Breakdown of metabolic waste, Filtration, Body Temperature (5) Flashcards
what is excretion and why is it important
the removal of waste products of metabolism from an organism eg. CO2 and NH2, NH3
> build up of waste products is often toxic, so excretion is an important elimination process in the body
what is egestion
the removal of undigested substances from an organism. These products have not entered cells and have therefore not been metabolised.
what are the main metabolic waste products in the body
CARBON DIOXIDE
NITROGENOUS WASTE PRODUCTS
why must carbon dioxide be removed from the body
where is it removed from and what is it the waste product of
It is the waste produce of aerobic respiration in all cells.
Excreted from the lungs.
WHY IT MUST BE EXCRETED
- the Bohr effect*
- carbaminohaemoglobin*
- respiratory acidosis*
explain the Bohr effect
when
explain carbaminohaemoglobin
explain respiratory acidosis
explain deamination and what is the product in mammals, fish and birds
+ give the necessary chemical formula
in the liver, excess amino acids are broken down (deaminated) in the liver and excreted by the kidney as urine. In mammals, excess AAs are converted to urea, ammonia in fish (which can withstand the toxicity) and uric acid in birds and insects.
amino acid + oxygen → keto acid + ammonia (very toxic, very soluble)
H2N-C-R-H-COOH + O2 → R-O=C-COOH + NH3
what are the formulae for AMINO ACID
AMMONIA
UREA
where is the liver and what is its overall structure (very basic)
IGNORE how are liver cells specialised
below the diaphragm, the gall bladder is just below it and stores the bile secreted by the liver
connected to the duodenum by the common bile duct
made of several lobes with many lobules containing hepatocytes
which two sources supply the liver with blood
+
how does blood leave the liver
- oxygenated blood supplied by the HEPATIC ARTERY, which branches off the aorta
- deoxygenated blood containing the products of digestion supplied by the digestive organs via the HEPATIC PORTAL VEIN (eg. the spleen, stomach, pancreas, small intestine, colon, rectum)
all the blood leaves via the HEPATIC VEIN (deoxygenated) , which joins the inferior vena cava to return to the heart
what is the histology of a liver lobule
The liver consists of thousands of polygonal blocks (lobules), made of acini, which contain vertical cords of homogenous/structurally undifferentiated hepatocytes and sinusoids, blood vessels and bile canalculi.
The sinusoids are open channels through which blood flows in close contact with the hepatocytes. It flows from the periphery of the lobule, where there are branches of the hepatic artery and the hepatic portal vein, to the centre, where there is a branch of the hepatic vein into which the blood from the liver drains.
Bile flows in the opposite direction, between the cords of cells.
explain the blood supply received by the hepatocytes
Blood from the hepatic artery and hepatic portal vein mix as they flow into the sinusoids, meaning the hepatocytes receive a double supply of blood; oxygenated and containing newly absorbed nutrients from the internal digestive organs.
how is bile moved to the gall bladder
Bile canaliculis are between every two rows of liver cells. They merge to form bile ducts in which the bile is drained from the liver into the gall bladder(storage of bile), and then via the common bile duct to the duodenum.
They run in a countercurrent to the blood vessels and sinusoids i.e. from the centre to the periphery.
which cells line the sinusoids
Kuppfer cells.
macrophages (large phagocytic cell, not WBC), engulfs old RBCs
how are hepatocytes specialised
hepatocytes contain a large quantity of mitochondria, lysosomes, glycogen granules, a prominent golgi apparatus and lipid droplets.
