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A-level Biology Year 1 > Gas Exchange > Flashcards

Gas Exchange Flashcards

1
Q

What is equation for rate of diffusion?

A

(surface area x difference in concentration) / thickness of surface

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2
Q

What is the path oxygen takes in the lungs?

A

Trachea -> bronchi -> bronchioles -> alveoli -> across alveolar epithelium -> capillary/blood

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3
Q

How does inhalation occur?

A
  • Internal intercostal muscles relax
  • Ribcage moves outwards
  • Diaphragm contracts and moves down
  • Lung volume increases
  • Pressure decreases and air moves into the lungs down the pressure gradient
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4
Q

How does exhalation occur?

A
  • Internal intercostal muscles contract
  • Ribcage moves inwards
  • Diaphragm relaxes and moves up
  • Lung volume decreases
  • Pressure increases and air moves out the lungs down the pressure gradient
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5
Q

Why is alveoli a good exchange surface?

A
  • Single cell thick epithelium -> short diffusion pathway
  • Constant blood supply -> concentration gradient always maintained
  • Many alveoli -> large surface area for diffusion
  • Moist walls -> dissolves gases and facilitates diffusion
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6
Q

How do you calculate pulmonary ventilation?

A

PVR = tidal volume x breathing rate

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7
Q

What is pulmonary ventilation?

A

The amount of air exchanged in one breathing cycle

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8
Q

Why do larger organisms need to have specialised gas a change systems?

A

Their surface area to volume ratio is too great for them to exchange gases with their environment

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9
Q

What are the adaptations of exchange surface?

A
  • Large surface area
  • Large concentration gradient
  • Thin exchange surface
  • Partially permeable
  • Movement of environmental medium e.g air and internal mediums e.g blood
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10
Q

What is the diaphragm?

A

Contracts and flattens to increase lung volume.

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11
Q

What are the alveoli?

A

They are air sacs where gas exchange occurs

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12
Q

What is the trachea?

A

A tube that allows the air to move in and out of the lungs and mouth

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13
Q

What is the role of the rings of cartilage on the bronco and trachea?

A

To prevent them from collapsing

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14
Q

What is the definition of tidal volume?

A

It is the volume of air normally taken in at each breath when the body is at rest

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15
Q

What is the definition of ventilation rate?

A

It is the number of breaths taken in one minute

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16
Q

What is the definition of vital capacity?

A

It is the maximum volume of gas that can be forced out of the lungs at the end of maximum inhalation.

17
Q

What is spirometry?

A

It gives an indication of lung function as it shows he forced vital capacity and forced expiratory volume

18
Q

What are the risks that can cause lung diseases?

A

Smoking, air pollution, genes, infections, occupation

19
Q

What is fibrosis?

A

This is when scar tissue forms in the lungs, which makes the diffusion pathways thicker. Lungs are less elastic so can’t expand to full capacity.
Breathing rate increases to compensate.
It is difficult to force out air.

20
Q

What is asthma?

A

It is when airways become inflamed due to the release of histamines. It causes less air to be able to flow through bronchi and bronchioles, decreasing the rate of diffusion as the concentration gradient is lower. It causes shortness of breath.

21
Q

What is emphysema?

A

It is a disease caused by smoking. It causes the elastins to be broken down making it so they are always stretched, meaning the alveoli cannot recoil to force air out. This lowers the concentration gradient and the surface area of alveoli decreases.

22
Q

What is tuberculosis?

A

A bacterial infection that reduces surface area of the lungs by causing holes and cavities to form in the lung tissue

23
Q

What is the processes of respiration in fish?

A

The fish opens its mouth and the floor lowers, causing the pressure to decrease and the volume of water in the mouth to increase. The water then passes over the gills and oxygen is filtered from the water into the blood, and the water leaves through the opercular opening.

24
Q

What is countercurrent flow and why is it important?

A

It is when water and blood flow in opposite direction. It means that equilibrium isn’t reached and that there is always a concentration gradient maintained across the whole length of the lamellae. Almost all oxygen in the water diffuses into the blood.

25
Q

What are spiracles?

A

They are tiny pores that gas enter which can close to reduce water loss, found in the insect respiratory system

26
Q

What ways do insects prevent water loss?

