Excretion

Question 1

How does liver break down amino acids

Answer 1

Amine groups removed from a.a by deamination producing ammonia and organic acids –> respired to give ATP and converted to carbohydrate and stored as glycogen

Organic acids used as ATP production or stored as glycogen

Ammonia combines with CO2 to form urea via the ornithine cycle and water occurring partially in mitochondria of liver cells

Urea is then excreted from liver cells and enters bloodstream and then is filtered out of the body via kidneys as a part of urine

Question 2

Where is ultrafiltration and what is the process of it

Answer 2

Glomerulus and Bowmans capsule
1. Blood enters glomerulus through afferent arteriole
2. Blood leaves glomerulus via smaller efferent arteriole maintaining high hydrostatic pressure
3. High pressure causes small molecules out of the blood via pores in the capillary endothelium
4. Basement membrane prevents large molecules from entering
5. Filtered fluid collected in Bowmans Capsule

Question 3

Where is selective reabsorption and what is the process of it

Answer 3

Occurs within the PCT (Proximal convoluted tubule) and lined with EPITHILIAL CELLS WHICH REABSORBS VARIOUS SUBSTANCES FROM FILTRATE BACK INTO BLOODSTREAM -> MICROVILLI -> INCREASE SA FOR REABSORPTION

1. Na+ actively transported into blood capillaries reducing Na+ conc. in Epithelial cells lining PCT
2. Na+ moves from PCT lumen into epithelial cells down its conc. gradient
3. Na+ is co transported with substances like glucose and amino acids into epithelial cells
4. These reabsorbed molecules can diffuse into blood capillaries

Question 4

What are cells that detect change in water potential and where are they found

Answer 4

Cortex and they are called osmoreceptors

Question 5

What is role of loops of henle

Answer 5

Cause decrease in water potential in medulla so water is removed from filtrate into interstitial space, and acts as a COUNTER CURRENT SYSTEM

Question 6

How does loop of Henle act as counter current system

Answer 6

As filtrate moves down collecting duct it loses water decreasing water potential, but pumping of ions into medulla out of ascending limb causes water potential of surrounding tissues in medulla to fall even lower than in the collecting duct. Hence this allows water to continue to move out of filtrate through the whole length of the collecting duct

Question 7

How are urine samples used for pregnancy tests

Answer 7

hCG binds to complementary antibody to form antibody-hCG complex
Antibody hCG complex moves along test stick with urine
hCG binds to immobilised antibody COMPLEMENTARY to them
binding of antibody produces coloured line

Question 8

How are urine samples used for drug detection

Answer 8

Carry out immunoassay where monoclonal antibodies bind to substance such as a drug or its breakdown products to indicate whether urine sample contains them
Vaporise urine sample with known solvent
Separate components of sample using gas chromatography
Use mass spectroscopy to identify molecular structures in sample

Question 9

What indicates how well kidney is able to function

Answer 9

GFR (Glomeular Filtrate)-> How much blood is filtered in the Bowmans capsule of the kidneys nephron
Low GFR -> Less effective blood filtration
High creatomome -> Signals that kidneys are not working proprelty

Question 10

What is dialysis

Answer 10

1.Dialysis fluid contains normal plasma levels of mineral ions/glucose hence they diffuse across semi permeable membrane into blood until their concentrations are normal
2.Dialysis fluid contains no urea hence urea is removed from blood to dialysis fluid via diffusion