Exchanges of substances Flashcards
1
Q
What is surface area to volume ratio?
A
- The ratio of an organisms surface area compared to its volume
- influences the efficiency of substance exchange
2
Q
How does size affect surface area to volume ratio?
A
as organism increases in size, its surface area to volume ratio decreases
3
Q
Why do small organisms rely on diffusion for exchange?
A
- They have a large surface area to volume ratio and short diffusion distances
- allowing efficient diffusion of substances
4
Q
Why do large organisms need specialized exchange surface?
A
- They have a small surface area to volume ratio
- This increases diffusion distances
- So requires adaptations for efficient exchange
5
Q
Calculation for surface area of a cube
A
area of one face x 6
6
Q
Calculation for volume of a cube
A
length x width x height
7
Q
What happens to the surface area to volume ratio when the size of a cube doubles?
A
decreases
because surface area increases at a slower rate than volume
8
Q
What are the adaptations for exchange surface
A
- Large surface area - more space for diffusion (villi, alveoli)
- Thin barriers - short diffusion distance
- Good blood supply or ventilation - maintains concentration gradients (capillaries, gills)
9
Q
How do villi and microvilli improve exchange?
A
increase surface area in the small intestine for efficient absorption of nutrients
10
Q
What features make alveoli efficient for gas exchange?
A
- Large surface area
- Thin walls
- Rich blood supply
- Moist surface
11
Q
Why do large organisms need efficient exchange surfaces?
A
Their surface area to volume ratio is too small for diffusion alone to meet metabolic demands
12
Q
Why cant large organisms rely on diffusion alone for exchange?
A
Diffusion becomes too slow due to increased diffusion distance
13
Q
How do organisms overcome diffusion limitations without specialized exchange systems?
A
By having a flattened shape (e.g flatworms) - reduces diffusion distances and increases surface area
14
Q
How do desert animals adapt their surface area to volume ratio?
A
Many have large ears to increase surface area for heat loss
15
Q
Why do fish need a specialized gas system?
A
fish have scales, which make them waterproof and a small surface rea to volume ratio, so they cannot rely on diffusion alone
16
Q
What is the gas exchange surface in fish
A
gills - allowing oxygen uptake from water
17
Q
Why is extracting oxygen from water more difficult than from air?
A
water contains 30 times less oxygen than air
18
Q
How are fish gills adapted for a large surface area?
A
- fish have four sets of gill filaments on each side of the head
- each filament has many thin gill lamellae at right angles to increase surface area
19
Q
How do fish gills provide a short diffusion distance?
A
- gill lamellae are very thin
- dense capillary network in each lamellae brings blood close to the surface for gas exchange
20
Q
What adaptation in fish gills maintains a high oxygen concentration gradient?
A
The countercurrent exchange principle ensures continuous diffusion
21
Q
What happens in countercurrent flow?
A
- water flows over the gills in the opposite direction to blood in the capillaries
- ensuring blood always meets water in a high oxygen concentration, maintaining diffusion gradient along the entire lamellae
22
Q
Why is countercurrent flow more efficient than concurrent flow?
A
- in countercurrent flow, equilibrium is never reached so oxygen diffuses along the entire length of the lamellae
- in concurrent flow, equilibrium will be reached at 50% oxygen saturation, stopping further diffusion
23
Q
What must you mention in an exam question about countercurrent flow?
A
- water and blood flow in opposite directions
- equilibrium is never reached, so diffusion continues
- a diffusion gradient is maintained across the entire lamellae
24
Q
Why can single celled organisms rely on diffusion only?
A
They have a large surface area to volume ratio, allowing oxygen and carbon dioxide to diffuse directly across the cell membrane
25
What are the main gases exchanged in single celled organisms?
- oxygen diffuses in for respiration
- carbon dioxide diffuses out
26
Why do multicellular organisms need a transport system?
- small surface area to volume ratio
- need specialized circulatory system
27
What is the main challenge insects face for gas exchange?
