The fundamental unit of life : CELL

class 9 

Biolog

chapter 1

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The fundamental unit of life : CELL

The cell is basic structural and functional unit of living organism .

Ø    Discovery of Ce HOOKE

Prokaryotic

➧  These organisms have primitive and incomplete cells . in this nucleus is absent.

➧  It contains single chromosome .

➧  Cell division take place by fission or budding .

Eukaryotic

➧  These have advanced and complete cells .

➧ In this nucleus is present

➧  It contain more than one chromosome

➧  Membrane bound cell organelles such as mitochondria, plastids, endoplasmic reticulum , Golgi apparatus , Lysosomes , etc.. are present.

➧  Cell division occurs by mitotic or meiotic  cell division.

PLASMA MEMBRANE

It permits the entry and exit of many materials in the cells. The plasma membrane  is called a  permeable membrane.

Diffusion

Some substances  like as CO₂ ,O_{2 ,}H₂O,etc..  can move across the plasma membrane  through a process name diffusion.

Osmosis

Osmosis is the movement of water through a half permeable membrane from a region of high concentration to a region of lower concentration, tending to equalise the concentrations of the water. Osmosis is passive transport, meaning it does't require energy to be applied.

Structure of Plant cell

Structure of Animal

Cell wall

➧  In plant cells , these occurs a hard cell wall

➧ It is made up of a fibrous polysaccharide (carbohydrate) called cellulose.

➧  It permit the plant cell to become turgid.

➧  It provides mechanical strength to support the cell.

➧  It is freely permeable to water and substance  in solution.

➧  It lie out side of the cells

Nucleus

➧  The nucleus is  a large , centrally located spherical cellular component .

➧  It is bounded by  two nuclear membrane.

➧  The nucleus controls all metabolic activities of the cell.

➧  It regulates  the cell cycle

➧  It is  concerned with the transmission of secretions .

➧  Golgi appratus is also involved in the synthesis of cell wall, plasma membrane and Lysosomes .

Lysosomes

➧  Lysosomes serve as intracellular digestive system , hence ,called digestive bags. 

➧  They destroy any foreign material l which enter  the cell such as bacteria and virus.

Mitochondria

➧  Mitochondria are sites of cell respiration.

➧  They are known as ‘power house’ of the cell.

➧  The energy stored in ATP is used by the cell.

➧  ATP is generally known as energy carrier or energy currency of the cell.

➧  Mitochondria are ready to make  some of their own proteins ; so they are regarded as semiautonomous organells.

Plstids

➧  Plastids occur  in most plant cells and are absent in animal cells. Plastids are of following three types;

1.     Chromoplasts

2.     Chloroplasts

3.     Leucoplasts

Chloroplasts

Chloroplasts are present  in green alage and higher plants . they have a green pigment called chlorophyll and they are involved in the photosynthesis of food . so chloroplasts are the “Kitchen of the cells”. Each chloroplast is bounded by two unit membrane like the mitochondria.

1.     Chloroplasts trap solar power and utilises it to manufacture food for the plant.

2.     Chloroplasts impart various colours to flowers to attract insects for pollination.

3.     Leucoplasts store food in the form of carbohydrates  (starch, fats and protein.