Transport In Animals Flashcards
Explain how spiracles in insects support gas exchange
Insects are covered with a protective exoskeleton made up of the the polysaccharide chitin.
Gases such as oxygen and carbon dioxide cannot easily pass through the exoskeleton . As a result there are small openings on the surface of the exoskeleton called spiracles which allow gas exchange
Spircale contain muscular sphincters which close to minimise water loss
Explain how the tracheae in insects support gas exchange
Spiracles lead into a network of tubes called tracheae which are relatively wide with a diameter of 1mm. The trachea extends down and along the insects body - short diffusion pathway
The walls of the tracheae are reinforced by spirals of chitin which prevents the tracheae from collapsing - constant flow of gas / volume maintained.
Explain how Tracheoles in insects support gas exchange
Tracheoles extend from the tracheae which are very fine tubes. They have a diameter of 1micrometre or less - short diffusion pathway
Each tracheole is a single cell that has extended to form a hollow tube into the insects cells - close proximity to cells.
The narrow diameter and close proximity of Tracheoles to cells result in a short diffusion distances for gases moving between the cells and Tracheoles. This allows oxygen to diffuse from the air into the Tracheoles to cells for aerobic respiration and CO2 is diffused out.
The huge number of Tracheoles provide a very large surface area for gas exchange. This allows insects to maintain a very rapid rate of aerobic respiration (during flight)
At the end of tracheoles contain a fluid called tracheal fluid which support anaerobic respiration
Explain how tracheal fluid in insects support gas exchange
The end of Tracheoles contain a tracheal fluid. During intense activity cells around Tracheoles undergo anaerobic respiration.
This produces lactic acid which lowers the water potential of cells.
The water moves into the cell which reduces the volume of targetable fluid, drawing air down into the Tracheoles. (More tracheole surface for gas exchange)
Explain the passive process of gas exchange in insects
Gas exchange is a passive process- oxygen diffuses down into the concentration gradient from the high concentration in the external air into the Tracheoles where the concentration Is lower.
Carbon dioxide diffuse down the concentration gradient from the relatively high concentration in the Tracheoles out to the external air
Explain how the size of insects support gas exchange
The small size of insects reduce the distance required for diffusion to take place
What problems do insects face in their gas exchange system and how is this prevented.
Walls of Tracheoles are moist and the ends of Tracheoles contain tracheal fluid. This means water vapor can diffuse out of an insect via the spiracles. However, each spiracle is surrounded by a muscular sphincter which closes the spiracle and reduces water loss.
Describe how some insects have evolved to increase the rate of gas exchange
Insects have three main body segments:
Some insects can contract muscles to change the volume of the thorax and abdomen which causes pressure changes in the Tracheae and Tracheoles pushing air in and out.
This bulk movement of air is called mass transport.
In some sections, the tracheae contain an expanded section called an air sac. The change in the volume of the thorax and abdomen through contraction can squeeze the air sacs causing air to move into the Tracheoles
Insects also use the air sacs when spiracles have been closed for water conservation
What are bony fish
bony fish are a large group of fish, which have evolved a skeleton made of bone.
What are example of bony fish
Tuna, cod,trout, salmon
Why do bony fish face significant problems during gas exchange
Bony fish are large and active organisms with a very high oxygen requirement
The large size of fish result in a very low surface area to volume ratio
Scaly surface of bony fish don’t allow gases to pass through
Why have bony fish evolved to have a Specialised gas exchange system
The concentration of oxygen in water is much lower than in air thus bony fish evolved to have a Specialised gas exchange system. This is done to extract the maximum amount of oxygen from water
Describe the operculum and opercular cavity
A flap of tissue slightly behind the head on either side of the fish is called an operculum. Behind that is the operculum cavity which contain gills.
Explain how gas exchange works within bony fish
Oxygen-rich water enters the fish through the mouth. The water passes over the gills where it diffuses from the water into the blood and carbon dioxide diffuses from the blood into the water. Finally, the water passes out through the operculum opening
Explain the structure of gills and gill filaments
Gills consist of several bony gills arches. Extending from each gil arch are a large number of Gil filaments.
Many pairs of Gil filaments extend from each gill arch. Gil filaments are covered with numerous gill lamellae which are also sometimes called gill plates
How does the gill lamellae exchange gas
Water flows between the gill lamellae. Oxygen diffuses from the water into the bloodstream and carbon dioxide diffuses from the blood stream into the water
How is lamellae adapted for efficient diffusion of gases
Gill lamellae have a massive surface area for gases to diffuse over.
There is a very short diffusion distance through the walls of the lamellae into the blood stream
Gill lamellae have any extensive network of blood capillaries
A Steep concentration gradient of oxygen is maintained as once oxygen is diffused into the bloodstream its carried away.
The counter-current exchange system: Blood with a low concentration of oxygen passes into the capillaries of the gill lamellae. As it passes through the gill lamellae, oxygen diffuses from the water into the blood. Oxygen- rich blood now passes out the gill lamellae and leave the gills ( the flow of blood is opposite to water flow). A steep concentration gradient for oxygen is maintained
Explain parallel flow
Initially, the water will have a much greater oxygen concentration than blood -high rate of diffusion of oxygen from the water into the bloodstream.
