Topic 3A - Exchange and transport systems Flashcards
Give 3 examples that show that organisms need to exchange substance
- Cells need to take in oxygen (for aerobic respiration) and nutrients
- They also need to excrete waste products like CO2 anr urea
- Most organisms need to stay at same temp, so heat needs to be exchanged too
The ease of exchanging substances depends on the organisms…
Surface area to volume ratio
Do smaller animals have higher or lower surface area: volume ratios?
They have higher surface area: volume ratios
In single-celled organisms, how are substances exchanged in/out of the cell?
Substances can diffuse directly into/out of the cell across the cell surface-membrane
In single-celled organism, why is diffusion rate quick?
Diffusion rate is quick because of the large SF and the small distances the substances have to travel
In multicellular organisms, why is diffusion across the outer membrane (into the environment) slow?
- Some cells are deep within the body - big distance between them and environment
- Large animals have low SF:V ratio - difficult to exchange enough to supply large volume of animal through relatively small outer surface
How are multicellular organisms specialised to exchange substances?
They use exchange organs e.g. lungs and a mass transport system
How is mass transport different in mammals and plants?
Mammals - refers to circulatory system, which uses blood to carry glucose and 02 around body. Also carries hormones , antibodies and waste like CO2
Plants - refers to transport of water and solutes in the xylem and phloem
How does the size of an animal affect heat exchange?
If animal too big - Hard to lose heat from body and SF: is small compared to volume
If animal too small - Heat is lost more easily as SA is large.
How does the shape of an animal affect heat exchange?
- Animals with compact shape have a smaller SA to volume ratio to minimise heat lose
- Animals with a less compact shape (sticky out bits) have a higher SA to volume ratio, increasing heat loss from their surface
Describe some behavioural and physiological adaptions, that SMALL animals use, to aid exchange
1) High SA:V ratio means they tend to lose more water as it evaporates from their surface. So some desert animals have kidney structure adaptations to produce less urine
2) Small animals in cold areas need to eat high energy foods like nuts, to support metabolic rates
3) Small animals may have thick layers of fur or hibernate when its cold
Describe some behavioural and physiological adaptions, that LARGER animals use, to aid exchange
- elephants have large flat ears to increase their SA, allowing them to lose heat
- hippos spend much of the day in water, to help them lose heat
What factors increase the rate of diffusion across exchange surfaces?
- Large surface area
- Thickness (exchange surfaces are only 1 layer of epithelial)
- Steep concentration gradient of particles
Why do fish need a counter current system for gas exchange?
Because there’s a lower conc of 02 in water than air, so they need special adaptations to get enough O2
Describe the counter-current system that fish use for gas exchange (diagram)
- H2O enters fish through mouth and out through gills
- Gills made of thin plates, gill filaments (for large SA)
- Filaments covered in lamellae, to increase SA more
- Lamellae have blood capillaries and thin surface layer of cells to speed up diffusion
- Blood and water flow in lamellae along opposite directions, maintaining large conc gradient between 2. Conc of O2 in water is always higher than in blood,so as much 02 as possible diffuses into blood
What do insects use to exchange gases?
Tracheae - microscopic air-filled pipes
Describe how insects use tracheae to exchange gases
- Air enters tracheae through surface pores; spiracles
- Oxygen travels down conc gradients towards cells
- Tracheae branch off to smaller, thinner, permeable walls (tracheoles) and go to cells. O2 is diffused to cells
- CO2 moves down conc gradient to spiracles, to be released
- RAM to move air in and out spiracles
What gases do plants need for photosynthesis and respiration?
Photosynthesis - C02
Respiration - O2
What is the main gas exchange surface for dicotyledonous plants? (DIAGRAM)
The surface of mesophyll cells in the leaves
How are mesophyll cells adapted to their function?
They have a large surface area so faster diffusion rate
What are stomata and what do they do?
They are pores in the epidermis that allow gases to move in and out of leaf
- They open to allow exchange of gases and close to prevent water loss
What do guard cells do?
They control the opening and closing of stomata
What adaptations do insects have to reduce water loss?
- They close their spiracles using muscles
- Waterproof, waxy cuticle around body & tiny hairs around spiracles to reduce water loss by evaporation
How are guard cells adapted to control water loss?
- Water enters guard cells, making them turgid, and opening stomatal pore as usual
- when plant is dehydrated, guard cells lose water and become flaccid, closing the pore
Give 5 examples of xerophytic adaptations (DIAGRAM)
- Stomata sunken in pits that trap most air, reducing conc gradient of water between leaf & air and reducing water loss by evaporation
- Layer of ‘hairs’ on epidermis - to trap moist air
- Curled leaves with stomata in, to protect from wind
- Reduce number of stomata
- Waxy waterproof cuticles on leafs and stems
Lungs are specialised organs for…
Gas exchange
Describe the structure of the lungs
- When you breathe in, air enters the trachea
- Trachea splits into 2 bronchi (one goes to each lung)
- Bronchus branches into smaller tubes - bronchioles
- Bronchioles end in small ‘air sacs’ called alveoli
- Ribcage, intercostal muscles, diaphragm all work together to move air in and out
How many layers of intercostal muscles are there?
