Exchange And Transport
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- Created by: BF
- Created on: 04-05-14 22:41
Why do multicellular organisms need specialised exchange surfaces, and single celled organisms do not?
Single celled organisms can exchange gasses etc. across their outer surface (large SA/V ratio) whereas multicellular organisms have smaller SA/V ratio and cells need more supplies- greater distance form surface to centre of the organism.
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Why do muticellular organisms need a transport system
Larger area to exchange more substances
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What makes an efficient exchange surface?
Large surface area, thin barrier/wall to reduce diffusion distance, fresh supply/quick removal of molecules to maintain gradient
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What are the features of the lungs?
Trachea, Bonchi, Bronchioles, Alveoli
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Where is the ciliated epithelium in the trachea/bronchi/bronchioles/alveoli?
Only alveoli do not have cilated epithelium- inner part of the airway to clear mucus
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Where is the cartilage in the trachea/bronchi/bronchioles/alveoli?
Trachea- Cartilage is in a c-shape to allow both strength and controlled movement, Bronchus- Plates of cartilage, less regular than in trachea
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Where are the goblet cells in the trachea/bronchi/bronchioles/alveoli?
Among the ciliated epithelium
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Where are the smooth muscle and elastic fibres in the trachea/bronchi/bronchioles/alveoli?
Between cartilage and ciliated epithelium, thick loose tissue
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What is the function of cartilage?
Structure, supports trachea and bronchi, holding them open,, prevents collapse during inhalation, move neck without constricting airways
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What is the function of cilia?
Waft mucus up the airway to the back of the throat, stomach acid kills bacteria.
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What is the function of goblet cells?
Secrete mucus to trap particles in the air (e.g. pollen and bacteria)
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What is the function of elastic fibres?
Help widen the airway in response to the constriction of the smooth muscle
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What is the function of smooth muscle?
Contracts the airways, makes lumen narrower (particularly in the bronchioles), stops inhalation of harmful chemicals, however allergic reactions trigger this action
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Describe the mechanism of breathing (inspiration and expiration)
Diaphragm and intercostals muscles (ribs) contract and relax
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What is tidal volume?
The volume of air moved in and out of the lungs with each breath when you are at rest
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What is vital capacity?
Largest volume of air that can be moved in and out of the lungs in any one breath
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How does a Spirometer measure tidal volume/vital capacity/breathing rate etc?
The reduction in chamber total volume/Time taken for this reduction/60 seconds(i.e. per minute)
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What is a single circulatory system?
A circulation where blood flows through the heart once during each circulation of the body (e.g. fish)
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What is a double circulatory system?
A transport system where blood flows through the heart twice for each complete circulation of the body (e.g. humans)
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What is an open circulatory system?
Blood is not carried in vessels, body movement helps circulate the blood
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What is an closed circulatory system?
Blood is carried in vessels, tissue fluid bathes vessels, more pressure, O2 and nutrients delivered quicker.
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Describe the structure of the heart
PICTURE
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Why does the left side of the heart have thicker walls?
Needs to withdstand higher hydrostatic pressure- the side of the heart which pumps blood to the rest of the body
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What are the stages of the cardiac cycle?
Diastole, Atrial Systole, Ventricular Systole
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What happens during Diastole?
Heart relaxes, atria followed by ventricles fill with blood
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What happens during Atrial Systole?
Atria contract together, pushes blood into the ventricles till full, atrioventricular valves shut to prevent backflow.
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What happens during Ventricular Systole?
All 4 valves shut, ventricles contract at the apex (base) pushing blood through arteries, semi lunar valves open and blood is pumped to the rest of the body, the cycle begins again.
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How does the heart contract?
Myogenic muscle,SAN initiates wave of excitation,spreads across atria which contract (atrial systole), between atria + vents. is a disc, does'nt conduct impulse, impulse reaches AVN,delays wave,sent down purkyne tissue,ventricles contract from apex
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How does the heart contract?
