1.
Introduction to Cell Biology:
• Concept of Evolution:
• Evolution explains how living organisms develop from earlier forms over time through
changes in heritable traits.
• Key contributions:
o Jean Baptiste Lamarck (1801): Proposed that traits acquired due to
environmental needs are passed on.
o Charles Darwin (1859): Introduced "survival of the fittest," where favorable
mutations increase chances of survival and reproduction.
2. Cell Theory:
• Formulated by Schleiden and Schwann (1838):
• Main Points:
o All living organisms are composed of cells.
o The cell is the basic unit of life, performing all vital functions.
o New cells arise only from the division of pre-existing cells.
3. Prokaryotic and Eukaryotic Cells:
• Prokaryotes:
• Characteristics:
o DNA is located in a nucleoid (no true nucleus).
o Lack membrane-bound organelles.
o Have a cell wall made of peptidoglycan.
o Ribosomes in the cytoplasm synthesize proteins.
o Example: Bacteria.
• Eukaryotes:
• Characteristics:
o Have a true nucleus enclosed in a nuclear membrane.
o Contain membrane-bound organelles like mitochondria, ER, and Golgi apparatus.
o Found in plants, animals, fungi, and protists.
4. Cell Organelles and Their Functions:
• Plasma Membrane:
• Made of a phospholipid bilayer with embedded proteins.
• Controls what enters and exits the cell.
• Acts as a living, protective barrier.
• Cytoplasm:
• Jelly-like substance that supports organelles and facilitates chemical reactions.
• Nucleus:
• Enclosed by a nuclear envelope.
• Houses DNA in chromosomes.
• Directs all cellular activities and genetic information.
• Nucleolus:
• Located inside the nucleus.
• Produces ribosomes, which are critical for protein synthesis.
• Cytoskeleton:
• Provides structural support and helps move organelles within the cell.
• Components:
o Microtubules: Tube-like structures made of tubulin.
o Microfilaments: Thread-like structures made of actin.
• Centrioles (Animal cells only):
• Assist in cell division by organizing the mitotic spindle.
• Mitochondria:
• Known as the "powerhouse" of the cell.
• Produces ATP through cellular respiration.
• Contains its own DNA and is inherited maternally.
• Endoplasmic Reticulum (ER):
• Rough ER:
o Studded with ribosomes.
o Synthesizes proteins for secretion or membrane integration.
• Smooth ER:
o Lacks ribosomes.
o Synthesizes lipids, detoxifies chemicals, and regulates calcium.
• Ribosomes:
• Made of proteins and rRNA.
• Sites for protein synthesis.
• Golgi Apparatus:
• Modifies, sorts, and packages proteins from the ER.
• Ships materials within or out of the cell.
• Lysosomes:
• Contain enzymes to digest cellular waste and recycle components.
• Play a role in cell death (autolysis).
• Vacuoles:
• Storage compartments for water, nutrients, and waste.
• Large central vacuole in plant cells maintains structure and stores cell sap.
• Chloroplasts (Plants only):
• Perform photosynthesis using sunlight to produce glucose.
• Contain thylakoid stacks (grana) and their own DNA.
5. Cell Functions:
• Key Functions:
• Metabolism: Chemical reactions that sustain life.
• Respiration: Energy production through the breakdown of glucose.
• Reproduction:
o Mitosis: Cellular replication for growth and repair.
o Meiosis: Produces gametes for sexual reproduction.
6. Whittaker’s Five Kingdom Classification:
• Five Kingdoms:
• Prokaryotae/Monera: Unicellular, prokaryotic organisms (e.g., bacteria).
• Protista: Eukaryotic, mostly unicellular organisms (e.g., algae).
• Fungi: Eukaryotic, decomposers with a cell wall made of chitin.
• Plantae: Eukaryotic, autotrophic organisms performing photosynthesis.
• Animalia: Eukaryotic, heterotrophic organisms without cell walls.