3
Define the terms ventilation, inspiration and expiration
Ventilation - breathing in and out
Inspiration - breathing in
expiration - breathing out
Describe the process of inspiration
- External intercostal and diaphragm muscles contract
- So ribcage moves upwards & outwards and diaphragm flattens, increasing vol of thoracic cavity
- As volume of TC increases, lung pressure decreases (to below atmospheric pressure)
- Air moves from area of high pressure to area of low pressure so air flows down trachea and into lungs
Is inspiration an active or passive process?
It’s an active process
Describe the process of expiration?
- External intercostal and diaphragm muscles relax
- So ribcage moves downwards & inwards and diaphragm is curved, decreasing vol of thoracic cavity
- As vol of TC decreases, lung pressure increases (above atmospheric temp)
- Because of conc gradient, area moves out of lungs
Can expiration be forced?
Yes
What happens during forced expiration?
- During forced expiration, the external intercostal muscles relax whilst internal intercostal muscles contract
- This moves ribcage further down and in
- Movement of external & internal intercostal muscles are antagonising (opposing)
Where does gaseous exchange take place in humans? (the specific part)
In the alveoli
What are alveoli surrounded by?
They are surrounded by a network of capillaries
Describe the diffusion of O2 and CO2 in the alveoli (DIAGRAM)
- O2 diffuses (down conc gradient) out of alveoli, across alveolar epithelium and capillary endothelium (type of epithelium that forms capillary wall), and into haemoglobin in the blood
- CO2 diffuses (down conc gradient) into the alveoli from the blood, and is breathed out
What factors speed up the rate of diffusion in the alveoli?
- Thin exchange surface
- Large number of alveoli in lung (to give large SF)
- Steep conc gradient of O2 and CO2 between alveoli and capillaries (constantly maintained by flow of blood and ventilation
Is expiration an active or passive process?
A passive process
What do lung diseases affect?
They affect ventilation and gas exchange in lungs
Define tidal volume (and what is the normal TD for adults?)
the volume of air in each breath - usually between 0.4 dm^3 and 0.5 dm^3 for adults
Define ventilation rate (and what is the normal VR for a healthy person?)
The number of breaths per min. For a healthy person at rest, it’s about 15 breaths
Define Forced expiratory volume (FEV1)?
The max vol of air that can be breathed out in 1 sec
Define forced vital capacity (FVC)?
Max vol of air that is possible to breathe forcefully out of lungs after a really deep breath in
1dm^3 is equal to…
1 litre
What’s a spirometer?
It is a machine that scientists use to measure the volume of air breathed in and out
What can you work out from the graph produced by a spirometer?
You can work out tidal volume, ventilation rate and other measures of breathing
How does pulmonary tubercolosis cause a reduction in tidal volume?
- TB bacteria causes immune system cells to build wall around bacteria in lungs. This forms small hard lumps called tubercles
- Infected tissue within tubercle dies and gaseous exchange surface is damaged so TV is reduced
- TB also causes fibrosis, furthering reducing TV
What are the common symptoms of pulmonary tubercolosis
- Coughing up blood and mucus
- Chest pains
- Shortness of breath and fatigue
What is fibrosis?
Fibrosis is the formation of scar tissue in lungs, as a result of an infection or exposure to substances like asbestos or dust
- scar tissue is thicker and less elastic than normal lung tissue
What are the consequences of fibrosis?
- Lungs are less able to expand, so can’t hold asmuch air - reduced TV and FVC
- Reduction in rate of gaseous exchange - diffusion is slower across thicker scarred membrane
What are the symptoms of fibrosis?
FIBROSIS 1. Shortness of breath 2.Dry cough 3 Chest pain 4. Fatigue and weakness
Why do fibrosis sufferers have a faster ventilation rate than normal?
Because they need to get enough air into their lungs to oxygenate their blood.
What is asthma?
Respiratory disease where airways become inflamed and irritated (usually because of allergic reaction or pollen/dust)
What happens during an asthma attack?
- Smooth muscle lining the bronchiole contracts and large amount of mucus is produced
- This causes constriction of airways and reduces the diameter of the airways , making it difficult for sufferer to breathe.
- Air flow in and out of lungs is reduced, so less O2 enters alveoli and moves into blood. Reduced air flow means FEV1 is severely reduced
What are the symptoms of an asthma attack?
- Wheezing
- shortness of breath
- tight chest
What can an asthma attch be relieved by and how does this work?
By drugs in inhalers, which cause the muscle in the bronchioles to relax, opening up the airways
What is emphysema?
A lung disease caused by smoking or long-term exposure to air pollution - foreign particles in smoke become trapped in alveoli
How do foreign particles in smoke damage the alveoli?
- Causes inflammation, attracting phagocytes to the area. Phagocytes produce an enzyme that breaks down elastin (protein in walls of alveoli)
- Elastin is elastic and helps alveoli return to its shape after inhaling/exhaling air
- Loss of elastin means alveoli cant recoil to expel air as well (so air is trapped in alveoli)
- Also leads to destruction of alveoli walls, which reduces surface area of alveoli, so rate of gaseous exchange decreases
What are the symptoms of emphysema?
- Wheezing
- shortness of breath
- increased ventilation rate as they try to increase the amount of oxygen reaching the lungs
Summarise the general effect of diseases like TB, fibrosis, asthma and emphysema?
- All reduce the rate of gas exchange in alveoli
- Less oxygen can diffuse into blood so body cells receive less oxygen and rate of aerobic respiration is reduced.
- Therefore, less energy is released and sufferers feel tired and weak
