3:Exchange and Transport Flashcards
What are the standard exchange surface characteristics?
- Large SA:V
- Thin, for a short diffusion pathway
- Moist, allows molecules to dissolve so they can diffuse
- Maintain a steep concentration
What happens to the SA:V the bigger an organism?
Surface area to volume ratio decreases
What is the pathway of air entering a locusts?
Spiracle —> Trachea —> Tracheole —> Indiviual cells
Describe the intake of airflow process in a locust?
1) Air flows through spiracles (each segment has a pair of spiracles)
2) Air travels from the tracheal tubes which run from the body surface to the tissues
3) Tracheal tubes branch off into a series of tracheoles which reach cells/tissue
What are the two ways gas exchange takes place in an insect?
- Diffusion gradient
- Ventilation by rhythmic abnormal movements
How does ventilation by rhythmic abnormal movements help gas exchange?
It further speeds up the exchange of respiratory gases by generating mass movement in and out of the tubes
Why do insects have a separate tracheal system instead of relying on blood to transport oxygen around the body?
- Insects have an open circulation -> they cannot easily direct the flow of blood to tissue that need it most
- Insects rely on diffusion and exchange of oxygen as a gas is more efficient
Why is the tracheal fluid withdrawn into the body when the tissue is very active?
This is to increase the surface area over which the exchange can occur
What is trachea in an insects exchange system lined with?
Chitin
Describe the pathway of gas exchange in fish.
1) The mouth is opened and the floor of the buccal cavity is lowered, this increases the volume and decreases the pressure so that water flows in
2) The volume of the operculum cavity is then increased and its pressure decreases. The floor of the buccal cavity starts to move up to increase the pressure
3) Water flows from buccal cavity to the operculum cavity where the gills are found
4) Gases can be exchanged between the blood in blood capillaries of the lamellae and water
Why is a countercurrent flow system used in fish?
In parralel flow, the concentration gradient will level out when the oxygen level in the blood and water are at 50%. Therefore diffusion stops.
However in countercurrent flow, the blood will continue to absorb oxygen from water as the concentration gradient doesn’t level out.
What are the adaptations of gills?
- several gill filaments and gill lamellar to increase the surface area
- gill filaments are thin for short diffusion path
- gill lamellar have a good blood supply and countercurrent mechanisms to maintain a high concentration gradient
Outline the passage of air in the mammalian gas exchange system?
Nose/mouth —> Trachea —> Bronchi —> Bronchioles —> Alveoli
What are the features of the trachea?
- Lined with ciliated epithelium
- Surrounded by ‘C’ shaped cartilage rings
- Surrounded by smooth muscles
Why does the trachea have ‘C’ shaped cartilage rings?
Protects it from collapse and provides support
What does the trachea have smooth muscles?
They contract and relax to increase and decrease the diameter of the trachea
What are the features of the bronchi?
- branched into 2 bronchus
- lined with ciliated epithelium (but less goblet cells than trachea)
- cartilage is irregular not in rings allowing more flexibility
- contains elastic fibres and smooth muscles
What are the features of the bronchioles?
- no cartilage or goblet cells
- walls contain smooth muscles
- it has elastic fibres
What is the passage of air in the different types of bronchioles?
Bronchiole —> Terminal Bronchiole —> Respiratory Bronchiole —> Alveolar Duct
What are the features of the alveoli?
- moist lining
- single cell thick lining of epithelial cells
- surrounded by very thin blood capillaries (usually one cell thick)
- contains elastic fibres
- contains lung surfactants
Why does the alveoli have a moist lining?
So gases can dissolve and diffuse faster
What is the lung surfactant?
A phospholipid that coats the surfaces of the lungs
Why do alveoli need lung surfactants?
Without it, the watery lining of the alveoli would create a surface tension which would cause them to collapse.
Is inspiration (inhaling) an active or passive process?
Active process
What is the process of inhalation?
1) The external intercostal muscles contract and the diaphragm contracts and flattens. This causes the ribcage to move up and out
2) Thoracic volume increases
3) Thoracic pressure decreases
4) Air flows into the lungs to equalise the pressure difference
Is expiration (exhaling) an active or passive process?
