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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 cellsRobert 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 cells2) Schleiden – first to see living plant cells3) Schwann – first to see living animal cells4) Virchow – discovered that cells come from other cells
The Cell TheoryThe 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 slide2) Swab the inside of your cheek with a toothpick3) Swirl the toothpick around in the drop of water4) Lay the coverslip down at an angle5) Place a tiny drop of blue dye on one end of the coverslip6) Touch a paper towel to the other side to draw the dye
across the sample7) 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