3.1.1 MODULE 3 EXCHANGE AND BREATHING OCR

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  • Created by: Davina1st
  • Created on: 07-02-21 15:01
Why do single celled organisms not need specialised exchange surfaces?
Metabolic activity is low, so O2 and CO2 production of cell are low. The organism has a large SA:V.
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What happens to the SA:V ratio as an organism gets bigger? What does this mean?g
As an organism gets bigger, the the SA:V ratio gets smaller. So gases can’t be exchanged fast enough or in large amounts enough to survive.
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What do all effective exchange surfaces have?
Increased SA, thin diffusion barriers, good blood supply and ventilation to maintain a diffusion gradient.
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Why does ventilation create an efficient exchange surface?
Ventilation helps to maintain a steep concentration gradient, which means more efficient diffusion of gases and other substances.
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Why does a good blood supply create an efficient exchange surface?
The steeper the conc gradient, the more diffusion takes place, having a good blood supply means that substances are constantly being delivered to and removed from the exchange surface.
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Why do humans need a specialised gas exchange system?
They are very large, with a large volume of cells. All the cells need a constant flow of oxygen for respiration as they are highly metabolic. CO2 is released which needs to be removed.
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Name the key structures of the mammalian gas exchange system.
Nasal cavity, trachea, bronchus, bronchioles, alveoli.
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How does the naval cavity specialised to carry out its function?
The nasal cavity has a large SA:V with a good blood supply which warms the air to the surrounding body temperature. A hairy lining, secretes mucus to trap dust, dirt and bacteria=protection of lung tissue. Moist surface= Increased humidity+Less evap
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How is the trachea specialised to carry out its function?
Trachea=airway carrying warm/moist air to chest. Wide tube with rings of strong cartilage=support and strength. Lined with ciliates epithelium and goblet cells. Goblet cells secrete mucus to trap dirt and cilia beat =moves mucus to throat (swallowed)
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How is the bronchus specialised to carry out its function?
The trachea divides to form the left bronchus to left lung and right bronchus to right lung. Has similar structure to trachea with supporting rings of cartilage for strength.
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How are the bronchioles specialised to carry out there function?
The bronchi divide to form small branches =bronchioles. They have no cartilage rings, the walls contain smooth muscle, which contracts to close up bronchioles and relax to open them up=changes amount of air entering.Flattened epithelium=Gas exchange
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How are the alveoli specialised to carry out there function?
They are tiny air sacs 200-300um diameter. Unique to mammalian lungs. Flattened epithelial cells+collagen+elastic fibres. Elastic fibres allow alveoli to stretch as air is drawn in+squeeze air out. =ELASTIC RECOIL
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What are the main adaptions of the alveoli to create an effective gas exchange system?
Large SA, thin layer=short diffusion distance. Good blood supply=steep concentration gradient and more diffusion of o2 in and co2 out. Good ventilation= steep diffusion gradients.
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Describe lung surfactant and its role
Lung surfactant covers the inner surface of the alveoli, it is in a solution with water and salts. It enables the alveoli to stay inflated. O2 dissolves into water then blood but water can evap into air in alveoli. Surfactant= minismes water loss
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Explain how inspiration (breathing in occurs)
Diagram contracts, so it is low and flat. External intercostal muscles move ribs up and out. Vol of thorax increases so pressure in thorax is reduced. Because pressure is lower than outside air, air is brought in through nasal passages.
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Explain how expiration (breathing out) occurs - PASSIVE
Muscles of diagram relax so it returns to come shape, external intercostal muscles relax so ribs moved down and out. Elastic fibres in alveoli return to normal length= Decreased vol of thorax= increased pressure. So air travels out= Pressure in+out
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Explain how expiration (breathing out occurs - ACTIVE
Could occur during/ after exercise. Intercostal muscles contract pull ribs down and in = decrease in vol of thorax which forces air out as the air outside is lower pressure than inside.
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What are the symptoms and triggers of asthma?
Symptoms = wheezing, coughing, struggling to breathe and blue fingertips. Triggers = house dust mites, smoke, pollutant and stress.
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What is the cause of asthma?
Cells that line bronchioles release histamines = enflamed epithelial cells = goblet cells secrete more mucus + smooth muscle contracts. Airways are narrow and full of mucus.
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What is a treatment of asthma?
Preventers - steroids to reduce stress in airways. Relievers - immediate relief from symptoms = causes smooth muscle to relax and open up airways. Drugs are delivered into system by inhaler.
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Give three ways the capacity of the lungs can be measured
