2 i) excretion

Question 1

2.56 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

Answer 1

The metabolic processes are respiration and photosynthesis.
Photosynthesis is CO2 + H2O > C6H12O6 + O2 thats carbon dioxide plus water becomes glucose and oxygen- the glucose is used for energy and oxygen is a waste product, it leaves the leaf through the stomata.
Respiration is C6H12O6 + O2 > H2O + CO2 + atp thats glucose + oxygen > water + carbon dioxide + energy- carbon dioxide is a waste product and is excreted from the leaf through the stomata.

Question 2

2.57 understand that the lungs, kidneys and skin are organs of excretion

Answer 2

Lungs
- Carbon dioxide- a waster product from respiring cells- is diffused into the lungs and then breathed out.

Kidneys
- Excess water, urea (amino acids) and salts are diffused into the kidneys.

Skin
- Water and salts are excreted through the skin.

Question 3

2.58 understand how the kidney carries out its roles of excretion and of osmoregulation

Answer 3

Excretion
- amino acids contain nitrogen- which is toxic to the body- the liver converts it into urea. The kidneys filter urea from the blood stream and combine it with water to create urine which then moves into the bladder.

Osmoregulation
- The kidneys react to ADH hormone released by the pituitary gland. If there is too little water ADH will be released and the kidneys will reabsorb water so that it can stay in the body. If there is too much water then less ADH is released and the kidneys reabsorb less water, so it is lost in urine.

Question 4

2.59 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

Answer 4

Waste or excess products are filtered from the blood stream by the kidneys, ureters carries urine to the bladder, the urine then leaves the body through the urethra.

Question 5

2.60 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct

Answer 5

Nephrons are tubular structures within the kidneys which carry out filtration.
The blood enters into the glomerulus in the Bowman’s capsule, this is where the blood is filtered to create a filtrate of water, glucose, salts and urea (among other things). This then travels through convoluted tubules, here some components are reabsorbed into the blood stream. The loop of Henlé s where water is where water and sodium chloride and reabsorbed into the blood stream. The filtrate then travels down the collecting duct which transports it to the ‘renal pelvis’ after which it goes down the ureters to the bladder.

This video is very useful: http://www.youtube.com/watch?feature=player_embedded&v=vNvZaGcLzEo#!

Question 6

2.61 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

Answer 6

Blood arrives in Bowman’s casual under the high pressure of an artery, it travels it to the glomerulus where the pressure is further increased (as the tubes are smaller). Components of the blood are forced out of the blood vessel into the glomerulus due to the high pressure, creating glomerulas filtrate (water, slats ect.)

Question 7

2.62 understand that water is reabsorbed into the blood from the collecting duct

Answer 7

As components travel through the nephron some are reabsorbed into the blood- as they are needed by the body. Much water of reabsorbed to avoid dehydration. This happens in the collecting duct.

Question 8

2.63 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule

Answer 8

Glucose is a component of golmerula filtrate. Some of the glucose in this filtrate is reabsorbed into the blood stream as it is needed by the body. The first section of convoluted tubules (before the henle loop) is the proximal convoluted tubule, in this area glucose is removed from the nephron and taken back into the blood.

Question 9

2.64 describe the role of ADH in regulating the water content of the blood

Answer 9

Excess or lack of water is detected by the hypothalamus in the brain, it causes the pituitary gland to produce Anti-diuretic hormone, or ADH. This hormone then travels through the blood stream to the kidneys, when it reaches them the kidneys lower the amount of water that is excreted by the body, and increase the amount of water that is reabsorbed into the blood stream. The urine is then more concentrated with a lower volume.
If there is too much water the levels of ADH are lowered and the opposite effects happen, resulting with a more dilute urine and less water in the blood.

Question 10

2.65 understand that urine contains water, urea and salts.

Answer 10

Urine is made up of waste products in the body that can be harmful if not excreted Among other things this includes water, urea and salts.