Cell the unit of life

Who coined the word cell

Robert hook in 1665 when he was observing very thin slices of bottle cork

Who discovered Live Cell?

Anton Von Leeuwonhook in 1674

Who discovered Nucleus

Robert Brown

1831

Matthias Schleiden

1838

• German Botanist 

• Every structural part of the plant is made up of cell 

  • Cells form tissue of the plant 

Theodore Schwann 

• German Zoologist 

• Noticed a very thin outer membrane

• presence of cell wall is unique feature of plant cells 

• Proposed hypothesis that the bodies of animals and plants are composed of cells and product of cells. 

Who explained how new cells were formed and where did it help 

Rudolf Virchow in 1855 

• explained that cells divided and new cells are formed from pre existing cells 

• Omnis Cellula-e Celula

• Modified the hypothesis of Schleiden and Schwann

• Gave cell theory its final shape

Cell Theory

By Matthias Schielden and Theodore Schwann

1. All living organism are composed of cells and products of cells 

2. All cells arise from pre-existing cells 

Differences between Prokaryotes and Eukaryoutes

Prokaryotes	Eukaryote
Naked Genetic Material - Nucleoid	Genetic Material enclosed in a nuclear membrane
Absent Nuclear Membrane	Present Nuclear Membrane
Single Circular DNA	Many Types of DNA
No membrane Bound Organells	Present Membrane Bound organells
Only Unicellular	Both Unicellular and Multicellular
Smaller	Larger
Multiply Faster	Multiply Slower

Similarities Between Prokaryotes And eukaryotes 

1. Cytoplasm 

2. Plasma Membrane 

3. Ribosomes are present with different size and density

4. Both and genetic Material

Cell envelope

Three Tightly bound layers

1. Outermost: Glycocalyx 

2. Middlemost: Cell wall 

3. Innermost: Plasma membrane 

Glycocalyx

Differs in composition and thickness among bacteria

1. Loose sheath/ layer called slime layers which adheres to cells 

2. Thick tough capsule providing protection 

Cell wall

• Made of peptidoglycans

• Rigid, provides shape

• Prevents bursting of cell

• Prevents collapsing of cell

Plasma Membrane

• Made of phospholipid Bilayer 

  • Seletively permeable 

How can we classify bacteria into two groups? How do we find the differences in the Cell wall? Who discovered it?

On the basis of difference in cell envelope

1. By staining the cell wall

2. Gram positive: Takes up the stain

   1. a thicker cell wall 

3. Gram negative: Doesnt take up the stain and has to be counterstained.

   • A thinner cell wall 

Discovred by Hans christian Gram 

Mesosomes

Defi: Invaginations of the cell membrane or Infoldings of the cell membrane

They are an extension of plasma membrane

Types: Vesicle [oval], Tubules [tube like], and lamellae  [layers] 

Chromatophors: Store pigment and seen in cynobacteria

Function: 

1. Cell wall formation 

2. DNA replication and distribution to daughter cells 

3. Cellular Respiration [ Due to embedded enzymes] 

4. Secretion processes 

5. Increase surface area, increase enzymatic action

Inclusion Bodies

Store Nutrients

Types:

1. Phosphate granules - store phosphate 

2. Cynophycean granules- Store Nitrogen 

3. Glycgen granules - store glycogen [ stored form of glucose] 

Non membrane bound 

Genome

Entire genetic makeup of an organism

Genes 

Segments on DNA giving information on synthesis of certain protein

Genotype

Gives all physical character of the organism known as phenotype of an organism 

Plasmids

Extra genomic DNA

Seen somtimes

Provides and unique phenotypic character to the organism

ex. Antibiotic Resistance Gene

Function: Used in gentic engenierring 

Monitor bacterial transformation with foreign DNA 

Ribosomes 

Scientist: George Palade

Year: 1953

Non membrane bound organells

Seen in prokaryotes and Eukaryotes 

Size: 15 Nanometers to 20 Nanometers 

Prokaryotes

• Two Subunits:

