Structure of cell YouTube Lecture Handout

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Structure of Cell YouTube Lecture Handout

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  • Cell membrane

  • Cytoplasm

  • Organelles

  • Cytoskeleton

  • Inclusion bodies

  • Nucleus

    Structure of cell Image-1

    Structure of Cell Image-1

    Structure of cell Image-1

    Structure of cell Image-2

    Structure of Cell Image-2

    Structure of cell Image-2

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

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

B. 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

    Plasma Membrane Structural Components

  • Structure

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

Functions of Cell Membrane

  • 1 Protection

  • 2 Selective permeability

  • 4 Links adjacent cells together

  • 5 Forms glycocalyx

  • 6 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

1. 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

2. 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

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