hepatocytes increase the SA of their cell surface membrane with microvilli, increasing surface in contact with blood for gaseous exchange of oxygen and carbon dioxide, and to extract food substances, toxins and metabolic waste
what are the functions of bile, where is it made and stored
made in the liver, stored in the gall bladder
FUNCTION OF BILE
- very alkaline- neutralises stomach acid/stomach chyme
- excretion of the breakdown of haem- bilirubin and biliverdin- excreted in the faeces
- detergent- the emulsification of fats (allowing water to mix with a fat droplet makes the fat smaller/breaks it down so that there is a larger surface area for lipase to break down)
label this micrograph of the liver lobules
State the first five roles of the liver
- FORMATION of BILE- used for 1. fat emulsification 2. excretion of breakdown products of haem 3. neutralisation of acid chyme
- BREAKDOWN of HAEMOGLOBIN- AAs from globin are reused, iron is reused, haem forms bilirubin and biliverdin (bile pigments)
- BREAKDOWN of HORMONES- important homeostatic mechanism eg. remove adrenaline, insulin to revert to dynamic equilibrium within narrow parametres
- STORAGE: vitamins- all fat soluble vitamins and some B group minerals, blood
- DETOXIFICATION
state the second five roles of the liver
- PRODUCTION OF CHOLESTEROL- cholesterol is the precursor of steroid hormones
- PRODUCTION of HEAT- distributed to rest of body by blood
- METABOLISM of CARBOHYDRATES- blood glucose buffering system. Glycogen storage by glycogenesis. Glycogen breakdown by glycogenolysis.
- METABOLISM of FATS- to increase blood-glucose levels by gluconeogenesis. Excess carbohydrate → converted to fats. Fatty acid oxidation (respiration of fats).
- METABOLISM of PROTEINS- 1. plasma protein synthesis 2. transamination 3. deamination- 1st part of urea formation 4. ornithine cycle- 2nd part of urea formation
how is urea formed (2 phases and what happens to the products)
+ chemical formulae
- DEAMINATION
REMOVAL OF AMMONIA FROM AMINO ACIDS WHICH ARE PRESENT IN EXCESS.
amino acid → keto acid + NH3
- Keto acid is used in respiration, ammonia enters the ornithine cycle to form urea*
2. the ORNITHINE CYCLE
FORMATION OF UREA FROM AMMONIA
Urea is less toxic than NH3, can be concentrated and stored in urine before excretion
2 NH3 + CO2 + H2O → 1 UREA + 2H2O
how are excess amino acids metabolised
> USED IN PROTEIN SYNTHESIS
> USED AS A RESPIRATORY SUBSTRATE IN AEROBIC RESPIRATION
> DEAMINATION to keto acid and ammonia; keto acid is used in respired or converted to glycogen; ammonia is used to produce organic nitrogenous bases ATCGU for nucleic acid formation or excreted via the ornithine cycle as urea
what is detoxification
-
TOXINS, either produced or consumed (hydrogen peroxide or alcohol, medicinal and recreational drugs) are converted to less toxic compounds in the liver and excreted by the kidneys.
* Eg. To detoxify ethanol, it is converted to acetyl CoA and can enter the Krebs cycle, using NAD co-enzymes as a substrate.*
* The more alcohol consumed, the more NAD is needed to carry out the oxidation/dehydrogenation reactions, producing reduced NAD.*
suggest what can happen to amino acids in liver cell metabolism
> used in protein synthesis
> as a respiratory substrate in aerobic respiration, entering at the Krebs cycle
> gluconeogenesis to maintain blood glucose levels
> excess amino acids are deaminated to produce ammonia and excreted from the body as urea in the urine
> transamination
> conversion to lipid/fatty acid
what is the structure of the kidney, where is urine transported to and which blood vessels supply the kidney (overview)
The renal cortex, renal medulla, renal pelvis, which connects to the bladder via the ureters.
Urethra secretes urine, connected to bladder, which connects to the kidney via the ureters.
