Cells History • Robert Hooke saw cork under a microscope and though the cellulose looked like little rooms so he called them, “Cells” • Van Leeuwenhoek- observed bacteria and sperm called animalcules • Rober Brown- discovered the nucleus (not the same as in chemistry)
Cell Theory (3 parts) • 1. Every organism is composed of cells • 2. The cell is the smallest unit of life • 3. Life comes only from cells
Spontaneous Generation • Ancient untrue theory that: Life comes from non-living matter • According to this bogus theory, Life comes from the “Either” • Argument for: Meat that rots spawns maggots • Argument against: the Pasteur Flask • The cell theory states that: Cells only arise by the division of a previously existing cell. • LIFE COMES ONLY FROM LIFE!
Components of the Cell • A plasma membrane surrounds the cell • Small parts of the inside of the cell are called ORGANELLES (little organs) • Two major kinds of cells: • PROKARYOTIC- (Pro = before, Karyon = nut) Bacteria, no membranes around it’s organelles, just cell soup • EUKARYOTIC- (Eu = true, karyon = nut) Animals (Us) and plants, these do have membranes around their organelles • Plants have a cell wall and a plasma membrane, animal cell have no cell wall.
Plasma Membrane • Bilipid layer (bi = two, lipid = fat, two fat layers) containing phospholipids, forms a fluid mosaic • The heads of the plasma membrane face to the outside and into the cell, the tails point at each other inside the membrane • The heads are HYDROPHILIC (hydro = water, philic = loving) because phosphate makes the head polar and water loves polar • The tails are HYDROPHOBIC (hydro = water, phobic = fearing) because they are really ___ and water and ____ don’t mix because fat is non-polar.
lipid bilayer fluid fluid one layer of lipids one layer of lipids Fig. 4.3, p. 52
PLASMA MEMBRANE CONTENTS • Cholesterol is found here • While the plasma membrane is basically ______ there is some protein in it. • Surface Protein- can be receptors. When attached to carbohydrates they are called RECEPTORS • These protein receptors serve as markers for the cell (ex. Human egg) and bind specific hormones to the cell (ex. Thyroxin to the thyroid gland) • Transmembrane Proteins- are transport proteins and span the outside and inside, make good channels for large molecules to pass into and out of the cell (ex. Insulin)
oligosaccharide groups cholesterol phospholipid EXTRACELLULAR ENVIRONMENT (cytoskeletal pro-teins beneatch the plasma membrane) open channel protein gated channel proten (open) gated channel proten (closed) active transport protein RECEPTOR PROTEIN LIPID BILAYER ADHESION PROTEIN RECOGNITION PROTEIN (area of enlargment) TRANSPORT PROTEINS CYTOPLASM PLASMA MEMBRANE Fig. 4.4, p. 53
CELL SIZE • Cells must be a certain size (the outside must be larger than the inside) • The outside of the cell must always be larger then the inside of the cell, this is called the cell surface to volume ratio • Normally, the outside of the cell is larger then the inside and this allows for transport of the cells contents • If the cell ratio is off (the inside is more then the outside) then the cell will not function properly • So a cell can only be a certain size. Mouse cells are the same size as ________ cells.
What size are cells? The period at the end of a sentence is the size of the biggest cell, the human egg. This is approximately 100 micrometers A red blood cell (RBC) is approximately 7 micrometers, how many RBCs would fit in the period at the end of a sentence?
EUKARYOTIC CELL STRUCTURES • CYTOSKELETON- network of protein (microfilaments and microtubules) that builds scaffolding giving the cell it’s shape • Flagella/ Cilia- microtubules that move • Nucleus- Control center of cell • Chromosomes- hereditary info found in the nucleus • ER- Endoplasmic Reticulum (Endo = inside, Reticulum = net)comes in two varieties: • ROUGH ER- has bumps of RNA called RIBOSOMES • Creates PROTIEN • SMOOTH ER- no bumps • Creates FAT
EUKARYOTIC CELL STRUCTURES (continued) • Golgi Complex- Packages products from ER • Lysosomes- Garbage collector of the cell • Mitochondria- power plant of the cell • Chloroplasts- found in plants (not animals) site of photosynthesis • Necleolus- Makes RNA inside the nucleus • Chromosomes- hereditary info found in the nucleus • Centrioles- responsible for cell division
EUKARYOTIC CELL STRUCTURES in a word • Cytoskeleton = shape • Flagella = whip • Celia = hairs • Rough ER = protein • Smooth ER = fat • Nucleus = Brain • Chromosomes = DNA • Golgi = packaging • Lysosomes = garbage • Mitochondria = energy • Nucleolus = ribosome (RNA)