A
  • Waterproof covering over body (exoskeleton)
  • Small surface area to volume ratio
27
Q

What is the structure of insect gas exchange systems?

A

Spiracles -> trachea -> tracheoles -> cells

28
Q

What is abdominal pumping?

A

To aid in the removal of CO2, insects also pump their abdomen, which raises the pressure in their body. This means that CO2 is forced out the spiracles down the pressure gradient.
Usually only done due to flying or for activities that require fast respiration

29
Q

What are the adaptations of a leaf for gaseous exchange?

A
  1. Flat -> large surface area
  2. Have stomata -> allows air to move in and out leaf
  3. Air spaces in leafs -> short diffusion distance between mesophyll cells & air
30
Q

What are the layers in a leaf?

A
  • Cuticle
  • Upper epidermis cells
  • Palisade mesophyll cells
  • Spongey mesophyll cells
  • Air spaces
  • Lower epidermis cells
  • Stoma & guard cells
31
Q

How does CO2 enter plants?

A

CO2 moves into airspaces via the stomata from high to low concentration
↓
CO2 diffuses from airspaces into cells
↓
Cell CO2 concentration decreases due to photosynthesis
↓
Start again

32
Q

How does O2 leave plants?

A

Cells produce O2 in photosynthesis
↓
O2 diffuses out of cells into air spaces
↓
O2 concentration increases in air spaces
↓
O2 moves out the cell via the stomata

33
Q

How are leafs adapted to reduce water loss?

A
  • Waterproof waxy cuticle -> reduce the rate of water loss from the surface
  • Air spaces -> saturated in water vapour from xylem and water diffuses out of the stomata and evaporates
  • Guard cells -> close at night to prevent water loss
  • Reduced photosynthesis at night -> so stomata can close as less sunlight = less photosynthesis
34
Q

How are xerophytic plants adapted?

A
  • Reduced stomata -> less surface area for water loss
  • Sunken stomata -> reduced conc gradient
  • Hairs trap water vapour -> reduced conc gradient
  • Rolled leaves -> reduced conc gradient
  • Spines -> less surface area for water loss
  • Thick waxy cuticles -> increased diffusion distance
35
Q

Describe and explain the mechanism that causes forced expiration. (4)

A
  1. Contraction of internal intercostal muscles;
  2. Relaxation of diaphragm muscles / of external intercostal muscles;
  3. Causes decrease in volume of chest / thoracic cavity;
  4. Air pushed down pressure gradient;
36
Q

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in alveoli and blood in the capillaries around them (5)

A

1) Many alveoli walls folded to provide large surface area
2) many capillaries provide large SA
3) (so) fast diffusion
4) epithelium wall is then
5) Flattened/ squamous epithelium
6) so short diffusion pathway
7) so faster diffusion
8) Ventilation/ circulation
9) maintains a diffusion/ concentration gradient
10) so fast diffusion

37
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing not required. (4)

A
  1. Trachea and bronchi and bronchioles;
  2. Down pressure gradient;
  3. Down diffusion gradient;
  4. Across alveolar epithelium;
    Capillary wall neutral
  5. Across capillary endothelium / epithelium;
38
Q

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. (6)

A

1 Large surface area provided by lamellae/filaments;
2 Increases diffusion/makes diffusion efficient;
3 Thin epithelium/distance between water and blood;
4 Water and blood flow in opposite directions/countercurrent;
5 (Point 4) maintains concentration gradient (along gill)/equilibrium not reached;
5 Not enough to say gives steep concentration gradient
6 As water always next to blood with lower concentration of oxygen;
7 Circulation replaces blood saturated with oxygen;
8 Ventilation replaces water (as oxygen removed);
6-8 Accept answers relating to carbon dioxide

39
Q

Describe and explain how fish maintain a flow of water over their gills. (4)

A
  1. mouth opens, operculum/opercular valve shuts;
  2. floor of mouth lowered;
  3. water enters due to decreased pressure / increased volume;
  4. mouth closes, operculum/opercular valve opens;
  5. floor raised results in increased pressure / decreased volume;
  6. high/increased pressure forces/pushes water over gills

A-level Biology Year 1 (19 decks)

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