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what is the function of the glomerulus?
blood filtration
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what is the function of the proximal convoluted tubule?
reabsorption, ammoniagenesis, and gluconeogenesis
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what is the function of the loop of henle?
establish salt gradient
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what is the function of the distal convoluted tubule (DCT)?
fine tuning electrolyte reabsorption
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what is the function of the collecting duct?
water balance
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what can the glomerulus filter?
small-moleculare-weight and water soluble compounds, <5000 daltons (D)
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what are the three layers of the glomerular filter?
- fenestrated capillaries
- basal lamina
- slits formed by podocyte foot processes
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at what dalton (D) are proteins too big to be filtered in the glomerulus?
>75,000 D
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what repels negatively charged compounds from being not easily filtered at the glomerulus?
negatively charged glycosaminoglycans (GAG) in the basal lamina of the glomerulus
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what shape is more easily filtered through the glomerulus?
flexible coils (more easily filtered than rigid spheres)
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what are the processes and pathways active in the proximal convoluted tubule?
- acronyme RAG:
- reabsorption (glucose, amino acids, electrolytes calcium sodium, peptides, small proteins)
- ammoniagenesis (for buffering)
- gluconeogenesis
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what three enzymes is the proximal convoluted tubule missing that does not allow it to take part in glycolysis?
- hexokinase (HK)
- phosphofructokinase 1 (PFK1)
- pyruvate kinase (PK)
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what are the advantages and disadvantages of not having glycolysis in the cell?
- Advantages: consverves glucose, minimizes regulatory issues that would happen with gluconeogenesis in the same cells
- Disadvantages: unable to generate ATP in anaerobic conditions
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what is the function of ammoniagenesis?
degrades glutamine to generate two ammonia ions to buffer uninary acid
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where is ammoniagenesis most active in normal conditions?
starving and acidosis conditions?
- normally-distal convoluted tubule
- starving and acidosis-dramatically increases in poximal tubule, still happenin in distal convoluted tubule
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what happens in the liver and kidney in an acidosis state?
- liver-urea synthesis decreases
- kidney-glutamine synthesis will increase
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during acidosis what happens to the rate of hepatic amino acid catabolism?
it will remain constant (but, liver produces less urea and more glutamine, significant portion of gluconeogenesis shifts to kidney)
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which has higher gram for gram glucose synthetic rates, the liver or kidney?
kidney
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what are the primary glucose precursors for gluconeogenesis in the liver?
alanine, glucogenic amino acid (not BCAAs), lactate, glycerol
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Decreased activity of CPSI leads to what 4 thing in the liver?
- decreased urea synthesis
- decreased hydrogen ion production
- increased hepatic glutamine synthesis and export
- decreased hepatic gluconeogenesis (carbon skeletons used for glutamine synthesis and export rather than gluconeogenesis)
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