Renal artery brings oxygenated blood from the aorta, and the renal vein removes deoxygenated blood to the inferior vena cava.
what are the pathways of filtrate and blood flow in the nephron
- blood flow:* aorta, renal artery, afferent arteriole to glomerulus, glomerulus capillaries, efferent arteriole from glomerulus, peritubular capillaries, vasa recta, branch of renal vein, inferior vena cava
- filtrate:* Bowman’s capsule, proximal convoluted tubule, descending limb of loop of Henle, ascending limb of loop of Henle, distal convoluted tubule, collecting duct
which are wider/narrower: DCT/PCT + ascending/descending L in LOH
lumen of distal convoluted tubules are larger than narrow proximal convoluted tubules
acsending limb is thicker than the thin-walled descending limb
what is the mechanism for ultrafiltration in the kidney
- HIGH PRESSURE IN THE GLOMERULUS due to the lumen of afferent arteriole > lumen of efferent arteriole causing high hydrostatic pressure in the glomerulus capillaries which forces liquid through the cell membranes from blood plasma to capsule lumen
- All membranes are one cell thick- glomerulus capillaries squamous endothelium, podocytes around capillaries, squamous epithelial cells of Bowman’s capsule,
- SIEVE MECHANISM is a series of structures.
- Endothelium of glomerulus capillaries have fenestration (pores) that increase permeability.
- Cells of the Bowman’s capsule (podocytes) have slit-like pores to increase permeability.
- Between these two tissues is a continuous layer of connective tissue- the basement membrane that prevents the passage of blood cells and plasma proteins. It is a thin, fibrous extra-cellular matrix made of protein fibres and mucopolysaccharides.
what is osmoregulation
the homeostatic control of water potential (U) of blood and tissue fluid
it is regulated by ADH - anti-diuretic hormone - a 9 AA polypeptide
produced by the hypothalamus
secreted into the posterior pituitary by neurosecretion;
- low water potential is detected in the walls of the blood vessels in the hypothalamus*
- in the hypothalamus (nervous tissue) neurosecretory cells release ADH, which travels along the axon of the neurone and is secreted into the posterior pituitary (endocrine tissues)*
what is an aquaporin
a transmembrane protein that forms pores in the membrane of cells which allows rapid passage of water by osmosis
how does ADH affect the concentration and volume of urine
When ADH is present, there is exocytosis of vesicles containing aquaporins as part of their membrane, increasing permeability of the collecting duct membrane to water.
More water is reabsorbed from the filtrate, resulting in CONCENTRATED urine of a decreased volume.
————————————————
When ADH is absent, there is endocytosis of the vesicles containing aquaporins in the collecting duct cells; aquaporins are removed and permeability of the collecting duct membrane to water decreases.
Water is retained in the filtrate, resulting in DILUTE urine of an increased volume.
how is low water potential corrected by osmoregulation
> OSMORECEPTORS in the hypothalamus detect a change in the water potential of the blood.
> If water potential is low, the posterior pituitary is stimulated to release ADH into the blood (neurosecretion).
> ADH is carried to the cells of the collecting duct and increases their permeability to water.
> Water reabsorption into the blood is increased.
what is water potential of the blood affected by
water potential is DECREASED (less water in the blood) by
- high levels of sweating, low levels of drinking
- water is lost in urine, sweat, faeces, breath
water potential is INCREASED (more water in the blood) by
- low levels of sweating, high levels of drinking
- water is gained by drinking, eating, respiration
what are the 3 parts of nephron function and what are the 5 functional structures that perform them (consecutively, following the filtrate/urine) in which half of the nephron do these occur
- ultrafiltration afferent arteriole brings oxygenated blood from the renal artery to the 1. GLOMERULUS/BOWMAN’s CAPSULE and away via the efferent arteriole cortex
- selective reabsorption in the 2. PROXIMAL CONVOLUTED TUBULE, supplied by the capillary network to convoluted tubules cortex
- water conservation in the 3. LOOP OF HENLE, the descending limb- thick and thin, the ascending limb, thin and thick, supplied by the vasa recta capillary, and the 5. COLLECTING DUCT, leading to the bladder medulla
explain what occurs during ULTRAFILTRATION in the BC/G
High hydrostatic pressure due to the wide lumen of the afferent arteriole and narrow lumen of the efferent arteriole forces blood plasma to filter from the blood in the glomerulus capillaries into the filtrate in the Bowman’s capsule, with only small molecules passing through the 3 layers.
