Structure of cell YouTube Lecture Handout

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Structure of Cell YouTube Lecture Handout


  • Cell membrane

  • Cytoplasm

  • Organelles

  • Cytoskeleton

  • Inclusion bodies

  • Nucleus

Structure of cell Image-1

Structure of Cell Image-1

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Structure of cell Image-2

Structure of Cell Image-2

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Cell Membrane Fluid Mosaic Model

The model was proposed by Singer & Nicolson in 1972

Structure of membrane

  • 7-10 nm (70 to 100 A) in thickness.

    • Tri layered structure- two electrons dense and one electron lucent layer

  • Biochemical composition:

    • Lipids

    • Proteins

    • carbohydrates

  • Lipids --- 40%.

    • Phospholipids (Phosphatidyl choline, Phosphatidyl ethanolamine, Sphyngomyeli etc.)

    • Cholesterol

    • Glycolipids

      • Functions : major barrier to water soluble sub. like urea, glucose & ions. but alcohol, oxygen & carbon dioxide can easily pass

  • Proteins -- 50%

    • Glycoproteins

    • Lipoproteins

  • Two types

    • Integral proteins: run throughout the mem. & act as channel, carriers etc.

    • Peripheral proteins: mostly present inside of the mem. & act as enzymes

  • Carbohydrates --10%

    • Glycoproteins

    • Glycolipids

  • Functions;

  • Have –ve charge so makes cell surface –ve that repels negative objects

  • Glycocalyx causes attachment of cells to each other

  • Some carbohydrates enter into immune reaction

  • Many act as receptors for binding hormones like insulin

Plasma Membrane Structural Components

Plasma Membrane Structural Components

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  • Structure

  • Most accepted model is FLUID MOSAIC model of Singer and Nicolson(1972)

Functions of Cell Membrane

  1. Protection

  2. Selective permeability

  3. Links adjacent cells together

  4. Forms glycocalyx

  5. Partcipate in immune response

3 Proteins Act As

  • Channels-voltage gated, ligand gated

  • Carriers

  • Pumps

  • Receptors

  • Contribute to cytoskeleton

  • Serves as enzymes

Cytoplasm and Organelles

  • Cytoplasm is aqueous substance in which organelles are dispersed.


  • Organelles are permanent components bounded by limiting membrane. These are:

  • Mitochondria, endoplasmic reticulum, ribosomes, golgiapparatus peroxisomes, centrosomes, lysosomes and centrioles

Functions of Organelles

  • Mitochondria (power house) makes ATP available

  • Endoplasmic reticulum

    • RER - involved in protein synthesis

    • SER -Site of lipid synthesis

    • -Contains enzymes controlling glycolysis

    • Also contain detoxifying enzymes

  • Ribosomes attached to RER & composed of RNA

    • Protein synthesis

  • Golgi apparatus

    • Concen. of proteins & polysaccharides

    • Packaging & formation of vesicles

    • Completion of glycoprotein synthesis

  • Lysosomes: intracellular digestive system, contain about 50 different hydrolytic enzymes

    • Make defense system of body

    • - Bacteria & debris of dead tissues taken up by the cells are destroyed

  • Peroxisomes: contain oxidases mainly present in kidney & liver cells.

    • Detoxify drugs & neutralize free radicals

    • Catalase one of the enzymes, breaks toxic hydrogen peroxide into water & oxygen

  • Centrioles: initates cell division

  • Nucleus:

    • -Responsible for transmission & expression of genetic information

    • -Cell reproduction & multiplication

    • -Synthesis of RNA

  • Chromatin: network of threads composed of DNA & proteins

  • Chromosomes: thread like st. formed from chromatin at the time of cell division. Pass genetic information

    • -There are 23 pairs of chromosomes. 22 are somatic & one pair of sex chromosomes

Inclusion Bodies

Cytoplasmic inclusions (temporary components) are also present. They are not living st.

These are

  • Stored foods

    • Fat as droplets in a section they look like signet ring

    • Carbohydrate

    • Glycogen can only be stained by PAS (periodic acid-Schiff) & gives a brilliant red colour

    • Proteins rarely stored

  • Secretary granules

    • like digestive enzymes synthesized in cytoplasm

3. Pigments

  • A Endogenous pig.

    • Hemoglobin & it’s derivatives eg. Hemosiderin,

    • Melanin

  • B Exogenous eg. lipofusin, dust, minerals like lead or silver