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Cell Structure
Chapter 7
Looking at cells
Discovery of Cells
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Robert Hooke was the
first person to see a
cell in 1665.
Hooke used a crude
compound microscope
to view a thin slice of
cork.
He called what he saw
“cells” because the
tiny squares reminded
him of the rooms that
monks lived in.
Looking at cells
A picture of the primitive
microscope that Hooke
used. Notice some of the
parts we’ve discussed.
A diagram of the “cells” that
Hooke viewed under his
scope.
Expanding on Hooke’s work.
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Around 1670 another
man named Anton Van
Leeuwenhoek made a
microscope a little
different then Hooke’s
that magnified 200x.
Van Leeuwenhoek’s
scope was a lot
stronger than Hooke’s
and he was able to see
bacteria in pond water.
Van Leeuwenhoek
called what he saw
“animalcules”.
Measuring the sizes of cells
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Once again scientists use SI units to
measure the length of microscopic
organisms.
Do you think they use meters,
centimeters or even millimeters?
Scientists use Micrometers and
Nanometers to measure microscopic
organisms.
1μm = 0.000001m
1nm = 0.000000001m
Cell Theory
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In 1838 a German botanist named
Mattias Schleiden noticed that cells
make up every part of a living thing.
Later a German zoologist named
Theodore Schwann noticed that
animals are also made of cells.
In 1858 Rudolph Virchow a German
physician noticed that all cells come
from existing cells
These observations formed the three
parts of the cell theory.
Three steps of the Cell Theory
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All living things are made of one or
more cells.
Cells are the basic units of structure
and function in organisms.
All cells arise from existing cells.
Size of Cells
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How big is a cell? 2 μm – 2 mm.
Most cells that we know of are very
small.
Why do you think cells are so small?
Nutrients and water need to diffuse
across the cell membrane and be
distributed throughout the entire cell.
Think about it… Is it easier to
distribute nutrients throughout a big
cell or a smaller cell?
Surface-area-to-volume ratio.
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What is surface area?
The cell membrane of a small cell
has a small surface area and a small
volume.
The cell membrane of a large cell has
a larger surface area and a very
large volume.
The cell with the highest ratio is the
most efficient cell.
What can we tell about the amount of
time it would take for nutrients to make
it to the nucleus of these cells?
Simple cells
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The first cells appeared on earth about
3.5 billion years ago.
The cells were very basic, they had
very few organelles and its DNA was
not surrounded by a nucleus.
These cells are called prokaryotic cells.
An example of a prokaryotic cell is
bacteria.
Prokaryotic cells
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Prokaryotic cells are very small, only
one to two μm in diameter.
Prokaryotic cells are filled with a fluid
like substances called cytoplasm.
These cells have a cell membrane
and a cell wall. (The cell wall of the
cork cell is what Hooke saw)
Most bacteria move using a long
threadlike structure that spins like a
propeller called a flagellum.
Some examples of bacterial cells.
Larger cells
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The cells that make up our bodies
are much more complex than
prokaryotic cells.
Our cells have many organelles that
each have a specific function.
Our cells also have a nucleus that
protects our DNA.
Our cells are called eukaryotic cells.
Eukaryote- Cell that has a nucleus,
internal compartments and appeared
on earth about 1.5 billion years ago.
Eukaryotic Cell
Important Organelles (Phospholipid
Bilayer)
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Phospholipid Bilayer- Double layer that
makes up the cell membrane.
Town Boundary
Important Organelles (Nucleus)
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Nucleus- Controls most functions in a
eukaryotic cell. Houses the DNA.
Surrounded by a nuclear envelope.
Nuclear Pores allow substances in and out
of the cell.
The
nucleus
acts like
City Hall
Important Organelles (Endoplasmic
Reticulum)
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Endoplasmic Reticulum- Helps distribute
proteins throughout the cell. Smooth & Rough.
The rough ER is studded with ribosomes.
The ER is
like a
factory.
Important Organelles (Golgi)
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Golgi Apparatus- Packages and distributes
proteins throughout the cells.
The Golgi
acts like a
post office
or a
packaging
plant.
Important Organelles (Vesicle)
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Vesicle – A small membrane-bound sac
that transports substance throughout a
cell.
A vesicle
acts like
a mail
truck.
Important Organelles (Lysosome)
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Lysosome – A small circular organelle that
contains digestive enzymes.
A lysosome
acts like a
garbage
truck.
Important Organelles
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Mitochondria – Organelle that harvests
energy and makes ATP. “The powerhouse”
The
electric
company.
Comparing Plant and Animal Cells
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Plant cells contain everything that an
animal cell has plus some.
Animal cells are circular whereas
plant cells are rectangular.
Plant cells have three organelles that
are not present in animal cells.
- Cell Wall
- Chloroplasts
-Central Vacuole
Important Organelles
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Cell Wall – The structure that surrounds
the cell membrane and provide support for
the cell.
The cell
wall is like
a city wall.
Important Organelles
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Chloroplast – Organelle that uses light
energy to make carbohydrates from
carbon dioxide and water.
A chloroplast
again is like
the electric
company.
Important Organelles
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Central Vacuole – Cavity that is used for
storage. The central vacuole takes up the
most space of any organelle.
Self
storage
facility.