Cells!

Have we always known about cells? No, they are too small to see with just our eyes. First, we needed the invention of the microscope to see things this small.

Compound microscope Specimen is magnified as light passes through several lenses.

Robert Hooke: English Scientist: observed cork with a microscope. He thought the box-like structures he saw looked like jail cells…

Anton Van Leewuenhooke: Discovered bacteria, protizoa, and other microscopic organisms.

Electron Microscope Some things are so small light waves totally miss them. Waves from electrons are used to “see” these very small objects.

Blood as seen with compound microscope Blood seen with electron microscope

Pollen Foot of house fly Staple in Paper Moth scales

Cell Theory: Cells are the basic unit of life. All cells come from pre-existing cells.

Exceptions to the cell theory The First Cell could not have arisen from a pre-existing cell. Viruses are not composed of cells but do contain genetic material. Although considered organelles, Mitochondria and Chloroplasts contain genetic material and can reproduce inside a cell.

Two types of cells Prokaryotic cells: Lack membrane bound structures such as a nucleus, mitochondria and chloroplasts. Pro = before Karyotic = nucleus Examples: Bacteria

Notice… no nucleus, no mitochondria, no chloroplasts

Eukaryotic cells Have membrane bound structures such as a nucleus, mitochondria… Eu = true Karyotic = nucleus Examples: all other cells

Cell Size Prokaryotic/bacteria: very small… 1 to 10 micrometers Eukaryotic: bigger… from 10 to 100 micrometers Chicken egg cell = 6 cm (the whole egg) Nerve cell = 1 meter long Human egg cell = 100 micrometers Red blood cell = 9 micrometers Skin cell = 20 micrometers

White blood cell and bacteria

Cell size and surface area Length of side (cm) 1 cm3 cm Total surface area (cm2) Total volume (cm3) Surface are to volume ratio

Cell size and surface area Length of side (cm) 1 cm3 cm Total surface area (cm2) 1cm2 x 6 sides = 6cm2 9cm2 x 6 sides = 54 cm2 Total volume (cm3) 1x1x1 = 1cm33x3x3 = 27cm3 Surface are to volume ratio 6:154:27 = 2:1

Structural heirarchy: Atoms: elements = carbon, hydrogen Molecules: water, glucose Organelles: nucleus, ribosome Cells: muscle cell, blood cell Tissue: fat tissue, bone tissue Organ: Stomach, lung Organ system: digestive system Organism: us

Cell Organelles 1. Plasma membrane (cell membrane) –Function: selectively permiable, keeps contents of cell in –Structure: phospholipid bilayer –In both plant and animal cells

Cytoplasm Function: site of many chemical reactions, gives cell its shape Structure: gel like substance made of 80% water.

Nucleus Function: the control center for all cell functions. It controls growth and cell division Structure: Envelope surrounding DNA

Nucleolus Function: Makes ribosomes Structure: Dense body inside the nucleus

Endoplasmic Reticulum Function: Aids in the assembly and transport of proteins and lipids. Structure: a network of folded membranes that form channels from the cell membrane through the cytoplasm to the nuclear membrane

Ribosome: Function: assembles proteins Structure: small dot like structures found on the E.R. or in cytoplasm

Mitochondria Function: break down carbohydrates and sugars, making energy from the food we eat Structure: 2 membranes, inner membrane folded, has own DNA

Golgi Complex Function: Packages materials for release from the cell. Structure: Stacks of flattened membranes and vesicles budding off

Lysosome Function: disposal and recycling units of the cell. (little stomachs) Structure: Membrane bound structures containing enzymes necessary for digesting certain material in a cell

Vacuole: Function: stores food, water, and waste Structure: fluid filled sac (plant cells have large vacuoles)

Centriole: Function: aids in animal cell division Structure: nine sets of three fused microtubles arranged in an open star shape and located just outside of the nucleus

Chloroplast Function: turns the sun’s energy into food (photosynthesis) Structure: 2 membranes, oval, green

Cell Wall Function: support and structure for cell. Structure: cellulose fibers

Cell Membrane Phospholipid bilayer

Selective Permeability The following substances can easily pass through the cell membrane…. Lipid soluble substances Small stuff –Glucose, oxygen, carbon dioxide, ions

Passive Transport: no energy required Diffusion: movement of molecules from a high concentration to a low concentration

Facilitated diffusion –Membrane proteins help molecules pass through the cell membrane.

Osmosis: Movement of WATER molecules from a high to a low concentration.

Active Transport: requires energy (ATP) Movement of molecules from a Low to a High concentration. Facilitated transport: –Some membrane proteins require energy to move molecules through the cell membrane.

Pinocytosis: cell drinking Phagocytosis: cell eating

Cell Organelle Lab These pictures are what you should have seen in the microscope… Cork Elodea Cheek cells Onion skin