The Cell Introduction to cell structure and function

The Microscope Invented by Galileo Galilei Cells first visualized by Robert Hooke Antoni von Leeuwenhoek Modern microscopy –Bright field –Dark field –Phase contrast –Electron

Cell Theory All living organisms are composed of one or more cells All cells come from pre existing cells The cell is the most fundamental unit of life Cells contain hereditary material Schleiden and Schwann

Cell size Limited due to surface to volume ratio Nutrients must enter across the surface Nutrients must support the volume within the cell Flat cells vs. round cells

Features common to all cells DNA as hereditary material Plasma membrane Cytoplasm Ribosomes Metabolic capacity All categories of macromolecules

Categories of Cells Two main categories Based on presence or absence of a membrane bound nucleus Prokaryotic cells Eukaryotic cells

Prokaryotic Cells No membrane bound nucleus Single molecule of circular DNA May have plasmids Nucleoid region Small size (.2-50u) Cell wall of peptidoglycan 70S ribosomes Flagella, if present, simple protein Pili Capsule Bacteria Archea

Eukaryotic Cells Membrane bound nucleus Membrane bound organelles Size- larger(10-100u) No peptidoglycan Cell walls- cellulose or chitin if present 80S ribosomes Extra cellular matrix More complex Protista Fungi Plantae Animalia

Typical Organelles Nucleus Endomembrane System –Nuclear envelope –Endoplasmic reticulum –Golgi –Vessicles Mitochondria Chloroplasts Cytoskeleton

Nucleus Nuclear envelope Pores Nucleolus Chromatin Nucleoplasm

Nucleus

Endomembrane System- Endoplasmic Reticulum Contiguous with the outer nuclear membrane Tubes of phospholipid bilayers Rough ER –Studded with ribosomes –Protein synthesis Smooth ER –Lipid and carbohydrate synthesis –Detoxification of poisons

Endomembrane System- Golgi Stack of membranes Performs final modifications to macromolecules Packages into vesicles Sends to final destination Phosphate address “Pack and Send”

Endomembrane System- Vesicles Membrane bound sacs Package and sequester contents Transport Lysosomes –Digestion –Recycling –Apoptosis Peroxisomes –Detoxify free radicals –Superoxide dismutase –Catalase –Break down lipids

Mitochondria Double membrane Inner membrane infolded Contains DNA Replicates independently Evolved from bacterium Main site for ATP production Krebs cycle, electron transport chain Found in all eukaryotic cells (almost)

Chloroplast Double membrane structure Internal membrane stacks- Thylakoid Site for photosynthesis Contains DNA Evolved from bacterium Found only in photosynthetic eukaryotes (plants)

Cytoskeleton Network of protein fibers –Microtubules –Intermediate filaments –Microfilaments –Molecular motors Control cell shape and movement

Microtubules

Intermediate Filaments

Microfilament

Molecular Motors Move organelles along micro tubules “Walk” Dynein Kinesin FlNn2dZchttp:// FlNn2dZc

Specialized Cytoskeletal Structures Cilia Flagella arrangement of microtubules Basal body Centriole arrangement of microtubules

Flagella and Cilia

Centriole and Basal Body

Comparison of Plant and Animal Cells

Plant and Animal Cells Animal Specific Features Lysosomes Centrioles Plant Specific Features Cell Wall- cellulose Chloroplasts Central vacuole Tonoplast Plasmodesmata

Plasma Membrane Cell perimeter Phospholipid bilayer Embedded proteins Fluid mosaic model Regulates transport of molecules I/O of cell Participates in cell communication

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