mod 2.3 - transport Flashcards
(121 cards)
1
Q
What does xylem transport?
A
Xylem: transports water and inorganic nutrients (mineral ions) absorbed by the roots from the soil to the aerial (above ground) parts of the plant.
2
Q
What does phloem transport?
A
Phloem: transports organic nutrients (dissolved sugars) produced in the leaves by photosynthesis throughout the plant. Other organic substances, such as amino acids, are also transported in the phloem.
3
Q
How do water and mineral ions get absorbed?
A
Plants absorb water and mineral ions through root hair cells.
4
Q
Why are mineral ions absorbed?
A
Potassium is needed to regulate the opening and closing of the stomata; calcium is needed to build cell walls; magnesium is important in the production of chlorophyll; and nitrogen is necessary for making proteins and aa’s.
5
Q
Why is water absorbed?
A
Water is essential for dissolving and transporting mineral ions through the plant.
6
Q
What is xylem in general?
A
Xylem is the vascular tissue that transports water and mineral ions obtained from the soil throughout the plant. It is mainly composed of xylem vessels and elongated cells called tracheids.
7
Q
How are xylem vessels formed?
A
Mature xylem vessels (or vessel elements) are long, water-filled tubes consisting of elongated cells joined end to end.
As the cells mature, the cell wall is strengthened with lignin (a polymer related to cellulose), making them stronger and more rigid.
The cytoplasm and nucleus in the xylem vessel cells then disintegrate and the cells die, creating hollow lignin tubes.
8
Q
What do mature xylem vessels have?
A
Cylindrical skeletons of dead cells joined end to end to form continuous tubes.
Perforated or complete openings at each end, like a straw, so that fluid can flow directly through them.
Pits (unthickened areas) and perforations in the side walls that allow sideways movement of substances between neighbouring vessels in the vascular bundle.
No nucleus or cytoplasm.
9
Q
How are tracheids formed?
A
Single, large, tapering water-filled cells that form part of the xylem tissue in all vascular plants.
When mature, tracheids lose their nucleus and cytoplasm, leading to cell death, but also creating an open structure for water to flow through.
10
Q
What do mature tracheids have?
A
Cylindrical skeletons of death cells joined to form continuous tubes, like xylem vessels.
Pits and perforations in their lignified cell walls.
No nucleus or cytoplasm.
11
Q
What is the difference between xylem vessels and tracheids?
A
Unlike xylem vessels, tracheids are not connected end to end; their ends overlap and water is transferred horizontally through the adjoining pits.
12
Q
How to roots optimise the absorption?
A
Roots have a branched structure that increases both SA and capacity to absorb water and mineral ions.
13
Q
What are the two possible pathways for movement of water and mineral ions absorbed from the soil via the roots?
A
The extracellular pathway and the cytoplasmic pathway.
14
Q
What is the extracellular pathway?
A
Most water and some mineral ions pass in or between cell walls.
15
Q
What is the cytoplasmic pathway?
A
Most mineral ions and some water pass through the cytoplasm of living root cells.
Involves substances entering a root hair cell by crossing the cell’s membrane, then passing from cell to cell through plasmodesmata, which are strands of cytoplasm that connect one cell with the next.
16
Q
What are the three types of transport that move substances across cell membranes and along the cytoplasmic pathway?
A
Active transport: most dissolved mineral ions are selectively taken (by proteins) into roots by active transport.
Osmosis: the high concentration of ions in the vascular tissues of terrestrial plants creates a very large osmotic concentration gradient.
Diffusion: some mineral ions (potassium and phosphate) enter the roots by diffusion; the uptake of these nutrients depends on the rate of water uptake.
17
Q
What is root pressure?
A
In some plants, the osmotic gradient draws in so much water from the roots that it can travel up to 10 m up the stem; known as root pressure. In some trees like BIRCH MINECRAFT, root pressure causes the rising of sap (water and mineral ions) in spring when the soil is warm and the rainfall is high.
