5.1.2 Excretion COMPLETE Flashcards
DEFINITION- Excretion
The removal of the waste products of metabolism from the body.
CO2 Transport
- CARBONIC ACID- Water and CO2 converted by carbonic anhydrase. Then dissociates into H+ and HCO3-
- CO2 also dissolves into the plasma forming carbonic acid
- CO2 also directly binds to haemoglobin forming CARBAMINOHAEMOGLOBIN
Effect of increasing CO2
Increased CO2 leads to more H+ ions increasing acidity. Proteins act as a buffer taking up H ions.
Medulla Oblongata detects increase in H ions and increases breathing rate.
Respiratory Acidosis
Medical Condition in which decreased ventilation causes increased blood CO2 conc. and decreased pH.
Caused by asthma, blockages of the airways and emphysema.
Functions of the Liver
CONTROL- blood sugar, lipids and amino acids
SYNTHESIS- plasma proteins, cholesterol, bile
STORAGE- vitamins A/D/B12, from, glycogen
DETOXIFICATION- Alcohol, Drugs
BREAKDOWN- Old RBC, hormones
Hepatic Artery
Moves from the Aorta to Liver, blood contains O2 for aerobic respiration.
Hepatic Portal Vein
From the small intestine to the liver, blood contains amino acids and glucose. Not connected to the heart
Hepatic Vein
From the liver to the vena cava, blood contains CO2 and waste products of respiration.
Bile Duct
From the liver to the gallbladder, containing the bile produced by hepatocytes
Liver Lobules
The lobule is formed by many hepatocytes
Branches of the hepatic artery and portal vein carry blood betweens rows and are called SINUSOIDS
The central vein is a branch of the hepatic vein.
Channels carry bile are called BILE CANALICULUS
KUPFFER CELLS line the sinusoids
Hepatocyte Structure
Lots of organelles such as mitochondria and ribosomes
Glycogen granules and fat droplets
Microvilli to increase SA
Kupffer Cell Structure
Specialised macrophages, engulf bacteria and breakdown RBC, product of the breakdown includes Bilirubin
Formation of Urea
- Deamination
2. The Ornithine Cycle
Deamination
Excess amino acids can’t be stored
The amino group is removed to form ammonia.
Keto Acids remain or their converted into fats for storage
The Ornithine Cycle
Produces urea from ammonia, as urea is less toxic and less soluble.
Dissolves in plasma to be excreted by kidneys
Uses ATP and CO2, takes place in the mitochondria
DEFINITION- Detoxification
Conversion of toxic molecules to less toxic molecules, e.g. catalase breaks down hydrogen peroxide into water and oxygen
Ethanol
A drug that depresses nerve activity, small lipid molecules that cross the plasma membrane via simple diffusion. Enters bloodstream quickly and is toxic
Detoxification of Alcohol
Broken down in the hepatocytes
Ethanol-> Ethanal (ethanol dehydrogenase)
Ethanal-> Ethanoate (ethanal dehydrogenase)
2H atoms are removed and combine with coenzyme NAD
Problem with alcohol and fatty acids
If too much alcohol theres not enough NAD to breakdown the fatty acids, so they’re converted back to lipids and stored in hepatocytes.
Liver disease
Scarring of the liver cells causing cell damage and liver failure.
Role of the Kidney
Remove waste products from the blood to produce urine, carried out by the nephrons
Nephrons
Blood enters through the renal artery, which branches into tiny arterioles called AFFERENT Arterioles and enter renal capsule. They divide into a complex called the GLOMERULUS. These merge into the EFFERENT arteriole which eventually become the Renal Vein
Ultrafiltration
The filtration on a micro scale, small molecules are filtered out of the blood and into the lumen of the nephron.
