5.1.2 Excretion Flashcards
What is excretion
The removal of metabolic waste from cells to maintain optimum cellular metabolism
How are excess amino acids excreted
Amine group removed (deammination)
Organic acid produced converted to acetate to be used in Calvin cycle and ammonia produced combines co2 to form urea via ornithine cycle. Urea excreted from liver cells and filtered out by kidneys.
What is the role of the liver in excretion
Filters blood
Converts ammonia to urea
Detoxification and waste removal
Bile production
Metabolism of drugs, hormones and others
Blood network of liver lobule
Oxygenated blood enters via hepatic artery
Blood rich in products from digestive enters via hepatic portal vein
The blood mixes in the sinusitis
Blood leaves via hepatic vein.
What is process of ultrafiltration
Blood enters glomerulus via afferent arteriole which has a wide lumen with blood under a high pressure, blood leaves glomerulus via efferent artiriole with a narrower lumen with blood under a low pressure. Creates a high hydrostatic pressure in the glomerulus.
This forces all small molecules out of blood through pores in endothelium of capillary into filtrate large molecules (proteins and blood cells) remain in blood. Molecules move through basement membrane (collagen fibres) which acts as another filter. They then pass through podocytes with pedicil projections wrapping around capillary further filtering the molecules. Filtrate then enters bowman’s capsule.
What is the process of Selective reabsorption
Sodium ions actively transported out of endothelium cell of pct tubule into blood to create low concentration of sodium inside cell. Sodium ions from filtrate now move down their concentration gradient, co transported with other molecules like glucose and amino acids. High concentration of glucose and amino acids created in pct cell. So glucose and amino acids leave the cell via facilitated diffusion into blood capillaries.
Loop of henle process
Descending limb impermeable to ions but permeable to water. Water leaves descending limb via osmosis to interstitial space with low water potential. Lowest water potential in loop of henle is achieved af the very bottom of the loop. As filtrate enters ascending limb, (impermeable to water and permeable to ions) sodium and chloride ions diffuse out of cell into interstitial fluid due to concentration gradient and low water potential. Further up the ascending limb, sodium and chloride ions are actively transported out of loop due to increased water potential in loop.
Role of distal convulated tubule
Reabsorbs water and mineral ions via active transport.
ADH effects permeability to water
What is the countercurrent multiplier
As filtrate moves down collecting duct it loses water
This decreases the water potential
Ions being actively transported out lowers water potential in interstitial space more than collecting duct allowing water to move out of filtrate entire length
Osmoregulation
Decreased water potential of blood detected by osmoreceptor cells in hypothalamus, water moves out of receptors causing them to shrink
Osmoreceptor cells send impulse to hypothalamus to produce ADH
ADH stored and released posterior pituitary gland into blood
ADH attaches to receptors on surface of dct and collecting duct cells.
This triggers secondary messenger molecules cAMP to initiate enzyme cascade
Aquamarine vesicles merge with cell surface membrane making cells more permeable to water.
Why are urine samples important
Allows diagnosis of certain diseases
High glucose indicates diabetes
High creatinine signifies muscle damage
Test for anabolic steroids
Pregnancy testing
How do pregnancy tests work
Wick of test dipped in urine
Mobile monoclonal antibodies attached to a dye bind to the hCG produce by pregnant women
hCG antibody complex binds to immobilised monoclonal antibodies to create a positive stripe
Remaining complex travels down and binds to more immobilised antibodies which are a control strip to show test has worked
How to test for presence of anabolic steroids
Mix specific antibodies with urine sample
Vaporise urine sample with known solvent
Seperate components using gas chromatography
Use mass spectrometry to identify molecular structures
What causes kidney failure
Kidney infections, inflammation can damage glomerulus
High blood pressure, damages glomerulus
Why is kidney failure bad
Build up of mineral ions causes osmotic and electrolyte imbalances
Build up of urea
High blood pressure (strokes ans potential heart problems)
What is dialysis
Patients blood passes on one side of partially permeable dialysis membrane and dialysis fluid is on other side in opposite direction flow
Dialysis fluid contains normal concentrations of ions and glucose
Ions and glucose diffuse from blood until normal concentrations are reached
Dialysis fluid contains no urea so all urea leaves blood entering dialysis fluid
Larger molecules cannot pass through membrane so remain in blood
Kidney transplant advantages
Relatively normal life
No dietary monitoring
Prevents build upmof waste
No regular dialysis
Kidney transplant disadvantages
Risk of rejection
Immunosuppressants for rest of life
Shortage of donors
Donor must be antigens compatible
Major surgery risks
