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Biology ALevel AQA PAPER 1 > 💚 3.3 Topic 3 - 3.3.2 Gas exchange > Flashcards

💚 3.3 Topic 3 - 3.3.2 Gas exchange Flashcards

1
Q

What are two things most gas exchange surfaces have in common? + one extra

A

1] A large surface area.
2] Thin [often just one layer of epithelial cells] = short diffusion pathway across gas exchange surface.

3] They also maintain a steep concentration gradient of gases across the exchange surface.

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2
Q

What do single-celled organisms exchange gases across? + how?

A

Their body surface.
They do this by absorbing and releasing gases by diffusion through their outer surface.

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3
Q

Single-celled organisms have a relatively large what? thin what? and short what?

A

Large surface area, thin surface and a short diffusion pathway.

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4
Q

Why is there no need for a gas exchange system in single-celled organisms?

A

As oxygen can take part in biochemical reactions as soon as it diffuses into the cell.

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5
Q

What system do fish use for gas exchange?

A

Counter-current system.

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6
Q

True or false? There is a lower concentration of oxygen in water than in air.

A

True.

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7
Q

How does the counter-current system work for gas exchange in fish?
[5 steps]

A

1] Water enters the fish through its mouth and passes out through the gills.
2] Each gill is made of lots of thin plates called gill filaments [big surface area for exchange of gases].
3] Gill filaments are covered in lots of tiny structures called lamellae [increase the surface area].
4] The lamellae have lots of blood capillaries and a thin surface layer of cells [speed up diffusion].
5] Blood flows through the lamellae in one direction and water flows over in the opposite direction [maintains a large concentration gradient between the water and the blood]. The concentration of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.

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8
Q

Counter-current system simple terms:

A

Blood flows through the lamellae in one direction and water flows over in the opposite direction. It maintains a large concentration gradient between the water and the blood. The concentration of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood.

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9
Q

What would a counter-current system graph look like?

A

y-axis = oxygen concentration
x-axis = distance along gill plate

blood horizontal line up
water horizontal line down

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10
Q

What is each gill made of?

A

Lots of thin plates called gill filaments, which give a big surface area for exchange of gases.

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11
Q

What are the gill filaments covered in?

A

Lots of tiny structures called lamellae, which increase the surface area even more.

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12
Q

The lamellae have lots of ….. ……….. and a …. ……. ….. of cells.

A

Blood capillaries and a thin surface layer of cells.

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13
Q

What do insects use to exchange gases?

A

Tracheae.

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14
Q

What are tracheae?

A

Microscopic air-filled pipes which are used for gas exchange in insects.

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15
Q

How does air move into the tracheae?

A

Through pores on the surface called spiracles.

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16
Q

In the tracheae does oxygen travel up or down the concentration gradient towards the cells?

A

Down towards the cells.

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17
Q

What do the tracheae branch of into?

A

Smaller tracheoles which have thin, permeable walls and go to individual cells = oxygen diffuses directly into the respiring cells - the insects circulatory system does not transport O2.

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18
Q

True or false for gas exchange in insects? CO2 from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere.

A

True.

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19
Q

What movements do insects use to move air in and out of the spiracles?

A

Rhythmic abdominal movements.

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20
Q

Where do dicotyledonous plants exchange gases?

A

At the surface of the mesophyll cells in the leaf.

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21
Q

What do plants need CO2 for? + what gas does this produce as waste?

A

Photosynthesis, which produces O2 as a waste gas.

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22
Q

What do plants need O2 for? + what gas does this produce as waste?

A

Respiration, which produces CO2 as a waste gas.

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23
Q

Where do gases move in and out of in the mesophyll cells?

A

Through special pores in the epidermis called stomata [singular = stoma].

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24
Q

What can the stomata do?

A

The stomata can open to allow exchange of gases, and close if the plant is losing too much water

