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Flascards > Liver > Flashcards

Liver Flashcards

1
Q

How do skeletal muscle cells convert and transport ammonia to the liver

A
  • glutamate + pyruvate = alanine + alpha ketoglutarate
  • enzyme = alanine transaminase (ALT)
  • alanine moves in the blood and transports ammonia to the blood

ammonia + alpha ketoglutarate = glutamate
-enzyme = glutamate dehydrogenase

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2
Q

How is ammonia released in the liver from different molecules to enter the urea cycle

A
  • glutamate = alpha ketoglutamate + ammonia
  • enzyme = glutamate dehydrogenase
  • glutamate + oxaloacetate = alpha ketoglutarate + aspartate
  • enzyme = aspartate transminase (AST)
  • alanine + alpha ketoglutarate = glutamate + pyruvate
  • enzyme = alanine transaminase (ALT)
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3
Q

Which amino acid is the only one that can directly enter the urea cycle

A

-aspartate

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4
Q

What organic groups are the urea made of

A
  • 2 nitrogen groups

- 1 carboxyl group

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5
Q

What is the first step of the urea cycle

A
  • ammonia + CO2 + 2ATP (bicarbonate) = carbamoyl phosphate
  • enzyme = carbamoyl phosphate synthetase 1 (CPS1)
  • this is the rate limiting step because of the n-acetylglutamate
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6
Q

Which molecule allosterically activates carbamoyl phosphate synthetase 1 (CPS1)

A

N-acetlyglutamate

-so increases the rate of urea synthesis

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7
Q

What molecules form n-acetylglutamate

A
  • glutamate + acetly-CoA = N-acetylglutamate

- enzyme = n-acetylglutamate synthestase

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8
Q

What is the 2nd step of the urea cycle

A
  • Ornithine + Carbamoyl phosphate = Citrulline + free phosphates
  • enzyme = orthinine transcarbamoylase
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9
Q

What is the 3rd step of the urea cycle

A
  • citrulline + aspartate + ATP = arginino-succinate

- enzyme = argininosuccinate synthetase

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10
Q

What is the 4th step of the urea cycle

A
  • arginino-succinate = fumarate + arginine

- enzyme = arginino-succinate lyase

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11
Q

What is the fumerate from the 4th step of the urea cycle used for

A
  • fumerate = malate

- malate =oxaloacetate (enzyme - malate dehydrogenase)

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12
Q

Why is oxaloacetate and aspartate transminase (AST) enzyme important in the urea cycle

A

-they regenerate aspartate to enter the urea cycle

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13
Q

What molecule is directly broken down to make urea and by which enzyme

A
  • arginine = urea + ornithine

- enzyme = arginase

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14
Q

What makes up a nucleotide

A
  • 5 carbon sugar (either deoxyribose or ribose)
  • phosphate group
  • nitrogenous base
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15
Q

Give the 3 pyrimidine bases

A
  • cytosine
  • thyamine
  • uracil
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16
Q

Give 2 purine bases

A
  • guanine

- adenosine

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17
Q

What is a nucleoside

A
  • nitrogenous base

- 5 carbon sugar

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18
Q

Give the names of some DNA nucleosides and the RNA counterparts

A
  • deoxyadenosine (DNA) and adenosine (RNA)
  • deoxyguanosine and guanosine
  • deoxycytidine and cytidine
  • deoxythymide and uridine
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19
Q

What are the 2 ways of making nucleotides (nucleotide synthesis)

A
  • de novo synthesis

- salvage pathway (from diet too)

20
Q

How does de novo synthesis occur

A

Starts with

  • ribose 5-phosphate + ATP = AMP + phosphoribosyl pyrophosphate (PRPP)
  • enzyme = ribose phosphate pyrophoshokinase
21
Q

Which enzyme converts RNA nucleotides (in diphosphate form) to DNA nucleotides

A

-ribonucleotide diphosphate reductase

22
Q

What is different about how purines and pyrimidines can be broken down

A
  • pyrimidines can be broken down completely into CO2 + NH3 (ammonia) which can be exhaled by the lungs or removed by the kidneys
  • purines are converted into uric acid which is then excreted into urine
23
Q

