Review Questions

Water and Ion Uptake:

In addition to anchoring the plant, roots perform two other vital functions

1. First they absorb water and salts from the soil.
2. ii. Second, they provide conducting tissues for distributing these substances to the tissues of the stem. Root hairs provide a large surface area for absorption. They grow out into the spaces between soil particles where they are in direct contact with the water. The cytoplasm of the root hairs has a higher concentration of salts than the soil water, so water moves by sis into the root hairs. Salts also enter root hairs by diffusion or active transport. After they enter into the root hairs, water and salts must move through the epidermis and cortex of the root, and then into the xylem tissue in the center of the root

Pathways through which water travels from the outside of the root to the inside:

There are two pathways through which water travels from the outside of the root to the inside

1. The first of these pathways is the apoplast pathway, in which water travels along cell walls and through intercellular spaces to reach the core of the root.
2. the Second route for water is the symplast pathway, in which water moves across the root hair membrane and through the cells themselves, via channels (plasmodesmata) that connect their contents.

Note:

Once in the xylem, the water can be carried to all the aerial parts of the plant.

Transpiration:

Transpiration is the loss of water from the plant surface through evaporation.

Opening and closing of stomata:

Most plants keep their stomata open during the day and close them at night.

Functions of guard cells:

It is the responsibility of the stomata to regulate transpiration via guard cells. The two guard cells of a stoma are attached at their ends. The inner concave sides of guard cells that enclose a stoma are thicker than the outer convex sides. When these guard cells get water and become turgid, their shapes are like two beans and the stoma between them opens. When the guard cells lose water and become flaccid, their inner sides touch each other, and the stoma closes.

The function of Potassium ions in opening and closing of stomata:

Recent studies have revealed that stomata open and close due to the movement of potassium ions in and out of guard cells. According to blue wavelengths of daylight open stomata by allowing K to flow into the guard cells, from the surrounding epidermal cells. Water passively follows these ions into the guard cells, and as their turgidity increases the stoma opens. As the day progresses, guard cells make glucose. Due to a higher concentration of glucose, their water potential decreases and water stays in them. At the end of the day, the K' flows back from guard cells to the epidermal cells, and the concentration of glucose also falls. This initiates the loss of water and reduced turgor pressure in guard cells, which causes the closure of the stoma.

Factors affecting the rate of transpiration:

1. The rate of transpiration is directly controlled by the opening and closing of stomata and it is under the influence of light. In strong light, the rate of transpiration is very high as compared to dim light or no light. Other factors which affect the rate of transpiration are given below.
2. Higher temperature reduces the humidity of the surroundings and also increases the kinetic energy of water molecules. In this way, it increases the rate of transpiration. The rate of transpiration doubles with every rise of 10°C in temperature. But very high temperatures i.e., 40-45°C cause closure of stomata, so that transpiration stops, and the plant does not lose the much-needed water.
3. When air is dry, water vapors diffuse more quickly from the surface of mesophyll cells into leaf air spaces and then from air spaces to outside. This increases the rate of transpiration. In humid air, the rate of the diffusion of water vapors is reduced and the rate of transpiration is low.
4. Wind (air in motion) carries the evaporated water from leaves, and it causes an increase in the rate of evaporation from the surfaces of mesophyll. When air is still, the rate of transpiration is reduced.
5. The rate of transpiration also depends upon the surface area of the leaf. More surface area provides more stomata and there is more transpiration.

Significance of Transpiration:

Transpiration is called a necessary evil. It means that transpiration is a potentially harmful process but is unavoidable too.

1. Transpiration may be a harmful process in the sense that it There is strong and requires wet surfaces from which evaporation can occur evidence that even during the conditions of drought loss of water from the plant mild water stress results in wilting, serious desiccation, and often the death of the plant, results in reduced This is the reason that at high temperatures, plants close their growth rate, stomata and reduce transpiration rate to prevent wilting.
2. On the other hand, transpiration is necessary too. It creates a pulling force called transpirational pull which is principally responsible for the conduction of water and salts from roots to the aerial parts of the plant body. When water transpires from the surfaces of the plant, it leaves a cooling effect on the plant. This is especially important in warmer environments. Moreover, the wet surfaces of leave cells allow gaseous exchange.

Note:

There is strong evidence that even mild water stress results in a reduced growth rate.