They must balance gas exchange with the need to conserve water in dry environments
28
What is the specialized gas exchange system in insects called?
The tracheal system - a network of internal air-filled tubes
29
what are the key components of the tracheal system?
- Trachea - large air tubes supported by rings
- Tracheoles - smaller tubes that extend into body tissues, delivering oxygen directly
- Spiracles - pores that control gas entry and water loss
30
What are the three ways gases move in and out of the tracheal system?
1. Diffusion gradient - oxygen moves in and it is used up and co2 moves out
2. Ventilation (mass transport) - muscle contractions speed up airflow
3. Water movement in tracheoles - lactate lowers water potential, drawing water into muscle cells, reducing diffusion distance in liquid phase
31
How does an insect reduce water loss through spiracles?
Spiracles can open and close using valves to minimize water loss when gas exchange isn't needed
32
What is the main limitation of the insect tracheal system?
Insects must be small as diffusion must cover short distances for efficient exchange
33
How do multicellular animals overcome diffusion limitations?
They use a specialized circulatory system to transport substances efficiently
34
What are the three main components of a circulatory system?
- A heart - to pump the transport fluid
- Vessels - to direct fluid flow
- A transport fluid - to carry substances (eg blood, haemolymph)
35
What is an open circulatory system?
- found in insects
- haemolymph is pumped into a body cavity where it bathes organs directly
- ostia (pores) allows haemolymph to be sucked back into the heart
36
What is a closed circulatory system?
- found in vertebrates and some invertebrates
- blood remains enclosed in vessels at all times
- blood is pumped through a series of vessels, allowing efficient transport
37
What needs to be exchanged between an organism and its environment?
- Respiratory gases
- Nutrients
- Excretory products
- Heat
38
What is the function of selectively permeable plasma membranes surrounding specialised exchange surfaces?
They control what substances are exchanged, allowing only specific materials to pass through.
39
How does an extensive blood supply or ventilation contribute to the efficiency of specialised exchange surfaces?
It maintains steep concentration gradients, which enhances the rate of diffusion across the exchange surface.
40
What is the purpose of thin walls in specialised exchange surfaces?
minimise the diffusion distance, allowing - faster exchange of substances.
41
What substances do plants exchange, absorb, or lose?
- Water
- minerals
- sunlight
- oxygen
- carbon dioxide.
42
How are roots adapted for absorbing water and minerals?
- Spread out for a large surface area.
- Covered in millions of root hair cells for maximum absorption.
43
What is the main function of leaves?
Photosynthesis – converting light energy into food
44
How are leaves adapted for photosynthesis?
- Broad & flat → Large surface area for light absorption
- Thin → Short diffusion path for gases
- Chloroplasts in palisade cells → Maximizes light capture
- Air spaces in spongy mesophyll → Allows efficient gas exchange
- Veins → Transport water (xylem) and food (phloem)
45
What are stomata?
Small holes on the underside of leaves that allow gas exchange and water loss
46
How do guard cells control stomata?
- Turgid (full of water) → Stomata open.
- Flaccid (low water) → Stomata close to prevent water loss.
47
What happens if stomata stay open permanently?
The plant loses too much water and may dehydrate
48
What does the waxy cuticle do?
Limits water loss and acts as a protective barrier
48
What do palisade cells do?
Contain chloroplasts for photosynthesis
49
How is the spongy mesophyll adapted for gas exchange?
Contains air spaces for easy diffusion of CO₂ and O₂
50
How is a dicotyledon leaf adapted for photosynthesis?
- Thin → Short diffusion path.
- Palisade layer → Packed with chloroplasts.
- Veins → Transport water & sugars.
51
How does Fick’s Law explain efficient gas exchange in leaves?
- Large surface area → Faster diffusion.
- Thin leaves → Short diffusion path.
- High concentration difference → CO₂ moves in, O₂ moves out.
52
How does gas exchange change between day and night?
