Assignment Discovery: Cells - Types of cells 6:02. The Incredible World of the Microscope - 20:00

Transcription

1 ! Before the middle of the 1600 s we could only study what we could see with the naked eye.! Living things may be either unicellular or multicellular.! Robert Hooke (English) was the first person to look at cork under the microscope and draw and describe what he termed cells.! Cells may be different shapes and sizes.! They reminded him of small rooms or cells in a monastery. Assignment Discovery: Cells - Types of cells 6:02! Matthias Schleiden (German) studied plant cells and concluded that plants are made of cells! Anton van Leeuwenhoek (Dutch) made single lens microscopes that could magnify objects about 200 times.! Theodor Schwann (German) studied animal cells and concluded that all living things are made of cells. The Incredible World of the Microscope - 20:00! Rudolf Virchow (Polish/German, physician) took all previous information and came up with the cell theory.! Compound Light Microscope - more than one lens and uses light to help magnify objects even if they are live.! They can magnify objects thousand times their actual size. 1. Cells are the basic units of all life. 2. All organisms are made of one or more cells. 3. All cells arise from existing cells.! Contrast = to distinguish between different parts of a specimen.! Resolution = to make or enhance the image to make it more clear or sharp. The Microscope - 20:40

2 ! Electron Microscopes - use electron beams instead of light to magnify objects a million times their actual size.! But the object must be fixed in position and placed in a vacuum.! Scanning Electron Microscope or SEM - sends a beam of electrons over the surface of the object.! Transmission Electron Microscope or TEM - sends a beam of electrons through the object. A Drop of Pond Water - 11:57! Cell Structures or Organelles ( elle means miniature or small version of! Cell Membrane ---separates the cell s contents from its environment.-controls what enters and leaves the cell.! It is composed of a phospholipid bilayer (fluid mosaic model) the two ends of the phospholipid molecule behave differently in water.! The phosphate head is hydrophilic ( meaning water - loving ) and the lipid tail is hydrophobic ( meaning water - fearing ).! The membrane may have several proteins embedded in the phospholipid bilayer. Some of them are for identification and some extend all the way through the layer to transport molecules. Bill Nye: Cells 22:00! Cytoplasm -the material between the cell membrane and the nucleus.! It is a semifluid substance made primarily of watervarious structures called organelles are suspended in the cytoplasm. Simply Science: Matter and Energy on the Move Cell Size 3:53

3 ! Cytoskeleton -a network of protein fibers and tubes extending throughout the cytoplasm.! It helps to support and provide shape.-enables the cell to move.! Nucleus -the control center of the cell! It contains most of the cell s genetic materialsurrounded by a nuclear envelope (lipid bilayer)! The command center of the cell! Chromosomes -structures that carry the genetic information! All organisms have a definite number of chromosomescontrol all cellular activity, such as growth and cell division! Nucleolus -a structure in the nucleus, where ribosomes are formed.! *Prokaryote cells belong to organisms whose cells have no definite nucleus.! *Eukaryote cells belong to organisms whose cells have a nucleus surrounded by a nuclear membrane.! Ribosomes -groups of ribosomes act like assembly lines, helping to make proteins from amino acids.! Point of assembly! Endoplasmic Reticulum -a network of membranes that produce materials for the cell.! Rough ER - has ribosomes on its surface and functions in the synthesis of proteins! Smooth ER - makes lipids, processes carbohydrates and modifies chemicals that are toxic to the cell.! A conveyor belt! Golgi Apparatus - is a series of flat, membrane-bound sacs where molecules are sorted, often modified, packaged and distributed to their destination.! A packaging and distribution center! Mitochondria - generates most of the energy needed by the cell to carry out life functions! -change the energy stored in food compounds into a form useful to the cell.! A powerhouse or generator! Lysosome - contains digestive enzymes that help break down large molecules of carbohydrates, proteins, and lipids.! It also digests old organelles that are no longer useful to the cell.! A garbage disposal

4 ! There are extensions of the cytoskeleton used for cellular mobility.! Cilia - short, hairlike projections that usually occur in large numbers on the surface of some cells.! Flagella - long tail-like projections that move in a whiplike fashion.! Ameoboid - amoebas move by a coordinated flow of the cytoskeleton.! Cell Wall - a tough, rigid outer covering that protects a plant cell and helps maintain its shape.! Chloroplasts - structures that enable the plant to make sugars through photosynthesis.! Vacuoles - a membrane bound compartment that serves many functions.! They may absorb water, or store proteins, ions and waste products of metabolism.! A storage container.! Some cells can survive on their own and some cells are specialized and cannot survive alone.! Specialized cells are designed to perform a specific function.! Multicellular organisms depend on the interaction of all the cells.! A semipermeable membrane lets certain molecules pass through and prevents other molecules from crossing.! Several processes are involved in moving materials across the cell membrane. Organelles within the cytoplasm 4:12! These processes can be classified as either passive transport or active transport.! Passive transport is the movement of a substance across a cell membrane without the input of the cell s energy.! Active transport uses cellular energy to move substances across a cell membrane. Passive Transport Active Transport! The most common form of passive transport is diffusion.! Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration.! The rate of diffusion depends on the temperature and the size of the molecules involved. Simply Science: Matter and Energy on the Move Passive Transport 4:00 Simply Science: Matter and Energy on the Move ActiveTransport 5:33

5 ! Diffusion always occurs down a concentration gradient.! A concentration gradient is the difference between the concentration of a particular molecule in one area and its concentration in an adjacent area.! When the molecules have been dispersed evenly, there is no concentration gradient, or we say it has reached dynamic equilibrium.! Some molecules move across cell membranes with the help of carrier proteins in the membrane.! This is called facilitated diffusion.! Facillitated diffusion increases the rate that some molecules cross the cell membrane.! The diffusion of water across a semipermeable membrane is called osmosis.! Cytoplasm is a solution of water and many dissolved solutes.! The natural tendency of water is to move from low solute concentrations to high solute concentrations.! Isotonic Solution - The concentration of the solutes outside the cell is equal to that inside the cell.! Hypertonic Solution - The concentration of the solutes outside the cell is higher than it is inside the cell.! Hypotonic Solution - The concentration of the solutes outside the cell is lower than it is inside the cell.! In order for a cell to move materials against a concentration gradient it must use energy.! This would be going from an area of low concentration to an area of high concentration.! This is called active transport.! Active transport uses carrier proteins and energy to pump ions and molecules across the cell membrane.! The energy for active transport comes from ATP.! Active transport is especially important in maintaining proper ion concentrations inside the cell.! Animal cells pump sodium ions out of the cell and potassium ions into the cell.! This sodium - potassium pump uses about one third of a cell s energy.! These concentration gradients are important for the contraction of muscles, the transmission of nerve impulses, and the absorption of nutrients.! Active transport enables the roots of plants to absorb nutrients from the soil instead of the nutrients moving from the roots back into the soil.! There is a higher concentration of nutrients in the roots than there are in the soil.! When a cell needs to transport large molecules across its membrane, it uses bulk transport.! Cells rely on two types of bulk movement, exocytosis and endocytosis.! During exocytosis, wastes and cell products are packaged in the Golgi apparatus and then secreted out of the cell.! For example..the salty solution in tears.

6 ! During endocytosis, a portion of the cell membrane surrounds desirable macromolecules that are outside the cell membrane.! This portion of the membrane pinches off and becomes a vacuole inside the cell.! If the cell membrane is engulfing a drop of water it is called pinocytosis.! If the cell membrane is engulfing a food particle of solid molecule, it is called phagocytosis. Standard Deviants School Biology: RNA Endocytosis 3:55