Cells: Notes 3

Bellwork: Wed. Oct. 3, 2017 2. _______ are basic units of structure & Write: (hint: 1-3 have the same answer ) 1. All living things are made of ______. 2. _______ are basic units of structure & function in living things. 3. New _______are produced from existing______. 4. Read p191 in your book: What are these three statements called? THE __________ ________________ (and – what one word goes in all of the blanks?)

Notes : CELLS 7.1 Life is Cellular

Smallest part of any living thing is the cell

Notes: Scientists began using microscopes to observe living things in the mid-1600s

In 1665, Englishman Robert Hooke used an early compound microscope In 1665, Englishman Robert Hooke used an early compound microscope. He looked at a slice of cork, dead plant material. It seemed to be made of 1000’s of empty chambers. Hooke named them “cells”. The term cell is used in biology to this day.

In Holland, Anton van Leeuwenhoek examined pond water (saw “Animicules”) and a sample taken from a human mouth. He drew the organisms he saw in the mouth— which today we call bacteria. http://www.hardydiagnostics.co m/articles/Leeuwenhoek-Father- of-Microbiology.pdf

Anton van Leeuwenhoek also observed these….

Other scientists observed that cells were the basic units of life: 1838: German botanist Matthias Schleiden concluded that all plants are made of cells. 1839: German biologist Theodor Schwann stated that all animals were made of cells. 1855: German physician Rudolf Virchow concluded: new cells could be produced only from division of existing cells.

The Cell Theory -Cells are the basic units of structure & function became a fundamental concept of biology. -All living things are made up of cells. -Cells are the basic units of structure & function in living things. -New cells are produced from existing cells.

Light Microscopes Light microscopes allow light to pass through specimens & uses 2 lenses to form an image. The first lens is located just above the specimen, enlarging the image of the specimen. The second set of lenses magnifies the image still further. Because light waves are diffracted, or scattered, as they pass through matter Light microscopes can be used to see cells and cell structures as small as 1 millionth of a meter. To study something smaller than that, scientists need to use electron microscopes. light microscopes magnify images up to 1000 times their original size.

Cell Stains one problem with light microscopy is that most living cells are nearly transparent, making it difficult to see the structures within them. So…. Scientists often stain cells so they can be seen more clearly under microscopes.

Cell Stains Using chemical stains or dyes can usually solve this problem. Some of these stains are so specific that they reveal only compounds or structures within the cell.

Some dyes give off light of a particular color when viewed under specific wavelengths of light, a property called fluorescence. Fluorescent dyes can be attached to specific molecules and can then be made visible using a special fluorescence microscope. Fluorescence microscopy makes it possible to see and identify the locations of these molecules, and even to watch them move about in a living cell.

Electron Microscopes Electron microscopes use beams of electrons, not light, that are focused by magnetic fields. Electron microscopes offer much higher resolution than light microscopes.

Transmission Electron Microscopes explore cell structures and large protein molecules producing flat, two-dimensional images. Since beams of electrons can only pass through thin samples, cells and tissues must be cut first into ultra thin slices before they can be examined.

Scanning Electron Microscopes produce three-dimensional images of the specimen’s surface. a pencil-like beam of electrons is scanned over the surface of a specimen. Because the image is of the surface, specimens viewed under a scanning electron microscope do not have to be cut into thin slices to be seen.

A scanning electron microscope picture of a nerve ending A scanning electron microscope picture of a nerve ending. It has been broken open to reveal vesicles (orange and blue) containing chemicals used to pass messages in the nervous system.

Because electrons are easily scattered by molecules in the air, samples examined in both types of electron microscopes must be placed in a vacuum in order to be studied. Researchers chemically preserve their samples first and then carefully remove all of the water before placing them in the microscope. This means that electron microscopy can be used to examine only nonliving cells and tissues.

Prokaryotes and Eukaryotes Cells fall into two broad categories, depending on whether or not they contain a membrane bound nucleus. The nucleus is a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA. The nucleus controls many of the cell’s activities.

Prokaryotes and Eukaryotes Eukaryotes: cells that enclose their DNA in nuclei. Prokaryotes: cells that do not enclose DNA in nuclei.

Prokaryotes smaller and simpler than eukaryotic cells. bacteria are prokaryotes.

Eukaryotes larger and more complex than prokaryotic cells. Most eukaryotic cells contain dozens of structures and internal membranes. Many eukaryotes are highly specialized. There are many types of eukaryotes: plants, animals, fungi, and organisms commonly called “protists.”

Work on your test review for Friday’s test END Work on your test review for Friday’s test

The next three slides are some old Bellworks

Bellwork: Tues/Wed Sept. 21/22, 2010 Find your Bellwork from Friday: 1. All living things are made of cells. 2. Cells are basic units of structure & function in living things. 3. New cells are produced from existing cells. What are these three statements called? (look in your book on 191)

Bellwork: Monday Oct. 4, 2010 Cell Test is THIS Friday Write: Cell Test is THIS Friday Mitochondria is the site of __________ ____________________________________ Chloroplast is the site of ______________________________

Bellwork: Thurs. Oct 2, 2014 Write: Cell Organelle Quiz…