Transport in Animals

Question 1

Describe the need for a transport system, 3 factors that affect this

Answer 1

• all living animal cells need a supply of oxygen and nutrients to grow under survive
• play also need to remove waste products so that these do not build up and become toxic
• very small animals do not need a separate transport system, because all their cells are surrounded by, or very close to, the environment in which they live- diffusion will supply enough oxygen and nutrients to keep the cell alive
• however, a larger animal with a complex anatomy will have more than two layers of cells- the diffusion distance becomes too long, and diffusion alone will be too slow to supply all the requirements
• size, surface area to volume ratio, level of metabolic activity

Question 2

Describe how size affects the needs for a transport system

Answer 2

• the cells insides a large Organism are further from its surface- the diffusion pathway is increased
• the diffusion rate is reduced, and diffusion is too slow to supply all the requirements
• the outer layers of cells use up the supplies, so that less will reach the cells deep inside the body

Question 3

Describe how surface area to volume ratio affects the need for a transport system

Answer 3

• small animals have a large surface area to volume ratio, such as the flatworm
• this means that for each gram of tissue in their body they have a sufficient area of the body surface through which exchange can occur
• however, larger animals have a smaller surface area to volume ratio- means that each gram of tissue has a smaller area of body surface for exchange

Question 4

Describe how level of metabolic activity affects the needs for a transport system

Answer 4

• animals needs energy from food, so that they can move around
• releasing energy from body by aerobic respiration requires oxygen
• if an animal is very active, it cells needs good supplies of nutrients and oxygen to supply the energy for movement
• animals that keep themselves warm, such as mammals, need even more energy

Question 5

What are the features of a good transport system

Answer 5

• a fluid to medium to carry nutrients, oxygen and wastes around the body- the blood
• a pump to create pressure that will push the fluids around the body- the heart
• exchange services that enable substances to enter the bloods on leave it again where they are needed- the capillaries
• an effective transport system will also include tubes or vessels to carry the blood by mass flow, and two circuits- one to pick up oxygen and another to deliver oxygen to the tissues

Question 6

Single circulatory systems- what they are, examples, describe

Answer 6

• fish
• the blood flows through the heart once for each Circuit of the body
• heart- gills- body- heart

Question 7

Double circulatory systems- what they are, examples, describe

Answer 7

• mammals
• two separate circuits- one circuit carries blood to the lungs to pick up oxygen- pulmonary circulation
• the other circuits carries the oxygen and nutrients around the body to the tissues- systemic circulation
• blood flows through the heart twice for each Circuit of the body
• heart- body- heart- lungs- heart

Question 8

Advantages of a double circulation- compare fish and mammals

Answer 8

An efficient circulatory system will deliver oxygen and nutrients quickly to parts of the body where they are needed- blood can be made to flow more quickly by increasing the blood pressure created by the heart.

In the single circulatory system of fish:

• the blood pressure drops as blood passes through the tiny capillaries of the gills
• blood has a low pressure as it flows towards the body, and will not flow very quickly
• the rate at which oxygen and nutrients are delivered to respiring tissues, and carbon dioxide and urea are removed, is limited

fish are not as metabolically active as mammals, as they do not maintain their body temperature. Therefore, they need less energy. Their single circulatory system delivers sufficient oxygen and nutrients for their needs.

In the double circulatory system of mammals:

• the blood pressure must not be too high in the pulmonary circulation, otherwise it may damage the delicate capillarys in the lungs
• the hearts can increase the pressure of blood after it has passed through the lungs, so the blood is under higher pressure as it flows to the body and flows more quickly
• the systemic circulation can carry blood at a higher pressure than the pulmonary circulation

mammals are active animals and maintain their body temperature full stop supplying the energy for it’s acquires energy from foods. The energy is released from foods in the process of respiration. To release a lot of energy, the cells needs a good supply of both nutrients and oxygen, as well as the removal of waste products

Question 9

Describe open circulatory systems

Answer 9

• E.g. insects
• the blood is not always held within blood vessels- the blood fluid circulates through the body cavity, so that the tissues and cells are bathed directly in blood
• An open circulatory system consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel.
• In the haemocoel, the haemolymph directly bathes organs and tissues, enabling the diffusion of substances.
• When the heart relaxes, the haemolymph blood is sucked back in via pores called ostia.
• the heart then pumps the blood towards the heads by peristalsis - at the forward’s end of the heart, nearest the heads, the blood simply pours out into the body cavity
• Haemolymph moves around the haemocoel due to the movement of the organism.
• In some animals, movements of the body may help to circulate blood, and without any movement the blood stops moving, so that the transport of oxygen and nutrients stops- or, in other animals such as insects, there is a muscular pumping organ much like a heart
• this is a long, muscular tube that lies just under the dorsal (upper) surface of the body
• some larger and more active insects, such as locusts, have open ended tubes attached to the heart- these direct the blood towards active parts of the body, such as the leg and wing muscles

