Biology I10/18/12  HW: Cell Theory – Write & Restate  Take out 7.1 Reading Guide

CHAPTER 7 CELL STRUCTURE & FUNCTION

Objectives  Explain what the cell theory is.  Describe how researchers explore the living cell.  Distinguish between eukaryotes and prokaryotes.

7.1 Life is Cellular  Cells are the basic structural and functional units of life.  They differ in structure and complexity  This idea is relatively new  Microscopes were first used around mid-1600’s  The invention of microscopes made the discovery of the cell possible

Robert Hooke  In 1665, Robert Hooke used an early compound microscope to look at cork  Observed that cork was made up of 1000’s of hollow chambers  Dubbed them cells since they looked like the monastery’s tiny rooms called “cellula”.

 Late 1600’s- Dutch textile salesman  Created different types of microscopes  Observed pondwater and found living organisms  Discovered over 5,000 types of microscopic life  Lenses were able to magnify up to 300X Anton van Leeuwenhoek

The Cell Theory A fundamental concept: a summary of confirmed discoveries  Cells are the most basic unit and structure of life  All living things are made up of cells  New cells are produced from existing cells

More Discoveries  1839 – German biologists Matthias Schleidan & Theodor Schwann  proposed that all organisms are made of cells.  1855 – German physician Rudolf Virchow  Proposed that all cells produce more cells through time

Exploring The Cell Three major types of microscopes 1. Light Microscope  Magnifies 40-1,000 times  Used to magnify objects that light can pass through  Uses slides

2. Electron Microscopes - Uses electrons to illuminate objects  Magnifies from 30,000 to 9 million times  Two types  Transmission – Beam of e - pass through thin slice Images are 2-D Useful to study internal cell structures, large proteins  Scanning – beam of e - scan over surface 3-D images Useful to study external structure  Can only be used to look at dead specimens

3. Scanning Probe Microscopes  Traces surface of sample with a probe  View single atoms, DNA, protein molecules  Can view living things

Cells  Cells come in a variety of shapes  Range in size from microscopic bacteria to giant amoeba  All cells have a cell membrane – outer flexible barrier  All cells have (or had) DNA Chaos carolinensis – Giant amoeba, approximately 1mm in length Mycoplasma pneumoniae

Cells Cell membrane Nucleus- containing DNA

 Eukaryotes- have cells that enclose their DNA in a nucleus  Prokaryotes- cells that do not enclose their DNA in a nucleus 2 Main categories of cells  Nucleus: large, membrane-bound structure that contains the cell’s genetic material in the form of DNA

Prokaryotes  Are generally smaller than eukaryotic cells  Have no nucleus  Carry out all of life’s processes  Ex: bacteria Bacillus anthracis

Eukaryotes  Are generally larger and more complex than prokaryotes  Contain dozens of membrane bound structures that are specialized  Nucleus separates DNA from rest of cell  Come in a variety of shapes and sizes  Ex: protists, fungi, plant, and animal cells

HW: Cell Theory: Write & Restate 1. Write the 1 st part of the cell theory 2. Restate the sentence in your own words 3. Draw a picture to describe the statement 4. Repeat steps 1-3 for 2 nd and 3 rd sentences.  Example:  Write: Each day the temperature is below 32 degrees.  Restate: It’s freezing everyday!  Draw: SunMonTueWedThurFriSat