Excretion

Question 1

Why can some waste products damage the cells ?

Answer 1

Because they are toxic

Question 2

What is the removal of toxic substances called ?

Answer 2

Excretion

Question 3

Is faeces excretion?

Answer 3

NO , excretion is only waste products of cells !

Question 4

What waste products does respiration create ?

Answer 4

CO2 and H2O

Question 5

What waste products does photosynthesis create ?

Answer 5

O2

Question 6

Where are the waste products of respiration and photosynthesis excreted through in a plant ?

Answer 6

Stomata in the leaf

Question 7

How do humans get rid of H2O a waste product of respiration ?

Answer 7

Sweating

Question 8

How do you humans get rid of carbon dioxide which is a waste product of respiration?

Answer 8

Using gaseous exchange in the lungs and then breathing out the air

Question 9

What happens if carbon dioxide is not excreted from a human ?

Answer 9

The plot turns toxic, lowering the pH, creating a weak acid. This week acid can damage cells

Question 10

What happens if water is not excreted from a human?

Answer 10

Excess water can affect the osmotic potential of the plasma

Question 11

What toxic waste substance is created by the breakdown of amino acid in the liver ?

Answer 11

Urea

Question 12

What is another word for the breakdown of amino acid’s?

Answer 12

Deamonation

Question 13

Why is urea created?

Answer 13

Because humans cannot store excess amino acid’s like we can with carbohydrates and lipids. Therefore excess amino acids need to be broken down, however what they are broken down into is toxic and must be removed from the body

Question 14

How is urea removed from the body ?

Answer 14

Via the kidney and skin

Question 15

How are waste products transported ?

Answer 15

In the bloods, plasma

Question 16

Order of urea formation

Answer 16

• amino acids are filtered into the liver along with the rest of the blood via the hepatic artery
• Excess amino acid’s cannot be stored and need to be broken down so they can be excreted. They are broken down into carbohydrates and ammonia
• ammonia is very toxic and must be broken down into a slightly less toxic chemical called Urea
• amino acids that are needed and the urea are released back into the blood stream via the hepatic vein

Question 17

What do the kidneys do ?

Answer 17

Filter the blood and remove any excess materials and passes them to the bladder to be excreted

Question 18

What are the three main sections of the kidney?

Answer 18

• cortex - at the top and lighter coloured
• medulla - triangular and in the middle
• pelvis - is at the centre

Question 19

What are the structures that filter the blood in the kidney called ?

Answer 19

Nephrons

Question 20

Describe stage one at the nephron

- ultrafiltration

Answer 20

• The size of the artery at the exit of the glomerous is smaller than the entrance, this creates a buildup of pressure
• this pressure forces small molecules by diffusion, such as urea, glucose, amino acid’s and salts across into the Bowmans capsule and form the glomerular filtrate
• larger molecules like proteins or red blood cells are too big to fit across and therefore stay in the blood

Question 21

Stage two of the nephron-selective reabsorption

Answer 21

• from the Bowmans capsule the filtrate travels to the proximal convoluted tubule, however it has a lot of useful material such as glucose which would be wasted unless they were recovered
• there are specialised cells within the walls of the PCT, which pump useful materials back into the blood stream via active transport
• all of the glucose is reabsorbed here along with 80 percent of the water

Question 22

Stage three of the nephron-water reabsorption

Answer 22

• there is still some water needed to be reabsorbed
• your kidneys will filter 180 L of fluid a day but you only produce 1.5 L of year-end per day
• loop of Henle and collecting duct are both involved in reabsorption of water if it’s needed
• if you have lost a lot of water through sweat I haven’t drunk anything nobody will try to re-absorb as much water from the filtrate as it can. This makes the year and have a lower volume of water and very concentrated, therefore a dark yellow colour
• if you have excess water your urine will contain a high volume of water will be less concentrated, so it will be a paler colour
• The water diffuses out of the loop of Henle because of low water potential of the blood stream by osmosis

Question 23

Stage four at the nephron- ADH

Answer 23

• your body controls water reabsorption by a hormone called anti diuretic hormone (ADH)
• and area in your brain called the hypothalamus monitors the level of water in your blood. If you need to reabsorb more, it tells The pituitary gland to release more ADH
• as ADH is a hormone it travels through the blood. The collecting duct is surrounded by capillaries. The ADH diffuses out of the blood and binds to receptors on the surface of the collecting duct cells. If ADH binds, this triggers the wall of the collecting duct to become more permeable to water. Therefore more is reabsorbed

Question 24

What substances are in the kidneys filtrate ?

Answer 24

Urea, salt and water

Question 25

The path of the filtrate from the kidney

Answer 25

Kidney —> ureter —-> bladder

—-> urethra