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AQA A-Level Biology > Y1: Exchange > Flashcards

Y1: Exchange Flashcards

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1
Q

How do single-celled organisms exchange gases?

A
  • oxygen is absorbed by diffusion across body surface (only covered by cell surface member)
  • CO2 diffuses out the same way

They have large SA:V ratio

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2
Q

Gas exchange in insects: Describe the tracheal system

Name components

A
  • Trachea
  • Tracheoles
  • Spiracles
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3
Q

Gas exchange in insects: What are trachea?

2

A

main tube thing

-supported by rings to prevent collapse

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4
Q

Gas exchange in insects: What are tracheoles?

3

A

smaller branches off trachea

  • extend throughout all body tissues
  • air is brought direct to tissues due to short diffusion distance
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5
Q

Gas exchange in insects: What are spiracles?

4

A
  • Tiny pores on body surface (beginning of trachea)
  • open and close via valve
  • open for gas exchange
  • close to prevent water loss
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6
Q

Gas exchange in insects: name 3 ways gas moves within the tracheal system

A
  • Diffusion gradient
  • Mass transport
  • H2O filled tracheal ends
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7
Q

Gas exchange in insects: explain how gas moves by diffusion gradient

O2 and CO2?
3 each

A
  • Oxygen used up by respiring cells
  • Low conc at tracheole ends
  • > conc gradient in
  • CO2 produced
  • High conc at tracheole ends
  • > conc gradient out
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8
Q

Gas exchange in insects: explain how gas moves by mass transport
2

A
  • Muscle contraction can squeeze trachea

- -> mass movements of air in and out

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9
Q

Gas exchange in insects: explain how gas moves by H2O filled tracheole ends

5

A
  • Muscle respires (anaerobic) producing lactase
  • soluble so dissolves and lowers water potential of muscle cells
  • -> water moves into muscle cells via osmosis and out of tracheole
  • -> decreases water so draws more air to ends
  • -> diffusion is quicker in air so inc rate into cells and inc h2o evaporation
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10
Q

Gas exchange in insects: Limitations?

4

A
  • Relie on diffusion to exchange gases
  • Needs short diffusion distance to be effective
  • -> insects must be small
  • -> length of diffusion pathway limits insect size
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11
Q

Gas exchange in fish: features that affect gas exchange?
4
and conclusion

A
  • fish are water-proof
  • gas-tight
  • outer covering
  • have small SA:V ratio
  • –>t4 have to have gills as surface cannot supply and remove respiratory gases
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12
Q

Gas exchange in fish: structure of the gills?

4

A
  • on body, behind head
  • made up gill filaments
  • stacked
  • have lots of gill lamellae at right angles to filaments to increase surface area
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13
Q

Gas exchange in fish: how does it work?

3
not explaining countercurrent flow

A
  • Water is taken in through the mouth
  • its forced over the gills and out through an opening in body
  • countercurrent flow: water and blood in opposite directions for max gas exchange
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14
Q

Gas exchange in fish: countercurrent flow?

How does it work?

5

A
  • Blood and water flow in opposite directions
  • Blood with high oxygen conc meets water but water has higher oxygen conc
  • t4 oxygen moves down conc gradient
  • As flows flow, oxygen gets less in water in blood and also water but always higher in water
  • t4 diffusion gradient always maintained across gill lamellae
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15
Q

Gas exchange in plants: what happens to some of the products of respiration?

How does this affect gas exchange?

A
  • CO2 used for photosynthesis and vice versa

- T4 exchange depends on balance between rate of respiration and photosynthesis

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16
Q

Gas exchange in plants: describe structure
from top to bottom

5

A 
upper leaf surface
upper epidermis
mesophyll cells (air spaces)
lower epidermis (stomata)
lower leaf surface
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17
Q

Gas exchange in plants: how is there short diffusion distance and fast diffusion?

3

A

short diffusion distance and fast diffusion

  • no living cell is far from external air
  • diffusion in the gas phase which is more rapid
  • air spaces have a very large surface area compared to volume of living tissue
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18
Q

Gas exchange in plants: what are some adpatations that help short diffusion distance and fast diffusion?