- Fluid passes from the glomerulus into the renal tubule by ultrafiltration.*
- It results in very low water potential in the blood of the capillary.*
after ultrafiltration, what is present and absent in the filtrate
filtrate: water, urea, glucose, ions, small proteins, amino acids, some hormones eg. HCG
not in filtrate: most plasma proteins, RBCs and WBCs, platelets, rest of water
how are podocytes adapted to their function
- slit-like pores that enable ultrafiltration by increasing permeability
- flat and thin
- one layer/are one cell thick
which cells line the proximal convoluted tubule/adaptations
CUBOIDAL EPITHELIA
many microvilli to increase SA for reabsorption, mitchondria, golgi apparatus
explain the second half of the ultrafiltration mechanism; sieve mechanism
- SIEVE MECHANISM is a series of structures.
- Endothelium of glomerulus capillaries have fenestration (pores) that increase permeability.
- Cells of the Bowman’s capsule (podocytes) have slit-like pores to increase permeability.
- Between these two tissues is a continuous layer of connective tissue- the basement membrane- that prevents the passage of blood cells and plasma proteins. It is a thin, fibrous extra-cellular matrix made of protein fibres and mucopolysaccharides.
label the following renal tissue
what is a problem with undergoing too much detoxification
To detoxify ethanol, it is converted to acetyl CoA , using NAD co-enzymes as a substrate, and can enter the Krebs cycle.
Fatty acids enter the respiration pathway by being oxidised to acetate, which is converted to acetyl CoA, requiring NAD.
The body prioritises detoxifying ethanol over converting fatty acids to acetyl CoA. Therefore excess consumption leads to an accumulation of fatty acids, which are converted to lipids and stored in the hepatocytes. This leads to alcoholic fatty liver disease and eventually cirrhosis.
what occurs in the PCT (2 marks)
Glucose, amino acids, most of the water and some of the salts are reabsorbed into peritubular capillaries that surround the nephron at this point
which molecules are ‘small molecules’ and ‘large molecules’
SMALL urea, glucose, water, amino acids, vitamins, small proteins
LARGE ions, plasma proteins, RBCs, WBCs
what is the function of the PROXIMAL CONVOLUTED TUBULE
to reabsorb organic compounds from the renal filtrate into the blood in the peritubular capillaries by active transport
compounds reabsorbed: Na+, K+ and other ions, glucose, amino acids, proteins(pinocytosis), water(osmosis)
what is the process for selective reabsorption
- 1. a concentration gradient is set up
- Na+/K+ pumps actively transport Na+ ions from the PCT cells (cuboidal epithelia) into the tissue fluid. The ions diffuse into the lumen of a peritubular capillary.
- This creates a low concentration of Na+ inside the PCT cell, and decreases the water potential inside the cell.
- 2. glucose, amino acids and water can move into the cell and blood
- Na+ ions move down their concentration gradient into the PCT cell by facilitated diffusion, using a co-transporter protein that co-tranports glucose and amino acids into the cell.
- Glucose and amino acids diffuse into the blood plasma in the peritubular capillaries down a concentration gradient, therefore lowering the water potential inside.
- Water will diffuse from the region of high water potential (outside the PCT cell in the PCT lumen) to the region of low water potential (inside the PCT cell) by osmosis. It will then diffuse into the blood plasma down the water potential gradient.
- (Some urea diffuses back into the blood.)
- 3. other substances
- A few proteins are removed from the filtrate by endo/pinocytosis.
- Poisonous substances and nitrogen-containing chemicals eg. creatinine, are actively secreted into the filtrate.