  • Smaller - 30S 

  • Larger - 50S 

• One Unit- 70S

Made oF rRNA + Proteins 

‘S’ : Svedberg unit 

• Sedimentation Coefficient

• It is an indirect measurement of size and density of ribosomes

• Condition required to Sediment on Ribosomes

Eukaryotes:

• Two Subunit:

  • Smaller- 40S

  • Larger- 60S

• One Unit- 80S

Polyribosmes or Polysomes

When many ribosmes are attached to 1 mRNA [Messenger RNA]

Function: Carrys a message, helps in translation of protein, a step in protein synthesis

Gas Vacuoles 

• Non membrane bound 

• Spaces in cytoplasm 

• Air filled 

• Provide buoyancy [ the ability to float ] to capture sunlight

• seen in photosynthetic and aquatic bacteria and purple and green bacteria

Cell Appendages

Outgrowths of the cell surface

1. Flagella [ only motile one]

2. Pili 

3. Fimbria 

Flagella

Protein: Flagellin

Different in prokaryote and eukaryote

3 parts : Basal Body, Hook, Filament [longest] 

Arrangement: Any 

Help to move. 

Pili

Protein: Pilin

Small, tube like outgrowth from cell curface 

Function: Attach to other bacteria 

ex. Transfer of DNA 

Fimbriae

Small bristle like outgrowths

Function: Adherence to host cells and rocky surfaces in streams 

Plasma Membrane

• Basic Defination

• Componets

Defi: Boundary seen in all living cells between intracellular compartments and extracellular compartments 

Encloses the protoplasm [ cytoplasm + nucleus] 

Cytosol- Only cytoplasm, no cell organells 

Seletively permeable

Reason: Depends on addition of proteins 

Components: 

1. Lipids : more abundant 

2. Proteins : more, less than lipids 

3. Carbohydrate : Less abundant 

4. Choslestrol : Less abundant 

Plasma membrane 

• Molecule and structure 

A phospholipid Bilayer: 

An amphiatic molecule [ two ends] 

• one polar end and one non polar end

Part: Head and Two tails

• Head = glycerol + phosphate 

  • Polar and hydrophilic.

• Tails = fatty acids/ lipids = saturated hydrocarbon

  • Non-polar and Hydrophobic

Phospholipid Bilayer-

• Heads face the ECF and ICF 

• Tails face eachother. 

Allows stability

• Single membrane : 1 phospholipid bilayer and 2 phospholipid layer 

• Double membrane : 2 phospholipid bilayer and 4 phospholipd layer 

Plasma membrane

• Proteins and its type 

Proteins : On the basis of ease of extraction [ easily removable] 

• Integral proteins 

  • Transmembrane proteins 

  • Partially burried proteins 

• Peripheral proteins 

Carbohydrate

They are seen around the ECF

Attached to either a

• Lipid- glycolipid 

• protein- glycoprotein 

Act as cell to cell markers 

Help in cell to cell recognition [identity tag] in blood groups 

Help to distinguish Self cells from foreign cells in immune system, helping them kill it. 

Cholestrol

A type of lipid seen randomly inbetween the tails of the phospholipid molecule.

it regulates the fluidity of the cell membrame

it depends upon body temperature

• Body temperature increase

  • fluidity increase 

  • cholestrol is added inbetween the tails 

  • It decreases the fluidity 

• Body temperature decreases 

  • Fluidity decreases 

  • Cholestrol is removed from inbetween the tail 

  • It increases the fluidiy 

Transmembrane proteins, its other name and what can and cannot pass through it

Other name : transporter protein, fully buried protein.

Substances that do not cross the phospholipid bilayer	Substances that do cross the phospholipid bilayer
Water, water soluble substances	Lipids, fatty acids, lipid soulable substances oil
Charged ions (Na + K+ etc_	Neutral particles
Polar molecules and compounds	Non polar molecules and compounds
Larger molecules	Smaller molecules.

