Bell Ringer 12/1/11 What is the person on the left looking through? What is the person on the right looking through What point is this cartoon making? http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html Get ready for notes!

The Story of Cells

What are cells? The Building Blocks of Life The cell is the smallest structural unit capable of performing life functions.

Cell Trivia The average human being is composed of around 100 Trillion individual cells!!! The egg yolk from an ostrich egg is the largest cell. They are about a half foot long. It would take as many as 50 cells to cover the area of a dot on the letter “i”

Discovery of Cells 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork (bark of tree) He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi

The Microscope! 1673- Anton von Leuwenhoek, invented the microscope and observed pond scum and discovered single celled organisms He called them “animalcules” He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants

Where does life come from? Old Theory - Spontaneous Generation Life spontaneously happens: Life comes from non-life Examples: Mice from cloth sacks and grains. Maggots from rotting meat. REALLY?

Where does life come from? Much doubt existed around Spontaneous Generation Conclusively disproved by Louis Pasteur Ummm, I don’t think so!!! ? = +

Where does life come from? 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells. Biogenesis – Life can only be formed from existing life.

The Compound Light Microscope (review) Lenses Light You’ve used it!! Up to x1500

Our Microscope…

The Electron Microscope (review) Biggest magnification (X 2,000,000) 2 types (SEM and TEM)

The Cell Theory 1. All organisms are composed of one or more cells. 2. The Cell is the smallest working unit of living things. 3. All cells come from pre-existing cells through cell division.

Examples of Cells Amoeba Plants Bacteria Red Blood Cell Nerve Cell

Two Types of Cells Prokaryotic Eukeryotic REMEMBER US

Prokaryotic Cells “Old School” Do not have a membrane-bound nucleus or organelles Few internal structures (organelles) Usually one-celled organisms like bacteria Smaller in size (1-10 um)

Eukaryotic Cells “New School” They do contain a membrane-bound nucleus and organelles and are more complex. May be unicellular or multicellular Larger in size (10-100um) Animal Plant

Cellular Organization Copy Colonies = group of genetically identical cells living together (bacteria), can live independantly Multicelluarity = groups of cells with specific roles in an organism Tissues  Organ  Organ System Volvox Pediastrum

Why are cells so small? Surface area-to volume ratio: small cells more efficient Small size = more surface area More surface area = easier transport of nutrients, oxygen, waste Pg. 73, Figure 4-5

DIFFUSION Movement of molecules from an area of higher concentration to an area of lower concentration 1 2 3 4

How do things actually get in and out of the cell? Through diffusion and osmosis Cell membrane and membrane structures act as the gatekeeper

How does diffusion occur? Passive Transport = doesn’t require energy Concentration Gradient = difference in concentration across a distance Equilibrium = concentration of molecules will be the same throughout the space Even at equilibrium molecules are still moving around [K] = concentration

Simple Diffusion = diffusion across membranes, only certain molecules are allowed across through pores http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

OSMOSIS Diffusion of water from high concentration to low concentration Moves mostly through passive transport Water is always moving in and out of your cells

Which direction does the H2O move? If the solution is… Hypotonic Means [K] of solutes outside of cell is lower than [K] of solutes in cytosol) water moves into the cell Cell will swell (get larger) Think hypo…o’s are round and chubby, like a plump little cell

If the solution is… Hypertonic [K] of solutes outside of cell is higher than [K] of solutes in cytosol Water moves out of the cell Cell shrinks and shrivels up

If the solution is… Isotonic [K] of solutes inside & outside cell are = Water moves in & out at equal rates

 HOW CELLS DEAL W/ OSMOSIS What happens if you live in a hypotonic environment? Get rid of extra water entering cells, contractile vacuole Get rid of extra solutes so less water comes into cell

Turgor Pressure = pressure of water against cell wall, occurs in hypotonic environment Plasmolysis = water leaves cell & cell shrinks away from cell wall, occurs in hypertonic environment

Cytolysis = bursting of cells , in a hypotonic environment too much water can move into cell

Organelles -Are (typically) membrane-bound structures with particular functions within eukaryotic cells. -Are on the surface of cells as well as inside the cell membrane.

Surrounding the Cell

Cell Membrane (Animal and Plant) Job: Boundary between the inside and the outside of a cell Is selectively permeable: (think Mr. Parker!) Composed of: Phospholipid bilayer Transport proteins The model of the cell membrane is called the Fluid-Mosaic Model. (fluid – phospholipids move w/in the membrane, mosaic – patters created proteins on membrane surface)

 Composition of a phospholipid

Cell Wall (Plant) Most commonly found in plant cells & bacteria Job: Supports & protects cells, almost acts as a shell Composed of: Cellulose fibrils

Cillia and Flagella (Animal and Prokaryotes) Job: Helps cells move and aids in fluid transport Cilia = many little hairs on the cell body Flagella = few/one tail(s) Location: On the exterior of the cell – in the cell matrix. Composed of: membrane bound cylinders

Inside the Cell

Nucleus (Plant and Animal) Job: Directs cell activities, storage of genetic info (the brain of the cell) Location: Separated from the cytoplasm by the nuclear membrane (envelope) Composed of: chromatin (DNA) which is the blueprint for proteins

Cytoplasm (Plant and Animal) Job: Suspension of eukaryotic organelles Site of numerous chemical reactions Location: Inside the cell membrane, inside individual organelles Composed of: Cytosol Water, salts, protein filaments, and organic compounds ~ 70% of a cell’s volume

Endoplasmic Reticulum (ER) (Animal and Plant) Job: site of cellular chemical reactions, assembly of proteins Rough: protein synthesis Smooth: numerous biochemical activities, production and storage of lipids Location: in the cytoplasm Composed of: A highly folded membrane, Rough ER has ribosomes imbedded in it for protein synthesis

Ribosomes (Plant and Animal) Each cell contains thousands Job: Make proteins Location: Found on the ER, on the nuclear envelope & floating throughout the cell Composed of: simple structure of 2 subunits: RNA protein

Mitochondria (Plant and Animal) Job: Produces energy (ATP) through chemical reactions known as cellular respiration Breaks down sugar molecules Location: in the cytoplasm Composed of: membranes (outer, and a highly-folded inner membrane) and specific enzymes Facts: Occur in various #s depending on cell function Has its own DNA

Golgi Apparatus (Plant and Animal) Job: Packaging plant Sorts proteins into packages and packs them into vesicles to be sent where they are needed Location: In the cytoplasm Composed of: System like a flat stack of tubes

Lysosomes (Animal) Job: Location: In the cytoplasm Digestive factory and breaks down waste (proteins, fats, and carbohydrates) with enzymes Transports undigested material to cell membrane for removal Location: In the cytoplasm Composed of: Digestive enzymes enclosed in a protective membrane and a lipid bilayer Cell breaks down if lysosomes explode - this is how a tadpole looses its tail when it turns into a frog!

Vacuoles (Plant and Animal) Job: Storage, digestion, and waste removal Helps plants maintain their shape Location: In the cytoplasm Composed of: Water & a thin membrane

Chloroplast (Plant) Job: Location: Composed of: Capture light energy (in thylakoid membranes) and convert it into chemical energy through photosynthesis. Location: In the cytoplasm Composed of: A double membrane Grana – stacks of membranous sacs

Cytoskeleton (Plant and Animal) Job: Support and structure (think tent poles!) Cell division and transport Anchors organelles Location: In the cytoplasm Composed of: Microtubules: thin hollow cylinders made of protein Microfilaments: smaller, solid protein fibers

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