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A2 - Bio - Exc
Excretion
| Question | Answer |
|---|---|
| Define the word Excretion | The removal of metabolic waste from the body, of bi products or unwanted substances from normal cell procedures. |
| What does metabolic waste consist of | Waste substances that may be toxic or are produced in excess by reactions inside the cell |
| What is Egestion and how does it differ to excrection | The release of unused materials such as faeces, excretion is the removal of bi-products of chemical reactions such as sweat, urine and CO2. Products of egestion never entered the cell therefore they arent excreted |
| Define the process of deamination | A reaction that breaks down amino acids, it is the removal of the amine group from an amino acid to produce ammonia |
| Name two waste products that are produced in large ammounts in the body | Urea and CO2 |
| Where is CO2 Produced | During respiration as a bi product |
| How is CO2 Excreted | CO2 binds to the Haemoglobin in red blood cells and is transported to the lungs where it dissociates with the red blood cells and is exhaled in the lungs |
| How is Urea produced | Through the process of Deamination, where an amino acid is broken down into keto acid and ammonia |
| What compound is formed when CO2 binds with HB | Carbaminohaemoglobin |
| Why is it important to remove CO2 from the body (6) | - Will compete with oxygen on HB, lowering oxygen carrying potential. - Has a higher affinity for HB then O2, meaning HB will be taken up - A build up of Carbonic acid, will alter the ph of the blood effecting enzyme action. |
| Explain how nitrogrenous compounds are excreted from the body | Amino acids are broken down via the process of deamination, into keto acid and ammonia. The ammonia is converted into urea. |
| Where is Urea Produced | In the liver from the excess amino acids |
| What disease can emphysema, chronic bronchitis, asthma or severe pneumonia cause | Respiratory acidosis |
| What is respiratory acidosis | the combination of co2 with water forms carbonic acid. this dissociates releasing hydrogen ions. hydrogen ions lower the ph of the blood and increase its acidity lowering the ph to below 7.35 |
| What is a ph buffer | a ph buffer is protein found in the blood that detects the ph changes in the blood and signals the medulla oblongata to increase breathing rate |
| why are nitrogenous compounds such as amino acids not simple excreted in excess ammounts | The amino acid contains almost as much energy as a carbohydrate. So excreting it would be a waste of potential energy. |
| Where are amino acids broken down | in the liver and undergo deamination |
| Why is ammonia converted into urea | Urea is a far less toxic and less soluble compound then ammonia and therefore is safer to store in the body |
| What is a liver cell also known as | A hepatocyte |
| Why does the liver need a good flow of blood | as it requires a large supply of oxygen for respiration, blood from the intestines also is rich in nutrients that need distribution and potentially high in toxins that need to be filtered. |
| What blood vessel connects the aorta to the liver | The hepatic artery |
| What blood vessel connects the small intestines with the liver | The hepatic portal vein |
| What blood vessel connects the liver to the vena cava | The hepatic vein |
| Which container holds all the bile formed in the liver | the gall bladder |
| Which vessel joins carries bile from the lobules to the gall bladder | the bile duct |
| What is a sinusoid | This a small vessel that is the meeting point of the hepatic artery and the portal vein, here oxygenated blood mixes with nutrient rich blood from the intestines. The hepatocyes lining the sinusoid remove or add molecules to the passing blood stream |
| Where is bile manufactured and where in the lobule is it sent | In the liver cells, and up the bile duct branch. |
| Why do the liver cells have many microvilli on their surface | these increase the surface area of the liver cells for endo and exocytosis |
| What are some functions of the liver cell | Protein synthesis, storage and transformation of carbohydrates, synthesis of cholesterol and bile salts and detoxification |
| What is a kupffer cell | Specialized macrophages that sit in the end of the sinusoid, their function is to absorb old red blood cells that are close to cell death. They break down hb releasing bilirubin, which is excreted in the bile and pigments faeces brown |
| What is the ornathine cycle | The detoxification of ammonia forming urea, ammonia produced during the deamination of excess amino acids |
| How is ammonia generated for this Ornathine cycle | Through deamnination, the amino acid is split into ammonia and keto acid through the addition of oxygen |
| describe how citruline is formed in the ornathine cycle | ammonia is combined with CO2 forming a compound that dissociates into H2O and citruline |
