Origin of waste products Flashcards
What does ureotelic mean?
Excrete excess protein-derived nitrogen as urea
What are the four stages to urea biosynthesis?
Transamination
Oxidative deamination
Ammonia transport
Urea cycle
What happens in transamination?
Amino acids are converted to glutamate
What happens in oxidative deamination?
Oxidative deamination occurs by glutamate dehydrogenase
What happens in ammonia transport?
Catalysed conversion to non-toxic glutamine for transport
What catalyses the conversion of ammonia to glutamine?
Glutamine synthase
How do amino groups travel from the muscle to the liver?
Via the glucose-alanine cycle
What is the amino carrier?
Alanine
What removes an amino group from alanine?
Alanine transaminase
What does alanine regenerate?
Glutamate
Gluconeogenic pyruvate
Describe how ammonia is converted to urea
ATP-dependent process
Requiring 5 enzymatic reactions
Describe urea
End product of nitrogen metabolism
Non-toxic
Uncharged, water soluble
Filtered and excreted by the kidneys
What factors increase urea excretion?
Excess protein intake
Protein energy malnutrition
Uncontrolled type 1 diabetes
Infections, burns, wasting disease
What factors decrease urea excretion?
Low protein diet Severe liver disease Glomerular nephritis Acute tubular necrosis Poor renal blood supply Renal obstruction
Where does uric acid come from?
Nucleic acid degradation yields purine and pyramidine bases
Purines breakdown enzymatically to uric acid
What would cause increased creatinine clearance?
Excessive meat diet
What would decrease creatinine clearance?
Wasting disease
Malnutrition
Poor renal function
What is urobilin?
Converted from urinary urobilinogen
What hormones would be seen in urine?
Hormonal end products
Deactivation of hormones
This makes them more polar and soluble
What are the advantages of urine testing?
Non-invasive diagnosis
Easily obtained
Normal composition known
What is red urine a sign of?
Blood
What is pseudohematuria?
Free Hb in the blood, myoglobin, porphyrins, drugs
What is red/brown urine?
Conjugated bilirubin
What is black urine?
Melanin
How would bacteria be detected in a urine sample?
Dipstick test for nitrite
What would white cells in the urine be evidence of?
Kidney infection
What would red cells in the urine be evidence of?
Damage
What diseases would cause acidic urine?
Uncontrolled diabetes
Starvation
Respiratory disorders
What diet would cause acidic urine?
Too much meat
What stones would be at risk of forming with acidic urine?
Uric acid
Cystine
What diseases would cause alkaline urine?
Urinary tract obstructions
Respiratory disorders
What diet would cause alkaline urine?
Citrus fruit
Vegetables
What stones are at risk of forming with alkaline urine?
CaPO4
MgPO4
CaCO3
Abnormal solute excretion is due to what two things?
Pre-renal
Renal
What things are excreted in small quantities?
Sugars
What would amino acids in the urine indicate?
Generalised tubular damage
Transporter defects
Raised plasma amino acid levels
What is the definition of proteinuria?
Over 200mg of protein excreted in 24 hours
What are the mechanisms of proteinuria?
Overflow
Glomerular
Tubular
Secreted