Transportation of water in terms of transpirational pull:

Cohesion-tension Theory:

1. According to this theory the mechanism by which water (along with dissolved materials) is carried upward through the xylem is transpirational pull.
2. Transpiration creates a pressure difference that pulls water and salts up from their roots.

Mechanism of transpiration pull:

When a leaf transpires (loses water), the water potential of its mesophyll cells drops. This drop causes water to move by osmosis from the xylem cells of the leaf into the mesophyll cells. When one water molecule moves up by the xylem of the leaf, it creates a pulling force that continues to the root. This pulling force created by the transpiration of water is called transpirational pull. It also causes water to move transversely (from root epidermis to cortex and pericycle).

Reasons for the creation of transpirational pull:

Following are the reasons for the creation of transpirational pull.

1. Water is held in a tube (xylem) that has a small diameter.
2. Water molecules adhere to the walls of the xylem tube (adhesion).
3. Water molecules cohere to each other (cohesion) and do not contain dissolved gases (which would otherwise come out of water and form bubbles).

Note:

These attractions allow an overall tension among water molecules and form 'columns' of water. The columns of water move from root to shoot and the water content of the soil supplies water to the ‘columns.

Transportation of Food:

Phloem is responsible for transporting food substances throughout the plant. The glucose formed during photosynthesis in mesophyll cells is used in respiration and the excess of it is converted into sucrose. In most plants, the food is transported in the form of sucrose.

Pressure flow mechanism:

The currently accepted hypothesis states that the transport of food is through the pressure-flow mechanism. In the pressure-flow mechanism, the food is moved from sources to sinks.

Source:

The sources include any exporting organs typically a mature leaf or storage organ.

Sinks:

Sinks are the areas of active metabolism or storage, for example, roots, tubers, developing fruits and leaves, and the growing regions. A storage organ is capable of storing food and exporting stored materials. For example, the root of beet is a sink in the first growing season, but becomes a source in the next growing season, when sugars are utilized in the growth of new shoots.

Mechanism of Source:

At the source, the food (sugars) is moved by active transport into the sieve tubes of the smallest veins. Due to the presence of sugar in sieve tubes, their solute concentration increases, and water enters them from the xylem via osmosis. This results in higher pressure in these tubes, which drives the solution towards the sink.

Mechanism of Sink:

At the sink end, the food is unloaded by active transport. Water also exits from the sieve tubes. The exit of water decreases the pressure in sieve tubes, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. In other words, the mass flow is caused by drops in pressure at the sink as the food and water molecules are removed.

Blood transfusions in the ABO blood group system:

Blood transfusion is the process of transferring blood or blood-based products from one person into the circulatory system of another.

Requirement of Blood transfusions:

Blood transfusions can be life-saving in some situations, such as massive blood loss due to injury, or can be used to replace blood lost during surgery. People suffering from anemia, hemophilia, thalassemia, or sickle-cell disease may require frequent blood transfusions.

Cross Matching for Blood transfusions:

Transfusion of blood is done after confirming that no agglutination results in the blood of the recipient.

Agglutination:

Agglutination leads to the clumping of cells and clumped cells cannot pass through capillaries. For the confirmation of no agglutination, blood samples of donor and recipient are crossed-matched for compatibility. Antibodies of the recipient's blood may destroy the corresponding antigen-containing RBCes of the donor or the antibodies of the donor's blood may destroy the antigen-containing RBCes of the recipient.

ABO Blood Group System:

It is the most important blood group system in humans. It was discovered by the Austrian scientist Karl Landsteiner, who found four different blood groups (blood types) in 1900. He was awarded the Nobel Prize in Medicine for his work.

Classification of ABO Blood Group System:

In this system, four different blood groups are distinct from each other based on specific antigens (antigen A and B) present on the surface of RBCs.

• Group A:

A person having antigen A has blood group A.

• Group B:

A person having antigen B has blood group B.

• Group AB:

A person having both antigens has the blood group AB.

• Group O:

A person having none of the A and B antigens has blood group O.

Rh Blood Group System (+ve & -ve blood group system):

In the 1930s, Karl Landsteiner discovered the Rh-blood group system. In this system, there are two blood groups i.e., Rh⁺ and Rh^- which are distinct from each other based on antigens called Rh factors (first discovered in Rhesus monkey), present on the surface of RBCs.