- Filtrate is isotonic with body fluids as it enters the LOH.
which adaptations help the PCT perform its role
- MICROVILLI = HIGH SURFACE AREA- the microvilli are in contact with the filtrate to maximise rate of reabsorption
- SODIUM-POTASSIUM PUMPS- using ATP to actively transport Na+ out of the pct cell in order to set up a conc. grad. across the membrane of the pct cell with the filtrate.
- CO-TRANSPORTER PROTEINS to allow the facilitated diffusion of glucose, aas and Na+ into the pct cell.
- many MITOCHONDRIA = high rate of diffusion; ATP for active transport is necessary to maintain the conc. grad. for Na+to diffuse into the PCT cell.
what is the function of the LOOP OF HENLE and how is it designed to allow the function
- to create an increasing gradient of salt concentration in the medulla, enabling excess water to be withdrawn by osmosis from the urine in the collecting duct.*
- the effect is increased by the countercurrent multiplier*
The filtrate is isotonic with blood plasma at entry to the descending loop
The descending limb is permable to water but relatively impermeable to solutes
The ascending limb is impermeable to water and permeable to salt
what is the process by which an increasing salt gradient is set up in the LOH
1. Na+ and Cl- are actively transported out of the thick part of the ascending limb, increasing concentration of Na+ and Cl in the interstitial fluid.
2. Water potential decreases in the interstitial fluid. Water moves out of the filtrate by osmosis along the descending limb. The filtrate becomes increasingly concentrated along the descending limb because the gradient is maintained. The most concentrated region of the LOH is at the bottom, at approx. 1200mOsm Kg-1.
3. Water enters the blood plasma in the capillaries in the vasa recta. As it leaves, water potential decreases in the filtrate.
4. After the descending limb, the LOH is no longer impermeable to salt/solutes and NaCl diffuses out of the filtrate into the interstitial fluid because the concentration is greater in the filtrate. From the bottom to the top of the ascending limb, the NaCl concentration gradually decreases.
At the entrance to the DCT/end of the LOH, the volume of fluid and concentration of NaCl have both been reduced.
what is the process of the collecting duct
Urine enters the collecting duct after the distal convoluted tubule.
WATER CONSERVATION Water will leave the collecting duct into the medulla tissue depending on the permeability of the cells, regulated by the ADH hormone.
Urine enters the renal pelvis.
what are the types of nephron and the implications of those types
in which mammals are they likely to be found
CORTICAL nephrons have a short loop of Henle and only just extend into the medulla. They function most when water supply is normal-excessive.
JUXTAMEDULLARY nephrons have a long loop of Henle that extend deep into the medulla. They function most when water is in short supply.
- cortical:* aquatic habitats eg. beavers
- cortical & jm:* terrestrial habitats with adequate water supply eg. rabbit
- juxtamedullary:* arid habitat with no water to drink eg. kangaroo rat with longer LOH too
the more arid the habitat, the larger the maximum concentration of urine produced
describe the collecting duct when ADH is present/absent
ADH present:
walls of DCT and CD are permeable to water and urea
water diffuses into the hypotonic medulla, urea escaped, concentrated urine is formed (approx. 1000mOsm kg-1)
ADH absent:
walls of DCT and CD are impermeable to water and urea
> water and urea are retained in the CD and dilute urine is formed (50 mOsm kg-1)
what is the glomerular filtration rate (GFR) and what is the normal value
> an assessment of kidney function; a measure of the volume of fluid passing through the kidney per minute (cm3min-1)
NORMAL VALUE: 90-120 cm3min-1
lower values lead to kidney disease/kidney failure
what are possible effects of kidney infections/high blood pressure
- protein in the urine
- blood cells in the urine
why do kidney infections/high blood pressure cause abnormal urine
Infection causes an increase in permeability in the renal/Bowman’s capsule, due to inflammation
Hypertension increases blood pressure in the glomerulus, causing large proteins to be pushed through the basement membrane
what occurs due to renal failure (7)
- BUILD UP of TOXINS eg. urea
- HIGH blood pressure- extra fluid and salt are not removed from the blood
- pain and stiffness in the JOINTS- due to urice acid accumulation and crystallisation in joints
- LOSS of ELECTROLYTE balance- DCT’s control of ions impaired
- weakened BONES- loss of maintenance of Ca2+ levels
- ANAEMIA- kidneys produce hormone that increases RBC production by bone marrow
- death
how can kidney malfunction be treated
- RENAL DIALYSIS/ RENAL REPLACEMENT THERAPY
- KIDNEY TRANSPLANT
what is DIALYSIS
the artificial removal of waste products and excess fluid from the blood. It requires a carefully controlled diet.
