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Cell Structure & Function
Chapter 7
The Discovery of the Cell
• Without a tool to make them visible cells were until the invention of the microscope
• 1665 - Robert Hooke used an early microscope to look at cork cells.
• About the same time Anton van Leeuwenhoek observed tiny organisms in pond water. http://www.youtube.com/watch?v=wzI2RrBYZ5U
Early Discoveries
• 1838 - Matthias Schleiden a German botanist concluded that all plants are made of cells.
• 1839 - Theodor Schwann a German biologist stated that all animals are made of cells.
• 1855 - Rudolf Virchow a German physician concluded that new cells can only be produced by division of existing cells
Cell Theory
• All living things are made up of cells.
• Cells are the basic units of structure and function in all living things.
• New cells are produced from existing cells through cell division.
How do microscopes work?
• Most use lenses to magnify the image of an object by focusing light or electrons.
• Types of microscopes:– Light microscopes – images 1 millionth of m– Electron microscopes – images 1billionth of m
• TEM – transmission – thin samples, can see cell structures & molecules
• SEM – scanning – 3-D surface images
Light Microscope image
SEM Images
TEM Images
Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
As you can see cells come in many sizes and shapes
All cells have some similarities:
• At some point they contain DNA
• All cells are surrounded by a thin flexible barrier called a cell membrane or plasma membrane.
But they also have differences and so are seperated into 2 broad groups:
Eukaryotes and Prokaryotes
Prokaryotic
• Do not have structures surrounded by membranes
• Do not separate DNA within a nucleus
• One-celled organisms, Bacteria
Eukaryotic• Contain organelles, specialized structures that perform specific
functions; surrounded by membranes• Nucleus separates DNA from the rest of the cell• Most living organisms, great variety
Plant Animal
http://library.thinkquest.org/C004535/eukaryotic_cells.html
What do these cells haveIn common?
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
http://waynesword.palomar.edu/images/plant3.gif
“Typical” Plant Cell
Cell Parts
Organelles
Inside the CellTwo major parts
Cytoplasm
• Gel-like mixture also called cytosol
• Portion outside the nucleus
• Surrounded by cell membrane
• Contains organelles of eukaryotes – specialized structures that perform specific tasks
Nucleus • Directs cell activities
• Separated from cytoplasm by nuclear membrane
• Contains genetic material – DNA – which contains coded information to make proteins
• Prokaryote cells lack a nucleus but they do contain DNA
Nuclear Membrane
• Surrounds nucleus• Made of two layers• Openings called
nuclear pores allow material to enter and leave nucleus
• Also called the nuclear envelope
http://library.thinkquest.org/12413/structures.html
Chromosomes
• In nucleus• Made of DNA• Contain instructions
for traits & characteristics
• Usually in the form of long thin threads called chromatin
http://library.thinkquest.org/12413/structures.html
Nucleolus
• Small dense region inside nucleus
• Involved in the assembly of organelles called ribosomes
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Membrane-bound sacs for storage of water, salts, proteins, and carbohydrates
• Plants usually have a large vacuole that helps maintain shape
• Paramecium – contractile vacuole
http://library.thinkquest.org/12413/structures.html
Lysosome• Small organelles filled
with enzymes to digest waste
• Transports digested material to cell membrane for removal
• Also breaks down old organelles no longer needed
http://library.thinkquest.org/12413/structures.html
Cytoskeleton
• Helps maintain cell shape and also in movement.
• Internal network of protein fibers:• Microfilaments • Microtubules
Ribosomes
• Each cell contains thousands
• Make proteins using instructions from DNA
http://library.thinkquest.org/12413/structures.html
Endoplasmic Reticulum• Internal membrane
system where compounds are assembled and transported
• Smooth ER: lacks ribosomes; makes lipids
• Rough ER(pictured): ribosomes embedded in surface; modify proteins made by ribosomes
Golgi Apparatus
• Modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or released outside the cell.
• Bundles proteins in tiny vesicles.
http://library.thinkquest.org/12413/structures.html
Mitochondria
• Convert chemical energy stored in food (glucose) into compounds that are able to be used by cells –ATP
• In humans most all of our mitochondria come from the cytoplasm of the egg cell – so you got yours from your mother.
• They also contain their own DNA!
http://library.thinkquest.org/12413/structures.html
Chloroplast
• Capture energy from sunlight and convert it into food – sugars – that contain chemical energy in a process called photosynthesis.
• Surrounded by two membranes
• Contain pigment called chlorophyll
http://library.thinkquest.org/12413/structures.html
Surrounding the Cell
Cell Membrane
• Outer membrane of cell that controls movement in and out of the cell
• Double layer • Also known as the
plasma membrane
http://library.thinkquest.org/12413/structures.html
Cell Wall
• Most commonly found in plant cells & bacteria
• Supports & protects cells
http://library.thinkquest.org/12413/structures.html