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AQA A-Level Biology 1-4 > 3.1-2 Gas Exchange in Organisms > Flashcards

3.1-2 Gas Exchange in Organisms Flashcards

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1
Q

What needs to be exchanged between an organism and its environment?

A

Respiratory gases - oxygen, carbon dioxide, water
Nutrients- vitamins, minerals, glucose
Excretory products - urea, faeces, fibre
Heat

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2
Q

What kind of exchanges can take place?

A

Passive - simple diffusion and osmosis

Active - facilitated diffusion and active transport

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3
Q

What happens to SA:V ratio when you increase the surface area?

A

As surface area increases
Volume will eventually become bigger than the surface area

Therefore SA:V ratio decreases

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4
Q

What is fick’s law?

A

Large SA x steep concentration gradient

Divided by

Short diffusion distance

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5
Q

What are some single cell organisms?

A

Bacteria
Fungi
Yeast
Algae

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6
Q

How does gas exchange take place in single celled organisms?

A

High SA:V ratio
1 cell thick therefore short diffusion distance
They use O2 for respiration constantly and water for chemical reactions (like protein synthesis) therefore steep concentration gradient as more O2 and water outside the cell

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7
Q

Describe the pathway of oxygen into insects?

A 
Spiracle
Trachea
Tracheoles
Capillaries 
Cells
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8
Q

How is steep concentration gradient achieved in gas exchange of insects?

A

Oxygen is constantly used by the cells for aerobic respiration therefore there is always more oxygen outside the cells

Abdominal pumping (rhythmic contractions) moves the gas in and out

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9
Q

How is large surface area achieved in gas exchange of insects?

A

Thin flat body surface

Leads to many spiracles available for oxygen to move in

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10
Q

How is short diffusion distance achieved in gas exchange of insects?

A

The tubes have a thin permeable membrane adjacent to individual cells for aerobic respiration

Mitochondria are rarely more than a few micrometers away from an air capillary

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11
Q

How does the trachea in insects being filled with water at the end help gas exchange?

A

In major activity anaerobic respiration takes place producing lactate = lower water potential
Therefore water moves into the cells and the volume of water in the trachioles decreases drawing air further in
This means the final stage of diffusion takes place as a gas and not a liquid making diffusion happen quicker

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12
Q

What is important about the trachea in insects?

A

They are supported by strengthened rings to prevent them form collapsing

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13
Q

How do insects limit water loss?

A

Small SA:V ratio - minimising area for water to be lost
Water proof covering on their whole body
Spiracles can be closed

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14
Q

How does water move into a fish?

A

Open mouth
= volume increases
∴ pressure decreases
Drawing water in because of the pressure concentration gradient

Water is forced over the gills for gas exchange

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15
Q

How does water move out of a fish?

A

Close mouth
= volume decreases
∴ pressure increases
Forcing water out because of the pressure concentration gradient

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15
Q

How is steep concentration gradient achieved in gas exchange of fish?

A

The blood in the gills acquiring oxygen moves around the body
∴ maintaining a steep concentration gradient
As always more oxygen in the water

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16
Q

How is large surface area achieved in gas exchange of fish?

A

The gill filaments and lamella

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17
Q

How is short diffusion distance achieved in gas exchange of fish?

A

1 cell thick to move through

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19
Q

What property do fish have?

A

A waterproof coating and therefore it is gas tight

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20
Q

What is the gill lamella?

A

Where the actual exchange takes place

A little disk perpendicularly placed at the end of the gill filaments that make up the gill rakers

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21
Q

How does the water move within the gills of a fish?

A

Countercurrent flow

The water moves in the opposite direction to the blood flow
A constant concentration gradient is maintained across the whole lamella

This allows for 80% of oxygen available to be absorbed into the blood

22
Q

What would happen if the fish gills used a parallel flow?

A

You reach an equilibrium where no diffusion can take place as the concentration gradient becomes isotonic

Only 50% of oxygen available can be absorbed into the blood

23
Q

What are the features of the cross section of a leaf? Top to bottom

A

Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongey mesophyll (containing air spaces)
Lower epidermis- containing guard cells and stomata

24
Q

What is the equation for photosynthesis?

A

6H20 + 6CO2 -> C6H12O6 + 6O2

25
Q

What is different about gas exchange in plants?

A

They respire and photosynthesise therefore the products produced can be used as the reactants in the other
This can reduce gas exchange with the external medium (air)
However depends on the balance of the rates as most of the reactants are acquired from the external medium

26
Q

How do stomata work in gas exchange?

A

They are surrounded by guard cells which can open and close the stomatal pore to control gas exchange

27
Q

How is large surface area achieved in gas exchange of plants?