18
Q
What is guttation?
A
In some small plants, root pressure can result in the process of guttation. This is the loss of liquid water, and sometimes other substances from leaves (different to transpiration).
In guttation, water is lost through specialised pores at the ends of leaf veins.
19
Q
What is the Casperian strip?
A
The Casperian strip between the roots and xylem is a waterproof layer of cells that form a barrier.
At this barrier, water travelling through the extracellular pathway is forced into the cytoplasm, therefore regulating the substances entering the xylem.
20
Q
What is translocation?
A
The transport of organic solutes from the leaves to other tissues in the plant is known as translocation. –> phloem
Leaves produce carbohydrates in the form of sugars during photosynthesis and are transported to other parts of the plant where it is needed.
21
Q
What is phloem?
A
Phloem transports organic solutes, such as sugars and aa’s, from the leaves to the stems and roots; where it is used or stored in its cells to produce energy for growth and reproduction.
Plants can store sugar in their cells as starch, which can be used for structural support, or as an energy source when the plant cannot photosynthesise.
Phloem tissue is composed of sieve tubes, companion cells, parenchyma cells and sclerenchyma cells.
22
Q
What are sieve tubes?
A
Mature sieve tubes are living cells with no nucleus and no lignin in the cell walls.
They form linear rows of elongated cells, and their cell walls are thin and perforated at each end by holes or pores → forming sieve plates.
Plasmodesmata pass through the perforations in sieve tubes, acting like straws through which sugars and other materials can move.
Sieve tube cells are connected with one or more companion cells, connected by plasmodesmata; and are able to function without a nucleus with companion cells.
23
Q
What are companion cells?
A
A type of parenchyma cell that provides metabolic support and helps load and unload materials throughout the plant. Like sieve tube cells, companion cells have thin cell walls.
They retain their nuclei and carry out all the metabolic processes required by the sieve tube cells, sharing metabolic products through plasmodesmata; keeping sieve tube cells alive.
24
Q
What are parenchyma cells?
A
Make up the soft tissue of a plant and have many important functions.
In leaves, they contain the chloroplasts and make up the mesophyll. Parenchyma cells that contain chloroplasts are called chlorenchyma cells.
In roots and tubers, they have large vacuoles that store starch, fats, proteins and water. They also provide buoyancy in aquatic plants and play a role in wound repair.
Their structure varies from elongated to spherical.
25
What are sclerenchyma cells?
Provide strength and structural support for the plant.
Mature sclerenchyma cells are dead and have very thick cell walls made of cellulose and lignin.
There are two types: fibres and sclereids.
Fibres are found in stem roots and the vascular tissue of leaves.
Sclereids are found in the outer layer of seeds and the shell of nuts.
The fibres of some plants, such as flax and hemp, have important uses as textiles.
26
What are sources?
Sources: the sites where sugars are produced during photosynthesis. (leaves)
27
What are sinks?
Sinks: the sites where sugars are translocated to. (roots, bulbs, stems, flowers and fruits)
28
Where is glucose produced?
Glucose (monosaccharide) is produced in the chloroplasts of the chlorenchyma cells and converted into sucrose in the cytosol of cells; this sucrose is then pumped into the companion cells and from there, flows into the sieve tube cells.
29
Is translocation an active transport?
Translocation is an active process; involving the flow of cytoplasm in sieve tubes driven by a pressure gradient. This pressure gradient begins in the leaves, where sucrose is actively pumped into phloem sieve tube cells.
30
Why do sieve tube cells have thick and rigid cell walls?
Sieve tube cells have thick and rigid cell walls to withstand hydrostatic pressure, which assists the flow of solutes. Transport in individual sieve tube cells is in one direction only, but bundles of sieve tube cells transport sap in both directions.
31
What happens when water enters sieve cells?
As water enters, it increases the fluid pressure (turgor) in sieve cells, which pushes fluid into the adjacent sieve cells.