Peak flow meter-measures rate at which air is expelled from lungs. Vitalographs - patients breathes in and out quickly through mouthpiece and graph of how much air is created. Spirometer - used to measure different lung volumes/breathing patterns.
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What are the different aspects of the Kung volume that can be measured by a spirometer?
Tidal volume, vital capacity, inspiratory reserve volume, expiratory reserve volume, residual volume and total lung capacity.
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What is tidal volume?
The volume of air that moves in and out of air lungs with each resting breath.
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What is vital capacity?
Volume of air that can be breathed in when the strongest exhalation is followed by the deepest inhalation.
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What is inspiratory reserve volume?
Maximum volume of air you can force out of your lungs after you have exhaled normally.
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What is expiratory reserve volume p?
Extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.
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What is residual volume?
Volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.
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What is total lung capacity?
Sum of the vital capacity and the residual volume.
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What is breathing rate? How is it calculated?
The number of breaths taken per minute. Ventilation rate is total volume of air inhaled in one minute. Ventilation rate = tidal volume x breathing rate (per min)
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Why do insects need a specialised exchange system?
Tough outer layer of insects=exoskeleton, it means that little to no gaseous exchange can take place. They have no blood supply, so oxygen cannot be carried through the body of an insect. They are small but very active.
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Describe how a spirometer can be used to measure different volumes?
Chamber filled with o2 floats on water, nose cap ensures all air goes back into tank, breathe in chamber goes down, breath out chamber goes up, movement of chamber=graph, soda lime absorbs co2 exhaled, total volume in tank decrease as co2 absorbed.
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How does gaseous exchange take place in insects?
Air enters/leaves through spiracles along abdomen/thorax,when bug is inactive spiracle is closed prevents water loss. Tracheae lead away from spiracle, lined in chitin. Then form tracheoles, air moves by diffusion to end where there is tracheal fluid
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What are spiracles? Insects
Small openings found along thorax/ abdomen which let air into the body of insect
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What is chitin? Insects
Material that lines the walls of the tracheae it is impermeable to gases
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What is the tracheoles? Insects
Tracheae branch to form tracheoles, which are a single elongated cell with no chitin along the walls. 0.6 to 0.8 um in diameter.
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What is tracheal fluid? Insects
Found at the end of the tracheoles, it causes limited penetration of air for diffusion.
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Why do fish need a specialised gas exchange system?
Water is 100 times denser than air and 100 times more viscous. This causes a slow rate of diffusion which is overcome by constantly moving.
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Describe how gills are specialised to carry out their function
A continuous flow of water is maintained over the gills. They have a larger surface area, good blood supply and thin layers. They are contained in a gill cavity and protected by an operculum. Gill filaments branch into Gill lamellae=Exchange surface
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What is ram ventilation?
A technique used by fish that rely on continuous movement to create a continuous flow of water over the gills.
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How do bony fish (and fish that don’t rely on movement) maintain a continuous flow of water over the gills?
Buccal cavity lowered, increase of volume and decrease pressure, water moves in. Operculum cavity expands=lower pressure. Floor moves up=increase pressure water moves over gills. Mouth closes= more pressure in operculum cavity, water moves over gills
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Why is it a good thing that the tips of adjacent gill filaments overlap?
Creates increased resistance to the flow of water over the gills surface, which slows down movement of water= more time for gaseous exchange to take place.
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Why is a countercurrent flow better than a parallel flow?
Countercurrent flow means a steep concentration gradient is maintained= more efficient gas exchange. Oxygen continues to diffuse the whole width of the gills whole way down the concentration gradient
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Card 2

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What happens to the SA:V ratio as an organism gets bigger? What does this mean?g

Back

As an organism gets bigger, the the SA:V ratio gets smaller. So gases can’t be exchanged fast enough or in large amounts enough to survive.

Card 3

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What do all effective exchange surfaces have?

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Preview of the front of card 3

Card 4

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Why does ventilation create an efficient exchange surface?

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Card 5

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Why does a good blood supply create an efficient exchange surface?

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