3.3.2 Gas Exchange Flashcards

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1
Q

FISH:

Explain how the gills allow efficient gas exchange

A
  • The lamellae provide a large surface area
  • Thin epithelium so a short diffusion pathway
  • Counter-current flow maintains the concentration gradient across whole length of lamellae
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2
Q

FISH:

Explain how the highly folded structures of the gill (lamellae) increase the efficiency of gas exchange

A

They increase the surface area over which diffusion can take place

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3
Q

FISH:

Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish.

A

Water and blood flow in opposite directions.
This maintains a concentration gradient across the gill (as there is always a higher concentration of oxygen in the water than blood)

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4
Q

Name the process by which carbon dioxide is removed from a single celled organism

A

Simple diffusion over the body surface

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5
Q

INSECTS:

Explain how the tracheal system limits the size of the insect

A

Because it relies on diffusion to bring oxygen to respiring tissues.
If insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs

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6
Q

INSECTS:

Give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects.

A
  • Insects have spiracles that can close to reduce water loss

* Insects have sunken spiracles that trap moist air

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7
Q

Describe and explain ways in which plants limit water loss.

A
  • Plants have a waxy cuticle which prevents the evaporation of water;
  • Plants have hairs on their surface that trap moist air reducing the water potential gradient
  • Plants have sunken stomata which again traps moist air reducing the water potential gradient
  • The stomata can close which reduces evaporation
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8
Q

How can you calculate pulmonary ventilation rate?

A

= tidal volume (dm3) x breathing rate (min-1)

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9
Q

LEAVES:

Explain why less water is lost by a plant when the air is humid.

A

Humidity reduces the difference in concentration of water between the plant and the air.
Reduced concentration gradient = less water loss

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10
Q

During an asthma attack, less oxygen diffuses into the blood from the alveoli.
 Explain why.

A

Asthma attacks narrow the airways, so not as much oxygen reaches the alveoli.
This means that there is a small concentration gradient (between blood and alveoli) so rate of diffusion is lower

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11
Q

What are xerophytes?

A

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

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12
Q

Give examples of how xerophytes limit water loss

A
  • Thick cuticle
  • Waxy cuticle
  • Rolled up leaves
  • Hairy leaves
  • Stomata in pits or grooves
  • A reduced surface area to volume ratio
  • Deep roots
  • Sunken stomata
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13
Q

XEROPHYTES:

Explain how having rolled up leaves reduces water loss

A
  • Traps a region of still air within the rolled leaf.
  • The trapped region has a high water potential.
  • As there is no water potential gradient between the inside and outside of the leaf there is no water loss
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14
Q

XEROPHYTES:

Explain how having hairy leaves reduces water loss

A
  • Traps still, moist air next to the leaf surface.

- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.

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15
Q

XEROPHYTES:

Explain how having stomata in pits or grooves reduces water loss

A
  • It traps still, moist air next to the leaf surface.

- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.

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16
Q

Explain why water is always lost from the gas exchange surfaces of terrestrial organisms

A
  • Gas exchange surfaces are permeable.

- And there is a higher concentration of water molecules inside the animal than outside water will diffuse out.

17
Q

Why does every cell inside an insect have a short diffusion distance?

A

They are only a short distance from the tracheae or the tracheoles

18
Q

INSECTS:

Name the tiny pores on the body surface of insects

A

Spiracles

19
Q

INSECTS:

For much of the time the spiracles are (open or closed)

A

Closed, to prevent water loss

20
Q

INSECTS:

Periodically spiracles must open. Why?

A

To allow gas exchange

21
Q

FISH:

What happens if blood and water flow in parallel?

A
  • Diffusion of oxygen into the blood is less efficient - (only 50%)
  • Equilibrium is reached as the conc. gradient cannot be maintained along the whole filament
22
Q

XEROPHYTES:

How can a reduced SA : Vol ratio in leaves be achieved?

A

eg. Leaves are reduced to pine needles

23
Q

LUNGS:

Starting with nose/mouth, list the structures that air passes through

A

Trachea - bronchi - bronchioles - alveoli

24
Q

LUNGS:

What prevents the trachea from collapsing?

A

Rings of cartilage

25
Q

LUNGS:

List the adaptations of the alveoli that make it ideal for gas exchange

A
Single layer of epithelium cells
Stretch as breathe in
Spring back as breathe out
Huge SA
Moist
Rich blood supply
26
Q

LUNGS:

What happens to the intercostals as we breathe in

A

External contract

Internal relax

27
Q

LUNGS:

What happens to the rib cage and the diaphragm before we inhale

A

Ribs - move up and out

Diaphragm - contracts and moves down

28
Q

LUNGS:

What happens to the volume and pressure of the thorax before we inhale air

A

Volume increases

Pressure decreases

29
Q

LUNGS:

What is the ‘tidal volume’?

A

The volume of air we breath in and out at rest (typically about 0.5dm3)

30
Q
LUNGS:
List the events of 
a) Intercostal Muscles
b) ribs
c) Diaphragm
                                                            When we exhale
A

a) Internal contract, external relax
b) Ribs move down and in
c) Diaphragm relaxes, domes up

31
Q

LUNGS:

Typically, what is the normal ventilation rate?

A

12-20 breaths per min

32
Q

Describe the gross structure of the human gas exchange system

A

Trachea - Bronchi - Bronchioles - alveoli

33
Q

Describe how we breathe IN

A

Diaphragm contracts
External intercostal muscles contract
Volume increases and pressure decreases in thorax
Air moves into lungs

34
Q

Describe how we breathe OUT

A

Diaphragm relaxes
Internal intercostal muscles contract
Volume decreases and pressure increases in thorax
Air moves out of the lungs

35
Q

describe the pathway of an oxygen molecule from alveolus to blood

A

crosses the single cell alveolar epithelium and then epithelium of the capillary

36
Q

describe ONE feature of the alveolus that allows efficient gas exchange

A

ONE CELL thick therefore creating a SHORTER diffusion pathway