Flowering Plants
2.67 Understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf.
The metabolic processes are respiration and photosynthesis.
Photosynthesis:
CO2 + H2O > C6H12O6 + O2 Thats is carbon dioxide + water > glucose + oxygen The glucose is used for energy and oxygen is a waste product. This leaves the leaf through the stomata. |
Respiration:
C6H12O6 + O2 > H2O + CO2 + atp Thats glucose + oxygen > water + carbon dioxide + energy The carbon dioxide is a waste product. This is excreted from the leaf through the stomata. |
Humans
2.68 Recall that the lungs, kidneys and skin are organs of excretion.
Skin
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Lungs
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Kidneys
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2.69 Understand how the kidney carries out its roles of excretion and osmoregulation.
Excretion
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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. |
2.70 Describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra.
2.71 Describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct.
Nephrons: A tubular structures within the kidneys which carry out filtration.
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2.72 Describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate.
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2.73 Understand that water is reabsorbed into the blood from the collecting duct.
- As components travel through the nephron some are reabsorbed into the blood.
- This is because they are needed by the body.
- Much of the water is reabsorbed to avoid dehydration.
- This happens in the collecting duct.
2.74 Understand that selective reabsorption of glucose occurs at the proximal convoluted tubule.
- 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.
2.75 Describe the role of ADH in regulating the water content of the blood.
- Excess or lack of water is detected by the hypothalamus in the brain,
- This 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;
- The kidneys increase the amount of water that is reabsorbed into the blood stream.
- The urine is then more concentrated with a lower volume of urea.
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.
2.76 Understand that urine contains water, urea and salts.
Urine is made up of waste products in the body that can be harmful if not excreted.
This includes:
This includes:
- Water,
- Urea
- Salts.