3 plus explainations

A
  • Stomata:
  • ->many small pores, no cell far from stomata, short diffusion distance
  • Interconnecting air spaces between mesophyll
  • ->gases easily in contact w/ mesophyll
  • Mesophyll
  • –>large SA for rapid diffusion
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19
Q

Gas exchange in plants: what are stomata?
5
Structure to function?

A
  • Miniature pores on underside of leaves
  • each surrounded by 2 guard cells
  • guard cells open and close stomatal pore
  • to control rate of gas exchange
  • close to prevent water loss
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20
Q

Gas exchange in plants: what are xerophytes?

2

A
  • Plants that have evolved/adapted to live in very dry environments (little water)
  • have adaptations to reduce water loss eg: small SA
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21
Q

Limiting water loss: why are terrestrial insect adaptations needed?
3

A
  • Terrestrial: live on land
  • t4 water easily evaporates
  • they have a thin, permeable surface with a large area
  • need to balance preventing water loss w/ respiration needs
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22
Q

Limiting water loss: what are 3 terrestrial insect adaptations?

A
  • Small SA:V ratio to minimise area for water loss
  • Waterproof coverings- outer chitin skeleton
  • Spiracles close at rest to prevent water loss
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23
Q

Limiting water loss: what are 5 leaf adaptations to prevent water loss?

A
  • Thick cuticle
  • Rolled up leaves
  • Needle leaves
  • Hairy leaves
  • Sunken stomata
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24
Q

Limiting water loss: why cant leaves limit water loss like insects?
1

A

-Can’t have small SA:V ratio as photosynthesis needs large SA for light and exchanging gases

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25
Q

Limiting water loss: how does a thick cuticle prevent water loss?
1

A

-Thick cuticle means less water can escape

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26
Q

Limiting water loss: how does rolled leaves prevent water loss?
3

A
  • Rolling protects lower epidermis from outside (stomata)
  • Traps still moist air next to leave surface
  • reduces water potential gradient so less water loss by evaporatio
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27
Q

Limiting water loss: how does hairy leaves prevent water loss?
2

A
  • Traps still moist air next to leave surface

- reduces water potential gradient so less water loss by evaporation

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28
Q

Limiting water loss: how does sunken stomata prevent water loss?
2

A
  • Traps still moist air next to leave surface

- reduces water potential gradient so less water loss by evaporation

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29
Q

Limiting water loss: how does decreased SA:V ratio prevent water loss?
3

A
  • small, circular leaves (like pine needles)
  • Decrease water loss bc less surface for water to evaporate from
  • Balanced against need for sufficient area for photosynthesis
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30
Q

Human gas exchange: Why is the breathing system large and in the body?

2
2

A

Large system:

  • Large organisms w/ lots of cells
  • Maintain high body temp (metabolic + resp rate)

Inside:

  • Air is not dense enough to support structures
  • prevent water loss
31
Q

Human gas exchange: describe inspiration

7

A
  1. diaphragm contracts and flattens
  2. external intercostal muscles contract
  3. internal intercostal muscles relax
  4. ribs move up and out
  5. volume of thorax increases
  6. pressure inside thorax decreases
  7. air moves in down pressure gradient
32
Q

Human gas exchange: is inspiration active or passive?

A

Active

33
Q

Human gas exchange: describe expiration

7

A
  1. diaphragm relaxes and comes upward
  2. external intercostal muscles relax
  3. internal intercostal muscles contract
  4. ribs move in and down
  5. volume of thorax decreases
  6. pressure inside thorax increases
  7. air moves out down pressure gradient
34
Q

Human gas exchange: is expiration active or passive?

A

Passive

35
Q

Human gas exchange: Describe human gas exchange pathway

5

A 
Sinuses
Trachea
Bronchi
Bronchiole
Alveoli
36
Q

Human gas exchange: What is the Pleura?

A

Membrane that covers lungs

37
Q

Human gas exchange: What is the pulmonary ventilation equation?