However, after a short distance the concentration of oxygen, is the same in both the blood and water. (Equilibrium takes place and diffusion stops_)
No more than 50% of the available oxygen in the water can diffuse into the blood
Why is a counter-current system good for gas exchange
There will always be a concentration gradient for oxygen.
This means that equilibrium is never reached.
Diffusion of oxygen takes place right across the length of the lamellae. 80% of oxygen in the water diffuses into the bloodstream
How do bony fish maintain constant water flow through the gas exchange system
Non-bony fish (sharks), the flow of water through the mouth and over the gills is caused by the fish swimming forward. However, bony fish allows water flow to occur even when the fish is not swimming.
When a bony fish opens its mouth, water flows into the mouth space (buccal cavity). The floor of the buccal cavity drops down increasing the volume available for water.
The fish shuts the operculum and increase the volume of the opercular cavity, which contains the gills.
Due to the increased volume, the pressure in the opercular cavity falls. At the same time, the floor of the buccal cavity lifts upwards
This increases the pressure of the water causing the water to flow over the gills in the opercular cavity
Now the fish closes its mouth and opens its operculum. At the same time, the sides of the opercular cavity squeeze inward on the water. This increases the pressure of the water, forcing it out of the operculum.
Why do mammals require a high oxygen demand
Low surface area to volume ratio
They are very active animals
They maintain their body temperature thus the require an increased rate of aerobic respiration
Explain the process of inhalation
The diaphragm contracts,flattening, and lowering. At the same time, the external intercostal muscles contract, moving the ribs upwards and outwards.
The volume of the thorax increases so the pressure in the thorax is reduced.
The thorax has a lower pressure than the atmospheric air, so air is drawn through the nasal passages, trachea, bronchi, and bronchioles into the lungs.
The air pressure in the lungs is now less than atmospheric pressure thus air is drawn into the lungs
Air is drawn into the alveoli and the elastic fibres between the alveoli stretch
Inhalation is an active process as it requires muscle contraction
Explain the process of exhalation
The muscles of the diaphragm relax so it moves up into its resting domed shape. The external intercostal muscles relax so the ribs move down and inwards under gravity. The elastic fibres in the alveoli of the lungs return to their normal length
The effect of all these changes is to decrease the volume of the thorax.
The pressure inside the thorax is greater than the pressure of the atmospheric air.
The elastic fibers between the alveoli also recoil, helping to push air out. (Elastic recoil)
The air moves out of the lungs until the pressure inside and out is equal again.
Exhalation is a passive process as muscle relax and don’t require energy
What is the function of the nasal cavity in humans
When humans breathe through their nose, air passes through the nasal cavity.
Hairs in the nasal cavity trap dust particles and warm and moistens the air before it enters the lung
Explain the structure of the trachea
The walls of the wide tube contain rings of cartilage, which is a firm and flexible material. This prevents the walls of the cartilage from collapsing when we inhale
The trachea is very close to the oesophagus. The cartilage in the trachea form a c-shape rather than complete rings. This allows food to pass down the oesophagus easily
The walls are lined with ciliated epithelial and goblet cells. Goblet cells secrete mucus which traps dust particles and pathogens.The ciliated epithelial cells have cilia extending from the cell membrane.
Explain the function of the trachea
The ciliated epithelial cells have cilia extending from the cell membrane. The beating of the cilia moves the mucus secreted by the goblet cells up where it is then swallowed and the dust and pathogens are digested by the stomach enzymes
-walls of trachea contain smooth muscle which contract and constrict the trachea. When the muscles relax, the trachea dilates . This changes the amount of air reaching the lungs
Explain the structure of the bronchus
-Similar structure to the trachea, with the same supporting rings of cartilage. However,smaller and the rings of cartilage are less abundant.
-walls of bronchus contain smooth muscle which contract and constrict the bronchus . When the muscles relax, the bronchus dilate. This changes the amount of air recahing the lungs
Explain the function of the bronchus
-walls of bronchus contain smooth muscle which contract and constrict the bronchus . When the muscles relax, the bronchus dilate. This changes the amount of air reaching the lungs
Explain the structure of bronchioles
- small bronchioles have no cartilage rings.
-walls of bronchioles contain smooth muscle which contract and constrict the bronchioles. When the muscles relax, the bronchioles dilate. This changes the amount of air recahing the lungs
-bronchioles are lined with a thin layer of flattened epithelium, making some gasesous exchange possible
bronchioles are much less smaller in size. They lead into air sacs called alveoli
Explain the structure of alveoli
-Each alveolus has a diameter of around 200-300 micrometre
Each alveolus consists of a layer of thin, flattened epithelial cell, along with some collagen and elastic fibres
The elastic tissue of the alveolus stretch and return to their resting size. To draw air in and out (elastic recoil)
Inner surface of alveoli is covered in a thin layer of solution of water, salts and lung surfactant
The Alveolar wall is one cell thick and flattened (squamous) {short diffusion pathway }
Moist thin lining (Oxygen can dissolve into solution)
What is the function of the alveoli
Gases diffuse in and out of the blood.
Oxygen in the air is dissolved by the moisture inside the alveolar wall. The oxygen then diffuses into the red blood cells where it combines with haemoglobin. Carbon dioxide diffuses from the blood in the alveoli air space.