Day: CO₂ in for photosynthesis, O₂ out.
Night: O₂ in for respiration, CO₂ out.
53
Why Are Stomata on the Underside?
Reduces water loss by keeping them in shade
54
When and why do stomata close?
When the plant lacks water to prevent dehydration.
55
Why do chloroplasts move inside cells?
To maximize light absorption or avoid damage in high light intensity.
56
Where does most gas diffusion occur in plants?
In the leaves, due to their thin & flat shape and many stomata
57
How do CO₂ levels affect stomata opening?
- Low CO₂ → Guard cells absorb water → Stomata open.
- High CO₂ → Guard cells lose water → Stomata close.
58
Why do plants need oxygen?
For respiration, which releases energy from food
59
How do insects reduce water loss?
- Waterproof cuticle on exoskeleton.
- Small surface area to volume ratio to minimize evaporation.
- Spiracles (openings) can close to prevent water loss.
61
How do insects exchange gases?
Through the Tracheal system
62
How do gases move in and out of an insect’s body?
- Diffusion gradient: O₂ moves in where needed; CO₂ moves out.
- Ventilation: Muscle movements create airflow in tracheae
63
Why must insects be small?
The tracheal system relies on diffusion, which is only effective over short distances
64
Why do plants need a transport system?
- Larger plants have a low surface area to volume ratio.
- They need specialized vascular tissues to transport water & nutrients
65
What are vascular plants?
Plants that have specialized transport systems, like xylem and phloem
66
How do plants absorb water?
- Root hairs absorb water and minerals from the soil.
- Water lost via transpiration must be replaced.
67
How is Marram Grass adapted to dry environments?
- Rolled leaves → Reduce water loss.
- Traps humid air → Reduces evaporation.
- Hairs on leaves → Slow air movement & decrease water loss.
68
How do plants obtain the oxygen required for aerobic respiration?
The majority of the oxygen required diffuses from the atmosphere through stomata and into leaves
69
How do plants obtain the carbon dioxide required for photosynthesis?
carbon dioxide diffuses from the atmosphere through stomata and into leaves
70
What gases do plants exchange with the atmosphere in the absence of light, and why?
In the dark, plants use diffusion to take in oxygen and release carbon dioxide
- because photosynthesis cannot occur without light, but aerobic respiration still takes place, requiring oxygen and producing carbon dioxide.
71
What adaptations do plant leaves have to reduce water loss?
- Waxy cuticle forms a waterproof barrier
- Guard cells close stomata when needed
72
What is meant by the term xerophyte?
Xerophytes are plants adapted to survive in dry conditions with limited water supply
73
What structural and physiological adaptations do xerophytes have to reduce water loss?
- Thick waxy cuticle - reduces water loss by evaporation
- Small, needle-like leaves - reduce the surface area across which water can be lost
- Hairs on leaves or rolled-up leaves - trap moist air next to leaf surface reducing the water potential gradient
- Water storage organs - conserve water
- Sunken stomata - trap moist air next to leaf surface reducing the water potential gradient
74
What are the different tissues in a typical plant leaf and their functions?
- Upper epidermis with waxy cuticle - reduces water loss
- Mesophyll - performs photosynthesis
- Lower epidermis - has stomata surrounded by guard cells for gas exchange
- Vascular tissue (xylem and phloem) - transports water and nutrients
75
What is the difference between breathing and respiration?
- Breathing: Movement of air into and out of the lungs.
- Respiration: Chemical reaction in cells that releases energy (ATP).
76
What is the difference between ventilation and gas exchange?
- Ventilation: The scientific term for breathing (air moving in & out).
- Gas Exchange: Diffusion of O₂ into blood and CO₂ out at the alveoli.
77
What are the main structures in the gas exchange system?
- Lungs
- Trachea
- Bronchi
- Bronchioles
- Alveoli
78
What is the function of cartilage rings in the trachea?
To keep the airway open and prevent collapse
79
What are the two key processes in ventilation?