While this is happening in the leaves, sucrose is being actively removed from sieve cells in roots, and used for growing shoots and developing fruit; causing an osmotic gradient that draws water out of sieve cells and lowers their turgor pressure.
Fluid pressure is therefore high in sieve tube cells in leaves and low in thos in roots and growing shoots.
Most phloem sap in sieve tubes flows along this fluid pressure gradient from sources to sinks, allowing the phloem to translocate solutes away from the source and towards the sink.
Translocation stops if the cells in the stem die.
32
What is transpiration?
The passive movement of water though the xylem of vascular plants, from the roots to the leaves.
33
Why is transpiration a vital process?
Transpiration is a vital process that enables plants to: absorb the water necessary for photosynthesis, transport mineral salts to leaf cells and fruits, cool down and not become overheated.
34
Who proposed the transpiration-cohesion-tension theory?
Proposed by John Joly and Henry Horatio Dixon in 1894, and is now the most accepted theory that explains the upward movement of water through the xylem of plants.
35
What is the transpiration-cohesion-tension theory?
Theory explains the primary mechanisms of water in plants; cohesion between water molecules, adhesion between water molecules and plant cell walls, and the tension (differential pressure) created when water evaporates from the leaves.
36
Are water molecules cohesive?
Water molecules are very cohesive; they have a strong tendency to stick together.
Cohesion also causes the water molecules evaporating from the surface of a leaf to pull adjacent water molecules with them.
Water in nearby xylem vessels is then drawn up to the leaves to replace the water lost via evaporation; in this way, thousands of lead cells, each drawing water from the xylem, create tension that pulls water up the xylem from the roots.
37
Are water molecules adhesive?
They are also adhesive, meaning they have a tendency to stick to other molecules.
38
How does adhesion and cohesion work together for transpiration
The adhesiveness allows it to stick to the hydrophilic cell walls in the xylem of the plant, and along with cohesion, moves against the force of gravity.
39
What is the transpiration stream?
This continuous one-way flow of water from roots to leaves is called the transpiration stream.
40
What factors affect transpiration rates?
Humidity, temperature and wind.
Also:
The SA across which transpiration takes place is related to the degree of opening of all stomata; this is by far the most important factor affecting the rate of transpiration. The greater the number of stomata and the more open they are, the more SA there is from which water can be lost.
The rate of transpiration is higher during the day than at night because stomata open during the day to exchange gases during photosynthesis, and close at night to minimise water loss.
41
How does humidity affect transpiration rates?
Humidity: rates decrease when there is a lot of water vapour in the air (high humidity). Humidity reduces the water concentration gradient between leaf spaces and air, so fewer molecules evaporate into the air. (potassium ions)
42
How does temperature affect transpiration rates?
Temperature: rates increase as temperature increases, because heat energy increases the rate of evaporation of water.
43
How does wind affect transpiration rates?
Wind: air currents increase the rate, by moving water vapour away from the leaf and increasing the rate of evaporation of water.
44
What are the two transport systems of mammals?
Mammals have two transport systems: the cardiovascular system (circulatory system) and the lymphatic system.
45
What is the cardiovascular system of mammals?
The cardiovascular system is a closed circulatory system. It Highly branched network means no cells are more than 1mm from a capillary, ensures efficient nourishment and waste removal. Specialised circulatory systems with networks of pipes and chambers have evolved to transport vital nutrients to all cells in complex multicellular organisms.
The cardiovascular system delivers oxygen from the lungs to the brain in less than 4 seconds.
46
What is the circulatory fluid of cardiovascular system in mammals?
Blood.
47
What are the two circulation pathways?
Pulmonary circulation and systemic circulation.
48
What is pulmonary circulation?
Pulmonary circulation: transports blood to and from the lungs. Deoxygenated blood is pumped from the heart to the lungs, where it is oxygenated before returning to the heart.