How are alveoli adapted for the diffusion of gases
-millions of alveoli with a large surface area of each alveolus
-Thin layers (single epithelial cell thick) short diffusion pathway between the air in the alveolus and blood in capillaries
-Good blood supply supplies constant flow of blood (brings carbon dioxide and carries of oxygen- steep concentration gradient)
-Good ventilation breathing helps maintain the steep diffusion gradient for oxgen and carbon dixoide between the blood and air in the lungs (steep concentration gradient of oxygen and carbon dioxide)
Lung surfactant makes it possible for the alveoli to remain inflated. Through reducing surface tension at the air-water interface of the alveoli
The function of elastic fibres is to stetch (prevent bursting) and recoil back into its original position.This helps exhalation.
Explain the structure of the nasal cavity
- large surface area with good blood supply, warm air to body temp
-hairy lining (ciliated epithelium cells) waft mucus to the mouth where it is then swallowed into the stomach
The goblets secretes mucus to trap dust/ bacetria. This protects the lung tissue from irritation/infection
Moist surfaces, which increases the humidity of incoming air, this reduces evaporation from exchange surfaces
Explain the pleural membrane
A membrane which surrounds the lungs, between these membranes are pleural fluid which acts as a lubricant as the lung volume changes.
Explain the function of the bronchioles
Transports air into small sacs called alveoli within your lung
How is the insect gas exchange system evolved to transport gases compared to mammals and fish
Gases are able to diffuse directly to and from body cells. However, in fish and humans, gases dissolve in blood, which acts as a transport system.
What is the role of Red blood cells (erythrocytes) in the gas exchange system
The blood acts as a transport medium transferring dissolved gases between the cells and the gas exchange system.
Blood transfers essential molecules such as glucose and amino acids.
Explain mass transport
When molecules are carried in a transport medium such as blood through a circulatory system
Explain the circulatory system in fish
Deoxygenated blood is pumped by the heart through the blood vessels to the gills
In the gills, the blood passes through narrow blood vessels called capillaries. Then oxygen diffuses from the water into the blood.
The oxygenated blood now passes from the gills through the blood vessel to the body tissue . The blood passes through narrow capillaries in the body tissue where oxygen diffuses from the blood to the cell that need it
The deoxygenated blood now returns in blood vessels back to the heart. (This is called a single circulatory system as blood is passes through the heart once)
Explain the drawbacks within the single circulatory system of fish
When the blood leaves the heart, the pressure of the blood is high and the blood is moving rapidly. However, the blood then passes through two sets of narrow capillaries (in the gills and body tissues)
When the blood passes through capillaries, the blood slows down and loses pressure. Therefore, the blood is moving relatively slowly. This limits how rapid oxygen can be delivered to body cells
Explain the circulatory system in mammals
Deoxygenated blood is pumped under high pressure from the heart to the lungs
In the lungs, the blood passes through narrow capillaries and oxygen diffuses from the air into the blood
The blood has passed through the capillaries it is now moving relatively slowly with lower pressure.
However, the oxygenated blood returns back to the heart which pumps the blood high pressure around the body. As it passes through the body tissues, the blood passes through capillaries and oxygen diffuses to the body cells.
The low pressure deoxygenated blood makes it way back to the heart to be pumped gain. This is a double circulatory system (blood is passed through the heart twice )
Explain the difference between a single and double circulatory system
Why is the double circulatory system more efficient
In a double circulatory system blood is passed through the heart twice whereas in a single circulatory system blood is passes through the heart once
Blood is passed through the heart twice in a double circulatory system therefore this ensures that blood moves to the body tissues rapidly and under high pressure. Therefore, delivers oxygen more efficiently
Explain what is meant by a closed circulatory system
In fish and mammals the blood is always contained in blood vessels as it travels to and from the heart.
The blood can move relatively rapidly and the amount of blood passing to different organs can be controlled by constricting or dilating blood vessels
Explain what is meant by an open circulatory system
Insects have an open circulatory system. They contain a fluid called haemolymph. This carries nutrients such as sugars but it does not carry oxygen. The haemolymph is passed out of the heart and passes directly into the body cavity called the haemocoel.
The molecules are then transferred between the haemolymph and body cells. The haemolymph then make its way back to the heart.
Key idea behind haemolymph
Haemolymph is not carried in blood vessel (this is an example of an open circulatory system ) The haemolymph is not carried in vessels, therefore it cannot move rapidly around the insect
The insect cannot change the amount of haemolymph moving throughout its body
Explain the process of gas exchange in the human circulatory system
The blood travels from the heart to the lungs in the pulmonary artery. The pulmonary artery is the only artery which carries deoxygenated blood. (Blood in arteries move under high pressure which increases every time the heart contacts {pulse})
Oxygenated blood travels from the heart to the body in a very large artery called the aorta. The aorta divides and these arteries carry oxygenated blood to different organs
The kidneys are suppled by the renal arteries through arterioles. Other organs are also supplied by their own arteries and arterioles,
Once the oxygenated blood reaches the organs it passes through very narrow blood vessels called capillaries (site of gas exchange- oxygen diffuses from blood to body cells and carbon dioxide moves from body cells to the blood)
Once the blood passes through the capillaries, the blood pressure is much lower and the blood is no longer surging in pulses. The blood passes into larger blood vessels called venules and then into veins
Veins carry deoxygenated blood away from the organ to the heart. The veins from the kidneys are called the renal veins.
