Two main types of cells §Prokaryotic – no nucleus, no membrane- bound organelles §Eukaryotic – has a nucleus, has membrane- bound organelles

An Overview of Cell Structure §All cells have three components l Cell/plasma membrane l Genetic material l Cytoplasm/cytosol

The Plasma Membrane

The Plasma Membrane Surrounds the Cell § Phospholipid bilayer contains embedded proteins

The Plasma Membrane Surrounds the Cell §Proteins enable cell to interact with environment §Transport proteins facilitate passage across membrane §Receptors induce cell changes with contact by molecules §Markers provide cell identity

The Central Portion of the Cell Contains the Genetic Material

Genetic material in prokaryotes §Single, circular molecule of DNA §Is concentrated in the center, not membrane bound

Genetic material in eukaryotes §Contained within the nucleus §Surrounded by two membranes

The Cytoplasm Comprises the Rest of the Cell's Interior §Cytoplasm is a semifluid matrix §Contains chemicals to carry out growth and reproduction

The Cell Theory

Robert Hooke § First cells seen with invention of microscope in 1665 § Observed honeycomb of empty compartments in cork

Antonie Van Leeuwenhoek § First to observe living cells

Matthias Schleiden §Observed plant tissues

Theodor Schwann §Observed animal tissues

Modern principles of cell theory §All organisms composed of one or more cells §Cell is smallest living functional unit §Cells arise only from the division of other cells

The Structure of Simple Cells: Bacteria (Prokaryotic)

A. Simplest Cellular Organisms §Great diversity §Similar organization, small size §May adhere in masses, but are fundamentally separate from one another

B. Strong Cell Walls §Carbohydrate matrix cross linked with peptide units §Gram positive, thick cell wall, retains stain, purple §Gram negative, thinner cell wall, releases stain, red or pink

The Prokaryotic Cell

C. Simple Interior Organization §1. Lack internal compartmentalization l a. Cell strength due to cell wall l b. Reactions not separated, single metabolic unit §2. Lack membrane-bound organelles l less efficient metabolic functions

The Structure of Eukaryotic Cells: An Overview §Plants, animals, fungi and protists are all eukaryotic §Eukaryotes are more complex than Prokaryotes

Eukaryotes Are More Complex Than Prokaryotes §Hallmark is compartmentalization l Organelles are separated from one another by membranes

The Animal Cell

Eukaryotes possess internal membrane-bound organelles §Golgi complex and lysosomes created by folding endoplasmic reticulum §Mitochondria and chloroplasts associated with cellular energy

Eukaryotes possess internal membrane-bound organelles (cont). §Central vacuole in plants stores protein and wastes §Vesicles in animals store and transport many materials §Nucleus contains chromosomes made of DNA

The Plant Cell

Plant Cells §Cytoskeleton-An internal scaffold of proteins §Cell walls-Cellulose fibers embedded with polysaccharides and proteins

The Endoplasmic Reticulum §Thin membranes not visible in light microscope §Divide interior into compartments §Lipid bilayer with embedded proteins §Abbreviated ER

Endoplasmic Reticulum (ER) Rough ER Smooth ER

Rough ER: Manufacturer of Proteins for Export §Ribosomes assist in the manufacturing of proteins l They contain groups of proteins and RNA l Translation of RNA into proteins

Smooth ER: Organizer of Internal Activities §Lack ribosomes §Contain embedded enzymes §Associated with detoxification, carbohydrate and lipid synthesis

The Nucleus: Information Center for the Cell §Spherical appearance in most cells §It is the largest organelle, readily visible §Centrally located, positioned by filaments

The Nucleus

The Nuclear Envelope §Double layer of membranes, outer membrane continuous with ER §Membranes pinched together at nuclear pores l Embedded with proteins, serve as molecular channels l Restrict passage of molecules to proteins and RNA

Proteins are made on the Ribosomes §On the ribosome, RNA is made into proteins §Proteins are necessary for the function of life l Ribosomes are the worker bees of the cell

The Golgi Complex: The Delivery System of the Cell §Golgi Bodies l Individual, flattened stacks of membranes l Collectively called the Golgi complex l Function in Molecule Collection, Packaging, Distribution l The FedEx of the cell

The Golgi Complex

Lysosomes: §Producers of digestive enzymes for the cell §Membrane bound organelles containing digestive enzymes l Digest worn-out cell components and recycle material into new structures §Digest pathogens engulfed by white blood cells l The garbage truck of the cell §Participate in selective cell annihilation

Lysosomes

Centrioles: Microtubular Assembly Plants §Present in animal and protist cells §Occur in pairs at right angles near nuclear envelope, forms the centrosome §Associated with assembly and organization of microtubules l Help move DNA during Mitosis

Centrioles

Mitochondria: The Cell's Chemical Power Plant §Occur in all organisms §Bounded by double membrane l a. Outer membrane is smooth l b. Inner membrane is folded into contiguous layers called cristae §Mitochondria possesses own DNA §Mitochondria are capable of replication

Mitochondria

Chloroplasts: Where Photosynthesis Takes Place §Occur in photosynthetic organisms, plants and algae §Bounded by double membrane §Internal membranes form disk-shaped thylakoids (look like pancakes) §Photosynthetic pigments on thylakoid surface §Possess own DNA, can reproduce

Chloroplast

The Cytoskeleton §Interior Framework of the Cell

Flagella and Cilia §Motility for the Cell

Flagella vs. Cilia

Cilia § Have functions other than locomotion §Pass fluids over tissue surface §Bend in response to sound waves l In your aural canal

ENDOSYMBIONT HYPOTHESIS §Mitochondria and chloroplasts originally were independent prokaryotic cells (with their own DNA). §Were engulfed by larger cells, eventually became symbiotic with each other.