Question 10

disadvantages of open circulatory systems

Answer 10

• blood pressure is low and blood flow is slow

- circulation of floods may be affected by body movements or lack of body movements

Question 11

Describe closed circulationary systems

Answer 11

• in larger animals the blood stays entirely inside vessels
• a separate fluid, called tissue fluid, bathes the tissues and cells
• From the heart, blood is pumped through a series of progressively smaller vessels. In the smallest vessels, capillaries, substances diffuse in and out of the blood and into cells.
• Blood then returns to the heart via a series of progressively larger vessels.

Question 12

Advantages of closed circulationary systems over open circulatory systems

Answer 12

• higher pressure, so that blood flows more quickly
• more rapid delivery of oxygen and nutrients
• more rapid removal of carbon dioxide and other wastes
• transport is independent of body movements

Question 13

What do all blood vessels have

Answer 13

An inner layer of lining, made of a single layer of cells, called the endothelium - smooth to reduce friction of flowing bolood

Question 14

Name types of blood vessels

Answer 14

• arteries
• arterioles
• capillaries
• venules
• veins

Question 15

Describe arteries

Answer 15

• carry blood away from the heart
• the blood is at high pressure- thick artery wall to withstand that pressure
• lumen relatively small- maintain high pressure
• inner wall folded- allows lumen to expand as blood flow increases
  Three layers of wall:
• inner layer (tunica intima)- thin layer if elastic tissue which allows the wall to stretch and then recoil to help maintain blood pressure
• middle layer (tunica media)- consists of a thick layer if smooth muscle
• outer layer (tunica adventitia)- relatively thick layer of collagen and elastic tissue- provides strength to withstand the high pressure, and recoil to maintain the pressure

Question 16

Describe arterioles

Answer 16

• small blood vessels that distribute the blood from an artery to the capillaries
• walls contain a layer of smooth muscle
• contraction pf this muscle will constrict the diameter of the arteriole- this increases resistance to flow and reduces the rate of flow of the blood
• constriction of the arteriole walls can be used to divert the flow of blood to regions of the body that are demanding more oxygen

Question 17

Describe capillaries

Answer 17

• very thin walls
• allow exchange of materials between the blood and tissue fluid
• very narrow lumen- diameter about the same as that of a red blood cell (7 um)- the red blood cells may be squeezed against the walls of the capillary as they pass along it- helps transfer of oxygen as it reduces the diffusion path to the tissues. Also increases resistance and reduces rate of flow.
• walls consist of a single layer of flattened endothelial cells- reduces diffusion distance for materials being exchanged
• walls are leaky- allow blood plasma and dissolved substances to leave the blood

Question 18

Describe venules

Answer 18

• blood lows from capillaries to small vessels- venules
• collect the blood from the capillary bed and lead into the veins
• wall consists of thin layers of muscle and elastic tissue outside the endothelium, and a thin outer layer of collagen

Question 19

Describe veins

Answer 19

• carry blood back to he heart
• blood is at a low pressure- walls don’t need to be thick
• lumen relatively large- ease flow of blood
• walls have thinner layer of collagen, smooth muscle and elastic tissue than in artery walls- don’t need to stretch and recoil, not actively constricted to reduce blood flow
• contain valves to help the blood flow back to the heart and to prevent it from flowing in the opposite direction. As the walls are thin, the vein can be flattened by the action of the surrounding skeletal muscle. Contraction of the surrounding skeletal muscle applies pressure ti the blood, forcing the blood to move along in a direction determined by the valves.