There is low pressure in the veins and the blood is not surging in pulses.
All the veins in the body organ connect into one very large vein called the vena cava.This returns the deoxygenated blood into the heart
Key idea of the human circulatory system
The heart is shown as your facing the person
The blood leave the in arteries (high pressure). The pressure increase every time the heart contract (pulse). However, blood continually moves forward between contractions.
Veins and arteries are named after the organ they come from and lead to
Explain the structure of arteries
Arteries have a diameter of 4-10mm
The artery wall is relatively thick and able to withstand the high pressure of the blood
The outer layer of the artery is rich in fibrous protein collagen (collagen plays a structural role strengthening the artery wall against the blood pressure)
Next there is a layer containing smooth muscle. when the smooth muscle contracts, the diameter of the artery narrows. This allows the body to control blood flow. (Small arteries will have a higher proportion of smooth muscle than larger arteries as it has a greater role in blood flow)
Next there is a layer rich in elastic fibers. This contains the protein elastin which can stretch.During contraction , a surge a blood is passes down the artery. As the surge moves through the elastic fibers stretch and recoil once the surge has passed. (Elastic recoil helps to keep the blood moving smoothly forward in between contractions)
The central cavity of the artery (lumen) is where the blood flows through, The lumen is lined with a thin layer of endothelial cells. This creates a smooth surface to reduce friction as the blood flows through.
Explain the structure of arterioles
The diameter is 50micrometres
The wall of the arterioles are the same as arteries. However, they differ in relative thickness
The pressure in arterioles and pulse is weaker thus the collagen-rich outer layer and the elastic layer are relatively thin compared to arteries. However, the smooth muscle layer is relatively thicker in arterioles compared to arteries.
What is the function of arteries
Oxygenated blood is carried from the heart to organs through arteries
Explain the function of arterioles
Deliver blood to the capillaries
Arterioles have a relatively thicker layer of smooth muscle compared to arteries Because they are involved in controlling the amount of blood passing through the capillaries. When the smooth muscle in arterioles contracts it reduces blood flow in capillaries this is called vasoconstriction
When smooth muscles in arterioles relaxes blood flow increases through the capillaries- vasodilation (takes place when a organ requires an increased amount of oxygen)
Compare arteries and arterioles
Blood pressure is lower and the effect of the pulse is weaker in arterioles compared to arteries
The collagen rich outer layer and the elastic layer are relatively thin in arterioles compared to arteries
The elastic layer is relatively thicker in arterioles compared to arteries.
The diameter of the artery is larger compared to the diameter of arterioles
Where are capillaries found
Capillaries are extensively branched in every tissue and organ and no body cell is very far from a capillary.
Explain a capillary bed
A network of capillaries where substances are exchanged between the blood and the body cells. (Oxygen and glucose diffuse from blood to the body cells while waste products such as carbon dioxide diffuse from the cells back to the blood)
Explain the adaptations of capillaries
It is extensively branched to provide a massive surface area for exchange of materials
Capillaries have an extremely thin wall (single layer of endothelial cells). On the outside is a thin basement membrane. There is a very short diffusion distance between the blood and the cells near the capillary. (Short distances increase the rate of diffusion of molecules between blood and cells)
The diameter of a capillary lumen is slightly greater than the diameter of a red blood cell. This means when RBC pass through capillaries they are pressed against the capillary wall. Therefore, this reduces the distance for the diffusion for the diffusion of oxygen from the RBC and tissue cells.
As the lumen of capillaries are only slightly larger than a RBC, the RBC travel in a single file line. Therefore, the RBC move through the capillaries more slowly than in arteries and arterioles. This relatively slow movement increases the time available for molecules to diffuse in and out the red blood cell
On the capillary wall there are small gaps between the endothelial cells. These gaps allow fluid to pass out of the blood. (Tissue fluid).- this fluid bathes the cells and provides essential molecules such as glucose and amino acids.
The gaps in the capillary wall also allow white blood cells to leave the bloodstream.
Explain the adaptions of veins
Veins have a thinner wall compared to arteries as the walls of veins do not have to withstand the high blood pressure.
Veins have a larger lumen compared to arteries as it carries a greater volume of blood compared to arteries.
The smooth muscle layer and the elastic layer are also thinner in veins compared to arteries.
The lumen of veins has an internal lining of endothelial cells. This smooth surface reduces friction between the blood and the wall of the vein
Veins contains valve which help to keep moving blood forward. (The blood in veins are traveling slowly under low pressure). If the blood moves forward, then the valves remain open. However, if it moves backwards then the valves shut (prevent back flow of blood0
Veins are found between skeletal muscles. When these muscles contact it squeezes the veins lying between them. This forces the blood along the vein.
When we inhale, the pressure of our chest cavity decreases. The decrease in pressure helps the blood in the chest veins to move towards the heart
Key ideas in veins
The blood in veins do not travel in pulses so there is no elastic recoil
What is found in blood
Consist of two mains part:
Cells- Red blood cells, white blood cells, platelets
Blood plasma- glucose, amino acids mineral ion, dissolve oxygen, plasma proteins
Describe the function of tissue fluid
Blood is carried from the heart to the body tissue in arteries. In the body tissues, the blood passes through narrow, thin-walled blood vessels called capillaries before returning to the heart in veins.