Transport across cell membrane types

Passive(Simple diffusion and faciliateted transport) and Active

Passive transport 

Types : Simple Diffusion and Faciliated transport

Movement of substances from higher concentration to lower concentration

Along the concentration gradient

Downhill transport

Requires no ATP (energy)

Simple Diffusion

Movement of substance from higher concentration to Lower concentration with no help of transport proteins

Faciliated Transport or Faciliated Diffusion

Movement of substance from higher concentration to lower concentration with the help of transport proteins

ECF: High concentration of Na+ and Low concentration of K+
ICF: High concentration of K+ and Low concentration of Na+

Passive transport of Na + = ECF to ICF 

Passive transport of K+ = ICF to ECF 

Types: Channel proteins and Carrier proteins 

Channel proteins

Specific channels
Movement of substances from higher concentration to lower concentration

Along the concentration gradient

Downhill transport

Requires no ATP (energy)

It can be gated and open 

If gated, then it only opens when necessary [K+] 

if open, then it always remains open [H20] 

Carrier proteins 

Movement of substances from higher concentration to lower concentration

No ATP required 
It goes through a conformational change 
They have a specific binding site (glucuse) 

• Once glucose binds in ECF

• It changes shape

• Drops into ICF 

Active Transport

Movement of substances from Lowerconcentration to higher concentration

againstb the concentration gradient

uphill transport

Requires ATP (energy)

It pumps 3 Na+ ions from the ICF to ECF 

It pumps 2 K+ ions from the ECF to ICF 

• ICF : 3 Na + Binds to protein, K+ remains empty

• Undergoes conformational change 

• ECF: 3 Na+ released into ECF. 2 K+ binds to protein 

• Undergoes Confomational change 

• ICF: 2 K+ Ions released and One ATP used. 

Endomembrane System

1. Endoplasmic reticulum 

2. Golgi apparatus 

3. Vacoules 

4. Lysosomes

All single membrane bound

Reason: Are in coordinated movement to eachothes

Endoplasmic Reticulum

Defi: A network / reticulum of tiny tubular structure

Two parts of Intracellualr Fluid (ICF) 

1. Inside ER: luminal 

2. Outside ER: Extraluminal compartment (cytoplasm) 

Two Types of ER: 
 1. Rough Endoplasmic reticulum: 

Ribosomes are studded on its surface.

help in protein synthesis and secretion. 

2. Smooth endoplasmic reticulum:
   Lipid Synthesis. Extensive and continous with outer membrane of nucleus. 

   1. Animal cells: Lipid like steriodal hormones are synthesises

Golgi Apparatus

Scientist: Camillo Golgi

Year: 1898

Size: 0.5 micronmeter to 1 micronmeter diameter.

Cisternae [ disk, flat shaped] are stacked like plates ontop of eachother. 

1. Cisface[forming face ]faces the nucles in a convex 

2. The transface [ maturing face ] faces away from the nucles in a concave 

Fucntion: Packaging materials, main site of synthesis of glycolipid and glycoproteins 

Materials are packaged in forms of Vesicles. 

They fuse with the Cisface and move towards transface

A number of ribosomes are modified in cisface and leave the transface. 

Lysosomes

Suicide bags

Membrane bound 

Formed by golgi apparatus

Contain acidic hydrolytic enzume [hydrolase] 

• help in breakdown of biomolecules by digestion

• Carbohydrate : Carbohydrases

• Lipids: Lipase 

• Protein: Proteases 

• Nuclic acid: Nucleases

When lysocome bursts, it dosent kill the cell, it instead become neutralised due to alkaline cytoplasm

Vacuoles

Contain cell sap, water, excretary products not useful for the cell.

Bound by a single membrane : Tonoplast

Occupy 90% space in plant cells.

Tonoplast: Movement of substance from lower concentration to higher concentration. 

Concentration is higher in vacuole than cytoplasm. 

