DO NOW: Answer the questions from our previous test on the paper in front of you.

TODAY: Introduction to Cells, Cell Theory Notes Cell lab: A look at your own cells! Notes on cell size, the cell membrane Cell Size demonstration

What is a cell? The smallest thing capable of carrying out life processes ALL CELLS: Are surrounded by a membrane Contain DNA Contain cytoplasm (the jelly-like stuff inside the cell)

The discovery of cells Robert Hooke – examined cork under a microscope and saw dead cells Called them “cells” because they looked like the rooms in a monastery where monks lived CELL WALLS

This paved the way for cell science and new discoveries: After Hooke… 1)Leeuwenhoek – first to see living cells 2)Schleiden – first to see living plant cells 3)Schwann – first to see living animal cells 4)Virchow – discovered that cells come from other cells

The Cell Theory The discoveries of Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow led to the development of The Cell Theory: FOUR PARTS: 1)All living things are made of cells. 2)Cells are the basic unit of life (the smallest thing that can be considered living). 3)Cells come from other cells. 4)Cells contain regions or compartments that are specialized to perform certain tasks.

See? Science is COLLABORATIVE!! New scientific discoveries build upon old ones.

LAB: A Look at Your Own Cells! Follow the directions CAREFULLY! 1)Place a tiny drop of water in the middle of your slide 2)Swab the inside of your cheek with a toothpick 3)Swirl the toothpick around in the drop of water 4)Lay the coverslip down at an angle 5)Place a tiny drop of blue dye on one end of the coverslip 6)Touch a paper towel to the other side to draw the dye across the sample 7)View under the microscope starting with the LOWEST POWER

The surface-area-to-volume ratio The more surface area compared to volume, the easier it is for the cell to take in materials it needs Surface area Volume

Cell Size Materials can enter and leave the cell only through the cell membrane These materials must be transported to different parts of the cell The smaller the cell, the easier it is to take up materials needed from the outside and transport them to where they need to go inside

The Cell Membrane Surrounds ALL CELLS Made of a double layer (“bilayer”) of phospholipids POLAR HEAD – “HYDROPHILIC” Sticks to water NON-POLAR TAIL “HYDROPHOBIC” Repels water

The Cell Membrane – A Phospholipid Bilayer

The Cell Membrane - A Phospholipid Bilayer

The Cell Membrane… … is SEMI-PERMEABLE, meaning some things can pass through, and some things can’t … contains large molecules which allow the cell to: a) transport materials across the barrier = transport proteins b) communicate with its environment = receptor proteins with carbohydrate chains

TRANSPORT PROTEINS Channel Proteins: have a tube through which molecules can pass into the cell Carrier Proteins: molecule binds to it and it changes shape to allow the molecule into the cell