Bio 4: Excretion

Question 1

Excretion

Answer 1

Removal of metabolic waste from the body

Question 2

Metabolic waste

Answer 2

The waste substances that may be toxic or are produced in excess by the reactions inside cells. E.g. CO2 and urea

Question 3

Carbon dioxide (as waste)

Answer 3

Passed from cells of respiring tissues. It is toxic in excess.
+Travels as hydorgencarbonate, this forms hydrogen ions that compete with oxygen for space on haemoglobin.
+Form carbaminohaemoglobin, reducing oxygen transport
+Respiratory acidosis, lower blood pH, blood becomes more acidic. Significant changes cause drowiness, headaches, confusion and even death.

Question 4

Urea (as waste)

Answer 4

Produced by deamination. This makes ammonia, which converted into urea, which is taken to the kidney.
Keto acid is used in respiration or for storage.

Question 5

Deamination

Answer 5

Removal of amine group from an amino acid to produce ammonia.

Question 6

Hepatic artery

Answer 6

Takes the oxygenated blood from the aorta into the liver

Question 7

Hepatic portal vein

Answer 7

Takes the deoxygenated blood from the digestive system to the liver.

Question 8

Hepatic vein

Answer 8

Blood leaves the liver, joins the vena cava

Question 9

Bile duct

Answer 9

Carries bile from the liver to the gall bladder

Question 10

Kupffer cells

Answer 10

Specialised macrophages that move in sinusoids. They breakdown and recycle old red blood cells. One product is bilirubin.

Question 11

Ornithine cycle

Answer 11

Process in which ammonia is converted to urea. It occurs partially in the cytosol and partly in mitochondria, as ATP is used.
Ammonia and carbon dioxide makes urea and water

Question 12

Alcohol detoxification

Answer 12

Ethanol is dehydrogenated to ethanal, then again to ethanoic acid. The final compound is acetate. This is combined with coenzyme A forming acetyl coenzyme A.

Question 13

Nephron

Answer 13

Functional unit of the kidney. Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine, which drains into the ureter.

Question 14

Glomerulus

Answer 14

Fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood. It is surrounded by a cup - or funnel-shaped capsule which collects the fluid and leads to the nephron.

Question 15

Selective reabsorption

Answer 15

Useful substances are reabsorbed from the nephron into the bloodstream while other substances remain in the nephron.

Question 16

Ultrafiltration

Answer 16

Filtration at a molecular level

Question 17

Podocytes

Answer 17

Specialised cells that make up the inner lining of the Bowman’s capsule. They have finger like projections called foot processes. This ensures there are gaps between the cells.

Question 18

Basement membrane

Answer 18

Fine mesh of collagen fibres and glycoproteins. This acts as a filter prevent large molecules getting through. Blood cells and proteins cannot get through. Water, amino acids, glucose, urea and inorganic ions can get through.

Question 19

Co-transporter proteins

Answer 19

Proteins in the cell surface membrane that allow facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose.

Question 20

Osmoregulation

Answer 20

Control and regulation of the water potential of the blood and body fluids. This is the kidney in humans.

Question 21

Loop of Henle

Answer 21

A descending limb into the medulla and an ascending limb into the cortex. This allows salts from the ascending limb into the descending. This increase the concentration in the tubule fluid, and causes them to diffuse out into the medulla.

Question 22

Cortex has high water potential because…

Answer 22

+ at the base sodium and chloride ions diffuse out of tubule
+high up, they are transported out
+ascending wall is impermeable to water (no water loss here)

Question 23

Distal convoluted tubule

Answer 23

In the cortex, between the loop of Henle and the collecting duct

Question 24

Collecting duct

Answer 24

Tubule fluid has a high water potential, water is lost depending on the presence of aquaporins. This lost by osmosis. The duct goes back into the medulla.

Question 25

ADH

Answer 25

Antidiuretic hormone, is released from neurosecretory cells in the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water. More ADH means more aquaporins are inserted into the collecting duct, this means more water is reabsorbed, and there is less urine.

Question 26

Osmoreceptors

Answer 26

Receptor cells that monitor the water potential of the blood.

Question 27

Haemodialysis

Answer 27

Blood is taken from a vein and passed through a dialysis machine so that exchange can occur across an artificially partially permeable membrane.
Heparin is added to avoid clotting.

Question 28

Peritoneal dialysis

Answer 28

Dialysis fluid is pumped into the body cavity so that exchange can occur across the peritoneum..

Question 29

Human chorionic gonadaotrophin

Answer 29

The hormone released by human embryos, it’s presence in the mothers urine as early as 6 days after conception confirms pregnancy.

Question 30

Monoclonal antibodies

Answer 30

Identical because they have been produced by cells that are clones of one original cell.

Question 31

Anabolic steroids

Answer 31

Drugs that mimic the action of steroid hormones that increase muscle growth.