The Cell

Living Organisms

• All organisms except Viruses are cellular• Only Two fundamental types

Fundamental Cell Types

• Prokaryotic : Bacteria & Archaea• Eukaryotic : Animals, plants,

protozoa, fungi & algae

• Viruses structure : protein coat + genetic material ( DNA or RNA )

• Virus is not a cell .

Virus

*Viruses structure : protein coat + genetic material ( DNA or RNA )*Virus is not a cell .

• Prokaryotic• Single cell• Size generally small (1-10μm)• Nucleus absent• DNA lies in cytoplasm(circular

molecule ) ( DNA+non-histone protein)

• No membrane bound organelles• Hair like flagella are simple tubes.

Ribosomes, are smaller in size 70 S• Simple internal structure• Cell division by simple binary fisssion

• Eukaryotic• Single or multicellular• Size generally large (10-100μm)• Nucleus present• DNA lies in nucleus. (chromosomes;

DNA +histone +non-histone proteins ) There is membrane bound organelles

• Flagella are complex supported by 9+2 tubes.

• Ribosomes are larger in size 80 S• Complex internal structure• Cell division by mitosis

Cells

Prokaryote Cell Structure

The Bacterial Cell Structure

• The Envelope & Capsule• Pili & Flagella• Cytoplasm & Inclusions

The Envelope & Capsule

• The bacterial envelope can be a three layered structure–Outer Membrane–Cell Wall–Cytoplasmic Membrane

• A capsule may or may not surround the envelope

Pili

• Straight hair like projections made of protein pilins•May be short or several cell

lengths long

The Eukaryotic Animal Cell

The Eukaryotic Plant Cell

Eukarytotic Structures• External structures cilia, flagella• Cell walls, Cell membranes• Cytoplasmic inclusions–Ribosomes–Cytoskeleton–Centrioles & Centrosomes

Eukarytotic Structures

• Nucleus & chromosomes• Endoplasmic Reticulum (rough &

smooth)• Golgi Body• Lysosomes• Mitochondria & Chloroplasts

Nucleus & contents

Mitochondria

Endoplasmic Reticulum (rough & smooth)

Functions Of Cell Organelles

• Nucleus : containing the chromosomes which carry the genetic information in DNA .

• Mitochondria : provide the energy to cell ,generates ATP .

• Riobosomes : sites of protein synthesis .• Endoplasmic reticulum : synthesis of secretary

proteins and carbohydrates.

• Golgi apparatus : transport molecules out of cells and to other organelles .

• Lysosomes : degradation of metabolites and cellular component after cell death .

• Peroxisomes : removal of H2O2 and other oxidizing radicals .

• Chloroplasts ( in plants ) : photosynthesis .• Vacuoles ( in plants ) : degradation and storage

.

Cell

Chemical composition-by weight :• 70% water• 7% small molecules• salts• Lipids• amino acids• nucleotides• 23% macromolecules• Proteins• Polysaccharides• lipids

• The proteins are the most prominent biomolecules in the cell , making up over 50% of the dry weight .

• There is 3000 different kinds of protein molecules ( 20 a.a can be arranged in different sequence to give a huge number of different proteins)

• The second most abundant biomolecules are nucleic acids .• These are followed by carbohydrates & lipids .• All living cells contain approximately the same proportion of

the major classes of biomolecules as in E.Coli .( in human there is about 100.000 different kinds of proteins )

The relative amounts of the major classes of biomolecules in living organisms

Major molecular component

Approxmate No of Molecular species

Percent total weigh Component

1 70 Water

3000 15 Proteins

Nucleic acids

1 1 DNA

1000 6 RNA

50 3 Carbohydrates

40 2 Lipids

500 2 Building-block molecules&intermediates

12 1 Inorganic ions

Example E.Coli