Discovery of cells Cells 1st discovered in 1665 by Robert Hooke Viewed dead cork cells with simple light microscope

Discovery of cells 1st live cells seen by Anton van Leeuwenhoek

Cell Theory About 150 years after 1st observations, scientists developed cell theory Three parts of the theory: 1)All living things are composed of one or more cells 2)Cells are the basic units of structure and function in an organism 3)Cells come only from the reproduction of existing cells

Cell Diversity Size Lots of variation in size; from bacteria to eggs. Some giraffe nerve cells can be 6.5 feet long! However, most are microscopic

Cell Diversity Although there is variation, most cells are microscopic Cells are limited by their surface area to volume ratio Please turn to page 70 of text

Cell Diversity Shape Shapes of cells vary according to their function “form follows function”

Cell Diversity Shape Shapes of cells vary according to their function “form follows function

Internal Organization Internal structures of cells are called organelles Organelles perform specific functions of the cells

Two types of cells Prokaryotes (bacteria) lack membrane bound organelles Eukaryotes have membrane bound organelles We will only study eukaryotes in this course(ZOO ONLY)

Organelles Cell membrane Membrane must regulate what wastes and nutrients leave or enter the cell Because of this the membrane is said to be selectively permeable

Organelles Structure Made of a bilayer of lipids and proteins Proteins and lipids move, creating a fluid mosaic Composition of membrane varies according to cell function

Organelles Cytoplasm Located between cell membrane and nucleus Jelly-like substance in which other organelles are located

Organelles Mitochondria Large organelles located in cytoplasm Manufactures ATP

Organelles Mitochondria Have double membrane Have own DNA Has lead scientists to believe that mitochondria evolved as symbionts with another cell

Organelles Ribosomes Most numerous organelle in the cytoplasm No membrane. They consist of proteins and RNA. Important in production of proteins in the cell.

Organelles Ribosomes 2 kinds Those in cytoplasm produce proteins used in the cytoplasm. They are “free floating” in the cytoplasm Those attached to the endoplasmic reticulum produce proteins for the membrane and those to be exported from the cell

Organelles Endoplasmic Reticulum (ER) Made up of membranous tubules and sacs. Cellular highway for molecules to move from one area of the cell to another

Organelles Endoplasmic reticulum Rough ER--dotted with ribosomes. Lot of rough ER in cells that produce proteins to be exported from the cell or inserted into the membrane

Organelles Endoplasmic reticulum Smooth ER--not covered with ribsomes Responsible for synthesis of steriods in glands, regulation of calcium in muscles, and breaking down of toxins in liver

Organelles Golgi apparatus-- Processing, packaging, secreting organelle of the cell. Like ER, is a network of membranes

Organelles Lysosomes-- Small spherical organelles that enclose certain enzymes within membranes (digestive and breaking down types)

Organelles Cytoskeleton Network of long protein strands in the cell. Provide the cell with support and structure Move organelles around the cell

Organelles Cilia Hair like organelles that extend from cell surface Assist in cellular movement Ex: moving unicellular organisms through water Lining respiratory tract to move particles to throat for swallowing

Organelles Flagella Similar to cilia, though fewer in number Propel cells though solution Made of microtubules similar to those of the cytoskeleton

Organelles Nucleus Contains genetic material of the cell and directs most of it’s activity

Organelles Nucleus Nuclear matrix-- similar to cytoskeleton Double membrane-- called nuclear envelope Chromatin--fine strands of DNA and protein

Organelles Nucleus Chromosomes-- chromatin that coils and packs densely prior to reproduction Site where DNA is copied into RNA. RNA is exported from nucleus and made into proteins

Organelles Nucleus Has at least one spherical area called nucleolus. This area synthesizes and partially assembles ribosomes.

Multicellular Organization-- tissues In most multicellular organisms, cells combine to form tissues Tissue-group of cells that carries out a specific function

Tissue Examples Epithelial tissue-- closely packed cells that cover the surface of things such as skin or lining of the nose

Tissue examples Connective tissue-- loosely scattered arrangement of cells that serves to support and link together other tissues.

Multicellular organization-- organs Organs--several types of tissues that interact to perform a specific function Example-stomach. Made up of epithelial tissue(lining) Muscle tissue (movement) Connective tissue (holds it all together) All work toward one function; digestion

Multicellular organization: organ systems Organ systems- groups of organs that carry out a set of related tasks Example: stomach is part of the digestive systems which also includes the mouth, esophagus, small and large intestines, and other organs.

Evolution of multicellularity Fossil evidence suggests that the first life on Earth was unicellular, prokaryotic organisms similar to bacteria Eukaryotes though to have evolved through symbiosis with prokaryotes (mitochondria have their own DNA and membranes--they could have originally been symbionts inside another cell!)

Evolution of Multicellularity Eventually some unicellular organisms started to live together in colonies. Over time, certain cells began to specialize in certain functions. Eventually, this lead to the development of tissues

What to know for quiz Cell theory Why cells are small Organelles and their function Multicellular organization Evolution of multicellularity