A

Pulmonary ventilation = tidal volume x ventilation rate

38
Q

Human gas exchange: What is the tidal volume?

A

Air taken in by one normal breath at rest

39
Q

Human gas exchange: What is the ventilation rate?

A

Number of breaths per minute

40
Q

Human gas exchange: Key features in the trachea and bronchi?

3

A

Cartilage
Ciliated epithelium
Goblet cells

41
Q

Human gas exchange: cartilage in trachea and bronchi structure to function?
1

A

Prevents trachea from collapsing a air pressure decreases

42
Q

Human gas exchange: ciliated epithelium in trachea and bronchi structure to function?
1

A

Waft mucus out of lungs (trap dirt)

43
Q

Human gas exchange: goblet cells in trachea and bronchi structure to function?
2

A

Secrete mucus to protect mucus membrane

Traps dirt and pathogens

44
Q

Human gas exchange: smooth muscle in bronchioles structure to function?
1

A

Contracts to control flow of air in and out of alveoli

45
Q

Human gas exchange: Key features in the alveoli?

4

A

They are tiny
Collagen/elastic fibres
Squamous epithelium
Rich blood supply

46
Q

Human gas exchange: effect of having tiny alveoli?

1

A

Large SA:V ratio for increased gas exchange rate

47
Q

Human gas exchange: collagen in alveoli structure to function?
1

A

Allow alveoli to stretch as they fill w/ air and spring back to expel CO2 rich air

48
Q

Human gas exchange: squamous epithelium in alveoli structure to function?
2

A

Facilitates selective diffusion of gases

Increases surface area

49
Q

Human gas exchange: rich blood supply in alveoli structure to function?
1

A

Maintains conc gradient for constant diffusion

50
Q

Human gas exchange: explain how having a network of narrow pulmonary capillaries around the alveoli means rapid diffusion?

4 and explainations

A

-Red blood cells slow through capillaries due to narrowness
> more time for diffusion
-short diffusion distance between alveoli air and red blood cells bc flat
-thin walls of alveoli and capillaries
>short diffusion distance
-Alveoli and capillaries have large total surface area
-Blood flow to maintain conc gradient

51
Q

Human gas exchange: explain how breathing movements means rapid diffusion?
3

A

They ventilate lungs
heart circulates blood around alveoli
steep conc gradient

52
Q

Human gas exchange: what are 5 risk factors for lung disease?

A 
Smoking
Air pollution
Genetic
Infections
Occupation (chemicals)
53
Q

Human gas exchange: structure of alveoli?

A
  • Alveoli walls are one cell thick
  • Capillaries run outside walls
  • Inside alveolus, air space
  • Site of gas exchange = epithelium of alveoli
54
Q

Enzymes and digestion: What is physical digestion? what is it useful for?

A
  • Eg: teeth, food churned by muscles in stomach

- Large surface area for chemical digestion

55
Q

Enzymes and digestion: What is chemical digestion?

A
  • Hydrolyse large insoluble molecules by enzymes (hydrolysis)
  • Multiple enzymes to break down different sections
56
Q

Enzymes and digestion: products of digestion of carbohydrates?

A

monosaccarides

57
Q

Enzymes and digestion: products of digestion of lipids?

A

Glycerol and fatty acids

58
Q

Enzymes and digestion: products of digestion of proteins?

A

Amino acids

59
Q

Enzymes and digestion: process of lipid digestion?

2

A
  1. Split into micelles by bile salts in the liver to increase surface area
  2. Lipases in the pancreas hydrolyse ester bonds
60
Q

Enzymes and digestion: process of Carbohydrate digestion?

starch to alpha glucose

7

A
  1. saliva (salivary glands) mix w. food (chewing)
  2. salivary amylase hydrolyses alternative glycosidic bonds of starch (mineral salts for op. pH)
    >maltose (disaccaride)
  3. stomach acids denatures amylase
  4. pancreatic amylase (pancreatic juice) do starch->maltose (alkaline salts for op. PH)
  5. muscles in wall of ileum push food
  6. epithelium lining contains maltase (membrane-bound discaccaridase)
  7. maltose–> alpha glucose
61
Q

Enzymes and digestion: process of carbohydrate digestion?
Sucrose
2

A
  1. sucrase hydrolyses single glycosidic bond

2. forms glucose and fructose

62
Q

Enzymes and digestion: process of carbohydrate digestion?
Lactose
2

A
  1. Lactase hydrolyses single glycosidic bond

2. Forms glucose and galactose

63
Q

Enzymes and digestion: process of protein digestion?