Question 20

Blood vessels comparison diagram

Answer 20

Question 21

Describe blood

Answer 21

• fluid held in our blood vessels
• consists of a liquid called plasma, containing many blood cells
• the plasma contains many dissolved substances, including oxygen, carbon dioxide, minerals, glucose, amino acids, hormones and plasma proteins
• the cells include the red blood cells [erythrocytes], various white blood cells [leucocytes] and fragment’s called platelets
• erythrocytes are small which means haemoglobin is very close to the plasma membrane- oxygen is unloaded and loaded very fast in and out of the cell- capillarys only allow one through at a time
• plasma proteins are around half albumins- involved in transporting fatty acids and hormones, help regulate osmotic pressure of the bloods- important in the formation of tissue fluid

Question 22

Describe tissue fluid

Answer 22

• similar to blood plasma, but doesn’t contain most of the cells found in blood, neither does it contain plasma proteins
• formed by plasma leaking from the capillarys- surrounds the cells in the tissue, and supplies them with oxygen and nutrients they require- as blood plasma leaks from the capillary, it carries all the dissolved stubstances into the tissue fluids- this movement is mass flow rather than diffusion- waste products from cell metabolism will be carried back into the capillary as some of the tissue fluids returns to the capillary

Question 23

Describe the formation of tissue fluid

Answer 23

• when an artery reaches the tissues, its branches into smaller arterioles, under then into a network of capillaries- these eventually linked up with manuals to carry blood back to veins- therefore blood flowing into an organ or tissue is contained in the capillaries
• at the arterial end of a capillary, the blood is at a relatively high hydrostatic pressure- this pressure tends to push the blood fluids out of the capillaries through the capillary wall- the fluids can leave through the tiny gaps between cells in the capillary wall
• the fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen- all the red blood cells, platelets, and most of the white blood cells remain in the blood, as do the plasma proteins- these are too large to be pushed out through the gaps in the capillary wall
• this tissue fluid surrounds the body cells, so exchange of gases and nutrients can occur across the plasma membranes- that exchange only occurs by diffusion, facilitated diffusion and active uptake- oxygen and nutrients enter the cells, carbon dioxide and other wastes leave the cells

Question 24

Describe the return of tissue fluid to the blood

Answer 24

• the blood pressure at the Venus ends of the capillary is much lower- allows some of the tissue fluid to return it to the capillary carrying carbon dioxide and other waste substances into the blood
  Not all the tissue fluid re enters the blood:
• some tissue fluid is directed into another tubular system called the lymph system or lymphatic system
• this drains excess tissue fluids out of the tissues and returns it to the blood system in the subclavian vein in the chest
• the fluid in the lymphatic system is called lymph and is similar in composition to the tissue fluid- it will contain more lymphocytes, as these are produced in the lymph nodes- which are swellings found at intervals along the lymphatic system which have an important part to play in the immune response

Question 25

Describe the hydrostatic pressure, oncotic pressure, cells, proteins, and fats of blood plasma

Answer 25

• hydrostatic pressure- high
• oncotic pressure- more negative
• cells- red blood cells, neutrophills, lymphocytes
• proteins- plasma proteins
• fats- transported in lipoproteins

Question 26

Describe the hydrostatic pressure, oncotic pressure, cells, proteins, and fats of tissue fluid

Answer 26

• hydrostatic pressure- low
• oncotic pressure- less negative
• cells- some neutrophills, especially in infected areas
• proteins- few proteins
• fats- few fats

Question 27

Describe the hydrostatic pressure, oncotic pressure, cells, proteins, and fats of lymph

Answer 27

• hydrostatic pressure- low
• oncotic pressure- less pressure
• cells- lymphocytes
• proteins- few proteins
• fats- more fats, especially near digestive system

Question 28

tissue fluid formation diagram

Answer 28

Question 29

Describe how pressures affect the movement of fluids in and out of the capillary

Answer 29

• both the hydrostatic pressure of the blood and tissue fluid, and oncotic pressure of the solutes influence movement
• the hydrostatic pressure of the blood tends to push fluid out into the tissues
• the hydrostatic pressure of the tissue fluid tends to push fluid into the capillaries
• the oncotic pressure of the blood tends to pull water back into the blood- has a negative figure
• the oncotic pressure of the tissue fluid pulls water into the tissue fluid
• the net result of these forces creates a pressure to push fluid out of the capillary at the arterial and and into the capillery at the venule end- net pressure is positive at the arterial and negative at the venous and

Question 30

Movement of fluids pressures diagram

Answer 30

Question 31

Briefly describe both sides of the mammalian heart

Answer 31

• it is a muscular pump- at the right side pumps the deoxygenated blood into the lungs to be oxygenated, the left side pumps oxygenated blood to the rest of the body
• on both sides com at the heart squeezes the bloods, putting it under pressure- this pressure forces the bloods along the arteries and through the circulatory system