49
What is systemic circulation?
Systemic circulation: transports blood to and from the rest of the body; this system is larger than pulmonary, as the heart must pump blood to all organs in the body. Oxygenated blood is pumped from the heart to the organs, where it gives up its oxygen to the cells before returning to the heart.
50
What are the key components of the mammalian cardiovascular system?
Key components: heart, blood vessels and blood.
51
How many chambers does the human heart have?
The human heart is a four-chambered muscular pump with two pumping chambers (ventricles) and two receiving chambers (atria). It is responsible for moving blood throughout the cardiovascular system. The right side of the heart pumps deoxygenated blood and the left side pumps oxygenated blood.
52
What are blood vessels?
Blood vessels are a network of muscular vessels carrying blood to and from the heart.
53
What are the blood vessels divided into?
Pulmonary vessels: carry blood two and from the lungs.
| Systemic vessels: carry blood to and from all other parts of the body.
54
What are the three types of blood vessels?
Arteries, veins and capillaries.
55
What are arteries?
Carry blood away from heart; they have thick, muscular walls and carry blood under high pressure.
56
What are veins?
Carry blood to the heart. They have thin walls and carry blood under low pressure.
57
What are capillaries?
Connect arteries and veins. They are fine vessels with very thin walls and carry blood under low pressure. The thin walls allow gases and nutrients to pass between the capillaries and tissues.
58
Where and what is the mammalian heart made of?
The mammalian heart is at the centre of the chest, between the lungs, surrounded by the protective rib cage.
It includes the cardiac muscle, connective tissue and nerve tissue.
Connective tissue makes up the valves and nerve tissue controls the heart rate.
A mammalian heart can pump even when separated from the body because it has its own electrical impulses.
59
What are the four chambers of the human heart?
The upper receiving chambers are the atria (singular atrium) and have thinner walls. Each atrium opens into one of the lower, thicker-walled chambers, called ventricles.
Blood moves through the heart in one direction because of the presence of four one-way valves: one between each atrium and the ventricle below, and one between each ventricle and its outgoing artery.
60
What is the blood flow in the heart (in general)?
Both sides of the heart function in a coordinated way: first both atria contract, then both ventricles contract. The right side of the heart pumps deoxygenated blood to the lungs, where it becomes oxygenated. The left side of the heart pumps oxygenated blood from the lungs around the body.
61
What is the right side of the heart responsible for?
Deoxygenated blood, returning from the body, enters the heart through two large veins (the inferior vena cava and the superior vena cava).
The deoxygenated blood flows through the vena cava into the right atrium.
As both heart chambers relax between contractions, the deoxygenated blood flows though a valve into the right ventricle.
The atrium contracts first, pushing more deoxygenated blood into the right ventricle.
As the ventricle contacts, the rising ventricular pressure closes the valve between the atrium and ventricle (atrioventricular valve) and opens the valve between the ventricles and the opening of the pulmonary artery (semilunar valve), pushing blood into the pulmonary artery.
Blood travels through the pulmonary artery to the lungs where it is oxygenated.
62
What is the left side of the heart responsible for?
In the lungs, blood loses carbon dioxide and gains oxygen by diffusion as blood flows though the narrow capillaries around the alveoli.
Oxygenated blood is pumped by the left ventricle to the rest of the body via the aorta.
63
How do the cells of the heart have a rich blood supply?
The cells of the heart have their own rich blood supply via the coronary circulation, consisting of vessels that spread across the surface of the heart and into the heart tissue, including the arteries, arterioles, capillaries, venules and veins.
64
What do the capillaries do?
Connect arteries to veins.
Deliver oxygen, nutrients and other substances to extracellular fluids via diffusion.
Receive carbon dioxide and other wastes.
65
How do red blood cells travel through capillaries?
Capillary has a diameter of 5-10μm, so red blood cells (7-10μm in diameter) pass very close to the capillary wall.