Largely passive process
What is the process of exhalation?
1) The external intercostal muscles relax and the diaphragm relaxes and moves up. This causes the ribcage to move down and in
2) Thoracic volume decreases
3) Thoracic pressure increases
4) Air flows out of the lungs to equalise the pressure difference
What is tidal volume?
The volume of air breathed in (or out) in one normal breath
What is the breathing rate?
The number of breaths per minute
What is the ventilation rate?
Total volume of air breathed in and out in one minute
What is the vital capacity?
The largest volume of air you can breathe in or out in one breathe
What is the inspiratory reserve volume?
Extra air above the tidal volume you can breathe in a forced breath
What is the expiratory reserve volume?
Extra air you can breathe out in a forced breath
What is the residual capacity?
Air you cannot empty from your lungs
What is the total capacity?
The sum of the vital capacity and residual capacity
How do you measure oxygen consumption?
1) Use soda lime to absorb the carbon dioxide
2) The trace will gradually fall as the breathing rate or volume in the chamber reduces
3) Measure how much the trace drops in a set time
4) Work out the volume of oxygen consumed per minute
Explain the need for transport system in multi-cellular animals?
1) SA:V is too small so diffusion is too slow
2) Distance is too great —> cannot rely on diffusion alone
3) High metabolic rate and waste production (more metabolically active so higher demand for nutrients)
What are the features of a good transport system?
1) Fluid or medium to carry nutrients + oxygen
2) A pump to create pressure to push the fluid
3) Exchange surfaces to enable oxygen + nutrients to enter the blood and be removed
4) Tubes or vessels to carry the blood
What does an open system consist of?
- a heart that pumps a fluid called haemolymph through shirt vessels into a large cavity called the haemocoel
- blood is not always enclosed in blood vessels
Why can’t humans have an open system?
1) Humans are too large to rely on an open system whereas insects are small so blood doesn’t meed to travel as far.
2) An open system can’t maintain a pressure so it’s slow
3) In an open system the tissue and cells are bathed in blood whereas I’m a closed system the vessels allow blood to be carried out to specific organs
5) A closed system can respond to external changes e.g. vasodilation
What is a closed circulatory system?
When the blood is fully enclosed within the blood vessels at all times
What are the advantages of a closed circulatory system?
- maintains high blood pressure —> regulate pressure as well
- blood can be deviated
- respond to external stimuli (thermoregulation)
What is a single closed circulatory system?
Blood flows only once through the heart in one circulation.
Only two chambers (atrium and ventricle)
What is the pathway of blood in the single closed circulatory system of fish? (EDIT)
Deoxygenated blood leaves the ventricle to gill capillaries, blood gets oxygenated by gaseous exchange. The gills have many capillaries for gas exchange so the blood pressure is low after going through the gill capillaries, blood gets oxygenates by gaseous exchange. The gills have many capillaries for gas exchange so the blood pressuremismlowmafteer going through the gill cappilaries. Low pressure blood then goes directly to he body which has a large number of cappilaifes.
What does is mean when it says the cardiac muscles in the heart are myogenic?
They can initiate contractions by generating their own electrical impulse
What are the two circulations in double circulation?
- Systematic Circulation
- Pulmonary Circulation
What happens during systematic circulation?
1) The left ventricle contracts
2) The semi lunar valve opens
3) Oxygenated blood enters the aorta
4) Aorta transports oxygenated blood to upper and lower parts of the body
5) Cells use oxygen for respiration and the blood gets deoxygenated
6) Deoxygenated blood is transported by superior and inferior vena cava to the right atrium
7) The right atrium contracts, tricuspid valve opens and the deoxygenated blood enter the right ventricle
What happens during the pulmonary circulation?