How does gout occur

A
  • build up of uric acid which enters joints and tendon
  • the uric acid becomes monosodium urate which crystallises
  • the body forms proteins around these crystals and the complex is called tophi
  • and tophi causes an inflammatory reaction called gout which usually occurs in the big toes
24
Q

How does salvage pathway produce nucleotide

A
  • hypoxanthine and guanine from purine degradation are converted back to GMP (guanine monophosphate) and IMP (iosine monophosphate) which can be converted to AMP (adenosine monophosphate)
  • through enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT) which returns the ribose and phosphjate group back to hypoxanthine and guanine
25
Q

What is Lesch-Nyhan syndrome (also called juvenile gout)

A
  • a complete abscene of hypoxanthine guanine phosphoribosyl transferase (HGPT)
  • causes too much uric acid produced by purine degradation
  • leads to gout
  • a genetic disease

Symptoms include

  • self-mutilation
  • causes gout in very young patients (thats why it is called juvenile gout)
26
Q

What does cholesterol do

A
  • helps to maintain the structure of the cell membrane
  • used to make bile acids
  • used to make steroid hormones
  • used to make vitamin D
27
Q

Where cholesterol synthesis occur

A
  • cholesterol synthesis is also called the mevalonate pathway
  • the smooth endoplasmic reticulum
28
Q

How cholesterol synthesis occur

A
  • acetyl-CoA + acetyl-CoA = Acetoacetyl-CoA + CoA
  • enzyme = acetyl-CoA acyl-transferase

Next

  • acetoacetyl-CoA + acetyl-CoA = HMG-CoA + CoA
  • enzyme = HMG-CoA synthase

Next

HMG-CoA = Mevalonate + CoA-SH + H2O
-enzyme = HMG-CoA reductase
(This is the rate limiting step/enzyme)

29
Q

What is the rate limiting enzyme and step of cholesterol synthesis

A
  • reduction of HMG CoA = Mevalonate + CoA-SH + H2O

- enzyme = HMG-CoA reductase

30
Q

What 3 proteins are used to regulate cholesterol synthesis

A
  • SREBP (sterol regulatory element binding protein)
  • INSIG1
  • SCAP
31
Q

What is the last precursor to cholesterol formation

A

7-dehydrocholesterol

32
Q

How does -dehydrocholesterol react with sunlight

A

7-dehydrocholesterol forms cholecalciferol (vitamin D3) when hit with a photon of light

33
Q

How is cholesterol affected by temperature

A
  • at low temperatures, cholesterol puts more space between the phospholipid so the cell membrane is more fluid
  • at high temperatures, cholesterol pulls phospholipids closer together so it is more rigid
34
Q

How do the cortex of the adrenal gland use cholesterol

A
  • use it to create corticosteroids like cortisol and aldosterone
  • cortisol is used in fight or flight
  • aldosterone is used to regulate blood pressure
35
Q

What is the rate determining enzyme of the urea cycle

A
  • carbamoyl phosphate synthetase 1 (CPS1)

- converts ammonia + bicarbonate = carbarmoyl phosphate

36
Q

Deficiency of which enzyme is the most common genetic cause of increased ammonia levels

A
  • ornithine transcarbamylase

- it converts carbamoyl phosphate + ornithine = citrulline + phosphate

37
Q

How many amino acids are in a dipeptide

A

2

38
Q

How many amino acids are in a polypeptide

A

-less than 50

39
Q

How many amino acids are in a protein

A

-greater than 50

40
Q

How is nitrogen lost from the body

A
  • renal excretion (around 70g per day)
  • faecal loss (around 10g per day)
  • skin/hair/sweat loss
41
Q

Which amino acids are both ketogenic and glucogenic

A
  • isoleucine
  • tryptophan
  • phenylanine
  • tyrosine
42
Q

What is the lifespan of crystallin protein

A

-life of the organism

43
Q

What is the lifespan of haemoglobin

A

-lifespan of the red blood cell (120 days)

44
Q

What is the lifespan of ornithine decarboxylase

A

Half life of 11 minutes

45
Q

What does a diamond on a genetic diagram stand for

A

-undetermined gender in a preganancy

46
Q

What does a triangle on a genetic diagram stand for

A

-miscarriage

Flascards (17 decks)

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