The History of the Cell Theory
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The Path to the Cell Theory
1500’s
First magnifying lenses used in
Europe to look at the quality of
cloth
1600’s
- First telescope and microscope
constructed in Holland
-
1665
Robert Hooke – used a microscope
to look at a thin slice of cork (bark
from an oak tree) and saw what
looked like small boxes
- First to name them cells (because
they looked like the small rooms
that monks lived in called “cells”)
1674
Anton van Leeuwenhoek – First to view
organisms from pond water using a
microscope
Advancements in Cell Biology and Imaging Quality
Cofounders of the Cell Theory
1838
1858
Matthias Schleiden – concluded
that all plants were made of cells
Rudolf Vichow –
Cells come from
pre-existing cells.
1839
Theodore Schwann – concluded that
animals were made of cells
The Basic Cell Theory
• All living things are composed of cells.
• Cells are the basic units of structure and function in living things.
• New cells are produced from existing cells.
Discoveries since the Cell Theory
• Endosymbiotic Theory
• In 1970, American biologist, Lynn Margulis, provided evidence that
some organelles within cells were at one time free living cells
themselves
• Supporting evidence included organelles with their own DNA
• Chloroplast and Mitochondria
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Modern Cell Theory
• With advancements and more studies in science the following
additions have been added onto the Cell Theory:
• Energy Flow occurs within cells.
• Metabolism
• Cells contain hereditary information that is passed on from cell to cell during
cell division
• DNA
• All cells are basically the same in chemical composition in organisms of similar
species.
The Cell Membrane:
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“Skin” that surrounds cell
Selectively permeable
Phospholipid bilayer
Many cell organelles have
membrane
Cytoplasm (Cytosol)
• The liquid inside the cell
• Helps to support cell
structures
• Provide protective buffer
Cytoskeleton
• gives a cell shape
• holds organelles inplace
• Lets cell move in space by
contracting and expanding
(microfilaments made of protein
actin).
• Holds organelles in place and
anchor nucleus (intermediate
filaments)
Mitochondrion
• The “powerhouse” of the cell
• Double-membrane
• Has its own DNA and ribosomes
• Use chemical energy from
primarily sugar to make the
energy for the cell to do various
metabolic tasks.
• The main molecule that provides
chemical energy is adenosine triphosphate (ATP).
NUCLEUS
• The control center of cell
• Source of genetic information
• Instructions for protein
production which controls cell
functioning.
• Almost always near center of
cell.
NUCLEOLUS
• Dark area in center of nucleus
• Makes materials for ribosomes
• Defective nucleoli evident in
Parkinson’s and Huntington’s
diseases.
Endoplasmic reticulum
• Attached to the nucleus by its
membranes.
• Two parts: the smooth
endoplasmic reticulum (SER) and
the rough endoplasmic reticulum
(RER).
• SER releases lipids, such as
hormones, that are used both in
the cell and in other cells.
• RER looks rough because it is
studded with ribosomes and
functions in making proteins.
Golgi Apparatus
• Modifies proteins by adding
signaling sugars onto surface of
protein.
• Unmodified protein arrives at
Golgi inside a transport vesicle.
• Fuses with Golgi and is modified
as it travels through Golgi
• Golgi membrane pinches off
with modified protein inside.
Golgi Apparatus
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Golgi Animation
Materials are transported from Rough ER to Golgi to the cell membrane by
VESICLES
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Protein Targeting & Disease
• Different types of proteins are
housed in different parts of the
cell where they can carry out
their specific functions.
• Other proteins are secreted.
• If proteins end up in the wrong
place or don’t get to the right
place this can lead to abnormal
cell function and/or serious
diseases.
Perioxisomes
• Vesicles that contain oxidative
enzymes
• Breaks down fatty acids, some
amino acids, and toxic hydrogen
peroxide.
• Look similar to lysosomes but
bigger
• Found near mitochondria and
chloroplasts while lysosomes can
be found anywhere in the cell.
Found in many Animal Cells - Centrioles
• Organize the spindle during cell
division.
• Consist of 9 groups of
microtubules; each group has
three microtubules.
• Therefore there are 27
microtubules in one centriole.
• Centrioles are always arranged
perpendicular to each other.
Found in many Animal Cells -Flagella
• 9 + 2 arrangement of
microtubules
• Used for cell movement
Found in many Animal Cells -Cilia
• Similar in structure to the flagella,
but they tend to be shorter
• 9 + 2 arrangement of microtubules
• Found in groups on the cell surface.
• In single-celled organisms, they
are used to move the cell.
• In the human body, used to move
substances across the cell surface
(e.g. cilia can be found on cells
lining the trachea. These cells help
to move mucus and trapped
particles away from the lungs.
Found in animal cells - Lysosomes
• Recycling centers of cell.
• Contain hydrolytic enzymes which
break nutrient particles into smaller
pieces so that other organelles can
use these fragments as a source of
energy.
• They destroy bacteria and organic
debris that enter cell from
extracellular fluid.
• Break down damaged organelles,
freeing components for re-use.
• Rarely found in plant cells because the
central vacuole fulfills the recycling
function in plant cells.
Found only in plant cells: Cell wall
• Surrounds the outside of a plant’s cell
membrane
• Attaches cells to neighboring cells.
• The wall is made of a rigid
polysaccharide called cellulose
• Gives plant cells shape and structure .
• It prevents cell from bursting when
too much water is available (e.g. rainy
seasons).
• Turgor pressure is pressure that water
puts on cell wall
Chloroplast
• Contains the molecule
chlorophyll.
• Traps light energy for the plant
and converts it to chemical
energy (sugar).
Found only in plant cells: Central Vacuole
• Found near the middle of the
cell.
• Stores water and other materials
in these storage tanks, keeping
them separate from cytosol.
• Central vacuoles perform the
same functions as lysosomes,
breaking down nutrients and
organelles into usable energy
components