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Cells What is a cell? • The smallest living unit and basic building block of life. • The human body has about 100 trillion cells!!! • Different cells in the body are specialized to carry out special jobs…just like the organs in our body! • All cells digest nutrients, excrete waste, synthesize (make) needed chemicals, and reproduce. Cells… • Scientists believe life began somewhere between 3.9 – 3.5 billion years ago. • Cells are the basic unit of life, basic building block of organisms. • Different cells in the body perform various tasks. (Examples: muscle cells are capable of rapid contraction; nerve cells transmit special chemicals to the body about our environment and help us be able to respond). Brain nerve cells Muscle Cells at rest Muscle MuscleCells Cellscontracting What are the two big groups into which cells are classified? • Eukaryotic - type of cell that does have its chromosomes surrounded by a nuclear membrane. (has a nucleus) – Animal and plant cells • Prokaryotic - A type of cell that does not have its chromosomes surrounded by a nuclear membrane (no nucleus) Eukaryotic Cells… • More advanced then prokaryotic • Appeared about 1 million years ago! Dinoflagellates – found on the ocean floor Are there living beings without cells? • Viruses are considered the only living beings that do not have cells. Viruses are constituted by genetic material (DNA or RNA) enwrapped by a protein capsule. They do not have membranes and cell organelles. The Cell Theory • All living things are composed of one or more cells. • The cell is the smallest entity that retains the properties of life. • New cells arise only from cells that already exist. Lets look at the Animal Cell But first…can you tell me: Is it a prokaryotic or eukaryotic cell? How do you know? Microfilament Microfilament Cytoplasm Microfilament Plasma (Cell) Membrane • Holds cell together • regulates the movement of materials into and out of the cell • Cell membrane is made up of proteins and a double layer of lipid (fat) molecules. • Border/City Wall The Cell Membrane http://library.thinkquest.org/C004535/cell_membranes.html Mitochondrion • Tiny oval shaped organelles • Mitochondria provide the cell with the needed energy. • Glucose (sugar) molecules are transported to the mitochondria where it can be broken down and made into energy (ATP). • Cellular Respiration: sugar molecules combine with oxgyen to form carbon dioxide and water. Energy is also released and stored in a compound called ATP. Power Plant of the cell Nucleus • The control center of the cell (just like your brain is the centre for your body). • It directs all cell activities including reproduction and metabolism. • It contains the genetic material (DNA) • In a city it would act like City Hall Nuclear Membrane (Envelope) • The outer lining of the nucleus (kind of like its skin) • Regulates materials into and out of the nucleus • In a city it would act like the security gaurds or a fence for City Hall…only allowing certain molecules in. Chromatids/ Chromatin • Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. • Two chromatid make up a chromosome. • Mayor/Councilors Nuclear Pore • Openings in the nuclear membrane that permit passage of substances into nucleus • City Hall gates/doors Ribosomes • The organelles that make proteins! • The smallest organelle found in the cytoplasm. • In order for cell growth and reproduction to happen…ribosomes need to be making proteins. • Lumberyard/steel factory (raw materials for building) • Ribosomes can attach to Endoplasmic Reticulum depending on the type of cell. Nucleolus • Produces ribosomes • Contractor or forest Lysosome • Organelles formed by the golgi apparatus. • Contain digestive enzymes for breaking down old organelles and bacteria. • They are only found in animal cells. • They play a big role in the human body’s defense mechanism to fight harmful substances. (White Blood Cells) • Garbage truck/landfill Centrioles • Every animal-like cell has two small organelles called centrioles. They are there to help the cell when it comes time to divide. • Aid in cell reproduction • Maternity ward/midwife Vacuole • An organelle that stores food and wastes left over by chemical processes inside the cell. • In a city it would be like a Warehouse Golgi Complex • Stores, modifies, and packages proteins from the rough endoplasmic reticulum. • The Golgi apparatus also creates vesicles which help take contents outside the cell. • Factory • http://www.johnkyrk.com/golgiAlone.html Microtubule/Microfilament • Microtubule - Long, hollow, cylindrical tubes that help transport materials throughout the cytoplasm. • Microfilament – long, solid, threadlike strands found in the cytoplasm that help provide shape and movement cells. Endoplasmic Reticulum • Fluid-filled canals transport materials throughout the cell • Smooth = no ribosomes; Rough = ribosomes • Trucking/Railway/Metro Transit Cytoplasm • Watery material containing substances for cell metabolism • Everything else in the city Good Link! • http://www.biology-questions-andanswers.com/cell-structure.html