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Exchange > Chapter 6: Exchange > Flashcards

Chapter 6: Exchange Flashcards

1
Q

Features of specialised exchange surfaces

A
  • Very thin (short diffusion distance).
  • Selectively permeable
  • Large surface area to volume ratio
  • Movement if the environmental medium (to maintain diffusion gradient)
  • Transport system to ensure the movement of the internal medium (to maintain diffusion gradient)
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2
Q

Equation for diffusion

A

SA X Difference in conc.
/
Length of diffusion path.

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3
Q

Gas exchange in single called organisms

A

They have a large SA to V ratio.

Oxygen is absorbed by diffusion across their body surface and carbon dioxide diffuses out across their body surface.

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4
Q

What are the three ways in which respiratory gases move in and out of the tracheal system?

A
  • Along diffusion gradient.
  • Mass transport.
  • Ends of tracheoles are filled with water.
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5
Q

How does water enter and leave the tracheae?

A

Through tiny spores called spiracles.

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6
Q

How do spiracles work?

A

Opened and closed by a valve.

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7
Q

What are the limitations of the tracheal system?

A

-Relies mostly on diffusion.
So short diffusion path needed. Therefore, insects are small. The diffusion pathway limits the size that insects can attain.

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8
Q

What is the gas exchange in insects?

A

They have evolved tracheae.

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9
Q

What are the tracheae supported by?

A

Strengthened rings.

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10
Q

What do tracheae divide into?

A

Dead end tubules called tracheoles.

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11
Q

How do respiratory gases move in and out of the tracheal system along a diffusion gradient?

A

(1) When cells respire, and so oxygen is used up. It’s concentration towards the ends of the tracheoles falls.
(2) This creates a diffusion gradient. This causes oxygen to diffuse from the atmosphere, along the tracheae and tracheoles to cells.
(3) Carbon dioxide is produced by cells during respiration.
(4) This creates a diffusion gradient in the opposite direction.
(5) This causes carbon dioxide to diffuse along the tracheoles, and trachea to the atmosphere.

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12
Q

Is diffusion quicker in gas or liquid?

A

Gas.

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13
Q

How do respiratory gases move in and out of the tracheal system by mass transport?

A

(1) Contraction of muscles in insects squeeze the trachea enabling mass movements of air in and out.

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14
Q

How do respiratory gases move in and out of the tracheal system when the ends of the tracheoles are filed with water?

A

(1) During major activity the muscle cells around tracheoles carry out anaerobic respiration.
(2) This produces lactate. This is soluble and lowers the water potential.
(3) So water moves into cells from the tracheoles by osmosis.
(4) The water in the ends of the tracheoles decreases in volume and in doing so draws air further into them.
(5) This means final diffusion pathway is in gas phase, not liquid and so more quicker. This increases rate at which air moves into tracheoles.

BUT LEADS TO GREATER WATER EVAPORATION.

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15
Q

What is the structure of the gills?

A

Gills are made up of gill filaments, at right angles to them are gill lamellae. This increases surface area of the gills.

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16
Q

What is countercurrent flow?

A

The flow of water and blood is in opposite directions.

17
Q

What does the countercurrent exchange principle ensure that?

A
  • Blood that is well loaded with oxygen meets water, which has its maximum concentration of oxygen. So oxygen diffuses from the water to the blood.
  • Blood with little oxygen meets water which has most oxygen removed. Diffusion occurs from the water to blood.
18
Q

What would occur with parallel flow?

A

Diffusion gradient is only maintained for half the distance across the gill lamellae. So only half of the oxygen diffuses from the water into the blood.

19
Q

What adaptions do leaves have for rapid diffusion?

A
  • Large surface area of mesophyll cells for rapid diffusion.
  • Many stomata.
  • Numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells.
20
Q

How is the gas exchange in plants similar to that of insects?

A
  • Diffusion occurs in gas phase.

- No living cell is far from external air.

21
Q

Where is the majority of stomata located?

A

Underside of leaf.

22
Q

What happens when water loss would be excessive?

A

The stomata close.

23
Q

What is each stroma surrounded by?

A

Pair of guard cells.

24
Q

How do terrestrial organisms lose water?

A

By evaporation.

25
Q

Which features of an efficient gas exchange conflict with the need to conserve water?

A

Thin, permeable and large area.

26
Q

What adaptation shave insects evolved to reduce water loss?

A

Small surface area to volume ratio.
Waterproof coverings.
Spiracles.

THIS MEANS AN INSECT HAS A INTERNAL NETWORK OF TUBES INSTEAD OF USING BODY SURFACE TO DIFFUSE GASES.

27
Q

What are xerophytes?

A

Plants which are adapted to living in areas where water is in short supply.

28
Q

Modifications of leaves where rate of water loss is high.

A
  • Thick cuticle. E.g. Holly
  • Rolling up of leaves= Protects lower epidermis and so traps region of still air. This area has high water potential so there is no gradient. E.g. Marram grass
  • Hairy leaves= Traps still, moist air next to leaf surface so reduced gradient. E.g. Type of heather plant.
  • Stomata in pits or grooves= Trap still, moist air next to leaf surface and reduce gradient. E.g. Pine trees.
  • Reduced surface area to volume ratio of leaves.
29
Q

Why are lungs located on the inside of the body?

A

Air is not dense enough to support and protect the delicate structures.
Body would lose a lot of water.

30
Q

Describe the process of inspiration.

A

(1) External intercostal muscles contract, internal intercostal muscles relax.
(2) Ribs move upwards and outward, increasing the volume of the thorax.
(3) The diaphragm contracts, causing it to flatten. This also increases the volume of the thorax.
(4) An increase in volume means there is a decrease of pressure.
(5) As a result, atmospheric pressure is now greater than pulmonary pressure and so air is forced into the lungs.

31
Q

Describe the process of expiration.

A

(1) Internal intercostal muscles contract, external intercostal muscles relax.
(2) Ribs move downwards and inwards, decreasing the volume of the thorax.
(3) Diaphragm relaxes and bulges upwards. This further decreases the volume of the thorax.
(4) Decreased the volume of the thorax means the pressure increases.
(5) Pulmonary pressure is greater than atmospheric pressure, so air forced out of lungs.

32
Q

Ventilation definition.

A

Movement of air in and out of the lungs.

33
Q

Pulmonary ventilation rate calculation (dm^3min^-1) =

A

Tidal volume (dm^3) X Breathing rate (min^-1)

34
Q

What are the main parts of the human gas exchange?

A 
Lungs
Trachea
Bronchi
Bronchioles 
Alveoli
35
Q

Why is diffusion between the alveoli and the blood very rapid?

A
  • Red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion.
  • Blood flow through pulmonary capillaries maintains a conc. gradient.
  • Alveoli and pulmonary capillaries have a large total SA.
  • Always a steep concentration gradient due to constant ventilation.
36
Q

What are the two stages of digestion?

A

Physical breakdown.

Chemical breakdown.

37
Q

What is physical breakdown?

A

Larger pieces breakdown into smaller pieces by teeth.
This provides larger surface area for chemical digestion and makes it possible to ingest food.
Food is churned in stomach and this physically breaks it up.

38
Q

Three types of digestive enzymes.

A

Carbohydrases: Hydrolyse carbohydrates to monosaccharides.

Lipases: Hydrolyse lipids into glycerol and fatty acids.

Proteases: Hydrolyse proteins to amino acids.

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