Question 32

Describe the external features of the heart

Answer 32

• in humans, the heart lies just off centre towards the left of the chest cavity
• the main part of the heart consists of firm, dark red muscle called cardiac muscle
• there are two main pumping chambers- the ventricles, and above them there are thin walled chambers called Atria- much smaller than ventricles
• coronary arteries lying over the surface of the heart- supply oxygenated blood to the heart muscle- if these become constructed, it can have severe consequences for heart health- reduces the delivery of oxygen and nutrients such as fatty acids and glucose- may cause anigma or a heart attack- myocardial infarction
• at the top of the heart there are a number of tubular blood vessels- these are the veins that carry blood into the Atria and the arteries that carry blood away from the heart

Question 33

Describe the internal features of the mammalian heart including chambers, valves, veins, and arteries

Answer 33

• divided into 4 chambers
• the two upper chambers are Atria- these receive blood from the major veins
• deoxygenated blood from the body flows through the vena cava into the right atrium
• oxygenated blood from the lungs flows through the pulmonary vein into the left atrium
• from the Atria, blood flows down through the atrioventricular valves into the ventricles
• there are tendinous cords attached to the valves- prevent the valves from turning inside out when the ventricle walls contract
• a wall of muscle called the septum separates the ventricles from each other- ensures that the oxygenated blood in the left side of the heart and the deoxygenated blood in the right side are kept separate
• deoxygenated blood leaving the right ventricle flows into the pulmonary artery leading to the lungs, where it is oxygenated
• oxygenated blood leaving the left ventricle flows into the aorta- carries blood to a number of arteries that supply all parts of the body
• at the base of the major arteries, where they exit the heart, are the semilunar valves- prevent blood returning to the heart as the ventricles relax

Question 34

heart diagram

Answer 34

Question 35

Describe blood pressure in the Atria

Answer 35

• the muscle of the Atria walls is very thin
• this is because these chambers do not need to create much pressure
• their function is to receive blood from the veins and push it into the ventricles

Question 36

Describe blood pressure in the right ventricle

Answer 36

• the walls of the right ventricle are thicker than the walls of the Atria
• this enables the right ventricle to pump blood out of the heart
• the right ventricle pumps deoxygenated blood to the lungs
• the lungs are in the chest cavity besides the heart, so blood does not need to travel very far
• also, the alvioli in the lungs are very delicate and could be damaged by very high blood pressure

Question 37

Describe blood pressure in the left ventricle

Answer 37

• the walls of the left ventricle can be two or three times thicker than those of the right ventricle
• the blood from the left ventricle is pumped out through the aorta and needs sufficient pressure to overcome the resistance of the systemic circulation

Question 38

Describe the structure of cardiac muscle

Answer 38

• consists of fibres that branch, producing cross bridges- these help to spread the stimulus around the heart, and also ensure that the muscle can produce a squeezing action rather than a simple reduction in length
• there are numerous mitochondria between the muscle fibrils (myofibrils) to supply energy for contraction
• the muscle cells are separated by interpolated discs- shown on micrograph by thick WAVY blue line- which facilitate synchronised construction
• each cell has a nucleus and is divided into contractile units called sacromeres- marked by the thin blue lines

Question 39

What is the cardiac cycle

Answer 39

• the role of the heart is to create pressure that pushes blood around the blood vessels- at the muscular walls of the four chambers must all contract any coordinated sequence, which allows the heart to fill with blood before pumping it away- this coordinated sequence is the cardiac cycle

Question 40

Stages of the cardiac cycle

Answer 40

• atrial systole
• ventricular systole
• diastole

Question 41

Describe atrial systole

Answer 41

• The muscles of the atria (plural for atrium) contracts
• The pressure inside of the atria increases
• The semi-lunar valves in the vena cava and the pulmonary vein close
• The tricuspid & bicuspid
  atrioventricular valves opens, allowing blood into the ventricles
• Pressure decreases
• This lasts about 0.1 seconds
• the muscle in the walls is thin so only a small increase in pressure is created by this contraction- helps to push blood into the ventricles stretching their walls and ensuring they are full of blood

Question 42

Describe ventricular systole

Answer 42

• The muscles of the ventricles contract
• The pressure inside the ventricles increases
• The tricuspid & bicuspid atrioventricular valves close
• The semi-lunar valves in the aorta and the pulmonary arteries open
• Pressure decreases
• This lasts about 0.3 seconds
• contraction starts at the apex (base) of the heart so that blood is pushed upwards towards the arteries