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25
What cells control the opening and closing of the stomata?
Guard cells.
26
True or false? Insects and plants can control water loss.
True. Exchanging gases tends to make you lose water, plants and insects have evolved adaptations to minimise water loss without reducing gas exchange too much.
27
If insects are losing too much water, what will they close?
Close their spiracles using muscles.
28
What features do insects have to reduce evaporation?
A waterproof, waxy cuticle all over their body and tiny hairs around their spiracles.
29
What happens to the guard cells when water enters?
They go turgid, which opens the stomatal pore.
30
What happens to the guard cells if a plant starts to get dehydrated?
They lose water and become flaccid, which closes the pore.
31
What are the plants called which are adapted for life in warm, dry or windy habitats where water loss is a problem?
Xerophytes.
32
What are the 5 examples of adaptations xerophytes have?
- Stomata sunk in pits. - A layer of hairs on the epidermis. - Curled leaves with the stomata inside. - Reduced number of stomata. - Waxy, waterproof cuticles.
33
How does xerophytes having stomata sunk in pits help reduce water loss?
They trap moist air, reducing the concentration gradient of water between the leaf and the air. This reduces the amount of water diffusing out of the leaf and evaporating away.
34
How does xerophytes having a layer of hairs on the epidermis help reduce water loss?
They trap moist air round the stomata.
35
How does xerophytes having curled leaves with the stomata inside help reduce water loss?
This helps to protect them from wind [windy conditions increase the rate of diffusion and evaporation].
36
How does xerophytes having a reduced number of stomata help reduce water loss?
Fewer places for water to escape.
37
How does xerophytes having waxy, waterproof cuticles help reduce water loss?
This is on the leaves and the stems to reduce evaporation.
38
Why do humans need oxygen in the blood?
For respiration and they need to get rid of carbon dioxide which is made by respiring cells.
39
What happens when you breathe in?
Air enter the trachea [windpipe], trachea splits into two bronchi [one bronchus leading to each lung], each bronchus then branches off into bronchioles, the bronchioles end in small 'air sacs' called alveoli where gases are exchanged.
40
What works together within the body to move air in and out?
The ribcage, intercostal muscles and diaphragm.
41
How many layer of intercostal muscles are there?
3 - need to know about two [internal and external intercostal muscles].
42
What is ventilation in simple terms?
Breathing in [inspiration] and breathing out [expiration].
43
What happens during inspiration?
External intercostal and diaphragm muscles contract = ribcage moves upwards and outwards and the diaphragm flattens. Volume of the thoracic cavity [space where lungs are] increases leading the pressure in the lungs to decrease [below atmospheric pressure]. Air will always flow from an area of high to low pressure [down a pressure gradient], so air flows down the trachea and into the lungs.
44
Is inspiration an active process? + what does this mean?
Yes, meaning it requires energy.
45
What happens during expiration?
External intercostal and diaphragm muscles relax = ribcage moves downwards and inwards and the diaphragm becomes curved again. Volume of the thoracic cavity [space where lungs are] decreases leading the pressure in the lungs to increase [above atmospheric pressure]. Air is forced down a pressure gradient and out of the lungs.
46
Is normal expiration an active process? + what does this mean?
No, meaning it does not require energy.
47
As expirations can be forced, what happens during forced expiration?
The EIM relax and IIM contract, pulling the ribcage further down and in. During this, the movement of the two sets of intercostal muscles is said to be antagonistic [opposing].
48
Alveoli simple definition:
Microscopic air sacs where gas exchange occurs in humans.
49
What is each alveolus made from?
A single layer of thin, flat cells called alveolar epithelium.
50
Why is the huge number of alveoli in the lungs a positive?
It means that there is a large surface area for exchanging oxygen and carbon dioxide.
51
The alveoli are surrounded by a network of ........... .
Capillaries.
52
How does oxygen get from the alveoli into the blood? + carbon dioxide?
O2 diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium [a type of epithelium that forms the capillary wall], and into haemoglobin in the blood. CO2 diffuses into the alveoli from the blood, and is breathed out.
53
What is a summary of the human gaseous exchange, including in the alveoli?
O2 moves down the trachea, bronchi and bronchioles into the alveoli [down a pressure gradient]. Once in the alveoli, the O2 diffuses across the alveolar epithelium, then the capillary endothelium, ending up in the capillary itself [down a diffusion gradient].
54
What are the features alveoli have to speed up the rate of diffusion so gasses can be exchanged quickly?
1] A thin exchange surface - the alveolar epithelium is only one cell thick = short diffusion pathway (which speeds up diffusion). 2] A large surface area - the large number of alveoli = a large surface area for gas exchange.
55
Is there a steep concentration gradient of oxygen and carbon dioxide between the alveoli and the capillaries?
A steep one, which increases the rate of diffusion.