1) The right ventricle contracts
2) Semi-lunar valve opens
3) Deoxygenated blood enters the pulmonary artery
4) The pulmonary artery transports the deoxygenated blood to the lungs
5) Gas exchange takes place in the lungs, blood gets oxygenated
6) Oxygenated blood is transported via pulmonary vein to the left atrium
7) Through the bicuspid valve it goes to the the left ventricle
What are the three stages of the cardiac cycle?
- Atrial systole
- Ventricle systole
- Diastole
What happens during the atrial systole?
1) Blood flows into both atria and their volume increases, the muscles of the atria contract to increase the pressure
2) The pressure behind the valves is greater forcing the valves to open
3) Blood starts to flow from atria to ventricles
4) The semi-lunar valves in the vena cava and the pulmonary valve close
5) Pressure starts to decrease in the atrium
What happens during the ventricular systole?
1) The muscles of ventricles contract
2) The pressure inside the ventricles increases
3) The tricuspid & bicuspid atrioventricular valves close
4) The semi-lunar valves in the aorta and the pulmonary artery open
5) Pressure decreases
What happens during the diastole?
1) Pressure in the ventricles decrease
2) Semi-lunar valves in the aorta and the pulmonary arteries close
3) All the heart muscles relax
4) Blood flows into the atria from vena cava and pulmonary vein
5) Blood pressure remains low inside the atria and ventricles
What are valves controlled by?
The pressure gradient
What causes a valve to open?
High pressure behind the valve
What causes the valves to close?
High pressure in front of the valve.
What is the ventricular pressure during the atrial systole?
Low pressure
Why is the ventricular pressure low during the atrial systole?
Blood hasn’t entered the ventricles
What is the ventricular pressure like in the ventricular systole?
Increases rapidly
Why does the ventricular pressure increase rapidly during the ventricular systole?
The ventricles contract
What happens to the valves during the ventricular systole?
Atrioventricular valves close and semi-lunar valves open
What is the ventricular pressure during the diastole?
Low as it is a passive process
What is the atrial pressure during the atrial systole?
Gradually increasing
Why does the atrial pressure gradually increase during the atrial systole?
Because the atria contracts
What is the atrial pressure during the ventricular systole?
Starts to decrease
Why does the atrial pressure start to decrease during the ventricular systole?
Because the blood flows into the ventricles and the atrial muscles relax
What is the atrial pressure during the diastole?
Slightly increases at the beginning
Why does the atrial pressure slightly increase at the beginning of the diastole?
Because the blood flows passively into the aorta from the vena cava and the pulmonary vein
What is the aortic pressure in the atrial systole?
The pressure remains the same as the blood hasn’t entered the aorta yet
What is the aortic pressure in the ventricular systole?
Starts to increase
What is the aortic pressure in the diastole?
Decreases
What is cardiac output?
The amount of blood pumped around the body
How do you calculate cardiac output?
Cardiac output = Stroke volume x heart rate
What is the stroke volume?
The volume of blood pumped by the left ventricle in each heart beat
What is the heart rate?
The number of times the heart beats per minute
What happens to the membrane of muscle cells when they are at rest?
It becomes polarised
What happens to the membrane of muscle cells when the charge distribution is reversed?
The membrane is depolarised and it causes them to contract
In terms of electrical activity, what happens during the atrial systole?
- The sino-atrial node (SAN) sends a wave of excitation (depolarisation) throughout the atria
- This causes the walls of the atria to contract almost simultaneously
Where is the sino-atrial node (SAN) found?
In the upper left wall of the right atrium
In terms of electrical activity, what happens during the ventricular systole?
- SAN sends electrical excitations to the atrio-ventricular node (AVN), causing the AVN to send excitation through the bundle of His and then into the Purkyne tissue.
- This causes depolarisation of cardiac muscles
- There is a time gap between the generation of waves of excision by the SAN and the receival of excitations from the AVN
What does the P wave represent in an ECG?
- The depolarisation of the atria
- The atrial systole
What does the QRS complex represent in an ECG?
The electrical impulses as it spreads through the ventricles and indicates the ventricular depolarisation
What does the T wave represent in an ECG?
- the diastole
- the ventricular repolarisation
What is bradycardia?