The flattened shape and lack of nucleus of a RBC are believed to improve their transport capability, by increasing the SA availability for exchange.
Their membrane structure makes them very flexible, allowing them to fold and squeeze through small capillaries.
66
How does exchange between blood plasma and extracellular fluid occur?
Exchange between blood plasma and extracellular fluid occurs by diffusion and filtration across capillary walls → ions and small molecules, like glucose and aa’s, diffuse through the capillary wall along concentration gradients.
67
How does filtration occur?
Filtration occurs by two opposite forces: hydrostatic pressure (or blood pressure) and osmotic pressure, which pushes fluid into and out of the capillaries.
Hydrostatic pressure is a result of blood pushing outwards on the capillary walls.
Osmotic pressure results from the differing solute concentrations between the blood and the extracellular fluid.
68
Why is there hydrostatic pressure with blood and capillaries?
Blood, being hypertonic (more concentrated) than the extracellular fluid, water tries to move through the capillary walls into the blood, putting an inward pressure on the capillaries, where there is an overall hydrostatic pressure → more fluid filters out of the capillary than filters in.
This pressure results in a small amount of protein leakage through the capillary wall cells; when blood pressure increases, this leakage is higher and can result in fluid loss to tissues, causing swelling.
Reabsorption allows around 85% of the fluid to return to the capillaries, while the remaining 15% enters the lymphatic system.
69
Where are the capillaries more permeable?
In some tissues, like the gut and liver, the capillaries are more permeable and allow larger molecules to cross → helps the absorption of digested foods from the gut, enabling the liver to take in materials to be broken down.
70
Where are the capillaries least permeable?
The capillary permeability in the brain is very low, therefore substances that enter and exit the brain are controlled.
Nerve tissue is very sensitive to its environment, so it is important that the composition of the extracellular fluid surrounding the brain and spinal cord is carefully regulated.
71
What is mammalian blood made of?
The fluid portion of blood is plasma: pale, yellow liquid containing ions, dissolved gases, proteins, hormones, nutrients and wastes.
The cellular elements of blood include red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes).
72
Why is blood a tissue?
Blood is a tissue because it is made up of many similar cells working together.
73
What are these specialised cells made from?
All produced by cells in the red bone marrow, found in the upper ends of long bones and in flat bones (skull, ribs, pelvis).
74
What are red blood cells?
Make up around 40% of blood in humans, a single drop containing about 5 million red blood cells.
Mature RBC are concave on each side and are highly flexible.
They lack a nucleus, and are full of a red pigment: haemoglobin.
Hemoglobin binds to oxygen and transports it to the cells. (unlike carbon dioxide, oxygen is relatively insoluble)
RBC live for around 120 days; old/damaged ones are removed and broken down by the liver or spleen, where useful substances like iron are reused by the body.
Every second, 2.5 million new RBC enter your bloodstream to replace old ones.
75
What are white blood cells?
Larger than RBC, but fewer in number.
| A drop contains 5000-10000 WBC, held in more reserve in the spleen, kidney, thymus and thyroid gland.
76
What are the main types of white blood cells?
Several types of WBC, but the two most numerous are involved in defence against microorganisms are phagocytes and lymphocytes.
77
What are phagocytes?
Phagocytes: remove debris and fright in infections. They are attracted to a site of infection, where they squeeze through tiny gaps in capillary walls and engulf harmful bacteria and damaged cells.
78
What are lymphocytes?
Lymphocytes: responsible for the production of antibodies and the development of immune responses.
79
What are platelets?
Fragments of cells; smaller than both RBC and WBC.
| Contain substances that are important in preventing blood loss and promoting blood clotting.
80
What is blood pressure caused from?
Caused by the contraction of the ventricles.
The muscular wall of the left ventricle is almost as twice as thick as that of the right ventricle; because the left ventricle must pump blood to all the organs, while the right only pumps blood to the lungs.