In capillaries fluid passes out of the blood and bathes the tissue cells (this is tissue fluid)
Tissue fluid leaves the blood at the part of the capillary which is near the artery. Tissue fluid transfer molecules such as oxygen and glucose to the tissue cells
Waste molecules from the tissue cells such as carbon dioxide pass into the tissue fluid. The tissue fluid returns back to the bloodstream at parts of the capillary which are near the vein.
Describe how tissue fluid is formed
At the arterial end of the capillary, the blood has just passed though an artery and an arteriole. Therefore, the blood at the arterial end of the capillary is still under relatively high pressure (hydrostatic pressure). This high pressure forces fluid out of the blood and into the tissue.
In blood plasma we have plasmas proteins. These proteins are hydrophilic therefore lower the water potential of the blood plasma. this creates a tendency for water to move back into the blood by osmosis (oncotic pressure)
At the arterial end of the capillary the hydrostatic pressure is greater than the oncotic pressure. This means that tissue fluid is forced out of the capillary through the gaps between the endothelial cells. (Ultrafiltration) .Blood cells and plasma proteins are too large to leave therefore they remain in the blood plasma.
At the venous end of the capillary, the hydrostatic pressure is much lower. That’s because a large amount of water has left the blood. However, the oncotic pressure is still high due to the plasma proteins in the blood plasma. This means at the venous end the hydrostatic pressure is less than the oncotic pressure. This causes water to move back into the blood by osmosis.
Describe the function of lymph fluid
90% of tissue fluid is reabsorbed back into the blood , the remain 10% is drained into a series of blind-ended vessels called lymph capillaries
Lymph capillaries connect into larger lymph vessels, forming the lymphatic system.
Lymph fluid moves along when lymph vessel are squeezed by nearby skeletal muscles. Valves in the lymph vessel help to keep the lymph fluid moving forward. Eventually the lymph fluid returns to the blood stream via the blood vessel under the collar bone. The lymphatic system plays a role in immunity.
Describe the role of erythrocytes in transporting oxygen
Erythrocytes have a biconcave structure which gives them a large surface area to volume ratio.This allows oxygen to diffuse in and out rapidly.
Each erythrocytes contain 300 million molecules of the oxygen carrying protein haemglobin.
Although erythrocytes initially have a nucleus, the nucleus is lost before the erythrocytes enter circulation. The absence of a nucleus means that more of the erythrocytes volume is available to carry haemoglobin.
Describe the structure of a haemoglobin molecule
A globular protein (this means it has a quaternary structure)
Contains 4 globin subunnits , each consisting of a polypeptide (protein) chain and a haem (non-protein) group (2 alpha and beta sub-units)
Each subunit contains a haem group (prosthetic group) which contains a single iron atom Fe^2+. Each haemoglobin molecule can therefore bind with 4 molecules of oxygen, one on each haem group.
Haem group has an affinity for O2
What is the word equation to create oxyhaemoglobin
Hb + 4O2 ⇌ Hb(O2)4
Haemglobin + oxygen ⇌ oxyhemoglobin
What do we call haemoglobin bonded to oxygen
Oxyhaemoglobin
What is an oxygen disassociation curve
A graph which measures the amount of oxygen that combines with haemoglobin
Describe an oxygen disassociation curve
The y-axis records the percentage saturation of haemoglobin with oxygen
The X-axis shows the partial pressure of oxygen
The curve on the graph is a sigmoid curve (S-shaped)
What does the oxygen disassociation curve tell us about haemoglobin
How strongly the oxygen is bound to the haemglobin
Define affinity
How strongly the oxygen is bound to the haemglobin
Explain the oxygen disassociation curve in terms of the structure of haemoglobin
Haemglobin has four polypeptides. Each polypeptide contains a haem group which can bind oxygen.
If there is no oxygen bound, then the haem groups have a low affinity for oxygen molecules. This means that it takes a relatively large partial pressure of oxygen for the first oxygen molecule to bind to a haem group. However, when one oxygen binds the quaternary structure of the haemglobin molecule changes
This now increases the affinity of the haem groups for oxygen. Therefore, binding more oxygen molecules only requires a relatively small increase in the oxygen partial pressure. (Positive cooperatively)
Describe how the partial pressure of oxygen affects haemoglobin saturation in red blood cells as they travel from the alveoli to body tissues, including active tissues.
In alveoli the partial pressure of oxygen is high and the haemglobin in red blood cell is around 97% saturated. However, as red blood cells make their way into the body tissues the partial pressure of oxygen decrease as the tissues are carrying out aerobic respiration. At a certain point, one oxygen molecule now unloads from the haemglobin molecule. This unloading changes the quaternary structure of the haemglobin molecule. This decreases the oxygen affinity of the remaining haem groups.