Slower than normal heart beat - less than 60bpm
What is tachycardia?
Faster than normal heart rate - more than 100bpm
What is ectopic beat?
Extra beats, followed by gaps
What is atrial fibrillation?
Irregular heartbeat rhythm
Why does blood pressure drop from aorta to arteries and from the arteries to capillaries?
- distance from heart increases
- blood flows into larger number of vessels
- total cross-sectional area of the arteries is greater than the aorta
- total cross-sectional area of capillaries is greater than the aorta/arteries
Why is it important that the blood pressure drops in the capillaries?
- capillary wall is only one cell thick
- high pressure would burst/damage capillary walls
- reduce chance of tissue fluid build up (causing oedema)
What is the main protein found in blood plasma?
Albumins
What are albumins?
Transport protein found abundantly in the blood plasma
What is hydrostatic pressure?
Pressure inside the blood
What causes hydrostatic pressure?
The contractions of the heart
How is tissue fluid formed from plasma?
- The effect of hydrostatic pressure is greater than the oncotic effect at the arterial end, which means water (with some dissolved substances) is forced out through the capillary wall as it has pores.
- The effect of oncotic pressure is greater than the hydrostatic pressure at the venous end, therefore some fluid returns back to the capillaries.
- Valves/pores at lymph vessels allow fluid and proteins out of the tissue fluid into lymph vessels
What is lymph?
A colourless/pale yellow fluid similar to tissue fluid (but contains more lipids)
What happens to excess tissue fluid that doesn’t return to the capillaries?
The excess tissue fluid drains into the lymphatic system, where it is formed as lymph
What does the lymphatic system consist of?
- lymphatic capillaries and vein-like lymph vessels (containing valves)
- lymph nodes
- lymphatic tissue in the spleen, thymus and tonsils
What are lymph nodes?
Sac like organs that trap pathogens and foreign substances, and which contain large number of white blood cells
What could happen in the tissue of a person if the drainage into the lymph glands were inefficient?
- Valves in lymph vessels allow fluid in from the tissue fluid
- if this doesn’t happen, the fluid collects and the area around the tissue swells leading to oedema
What is pressure of tissue fluid like?
Low
What is pressure of lymph?
Low
What makes up 95% of the dry mass of red blood cells?
Haemoglobin
What is the concentration of oxygen in the blood measure by?
Partial pressure
What is partial pressure?
The amount of pressure exerted by a gas relative to the total pressure exerted by all gases
Explain the S-shaped curve in the oxygen disassociation graph.
1) In the lungs, there is high partial pressure of oxygen so one molecule of it can diffuse into haemoglobin and associate with the haem group
2) This causes a conformational change in the haemoglobin molecule
3) More oxygen can now associate with the haem (2nd O2 + 3rd O2)
4) The haemoglobin becomes saturated so it is more difficult for the fourth molecule to attach
5) At low partial pressure of oxygen it’s hard for it to attach
What is foetal haemoglobin?
A special form of haemoglobin found in foetal bloodstream.
-> it has a higher affinity for oxygen than adult haemoglobin
What does it mean when foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin?
Foetal haemoglobin takes up oxygen in lower partial pressure of oxygen in the placenta because adult oxygen will dissociate from adult oxyhaemoglobin
What is the benefit for foetal haemoglobin having a higher affinity for oxygen.
This helps maximise oxygen uptake from the mother’s bloodstream, which has already lost some of its oxygen by the time it reaches the placenta.
What is myoglobin?
A molecule with a similar structure to haemoglobin, but with only one haem group
Why is myoglobin found in muscle cells?
It has a very high affinity for oxygen (even at very low partial pressure).
-> this means OHb will only dissociate when oxygen levels are low
Therefore it acts as an oxygen reserve
What happens to carbon dioxide in the blood?
1) 5% is carried dissolved in plasma
2) 10% bunds with globin groups in erythrocytes
3) 85% reacts with water
What is the result of the carbon dioxide that binds with globin groups in erythrocytes?
A molecule called carbaminohaemoglobin
What happens when carbon dioxide reacts with water in the blood?
