Transcript What is a Cell?

Chapter 1
Cells
1-1
The Diversity of Cells
Essential Questions/Learning
Goals:





State the parts of the cell theory.
Explain why cells are so small.
Describe the basic parts of the cell.
Describe how eubacteria differ from
archaebacteria.
Describe the difference between prokaryotic
cells and eukaryotic cells.
Science Terms
 Cell
 Cell
membrane
 Organelle
 Nucleus
 Prokaryote
 Eukaryote
What is a Cell?
A
cell is the
smallest unit that
can perform all of
the processes
necessary for life.
Cells and the Cell Theory
 Who
discovered cells?
 Robert Hooke (1665)
 Looked a thin slice of cork.
What did the cork look like?
 Tiny
little rooms
 Monks from that age
worked in tiny rooms called
cells.
 These cells were actually
the dead outer layers of
cork cells.
What else did Hooke look at
under his microscope?
 Also
looked at living plants.


These cells appeared to be filled with a juice.
These cells with “juice” were alive.
 Hooke
looked at many different
things under his microscope (fish
scales, hair, fly eyes, etc., but he
mostly studied plants and fungi)
Why did he study mostly plants
and fungi?
 Because
both plants and fungi have
cell walls that make them easy to
see under a microscope.
 Animal cells don’t have cell walls
and this makes them difficult to see
under a microscope.
 Hooke actually thought that
animals weren’t made of cells.
What was Anton Van Leeuwenhoek’s
contribution?
 Made
his own microscopes
and looked at pond scum.
 Saw
tiny organisms in the water
 Called

them animalcules.
Means little animals.
 Today
we call them protists.
Leeuwenhoek’s other discoveries
 Saw
blood cells
 First person to see
bacteria
 Discovered that
yeasts cause
bread to rise.
The Cell Theory:
 Matthias
 ALL
Schleiden (1838): Studied plants
PLANTS ARE MADE OF CELLS!
 Theodor
animals
Schwann (1839): Studied
 ALL
ANIMALS ARE MADE OF CELLS!
 Wrote the first two parts of the Cell Theory.


1. All organisms are made of one or more cells.
2. The cell is the basic unit of all living organisms.
 Rudolf
Virchow (1858):
 Cells
could only come from other cells.
 Wrote the third and final part of the Cell Theory.

3. All cells come from existing cells.
Cell Size:
 How
big?
 SMALL!
 50
cells would needed
to cover the period at
the end of a sentence.
 Some cells are big.
A
chicken egg is actually
one very large cell.
Many Small Cells

WHY so small?
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If a cell gets too large, it’s surface area (s.a.) will
not be large enough to bring in nutrients and
get rid of wastes from the large volume within
the cell.
The s.a. of the cell is a two dimensional surface,
but the interior of the cell is three dimensional.
 This means that the volume of the cell grows
much more than the surface area as the cell

size increases.
MATH BREAK!
(page 6)
Parts of a Cell:
 The
Cell Membrane
 The
cell membrane is the living
protective layer that covers the cell’s
surface and acts as a barrier between
the inside of the cell and the
environment around it.
 The cell membrane controls what enters
and leaves a cell
 It
is like a doorway to the cell.
Cytoplasm
 Cytoplasm
is the “cell
fluid” that fills the
inside of the cell.
 Recall
Hooke’s juice.
What do you call the
structures within a cell?
 Organelles:
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The word means “tiny organs” and they are
found floating in the cytoplasm.
Each organelle has a specific job to
perform for the cell.
Genetic Material:
 All

cells contain…
DNA (deoxyribonucleic acid).
 Basically
a set of instructions for making
parts of cells.
 DNA gets passed on (inherited) by the
offspring of the organism
Where is genetic material
found?
 Nucleus:
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Many cells keep their DNA inside of a
centralized organelle called the nucleus.
Human cells have a nucleus.
Two Kinds of Cells:
 Cells
without a nucleus:
 Prokaryotic
 Two


cells.
subgroups.
Eubacteria
Archaebacteria
 Cells
with a nucleus:
 Eukaryotic
 Plants,
cells.
animals, fungi (the
stuff we can see we just our
eyes that we know to be
alive)
Eubacteria:
 Most
prokaryotes are eubacteria
 Nucleus?

NO!

DO have DNA that is long and circular like a rubber band.
 Organelles?

JUST Ribosomes.

Small round organelles
 Cell

Wall?
YES! Allows it to maintain its shape.

Has a cell membrane within the cell wall.
 Where do they live?
 Soil, water, or on or in other organisms.
 Pretty much on most places on the earth.
Archaebacteria:
A
more rare and extreme form of bacteria.
 Have
circular DNA like eubacteria.
 Have cell wall and cell membrane

Cell wall is different from other organisms.
 Have
ribosomes, but they are more like eukaryotic
ribosomes than eubacterial ribosomes.
 Can live where no other organisms can live.
(extremophiles)
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Thermophiles (heat loving)
Halophiles (salt loving)
Methanogens (methane making)
Eukaryotic Cells
 How
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
big?
These cells are the largest of cells.
Most are still microscopic, but are about 10
times larger than prokaryotes.
 Nucleus?
 YES!

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DNA is found inside the nucleus.
Other Organelles?
 MANY!
Eukaryotes
 What
 An
is a eukaryote?
organism made of MORE than one cell.
 Eukaryotes
include:
 Animals:
multicellular
 Plants: multicellular
 Protists:
 Amoeba:
unicellular
 Algae: multicellular and multicellular
 Fungi:
 Yeast:
unicellular
 Mushrooms: multicellular