Adaptions for Ultrafiltration
BASEMENT MEMBRANE- acts as a filter, however blood cells and proteins are too big
DIAMETER OF BLOOD VESSELS- The Afferent arteriole has a wider diameter. Builds up hydrostatic pressure
PODOCYTES- Specialised cells with fingerlike projections that allow filtrate to pass beneath cells
CAPILLARY ENDOTHELIUM- Spaces between cells that fluid passes between
Filtrate Composition
Same as plasma, except for larger plasma protein that can’t cross the basement membrane
DEFINITION- Selective Reabsorption
Parts of the filtrate are reabsorbed into the blood i.e. glucose, amino acids
Proximal Convoluted Tubule Cells Structure
Cuboidal epithelial cells with microvilli to increase SA
Lots of mitochondria to provide ATP
Blood capillaries lie close to the surface
Selective Reabsorption Process
- Na-K pumps actively transport sodium out of PCT cells
- A low conc. leads leads to NA ions entering by facilitated diffusion, glucose and amino acids cotransported with NA
- This increases the filtrates water potential
- Water moves down gradient by osmosis
- Urea enters PCT by simple diffusion
- Any large molecules e.g. proteins, reabsorbed by endocytosis
Reabsorption of Water
Water is reabsorbed in via the loop of henle
Loop of Henle
Reabsorbs water from collecting duct
Lowers water potential in the medulla
Shorter in aquatic animals
Descending limb
Narrow
Thin walls
Highly water permeable
Ascending limb
Wider
Thick walls
Impermeable to water
Water reabsorption process
- Na and Cl actively transported out the ascending limb
- Water can’t leave ascending limb
- Water leaves descending limb by osmosis
- Lowest water potential in deepest part of medulla
- Na and Cl diffuse out ascending limb
- Water gradient develops
- Collecting duct is permeable to water
- Water potential in the interstitial region is lowered
Distal Convoluted Tubule
Contains microvilli and mitochondria
The region controls pH, salts under the influence of hormones
Collecting Duct
The tubule fluid contains a lot water
As the tubule fluid passes down the collecting duct, water moves by osmosis into the surrounding medulla where theres a lower water potential, It then enters blood capillaries by osmosis
Desert Mammal Adaptions
Long loop of Henles Oxidise fats rather than carbohydrates Long colon (large intestine) Less sweating Produce dry faeces
Osmoregulation
The control of water and salt levels in the body
Involves kidney, pituitary gland, hypothalamus
How water is gained
Food
Respiration
Drinking water
How water is lost
Urine
Sweat
Faeces
Water vapour
Osmoreceptors
Found in the hypothalamus and monitors blood passing through, they’re sensitive to water potential
Low water potential leads to cell shrinkage as water moves out
Neurosecretory
Produce a hormone called Anti Diuretic Hormone
Produced in the cell Bodies and its secreted into axons, these terminate in the posterior pituitary gland
When stimulated an action potential is sent down axons, ADH is secreted in the posterior pituitary gland
Target cells are in the Collecting duct
How ADH affects the permeability of the Collecting duct
ADH molecules combine with receptors on the membrane of the collecting duct
Activates an enzyme which causes vesicles in the cells to fuse with cell surface membrane (Adenylyl cyclase)
Vesicles contain Aquaporins making membrane more permeable
More water leaves the collecting duct by osmosis
When less ADH, membrane folds inwards to reform vesicles
Aquaporins
The channel’s very narrow so large molecules struggle
A positive charge in the centre will repel positive ions
Kidney Failure Causes
Caused by high blood pressure, diabetes, infection
Glomerular Filtration Rate
Estimate of how much fluid passes into nephrons each minute
Protein in urine also indicates if filtration mechanisms are damaged
Kidney Failure Treatment
DIALYSIS
Waste products, excess fluid, mineral ions are removed from blood by passing it over a partially permeable dialysis membrane.
Substances are exchanged between the fluids
The dialysis fluid contains the correct concentrations
Types of Dialysis
Haemodialysis
Peritoneal dialysis
Haemodialysis
Blood from an artery or vein is passed into a machine containing an artificial dialysis membrane, special shape to increase SA
Heparin is added to avoid clotting
Dialysis fluid flows in the opposite direction
Must be performed in a clinic 3/4 times a week for 3 hours
Peritoneal Dialysis
The dialysis membrane is inside the body’s abdominal membrane
First a surgeon implants a permanent tube into the abdomen
Dialysis solution fills the space then after several hours its drained
This can be done by the patient at home and they can move around
Kidney Transplant
Surgery where a new organ is implanted in the lower abdomen
Immunosuppressant drugs are needed to prevent rejection
Advantages of kidney transplant
Freedom form time consuming dialysis
Feel physically fitter
Improved quality of life- can travel
Disadvantages of Kidney transplant
Need to take immunosuppressant drugs
Major surgery is needed
Need regular checkups to looks for signs of rejection
Side effects of immunosuppressants:
Fluid retention, high blood pressure, become susceptible to infection
Pregnancy Testing
Pregnant women produce the hormone HCG in the placenta
Mobile monoclonal antibodies attach the HCG, have a blue pigment
This moves down the stick with HCG acting as an antigen due to its complementary shape
HCG then binds to the immobilised antibodies and a blue line forms
Left over monoclonal antibodies continue to another fixing site producing a control line
Anabolic Steroids
Stimulate the development and growth of tissues such as muscle
Used as a performance enhancer to increase muscle mass
