One of the most important parts of plants is the stomata. Stoma is the singular form of stomata and it means ‘mouth’. Stomata function is to regulate the process of photosynthesis, transpiration, respiration, etc. Stomata are found on the leaves of plants. They can either be present on both the sides or just on one side of the leaf.

The structure of the stomata consists of a kidney shaped epidermal cell with an opening in the center which is known as a pore. Inner walls of the guard cells face the aperture and are thicker than the outer layers. Guard cells also have large vacuoles. The cells which surround the guard cells are known as subsidiary or accessory cells.

The most important and major function of stomata is the exchange of gases. In simple terms we can say that the plant takes CO2 from the atmosphere and gives out O2 which is utilized by animals and human beings.

Stomata Function in Photosynthesis

Photosynthesis is a process of manufacturing food in the plant with the help of sunlight, carbon dioxide and water. The plant takes carbon dioxide from the atmosphere which is taken through the stomata. The water molecule is broken down into hydrogen and oxygen and the oxygen is then released in the atmosphere as a by product. This oxygen is also released through the stomatal openings. Hence we can say that the medium of gaseous exchange is stomata. This is a medium of cellular respiration in plants. The work which a nose does for us is similar to the stomata in a plant.

Stomata Function in Transpiration

Transpiration is a process of evaporation of water from the surface of the plant. This is done through the stomatal openings. This helps the plant to get cool and also helps in the transfer of minerals and other materials to different parts of the plant. As the plant takes water from the soil, the openings absorb other minerals. But to transfer these minerals to the surface of the plant, the water on the surface of the plant should be evaporated. Once it is evaporated, it will develop pressure which will force the roots to absorb water from the soil and will be transferred to the tips of the plants. The major work of evaporation of water is done by stomata. Go through what is transpiration to get a better idea.

Opening and Closing of Stomata

Apart from the transpiration and photosynthesis process, stomata also have another very important function. This function is to save water loss. This is done by the opening and closing of the stomata. Plants cannot make their food at night. This is because they do not get sunlight which in turn does not open the stomata. As soon as sunlight strikes the plant’s leaf, there is a change in turgor pressure. This forces the guard cells to form a crescent shape and open the pores of the stomata. This makes the pores open and the processes of photosynthesis, transpiration and respiration are continued. But once the sun sets, the guard cells lose the turgor pressure and this results in the closing of the stomata. This opening and closing also depends upon the environmental conditions. In adverse condition such as very high temperature, the stomata closes itself to stop water loss. They sometimes also keep moist air closed inside themselves to prevent the plant’s tissues from freezing in excess cold.

Factors that affect the rate of transpiration
1. Light
Plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of the stomata (mechanism). Light also speeds up transpiration by warming the leaf.
2. Temperature
Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises. At 30°C, a leaf may transpire three times as fast as it does at 20°C.
3. Humidity
The rate of diffusion of any substance increases as the difference in concentration of the substances in the two regions increases.When the surrounding air is dry, diffusion of water out of the leaf goes on more rapidly.
4. Wind
When there is no breeze, the air surrounding a leaf becomes increasingly humid thus reducing the rate of transpiration. When a breeze is present, the humid air is carried away and replaced by drier air.

In some ways, every person’s blood is the same. But, when analyzed under a microscope, distinct differences are visible. In the early 20th century, an Austrian scientist named Karl Landsteiner classified blood according to those differences. He was awarded the Nobel Prize for his achievements.

Landsteiner observed two distinct chemical molecules present on the surface of the red blood cells. He labeled one molecule “A” and the other molecule “B.” If the red blood cell had only “A” molecules on it, that blood was called type A. If the red blood cell had only “B” molecules on it, that blood was called type B. If the red blood cell had a mixture of both molecules, that blood was called type AB. If the red blood cell had neither molecule, that blood was called type O.

If two different blood types are mixed together, the blood cells may begin to clump together in the blood vessels, causing a potentially fatal situation. Therefore, it is important that blood types be matched before blood transfusions take place. In an emergency, type O blood can be given because it is most likely to be accepted by all blood types. However, there is still a risk involved.

A person with type A blood can donate blood to a person with type A or type AB. A person with type B blood can donate blood to a person with type B or type AB. A person with type AB blood can donate blood to a person with type AB only. A person with type O blood can donate to anyone.

A person with type A blood can receive blood from a person with type A or type O. A person with type B blood can receive blood from a person with type B or type O. A person with type AB blood can receive blood from anyone. A person with type O blood can receive blood from a person with type O.

Because of these patterns, a person with type O blood is said to be a universal donor. A person with type AB blood is said to be a universal receiver.

Blood has three main functions: transport, protection and regulation.

Transport
Blood transports the following substances:
Gases, namely oxygen (O2) and carbon dioxide (CO2), between the lungs and rest of the body
Nutrients from the digestive tract and storage sites to the rest of the body
Waste products to be detoxified or removed by the liver and kidneys
Hormones from the glands in which they are produced to their target cells
Heat to the skin so as to help regulate body temperature

Protection
Blood has several roles in inflammation:
Leukocytes, or white blood cells, destroy invading microorganisms and cancer cells
Antibodies and other proteins destroy pathogenic substances
Platelet factors initiate blood clotting and help minimise blood loss

Regulation
Blood helps regulate:
pH by interacting with acids and bases
Water balance by transferring water to and from tissues

Composition of blood

Blood is classified as a connective tissue and consists of two main components:

1. Plasma, which is a clear extracellular fluid, Blood plasma is a mixture of proteins, enzymes, nutrients, wastes, hormones and gases.