| what happens to citruline in the ornathine cycle | The citruline gets ammonia added to it which forms argenine and H2O, H2O is then reintroduced to the argenine forming Urea and Ornathine |
| Where happens to urea after it is reintroduced to the blood stream | the kidneys accept the urea, concentrate it into urine and store it in the bladder for excretion |
| What is detoxification | This is the conversion of toxic molecules to less toxic or non toxic molecules |
| What does catalase do | This is a detoxification enzyme that has a sizable turnover rate, hydrogen peroxide into water and oxygen (can detoxify 5 million hydrogen peroxide molecules in one minute) |
| What is ethanol broken down into and by what enzyme | Ethenal, by the ethanal deyhydrogenase enzyme |
| What is ethenal broken down into, by what enzyme and what happens to the products | Ethenal is broken down into ethanoate (acetate) by the ethenal dehydrogenase enzyme, this combines with coenzyme A to form acetyle coenzyme A which is used in the link reaction to carry acetate to the kreb cycle |
| What occurs if during the break down of alcohol there is a deficiency of NAD or a lack of NAD | NAD is used during the detoxification of alcohol, without this molecule the fatty acids are converted into lipids and stored in the hepatocytes, this causes the liver cell to enlarge forming the condition known as fatty liver |
| What is Fatty liver | When the you consume more alcohol then the liver can detoxify, the fatty acids in the alcohol are stored as lipids in the liver cells enlarging then. if |
| What is the renal Artery | The Artery that carries blood oxygenated blood to the Kidneys |
| What is the renal vein | This vein carries deoxygenated, filtered blood from away from the kidney |
| What is the Nephron | This is a small tubule that receives fluid from the blood and converts it into urine. |
| What is the glomerulus | This is a fine network of capillaries that increases the local blood blood pressure to squeeze fluid out of the blood. |
| What is ultrafiltration | This the process of fluid in the blood being pushed out of the Glomerulus and into the bowmans capsule |
| What is the bowmans capsule | This is a cup shaped structure that surrounds the glomerulus and catches any fluid pushed out of the glomerulus through ultra filtration |
| What are the four parts of the nephron | - The proximal convoluted tubule - Loop of henle - Distal Convoluted Tubule - Collecting duct |
| What is selective Reabsorption | The process of certain tissues in the Nephron reabsorbing molecules in the fluid back into the capillaries surrounding the tubule. What is left in the collecting duct is Urine and is passed into the pelvis and down the ureter to the bladder |
| What does the proximal convoluted tubule absorb Through selective reabsorbtion | All sugars, some salts and water (85%) of reabsorption occurs here |
| What occurs in the descending limb in the loop of henle | The water potential is lowered by the addition of salts and removal of water |
| What occurs in the ascending limb, in the loop of henle | the water potential is increased by the removal of salts by active transport |
| What occurs in the collecting duct | The water potential is decreased again by the removal of water, this ensures the urine has a low water potential, meaning a high concentration of solutes then is found in the the blood and tissue fluid. |
| What tissues are found in the glomerulus | - Capillary Epithelium - Basement Membrane - Podocytes (Epithelial cells of the bowmans capsule) |
| Whats the difference between afferent and efferent vessels | The afferent vessels bring blood to an organ, where as efferent vessels take blood away from it. |
| What cellular tissue is involved in the majority of ultra filtration and why | The basement tissue found between the capillary tissue and the podocytes, consist of a fine mesh of collagen fibres and glycoproteins. This mesh blocks any molecule with a RMM of 69000. (stops most proteins and red blood cells) |
| Why are the podocytes specialised | They contain many finger like projections known as major processes that ensure gaps between the cells to allow fluid to pass into the tubules |
| What is filtered out of the blood | Water, amino acids, glucose, urea and inorganics like potassium, chloride and sodium |
| Why are the contents left in the blood ater ultrafiltration important for selective reabsorption | The blood will contain many proteins, this means the water potential will be very low ensuring some fluid are maintained and water will travel in to the blood via osmosis later in the filtration process. |
| Why do the epithelial cells of the proximial convoluted tubule have microvilli | This increases the surface area for reabsorbtion |
| What doe the co-transported proteins in the walls of the proximal convoluted tubule do | They transported glucose, amino acids and sodium ions from the tububle into the cell through facilitated diffusion |