If the red blood cells move into more active tissue then the oxygen partial pressure will be even lower and two more oxygen molecule will rapidly unload from the haemglobin molecule. For the final oxygen molecule to unload the partial pressure of oxygen has to be very low. This is unlikely to happen under normal conditions but it could take place in very active tissue (muscle tissue during exercise)
Describe the effect of carbon dioxide on the oxygen affinity of haemoglobin (the Bohr effect)
Aerobic respiration produces the gas carbon dioxide. (Carbon dioxide shifts the oxygen disassociation curve to the right). This causes the oxygen affinity of haemoglobin to decrease. This is called the Bohr effect
If the partial pressure of carbon dioxide is low then the haemoglobin is 75% saturated at a partial pressure of oxygen of around 7kPa. However, if the partial pressure of carbon dioxide is high then the haemoglobin is now only 25% saturated at the same partial pressure of oxygen as before. (Carbon dioxide reduces the affinity of haemoglobin for oxygen )
Haemglobin has a higher affinity for oxygen in condition where the partial pressure of carbon dioxide is low e.g in the lungs). In the lung haemoglobin has a higher adding level of oxygen saturation. However, the partial pressure of carbon dioxide will be high in active tissue undergoing aerobic respiration (e.g muscle tissue) because haemoglobin has a lower oxygen affinity it is likely to unload its bound oxygen in these tissues.
How does carbon dioxide in the blood affect haemoglobin’s affinity for oxygen?
In blood carbon dioxide can form the acidic molecule carbonic acid. Carbonic acid released the hydrogen ion H+. The H+ combines with haemoglobin and causes the quaternary structure of the haemoglobin molecule to change. This change in quaternary structure causes the haemoglobin to have a lower affinity for oxygen. (Haemglobin unloads oxygen more easily due to the low affinity)
Describe how oxygen is transferred from maternal blood to fetal blood
In the placenta the fetal blood and the maternal blood pass closely to each other. Although, they do not mix. The maternal blood has a higher level of oxygen compared to the fetal blood. This causes oxygen to diffuse across the placenta and into the fetal blood.
Describe how fetal haemoglobin is adapted for the transfer of oxygen
Haemoglobin has four polypeptide chains. However, in the fetus two of the polypeptide chains are different compared to adult haemoglobin. This is due to differences in gene expression in the fetus compared to the adult. These different polypeptide chains in the fetal haemoglobin mean that it has a high oxygen affinity.
Carbon dioxide from the fetus diffuses into the maternal blood. This carbon dioxide lowers the oxygen affinity of the maternal haemoglobin. Combined with the higher oxygen affinity of the fetal haemoglobin this makes oxygen transfer from the maternal blood to the fetal blood extremely efficient.
Describe how carbon dioxide is transported in the blood
All cells produced carbon dioxide when they carry out aerobic respiration. This carbon dioxide is transported in the blood from actively respiring tissues to teh lungs where it is breathed out:
5% of carbon dioxide is dissolved directly into the blood plasma
20% of carbon dioxide forms a compound with haemoglobin molecules in the red blood cells. (Haemoglobin contains four polypeptide chains. In each of these the first amino acid has a free amino group. Each amino groups reacts with a molecule of carbon dioxide. One molecule of haemoglobin reacts with four molecules of carbon dioxide).
75% is transported as hydrogencarbonate ion in the blood plasma.
What’s is the equation for carbon dioxide
Glucose + oxygen —> carbon dioxide + water
What is the equation for carbaminohaemoglobn
(Respiring tissues)
carbon dioxide + haemoglobin ⇌ carbaminohaemoglobin
(Lungs)
What is the equation to form carbonic anhydrase
(Carbonic anhydrase)
Carbon dioxide + water ⇌ Carbonic acid
How does carbon dioxide interact with haemoglobin in red blood cells, and what happens to this interaction in respiring tissues versus the lungs?
20% of carbon dioxide forms a compound with haemoglobin molecules in the red blood cells. (Haemoglobin contains four polypeptide chains. In each of these the first amino acid has a free amino group. Each amino groups reacts with a molecule of carbon dioxide. One molecule of haemoglobin reacts with four molecules of carbon dioxide).
When the blood passes though respiring tissues the level of carbon dioxide is high and carbaminohaemoglobin forms. However, in the lungs, the level of carbon dixode is low. The carbaminohaemoglobin breaks down, releasing carbon dioxide.
How is 75% of carbon dioxide transported in the blood, and what role do red blood cells, carbonic anhydrase, and haemoglobin play in this process?
Carbon dioxide reacts with water to form carbonic acid. This reaction takes place slowly.However, red blood cells contain an enzyme which speed up this reaction.This is called carbonic anhydrase.
When carbon dioxide diffuses into red blood cells, it rapidly forms carbonic acid. This ensures that the levels of carbon dioxide in the red blood cells are low. Thus a steep concentration gradient for carbon dioxide. This causes a high rate of diffusion of carbon dioxide into the red blood cells.
Once the carbonic acid is formed, it then disassociates or splits forming the hydrogen carbonate ion and the hydrogen ion H+. The hydrogen carbonate ion diffuses out of the red blood cell to the blood plasma. The hydrogen carbonate ion has a negative charge. When the hydrogen carbonate ion diffuses out of the red blood cell this creates a charge imbalance. As the hydrogen carbonate ion diffuses out of the red blood cell a negative chloride ion diffuses into the red blood cell. (Chloride shift).
