2 Excretion

Question 1

When are carbon dioxide and oxygen waste products in a leaf?

Answer 1

During respiration, oxygen is useful and carbon dioxide is a waste product.
During photosynthesis, carbon dioxide is useful and oxygen is a waste product.
The waste products are lost via the stomata of a leaf.

Question 2

What is excretion?

Answer 2

the removal of waste products

Question 3

What are the excretory products of the lungs?

Answer 3

Carbon dioxide made from aerobic respiration

Question 4

What are the excretory products of the kidneys?

Answer 4

Urea made from excess protein
removed as urine
Water made from aerobic respiration removed as urine
Ions (salt)

Question 5

What are the excretory products of the skin?

Answer 5

Water made from aerobic respiration removed as sweat

Question 6

PAPER 2 How does the kidney carry out excretion?

Answer 6

Ultrafiltration, Reabsorption and Releasing waste into bladder where it is stored before being released via the urethra

Question 7

PAPER 2 How does the kidney carry out osmoregulation?

Answer 7

Water is excreted by the kidneys in the urine.

Question 8

PAPER 2 What is part of the urinary system?

Answer 8

aorta
vena cava
renal artery
renal vein
kidneys
ureter
bladder
sphincter
urethra

Question 9

PAPER 2 What is part of the nephron?

Answer 9

bowman’s capsule
glomerulus
proximal convoluted tubule
loop of henle
distal convoluted tubule
collecting duct

Question 10

PAPER 2 What is ultrafiltration?

Answer 10

renal artery flows through glomerulus
glomerulus filters out large molecules like proteins and blood cells so they stay in blood and don’t go in nephron
high pressure built up which squeezes small molecules (water, urea, ions, glucose) out of blood and into bowman’s capsule
this is called filtrate

Question 11

PAPER 2 Where does ultrafiltration occur?

Answer 11

Bowman’s capsule

Question 12

PAPER 2 What is the composition of glomerular filtrate?

Answer 12

water
salts/ions
glucose
amino acids
urea

Question 13

PAPER 2 How is water reabsorbed into the blood from the collecting duct?

Answer 13

Water is reabsorbed into blood via osmosis
Collecting duct is affected by ADH which makes the collecting duct more permeable so more water is reabsorbed into the blood
This is called osmoregulation

Question 14

PAPER 2 What gland releases ADH?

Answer 14

pituitary gland

Question 15

PAPER 2 What is osmoregulation controlled by?

Answer 15

negative feedback. If water gets too high or low, mechanism triggered that brings it back to normal

Question 16

PAPER 2 What is selective reabsorption?

Answer 16

Glucose is reabsorbed from proximal convoluted tubule via active transport so it can be used in respiration
Sufficient ions are reabsorbed but excess ions aren’t

Question 17

PAPER 2 What does urine contain?

Answer 17

Urea
Ions/salts
Water

Question 18

PAPER 2 What makes urine more concentrated?

Answer 18

If you have lost a lot of water through sweating or haven’t drank enough
body will try and reabsorb as much water from the filtrate as it can.
This makes the urine very concentrated, with a lower volume of water and therefore is a darker browner colour.