Cells Inside and Out Cell Theory n

Cells Inside and Out

Cell Theory n English scientist Robert Hooke used a crude microscope to look at a slice of cork. n He saw little boxes that reminded him of the small rooms that monks lived in – Cells

Cell Theory n Later the observations of scientists Schleiden, Schwann and Virchow led to what we call the Cell Theory: n All living things are composed of one or more cells n Cells are the basic units of structure and function in organisms n All cells arise from existing cells

Size Chart Atom Molecule Organelle Cell Tissue Organ System Organism Population Community Ecosystem

Cell Size n n Having many small cells is more efficient than having a few large cells Small cells have larger surface to volume ratios than large ones n So, substance exchange is faster in small cells than in large.

Surface to Volume Ratio Example n Surface area Equation on a cube n L 2 X 6 n Volume Equation of a cube n L 2 X H

Magnification n. Light microscope n Visible light passes through object n A Lens magnifies the image n. Magnification n Making an image seem larger than what it is n. Resolution n What measures the clarity of an object n What limits a particular type of scope

Magnification n Electron Microscope n 100, 000 X magnification power n Scanning Electron Microscope (SEM) n Allows for better resolutions on the surface of an object n Shows object in 3 D n Good for observing living organisms

Magnification n Electron Microscopes n Transmission Electron Microscope (TEM) n Observer to sees through cells n allows the observer to see specimen's internal structure

Features Common to All Cells n Cell Membrane n All cells share this outer boundary n This membrane encloses and separates the interior of the cell – the cytoplasm n The cell membrane also regulates what enters and leaves the cell

Features Common to All Cells n Cytoplasm (Cyto= cell, -plasm= formative material) n Everything between plasma membrane and nucleus or nucleoid region. n Cytoskeleton (Cyto= cell, -skeleton= structural framework) n Structure made of microfibers & microtubules within the cytoplasm that suspends the cells structures n Most cells have ribosomes n Cellular Structures on which proteins are made

Prokaryotes n Bacteria Cells n Have no nucleus n n Evolved before eukaryotic cells Structures Common to Prokaryotes n Nucleoid region- where the chromosome is ribosomes- protein synthesis n Cell membrane- “gate keeper” n Cell wall (different than plants)- support n Some have capsules outside wall- resistance to antibiotics n Pili- exchange of genetic info n Flagella- movement n

Prokaryotes

Eukaryotes n Plant and Animal Cells n Cells are more complex than prokaryotic cells n Much like Prokaryotes Eukaryotic Cells n have a cell wall (plants/protists/fungi) n have a plasma membrane n have Cytoplasm n have ribosomes n But within their cytoplasm eukaryotes have n Organelles n Cytosol - fluid in cytoplasm

Major Organelles to know n Cytoskeleton- support & protection n Cell membrane- “gate keeper” controls what enters or leaves the cell n Nucleus- holds the chromosomes, directs cell n Endoplasmic Reticulum- transport & protein formation n Golgi Apparatus- packages things n Lysosomes- hold digestive enzymes, “suicide sac” n Vesicles- storage n Mitochondria- “Power house” respiration, ATP energy n Cell Wall- support, protection n Chloroplasts- photosynthesis, make glucose n Central Vacuole- storage, especially of water n Ribosomes- protein making

Cytoskeleton n Provides interior framework to support cell n Made of network of protein fibers tied to the plasma membrane.

Cytoskeleton n There are three kinds of cytoskeleton fibers n Microfilaments (or Actin Fibers) n Made of protein actin n Works in the shape and movement of a cell n Microtubules n Tiny tubules made up tubulin protein n Highway for transportation of info. from nucleus to parts of the cell n Intermediate Fibers n Rope-like fibers where enzymes and ribosomes anchor in the cell

Cell Membrane n Phospholipid bilayer - barrier separating inside of cell (cytoplasm) from outside n Selectively permeable (penetrable) - controls what enters & leaves cell

Proteins Embedded in the Plasma Membrane n n ** Proteins are macromolecules made of amino acids Some proteins embed in the plasma membrane n Enzymes n Transport Proteins n Receptor Proteins n Must have both polar & non polar ends to embed in the membrane

Nucleus n Nucleus and mitochondria contain genes n Nucleus consists of: n Envelope n Double membrane n Pores let messages in and out n Chromatin n DNA n Protein n Nucleolus n Produces r. RNA n r. RNA with proteins makes up ribosomes

Nucleus

Endoplasmic Reticulum (endo = Inside, plasm = formed material) n Major system of internal membranesmove proteins and other stuff through cell n Is a lipid bilayer with embedded proteins n Makes steroids, lipids n Detoxifies chemicals

Endoplasmic Reticulum (ER) n Rough ER n Has ribosomes embedded so looks “rough” n Processes proteins n Smooth ER n No ribosomes embedded so looks “smooth” n Makes lipids and breaks down toxic chemicals

Golgi Apparatus/Lysosomes n Golgi Apparatus n Flattened pancake like membrane-bound sacs- the packaging distribution center of the cell

Lysosomes/Vesicles Lysosomes (lyso-breaking, -some=body) • Small spherical organelles • hold digestive enzymes Work with Golgi to produce, package and distribute protiens Vesicles • Small bubble-like membrane bound sacs • carry material from ER to Golgi and out of cell Some will become lysosomes

Here’s the Protein Flow

Mitochondria n Harvests energy from organic compound (sugars) to make ATP n ATP: energy “Money” in the cells n Cellular respiration n Most eukaryote cells contain mitochondria n Double membrane n Big bag stuffed in smaller bag n Folds of inner bag = cristae n Space inside inner bag called matrix n Holds enzymes and DNA n This DNA ONLY inherited from mom

Mitochondria

Organelles Common to Plants n n Plants contain all of the organelles now mentioned plus more Organelles Only in Plants (not animals) n Cell Wall n Chloroplast n Central Vacuole

Cell Wall n Surrounds the cell membrane n Made of proteins and carbohydrates n Cellulose - polysaccharide(poly=many, saccharide=sugars) cellulose can NOT be digested by all us, but some can. n Supports and Maintains the shape of a cell n Protects from damage

Chloroplasts n Plant cells contain mitochondria to produce the energy “bucks” (ATP), AND they contain chloroplasts to make the glucose the mitochondria “burns” to make the ATP n Chloroplasts use light energy to convert carbon dioxide and water into sugar, oxygen and energy (ATP) n Also found in algae and some protozoans. n Chloroplasts n have two membranes n have enzymes & DNA

Chloroplasts

Central Vacuole n n n Largest organelle in a plant cell Contains ions (charged atoms), nutrients (macromolecules), and wastes When full, makes cell rigid which enables the plant to stand upright.

Plant Cell

The Endosymbiotic Hypothesis n. Evolution of the Eukaryotic cell – (with mitochondria and chloroplasts) n. Theory: one large prokaryotic cell ingested another which became mitochondria and/or chloroplast in the now eukaryotic cell.

n. Evidence n. Both are similar to bacteria in size and shape n. Both have a double membrane n Outer from being taken into cell n Inner from original bacterial cell n. Contain DNA in loop like bacteria n. Contain ribosomes - make proteins n. RNA in ribosomes like bacterial cells

The Endosymbiotic Theory