CELL

 Introduction :- cell is the structural and functional unit of the living body.

Structure of cell study under 3-heading:- 

⦁ Cell membrane.

⦁ Cytoplasm. 

⦁ Nucleus. 

1. Cell membrane:- 

⦁ This membrane separate the I.C.F from E.C.F

⦁ Cell membrane is semi permeable membrane.

⦁ Thickness of cell membrane – 75A-111A.

Composition of cell membrane: -protein 55% - mainly glycoprotein lipid – 40% - mainly phospholipids carbohydrate – 5% 

Function of lipid layer:- 

 It allows only fat soluble substance.

 But it not allows water soluble substance.

Function of protein layer:- 

This provides structural integrity of cell membrane.

Work as carrier protein.

Provide protein channel. 

carbohydrate:- Glycolipid,Glycoprotein

Function:- Cell identity marker during tissue formation.

Function of cell membrane:- 

 Protective function.

 Work as selectively permeable membrane.

Absorptive function.

Excretory function.

 Gasses exchange through this membrane.

 Maintain cell size and shape. 

Cytoplasm: -cellular substance between plasma membrane and nucleus is called cytoplasm.

Cytoplasm composed by :- Cytosol + Organelles.

Cytosol :- clear liquid fluid is cytosol.

Organelles:-

⦁ Some organelles bounded by limiting membrane.

⦁ Some are not bounded by limiting membrane. Like- Ribosome, cytoskeleton.

⦁ Endoplasmic reticulum: - Two types of endoplasmic reticulum.

a. Rough endoplasmic reticulum / granular endoplasmic reticulum:- 

 Ribosome attach on this reticulum. So protein synthesis occurs here.

b. Smooth endoplasmic reticulum: - / a granular endoplasmic reticulum.

 There no ribosome attaches.

This is responsible for synthesis of non protein substance like: - lipid, steroid hormone

⦁ Golgi apparatus/ Golgi body :- 

Absent in RBC.

This function is packing and transporting the protein which formed from R.E.R to different part of the cell so called post office of the cell.

⦁ Ribosome / protein factory :- 

 Ribosome present of R.E.R and some freely in cytoplasm.

Ribosomes are made up by 35% protein and 65% Rrna Function :- protein synthesis so this is also known as protein factory.

⦁ Lysosome :- 

 Lysosome are membrane bound organelles.

Lysosome has many digestive and hydrolytic enzyme.

Lysosome enzyme destroys the entire cell in some pathological condition so this called autolytic activity of lysosome.

Heterophagy – digest the extracellular material.

Autophagy – Digest the intracellular material. Like – worn-outorganelles.

GARBAGE SYSTEM OF CELL IS – LYSOSOME

⦁ MITOCHONDRIA :- 

 It is bilayered organelles.

 Outer mitochondrial membrane is smooth and inner is folded is called cristae.

 Inner cavity is filled with fluid called Matrix which contains many enzymes. 

 Mitochondria is called power house of the cell.

⦁ Peroxisomes :-

 This is membrane bounding organelles.

 This contain enzymes like :- catalase, urate oxidase,

 This is mainly found in liver.

 Main function is detoxification of toxic substance in cell.

⦁ Centrosome :-

⦁ It located near the nucleus.

⦁ It consists by two components that is a pair of centrioles and pericentriolar material.

⦁ Centrosome is absent in nervous system so there regeneration is not occur. 

⦁ Centrosome are responsible for the movement of chromosomes during cell division.

⦁ Cytoskeleton :-

⦁ This is the complex network of the structures which present throughout the cytoplasm.

⦁ It maintains the shape of the cell and gives support to cell.

⦁ This consists by three protein components that are follows:-microtubules, intermediate filaments, microfilaments.

3. Nucleus:-

Structure of nucleus:-

⦁ Nuclear membrane

⦁ Nucleoplasm

⦁ Nucleolus/nucleoli

⦁ Nuclear membrane: -Double layered and porous in nature. This allow the nucleoplasm to communicate with the cytoplasm.

⦁ Nucleoplasm :- it contain material in the form of D.N.A which form gene. D.N.A made by thread like material known as chromatin. In dividing cell just before division the chromatin become rod shape called chromosomes. Chromosome carry the information about hereditary character.

⦁ Nucleolus: -it contain R.N.A and protein R.N.A is synthesized by 5-different pair of chromosomes.

D.N.A (Deoxyribonucleic Acid) :- D.N.A Present In Nucleus And Mitochondria.

Structure Of D.N.A Is Double Helical Structure. It Is Formed From:-

⦁ Deoxyribose-Sugar

⦁ Phosphate

⦁ Nitrogenous Base

D.N.A Chain Formed By:-

⦁ Deoxyribose-Sugar

⦁ Phosphate

⦁ This Chain Connected By Nitrogenous Base

Nitrogenous Base Of D.N.A:-

Purine →Adenine And Guanine

Pyrimidines → Thymine And Cytosine

R.N.A (Ribose Nucleic Acid):-

Structure of R.N.A

⦁ Each R.N.A Molecules Consists Of Single Strand Of Polynucleotide.

⦁ Each Nucleotide In R.N.A Formed From :-

⦁ Ribose-Sugar

⦁ Phosphate

⦁ One Organic Base

Organic Base in R.N.A:- 

⦁ Purines → Adenine +Guanine

⦁ Pyrimidines → Uracil + Cytosine

Types Of R.N.A → 3 Types Of R.N.A

1. mRNA (Messenger rR.N.A) :- It Carry The Genetic Code Of Amino Acids Sequence For The Synthesis Of Protein From The D.N.A To Cytoplasm.

2. tRNA (Transfer R.N.A) :- This R.N.A Responsible For Decoding The Genetic Message Present In mRNA.

3. rRNA (Ribosomal RNA) :-

⦁ It Present In Ribosome. 

⦁ It Responsible For Protein Synthesis.