3 main types!!

A
  1. endopeptidases: hydrolyse peptide bonds between amino acids in central region of protein
    >forms series of peptide molecules
  2. exopeptidases: hydrolyse peptide bonds from ends
    >forms dipeptides and single amino acids
  3. dipeptidases: hydrolyses peptide bonds between 2 amino acids of dipeptides
    -dipeptides are membrane bound in epithelial cell in ileum
64
Q

Enzymes and digestion: describe structure of ileum and how it increases rate of diffusion

4

A
  1. walls folded into villi and microvilli on ep. lining cells
    - > increase SA for diffusion
  2. Thin walls between epithelium cells and capillaries
    - >short diffusion distance
  3. muscle mixes contents
    - > maintain diffusion gradient
  4. blood vessels surrounding
    - >carry away absorbed molecules to maintain diffusion gradient
65
Q

Enzymes and digestion: oesophagus role and structural adaptation?
2

A
  • Tube that carries food from mouth to stomach

- Smooth muscle to aid peristalsis

66
Q

Enzymes and digestion: stomach role and structural adaptation?
4

A
  • Muscular sac that is able to secrete acid, mucus and proteases
  • Involved in mechanical and chemical digestion
  • Smooth muscle to aid peristalsis
  • Goblet cells secrete thick mucus that protects lining
67
Q

Enzymes and digestion: large intestine role and structural adaptation?
2

A
  • Absorbs water

- Smooth muscle to aid peristalsis

68
Q

Enzymes and digestion: rectum role and structural adaptation?
2

A
  • Stores faeces containing waste products and food that hasn’t been digested
  • Storage until socially acceptable time for defecation
69
Q

Enzymes and digestion: Salivary glands role and structural adaptation?
2

A
  • Secrete amylases which hydrolyses starch into maltose

- Found near mouth to begin chemical digestion early

70
Q

Enzymes and digestion: pancreas role and structural adaptation?
2

A
  • Produces ‘pancreatic juice’ containing proteases, lipase and amylase
  • Contains a duct that empties into the ileum at the start for efficient digestion
71
Q

Enzymes and digestion: amino acid and monosaccharide absorption?
2

A

Diffusion

Co-transport

72
Q

Enzymes and digestion: triglyceride absorption process?

Into epithelial cells
4

A
  1. bile salts=forms micelles
  2. movement in ileum means micelles contact with ep cells lining villi
  3. micelles break down to release monoglycerides and fatty acids
  4. they are non-polar so they diffuse into epithelial cells
73
Q

Enzymes and digestion: triglyceride absorption process?

From ep. cells into body cells

6

A
  1. MG and FA go to endoplasmic reticulum to reform into triglycerides
  2. golgi adds cholesterol and lipoproteins to form chylomicrons (special particles adapted to transport lipids)
  3. chylomicrons leave by exocytosis
  4. enter lymphatic capillaries (lacteals) at centre of each villus to enter the blood system
  5. triglycerides in chylomicrons hydrolysed by enzyme in ep. cells of blood capillaries
  6. diffuse into cells
74
Q

Enzymes and digestion: triglyceride absorption process?

Formation of micelles

4

A
  1. Bile salts have a lipophilic (lipid-soluble and hydrophobic) end and a lipophobic (and hydrophilic) end
  2. arrange in fat droplets w/ lipophobic ends poking out
  3. prevents fat droplets ticking together so only small micelles
  4. when they reach ep. cells the bile salts break down releasing fatty acids for absorption

AQA A-Level Biology (11 decks)

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