5.1.2 Liver and Excretion Flashcards
Deamination
Amino Acid + Oxygen ->keto acid + ammonia
Keto Acid enters respiration to release energy
Ammonia enters the ornithine cycle to be converted into urea
Examples of Excretion
CO2: waste from respiration, excreted via the lungs
Nitrogenous Waste: urea, produced in the liver and excreted as urine via the kidneys
Bile Pigments: produced from the breakdown of haemoglobin in the liver and excreted as bile in the intestines (faeces)
Hepatic Artery
supplies liver with oxygenated blood from the heart
Hepatic Vein
Takes deoxygenated blood away from the liver
Hepatic Portal Vein
brings blood from the duodenum and ileum so that toxins can be filtered out and broken down here in the liver
Bile duct
takes bile produced by the liver to the gall bladder to be stored
carbohydrate metabolism
Hepatocytes are involved in the homeostatic control of glucose levels in the blood. When the blood glucose levels rise, insulin levels rise and stimulate hepatocytes to convert glucose into glycogen.
Detoxification
Level of toxins tend to increase. Apart from urea, many other metabolic pathways produce potentially poisonous substances. The liver is where most of these are detoxified.
Transamination
The conversion of one amino acid into another. This is important because the diet does not always contain the required balance of amino acids but transamination can resolve this issue
Excretion in kidneys
Blood enters kidney through renal artery and then passes through capillaries in cortex. When in capillaries, substances are filtered out of blood into tubules called ultrafiltration. Useful substances reabsorbed back into the blood called selective reabsorption. Remaining substances such as urea pass along tubules then along the ureter to the bladder to be expelled during urination. Filtered blood passed out of the kidney through the renal vein.
Selective Reabsorption
Occurs throughout the nephron after the renal capsule. When filtrate is first formed, it is hypotonic to the blood.
Most of this occurs in the PCT, cells lining tubule are adapted for the reabsorption of substances from the lumen, across them, into the blood capillaries around them.
85% reabsorbed
Causes of Kidney Failure
Diabetes
Hypertension
Genetics
Kidney stones
Main Problems with Kidney Failure
blood in urine proteins in urine selective reabsorption may stop urea and toxins may accumulate in the blood disrupted water/ion balance
Glomerular Filtration Rate (GFR)
Rate that substances are filtered out of the blood in the glomerulus into the renal capsule
below normal rate = kidneys not functioning
blood test measures conc of creatinine (a breakdown product from muscle cells)
Age, Gender and Fitness need to be taken into consideration
GFR readings
reading below 60 for 3+ months indicated severe chronic kidney disease
reading below 15 shows kidney failure
Haemodialysis
Patients blood is passed through a dialysis machine — blood flows in one side of the partially permeable membrane and dialysis fluid flows on the other side
Waste products diffuse into fluid, removing them from the blood. Larger molecules can’t pass.
Each session takes 3-5 hours and need 2-3 sessions weekly in hospital
patients feel unwell between sessions as waste products build up
Peritoneal Dialysis
Dialysis fluid is put through a tube that passed from outside the abdomen into their abdomen cavity. Waste products diffuse out into fluid across the peritoneum.
Fluid then drained out through tube
can be carried out at home either several times a day or one long overnight session
risk of infection around site of tube and patient doesn’t have dialysis free days.
Kidney Transplant
new kidney implanted to replace damaged kidney
doner must have same blood and tissue type. often donated from living relatives but can receive one from an organ doner.
advantage; cheaper, more convenient, can live fairly normal life
disadvantage; major surgery with risk of infection, risk of rejection, will have to take immunosuppressants so more at risk to illness
pregnancy tests
hCG molecules carried up test in urine and bind to mobile antibodies to form hCG/antibody complex
complex bunds to immobilised antibodies to form a coloured line of woman is pregnant
mobile antibodies within hCG move up to second window
excess mobile antibodies bind to immobilised antibodies to form a line whether pregnant or not
pregnancy test
A coloured line only occurs at the bottom window if woman is pregnant (requires presence of hCG)
A coloured line will spread in the top window either way — this is a control window to ensure test is working
recreational drugs
drugs such as cannabis, ecstasy or cocaine will be present in the urine
test strips containing antibodies that the drug will bind to
a sample of urine is applied to test strip and if present a colour change is i’ll occur indicating a positive result
if positive, urine sample is sent for further testing to confirm which drugs are used. second test uses GC/MS
Anabolic steroids
Drugs that build up muscle tissue that can cause liver damage.
Tested using Gas Chromatography/ Mass Spectrometry (GC/MS)
In GC, urine sample is vaporised and passed through a column containing a polymer. Different substances move through as different speeds to separate out.
Once separated, MS converts them into ions then separated via mass and charge
Results analysed by computer by comparing results of known substances to detect what was in the urine sample
Osmoregulation
controlling the amount of water and salts in the body
Increased Water Potential
Red Blood Cells become hypotonic and water enters the cell and it will eventually burst.
Water enters cell via diffusion (high to low conc)
Kills cells and reduces amount of red blood cells in the body
Decreased Water Potential
Red Blood Cells become hypertonic and shrink
Water leaves cells via diffusion (high to low conc) and enters the vessel
reduces oxygen carrying capacity and function
Ways water is lost
urine
faeces
breathing
sweating
ultrafiltration
Produces filtrate— some of this is reabsorbed (water, proteins, glucose) and some is excreted (urea, some mineral ions)
