Chapter 17 Cell Intro and Theoryx

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Transcript Chapter 17 Cell Intro and Theoryx

Cell Theory and Cell
History of Cell Study
Hooke- In 1665 was the first
person to describe cells. He looked
at a piece of cork under a compound
microscope he made. He saw little
box like structures he called cells or
“little rooms.”
History of Cell Study
van Leeuwenhoek- a Dutch
naturalist (early 1600’s)
developed the first microscope.
In 1673 he looked at pond scum
and described what saw as
“anumalcules” or little animals.
History cont…..
 Robert
Brown- (1831) discovered the nucleus of
the cell.
 Matthias Schleiden- (German, 1838) a Botanist,
concluded that all plants were made up of cells.
 Theodor Schwann- (German, 1839), studied animal
cells. Concluded that animals were made up of
 Rudolf Virchow- (1858) concluded that all new
cells must come from previously existing cells.
The Cell Theory
The cell is the basic unit
of life of all living things.
2. All living things are made
up one or more cells.
3. Cells come from preexisting cells.
Exceptions to the
Cell Theory
The first cell could not have
arisen from a previously
existing cell, Scientists don’t
know the origin of the first
cell and no one was there to
record what happened.
History of Cell Study
are so small they cannot be
seen without a microscope.
Scientist did not know much about
cells until the discovery of the
microscope. Today we have light,
dissecting, scanning electron, and
transmission electron microscopes.
All cells contain
2 Types of Cells
Prokaryote-No Nucleus or membrane
bound Organelles except ribosomes.
They are single celled and date back
3.5 billion years (Cynobacteria). They
are further classified as eubacteria
or archaebacteria.
2 Types of Cells
Eukaryotic-Has a nucleus and
organelles bound by a cell membrane.
All living cells that are not bacteria
are eukaryotes. Comes from Greek,
“eu” true and karyote “kernel”.
is just another name for
common bacteria. They are the most
common prokaryote and the world’s
smallest cell. Bacteria have a cell wall
( a hard exterior covering), cell
membrane, no nucleus, ribosomes, and
circular DNA shaped like a rubber
are the second kind of
prokaryote. Three types:
Methane making found in swamps.
Heat-loving found in hot areas.
Salt-loving found in extremely salty
water. Heat and salt loving are
called Extremophiles.
are the largest cells, normally
10 times the size of prokaryotes.
Cell Size
average human has about
100 trillion cells in their body. Most
cells in the body are 5 to 20 µm in
All cells have
All cells have cell membranes,
organelles, cytoplasm, and DNA.
Most cells are microscopic in size,
however a chicken egg is one big cell.
An ostrich egg is the largest single
Cell Size
cells are small because they
take in food and get rid of waste
through their outer surface. The
area of a cells surface vs the cells
volume limits a cells size. Small cells
are much more efficient than large
Benefits of Multicellular
Larger size
2. Longer life
3. Specialization of function
Images of cells
Cell Membrane
Separates the cell organelles from the
outside world. Made up of a
phospholipid bilayer. Heads are polar
and face outward and the tails are
nonpolar and face inward. Passage ways
in the bilayer are called channels which
allow only certain substances to enter
the cell.
Contains the DNA and controls the
cells life activities.
Jelly like material inside the cell
that all the organelles float in. Fills
the area from inside the cell
membrane to the nuclear membrane.
It is made up mostly of free floating
ribosomes and water.
Structures inside the cell that carry
out specific tasks so the cell can
carry out the basic functions of life.
Really means “small organs”.