• Rh-positive:

A person having Rh factors has blood group Rh-positive.

• Rh-negative:

A person not having Rh factors has blood group Rh-negative.

Note:

Unlike the naturally occurring anti-A & anti-B antibodies of the ABO system, an Rh-negative person does not produce anti-Rh antibodies unless he or she is exposed to Rh-factor.

After birth, two types of antibodies i.e., anti-A & anti- antibodies appear in the blood of individuals. These antibodies are present according to the absence of the corresponding antigen, in persons with blood group A, antigen A is present and antigen B is absent. So, their blood serum will contain anti-B antibodies. In persons with blood group B, antigen B is present and antigen A is absent. So, their blood serum will contain an anti-A antibody. In persons with blood group AB, antigens A & B are present i.e., neither is absent. So, their blood serum will contain no antibody. In persons with blood group O, neither antigen A nor antigen B is present i.e., both are absent. So, their blood serum will contain both anti-A& anti-B, antibodies.

Leukemia (blood cancer):

We know that cancer means the uncontrolled production of cells.

Signs and Symptoms of Leukemia (blood cancer):

Leukemia is characterized by the appearance of a great number of immature and abnormal white blood cells in the bone marrow and often in the spleen and liver.

Causes of Leukemia (blood cancer):

This is caused by a cancerous mutation in bone marrow cells or the lymph tissue cells and results in the uncontrolled production of white blood cells (leukocytes). The mutated bone marrow cells may spread throughout the body, so that white blood cells are produced in many other organs. These white blood cells are not completely differentiated and so are defective.

Types of Leukemia (blood cancer):

This disease may be of different kinds depending on the type of white blood cells, which are being produced at a faster than normal rate. There may be Neutrophilic leukemia, Eosinophilic leukemia, Basophilic leukemia, Monocytic leukemia, or Lymphocytic leukemia.

Treatment of Leukemia (blood cancer):

It is a very serious disorder, and the patient needs to change the blood regularly with the normal blood, got from donors. It can be cured by bone marrow transplant, which is in most cases effective, very expensive treatment.

Thalassemia (g. thalassa = sea; haem = blood):

It is also called Cooley's anemia by the name of Thomas B. Cooley, an American pediatrician (the physician who treats children).

Causes of Thalassemia:

It is a genetic problem due to mutations in the gene of hemoglobin.

Signs and Symptoms of Thalassemia:

The hemoglobin molecule in most cases of thalassemia does not have ß-chains in it. instead, F-chain is present (F: fetal hemoglobin). This is called ß-thalassemia and the patient cannot transport oxygen properly.

Treatment of Thalassemia:

The blood of these patients is to be replaced regularly, with normal blood. It can be cured by bone marrow transplant which is very expensive and does not give a 100% cure rate.

chambers in the human heart: The human heart consists of four chambers.

Left and right atria: The upper thin-walled chambers are called the left and right atria (singular 'atrium').

Left and right ventricles:

The lower thick-walled chambers are called the left and right ventricles. The left ventricle is the largest and strongest chamber in the heart.

Blood flow through the chambers:

The human heart works as a double pump i.e., it receives deoxygenated (with less oxygen) blood from the body and pumps it to the lungs and, at the same time, it receives oxygenated (with more oxygen) blood from the lungs and pumps it to all the body. Inside heart chambers, the deoxygenated and oxygenated blood are kept separated. Here is a brief description of the circulation of blood inside the heart to show its double-pump mechanism.

Function of the right atrium:

The right atrium receives deoxygenated blood from the body via the main veins i.e., superior and inferior vena cava. When the right atrium contracts it passes the deoxygenated blood to the right ventricle.

The opening between the right atrium and the right ventricle is guarded by a valve known as the Tricuspid valve

Tricuspid valve:

Tricuspid valve (because it has 3 flaps). When the right ventricle contracts, the blood is passed to the pulmonary trunk, which carries blood to the lungs. The tricuspid valve prevents the backflow of blood from the right ventricle to the right atrium.

Semilunar valve:

At the base of the pulmonary trunk, the pulmonary semilunar valve is present which prevents the backflow of blood from the pulmonary trunk to the right ventricle.

