The Fundamental Unit of Life

Mitochondria

Mitochondria is a cell organelle found in almost all eukaryotic cells. Mitochondria generate energy which is necessary for life processes through aerobic respiration. Respiration takes at the cellular level in mitochondria. Hence, the MITOCHONDRIA IS KNOWN AS THE POWERHOUSE OF THE CELL.

Mitochondria has a spherical to oval shape. Mitochondria are covered with two layers of membrane. The outer layer of the membrane of mitochondria is spherical and porous while the inner layer of mitochondria has folded shape. The folded shape of the inner membrane of mitochondria facilitates enough space to release energy necessary for life. Mitochondria are the only cell organelles that have their own DNA and ribosomes. With these special structures, mitochondria are able to make some of their own proteins.

The number of mitochondria varies from cell to cell and tissue. Muscles and liver cells may have hundreds to thousands of mitochondria while red blood cells do not have mitochondria.

The Mitochondria was discovered in 1857 by a Swiss scientist Albert von Kolliker.

The energy we required for life processes is produced by mitochondria found in the cytoplasm of the cells. Mitochondria produces energy by using nutrients in the form of glucose. This energy released by mitochondria is in the form of Adenosine Triphosphate. Adenosine Triphosphate is popularly abbreviated as "ATP".

Along with producing energy, mitochondria store calcium, generate heat and plays important role in the growth and death of the cell. Calcium is used for cell signaling.

Plastids

Plastid is a membrane bound cell organelle only found in plant cells. There are mainly two types of plastids, viz. chromoplasts and leucoplasts.

Chromoplasts

Chromoplats are the coloured plastids found in plant cells. Chromoplasts synthesise and store colour pigments in the different parts of the plant. Chromoplasts give the characteristic colour to the leaves, fruit, and flower of plants.

Chloroplasts

Chromoplasts containing the pigments are known as Chloroplasts. Chloroplasts further can be divided into two types. These two types of chloroplasts are chlorophyll and carotenoids.

Chlorophyll

Chlorophyll is a pigment which gives green colour to the plant. It is mainly found in the leaves of the plant. Because of the chlorophyll, the leaves of a plant look green.

It is the chlorophyll because of which photosynthesis takes place in a plant. Photosynthesis is the synthesis of food using sunlight, carbon dioxide and water.

Carotenoids

A group of natural pigments found in plants is known as Carotenoids. These pigments are yellow, orange, and red. Carotenoids give characteristic colours to the fruits, flowers, buds, and roots of a plant. These specific colours enables flowers to attract insects that are necessary for pollination.

Stroma

The fluid filled internal space of chloroplasts is known as stroma. The stroma contains starch, chloroplasts DNA, and ribosomes similar to mitochondria. The process of photosynthesis starts in the stroma.

Leucoplasts

Leucoplasts are the plastids that stores materials such as starch, oil, proteins, etc. in plants. Leucoplasts are non-pigmented plastids in contrast with chromoplasts. Leucoplasts do not contain chlorophyll because of this it does not take part in photosynthesis and hence are present in non-photosynthetic tissues of plants. Leucoplasts are generally found in the roots, bulbs, and seeds of a plant.

Vacuoles

Vacuoles are membrane bound cell organelles. Vacuoles are similar to lysosomes or specialized lysosomes and do cleaning processes and balance water inside and outside of the cell.

Vacuoles have no specific shape and size. The size and shape of vacuoles depend upon the requirement of the cell. Vacuoles are formed by the fusion of multiple vesicles and are hence larger than the vesicles in size. The size of vacuoles is smaller in animal cells compare to plant cells.

Vacuoles may store liquid or solid and hence are called the storage sacs of liquids or solids. The membrane of the vacuoles keeps the material inside separate from the outer environment of the cell.

Vacuoles isolate toxic or harmful material or waste products inside the cell and get rid of these materials. Vacuoles support the structure of the leaves and flowers of a plant along with the turgidity and rigidity of the cells.

Vacuoles stores amino acids, sugars, and other various amino acids and proteins which are necessary for the life of plant cells. In unicellular organisms, an amoeba food vacuole contains food items that have to be consumed.

In plants, vacuoles may occupy 50% to 60% of the cell volume.

Cell Division

The process of division of cells to form new cells is called Cell division. The growth and reproduction of organisms take place through cell division.

There are two types of cell division take place in eukaryotes: Mitosis and Meiosis.

Mitosis

The division of cells into two cells for the growth and repair of the tissues is called Mitosis. The Mitosis is known as Vegetative Division also.

The cell from which new cells are formed is called Mother Cell or Parent Cell. And the new cells produced after division are called Daughter Cells.

Daughter cells are copies of the parent cell and hence contain the same genetic information. This means daughter cells are genetically identical to the parent cell.

The daughter cells produced in the process of mitosis have the same number of chromosomes as the mother cells.

Meiosis

The division of cells for reproduction in eukaryotes is known as Meiosis.

The meiosis takes place in the specific cells of reproductive organs of plants and animals. In the meiosis consecutive two divisions take place to complete the division. In this division, four cells are formed instead of two in mitosis. The cell divides to form gametes which give rise to offspring after fertilisation. The new cells formed in the mitosis have half number of chromosomes as the mother cells. In humans, the number of chromosomes is 46 in each cell. Hence, the daughter cell produced for reproduction by meiosis has a total of 23 chromosomes.