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iGCSE Biology > Excretion > Flashcards

Excretion Flashcards

1
Q

Define excretion

A

removal of metabolic waste

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2
Q

What is metabolic waste?

A

products of reactions that have no use in the human body

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3
Q

Why is excretion important?

A

some products of reactions can be toxic

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4
Q

Give examples of toxic products of reactions

A

urea
carbon dioxide

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5
Q

How is co2 produced?

A

respiration

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6
Q

How is urea produced?

A

deamination

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7
Q

Where is co2 produced?

A

respiring cells

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8
Q

Where is urea produced?

A

liver cells

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9
Q

Where is co2 removed?

A

lungs via blood plasma

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10
Q

Where is urea removed?

A

kidneys and skin

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11
Q

Describe the structure of the kidney

A

cortex
medulla
pelvis
1000s of nephrons

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12
Q

What is deamination?

A

break down of amino acids that produces carbohydrates

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13
Q

What are the carbohydrates produced in deamination?

A

glucose - respiration
ammonia - toxic - urea

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14
Q

Describe the process of deamination

A
  1. amino acids filtered into liver by hepatic artery
  2. amino acids broken down
  3. carbohydrates produced (glucose, ammonia)
  4. ammonia converted into urea (less toxic)
  5. amino acids and urea back into blood stream by hepatic vein
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15
Q

Why is ammonia converted into urea?

A

less toxic

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16
Q

Why are the amino acids broken down into carbohydrates in deamination?

A

body cannot store excess amino acids

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17
Q

What is the kidney?

A

organ that filters blood

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18
Q

What processes happen in the nephron?

A

ultrafiltration
selective reabsorption
water reabsorption

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19
Q

What does the nephron contain?

A

glomerulus
bowman’s capsule
pct
loop of henle
dct
collecting duct

20
Q

What is ultrafiltration?

A

process that filters blood into the glomerulus at high pressures to form glomerular filtrate

21
Q

What is the glomerular filtrate made of?

A

water, urea, amino acids and glucose

22
Q

How is a high pressure created in the glomerulus?

A

afferent arteriole has larger diameter at entrance of glomerulus compared to efferent arteriole at exit

23
Q

What is the Bowman’s capsule?

A

collection of capillaries

24
Q

What is the glomerulus?

A

where glomerular filtrate is created

25
Q

What does the high pressure in the glomerulus mean for the glomerular filtrate?

A

only small molecules can move from the capillaries in the glomerulus into the Bowman’s capsule
large molecules cannot cross the basement membrane

26
Q

Which large molecules cannot enter the glomerular filtrate?

A

red blood cells
white blood cells
proteins

27
Q

What is selective reabsorption?

A

selective uptake of useful substances like glucose, water and amino acids

28
Q

Where does selective reabsorption happen?

A

proximal convoluted tubule

29
Q

How is the pct adapted for selective reabsoption?

A

mitochondria
microvilli

30
Q

Why does the pct have lots of mitochondria?

A

respiration
makes ATP
for active transport
glucose and amino acids move against conc gradient - want to absorb all

31
Q

Why does the pct have lots of microvilli?

A

increases surface area
increases rate of diffusion and active transport

32
Q

Which processes transport glucose, amino acids and salts out of the pct?

A

active transport
diffusion

33
Q

Why does water move out of the pct during selective reabsorption?

A

glucose and amino acids are removed so water potential is increasing in pct
water moves by osmosis down conc gradient
water follows glucose and amino acids

34
Q

What happens in the loop of Henle?

A

concentration of urine

35
Q

What happens in the collecting duct?

A

water reabsorption

36
Q

Describe how the loop of henle concentrates urine

A

salts and ions selectively reabsorbed
water potential increases
water moves by osmosis down conc gradient
water follows

37
Q

What is the role of ADH?

A

makes collecting duct more permeable by making small holes in it

38
Q

How does ADH respond to the body being dehydrated?

A

more holes
reabsorb as much water as possible
= osmoregulation

39
Q

What is in urine?

A

urea
water
some salts

40
Q

What is in blood plasma?

A

glucose
urea
water
some salts
red blood cells
white blood cells
protein

41
Q

What is osmoregulation?

A

collecting duct responding to ADH
absorbing as much water as possible because of dehydration

42
Q

ureter

A

tubes that carry urine from the kidneys to the bladder

43
Q

urethra

A

tube that carries urine from the bladder out of the body

44
Q

Give two advantages of having a kidney transplant rather than treatment by dialysis

A

dialysis - regular hospital treatements
transplant - continuous, no build-up

45
Q

Give two possible disadvantages of having a kidney transplant.

A

rejected by other tissues - foreign object
infection

iGCSE Biology (20 decks)

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