Transcript Cell Theory and Organelles

Part 1: The Cell Theory
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The Discovery of the Cell
In 1665, Robert Hooke used an early microscope to look at
a thin slice of cork, a plant material.
Cork looked like thousands of tiny, empty chambers.
Hooke called these chambers “cells.” (THINK PRISON
CELLS)
Cells are the basic units of life.
Hooke’s Drawing of
Cork Cells
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• Anton van Leeuwenhoek used a
microscope to observe tiny organisms
(microorganisms) in pond water
The Cell Theory
In 1838, Matthias Schleiden concluded that all plants were
made of cells.
In 1839, Theodor Schwann stated that all animals were
made of cells.
These conclusions led to the first two parts of the cell
theory:
1) All living things are composed of cells
2) Cells are the basic unit of structure and function
in living things
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The Cell Theory
In 1855, Rudolph Virchow concluded that new cells
were created only from division of existing cells.
This led to the third part of the cell theory:
3) New cells are produced from existing cells
Exploring the Cell
Electron Microscopes
Electron microscopes reveal details 1000 times smaller
than those visible in light microscopes.
Electron microscopy can be used to visualize only
nonliving, preserved cells and tissues.
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Exploring the Cell
Transmission electron microscopes (TEMs)
• Used to study cell structures and large protein
molecules
• Specimens must be cut into ultra-thin slices
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Exploring the Cell
Scanning electron microscopes (SEMs)
• Produce three-dimensional images of cells
• Specimens do not have to be cut into thin slices
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Exploring the Cell
Scanning Electron Micrograph of Neurons
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Prokaryotes and Eukaryotes
Cells come in a variety of shapes and sizes.
2 Types: Prokaryotic and Eukaryotic
All cells:
– are surrounded by a barrier called a cell
membrane.
– at some point contain DNA.
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Prokaryotes and Eukaryotes
Cells are classified into two
categories, depending on whether
they contain a nucleus.
The nucleus is a large membraneenclosed structure that contains the
cell's genetic material in the form of
DNA.
The nucleus controls many of the
cell's activities. (The Brain of the
Cell!)
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Eukaryotes are cells that contain nuclei.
Prokaryotes are cells that do not contain
nuclei.
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What are the characteristics of
prokaryotes and eukaryotes?
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Prokaryotes
Prokaryotic cells have genetic material that is
not contained in a nucleus.
•Prokaryotes do not have membrane-bound
organelles (cell parts surrounded by
membrane).
•Prokaryotic cells are generally smaller and
simpler than eukaryotic cells.
•Example Organism: Bacteria
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Eukaryotes
Eukaryotic cells
contain a nucleus
in which their
genetic material is
separated from the
rest of the cell.
Eukaryotic cells
generally contain
dozens of cell parts
(organelles) and
internal membranes
They are generally
larger and more
complex than
prokaryotic cells.
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• Cells contain
internal structures
called organelles
• Organelles carry
out specific
functions for the
cell (like organs in
the body!)
•Many eukaryotic cells are highly specialized (Ex: leaf
cells in plants, nerve cells, muscle cells)
•Example Organisms: Plants, animals, fungi, and
protists are eukaryotes.
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Just for Fun
Guess the cell type for each cell:
Options are:
plant cell, neuron (nerve cell), skin cell,
sperm cell, bone cell, bacterium, blood
cell, muscle cell
#2
#1
#3
#4
#5
#6
#7
#8
How are Cells Different From Each
Other?
1) Size
2) Shape
3) Internal Organization
Fun Fact: In the human body, there are at
least 200 different cell types!
Size
• Big Enough for the Unaided Eye?
Example: Giraffe Nerve Cells (2 Meters)
• Small Enough to Need a Microscope?
Examples:
1) Plant / Animal Cells (10-50
Micrometers)
2) Bacteria (0.2 Micrometers)
Shape
• Remember: Form Follows Function!
Question: How does the shape of these
cells help them perform their functions?
Part 2: Eukaryotic Cell
Structures
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Review
• Organelle: A cell component that
performs specific functions for the cell
• Cell biologists divide the eukaryotic cell
into two major parts: the nucleus and the
cytoplasm.
• The Cytoplasm is the portion of the cell
outside the nucleus.
Cytoplasm
• Definition: The region of a cell between
the cell membrane and the nucleus
• Contains a variety of organelles in a jellylike, watery fluid called the cytosol
Cell Membrane
• Also called the plasma
membrane
• A barrier that surrounds the
cytoplasm
• Separates the inside of cells
from the outside environment
• Regulates passage of
materials into and out of the
cell
• Found in both plant and
animal cells
Nucleus
The nucleus is the control
center of the cell.
The nucleus contains
nearly all the cell's DNA
and with it the coded
instructions for making
proteins and other
important molecules.
Red = Nucleus
Green = Nucleolus
Ribosomes
One of the most important jobs carried
out in the cell is making proteins.
Proteins are assembled on ribosomes.
Ribosomes are small particles of RNA and
protein found throughout the cytoplasm.
Endoplasmic Reticulum
• A system of
membranous
tubes and sacs
• Used to make
proteins and as
a “highway for
cell materials”
Rough ER
Smooth ER
Structure
Has Ribosomes
No Ribosomes
Function
Makes Protein
Regulates calcium
level in muscle,
makes steroids in
glands, breaks
down toxins in liver
Golgi Apparatus
• Function: the processing and packaging
organelle; works with the ER; modifies
proteins to be sent out of the cell
• Structure:
1) System of membranes
2) Flattened sacs
Lysosomes
• Structure: small, spherical
organelles that enclose
hydrolytic enzymes within
single membranes
• Function: these enzymes
can digest carbs, lipids,
DNA, RNA, old organelles,
viruses, bacteria
• Not found in plant cells or
prokaryotes
• Role of lysosomes in
development?
Mitochondria
• Function: powerhouse of
the cell; produces energy!
• Structure: 2 membranes,
have their own DNA
• Question: In what types of
cells would mitochondria
be the most numerous?
Chloroplasts
• Function: the organelles in a plant cell in
which the energy of sunlight is converted
into chemical energy (photosynthesis)
• Structure: 2 membranes, contains DNA,
chlorophyll (green color!)
Vacuole
• Found in plants and
animals
• Large central
vacuole in plant cells
• Function: fluid-filled
organelle that stores
enzymes and wastes
Cell Wall
• Not found on animal
cells; on plant cells and
bacteria
• Function: supports and
protects the cell
• Structure: cellulose,
pores
Cytoskeleton
• Function: a structure to
maintain the shape and
size of cells (like our
skeletons!)
• Structure: a network of
long protein strands
located in the cytosol; 2
types
1) Microfilaments
(thinner)
2) Microtubules
(thicker)
Cilia / Flagella
• Structure/Function: hair-like organelles
that extend from the surface of the cell,
where they assist in movement
• Made of microtubules!
• Differences between cilia and flagella