Lesson Overview 7.1 Life is Cellular

Lesson Overview Lesson Overview Life Is Cellular THINK ABOUT IT What’s the smallest part of any living thing that still counts as being “alive?” Can we just keep dividing living things into smaller and smaller parts, or is there a point at which what’s left is no longer alive? As you will see, there is such a limit. The smallest living unit of any organism is the cell.

Lesson Overview Lesson Overview Life Is Cellular Early Microscopes It was not until the mid-1600s that scientists began to use microscopes to observe living things. In 1665, Englishman Robert Hooke used an early compound microscope to look at a nonliving thin slice of cork, a plant material. Under the microscope, cork seemed to be made of thousands of tiny, empty chambers that Hooke called “cells”. The term cell is used in biology to this day. Today we know that living cells are not empty chambers, but contain a huge array of working parts, each with its own function.

Lesson Overview Lesson Overview Life Is Cellular Early Microscopes In Holland, Anton van Leeuwenhoek used better lenses- able to examine living cells!! Examined pond water and samples taken from a human mouth. He drew the organisms he saw in the mouth—which today we call bacteria.

Lesson Overview Lesson Overview Life Is Cellular The Cell Theory Contributors of the cell theory: Robert Hooke- examined dead cells in cork In 1838, German botanist Matthias Schleiden concluded that all plants are made of cells. German biologist Theodor Schwann-all animals were made of cells. In 1855, German physician Rudolf Virchow- new cells could be produced only from the division of existing cells

Lesson Overview Lesson Overview Life Is Cellular The Cell Theory These discoveries are summarized in the cell theory, a fundamental concept of biology: -All living things are made up of cells. -Cells are the basic units of structure and function in living things. -New cells are produced from existing cells. The modern version of the Cell Theory includes the ideas that: Energy flow occurs within cells. Heredity information (DNA) is passed on from cell to cell.DNA All cells have the same basic chemical composition.

Lesson Overview Lesson Overview Life Is Cellular Exploring the Cell Light microscopes-visible light passed through specimen and then through glass lenses X actual size lenses refract (bend) light to magnify the image Magnification: ratio of object’s image size to real size

Lesson Overview Lesson Overview Life Is Cellular Resolution: clarity of image (min distance 2 pts can be separated & still distinguished as 2 points) Contrast: difference between light & dark areas

Lesson Overview Lesson Overview Life Is Cellular Electron Microscopes Electron microscopes (EM) - beams of electrons focused through or onto surface electron beams have shorter wavelength than visible light so much finer resolution Electron microscopes offer much higher resolution than light microscopes.

Lesson Overview Lesson Overview Life Is Cellular Transmission (TEM)- study internal structure of cells Scanning (SEM)- detailed study of 3D image Disadvantage of both - specimen is nonliving

Lesson Overview Lesson Overview Life Is Cellular Cell Stains Cells- nearly transparent, making it difficult to see the structures within them. chemical stains & dyes- can be so specific that they reveal only compounds or structures within the cell.

Lesson Overview Lesson Overview Life Is Cellular Cell Stains Fluorescence microscope- Fluorescent dyes attached to specific molecules and made visible using a Fluorescence microscope possible to identify the locations of these molecules, and even to watch them move about in a living cell.

Lesson Overview Lesson Overview Life Is Cellular Cell Size Most cells 1-100um The smallest objects that the unaided human eye can see are about 0.1 mm long Under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification

Lesson Overview Lesson Overview Life Is Cellular Prokaryotes vs Eukaryotes Major Difference: Prokaryotic cells do not separate their genetic material within a nucleus it is concentrated in nucleoid (no membrane) In eukaryotic cells, the nucleus (with membrane) separates the genetic material from the rest of the cell.

Lesson Overview Lesson Overview Life Is Cellular Nucleus- membrane-enclosed structure containing the cell’s genetic material in the form of DNA. The nucleus controls many of the cell’s activities. Nuclear envelope- encloses nucleus from cytoplasm, double membrane with pores

Lesson Overview Lesson Overview Life Is Cellular Prokaryotic cells- smaller and simpler than eukaryotic cells. Despite their simplicity, prokaryotes grow, reproduce, and respond to the environment, and some can even move by gliding along surfaces or swimming through liquids. Bacteria are prokaryotes. Prokaryotes

Lesson Overview Lesson Overview Life Is Cellular Eukaryotes Eukaryotic cells- larger and more complex than prokaryotic cells. Most eukaryotic cells contain organelles & internal membranes. Many eukaryotes are highly specialized. There are many types of eukaryotes: plants, animals, fungi, and organisms commonly called “protists.”