Transcript Cell
The Cell Theory 1. All living things are composed of cells 2. Cells are the building blocks of more complex structures 3. All cells come from preexisting cells Two Classes of Cells Prokaryotic – Lack a true nucleus – Lack most organelles – Bacteria Eukaryotic – Have a true nucleus – Contain organelles • Specialized structures within cells that perform tasks – Animals – Plants – Fungi – Protists Microscope Review Question • On high power you use the large knob to bring a cell into focus. But, all of a sudden the cell is gone! • Why? What should you do? • Ooops! Only use the small (fine focus) knob on high power. • Go back to low power and start over Microscope Review Question • A microscope at • Medium power = 5 x 10 another school has an • Medium power = 50 eyepiece that • Objects will seems 50 provides 5x times bigger on medium magnification. The power than they are in medium power lens real life provides 10x magnification. • What is the total magnification on medium power? Microscope Review Question • Why couldn’t you focus on three overlapping threads at once? • They were too thick. • Our microscopes have a shallow “depth of field” – you only see a tiny “slice” of space at any time Nucleus- contains genetic information (DNA), • “brain of the cell” •Protected by nuclear membrane •Filled with nucleoplasm •Nucleolus at the center Endoplasmic Reticulum- ships products throughout the cell Rough ER- ships proteins Smooth ER- ships Lipids Flagellum- propels cell Lysosome- digests materials Centriole- aids in cell division Cytoskeleton- provides structure and aids in movement Mitochondrionconverts energy, makes ATP for the cell Cell membraneencloses and controls what enters and leaves the cell Golgi apparatusships products outside of the cell Ribosomesmake proteins Central vacuolestores water Cell wallprovides structure Chloroplast- Site of photosynthesis Plant vs. Animal Cells Plant cells • have cell walls • contain chloroplasts •look green • have larger vacuoles Cell Membrane “Water loving” (Hydrophilic) heads face the inside (cytoplasm) and outside of the cell where there is lots of water “Water fearing” (Hydrophobic) tails face each other http://www.pearsonsuccessnet.com Online 6.4 pg 2 internal membrane system Selectively Permeable Membrane • Small and uncharged substances move freely across the cell membrane – No attraction to charged heads • Charged substances need help getting across – Attracted to charged heads • Large substances cannot cross Diffusion • Movement of molecules from an area of high to low concentration until a balance is reached • No energy needed • Small, uncharged substances – O2 and CO2 • When balanced, molecules still move, but at the same rate in both directions Cells are limited in size • Food, nutrients, and gases must enter and leave through the membrane • The larger the cell, the larger the surface area needs to be to stay efficient • Cells with a high surface area: volume ratio are most efficient • Conclusion- in order to be efficient, cells must be small! http://www.pearsonsuccessnet.com Lab 6 pg2 Osmosis Diffusion of water across a selectively permeable membrane Cells react to the solutions they are in: – Hypotonic- lower concentration of solute than watercells swell (cytolysis) – Isotonic- equal concentrations of solute and watercells don’t change – Hypertonic- higher concentration of solute than watercells shrink (plasmolysis) Exocytosis • Releasing large products from a cell http://www.coolschool.ca/lor/BI12/unit4/U04L05.htm http://www.middlesexcc.edu/faculty/Barbara_Bogner/111unitone.html Endocytosis • Engulfing large products into a cell “Diffusion Across a Model Cell Membrane” Lab Activity Glucose / Starch Solution Water and Iodine Pre-Lab Discussion How will you determine if starch diffused? In what direction will it move? How will you determine if glucose diffused? In what direction will it move? How will you determine if iodine diffused? In what direction will it move? How will you determine if water diffused? In what direction will it move?