Introduction to Molecular Cell Biology Unit of Life Dr. Fridoon Jawad Ahmad HEC Foreign Professor King Edward Medical University Visiting Professor LUMS-SSE

Overview

Life is not a random collection of some macromoleulces.   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 to maintain large surface area to volume ratio.   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.   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

Plasma Membrane   The PM is composed of a phospholipid bilayer, with the hydrophilic “heads” of the lipids facing the cell’s aqueous interior on one side of the membrane and the extracellular environment on the other

Plasma Membrane constant internal environment   constant internal environment selectively permeable barrier communicating with adjacent cells and receiving extracellular signals binding and adhering to adjacent cells

The Nucleus The nucleus is the site of DNA duplication.   The nucleus is the site of DNA duplication. The nucleus is the site of genetic control of the cell’s activities. A region within the nucleus, the nucleolus, begins the assembly of ribosomes from specific proteins and RNA.

The Nucleus 2 membranes

Chromatin and Chromosome

Ribosomes Free or attached to ER involved in protein synthesis.   Free or attached to ER involved in protein synthesis. Present in Mitochondria & Chloroplasts. Contain protein and RNA.

RER Segregates newly synthesized Proteins.   Segregates newly synthesized Proteins. Chemically modifies proteins (Glycosylation adress)

Secreting and detoxifying cells have abundant SER   Glycogen hydrolysis. Secreting and detoxifying cells have abundant SER Cis, Medial & Tarns

Manufactures poly-saccharides for the plant wall. 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 contain many digestive enzymes.   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..

Breakdown fuel molecules to make ATP. 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

Cytoskeleton Microfilaments: Cell shape (change), cellular motion, contraction, cytoplasmic streaming & cytokinesis Intermediate filaments: Rope like stabilize cell shape, resist tensile forces, cell adhesion & nuclear lamina. Microtubules: Long hollow dynamic, move chromosomes & transport.

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

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.

Celia are Made of Microtubules

ECM in Animals Bone