2. Formed elements, which are made up of the blood cells and platelets
The formed elements are so named because they are enclosed in a plasma membrane and have a definite structure and shape. All formed elements are cells except for the platelets, which tiny fragments of bone marrow cells.
Formed elements are:

Erythrocytes, also known as red blood cells (RBCs)

Red blood cells (RBCs), also known as erythrocytes, have two main functions:
To pick up oxygen from the lungs and deliver it to tissues elsewhere
To pick up carbon dioxide from other tissues and unload it in the lungs

Leukocytes, also known as white blood cells (WBCs)

Whenever a germ or infection enters the body, the white blood cells snap to attention and race toward the scene of the crime. The white blood cells are continually on the lookout for signs of disease. When a germ does appear, the white blood cells have a variety of ways by which they can attack. Some will produce protective antibodies that will overpower the germ. Others will surround and devour the bacteria.

Platelets

The human body does not handle excessive blood loss well. Therefore, the body has ways of protecting itself. When, for some unexpected reason, sudden blood loss occurs, the blood platelets kick into action.

Platelets are irregularly-shaped, colorless bodies that are present in blood. Their sticky surface lets them, along with other substances, form clots to stop bleeding.

When bleeding from a wound suddenly occurs, the platelets gather at the wound and attempt to block the blood flow. The mineral calcium, vitamin K, and a protein called fibrinogen help the platelets form a clot.

Overviews of Animal Cells

Overviews of Plant cells

There are two main types of cells. They are prokaryotic cells and eukaryotic cells. Prokaryotic cells are found in bacteria and archaea and are also called prokaryotes. Eukaryotic cells are found in pretty much everything else such as plants and animals.

EUKARYOTIC Cell Structure and Functions:

Cell Membrane: The cell membrane allows certain molecules to enter or leave the cell. It separates internal metabolic reactions from the external environments. It also allows the cell to excrete wastes and to interact with its environment.

Nucleus: The nucleus communicates with the surrounding cytosol via the numerous nuclear pores. It also houses and protects the cell’s genetic information.

Nucleolus: The nucleolus is where DNA is concentrated when it is in the process of making ribosomal RNA.

Ribosomes: The ribosomes direct protein synthesis in the cytoplasm.

Cytosol: The cytosol is the “soup” within which all the other cell organelles reside and where most of the cellular metabolism occurs. The cytosol is full of proteins that control cell metabolism including signal transduction pathways, glycolysis, intracellular receptors, and transcription factors.

Centrosome: The centrosome is an area in the cell where microtubles are produced.

Golgi Apparatus: The golgi apparatus is a system of flattened, membranous sacs. The sacs nearest the nucleus recieve vesicles from the ER containing newly made proteins or lipids. The stacked membranes modify the vesicle contents as they move along the golgi apparatus. The protiens get “address labels” that direct them to various other parts of the cell.

Mitochondria: The mitochondria transfer energy from organic molecules to adenosine triphosphate.

Endoplasmic Reticulum: The ER functions primarily as an intracellular highway, a path along which molecules move from one part of the cell to the other. The Rough ER produces phospholipids and proteins. These proteins are later exported from the cell or inserted into one of the cell’s own membranes. The Smooth ER builds lipids such as cholesterol. It also produces the steroid hormones estrogen and testosterone.

Lysosomes: The lysosomes contain digestive enzymes which break down large molecules, such as proteins, nucleic acids, carbohydrates, and phospholipids.

Cytoskeleton : The cytoskeleton is a network of thin tubes and filaments that give shape to the cell from the inside.

Plant cells have three kinds of structures that are not found in animal cells and that are extremely important to plant survival: plastids, central vacuoles, and cell walls.

Cell Wall: The cell wall is a rigid layer that lies outside the cell’s plasma membrane. Plant cell walls contain a carbohydrate called cellulose. Pores in the cell wall allow water, ions, and some molecules to enter and exit the cell.

Plastids: They are organelles that are surrounded by a double embrane and contain their own DNA. Chloroplasts are a type of plastid. Chloroplasts use light energy to make carbohydrates from carbon dioxide and water.

Central Vacuoles: The central vacuole is a large, fluid-filled organelle that stores not only water but also enzymes, etabolic wastes, and other materials.

The primary function of the respiratory system is to exchange oxygen and carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli. The layers of cells lining the alveoli and the surrounding capillaries are each only one cell thick and are in very close contact with each other. This barrier between air and blood averages about 1 micron (1/10,000 of a centimeter) in thickness. Oxygen passes quickly through this air-blood barrier into the blood in the capillaries. Similarly, carbon dioxide passes from the blood into the alveoli and is then exhaled.

We can improve the quality and increase the quantity of food in many ways such as :
(a) use quality breeds

(b) Introducing the use of modern technology

(c) Provision of education, training and guidance to farmers

(d) Research and development on food production

(e) Optimum use of land and irrigated areas

(f) Efficient land management.