A

They are flat and thin due to air spaces in the spongey mesophyll

28
Q

How is steep concentration gradient achieved in gas exchange of plants?

A

O2, water and CO2 are constantly being used up in respiration and photosynthesis

Through transpiration a constant flow of water is achieved through the plant with the stomata helping

29
Q

How is short diffusion distance achieved in gas exchange of plants?

A

Between the stomata the gas travels through the numerous interconnecting air spaces and only has to go through 1 cell

Diffusion takes place in the gas phase which makes it faster than if it was in water

30
Q

What is a xerophyte?

A

A plant that is adapted to live in areas where water is in short supply

31
Q

What are the adaptations of xerophytic plants to limit water loss?

A 
Thick waxy cuticle
Hairs on its lower surface 
Leaf rolled up
Stomata in pits
Shallow roots close to the surface 
Reduced SA:V ratio of leaves
32
Q

How does the thick waxy cuticle in xerophytes help reduce water loss?

A

Reduces water evaporation from its surface

33
Q

How does hairs on the lower surface, leaf rolled up and stomata in pits help reduce water loss in xerophytes?

A

Traps the still moist air inside/next to the stomata

Which reduces the water potential gradient

34
Q

How do the shallow roots in xerophytes help reduce water loss?

A

Allows more water to be absorbed

35
Q

How does the reduced SA:V ratio of leaves in xerophytes help reduce water loss?

A

They are small and circular in cross as so not to compromise large SA for photosynthesis

36
Q

Describe inspiration in mammals?

A

The external intercostal muscles and the diaphragm contract whilst the internal intercostal muscles relax
The ribcage moves up and out which increases the volume of the thorax and decreases the pressure inside the lungs

Because of the concentration gradient of pressure air is forced in

37
Q

Describe expiration in mammals?

A

The external intercostal muscles and the diaphragm relax whilst the internal intercostal muscles contract (if expiration is forced)
The ribcage moves down and in which decreases the volume of the thorax and increases the pressure inside the lungs

Because of the concentration gradient of pressure air is forced out

38
Q

What is the equation for pulmonary ventilation?

A

Pulmonary ventilation = tidal volume (dm3) X ventilation rate (min-1)

39
Q

What is pulmonary ventilation?

A

Total volume of air moved into the lungs per minute

40
Q

What is tidal volume?

A

Total volume of air taken in each breath

41
Q

What is ventilation rate?

A

Number of breaths per min

42
Q

How is short diffusion distance achieved in gas exchange of mammals?

A

Thin cell surface membrane
The capillaries are immediately next to the alveoli
The cell wall of the alveolus is 1 cell thick

43
Q

How is large surface area achieved in gas exchange of mammals?

A

Lots of alveoli create a large SA in a small space

44
Q

How is steep concentration gradient achieved in gas exchange of mammals?

A

The movement of the internal medium of blood is constant - O2 is moved away around the body

The movement of external medium of air is constant - due to changes in volume and pressure (always more oxygen in alveoli)

This keeps oxygen and carbon dioxide levels at a constant concentration gradient

45
Q

What does the alveolus and capillary include?

A

Cell wall
Thin layer of moisture

Plasma
Red blood cells
Cell wall

O2 and CO2 diffusing between the two

46
Q

What is the cause, symptoms and treatment of pulmonary tuberculosis? Risk factors?

A

Caused by a bacterium

Difficulty breathing
Chest pain
Coughing

Antibiotics

Smoker, HIV, Age

47
Q

What is the effect on gas exchange in the lungs of pulmonary tuberculosis?

A

The white blood cells surrounding the bacteria prevent a path to the cell membrane of the alveoli so oxygen struggles to diffuse in

48
Q

What is the cause, symptoms and treatment of pulmonary fibrosis? Risk factors?

A

Dust, mould - viral infection

Short of breath
Cough

Nutritional advice, oxygen therapy, lung transplant

Age, gender(men)

49
Q

What is the effect on gas exchange in the lungs of pulmonary fibrosis?

A

A lot of scaring on the alveoli creating irregular/abnormal air spaces
Leading to less surface area for exchange

Fibrous connective tissue also builds up in the lungs reducing elasticity

50
Q

What is the cause, symptoms and treatment of asthma? Risk factors?

A

Unknown

Breathlessness
Tight chest

Inhalers

Genetic, smoking

51
Q

What is the effect on gas exchange in the lungs of asthma?

A

Bronchiole tubes become constricted due to muscle spasms therefore a lack of oxygen reaches the alveoli

52
Q

What is the cause, symptoms and treatment of emphysema? Risk factors?

A

Smoking
Air-pollution

Coughing
Exhaustion

Bronchodilators
Inhaled steroids

SMOKING!
Air pollution, genetics, age

AQA A-Level Biology 1-4 (20 decks)

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