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Year 2 - Renal (DP) > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

What are the cons to using inulin to measure eGFR?

A

It isn’t endogenous

It’s difficult to measure

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2
Q

What makes up the urea in the urea cycle?

A

Endogenous ammonia

Ammonia in the portal circulation

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3
Q

How much urea is excreted by the kidney?

A

75%

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4
Q

Where does the urea that isn’t excreted by the kidney go?

A

Into the blood

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5
Q

What do ureases and proteases do?

A

Breakdown urea and proteins respectively into ammonia

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6
Q

Where do blood proteins come from?

A

Diet
Bacteria
Cells

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7
Q

What can happen to blood ammonia?

A

Enters portal circulation

Changed into ammonium ion (which can then enter the portal circulation or be excreted in stool)

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8
Q

What percentage of ammonia/urea in the portal circulation enters the systemic circulation?

A

15%

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9
Q

Where does the majority of the urea cycle occur?

A

In the cell cytosol

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10
Q

What step in the urea cycle occurs in the mitochondrial matrix?

A

Ornithine conversion to Citrulline by the addition of Carbamoyl Phosphate

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11
Q

What forms Carbamoyl Phosphate?

A

Carbon Dioxide and Ammonium (with 2ATP molecules)

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12
Q

When is urea produced in the urea cycle?

A

When Arginine is converted to Ornithine

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13
Q

What is the chemical formula of urea?

A

CO(NH2)2 (ie. Diaminomethanal)

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14
Q

When is Fumarate produced in the urea cycle?

A

During the conversion of Arginosuccinate to Arginine

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15
Q

What step in the urea cycle requires the addition of Asparate?

A

Conversion of Citrulline to Arginosuccinate

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16
Q

What are the cons of using urea to estimate GFR?

A

Doesn’t appear at a constant rate
It is reabsorbed in the renal tubule
It undergoes extra-renal elimination

17
Q

What does Creatine Kinase do? What else does this conversion require?

A

Converts Creatine -> Phosphocreatine:

- Requires ATP

18
Q

Where can creatinine come from?

A

Muscle turnover
Creatine
Phosphocreatine

19
Q

How much creatinine is filtered out at the glomerulus?

A

90-95%

20
Q

Is any creatinine secreted in the renal tubules?

A

Yes:

- 5-10% in the DCT

21
Q

What is the only con of using creatinine as a measure of eGFR?

A

It is secreted in the DCT

22
Q

When is the use of creatinine useless for calculating eGFR?

A

If GFR >60ml/min

23
Q

How is creatinine clearance calculated?

A

[Creatinine]urine x Urine Volume
Divided by
[Creatinine]plasma x Duration of collection

24
Q

What is the rough creatinine clearance in young, well-built people?

A

Arround 120ml/min

25
Q

What proteins are seen in overflow proteinuria?

A

Bence Jones Proteinuria (in myeloma)

Myoglobinuria (in Rhabdomyolysis)

26
Q

What type of proteins are seen in glomerular proteinuria?

A

Albumin

27
Q

What proteins are seen in tubular proteinuria?

A

β₂ microglobulin

α₁ microglobulin

28
Q

What protein is seen in secreted proteinuria?

A

Tamm-Horsfall protein (most commonly excreted protein in normal urine)

29
Q

How does hypoalbuminaemia result in oedema?

A

Results in decreased capillary oncotic pressure:

-> Water loss from vessels in ECF

30
Q

What is a normal ACR?

A
31
Q

What is microalbuminaemia defined as?

A

PCR 45-149mg/mmol
ACR:
- 2.5-30 (Men)
- 3.5-30 (Women)

32
Q

What PCR defines nephrotic syndrome?

A

> 450 mg/mmol

33
Q

What volume is filtered by the kidneys every day?

A

180L

34
Q

What is the urine sodium in pre-renal failure?

A
35
Q

What is the urine/serum urea ratio in pre-renal failure?

A

> 10:1

36
Q

What is the urine/serum osmolality ratio in pre-renal failure?

A

> 1.5:1

37
Q

What is the urine sodium in intrinsic renal damage?

A

> 40nmol/L

38
Q

What is the urine/serum urea ratio in intrinsic renal damage?

A
39
Q

What is the urine/serum osmolality ratio in intrinsic renal damage?

A

Year 2 - Renal (DP) (15 decks)

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