muscle
  2. Alanine to pyruvate in liver
  3. Pyruvate to glucose in liver
40
Q

Which proteins are preferably used for gluconeogenesis?

A

Proteins with high alanine and glutamine content

41
Q

Where can alanine and glutamine rich proteins be found?

A

In the forearms

42
Q

How are fatty acids metabolized?

A

Through the TCA cycle and released as CO2

Fatty acids cannot produce glucose, that is why muscle is used

43
Q

Which compound from triglycerides can be used for gluconeogenesis?

A

Glycerol

44
Q

What are the primary enzymes in glycolysis?

A
  1. Glucokinase
  2. Phosphofructokinase
  3. Pyruvate kinase
  4. Pyruvate dehydrogenase

Kinases add phosphate groups

45
Q

Which are the primary enzymes during gluconeogenesis?

A
  1. Pyruvate decarboxylase
  2. PEP carboxykinase
  3. Fructose-1,6-biphosphatase
  4. Glucose-6-phosphatase

Fructose-2,6-biphosphate most important regulator

46
Q

Via which TCA metabolite does pyruvate convert into glucose?

A

Oxaloacetate

47
Q

Where does the conversion of pyruvate to oxaloacetate take place?

By enzyme pyruvate carboxylase (adds carboxyl group)

A

Mitochondria

Oxaloacetate cannot easily cross this membrane

48
Q

Which molecule inhibits the TCA cycle?

A

NADH

49
Q

Which metabolites can indirectly be converted into glucose?

A
  • Malate
  • Oxaloacetate
50
Q

Gluconeogenesis needs energy, how is this produced?

A

By beta-oxidation

fatty acid processing to acetyl CoA

51
Q

Pyruvate carboxylase is activated by which matabolite?

A

Acetyl CoA

biochemistry (13 decks)

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