The function of the left atrium:

The oxygenated blood from the lungs is brought by pulmonary veins to the left atrium. The left atrium contracts and pumps this blood to the left ventricle.

Bicuspid valve:

The opening between the left atrium and the left ventricle is guarded by a valve known as a bicuspid valve (because it has two flaps). When the left ventricle contracts, it pumps the oxygenated blood into the aorta, which carries the blood to all parts of the body (except the lungs). The bicuspid valve prevents the backflow of blood from the left ventricle to the left atrium. At the base of the aorta, the aortic semilunar valve is present which prevents the backflow of blood from the aorta to the left ventricle.

Collection of deoxygenated blood:

We see the right side of the heart collects the deoxygenated blood from the body and distributes it to the lungs.

Collection of oxygenated blood:

while the left side collects the oxygenated blood from the lungs and distributes it to the body.

Pulmonary circulation or circuit:

The pathway on which deoxygenated blood is carried from the heart to the lungs and in return oxygenated blood is carried from the lungs to the heart is called pulmonary circulation or circuit.

Systemic circulation or circuit:

Similarly, the pathway on which oxygenated blood is carried from the heart to the body tissues and in return deoxygenated blood is carried from the body tissues to the heart is called systemic circulation or circuit.

The function of Arteries:

Arteries are the blood vessels that carry blood away from the heart. In adults, all arteries except the pulmonary arteries, carry oxygenated blood.

 Structure of an artery:

Their structure shows that arteries are well adapted to their function Layers of an artery: The walls of an artery are composed of three layers.

1. Tunica externa:

The outermost layer is known as the tunica externa and it is composed of connective tissue.

2. Tunica media:

The middle layer is the tunica media and is made up of smooth muscles and elastic tissue.

3. Tunica intima:

The innermost layer is the tunica intima and is made up of mainly endothelial cells

The function of Lumen:

The hollow internal cavity in which the blood flows is called the lumen.

Arterioles:

When arteries enter body organs, they divide into smaller vessels known as arterioles. The arterioles enter tissues and divide into capillaries.

The function of Capillaries:

Capillaries are the smallest blood vessels, which are formed by the divisions of arterioles. The exchange of materials between blood and tissue fluid is carried out through the capillaries.

Structure of Capillaries:

The walls of capillaries are composed of only a single layer of cells, the endothelium. This layer is so thin that molecules such as oxygen, water, and lipids can pass through them and enter the tissue fluid. Waste products such as carbon dioxide and urea can diffuse from tissue fluid into the blood.

Note:

Capillaries are so small that the red blood cells need to partially fold into bullet-like shapes to pass through them in a single file.

The function of Veins:

A vein is a blood vessel that carries blood toward the heart. In adults, all veins except the pulmonary veins, carry deoxygenated blood. Veins are also well adapted to their function.

Structure of Veins:

The walls of the vein are composed of the same three layers as are present in the artery wall. The tunica externa and the tunica intima have the same composition, but the tunica media of a vein is comparatively thin as compared to that of an artery. It has fewer smooth muscles and elastic tissue. The lumen of the veins is broader than that of arteries.

The function of Valves:

In a tissue, capillaries join to form small venules, which join to form veins. Most veins have flaps called valves that prevent the backflow of blood.

The diagram below shows the origins, locations, and target areas of the main arteries in the human blood circulatory system.

Difference between Atherosclerosis and arteriosclerosis:

Atherosclerosis:

Atherosclerosis is a disease affecting arteries. It is commonly referred to as a "narrowing" of the arteries. It is a chronic disease in which there is an accumulation of fatty materials, abnormal amounts of smooth muscles, cholesterol, or fibrin in the arteries. When this condition is severe, the arteries can no longer expand and contract properly, and the blood moves through them with difficulty. The accumulation of cholesterol is the prime contributor to atherosclerosis. It results in the formation of multiple deposits called plaques within the arteries. Plaques can form blood clots called thrombi within arteries. If a thrombus dislodges and becomes free-floating, it is called an embolus.

Arteriosclerosis:

Arteriosclerosis is a general term describing any hardening of arteries. It occurs when calcium is deposited in the walls of arteries. It can happen when atherosclerosis is severe. 

Myocardial Infarction (heart attack):

It is more commonly known as a heart attack and is a medical condition that occurs when the blood supply to a part of the heart is interrupted and leads to the death of some cells of the heart muscles.