Amoeba: Contractile vacuoles: Osmoreguation and excretoon 
Protits: Food vacuoles for engulfing food

Mitochondria

The power house of the cell

Double membrane bound

Function: Site of aerobic respiration / cellular respiration

Self autonomous:

• It generate ATP by using glucose

• Synthesis of proteins

  • due to presence of 70S ribosome and few RNA and Single circular DNA 

• Self duplicate: Divide by its own

  • by binary fission

  • creates the protein needed for binary fission

More Mitochondria : More energy : Muscle and neurons

Less Mitochondria: Less Energy: Epithelial tissue 

Diamter: 0.2 to 1 micronmeter 

Length: 1 to 4.1 micronmeter 

Outer membrane: more permeable: more proteins present

Outer compartment / inter membrane space: aqueous 

Inner membrane: infoldings know as cristea: increase surface are for respiration 

• less proteins, more enzymes

Inner compartment : Homogenous aqueous matrix 

Plastids

Double membrane bound organells

Present: Plants, euglena, chlorella, dinoflagellets, chlmydomonas.
Types:

1. Chloroplast 

2. Chromoplast 

3. Leucoplast 
   

Chromatophor

Colour: Red, yellow, orange

Pigement: Caretenoid [carotene] and Xanthophylls.

Functions: Imparts color of flower

Leucoplast

Colour: No colour

Pigment: Absent

Function: Storage of nutrients

Types:

1. Amyloplasts: Stores starch

2. Elaioplasts: Store fat and oil 

3. Aleuroplasts: Stores protien 

Chloroplast

Colour: Green

Pigment: Chlorophyll, cartenoid

width: 2 to 4 micronmeter

Length:  5 to 10 micronmeter

Number: Varies

• Chlymydomonas: 1

• green Algae/mesophyll cell: 20 to 40 %

Double membrane:

• Outer membrane: more permeable

• Inner membrane: less permeable:

• Inner compartment : contain stroma [like the cytoplasm of cell] 

Thylakoloid: A single flattened plate of single membrane.

• lumen of thylakoloid: Chlorophyll 

Granum: Stack of Thylakoloid 

Stoma lamellae: Tubulae that Connects the thylakoloid of chloroplast 

Self autonomous:

• Contains Ribosome [70S], DNA molecules, single circular DNA 

• Self Replicate

Cell wall

Rigid and non living 

Plants Cells:

1. Cellulose

2. Hemi-Cellulose 

3. Pectin 

4. Proteins 

Algal Cell: 

1. Celluslose 

2. Galantans 

3. Mannans 

4. Calcium Carbonate 

Fuction: Shape, protects from mechanical damage and infections, cell to cell interactions, barrier to useless molecules. 

Components: 

1. Middle Lamellae: Acts like a glue for two cells.      Made up of Calcium pectate salts 

2. Primary Cell wall: Secreted when cell is young.  outside the Plasma membrane and connects the cells with middle lamellae

3. Secondary cell wall: Secreted when cell is old. For strength. Its made of suberin and lignin.

4. Plasmodesmata: Cytoplasmic connection with two cells

Cytoskeleton

Defi: Network of filamentous proteins

Types:

• Microtubules [ forms highways and spindle fiber] 

• Intermediate filaments 

• Microfilaments 

Function: 

1. Hold all organells, provide support. 

2. Help in motility of the vesicles and cells by cilia and flagella 

3. Shape to cell.

Centrosome

Animal cell: Present

Plant cell: Absent 

Non membrane bound. 

Centrioles: Two rod shaped structure perpendicular to eachother 

• surrounded by an amophous substance [powder like] and call it pericentriolar

1 centrosome 2 centrioles

Centrioles give rise to Basal body and microtubules

Basal body givess rise to cilia and flagella

Microtubules are made of protein called Tubulin

Structure of Centriole

Arrangement of microtubules : 9 + 0

9: Peripheral microtubes

0: Hub

Componenets : 

1. Peripheral tubules :                                              9 evenly place peripheral fibrils made of tublin proteins, each a triplet. 

