Cell biology

Glycocalyx- polysaccharide ( mucopolysaccharide) and polypeptide.

Cell wall- bacterial cell wall is composed of peptidoglycan which is a colarbohydrate made of NAG & NAM.

  • It is heteropolymer of NAG and NAM.

  • Bacterial cell wall can be digested by lysozyme as it breaks the Beta 1,4- glycosidic bond.

Mesosome- It is analogous structure to mitochondria of eukaryotic cell.

  • Function- help in respiration.

  • Help in DNA replication and distribution of replicated DNA into daughter cells.

  • Secretion of materials.

  • Help in cell wall formation.

  • Increase the surface area so enzymatic activities also increases.

Chromatophore- Membranous extension in photosynthesis bacteria.

Contains pigments for purpose of photosynthesis.

Flagella- filament like, emerges from cell membrane.

  • There is wide range in number and arrangement of flagella in different bacteria.

Pili-

  • Shorter pili (fimbrae)- small bristle like, Attachment of bacteria to the substratum.

  • Longer pili (sex pili)- help in conjugation.

No role in motility.

Gas vacoule- made of pseudomembrane.

  • It is gas permeable and water impermeable.

  • Composed of protein.

  • Provides buoyoncy control.

Ribosome- size of 70S- 15-20 nm.

Plasmid DNA- provided certain unique phenotypic characters to bacteria.

  • Resistance to antibiotic.

  • Monitors bacterial transformation with foreign DNA.

Staining technique- by H.C gram.

  • Result- COLOURED i.e gram positive bacteria

  • Cell wall is single layered i.e of peptidoglycan (makes strong bond with crystal violet)

  • Thick

  • NON COLOURED i.e gram negative bacteria

  • Cell wall is double layered i.e of lipopolysaccharide and peptidoglycan.

  • Thin.

In mycoplasma, cell wall absent.

Size of eukaryotic cell- 10 micrometre to 20 micrometre.

Cell wall- fungi i.e of chitin (homopolymer of NAG)

Plants i.e of cellulose, hemicellulose, pectin, protein, lipids.

Algae i.e of cellulose, galactans, mannans, CaCO³

Middle lamella- made of calcium pectate( mainly) and magnesium pectate.

Acts as cementing layer.

Can be dissolved by activity of pectinase enzyme.

Plasmodesmata- living cytoplasmic connection between 2 adjacent plant cell.

Cell wall and middle lamella may be traversed by it.

Tertiary cell wall is present in tracheids of gymnosperm which is made up of cellulose and xylans.

  • Cell membrane is living structure.

  • Cell wall is non living structure.

Ratio of protein and lipid variable from cell to cell.

Cell membrane- protein- 52%

Lipid- 40%

Carbs- 8%

External protein- Removed easily by salt treatment.

  • 30% of total protein.

  • These bind with contractile protein like actin & spectrin and help with constriction of membrane.

Internal protein- 70% of the total protein.

Acts as transporter protein.

lipids- A. Phospholipid - main lipid

Amphipathic in nature.

Head ( polar and hydrophilic)- glycerol and phosphate.

Tail ( non polar, hydrophobic)- fatty acid ( saturated and unsaturated)

Cholesterol- rigid lipid which provide stability to membrane.

Acts as temperature buffer.

Carbohydrate- glycoprotein and glycolipid.

  • Acts as antigen.

  • Cell to cell recognition.

  • Asymmetrical nature of membrane due to its presence.

Fluid mosaic model- polar head is present towards outside as it ensures protection of hydrophobic tail of saturated fatty acid from aqueous environment.

Saturated fatty acid is inversely proportional to fluidity.

Movement of lipid.

  1. Flip flop

  2. Lateral

  3. Rotational

  4. Flexion

Movement of protein.

  1. Lateral

  2. Rotational

Endoplasmic reticulum

  • ER forms 50% of total membrane hence also known as system of membrane.

  • ER divides intracellular space into 2 part: a) luminal part and b) extra luminal part.

  • Cisternae are unbranched. (Protein synthesis)

  • Tubules are branched. ( Lipid synthesis)

  • Functions- ER provide mechanical support.

  • Cell wall formation.

  • Formation of desmotubule.

  • Reformation of nuclear envelope during telophase of cell cycle.

Function of RER.

  • Help in formation of lysosomal enzyme.

Function of SER.

  • help in lipid synthethesis like phospholipid, cholesterol, and steroidal hormone.

  • Synthesis of sex hormone like estrogen and progesterone.

  • Detoxification of liver cell.

  • Help in glycogen synthesis.

  • Help in formation of vacoule, glyoxysome and spherosome.

  • Synthesis and storage of vitamin D.

Microsomes.

Are fragments of ER associated with ribosomes.

Help in in vitro protein synthesis.

Sarcoplasmic Reticulum.

Modified SER present in muscle cell.

Help in supply of Ca+ ion for muscular movement.

Nissls granules.

Modified RER present in nerve cell.

Help in protein synthesis.

Myloid body

Modified SER.

golgi body - k/a dictyosome in plants as cisternae is not interconnected.

cisternae- diameter- 0.5 to 1 micrometre.

Generally 8-12 are present.

Concentrically arranged near the nucleus.

They show polarity due to presence of 2 face.

  1. Cis/convex/forming face

  2. Trans/concave/trans face

Face of cisternae are interconnected but entirely different.

Tubules

Single membrane bound developed by fenestration ( at the tip of cisternae)

Vesicles

May be secretory vesicle, clathrin coated vesicle, golgi vesicle.

Function of golgi body.

  • Modification, packaging and secretion.

  • Help in cell wall formation

  • Formation of acrosome of sperm cell

  • Secretion of mucilage at root tip.

  • Formation of glycolipid and glycoprotein.

Formation of glycolipid is k/a glyosidation.

Formation of glycoprotein is k/a glycosylation.

Lysosome- formed by process of packaging in golgi body.

Size- 0.2 to 0.8 micrometre.