1. Inhalation (Inspiration): Air is drawn into the lungs.
2. Exhalation (Expiration): Air is forced out of the lungs.
80
What muscles are involved in breathing?
- Diaphragm (muscle under lungs).
- External & internal intercostal muscles (between ribs).
81
What does "antagonistic" mean in breathing?
One muscle contracts while the other relaxes
82
What happens during inhalation?
1. Diaphragm contracts & flattens.
2. External intercostal muscles contract (ribcage moves up & out).
3. Volume in thorax increases.
4. Pressure in lungs decreases.
5. Air moves in (high pressure outside → low pressure inside).
83
What happens during exhalation?
1. Diaphragm relaxes & domes up.
2. Internal intercostal muscles contract
3. Volume in thorax decreases.
4. Pressure in lungs increases.
5. Air moves out (high pressure inside → low pressure outside).
84
What is the function of the alveoli?
To provide a large surface area for efficient gas exchange.
85
How are alveoli adapted for gas exchange?
- Millions of alveoli → Large surface area.
- One-cell thick walls → Short diffusion distance.
- Surrounded by capillaries → Maintains concentration gradient.
86
How does gas exchange occur in the alveoli?
- O₂ diffuses into blood from alveoli.
- CO₂ diffuses out from blood into alveoli.
87
Why are capillaries important in gas exchange?
They maintain a constant concentration gradient by:
- Bringing in low oxygen blood.
- Carrying away oxygenated blood.
88
How does air move in and out of the lungs?
Air moves from high pressure to low pressure.
89
What factors affect how fast we breathe?
- Exercise → Muscles need more O₂, so breathing rate increases.
- High CO₂ levels → Detected by brain, increases breathing rate.
90
Describe the basic structure of an alveolus.
small air sac with a thin wall comprising one layer of squamous epithelial cells, elastic fibres, and collagen fibres
91
What is the function of collagen fibres in alveoli?
They contain strong collagen that prevents alveoli from bursting and limits overstretching
92
Which blood vessels are involved in human gas exchange in the lungs?
- Pulmonary Artery
- Capillaries
- Pulmonary vein
93
What is the function of the pulmonary artery?
delivers deoxygenated blood (rich in carbon dioxide) from the heart to the pulmonary capillaries
94
What is the function of capillaries?
carbon dioxide diffuses from the capillary blood into the alveoli, and oxygen diffuses from the alveoli into the capillary blood
95
What is the function of the Pulmonary vein?
delivers oxygenated blood (rich in oxygen) from the pulmonary capillaries to the heart
96
What is the role of the human gas exchange system?
to exchange oxygen and carbon dioxide between the body and the environment
97
Why are the lungs located inside the body in mammals?
- Air is not dense enough to support the delicate lung tissues
- To reduce water loss
98
Where in the lungs does gas exchange occur?
across the alveolar membrane of alveoli
99
Describe the pathway air takes after it enters the body via the mouth and/or nose.
1. Air enters the trachea
2. Air moves into the two bronchi
3. Air moves into the bronchioles
4. Air moves into the alveoli
100
Which structures line the trachea and bronchi
- Cartilage
- Smooth muscle
- Goblet cells
- Ciliates epithelial cells
101
Where are the lungs located in mammals, and how are they protected?
The lungs are located inside the chest in the thoracic cavity, protected by the ribcage
102
How do elastic fibres in the alveoli contribute to exhalation?
They shrink and recoil back to their original shape when the thoracic cavity volume decreases
103
Why is oxygen uptake a measure of metabolic rate in organisms?
Oxygen is used in respiration which provides energy
104
Describe the pathway taken by an oxygen molecules from an alveolus to the blood
- Across alveolar epithelium
- Endothelium of capillary arteries
105
Ways an insects tracheal system is adapted for efficient gas exchange
- Tracheoles have thin walls so short diffusion distance
- large number of tracheoles so large surface area
- tracheoles provide tubes full of air so fast diffusion