2. 9 peripheral tubules : 27 microtubules 

3. Radial spoke: connect the peripheral triplets to the hub

4. Linker protein : Connects one peripheral tube to another.

5. Central hub: protenacious

Name: Cartwheel appereance

Structure of Cilia and Flagella

Arrangment: 9 + 2 

9: peripheral tubes 

2: Proteinaceous Central hub 

Componenets : 

1. Peripheral tubules :                                              9 evenly place peripheral fibrils made of tublin proteins, each a doublet. 

2. 9 peripheral tubules : 18 microtubules 

3. Radial spoke: connect the peripheral triplets to the hub

4. Linker protein : Connects one peripheral tube to another.

5. Plasma membrane: Surrounds all the above componets and are known as core or axoneme

Basal Body arrangement: 9 + 0 

Differnece of Cilia and Flagella

Cillia	Flagella
Shorter	Longer
Hair like	Tail like
Oar like coordinated movement	Whiplash like movement
Ex. ciliated epithelim	ex. Human sperm

Nucelus

Discovered by robert brown in 1831

Double membrane bound

Perinucleur space: The gap between the outer membrane and inner membrane of the nucler membrane 

• size: 10 to 50 nanometer 

Nucleur pores: Fusion of outer membrane and inner membrane 

• Allowing Biodirectional movement of RNA, Proteins and ribosomes 

Nucleoplasm: Matrix inside the nucleus 

• Nucleolus

• Chromatin Fibers 

Nucleolus:

• Non membrane bound

• Dense and continous with nucleoplasm 

• Manufactures subunit of ribosomes [60S and 40S] 

• More Nucleolus and More protein synthesis More ribosome

Chromatin fibers 

Chromatin Fibers: Discovered by flemming

Genetic Fibers, Nucleoprotein Fibers

Nucleic protein + Acid

• DNA 

• RNA 

• Histone proteins [ alkaline basic protein]

• Non histone proteins 

Chromosomes and Diving cells 

Total Number: 46

Total Pairs: 23

Type: Autosomes and Sex chromosomes

Autosomes: 44 chromosomes and 22 pair 

• They are extreamly similar with a small difference like in eye colour, its eyes but differnce is colour, 

Sex chromosomes: Show Sex linked character 

• X and Y 

• XX: Female 

• XY: Male 

DNA: 2 meter long broken down into 46 pieces 

1. Replicate DNA [matter is increased] 

2. Shortening and Condensing of the replicated DNA by winding it around histone proteins to fit inside nucleus

3. Chromosome becomes visisble in a diving nucleus 

4. Structure: 

   1. Centromere [primary constrictions] with a kinetochore surrounding it 

   2. 2 Chromatid in 1 chromosome and 1 centromere 

   3. 4 chromatid, 2 chromosome and 2 centromere 

Position of Centromere

1. Metacentric: Middle centromere, equal arms of chromosome

2. Subcentric: Centromere slightly away from the middle, hence unequal arms [one shorter and one longer arm]

3. Acrocentric: Centromere situated closer to its end, forming one extreamly short arm and extreamely long arm

4. Telocentric: Centromere to the terminal

Satalite: Non staining secondary constriction at a constant location

Microbodies 

very small Vesicles 

Single membrane bound 

Contains enzyme for various metabolic reactions

Found in plants and animal

1. Peroxisome: 

   • Covert toxic hydrogen peroxide [ H2O2] to water [H2O]  

2. Glyoxysoms and Glyoxysomes:

   • Seen only in plants

   • Fat metabolism and Storage

Interphase

Resting cells: Non Diving cells

This stage is known as interphase 

• DNA and RNA is of

  • Extended form

  • tangled,

  • loosely wound around histone proteins

  • Indistinct 

Dividing Cells

•  DNA and RNA is of

• Short form

• condensed

• tightly double wounded around histone proteins

• distinct