Question 43

Describe diastole

Answer 43

• Pressure in the ventricles decreases
• The semi-lunar valves in the aorta and the pulmonary arteries close
• All the heart muscles relax
• Blood flows into the atria from the vena cava and pulmonary vein
• Blood pressure remains low inside the atria and ventricles
• elastic recoil causes the chambers to increase in volume allowing blood to flow in from the veins

Question 44

Cardiac cycle diagram

Answer 44

Question 45

Describe the working of atrioventricular valves

Answer 45

• after systole, the ventricular walls relax and recoil
• the pressure in the ventricles rapidly drops below the pressure in the Atria
• blood in the Atria pushes the atrioventricular valves open
• blood entering the heart flows straight through the Atria and into the ventricles
• the pressure in the Atria and ventricles rises slowly as they fill with blood
• the valves remain open while the Atria contract, but close when the Atria begin to relax
• this closure is caused by a swirling action in the blood around the valves when the ventricle is full
• as the ventricles begin to contract- systole- the pressure of the blood in the ventricles rises
• when the pressure rises above that in the Atria, the blood starts to move upwards
• this movement fills the valve pockets and keeps them closed
• the tendinous cords attached to the valves prevent them from turning inside out
• this prevents the blood flowing back into the Atria

Question 46

Describe the working of the semilunar valves

Answer 46

• before ventricular contraction, the pressure in the major arteries is higher than the pressure in the ventricles
• this means that the semilunar valves are closed
• ventricular systole raises the blood pressure in the ventricles very quickly
• once the pressure in the ventricles rises above the pressure in the major arteries, the semi lunar valves are pushed open
• the blood is under very high pressure, so it is forced out of the ventricles in a powerful spurt
• once the ventricle walls have finished contracting, the heart muscles start to relax- diastole
• elastic tissue in the walls of the ventricles recoils
• this stretches the muscle out again and returns the ventricle to its original size
• this causes the pressure in the ventricles to drop quickly
• as it drops below the pressure in the major arteries, the blood starts to flow back towards the ventricles
• the semi lunar valves are pushed closed by the blood collecting in the pockets of the valves
• this prevents blood returning to the ventricles
• the pressure wave created when the left semi lunar valve closes is the pulse that we can easily feel at the wrist or neck

Question 47

Briefly describe what valves do and how they work

Answer 47

• they ensure that blood flows in the correct direction- they are opened and closed by changes in the blood pressure in the various chambers of the heart

Question 48

Pressure changes in heart chambers graph

Answer 48

Question 49

Describe blood flow and pressure changes/regulation in the blood vessels

Answer 49

Blood enters the aorta and pulmonary artery in a rapid spurt, but the tissues require blood to be delivered in an even flow- at the structure of the artery walls play a large part in creating a more even flow:

• the artery walls close to the heart have a lot of elastic tissue
• when blood leaves the heart, these walls stretch
• as blood moves on and out of the aorta, the pressure in the aorta starts to drop
• the elastic recoil of the walls helps to maintain the blood pressure in the aorta
• the further the blood flows along the arteries, the more the pressure drops and the fluctuations become less obvious
• it is important to maintain the pressure gradient between the aorta and the arterioles, as this is what keeps the blood flowing towards the tissues

Question 50

what makes heart muscle unique, what is it described as because of this property

Answer 50

It can initiate its own contraction- myogenic- the muscle will contract and relax rhythmically even if it is not connected to the body

Question 51

Describe the nature of heart contraction, what can happen if this goes wrong

Answer 51

• The muscles from the Atria and the muscles from the ventricles each have their own natural frequency of contraction
• the muscles from the atria tend to contract at a higher frequency than the ventricular muscle- this property of the muscle could cause inefficient pumping if the contractions of the chambers are not synchronised- condition known as fibrillation
• so the heart needs a mechanism that can coordinate the contractions of all four chambers

Question 52

describe the initiation and control of the heartbeat

Answer 52

• at the top of the right atrium, near the point where the vena cava empties blood into the atrium, is the sino-atrial node (SAN)
• this is a small patch of tissue that generates electrical activity- initiates a wave of excitation at regular intervals
• occurs roughly 55 to 80 times a minute in humans
• the SAN is also known as the pacemaker

