CELLS Chapter 6- Cell Structure and Function

A Cell is: the smallest unit that can carry on all of life’s functions Galileo – early 17 th century (1600’s) – Looked at insects – Detailed sketches of insect eye

I. The Cell Theory A.Development of Cell Theory (history) ’s- first lenses used by merchants to determine quality of cloth (look at precision of the weave) ’s- microscope and telescope constructed a. Anton van Leeuuwenhoek- made simple microscope- observed living things in pond water for the first time – Late 1600’s

b. Robert Hooke- looked at thin slice of cork. Noticed it was made of tiny chambers- called them “cells”, mid 17 th century Hooke’s work stimulated others to search for cells in other living things. It became apparent that cells were basic units of all living things Used compound microscope

c. Robert Brown– 1820’s, Botanist, first used word “nucleus” for dark spot in cell

d Matthias Schleiden- German botanist concluded all plants made of cells

e. 1839– Theodor Schwann- Concluded that all animals made up of cells f Rudolf Virchow- Russian physician said “Where a cell exists, there must have been a preexisting cell……..”

B. The Cell Theory-summary of before mentioned scientists and other biologists is one of fundamental concepts of biology 1. All living things are composed of cells 3. New cells are produced from existing cells 2. Cells are the basic units of structure and function in all living things.

II. Basic Cell Structures 1. Smallest- 0.2 micrometers (bacteria) A. Cells come in many shapes and sizes

b. Largest- birds egg and giant amoeba (1000 micrometers)

B. Structures common in most Cells 1. Cell membrane-thin, flexible barrier around the cell. a. Many also have cell wall- strong layer around the cell membrane (found in plants, algae, fungi, and bacteria) b. Support and protect cells, while allowing them to interact with surroundings.

2. Nucleus-large structure containing cell’s genetic material- controls cell’s activities (“brain”)

3. Cytoplasm-Material inside the cell membrane but not including nucleus. Also contains many important structures

C. Prokaryotes and Eukaryotes- Scientists divide cells Into two groups depending on whether they have a nucleus or not. 1. Prokaryotes-no nucleus a. Smaller and simpler than cells of eukaryotes b. Do have cytoplasm, cell membrane, ribosomes c. Still carry out all activities associated with life

2. Eukaryotes-do contain nucleus and membrane bound organelles (includes plants, animals, fungi) a. Contain cytoplasm and cell membrane b. Also contain dozens of other specialized structures called organelles (means tiny organs)

KEY CONCEPT Technology continually changes the way biologists work.

Imaging technologies provide new views of life. Unitl 1600’s, cells were not known to exist! A microscope provides an enlarged image of an object. stoma –light microscopes (LM) 2000x

stoma – scanning electron microscopes (SEM) Imaging technologies provide new views of life. A microscope provides an enlarged image of an object. –light microscopes (LM) 1500X

– transmission electron microscopes (TEM) stoma – scanning electron microscopes (SEM) Imaging technologies provide new views of life. A microscope provides an enlarged image of an object. –light microscopes (LM) 5000X

Microscopes Compared and Contrasted! Type of Microscope Image Source Best Magnifiying Power AdvantagesDis- advantages Compound Light Pass light through 1500X-2000XCan view living cells Not enough power, 2D Scanning Electron (SEM) Passes beam of electrons over surface 50,000XGreat 3D details Works only in vacuum – no living cells Transmssion Electron (TEM) Passes beam of electrons through 100,000X (1 text says 2 millionX!) Best magnfication of all Works only in vacuum – no living cells, 2D