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3. Exchange of substances > Exchange > Flashcards

Exchange Flashcards

1
Q

Why do small organisms not need a specialised exchange surface?

A

have a very high SA:Vol so diffuse all oxygen in through membrane

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2
Q

State ficks law

A

rate of diffusion = (surface area * difference in conc.) / length of diffusion pathway

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3
Q

Exchange in single celled organism

A
  • small w/ large SA:Vol
  • O2 + CO2 diffuse across one cell thick membrane
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4
Q

Describe respiration in the tracheal system

A
  • oxygen used for respiration
  • conc. gradient set up btw. atmosphere (high) and cells (low)
  • oxygen diffuses in through spiracle + tracheae
  • muscle contraction pumps gases through
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5
Q

Explain why tracheoles filled w/ water

A

So that during exercise (anaerobic respiration), water moves into cells by osmosis due to water. pot gradient set up by lactate. This draws air into tracheoles in which diffusion takes place more rapidly

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6
Q

List adaptations of insects for efficient gas exchange

A
  • tracheoles thin walls -> short diff. path
  • highly branched -> short diff. path + large SA
  • tracheae tubes filled w/ air -> faster diffusion in air
  • fluid moves into tissues from tracheoles -> more air
    for fast diff. + larger SA
  • abdominal pumping -> maintains conc. gradient
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7
Q

Features of fish gills for efficiency

A
  • v. large SA -> flat filaments w/ lamellae folds
  • thin walled/flat -> close contact water, short diff. path
  • good blood circulation -> conc. gradient maintained
  • water ventilation -> conc. gradient maintained
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8
Q

Concurrent vs Countercurrent

A

Concurrent: same direction of flow so equilibrium reached, half O2 taken up
Countercurrent: opposite direction of flow so conc. gradient maintained, 100% O2 taken up

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9
Q

Adaptations of leaves for gas exchange

A
  • many stomata -> short diff. path as no cell is far
  • many air spaces in mesophyll -> gases readily in contact w/ mesophyll cells
  • large SA of mesophyll cells -> rapid diff.
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10
Q

Respiration formula

A

oxygen + glucose -> carbon dioxide + water

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11
Q

Photosynthesis formula

A

carbon dioxide + water -> glucose + oxygen

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12
Q

Adaptations to limit water loss in insects

A
  • small SA:V ratio -> minimise area of water loss
  • waterproof covering (chitin) covered in waterproof cuticle
  • spiracles close -> reduce water loss
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13
Q

Adaptations to limit water loss in plants (xerophytes)

A
  • thick cuticle forms waterproof barrier
  • rolling up of leaves -> region of still air becomes saturated w/ H2O decreasing water pot. gradient
  • hairy leaves/stomata in pits -> trap moist air next to leaf reducing water pot. gradient
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14
Q

Why are lungs needed?

A

Remove lots of CO2 and absorb lots of O2

-> humans have lots of cells and high metabolic rate

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15
Q

Pathway of air in the lungs (plus a feature)

A

trachea (cartilage to prevent collapse)
bronchi (mucus trap dirt + cilia waft it up to throat)
bronchioles (muscle lined to control air flow)
alveoli (elastic fibres allow them to stretch and recoil)

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16
Q

Process of inspiration (active)

A
  • external ic contract, internal ic relax
  • ribs pulled up and out as thorax vol. increases
  • diaphragm contracts increasing vol. of thorax
    further
  • less air pressure in lungs
  • air forced in as atmospheric pres. > pulmonary pres.
17
Q

Process of expiration (largely passive)

A
  • internal ic contract, external ic relax
  • vol. of thorax decrease as ribs move in and down
  • diaphragm relaxes, is pushed up by contents of
    abdomen decreasing vol. of thorax further
  • more air pressure in lungs
  • air forced out as pulmonary pres. > atmospheric pres.

note: under normal breathing, recoil of elastic tissue main reason for air being forced out

18
Q

Why is diffusion rapid btw. alveoli and capillaries?

A
  • r.b cells slowed in cap’s -> more time for diffusion
  • thin endothelium which r. b cells flattened against + thin epithelium -> short diff. pathway
  • alveoli + p.capillaries have large SA
  • constant ventilation of air + blood maintains conc.
    gradient
19
Q

Risk factors for lung disease (COPD)

A 
smoking
air pollution
genetic make-up
infections
occupation
20
Q

Order of digestive tract

A

mouth, pharynx, oesophagus, stomach, ileum, colon, rectum

21
Q

2 stages of digestion

A

Physical - food broken down into smaller pieces to be ingested
Chemical - hydrolysis of insoluble mols into smaller soluble ones using enzymes

22
Q

Examples of carbohydrases

A

amylase (starch)
maltase (maltose)
sucrase (sucrose)
lactase (lactose)

23
Q

Carbohydrate digestion

A
  • sal. amylase hydrolyses starch -> maltose + minerals salts maintain optimum pH
  • acids in stomach denature amylase + stop hydrolysis
  • amylase from pancreatic juice in ileum mixes w/ food, resumes hydrolysis + contains alkaline salts to
    maintain neutral pH
  • muscle lining pushes food along ileum, epithelial lining produces membrane-bound maltase
  • maltose hydrolysed into a.glucose
24
Q

Lipid digestion

A
  • lipids split into micelles by bile salts in emulsification -> increases SA so lipase action sped up
  • lipase from pancreas hydrolyses ester bond in triglycerides to form monoglycerides and f. acids
25
Q

Protein digestion

A

Large complex mols hydrolysed by different peptidases.

  • endopeptidases hydrolyse pep. bonds in central region creating many mols
  • exopeptidases hydrolyse pep. bonds on terminal end of a.acids releasing a.acids + dipeptides
  • dipeptidases hydrolyse bond in dipeptide (membrane-bound)
26
Q

Where are products of digestion absorbed?

A

In the ileum: folded + possesses villi

27
Q

Features of villi for absorption

A

thin walls, large SA, good blood supply etc.

  • muscle to mix contents of ileum, maintain diffusion gradient
  • epithelial cells contain microvilli, further increasing SA
28
Q

Describe processes involved in absorption of products of lipid digestion from ileum to lymph vessels

A
  • micelles contain bile salts + f. acids
  • these make f.acids + m.glycerides more soluble in water
  • products absorbed by diffusion into epithelium
  • triglycerides reformed in ep. cells
  • chylomicrons move out of cell by exocytosis into lymphatic capillaries

3. Exchange of substances (4 decks)

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