4.5.3.3 Maintaining Water and Nitrogen Balance in the Body

Question 1

What is osmoregulation

Answer 1

• control of water levels and mineral salts in blood

Question 2

Why are water levels and mineral salts controlled?

Answer 2

• to protect cells
• by stopping to much water from entering or leaving them as concentration of both are the same inside and outside of cells
• won’t function effectively if too much is gained or lost

Question 3

What happens if water concentration is too high outside?

Answer 3

• water enters cells by osmosis
• cells may burst

Question 4

What happens if water concentration is too low outside?

Answer 4

• water will leave by osmosis
• cells may shrivel

Question 5

How is osmoregulation similar in plants?

Answer 5

• full: cell walls are turgid/firm
• lose: become flaccid, cytoplasm shrinks away from cell wall

Question 6

How are water, ions and urea lost in the body?

Answer 6

• urine from kidneys
• sweat from skin
• water vapour from lungs during exhalation?

Question 7

How are water, ions and urea lost in the body by urine?

Answer 7

• kidneys are organs of urinary system

Question 8

How are water, ions and urea lost in the body by sweat?

Answer 8

• sweat contains water, ions and urea
• when sweat is produced, they are lost
• cannot control levels lost

Question 9

How are water, ions and urea lost in the body by exhalation?

Answer 9

• water leaves body during exhalation as well as carbon dioxide
• cannot controls levels lost

Question 10

What does the digestion of excess proteins from the diet result in?

Answer 10

• excess amino acids
• need to excreted safely

Question 11

What does the liver do with amino acids?

Answer 11

• deanimates them to form ammonia after being transported from small intestine
• urea is also produced

Question 12

Why does ammonia need to excreted immediately?

Answer 12

• it is toxic so it needs to converted to urea

Question 13

How is blood transported to the kidneys?

Answer 13

• through renal artery

Question 14

How is blood transported back to the circulatory system?

Answer 14

• through renal vein

Question 15

What is the function of kidneys in maintaining water balance of the body?

Answer 15

• they produce urine (which helps maintain the balance)
• urine contains water, urea and salts

Question 16

What is urea?

Answer 16

• main waste product remove in urine as it is not reabsorbed in kidney

Question 17

What is a nephron?

Answer 17

• filtering unit
• made of a tubule
• responsible for removing urea, excess water and mineral ions from blood

Question 18

What are the different stages which a kidney goes through to produce urine?

Answer 18

• filtration
• selective reabsorption
• formation of urine

Question 19

What happens during filtration?

Answer 19

• blood passed through nephron to inside kidneys
• blood under high pressure at start of nephron, aids ultrafiltration of blood
• small molecules (ureas, water, ions, glucose) filted out and into nephron tubule
• large molecules (proteins) too big to fit through capillary wall and stay in blood

Question 20

What happens during selective reabsorption?

Answer 20

• kidneys reabsorb molecules which are needed, let the other pass out in urine
• all of glucose reabsorbed
• as much water as needed reabsorbed (balance of water level in plasma)
• as many ions as needed reabsorbed (balance of mineral ions in plasma)

Question 21

What happens during the formation of urine?

Answer 21

• molecules which aren’t selectively reabsorbed continue along tubule as urine and pass down to bladder

Question 22

Why is the hypothalamus important in water balance?

Answer 22

• detects changes in concentration in blood plasma

Question 23

Why is the pituitary gland important in water balance?

Answer 23

• regulates release of anti-diuretic hormone (ADH)

Question 24

What happens when the hypothalamus detects a high concentration of blood (less water)?

Answer 24

• pituitary gland releases more ADH
• ADH makes kidney tubules more permeable (more water can go through)
• more water is reabsorbed back into blood
• urine is more concentrated (less water in it)

Question 25

What happens when the hypothalamus detects a low concentration of blood (more water)?

Answer 25

• pituitary gland releases less ADH
• ADH makes kidney tubules less permeable (less water can go through)
• less water is reabsorbed back into blood
• urine is less concentrated (more water in it)