Therefore, the right contracts with less force → there is lower blood pressure in the right ventricle and pulmonary arteries than in the left.
81
Why is a pulse felt?
In arteries, blood pressure fluctuates with each heartbeat, producing a pressure wave that is felt as a pulse.
82
How does systolic pressure change?
The higher systolic pressure occurs when the ventricle contacts, and the lower diastolic pressure occurs when it relaxes.
83
What is the marfan syndrome?
Inherited disorder that affects connective tissue (holds and connects tissue together; their cells are held in an extracellular matrix).
It is caused by a defective glycoprotein: fibrillin-1, causing the connective tissue to be weakened, affecting its function and causing a range of malfunctions in tissues and organs throughout the body.
84
What two major problems may happen from weakened connective tissue in the aorta?
Aneurysm: where the aorta stretches and bulges under pressure, slowing blood flow that causes blood clots, strokes or a pulmonary embolism in the lungs. If the aneurysm ruptures, it may lead to death.
The aorta may begin to tear, so blood leaks between the layers of the aorta, causing lack of blood flow and eventual death.
85
What is atherosclerosis?
A type of arteriosclerosis.
With age, arteries lose collagen and elastin filaments, therefore becoming less elastic and hardening; this hardening of the arteries being arteriosclerosis → puts stress on the heart to pump harder.
Atherosclerosis affects the coronary blood vessels that supply blood to the heart muscle; build up of plaque restricts the supply of nutrients and oxygen to the heart tissue.
Everyone eventually develops some degree of arteriosclerosis with age; but those with high levels of cholesterol and triglycerides in the blood increase risks.
Smoking, poor diet, lack of exercise and obesity are also risk factors.
86
What does the lymphatic system transport?
It transports a colourless liquid - lymph - from the tissue to the heart.
87
What are the organs of the lymphatic system?
Open system that contains lymph vessels, nodes and organs (thymus and spleen).
88
What is the function of the lymphatic system?
Return extracellular fluid containing proteins that have leaked out of the capillaries back into the cardiovascular system. Without this, fluid would accumulate in the tissues; once inside this system, the fluid is known as lymph.
89
What is the structure of the lymphatic system?
Fine lymph capillaries join to form increasingly larger vessels, which eventually empty into the large veins near the heart.
Similar structure to cardiovascular system.
90
The characteristics of lymph fluid under different circumstances?
Larger lymphatic vessels contract, but most lymph flow results from the external compression of lymph vessels by muscular activity, such as during movement or breathing.
When compressed, lymph fluid is forced in one direction (one-way valves).
When a person is stationary for a long time, the fluid drainage from tissues decreases causing swelling.
91
How does the lymphatic system factor into the immune system?
Also plays a vital role in the immune system, where invading pathogens are transported in the lymph to the lymph nodes, where bacteria, viruses and cancer cells are trapped and destroyed by phagocytes and lymphocytes → why lymph nodes swell when there is an infection.
92
What is deep vein thrombosis?
Fluid accumulation from being stationary can lead to this condition which is a blood clot that forms in the veins of the leg.
If the clot breaks away and is carried by the bloodstream to a lung, it can lodge here, causing pulmonary embolism (blockage of the main artery of the lungs).
Regular exercise, a healthy diet and not smoking reduce the risk of this.
93
What are open circulatory systems?
Blood is pumped by the heart but is emptied into an open, fluid-filled space, the haemocoel, which lies between the ectoderm and endoderm. Eg: insects; arthropods.
Has a heart-like structure, but no blood vessels.
No distinction between blood and extracellular fluid.
The fluid is called hemolymph and is in direct contact with all cells, kept moving by the heart and the movement of the organism.
94
What are insect circulatory systems? Open or closed?
No circulatory system involved; open circulation.
95
How does gas exchange occur in insect circulatory systems?
Gas exchange directly between the atmosphere and their cells.