1) The reaction is catalysed by an enzyme in erythrocytes to form carbonic acid.
2) This disassociates into hydrogen carbonate ions and H+ ions.
3) The H+ ions bond with haemoglobin to form haemoglobic acid and the hydrogen carbonate diffuses out into the plasma.
What is the enzyme that catalyses the reaction between water and carbon dioxide in the blood?
Carbonic anhydrase
What are the equations for the reaction between carbon dioxide and water in blood?
1) CO2 + H2O —> H2CO3
2) H2CO3 —> H+ + HCO3-
3) H+ + HB —> HHb
Q
The Bohr shift lowers the affinity of haemoglobin for oxygen so at the same partial pressure there is a lower percentage saturation of oxygen so there is more oxygen dissociation release oxygen for respiring tissue
What is the chloride shift?
Chloride ions moves into the erythrocytes cytoplasm from the plasma to balance out the electrochemical distribution.
What is the xylem?
One continuous tube (lined with water impermeable lignin) to transport water and mineral ions via the transpiration stream
How is the xylem being made of dead cells useful for its function?
- no cross wall, cells are joined end to end so are continuous
- hollow so no contents (organelles and cytoplasm)
How is the xylem being lined with lignin useful for its function?
- strengthens the xylem wall to prevent collapse of oxygen
- waterproof cells, reduces lateral loss of water
- increases capillarity
- improves adhesion (of water molecules)
- spiral pattern allows flexibility and prevents stem branching
How is the xylem having pits useful for its function?
- pits allows water to move in and out
- supply water to other tissues and types of cells
What is cohesion tension theory?
- Water molecules and cohesive to each other and adhesive to the lignin
- The narrow lumen of the xylem creates a capillary action.
- Water in the xylem is under tension and is pulled up as one continuous column of water
Outline the sequence of events in the transpiration stream?
1) Root hair cells absorb water by osmosis
2) This creates a high hydrostatic pressure in the roofs
3) Water enters the xylem and moves up through the xylem in the stem
5) Water moves from the xylem to leaf cells
6) Water evaporates from the leaf cells to air spaces in the spongy mesophyll tissue
7) Water evaporates from air spaces by transpiration
How is the root hair adapted for water and mineral uptake?
1) It’s long
2) Thin cell wall - short diffusion path
3) Large surface area
4) Lack of water proof layer
5) Many root hair cells present (abundant)
6) Low water potential
7) Contains channel and carrier proteins
8) Has many mitochondria
What are the three pathways for water uptake in plants?
1) Apoplast pathway - via cell wall
2) Symplast pathway - via cytoplasm
3) Vacuolar pathway - via vacuole
What is the symplast pathway?
This is the movement of water through the cytoplasm.
How does water move in the symplast pathway?
Water travels through the cell wall, partially permeable membrane and then enters the cytoplasm.
Water travels through the plasmodesmata and enters adjacent cells
What are plasmodesmata?
Gaps in the cell wall
What is the apoplast pathway?
This is the movement of water through the cell wall and intracellular spaces.
This is the fastest pathway as the cell wall is fully permeable.
What is the fastest pathway of water uptake?
The apoplast pathway, as the cell wall is fully permeable
What is the slowest pathway of water uptake?
The vacuolar pathway
What is the the vacuolar pathway?
This is the same as the symplast pathway but water moves through the cells vacuoles in addition to the cytoplasm.
Water can move into the sap in the vacuole, through the tonoplast
What is the Casparian strip?
An impermeable layer of suberin (a waxy material). As a result all water in the apoplast pathway is forced into symplast pathway
What is transpiration?
The loss of water vapour by diffusion into the atmosphere via stomata from leaves.
What is the transpiration stream?
Water loss by transpiration must be replaced by water travelling up the xylem from the roots.
What are uses of the transpiration stream?
1) needed for photosynthesis
2) keeps cells turgid so plants don’t wilt
3) keeps leaf cells turgid so they can absorb the maximum amount of light
4) carries minerals
5) evaporation of water helps keep the plants cool
