The process by which living things produce more living things of their own kind is called the reproduction. The older ones are called as parents and newly formed are called as progeny.
Importance of Reproduction:
- It helps in increasing number of the organisms.
- Continuity of life on the earth crust.
- Transmission of genetic material from one generation to the next.
- Continuation of life with a fresh start.
- The smallest independently functioning unit in the structure of an organism, usually consisting of one or more nuclei surrounded by cytoplasm and enclosed by a membrane. Cells also contain organelles such as mitochondria, lysosomes, and ribosomes. (LoF)
- It is the Basic unit of a living thing. (LoF)
- The mass of protoplasm having cytoplasm and nucleus surrounded by cell membrane is called a cell. But in the case of a plant cell, the plasma membrane is covered by a cell wall.
- The cell is the basic structural and functional unit of life. i.e. It means all the living organisms are composed of the cell and they perform different activities due to the presence of the cell.
- It was first discovered by ROBERT HOOKE in 1665 during observing the thin slide of cork. Later ROBERT BROWN in 1831 discovered nucleus in the cells of orchids.
An animal cell typically contains several types of membrane-bound organs or organelles. The nucleus directs activities of the cell and carries genetic information from generation to generation. The mitochondria generate energy for the cell. Proteins are manufactured by ribosomes, which are bound to the rough endoplasmic reticulum or float free in the cytoplasm. The Golgi apparatus modifies, packages, and distributes proteins while lysosomes store enzymes for digesting food. The entire cell is wrapped in a lipid membrane that selectively permits materials to pass in and out of the cytoplasm. (LoF)
Plant cells contain a variety of membrane-bound structures called organelles. These include a nucleus that carries genetic material; mitochondria that generate energy; ribosomes that manufacture proteins; smooth endoplasmic reticulum that manufactures lipids used for making membranes and storing energy; and a thin lipid membrane that surrounds the cell. Plant cells also contain chloroplasts that capture energy from sunlight and a single fluid-filled vacuole that stores compounds and helps in plant growth. Plant cells are surrounded by a rigid cell wall that protects the cell and maintains its shape. (LoF)
STRUCTURE OF TYPICAL PLANT CELL:
- Size = 0.01mm – 0.1mm (dia)
- In 1 cubic inch – 15 million to 15 billion
- Largest cell (pulp of watermelon)
The basic components are:
- Cell Wall
- Cell Membrane
- It is made of proteins and lipids.
- Outermost boundary of the plant cell (See Picture)
- Not found in animal cell
- Different from that of prokaryotes both in structure and chemical composition.
- Cell wall can be separated from the cell without killing it.
- When the cell dies, cell wall persists which shows it is non-living.
- The cell wall of a woody plant is thick.
- Cell wall provides protection and support to the cell.
- It gives a definite shape to the cell
- Outermost layer in an animal cell and next to cell wall in the plant.
- It is thin, elastic, and can repair itself to some extent.
- The cell membrane is chemically composed of lipids and proteins: 60-80% proteins while 20-30% lipids.
- A small amount of carbohydrates is also present.
- It provides mechanical support and external frame to Protoplasm (living content of a cell).
- It is semi-permeable that allows some molecules to pass through it and not others.
- It is a fluid portion of cell lying outside of the nucleus.
- It is found inside the cell membrane.
- Chemically it is about 90% water and forms a solution having all the fundamental bio-molecules of life.
- Acts as the storehouse of vital chemicals.
- It is a site for certain metabolic pathways, eg glycols’
- It contains:
- Endoplasmic reticulum
- Golgi apparatus
- Centriole (not in a plant cell).
- It is a network of channels or tubules extending throughout the cytoplasm
- The channels seem to be in contact with the plasma membrane.
- It has two types:
- Rough ER – having ribosomes at its surface
- Smooth ER – don’t have ribosomes
- Provide mechanical support to the cell so that its shape is maintained
- SER plays important role in the transport of materials from one part of the cell to the other.
- SER helps in the synthesis of a number of molecules eg lipids.
- Tiny granules studied by Palade
- Composed of RNA and protein
- May be freely scattered in the cytoplasm or attached with the endoplasmic reticulum.
- Concerned with protein synthesis
- Small bodies may be filamentous or rod-shaped (See Picture)
- Structure of folded membrane made up of proteins and lipids.
- They are the powerhouse of the cell
- They play a basic role in respiration involving oxidation-reduction of the food material with the release of ATP.
- They were discovered by Mr. Golgi so-called Golgi bodies
- They are a collection of fluid-filled sac-like structure
- They are concerned with cell secretions. The secretions are products formed within the cell and then passed to outside
- It is involved in the synthesis of the cell wall in plants.
- (Lyso = splitting + soma = body)
- They were first isolated by Deduce in 1949. They are bounded by a single membrane and are simple sacs. (Picture at Endoplasmic reticulum)
- They release energy for extracellular digestion
- They are involved in phagocytosis ie digestion of foreign bodies and autophagy ie self-eating.
- An important and prominent structure lying inside the cell
- It may be spherical or irregular in shape
- In animal cells, it is present in the center
- In a plant cell, it lies close to the cell membrane as there is a large central vacuole
- The nucleus consists of:
- Nuclear membrane
- Its outermost membrane is called tonoplast
- Having water inside having salt + sugar and other organic material called sap.
- Pigments are present (purple, blue)
- The blue or purple color of flowers is due to sap.
DIFFERENCE B/W PLANT AND ANIMAL CELLS:
|ANIMAL CELL||PLANT CELL|
|1. No cell wall
2. More cytoplasm
3. Small vacuoles but large in number
4. Round in shape
5. The nucleus is present in the center
6. A large amount of Mitochondria
7. Heterotrophic cell
8. Chloroplast is absent
9. Centrioles are present
10. No rigidity due to the absence of cell wall
11. Plastid is absent
|1. The cell wall is present
2. Less cytoplasm
3. Big vacuole but only one
4. Oval in shape
5. Nucleus at periphery
6. Less amount of Mitochondria
7. Autotrophic cell
8. Chloroplast is present
9. Centrioles are absent
10. Rigidity due to the presence of cell wall.
11. Plastid is present.
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