Causes of Myocardial Infarction (heart attack):

A heart attack may be caused by a blood clot in coronary arteries. It is a medical emergency and the leading cause of death for both men and women all over the world. The term myocardial infarction is derived from myocardium (the heart muscle) and infarction (tissue death).

Symptoms of Myocardial Infarction (heart attack):

Severe chest pain is the most common symptom of myocardial infarction and is often described as a sensation of tightness, pressure, or squeezing. Pain radiates most often to the left arm, but may also radiate to the lower jaw, neck, right arm, and back Loss of consciousness and even sudden death can occur in myocardial infarction.

Treatments of Myocardial Infarction (heart attack):

Immediate treatment for suspected acute myocardial infarction includes oxygen supply, aspirin, and a sublingual tablet of glyceryl trinitrate. Most cases of myocardial infarction are treated with angioplasty (mechanical widening of a narrowed or obstructed blood vessel) or bypass surgery (surgery in which arteries or veins from elsewhere in the patient's body are grafted to the coronary arteries to improve the blood supply to heart muscles).

Prevention of Myocardial Infarction (heart attack):

There is therefore increased emphasis on preventing cardiovascular disorders by modifying risk factors, such as healthy eating, exercise, and avoidance of smoking.

A lenticel is an airy aggregation of cells within the structural surfaces of the stems, roots, and other parts of vascular plants. It functions as a pore, providing a medium for the direct exchange of gasses between the internal tissues and atmosphere. 

The main role of potassium is to provide the appropriate ionic environment for metabolic processes in the cytosol, and as such functions as a regulator of various processes including growth regulation Plants require potassium ions (K) for protein synthesis and for the opening and closing of stoma, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid. A deficiency of potassium ions can impair a plant's ability to maintain these processes. Potassium also functions in other physiological processes such as photosynthesis, protein synthesis, activation of some enzymes, phloem solute transport of photoassimilates into source organs, and maintenance of cation: anion balance in the systole and vacuole.

Cohesion-tension theory:

The theory states that the force which carries water (along with dissolved salts) upward through the xylem is the transpirational pull

1. According to this theory the mechanism by which water (along with dissolved materials) is carried upward through the xylem is transpirational pull
2. ii. Transpiration creates a pressure difference that pulls water and salts up from their roots.

Mechanism of Source:

At the source, the food (sugars) is moved by active transport into the sieve tubes of the smallest veins. Due to the presence of sugar in sieve tubes, their solute concentration increases, and water enters them from the xylem via osmosis. This results in higher pressure in those tubes, which drives the solution towards the sink.

Mechanism of Sink:

At the sink end, the food is unloaded by active transport. Water also exits from the Sieve tubes. The exit of water decreases the pressure in Sieve tubes, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. In other words, the mass flow is caused by drops in pressure at the sink as the food and water molecules are removed.

White Blood Cells (Leukocytes):

These blood cells are colorless, as they do not contain pigments. They are not confined to the bloodstream, as they also migrate out into the tissue fluid.

Amount of White Blood Cells:

There are 1 or 2 leukocytes for every 1000 RBCs. One cubic millimeter of blood contains 7000 to 8000 of them. They are much larger (two to three times) than the red blood cells.

The average life span of a white blood cell:

They have a life span of months or even years, but this depends on the body's needs.

Pus is a whitish-yellow, yellow, or yellow-brown exudate produced by vertebrates during inflammatory pyogenic bacterial infections. Pus is produced from the dead and living cells that travel into the intercellular spaces around the affected cells.

The most common agents that induce pus formation are bacteria, such as Staphylococcus aureus. In addition, some chemical agents can cause pus creation.

The pericardial fluid reduces friction within the pericardium by lubricating the epicardial surface allowing the membranes to glide over each other with each heartbeat. 

Systole:

The time at which ventricular contraction occurs is called systole. systole is the contraction of the chambers of the heart, driving blood out of the chambers. The chamber most often discussed is the left ventricle. However, all four chambers of the heart undergo systole and diastole in a timed fashion so that blood is propelled forward through the cardiovascular system.

Diastole:

Diastole is the period when the heart fills with blood after systole (contraction). Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing. The term diastole originates from the Greek word meaning dilation.