This prevents a charge imbalance in the red blood cell. When carbonic acid disassociates, it releases the hydrogen ion H+. These hydrogen ion cause the pH of the blood to fall. To prevent this, the haemoglobin in red blood cells bind to the hydrogen ions. Thus the haemglobin acts as a buffer. When haemoglobin binds to hydrogen ions, it forms haemoglobinic acid.
Describe the structure of the human heart
The heart is formed from cardiac muscle and has two separate sides. It consist of four chambers the top 2 chambers are called the atria which have relatively thin and muscular walls. The bottom two chambers are called the ventricles which have a much thicker and muscular wall than atria.
Deoxygenated blood enters the heart from the Vena Cava and travels enters the right atria. The atria is separated from the ventricles by the atrioventricular valves. The left AV valve is called the bicuspid valve and the right AV valve is the tricuspid valve. These valves are attached to tendons which ensure that the valve open in the right direction.
The deoxygenated blood then passes out of the right ventricle to the pulmonary artery ready to travel into the lungs, dividing the two are the semi-lunar valve.
The right and left side of the heart are completely separated from each other by a wall called the septum. The septum prevents any blood from passing directly between the two sides of the heart.
Oxygenated blood returns from the lungs and enters the pulmonary vein and then travels to the left atria. The blood then enters the left ventricle. This is divided by the bicuspid valve. The blood exits through the aorta from the left ventricle. This is divided by the semi-lunar valve
The coronary artery branches directly from the aorta. This supplies the hearty muscle with oxygen and nutrients.
Describe the pattern of blood flow through the human heart
Deoxygenated blood enters the right atrium through the vena cava. The vein cava has two branches. The superior vena cava brings blood from the head and upper parts of the body. whereas, the inferior vena cava brings in blood from the lower parts of the body.
The deoxygenated blood is now pumped from the right atrium to the right ventricle. The right ventricle now pumps the deoxygenated blood out of the heart to the lungs through the pulmonary artery. In the lungs, the blood becomes oxygenated.
Oxygenated blood now returns from the lungs back to the heart in the pulmonary vein. The pulmonary vein brings blood into the left atrium.
The blood then passes into the left ventricle which pumps the blood out of a large blood vessel called the aorta.
The aorta transfers the oxygenated blood to all the parts of the body including the head. (The right and left side of the heart contract at the same time / the left ventricle has a thicker muscular wall than the right ventricle. This is because the left ventricle pumps blood around the whole body whereas the right ventricle only pumps blood into the lungs)
Describe how the action of the heart is initiated and coordinated
During the heart beat, the muscular wall of the heart contact. This contraction forces blood to the lungs and to other organs in the body.
The heart beat is initiated by the heart itself. (The heart does not need an external signal in order to beat. The heart triggers it owns beat therefore is considered myogenic)
In the wall of the right atrium there is a group of specialised cells called the sino-atrial node or SAN otherwise known as the pacemaker. The cells in the sino-atrial node depolarise (become electrically excited). This triggers a wave of excitation to spread across the atria. This causes the atria to contact. This contact is called the atrial systole.
This wave of electrical excitation crossing the atria cannot pass directly down to the ventricles. This is because there ventricle and atria are separated by a layer of non-conducting tissue. This layer of tissue will not pass the electrical excitation through it. However, between the atria there is another group of specialised cells called the atria-ventricular node or AVN
The AVN is connected to conducting fibers called Purkyne fibres. Initially, the Purkyne fibres are bundled together (this is called the Bundle of His). However, this then branches, with the Purkyne fibres running down to the apex or base of the heart then up the walls of the ventricles.
The atrio-ventricular node detects the electrical excitation passing over the atria. After a short delay, the AVN then transmits the electrical excitation down the Purkyne fibres. This electrical excitation causes the ventricles to contract. (The ventricle contracts from the apex upwards to ensure that the maximum volume of blood is pumped out of the ventricles, the slight delay before the AVN triggering an electrical exciaition down the Purkyne fibres is to allow the ventricles to contact after the atria have contacted.
Describe the events taking place in the heart during the cardiac cycle
Both the atria and ventricles are in diastole (relaxed). Blood flows into the atria through the vena cava and pulmonary vein. This causes the pressure in the atria to rise. At a certain point the pressure in the atria is greater than the pressure in the ventricles. This causes the atrioventricular valves to open allowing blood to flow down from the atria into the ventricles.
Now the atria contract (atrial systole takes place). This pushes the remaining blood from the atria into the ventricles.
After a short period of time the ventricles contact (ventricular systole takes place). The pressure in the ventricles now rises rapidly. Because the ventricular pressure is now greater than the atrial pressure the atrioventricular valve closes. This prevents any blood from moving back into the atria from the ventricles.
the semilunar valve in the pulmonary artery and aorta also open. Blood is pumped from the ventricle out of the heart. When the ventricles contract the atria relaxes.
Finally, the ventricles relax (ventricular diastole takes place). The pressure in the ventricles falls below the pressure in the pulmonary artery and the aorta. This causes the semilunar valves to shut. This prevents blood from flowing back into the ventricles. At this point the heart is ready to enter the next cardiac cycle.
What does systole mean
Contacting
What does diastole mean
Relaxing
Describe the pressure and changes during the cardiac cycle
(Both the left and right side of the heart show a similar pattern in pressure and volume changes during the cardiac cycle
The left atrium undergoes systole (contracting). This causes the pressure in the left atrium to increase. The atria-ventricular valve is open, so blood flows down into the left ventricle. This causes the pressure of the left ventricle to increase.