Gas exchange takes place across a network of fine internal air-filled tubes called trachea and finer tracheoles; which open to the atmosphere through spiracles that open and close.
Tracheoles branch into smaller and smaller tubes, reaching all tissue.
Oxygen moves into the tissues and carbon dioxide enters the trachea to be removed from the organism.
96
Why is size limited in insects?
This gas exchange is slow, so some larger organisms pump their abdomens to accelerate the movement of these gases.
Grasshoppers also have air sacs that can be pumped to move air through the system.
This type of respiratory system limits the size of insects.
97
What are closed circulatory systems?
A heart is the main propulsive organ, pumping blood and maintaining high blood pressure in arteries.
Animals with closed circulation can increase oxygen delivery to a tissue very rapidly.
Maybe a single circulatory system with a two-chambered heart, or a double circulatory system with a four-chambered heart.
Allows for bursts of energy.
98
What happens in the single circulatory systems of fish?
Blood travels from the heart to the gills, where it absorbs oxygen and releases carbon dioxide. Then it flows from the gils to the organs and tissues in the rest of the body, then back to the heart.
It is a single circulatory system as there is just one circuit from the heart.
Gills are principal organs of the respiratory system.
99
Why do circulatory systems need to be efficient in fish?
Oxygen is not very soluble in water, so the respiratory system needs to be efficient.
100
What are gills composed of?
Gills are composed of several gill arches on either side of the pharynx (throat).
Each gill is composed of rows of filaments, which in turn are composed of lamellae.
101
What are lamelle in gills?
Lamelle are closely packed rows of leaf-like structures in which oxygen diffuses into the blood and carbon dioxide diffuses from the blood into the surrounding water.
102
Where is water drawn in through a fish?
Water is drawn into the pharynx through the mouth and pushed in between the gill arches by compressing the pharynx with the mouth closed; forcing water between individual gill lamellae.
103
Why are gills red?
Have large SA for gas exchange and are visibly red because they contain many blood vessels.
104
Where is water drawn out through a fish?
Water then passes out under the operculum, which covers and protects the fragile gills.
105
What are double circulatory systems?
Found in amphibians, reptiles and mammals, where there are two circuits from the heart.
The first circuit: blood passes from the heart to the lungs, where it absorbs oxygen and releases carbon dioxide, then returns to the heart.
The second circuit: blood passes from the heart to the organs and tissues in the body, then back to the heart.
106
What circulatory systems do birds have?
Double circulatory system.
107
What is the process of circulatory systems in birds?
Bird lungs are similar to mammals, but instead of alveoli, they have a system of microscopic tubules called air capillaries: where oxygen moves into the blood and carbon dioxide moves from the blood into the lungs to be exhaled.
Their lungs are small, and do not have a diaphragm to expand and contact; instead they rely on pressure changes in air sacs to move air in and out of their respiratory system. They have 7-9 air sacs, dependent on the species.
108
What is inhalation in birds?
Inhalation: air is drawn into the posterior air sacs and air from the lungs moves into the anterior air sacs.
109
What is exhalation in birds?
Exhalation: air sacs collapse, which pushes air from the posterior air sacs into the lungs.
Air in the anterior air sacs is expelled via the trachea.
110
Why is the bird's respiratory system the most efficient?
Their process of exhalation creates a one-way flow of fresh air through the bird’s lungs → efficiency.
111
How is oxygen carried?
Efficient supply of oxygen (through ventilation) and removal (by circulation) is needed to maintain an oxygen concentration gradient across the lung surface.
The oxygen carrying molecule haemoglobin increases the oxygen-carrying capacity of the blood → which reduces the amount of energy that must be spent pumping blood.
112
What is haemoglobin?
Haemoglobin is a complex protein containing iron.
It can combine reversibly with oxygen.
Oxygen is insoluble in blood (only 0.2mL of oxygen gas dissolves in 100mL of blood).
The carrying capacity of mammalian blood is increased 100 times by the presence of the red respiratory protein which is carried in RBC.