| What property does the opposite membrane of cell have, found close to the tissue fluid and blood capillaries. | This is also folded heavily to increase surface area. this also contains many sodium / potassium pumps that pump sodium ions into the blood and pump potassium ions into the cell |
| Why does the proximal convoluted tubule epithelial cell contain many mitochondria | This indicates that the cell has a high energy requirement, or processes that require a large amount of atp |
| what is facilitated diffusion | diffusion that is enhanced by the action of proteins in the cell membrane. |
| What do the sodium - potassium pumps | these are specialized proteins in the cell surface membrane that actively transport sodium and potassium ions against their concentration gradients. |
| What is osmoregulation | The control of water and salt levels in the body. |
| Why does water need to be regulated in the body | Water levels need to be balanced between cells and the surrounding fluids must be maintained to prevent problems with osmosis |
| Where do we gain water from | - food - drink - Metabolic respiration |
| Where do we lose water | - urine - sweat - water vapor in exhaled air - Faeces |
| if its a cool day and you consume a lot of water, what will the water concentration of your urine be like | more quantities of less concentrated urine will be produced |
| if its a hot day and you consume very little water, what will the water concentration of your urine be like | Lower quantities of highly concentrated urine will be produced |
| What is ADH | Anti Diuretic Hormone |
| What does the hormone ADH do | This is a chemical messenger that when the body detects that water levels in the blood are low, is released to make the walls of the collecting duct more or less permeable when reabsorbing water in kidneys |
| Where is the ADH created. | In the posterior pituitary gland, within neurosecretory cells |
| What is an osmoreceptor and where is it found | A receptor that detect water levels in the blood, and is found in the hypothalamus |
| What is a neurosecretory cell | A cell found in the brain that acts as a neuroreceptor but stimulates the production of ADH |
| What transport channel is more permeable to water molecules | Aquaporins |
| ADH has a half life of 20 minutes, what does this mean? | The half life is the time it takes for the hormones concentration in the blood to half |
| What occurs in the body if the water potential is too high in the blood | - Hypothalamus detects too much water in the blood - Nueurosectory cells create and secrete less ADH into the blood - less ADH binds to walls of Collecting duct and stimulate less aquaporins to bind to the walls of the CD, reabsorbing less water |
| What occurs in the body if the water potential is too low in the blood | - Hypothalamus detects low water levels in the blood - Nueurosectory cells create and secrete more ADH into the blood - more ADH binds to walls of Collecting duct and stimulate more aquaporins to bind to the walls of the CD, reabsorbing more water |
| What are some common causes for kidney failure | Diatbetes Mellitus, Hypertention and infections |
| Why is kidney failure a bad thing | The body will be unable to remove, excess water, salts and waste products from the blood stream, leading to a toxin related death |
| What are the two treatments for Kidney failure | Dialysis and a kidney transplant |
| How does dialysis work | Blood is pumped across a membrane that mimics the nephron that absorb any salts, urea etc that are in excess and allows the rest of the blood to return to the body. This is combined with a strict diet |
| What are the two types of Dialysis | Haemodialysis and Peritoneal Dialysis |
| What occurs in Peritoneal Dialysis | A surgeon implants a tube in the abdomen, dialysis is poured into and fills the space between their organs and abdomen, after a few hours this fluid is drained. This is done several times a day. |
| What occurs in Haemodialyss | Blood from a vein is passed into the machine that has the artificial nephron like membrane. This is done three time a week for several hours. |
| What occurs during a kidney transplant | Old kidneys are left unless they are infectious or cancerous. While under general anaesthetic the patient is implanted with the new kidney and is supplied blood from the circulatory system and is connected to the bladder |
| What are some disadvantages of Dialysis treatment | - Time consuming - Limited diet - Lower quality of life - General feeling of sickness - Categorized as terminally ill |
| What are some disadvantages of translant treatment | - Major surgery requires general anaesthetic - Frequent checks - Surgery risks like infection, bleeding and surrounding damage to organs - Immunosuppressent drug side effects like fluid retention, high blood pressure and infection |
| Why are immunosuprresents used during a kidney transplant | These drugs are used to stop the body from identifying the transplanted organ as a foreign body that needs to be destroyed, and lowers chance of rejection |
Created by:
delldom
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