PICTURE
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Describe the structure of an artery
Lumen, endothelium, elastic fibres, smooth muscle, collagen fibres
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Describe the structure of an vein
Same as an atery but with a wider lumen
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Describe the structure of an capillary
Lumen + Endothelium, very thin walls
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What is the function of an artery?
Carry oxygenated blood away from the heart, high pressure
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What is the function of a vein?
Carry deoxygenated blood to the heart, low pressure
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What is the function of a capillary?
Exchange of materials between the blood and cells of tissues via tissue fluid
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How is tissue fluid formed from plasma?
Organ/Tissue surrounded by capills, arterial end of capill. high hydrostatic press, pushes t.f. (plasma, dissolved nutrients + O2) out of capills. Platelets + erythrocytes stay in capill. too large for gaps. T.f. cover body cells, allows diffusion
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How does the tissue fluid return to the blood?
At venous end of capill. osmotic pressure overcomes hydrostatic pressure, water moves down the water potential gradient and back into the blood.
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How does haemoglobin carry oxygen?
Blood cells contain haemoglobin (4 subunits) which takes up oxygen, iron atoms have an affinity for O2 (4 molecules)
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What is dissociation?
Body cells need O2 for aerobic respiration, oxyhaemoglobin must release O2
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How much oxygen can haemoglobin take up?
This depends on the partial pressure- i.e. at the arterial end of a vessel there is a higher partial pressure, at venous end there is a lower p.p.- Produces and ‘S shape’ oxyhaemoglobin dissociation curve
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Describe the dissociation curve
At low pO2, O2 cannot reach haem groups, there is than a steep rise due to the diffusion gradient increasing and oxygen can bind to the haem groups, curve then levels off near 100% saturation, hard for O2 to bind to the 4th haem group
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Why does fetal haemoglobin have a higher affinity for oxygen than adult haemoglobin?
The fetal haemoglobin has to be able to pick up oxygen in the placenta where there is a low partial pressure
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How does haemoglobin carry carbon dioxide?
5% directly dissolved in the plasma, 10% combined with haemoglobin (carbaminohaemoglobin), 85% transported in the form of hydrogencarbonate ions (HCO3-)
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How are hydrogencarbonate ions (HCO3-) formed?
Carbonic anhydrase (enzyme) combines CO2 + H20, forms H ions + HCO3- ions, which diffuse out of red blood cell- Oxyhaemoglobin dissociates from O2 due to H ions & The H ions bond with haem, forms haemoglobinic acid, chloride shift maintains charge
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What is the Bohr Effect?
The effect of carbon dioxide concentration on the affinity of haemoglobin for oxygen (changes the shape of the curve) Oxyhaemoglobin releases oxygen more readily
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Where is xylem found in the root of a dicotyledonous plant?
PICTURE
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Where is xylem found in the stem of a dicotyledonous plant?
PICTURE
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Describe the structure of xylem vessels
Xylem vessel elements- long cells with thick walls impregnated with lignin, which which waterproofs walls, cells die and contents decay, makes a tube supported by the lignin. It also has living parenchyma cells.
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Describe the structure of phloem
Small cytoplasm + no nucleus, alined forms tube to transport sap. Cross-walls at intervals, perforated to allow sap to flow. Companion cells, large nuclei + dense cytoplasm, mitochondria produce ATP for loading sucrose. CC + STE linked by plasmodesma
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What factors affect the transpiration rate? (8)
Number of leaves, Number size and position of stomata, Presence of cuticle, Light, Temperature, Relative humidity, Air movement or wind and Water availability
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Other cards in this set
Card 2
Front
Why do muticellular organisms need a transport system
Back
Larger area to exchange more substances
Card 3
Front
What makes an efficient exchange surface?
Back
Card 4
Front
What are the features of the lungs?
Back
Card 5
Front
Where is the ciliated epithelium in the trachea/bronchi/bronchioles/alveoli?
Back
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