excretion in humans

Question 1

Where’s carbon dioxide excreted from?
where’s carbon dioxide produced from?
What happens if CO2 isn’t excreted?

Answer 1

1. lungs
2. CO2 in respiration
3. toxic to cells if not excreted; lowers pH of cells & blood.

Question 2

where’s urea & excess water and ions excreted from?
where is urea produced?

Answer 2

1. kidneys
2. in liver from excess amino acids (deamination)

Question 3

how do plants excrete waste materials?

Answer 3

Daylight hours
* photosynthesis takes place using CO2 they produce in respiration

Night
* plants can’t photosynthesise, they respire. waste product is CO2 through their stomata.

Question 4

how do kidneys excrete?
filtration, ureter, urethra, bladder

Answer 4

• Kidneys work by filtering stuff out the blood under high pressure, then reabsorbing the useful things.
• The urine flows down the ureter, & into the bladder, where it’s stored.
• When sphincter muscle at the entrance to the urethra relaxes, the urine flows out of the body through the urethra
• Final liquid that flows out of nephron is a solution of urea & salts in water. (urine)

Question 5

1.Structure, location, & function of a nephron & its associated blood vessels

Answer 5

Location between the cortex & medulla.

Function where urine is produced.

Structure Glomerulus; sits inside Bowman’s capsule.
* Blood pressure in glomerulus high.
* This forces out smaller molecules from blood into Bowman’s capsule.
* The susbtances forced out of capillaries are: water, glucose, urea, ions.
* This process is known as ultrafiltration.

Question 6

What is selective reabsorption
Formation of urea, excess water, ions

Answer 6

Selective reabsorption
* Some of the substances forced out of glomerulus will be reabsorbed back into the blood, further down the nephron bc they’re useful.
* The nephron absorbs
* All of the glucose
* Some ions
* Most of water
back into the blood. None of the urea is reabsorbed.

What’s left of the filtrate forms urine
Urea, excess water, excess ions

Question 7

What is assimilation?
Where & how does it take place? Give an example of assimilation.

Answer 7

1. digested food molecules converted to other molecules that body will use.
2. Takes place in the liver; e.g assimilation of amino acids by converting them to proteins.

Question 8

what is deamination

Answer 8

the removal of nitrogen-containing part of amino acids, to form urea.

Question 9

what role does liver play in excretion?

Answer 9

1. deamination
2. assimilaton
   e.g amino acids converted to proteins