Introduction to Molecular Cell Biology

Unit of LifeUnit of LifeDr. Fridoon Jawad AhmadDr. Fridoon Jawad Ahmad

HEC Foreign ProfessorHEC Foreign ProfessorKing Edward Medical UniversityKing Edward Medical University

Visiting Professor LUMS-SSEVisiting Professor LUMS-SSE

OverviewOverview

Life 

Life is not a random collection of some macromoleulces.

Life is a collection of macromoleulces that can perform unique functions because the are enclosed

in structural acompartment that provides consistency (homeostasis).

All organisms are composed of cells the basic unit of life and all cells come from preexisting cells

Cells are Small 

Cells are small to maintain large surface area to volume ratio.

Larger volume requires a grater

exchange of materials from out

side which is a function of surface

area.

Prokaryotic Cells 

No membrane enclosed internal compartments.

The plasma membrane regulates traffic is a barrier.

Nucleoid region contains DNA, most have cell wall.

Support & Cell shape

Protection From Phagocytes

Special Prokaryotic Cells 

Cyanobacteria Chlorophyll containing have folds of plasma membrane, other have mesosomes (energy).

Some have actin like filaments and other have Flagella made-up of Flagellin.

Eukaryotic Animal Cell

Eukaryotic Plant Cell

How the Function of Organelles was

determined

The Nucleus

Chromatin and Chromosome

Ribosomes 

Free or attached to ER involved in protein synthesis.

Present in Mitochondria & Chloroplasts.

Contain protein and RNA.

RER 

Segregates newly synthesized Proteins.

Chemically modifies proteins (Glycosylation adress)

SER 

Glycogen hydrolysis.

Secreting and detoxifying cells have abundant SER

Cis, Medial & Tarns

Golgi Apparatus

The Golgi apparatus receives materials from the rough ER

and modifies them.

Concentrates sorts and packages proteins and sends

them to other destinations.

Manufactures poly-saccharides for the plant wall.

Lysosomes 

Lysosomes contain many digestive enzymes.

Lysosomes fuse with the phagosomes produced by phagocytosis (autophagy) to form secondary

lysosomes, where engulfed materials are digested.

Undigested materials are secreted from the cell when the secondary lysosome fuses with the plasma

membrane..

Mitochondria 

Breakdown fuel molecules to make ATP.

Some protists have one, liver more than a thousan

and egg a few hundred thousand MT.

Mitochondria and chloroplasts contain their own DNA and ribosomes for making some of their

own proteins.

Endosymbiosis 

The endosymbiosis theory of the evolutionary origin of mitochondria and chloroplasts states that these

organelles originated when larger prokaryotes engulfed, but did not digest, smaller prokaryotes.

Mutual benefits permitted this symbiotic relationship to be maintained, allowing the smaller cells to evolve

into the eukaryotic organelles observed today.

Photosynthesis

Detoxification of O2

Peroxisomes and Glyoxysomes

Peroxisomes collect and degrade toxic

Peroxide H2 O2

byproducts of chemical reactions

Glyoxysomes convert stored lipids into carbohydrates.

Cytoskeleton

Cytoskeleton

Actin (cortical) Stabilizes cell shape.Generates movement local general.

Constriction ring in cell divission (Cytokinesis). Movement of cytoplasam (cytoplasmic strreaming).

IF stabilize cell structure (hold organelles).Stabilize and maintain tissue rigidity (desmosomes).

Lamins in nucleus.Resist tention.

IF in Desmosomes

Microfilaments for Support

Celia are Made of Microtubules

movements 

The movements of cilia and flagella result from the binding of the motor protein dynein to

the microtubules.

Dynein and another motor protein, kinesin, also bind to

microtubules to move organelles through the cell.

ECM in Animals

Bone