Transcript A View of the Cell

A View of the Cell
Chapter 7 Notes
Microscopes
 The
microscope was invented by
Leeuwenhoek.
 A compound light microscope
has a series of lenses and light.
 Electron microscope uses a
beam of electrons instead of
light. Can magnify objects up to
500,000 times their size.
The Cell Theory
 All
organisms are made of one
or more cells.
 The cell is the basic unit of
structure of organization of
organisms.
 All cells come from existing
cells.
The 2 types of Cells
Prokaryotes and Eukaryotes
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There are 2 types of cells.
Prokaryotic cells – these cells do not have a
nucleus, they do not have organelles attached
to the cell membrane. These are small cells.
Bacteria cells are prokaryotic cells.
Eukaryotic cells
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Eukaryotic cells – these cells do have a nucleus, they
do have organelles attached to the membrane.
These cells can be much larger than prokaryotic
cells.
An organelle is a specialized structure in a cell that
carries out a specific function. A “little organ.”
The Plasma Membrane

All cells are surrounded by a plasma
membrane.
 This is a flexible boundary between the cell
and its environment, to allow a steady
supply of nutrients to come into the cell no
matter the external conditions.
 The plasma membrane helps to maintain
homeostasis.
 It has selective permeability. A process in
which only certain molecules can pass
through the membrane and others are kept
out.
Structure of the
Plasma Membrane
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The plasma
membrane is
made up of a
phospholipid
bilayer.
 This is two layers
of phospholipid
molecules.
Plasma Membrane (cont.)
The membrane is referred to as a “fluid
mosaic.” This means it is not a rigid
membrane, it’s shape and form can
change and move.
 Cholesterol molecules throughout the
membrane help stabilize the
phoshopholipids and keep the fatty acid
tails from sticking together.
 Transport proteins are also found in the
membrane to move needed substances or
waste materials through the membrane.
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Cell Structures and Their Functions
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Some organisms have an
additional boundary
between the cell and the
environment. This is the
cell wall. Plants, fungi,
bacteria, and some
protists have cell walls.
Cell wall – a fairly rigid
structure located outside
the plasma membrane
that provides additional
support and protection.
Plant cells are separated by
transparent cell walls.
Nucleus
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The nucleus is the control
center of the cell. It contains
directions to make proteins.
The nucleus controls the
activities of the organelles.
The nucleus is surrounded
by a nuclear membrane.
Nucleolus – an organelle in
the nucleus that makes
ribosomes.
Micrograph of a cell nucleus
showing the darkly stained
nucleolus.
Cytoplasm
 The
cytoplasm is everything inside the cell
membrane and outside the nucleus.
 It contains most of the organelles for the
cell. It is the clear, gelatinous fluid inside a
cell.
Organelles and their Functions
 Endoplasmic
reticulum – the site of cellular
reactions.
 Rough endoplasmic reticulum – it is ER
with ribosomes attached to its surface.
 Ribosomes – carry out protein synthesis.
(they make proteins).
 Golgi apparatus – sorts and packages
proteins to be sent out to where they are
needed.
Nucleus, ER, and Golgi Apparatus
1.
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3.
4.
5.
6.
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Nucleus
Nuclear Pore
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Ribosome on rough ER
Proteins that are transported
Transport vesicle
Golgi Apparatus
Vacuoles and Lysosomes
Vacuole – a membrane
bound compartment
used for temporary
storage of materials.
(10) They are used to
store food, enzymes,
wastes, and other
materials.
 Lysosome – contain
digestive enzymes (12)
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Energy transformers
– cell organelles that capture
light energy and convert it to chemical
energy. Found in plant cells and some
protists. This is the site of photosynthesis.
 Mitochondria – membrane bound
organelles in plant and animal cells that
transform energy for the cell. Break down
chemicals and into usable forms.
 Chloroplasts
Organelles for Cellular Support
Cytoskeleton – forms a
framework for the cell. It
is a constantly changing
structure.
 Microtubules – thin,
hollow cylinders made of
protein that make up the
rods for the cytoskeleton.
 Microfilaments – small,
solid fibers that help
make up the cytoskeleton
 Centrioles – occur in
pairs, made of
microtubules, help in cell
division.
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Microtubules are green,
Microfilaments are red,
Nuclei are blue.
Organelles for Locomotion
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Cilia – short, numerous
hair-like projections that
aid in locomotion. Motion
is similar to that of oars
on a boat.
Flagella – a long, whiplike projection used in
locomotion. A cell can
have one or two flagella.
Unicellular organisms use
these a major means of
locomotion.
Flagella on e. coli bacterium.