Mature RBC are little more than cell membranes filled with haemoglobin.
113
How does oxygen concentration affect haemoglobin interactions?
Four oxygen molecules can combine with one of this protein.
In areas of high oxygen concentration (blood vessels in lungs), haemoglobin can combine with oxygen to form oxyhaemoglobin.
In areas of low oxygen concentration (muscles that are exercising) oxygen is released (dissociated) from the oxyhaemoglobin.
Therefore, the percentage of oxygen concentration in exercising muscles, tissues and lungs varies.
114
Oxygen in the tissues:
The oxygen-haemoglobin dissociation curve represents how blood carries and releases oxygen throughout the body.
The percentage of Hb saturated with oxygen indicates how readily Hb binds to oxygen molecules → this binding can be affected by many factors; an increased oxygen affinity shifts the curve to the left and a decreased oxygen affinity shifts the curve to the right.
Resting humans: Hb is almost 100% saturated with oxygen in the lungs, and about 75% saturated in other tissues, meaning one-quarter of the oxygen carried by blood throughout the body is taken up from capillaries and used by cells for cellular respiration.
Remainder of oxygen is a reserve when oxygen demand increases such as in exercise or emergencies.
115
Why are muscles red?
Muscles are red because they contain a form of haemoglobin called myoglobin; which carries a reserve store of oxygen that muscles can use for a limited period if the amount of oxygen in the blood suddenly decreases (in exercise or if a blood vessel is temporarily blocked).
116
Myoglobin?
When the blood supply is restored, the myoglobin oxygen store is refilled from the blood.
Myoglobin has a higher affinity for oxygen than haemoglobin and therefore can take oxygen from it.
Also means that hemoglobin releases large amounts of its bound oxygen to exercising muscle before the myoglobin releases its store, making it a true emergency source.
The haemoglobin of a fetus binds oxygen with greater affinity than an adult, extracting blood from the mother's placenta.
Myoglobin has a stronger affinity for oxygen than does haemoglobin.
117
What anaemia?
A condition where there are insufficient RBC or the quality of the RBC or haemoglobin is low.
Caused from iron deficiencies in the diet, failure to absorb iron, heavy menstruation, or inherited disorders (sickle cell disease).
Results in pale skin, tiredness, muscle weakness, headaches and problems with focus.
Treatment requires change in diet, or oxygen therapy and blood transfusions.
118
How does carbon dioxide get carried?
Must be excreted to prevent a decrease in pH from its binding with water, creating carbonic acids.
In mammals, 7% of the carbon dioxide carried by blood is dissolved in the blood plasma; 23% combines with haemoglobin molecules → carbamino-haemoglobin.
The remainder of carbon dioxide produced in working tissues passes into RBC where it is converted into hydrogen carbonate ions, and then passes out to be transported in the plasma.
When blood reaches the lungs, the hydrogen carbonate moves back into the RBC, where it is converted into carbon dioxide for release during breathing.
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What does the Bohr effect explain?
It explains how haemoglobin picks up and releases oxygen where it is needed in the body.
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Who discovered the Bohr effect?
Discovered in 1904 by Danish scientist Christian Bohr, where he discovered that the affinity of haemoglobin for oxygen is inversely related to the acidity of the blood and the concentration of carbon dioxide.
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Explain the Bohr effect?
As the blood nears the lungs, the concentration of carbon dioxide decreases (decreasing acidity) and the affinity of haemoglobin for oxygen increases → allows haemoglobin to bind to the oxygen entering the blood from the lungs and transport it to cells throughout the body.
The opposite occurs in tissues where oxygen needs to be released/dissociated from haemoglobin. As blood moves away from the lungs, the concentration of carbon dioxide increases (increasing acidity) and the affinity of haemoglobin for oxygen decreases → allows oxygen to be released from the haemoglobin in RBC to cells throughout the body where it is needed for cellular respiration.
