Biology : Homeostasis (9700 A2)

Specific Flashcards made for revision purposes by Ahmad Chaudhry.

What is Urea waste product of and how is it produced.

waste product of excess amino acids.
Produced by Deamination (removal of H and NH2 to produce NH3)
NH3 produced reacts with CO2 to produce Urea.

What is the mechanism for excretion in kidneys.

Ultrafiltration in Bowmans capsule
Selective Reabsorption in PCT, LOH, DCT and Collecting duct.

What are the 3 layers in which blood within the glomerulus is separated from the lumen.

• Endothelium (capillary gaps)

• Basement membrane (made of collagen, main barrier)

• Podocytes (Contain finger liked projections which form gaps)

Why is the lumen of afferent arteriole wider than that of efferent arteriole.

the wider the lumen, the more hydrostatic pressure, hence the substances from the blood are filtered out easily.

How does PCT Absorb Ions.

Na⁺ Ions are absorbed from the lumen of PCT into the cells, by active transport.
Gradient formed, Na⁺ now go from PCT cells into blood by facilitated diffusion.
Na is cotransporter alongside glucose.

Adaptations of PCT cells.

• Numerous microvilli (High SA for absorption)

• Transport proteins for Reabsorption

• Aquaporins

• High Mitochondria (ATP production)

• Tight Junctions (holding adjacent cells together)

How is water reabsorbed in Loop of Henle (LOH)

1) In Ascending limp, Cl and Na ions are pumped out by AT (Active transport)
2) Due to difference in concentration, water moves to DCT
3) Na and Cl in tissue fluid will diffuse into Descending limb.
4) Water moves out into tissue fluid. Reabsorbed.

ADH is released from.

Posterior Pituitary Gland.

Describe the ADH response.

1) Bind to plasma membrane receptors on DCT/CD
2) Activates a series of enzyme controlled reaction (To produce active Phosphorylase)
3) Vesicles containing aquaporins fuse with membrane of lumen side
4) Permeability is increased.

What cells produce insulin.

Beta cells

What cells produce Glucagon.

Alpha Cells

In which parts of the body does insulin act.

Muscle cells
Adipose cells
Liver cells

How does insulin lower blood glucose.

• Increase permeability (GLUT proteins within vesicles will fuse with the membrane, hence more facilitated diffusion)

• Increase glucose uptake (activation of glucokinase)

• Increased respiration rate

• Glycogenesis (Glucose → Glycogen by Phosphofructokinase and Glycogen Synthetase. Stored in liver + muscle cells)

• Increase protein and lipid synthesis

• Gluconeogenesis doesn’t happen.

How does Glucagon act on cells when produced.

• Binds to cell surface membrane receptor

• receptor changes shape

• activates G protein

• which activates adenyl cyclase

• adenyl cyclase reacts with ATP to produce cAMP

• cAMP acts as secondary messenger and activate protein kinase

• Enzyme cascade reaction takes place

What are effects of glucagon.

• cAMP will activate breakdown of Glycogen to glucose.

• Use Proteins + Lipids as respiratory Substrate

• Glucose released form GLUT proteins in liver

• Glucose raised

Which 2 enzymes are immobilized on the dipstick test pad.

Glucose Oxidase and Peroxidase.

What is the function of glucose oxidase?

Catalyze reaction of glucose → Gluconic Acid + Hydrogen Peroxide

What is the function of Peroxidase.

Catalyze reaction of Hydrogen peroxide + Chromogen → Darker Compound