5.2 Excretion as an example of homeostatic control Flashcards
Define excretion (1)
The removal of metabolic waste from the body.
What are the 3 main excretory products?
Carbon dioxide
Nitrogenous waste compounds
bile pigments
In what three ways is C02 transported around the body? (3)
5% dissolved in plasma
10% carbaminohaemoglobin
85% HCO3- hydrogen carbonate
How does carbon dioxide lower the pH of blood? (2)
CO2+H20—–> H203 carbonic acid
H203 dissociates——-> H+ + HCO3-
How do deamination and urea formation occur? (2)
AA + Oxygen—->keto acid + ammonia
ammonia + co2——>urea + H20
Name three functions of the liver (3)
storage of glycogen/maintain glucose conc bile synthesis breakdown RBC's breakdown of hormones storage of vitamins breakdown excess AA- urea detoxification of alcohol
Describe the process of the detoxification of alcohol.
ethanol dehydrogenase breaks down ethanol into ethanal
ethanal is dehydrogenated again by ethanal dehydrogenase
forming ethanoic acid
The hydrogen ions are conbined with NAD to form reduced NAD
What are the four tubes running through/along side a hepatocyte?
Bile duct
hepatic vein
hepatic portal vein
hepatic artery
What does a kupffer cell do? (1)
digests old RBC’s
In which direction does the hepatic artery carry blood? Is the blood oxygenated or deoxygenated?
away from heart to hepatocytes (oxygenated)
In which direction does the hepatic portal vein carry blood? Is it oxygenated/deoxygenated?
from digestive system to liver
In which direction does the hepatic vein carry blood?
Away from liver towards heart vena cava
Define ultrafiltration. (1)
The filtration of the blood at a molecular level under pressure.
The renal artery splits to form many afferent arterioles which each lead to a knot of capillaries called the WHAT?
Glomerulus
What is each glomerulus surrounded by
Bowman’s capsule
What are the 3 layers of the barrier between the capillary’s blood and the lumen of the bowmans capsule?(6)
Endothelium of the capillary- gaps between cells, and pores in the cells allowing plasma out of capillary
Basement membrane- collagen fibres and glycoproteins stops big molecules through like RECs
Epithelial cells of Bowmans capsule- called podocytes, have foot processes ensure gaps between cells so fluid can pass into Bowmans capsule
What does the blood plasma contain? (5)
Water Amino acids Glucose Urea Inorganic materials ions (sodium, chloride, potassium)
Why is peritoneal dialysis fluid replaced four times a day whereas haemodialysis patients only need treatment three times a week?
peritoneal removes less waste than heamo
haemodialysis is constantly refreshed
haemodialysis maintains conc grad but peritoneal conc grad reduces
Where is glucose selectively reabsorbed into the kidneys?
the proximal convoluted tubule
How are glucose and amino acids selectively reabsorbed?
sodium ions are actively pumped out of the cell
so conc of sodium decreases creating conc grad
sodium ions diffuse into cell through cotransport protein carrying either glucose or AA
water moves into cell by osmosis
glucose and aa diffuse into blood
How are the cells lining the tubule specialised to achieve reabsorption? (4)
microvilli increase sa
cotransport proteins in membrane
other end of cell also folded to increase sa and has sodium potassium pumps
many mitochondria for lots of atp
How are the cells lining the tubule specialised to achieve reabsorption? (4)
microvilli increase sa
cotransport proteins in membrane
other end of cell also folded to increase sa and has sodium potassium pumps
many mitochondria for lots of atp
How do we alter the permeability of our collecting ducts? (4)
ADH detected by cell surface receptors
enzyme controlled reactions
causing vesicles containing water peprmeable channels (aquaporins) to fuse with membrane
so more water can be reabsorbed
How do we alter the concentration of ADH in the blood?
Osmoreceptors in hypothalamus shrink when wp is low
stimulates neurosecretory cells in hypothalamus
ADH made in cell body (in hypo) moves down axon to terminal bulb in pituitary gland where its stored in vesicles.
when neurosecretory cells are stimulated by osmoreceptors, they carry actionpotentials down the axon and release ADH by exocytosis
How do pregnancy tests work? (5)
urine onto stick
hCG binds to antibodies attached to blue bead
mobile antibodies move down test stick
if hCG is present it binds to fixed antibodies holding bead in place forming blue line
mobile antibodies with no hCG attached bind to another fixed site to show test is working
Define the ornithine cycle
A series of biochemical reactions that convert ammonia to urea