Question 53

Describe contraction of the Atria

Answer 53

• the wave of excitation quickly spreads over the walls of both Atria
• it travels along the membranes of the muscle tissue
• as the wave of excitation passes, it’s causes the cardiac muscle to contract- this is an atrial systole
• the tissue at the base of the Atria is unable to conduct the wave of excitation, and so it cannot spread directly down to the ventricle walls
• at the top of the interventricular septum separating the two ventricles is another node- the atrioventricular node (AVN)
• the AVN also is the only roots that can conduct the wave of excitation through to the ventricles
• the wave of excitation is delayed in the node- allows time for the Atria to finish contracting and for the blood to flow down into the ventricles before they begin to contract

Question 54

Describe contraction of the ventricles

Answer 54

• after the short delay, the wave of excitation is carried away from the avn and down specialised conducting tissue called the purkyne tissue
• this runs down the interventricular septum
• at the base off the septum, the wave of excitation spreads out over the walls of the ventricles
• as the excitation spreads upwards from the base (apex) of the ventricles, it causes the muscles to contract
• this means that the ventricles contract from the base upwards
• this pushes the blood up towards the major arteries at the top of the heart

Question 55

Control of the heartbeat diagram

Answer 55

Question 56

How do we measure the electrical activity of the heart, describe

Answer 56

• electrocardiograms (ECG)
• involves attaching a number of sensors to the skin
• some of the electrical activity generated by the heart spreads upwards talk through the tissues next to the heart and outwards to the skin- at the sensors on the skin pick up the electrical excitation buy the heart and convert this into a trace

Question 57

Describe/explain the shape of an ECG trace in a normal person

Answer 57

• P wave excitation of the atria
• QRS complex- excication of the ventricles
• T- diastole

Question 58

Abnormal ECG traces

Answer 58

Question 59

Describe transport of oxygen

Answer 59

• transported in the red blood cells- erythrocytes
• these cells contain the protein haemoglobin- when it takes up oxygen, it becomes oxyhemoglobin
• haemoglobin + oxygen- oxyhaemoglobin
• oxygen is absorbed into the blood as it passes the alvioli in the lungs
• oxygen molecules diffusing into the blood plasma enter the red blood cells- here they become associated with the haemoglobin
• this means that the oxygen binds reversibly to the haemoglobin
• this takes the oxygen molecules out of solution and so maintains a steep concentration gradient, allowing more oxygen to enter the blood from the lungs and diffuse into the cells
• the blood carries the oxygen from the lungs back to the hearts, before travelling around the body to supply the tissues
• in the body tissues, cells need oxygen for aerobic respiration- therefore the oxyhemoglobin must be able to release the oxygen- this is called dissociation

Question 60

Describe haemoglobin

Answer 60

• complex protein with four subunits
• each subunit consists of a polypeptide chain and a haem group
• the haem group contains a single iron ion in the form of Fe2+
• this iron ion can attract and hold an oxygen molecule- the haem group is said to have a high affinity for oxygen
• as each haem group can hold one oxygen molecule, each haemoglobin molecule can carry four oxygen molecules
• there are about 280 million molecules of haemoglobin in each red blood cell- so a red blood cell can carry over a billion oxygen molecules

Question 61

What does the ability of haemoglobin to associate with and release oxygen depend on

Answer 61

• the concentration of oxygen in the surrounding tissues- measured by the relative pressure that it contributes to a mixture of gases- called the partial pressure of oxygen or pO2
• it is also called the oxygen tension and is measured in units of pressure- kPa

Question 62

Relationship between concentration of oxygen absorbed and oxygen tension in normal liquid versus haemoglobin

Answer 62

• with a normal liquid, you might expect the concentration of oxygen absorbed in the liquid to be directly proportional to the oxygen tension in the surrounding air- linear graph- straight line
• haemoglobin can associate with oxygen in a way that produces an S shaped curve- the haemoglobin dissociation curve

Question 63

Describe the haemoglobin association curve

Answer 63

• at low oxygen tension, so haemoglobin does not readily associate with oxygen molecules- this is because the haem groups that attract the oxygen are in the centre of the haemoglobin molecule- makes it difficult for the oxygen molecule to reach the haem group and associate with it
• this difficulty in combining with the first oxygen molecule accounts for the low saturation level of haemoglobin at low oxygen tensions
• as the oxygen tension rises, the diffusion gradient into the haemoglobin molecule increases- evenutally one oxygen molecule enters the haemoglobin molecule and associate with one of the haem groups
• this causes a slight change in the shape of the haemoglobin molecule- conformational change
• it allows more oxygen molecules to enter the haemoglobin molecule and associate with the other heme groups relatively easily- accounts for the steepness of the curve as the oxygen tension rises
• ask the haemoglobin approaches 100% saturation, the curve levels of, creating an S shaped curve