Now the left ventricle contacts (ventricular systole). Pressure in the left ventricle massively increases. Because the pressure in the left ventricle is now greater than in the left atrium the atrioventricular valve shuts.
When the pressure in the left ventricle is greater than in the aorta the semilunar valve in the aorta opens. Blood now flows out of the left ventricle though the aorta. The pressure in the left ventricle now falls as blood is leaving. At a certain point the pressure in the left ventricle is less than in the aorta. Now the semilunar valve in the aorta closes preventing blood being drawn back into the left ventricle. (While the left ventricle contacts the left atrium relaxes- this means that the left atrium is refilling with blood). The left ventricle now relaxes causing pressure in the ventricle to fall. Eventually, the pressure in the left ventricle falls below the pressure in the left atrium.
At this point the atrioventricular valve opens and blood begins to flows into the left ventricle from the left atrium. As the atria and ventricles refill the heart is now ready to enter the next cardiac cycle.
Describe the volume changes during the cardiac cycle
Blood volume increases as it is pumped into the left ventricle when the left atrium contracts. When the left ventricles contracts blood volume falls as blood passes out through the aorta. Finally, the blood volume increases again as the left ventricle relaxes and blood flows down from the left atrium
What can attaching electrode to the surface of the skin achieve
Scientists can analyse the electrical activity of the heart. The resulting trace is called an electrocardiogram or ECG.
What can a patter of an ECG tell us
The first bump (P wave) shows the contraction of the atria (atrial systole)
The abrupt spike (QRS wave) shows contractions of the ventricles (ventricular systole).
Then final bump (T wave) shows relaxation of ventricles (ventricular diastole)
How to calculate a heart beat
Measure the time between the start of one cardiac cycle with the next cardiac cycle.
Then do 60/ the value to give the heart beat in minutes
What is the term given to people with a slow resting heart rate under 60 beats per minute
Bradycardia
What can cause bradycardia to develop
Bradycardia can happen due to athletic training which increases the stroke volume of the heart. As the heart pumps a greater blood volume per beat the number of beats per minuet decreases.
Some people develop bradycardia due to disease. (These people may require an artificial pacemaker)
What is the term given to people with afast resting heart rate greater than 100 per minute
Tachycardia
What can cause tachycardia to develop
Tachycardia can be caused by short-term effects such as fear, panic or exercise.
Longer term tachycardia can be caused by problems with the sinoatrial node or other medical conditions. (In this case surgery or dugs may be required).
Explain an ectopic heartbeat
An extra heartbeat that is not part of the heart’s usual rhythm.
The heart contacts again before the first contraction has finished. This is then followed by a short pause before the normal rhythm continues.
It is relatively common and does not pose any health risk. However if a person experiences frequent ectopic heartbeats then that might indicate a more serious heart condition.
Explain atrial fibrillation
When irregular waves of electrical excitation pass over the atria. This causes the atria to contact randomly and rapidly up to several hundred times a minute.
In most cases, the electrical excitation is not transmitted to the ventricles. The ventricles contract less frequently than the atria. Because the normal rhythm of the heart is disrupted atrial fibrillation is a type of arrhythmia.
During atrial fibrillation, the heart cannot pump blood normally.
Atrial fibrillation is often treated with medication or surgery.
Explain the cardiac output
Volume of blood pumped into the circulatory system in one minute
Explain heart rate
The number of heart beats per minute
In a normal human the heart rate ranges from 60-100 beats per minute. However, during exercise, the heart rate can rise significantly.
Explain stroke volume
The volume of blood pumped out of a ventricle during each contraction
(Normally we consider the left ventricle since this pumps blow around the body. A typical stroke volume is 70cm^3)
How can we call calculate the cardiac output
Cardiac output (cm^/min) = heart rate (beats / min) X stroke volume (cm^3)
We convert the cardiac output from cm^3 / min to dm^3 / min by dividing by one thousand
What is the formula for cardiac output adn the rearranged formulas
Original:
Cardiac output (cm^/min) = heart rate (beats / min) X stroke volume (cm^3)
Rearranged:
Heart rate (beats/ min) = Cardiac output (cm^3 / min) ÷ stroke volume (cm^3)
Stroke volume (cm^3)=. cardiac output (Cm^3 / min) ÷ heart rate (beats / min)
Function of capillaries
Capillaries exchange substances between the blood and body tissues. They are the smallest of the blood vessels.
Site of metabolic exchange.
Structure of venules
Larger than capillaries but smaller than veins.
Venules have thinner walls than arterioles.
They are porous in order to allow fluid and blood to easily move through their walls.
Function of venules
Blood travels from capillaries into venules, which then branches back into the veins ready to lead towards the heart.
Why is the oxygen affinity for the feta haemglobin only slightly greater than adult haemoglobin
Fetal haemoglobin has a higher affinity for oxygen. Thus has a higher affinity of oxygen transfer across the placenta from the maternal haemglobin to the fetal haemoglobin.
The oxygen affinity is only slightly greater as if it was a lot higher than it could prevent it from unloading oxygen in the fetal issues.
