Cell Structure 2 Pau Ldh

CELL STRUCTURE AND CELL Class 9th Submitted by: Alisha  Vanita  Jasmine Under Guidance of: Mrs. Kusum Lata (Science Mistress)

Teacher TrainerMiss Harinder Kaur Student TrainerMiss Rachna

CELL The cell is the basic

structural and functional unit of life.

DISCOVERY OF CELL Cell was

discovered by Robert Hooke in 1665.

TYPES OF CELL:EUKARYOTIC CELL PROKARYOTIC CELL

PROKARYOTIC CELL: They are the cells which have primitive organization of

genetic material. their “DNA” is not enclosed in a nuclear membrane e.g.: BACTERIA HUMAN RBC etc.

EUKARYOTIC CELL: In the cells of plants and animals the genetic

material is located within the nuclear membrane.

STRUCTURE OF CELL Cells fall into one of two categories:

prokaryotic or eukaryotic (see Prokaryote). In a prokaryotic cell, found only in bacteria and archaebacteria, all the components, including the DNA, mingle freely in the cell’s interior, a single compartment.

CELL WALL  In plant cell the outer membrane is enclosed

by a rigid cellulose covering called cell wall.  Functions:-

1. It provides a definite shape to the cell. 2. It provides rigidity to the cell.

CELL MEMBRANE  It is the membranous covering of the

protoplasm (inner material) of the cell. It regulates the entry and exit ions and molecules in and out of the cells.  Functions:3. It allows exchange of specific materials. 4. Plasma membrane binds the semi-fluid content of the cells.

CYTOPLASM  The space between the plasma membrane & the

nucleus is filled by an amorphous, homogenous, colloidal liquid called cytoplasmic matrix.  Functions:1.It helps in exchange of materials between different cell organelles. 2.Breaking down of glucose takes place in the cytoplasm.

NUCLEUS  The dense spherical mass in the cytoplasm is

called nucleus. It contains chromosomes which are the bearer of hereditary characteristics called genes. It controls the activities of the cell.  Functions:1. Nucleus controls cell metabolism & other activities of the cell. 2. It directs cell differentiation & cell replication.

CELL ORGANELLAES  Inside the cytoplasm there are other minute

bodies which perform different functions called cell organelles. These are as under:

RIBOSOMES  These are sites for the synthesis of proteins.  Function:-

Ribosome help in protein synthesis inside the cell. Hence they are called protein factories of the cell.

MITOCHONDRIA  These are the sites for the production of energy

rich molecules & are, therefore called ‘power house’ of the cell.  Functions:1. Mitochondria provide important intermediates for the synthesis of several biochemicals like chlorophyll, cytochromes etc. 2. Synthesis of many amino acids occur in mitochondria. 3. This is the site for the oxidation glucose to provide energy in the form of ATP.

GOLGI BODIES  It is present around or above the centrioles

in all eukaryotic cells except mammalian RBC’s & mature sperms.  Function:1. It helps in the storage of secretary products. 2. It helps in the formation of cell plate during cell division.

PLASTIDS  These organelles are found only in plant

cell. Plastids are of three types1. Chromoplasts 2. Chloroplasts 3. Leucoplast

1.Chromoplasts:-contain fat soluble, yellow, orange or red colored pigment. They provide color to flowers & fruits, chromoplasts are formed either from fruits leucoplasts or chromoplasts. These are found in leaves, flowers, fruits etc. 2. Chloroplasts:-are green plastids which possess photosynthetic pigment chlorophyll, which is responsible for food preparation by photosynthesis. 3. Leucoplast:-are colourless plastids. THEY STORE THE RESERVE FOOD e.g. Amyloplasts store starch, aleuronoplasts store proteins & elaioplasts store fats. Functions:-1. Chloroplast helps in photosynthesis so are called kitchen of the cell. 2. Chromoplast provides color to flowers & fruits. 3. Leucoplast helps in the storage of food.

CENTROSOME  It is a small naked protoplasmic structure present near

the nucleus. Centro some consists of two small granules called centrioles.  Functions:1. They help in spindle formation during cell division in animal cell. Plants cells lack centrioles but the spindle is formed without their aid. 2. They act as basal bodies and give rise to cilia and flagella.

LYSOSOME  The lysosome is a small vesicle surrounded by a

single membrane a variety of digestive enzymes. These enzymes are released when the membrane bursts, permitting it to digest cellular structure. Thus lysosomes are involved in autolysis or self digestion of cells after their death. So are also called “suicidal bags”. Lysosomes are formed by golgi apparatus.

VACUOLES  These are fluid filled & membrane bounded spaces. In animal

cells vaculoes are smaller in size. In mature plants cells the small vacuoles fuse to form A single large vacuole. Vacuoles are bounded by A membrane known as tonoplast. They are filled with A fluid called cell sap which consists of free water & A variety of compounds including minerals, sugars, amino acids, proteins & metabolic wastes.  Functions:- 1. Vacuoles help the cell to remain turgid. 2. They play an important role in growth by helping in the elongation of cells. 3. In protozoan like amoeba & paramecium the vacuoles help in osmo-regulation.