Question 64

Describe and explain the differences between foetal and adult haemoglobin

Answer 64

• foetal haemoglobin has a higher affinity for oxygen- therefore the haemoglobin dissociation curve is to the left as it must be able to associate with oxygen in an environment where the oxygen tension is low enough to make adult haemoglobin release oxygen
• in the placenta, where the oxygen tension is low, foetal haemoglobin will absorb oxygen from the surrounding fluid- reduces the oxygen tension even further- as a result, oxygen diffuses from the mothers blood fluid into the placenta- reduces the oxygen tension within the mothers blood, which, in turn, makes the maternal haemoglobin release more oxygen- dissociation

Question 65

Where is carbon dioxide released from, wheer is it transported to

Answer 65

• respiring tissues

- must be removed from these tissues and transported by the blood to the lungs for excretion

Question 66

What are the ways in whichcarbon dioxide is transported

Answer 66

• 5% dissolved directly in blood plasma
• 10% combined directly with haemoglobin to form compound carbaminohaemoglobin
• 85% transported in the form of hrdrogencarbonate ions

Question 67

Describe the formation of hydrogencarbonate ions

Answer 67

• carbon dioxide in the blood plasma diffuses into the red blood cells
• here, it combines with water to form a weak acid- carbonic acid - reaction catalysed by enzyme carbonic anhydrase- CO2 + H2O–> H2CO3
• this carbonic acid dissociates to release hydrogen ions (H+) and Hydrogencarbonate ions- H2CO3–> HCO3- + H+

Question 68

Describe what happens once hydrogencarbonate ions have been formed

Answer 68

• The hydorgencarbonate ions diffuse out of the red blood cells into the plasma
• the charge inside the red blood cell is maintained by the movement of chloride ions (Cl-) from the plasma into the red blood cell
• called the chloride shift

Question 69

What is the issue once hydorgencarbonate ions have diffused out, describe what is done to present it

Answer 69

• the hydrogen ions building up in the red blood cell could cause the contents of the red blood cell to become very acidic
• to prevent this, the hydrogen ions are taken out of solution by associating wit haemoglobin to produce haemoglobinic acid (HHb)
• The haemoglobin is acting as a buffer (compound that maintains constant pH)

Question 70

Formation of hydrogen carbonate ions diagram

Answer 70

Question 71

Describe amounts of O2/CO2 at respiring tissues

Answer 71

• blood entering respiring tissues carries oxygen as oxyhaemoglobin
• the partial pressure of oxygen in the respiring tissues is lower than that in the lungs, as oxygen has been used in respiration
• as a result, the oxyhaemoglobin begins to dissociate and release oxygen t the tissues
• this means the haemoglobin is available to take up the hydrogen ions, forming haemoglobinic acid
• whee
  re the issues are very active there is more carbon dioxide released- has large effect on haemoglobin

Question 72

What is the name of the effect involved with the partial pressures of oxygen/carbon dioxide and haemoglobin

Answer 72

Bohr effect

Question 73

Describe the Bohr effet

Answer 73

• describes the effect that an increasing concentration of carbon dioxide has on the haemoglobin
• carbon dioxide enters the red blood cells forming carbonic acid which dissociates to release hydrogen ions
• these hydrogens affect the pH of the cytoplasm, making it more acidic
• these changes in pH affect the tertiary structure of haemoglobin- increased acidity reduces the affinity of it for oxygen
• The haemoglobin is unable to hold as much oxygen, and oxygen is released from the oxyhaemoglobin to the tissues
• where tissues (such as contracting muscles) are respiring more, there will be more carbon dioxide
• as a result, there will be more hydrogen ions released in the red blood cells
• this makes the oxyhaemoglobin release more oxygen
• When more carbondioxide is present, haemoglobin becomes less saturated with oxygen
• reflected in change in oxygen dissociation curve- shift downwards and to the right- The Bohr shift
• his results in more oxygen being released when more carbon dioxide is produced in respiration- advantageous as this is what muscles need for aerobic respiration to continue

Question 74

Bohr effect

Answer 74