cell by dr. bbt for paramedics

7/28/2019 Cell by Dr. BBT for Paramedics

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2. CELL

By:-

Dr. B. Bhusan Tamrakar (MD)


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Cell

Cell is the structural & functional unit of

human being. It was 1st discovered by Robert

Hook in 1665 AD.

Structure of Human cell:-

1. Cell membrane (Plasmalemma),

2. Cytoplasm (Protoplasm) &

3. Nucleus (brain of the cell).


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1. Cell membrane (Plasmalemma)

It surrounds cytoplasm & other organs.

It provides shape for cell

It transports the nutrients & useful materials

inside the cell & removes waste materials.

It helps to move molecules from lower

concentration to higher.

It provides immunological identity, which actsas Phagocytosis.


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2.i. Cytoplasm (Protoplasm):-

This is a fluid located between the cellmembrane and the nucleus.

The fluid is slightly opaque, colorless &soft jelly

like substance.It consists of water, amino acids carbohydrates,

salts & etc.

It contains matrix, organelles (Mitochondria,ER, Ribosomes, Lysosomes, Golgi apparatus)

& inclusions.


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2. Cytoplasm (Protoplasm):-contd

2.i.a. Mitochondria (power house of cell):-

- produces energy for cell,

- helps in completion of cellular respiration,

- produces energy from glucose in the presence of

oxygen.


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2.i.b. Endoplasmic reticulum

i. Rough:- is a single, bilayer. It is organised into

stacks of large flattened sacs called cisternaethat are studied with ribosomes on the

cytoplasmic side. RER synthesizes protein for

golgi apparatus, plasma membrane &lysosomes.

ii. Smooth:-It is a network of sacs, vesicles &

tubules which continues with RER, but lacksribosome. It synthesizes proteins, fatty acids

& hormones.


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ER


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2.i.c. Ribosomes:-

It composed of rRNA & protein.

It is called factories of protein, because itsynthesizes protein.

2.i.d. Lysosomes:-It is spherical membrane enclosed withorganelles.

It contains 60 hydrolyte enzymes required forintracellular digestion.

So, it acts on the digestive system of cell.


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lysosome


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2.i.e. Golgi Apparatus:-

It consists of disc-shaped smooth cisternae.It is associated with numerous small membrane

bound vesicle.

It is the site of posttransiatinnal modification &sorting of newly synthesized proteins & lipids.

Functions:-

Helps in synthesis of polysachharides.Helps in production of hormone, enzyme &

protein.


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Golgi apparatus


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2.ii. Inclusions:-

These are vacoules or fat droplet.

It is also called storage of wastes.

There are clear circular spaces.These spaces contains waste which are

secretions formed by cell.


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3. Nucleus ( brain of the cell):-

They are rounded & elongated structure usually

placed in the centre of the cell.

It is composed of nuclear envelope, chromatin,

nucleolus & nucleoplasm.

In the nucleus of every cells has the

chromosomes containing the genes composed

of segments of DNA & RNA.

It synthesizes protein & RNA.


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Nucleus


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3.a. DNA (Deoxyribonucleic acid):-

It is made up of 2 polynucleotide chains.Each nucleotide is composed of a deoxyribase

& phosphate molecule.

DNA contains genetic information or geneticcode.

This information is transcribed into RNA in the

nucleus, which acts as messenger.It consists of Adenine, Guanine, Cytosine &

Thymine.


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3.b. RNA (Ribonucleic Acid):-

It is found in the nucleolus & the cytoplasm.

In RNA Thymine is replaced by Uracil.

mRNA copies DNA & migrates to cytoplasmwhere it becomes associated with ribosome,

this is the site of protein synthesis.

tRNA is in the cytoplasm which combineswith complimentary bases on the mRNA.

cell by dr. bbt for paramedics

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