The Cell

A Little History

• Robert Hooke– English scientist; looked at a slice of

cork under a compound microscope

– Observed small, room-like structures that he called cells

• Because they reminded him of the rooms monks live in

– He only saw the cell walls because cork cells are already dead

A Little History

• Anton van Leeuwenhoek (1674)– Dutch fabric merchant and amateur

scientist

– Looked at blood, rain water, and scrapings from teeth through a simple microscope (one lens)

– Observed living cells and improved the quality of the microscope

A Little History

• Matthias Schleiden(1838): viewed plant parts under a microscope; discovered plant parts are made of cells

• Theodore Schwann(1839): viewed animal parts under a microscope; discovered animal parts are made of cells

• Rudolph Virchow(1855): stated that all living cells come only from other living cells

Cell Theory

1. All living things are made up of cells.

2. Cells are the smallest working units of all living things.

3. All cells come from preexisting cells through cell division.

Definition of Cell

A cell is the smallest unit that is capable of performing life

functions.

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

Two Types of Cells

•Prokaryotic•Greek roots: [pro]=before,[karyon]=kernel (refers to the nucleus)• In domains Bacteria and Archaea

•Eukaryotic•Greek roots: [eu]=true, [karyon]=kernel (refers to the nucleus)•Domain Eukarya

Prokaryotic

• Do not have structures surrounded by membranes-no nucleus

• Few internal structures

• One-celled organisms– Bacteria

http://library.thinkquest.org/C004535/prokaryotic_cells.html

Eukaryotic• Contain organelles surrounded by membranes• Most living organisms

Plant Animal

http://library.thinkquest.org/C004535/eukaryotic_cells.html

Cell Structure & Function

http://koning.ecsu.ctstateu.edu/cell/cell.html

http://waynesword.palomar.edu/images/plant3.gif

“Typical” Plant Cell

cytoplasm

ribosome

Golgi aparatus

vacuole

Cell wall

Cell membrane

nucleus

nucleolus

Nuclear membrane

mitochondria

chloroplast

Endoplasmic Reticulum

“Typical” Animal Cell

http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

Cell membrane

nucleus

nucleolus

Nuclear membrane

lysosome

mitochondria

cytoplasm

ribosome

Golgi aparatus

Endoplasmic Reticulum

Cell Parts

Organelles

Surrounding the Cell

Cell (Plasma) Membrane• Controls movement in and

out of cell

Cell Wall

• Most commonly found in plant cells & bacteria

• Supports & protects cells

• Plant cell walls are mostly made of cellulose

http://www.yellowtang.org/images/cell_walls_in_plant_c_ph_784.jpg

Inside the Cell

Nucleus

• “the information center” or “brain” of the cell

• Contains genetic material – Chromosomes (DNA)

http://www.cartage.org.lb/en/themes/Sciences/Zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Nucleus/cellnucleus.jpg

Nuclear Membrane

• Surrounds nucleus• Has pores that allow

mRNA to move out of nucleus

http://www.microscopy.fsu.edu/cells/nucleus/images/nuclearenvelopefigure1.jpg

Nucleolus

• Specialized region in the nucleus where ribosome subunits are made

http://www.microscopy.fsu.edu/cells/nucleus/images/nucleolusfigure1.jpg

Cytoplasm

• Portion of the cell outside of the nucleus

• Gel-like substance

Endoplasmic Reticulum, ER• Manufactures products for

secretion

• Smooth ER: lacks ribosomes– Makes and packages

lipids• Rough ER: ribosomes

embedded in surface – Makes and packages

proteins

Ribosomes

• “Work benches” for protein synthesis

• Found on the Rough ER & floating throughout the cell

http://publications.nigms.nih.gov/insidethecell/images/ch2_ribosome_proteinbig.jpg

Mitochondria

• Energy Organelle– Breaks down glucose to

produce energy packets (ATP) for the cell

• Contains its own DNA

http://www.cartage.org.lb/en/themes/sciences/zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Mitochondria/mitochondria.jpg

Golgi Bodies

• Modifies, sorts and packages proteins and other products for distribution

Lysosome• Bags of enzymes that

break down old organelles and bacteria

• Keeps the cell clean

http://publications.nigms.nih.gov/insidethecell/images/ch1_lysosome.jpg

Vacuoles• Membrane-bound

sacs for storage, digestion, and waste removal

• Much larger in plants• Help plants maintain

shape

Chloroplast

• Usually found in plant cells

• Contains green chlorophyll

• Where photosynthesis takes place

http://www2.mcdaniel.edu/Biology/botf99/cellstructure/chloroplast..jpg

flagella• Long, slender, whip-like projection

used for movement

cilia• Small hair-like structures found on the

surface of cells used for movement