It decreases protein and salt. Fluid intake is controlled.
what is the first type of dialysis
Haemodialysis: involves dialysis machine
a fistula is formed in the patient’s arm; blood flows from the artery directly into the vein.
Blood flows out of dialysis needles into the machine, made of tubes, surrounded by fresh dialysis fluid, COUNTERCURRENT MECHANISM used, purified blood returned to the body
ions and small molecules- sugars, amino acids is prevented by adjusting the concentrations in the dialysate to be the same as in the blood
3x/week, 2-4 hours in hopsital per session
what is the second type of dialysis
PERITONEAL DIALYSIS: the peritoneum (the lining of the abdomen) is selelctively permeable and allows the exchange of substances between the blood and the peritoneal fluid
Dextrose is in the solution to decrease water potential, allowing excess water to diffuse out of the blood. The membrane is not permeable to dextrose)
Permanent tube is surgically placed in abdomen; so can be carried out at home.
what are the differences between haemodialysis and peritoneal dialysis
PD: living membrane, active transport and diffusion can take place, allowing better exchange.
do not have to go to hospital- stay at home
HD: higher chance of infection because the blood leaves the body
anticoagulant is added to prevent blood clotting
what are the problems with KIDNEY TRANSPLANT and how are they overcome (3)
- donor required- # of donors < # needing kidney transplants
- tissue/organ refiction- 1. matching of tissue types 2. recipient given immunosuppressant drugs to decrease immune reaction to foreign organ
- major surgery- under general anaesthetic
name two major diagnostic tests that examine the excretory products in urine samples
the pregnancy test using monoclonal antibodies raised against the pregnancy hormone HCG
gas spectrometry for detection of anabolic steroids in athletes
what occurs when a pregnancy test strip is placed in an urine sample containing HCG molecules
the urine sample is drawn up the test strip
HCG antibodies are complexed with coloured granules
These complexes bind to HCG molecules, if present
immobilised HCG antibodies trap the coloured complexes
a coloured band appears in this window = positive
a coloured band always appears in the control window showing the test has run completely because HCG antibodies trapped by anti-antibodies
how are anabolic steroids discovered in the urine
>An urine sample undergoes gas chromatography/spectrometry
solvent = gas (organic solvent because steroids are lipid-soluble) urine is vaporised
>each substance stay for a specific time= retention time
creates chromatogram
what happens to proteins that are orally consumed
They are hydrolysed in the stomach and intestines by peptidase enzymes into amino acid monomers. Amino acids (not in excess) are filtered into the filtrate in the Bowman’s capsule and reabsorbed in the proximal convoluted tubule into the blood plasma.
Excess AAs are deaminated to ammonia, ornithine cycle to urea and excreted by the urethra/bladder in the urine.
Amino acids can be transaminated, used as a respiratory subtrate at the Krebs cycle or used in protein synthesis.
name + explain briefly the four ways of heat exchange between an organism and its environment
- RADIATION_ the emission of electromagnetic waves- can transfer heat between objects not in direct contact eg. absorbing heat radiating from the Sun
- EVAPORATION\_ the removal of heat from the surface of a liquid losing some molecules as gas eg. sweating-cooling effect
- CONVECTION_ the transfer of heat by movement of air or liquid past a surface
- CONDUCTION\_ direct transfer of heat between molecules in direct contact - lizard sits in cool surface