56
How is the steep concentration gradient of oxygen and carbon dioxide between the alveoli and the capillaries maintained constantly?
By the flow of blood and ventilation.
57
What can measures of lung function help to diagnose?
Lung disease.
58
What does lung disease affect?
Both ventilation [breathing] and gas exchange in the lungs [how well the lungs function].
59
Tidal volume defintion:
Volume of air in each breath. [Usually between 0.4dm3 and 0.5dm3 for adults]
60
Ventilation rate defintion:
The number of breaths per minute. [For a healthy person at rest it's about 15 seconds]
61
Forced expiratory volume [FEV1] definition:
It is the maximum volume of air that can be breathed out in 1 second.
62
Forced vital capacity [FVC] definition:
It is the maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in.
63
You figure out tidal volume, ventilation rate and other measures of breathing from a graph produced by a what?
Spirometer [a fancy machine that scientists and doctors use to measure the volume of air breathed in and out].
64
What are 4 different lung diseases?
Pulmonary Tuberculosis [TB], Fibrosis, Asthma and Emphysema.
65
What happens when someone becomes infected with TB?
Immune system cells build a wall around the bacteria in the lungs. This forms small hard lumps called tubercles. Infected tissue within the tubercles dies and the gaseous exchange surface is damaged, so the TV is decrease. Tuberculosis also causes fibrosis, which further reduces the TV.
66
What does other lung disease does tuberculosis also cause?
Fibrosis.
67
What happens when the tidal volume [TV] is reduced?
Less air can be inhaled with each breath. In order to take in enough oxygen, patients have to breathe faster, i.e. ventilation rate is increase.
68
What are common symptoms of pulmonary tuberculosis [TB]?
A persistent cough, coughing up blood and mucus, chest pains, shortness of breath and fatigue.
69
What can fibrosis be a result of?
An infection or exposure to substances like asbestos or dust.
70
Fibrosis is the formation of what?
Scar tissue in the lungs.
71
How is scar tissue formed from fibrosis, different from normal lung tissue?
It is thicker and less elastic.
72
How does fibrosis affect someones lungs?
It leads to the lungs being less able to expand and so can't hold in as much air as normal. This leads to the TV being reduced [leads to a faster ventilation rate than normal to get enough air into their lungs to oxygenate their blood] as well as the FVC [a smaller volume of air can be forcefully breathed out].
73
What does fibrosis do to the rate of gaseous exchange? Why?
Diffusion is slower across a thicker scarred membrane.
74
What are common symptoms of Fibrosis?
Shortness of breath, a dry cough, chest pain, fatigue and weakness.
75
What type of condition is asthma? + what is it usually caused by?
A respiratory condition where the airways become inflamed and irritated. It is usually caused by an allergic reaction to substances such as pollen and dust.
76
What happens during an asthma attack? + what does it cause?
The smooth muscle lining the bronchioles contracts and a large amount of mucus is produced. It causes constriction of the airways making it difficult to breathe properly. Air flow in and out of the lungs is severely reduced. Reduced air flow = FEV1 is reduced.
77
What are common symptoms of asthma?
Wheezing, a tight chest and shortness of breath.
78
What do inhalers used to relieve asthma include?
Drugs which cause the muscle in the bronchioles to relax opening up the airways.
79
What is emphysema? + what is it caused by?
It is a lung disease caused by smoking or long-term exposure to air pollution. Foreign particles in the smoke/air become trapped in the alveoli.
80
What does emphysema cause in the alveoli? and what does it attract?
It causes inflammation in the alveoli which attracts phagocytes to the area. The phagocytes produce an enzyme that breaks down elastin which is a protein found in the walls of the alveoli.
81
What is elastin? + what does it mean if this is reduced by emphysema?
Elastin is elastic which helps the alveoli to return to their normal shape after inhaling and exhaling air. If this is reduced, the alveoli cannot recoil to expel air [it remains trapped in the alveoli].
82
What can emphysema also lead to beside from a reduction is elastin?
It also leads to destruction of the alveoli walls = reduces the surface area of the alveoli & rate of gaseous exchange decreases.
83
What are common symptoms of emphysema?
Shortness of breath and wheezing.
84
Do people with emphysema have an increased ventilation rate?
Yes as they are trying to increase the amount of air reaching their lungs.
85
What do lung diseases all lead to in simple terms?
Reduce rate of gaseous exchange in the alveoli, less oxygen diffuses into the bloodstream, body cells receive less oxygen, rate of aerobic respiration is reduced, less energy is released, feel tired and weak.
86
What are risk factors?
Factors which increase a persons chance of getting that disease.
87
What is a key phrase which thinks correlation and causation?
Correlation does not always mean causation. [Correlation does not always mean that one thing causes the other].
88
What is the equation linking pulmonary ventilation rate [PVR], tidal volume and breathing rate?
Pulmonary ventilation rate [PVR] = tidal volume x breathing rate.

Biology ALevel AQA PAPER 1 (16 decks)

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