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Who discovered cells?
• Robert Hooke was the first person
to use the term “cell” in 1665.
• He was using a microscope to
observe a thin slice of cork, he
called the dead chambers he saw
“cells”.
• Cells vary considerably in size. The smallest
cell, a type of bacterium known as a
mycoplasma, measures 0.0001 mm
(0.000004 in) in diameter; 10,000
mycoplasmas in a row are only as wide as
the diameter of a human hair. Among the
largest cells are the nerve cells that run down
a giraffe’s neck; these cells can exceed 3 m
(9.7 ft) in length. Human cells also display a
variety of sizes, from small red blood cells
that measure 0.00076 mm (0.00003 in) to
liver cells that may be ten times larger. About
10,000 average-sized human cells can fit on
the head of a pin.
Prokaryotic cells
• Smallest and simplest cells.
• Single-celled organism that lacks a
nucleus and other internal compartments.
• Cannot carry out many specialized
functions.
• First lived 3.5 billion years ago.
Example: bacteria
Eukaryotic cells
• Ten times larger than prokaryotic
cells.
• Organism whose cells have a
nucleus.
• Specialized
• Found 1.5 billion years ago.
• Some are single – celled.
The Cell Theory
• Formed after Schleiden, Schwann, and
Virchow’s observations of cells.
• Has three parts:
1. All living things are made of one or
more cells.
2. Cells are the basic units of structure
and function in organisms.
3. All cells arise from existing cells.
2 Types of Eukaryotic Cells
• ANIMAL
PLANT
Organelle
• Membrane bound compartments
inside cells.
• A structure that carries out
specific activities in the cell.
Cytoplasm
Semifluid that fills the cell. Composed of
about 65 percent water, the cytoplasm is
packed with up to a billion molecules per
cell, a rich storehouse that includes
enzymes and dissolved nutrients, such as
sugars and amino acids.
Cytoskeleton
• Microscopic fibers.
• Crisscrosses the cytoplasm, anchoring
the organelles in place and providing
shape and structure to the cell.
Cell Membrane / Plasma
membrane
All living cells have a cell membrane
that separates them from their
surroundings, much like the walls of
this
room separate us from the rest of the
school.
Characteristics of the Cell Membrane
1. Made up of lipids and proteins called a
phospholipid bilayer.
2. Acts as a barrier.
3. Controls what enters and leaves the cell.
(Selective permeability)
4. Sometimes called the fluid mosaic model
because it is not rigid.
The Cell Membrane
The Nucleus
• Controls almost all cell functions.
• Surrounded by a porous
double membrane called the
nuclear membrane or envelope.
• Large, dark structure.
The Nucleolus
• Found inside the nucleus.
• Composed of RNA and proteins that
are involved in ribosome formation.
• It can be thought of as the brain
because it contains the genetic
material.
Ribosomes
• Tiny bead like structures.
• Found in both prokaryotes and
eukaryotes.
• Manufacture proteins.
• Composed of both RNA and
proteins.
Endoplasmic Reticulum
• 2 types:
1. Rough ER 2. Smooth ER
• Serves as a transport system by moving
proteins and other substances through the
cell.
• The rough ER has ribosomes located on
its surface and the smooth ER does not.
Rough ER
The Golgi Apparatus
• Vesicles that contain newly made
proteins.
• Modifies, collects, packages and
distributes molecules after they are
made at the ER and other cell
locations.
• Flattened, membrane bound sacs.
The Golgi Apparatus
Lysosomes
• Small, spherical organelles that
contain the cells digestive
enzymes.
• They act as a clean up crew.
• They are like the toilet of the cell
because they digest waste
products.
Vacuoles
• Store materials like water, salt
proteins, and carbohydrates.
• Plant cells have a very large
central vacuole that is filled with
fluid.
Mitochondria
• Change the chemical energy stored in
food into compounds
the cell can use.
• Makes almost all of
the cells ATP.
• Sometimes called the
powerhouse of the cell.
Chloroplasts
• Found only in plant cells and algae.
• Use light energy (sun) to make
carbohydrates from carbon dioxide and
water that the mitochondria can use.
• Chloroplasts and mitochondria supply the
energy needed to power plant cells.
• Where photosynthesis takes place.
Chloroplast in onion cells:
• Chloroplasts, minute green,
spherical structures, are essential to the
process of photosynthesis, in which captured
sunlight is combined with water and carbon
dioxide in the presence of the chlorophyll
molecule to produce oxygen and sugars, which
can be used by animals. Without the process of
photosynthesis,
the atmosphere
would not contain
enough oxygen to
support animal life.
ANIMAL VS. PLANT CELLS
ANIMAL
PLANT
Cell membrane
Cell wall and cell
membrane.
Large central vacuole.
Chloroplasts that give
plants a green color.
PLANT CELL
ANIMAL CELL
Cell Specialization
• Occurs when cells change to perform
certain functions better.
• Sometimes called complex multicellularity.
Ex. Rod and Cone cells in your eye
are
specially adapted to allow you to
see
colors.
Cellular Organization
1. Cells – nerve cells, red and white blood
cells.
2. Tissues – distinct group of cells with similar
structure and function.
Ex. Muscles
3. Organs – tissues organized into a
specialized structure with a specific
function.
Ex. Heart
4. Organ System – various organs that carry
out a major body function.
Ex. Circulatory system
Cells and Homeostasis
• Homeostasis – when organisms make
internal adjustments based on external
changes.
• One way cells maintain homeostasis is
by controlling the movement of
substances across their cell
membranes.
• Sometimes this movement requires
energy (active transport) and
sometimes it does not (passive
transport).
PASSIVE TRANSPORT
• NO ENERGY REQUIRED!
• 2 Types
1. Diffusion – movement of
substances from an area of higher
concentration to one of lower
concentration in an attempt to
reach equilibrium.
2. Osmosis – diffusion of water
molecules through a selectively
permeable membrane.
ACTIVE TRANSPORT
• REQUIRES ENERGY!
• Particles move against the
concentration gradient.
• Involves carrier proteins found in the
cell membrane that act as “elevators”
or “carriers” of the material into the
cell.
Antoni van Leeuwenhoek
• Improved the simple microscope.
• Built over 240 microscopes.
• Discovered living creatures in pond
water which he called “animalcules”.
They were actually single-celled
organisms.
• 1st to discover and describe bacteria.
MICROSCOPES
• 2 common kinds:
1. Light microscope – light passes
through one or more lenses to produce an
enlarged image of a specimen.
2. Electron microscope – forms an
image of a specimen using a beam of
electrons rather than light.
Compound Microscope
• Light microscope that uses two lenses.
• Used to view living and small organisms.
Maximum magnification is 2000x
YOU NEED TO BE ABLE TO IDENTIFY
ALL THE PARTS OF A COMPOUND
MICROSCOPE!
Compound Microscope
Calculating magnification
• Multiply the power of the eyepiece (ocular)
by the power of the objective being used.
Ex. Eyepiece 10x
Objective 40 x
TOTAL MAGNIFICATION 400X
The Electron Microscope
• 2 Types
1. Transmission (TEM)– electron
beam is directed at a very thin slice of
specimen that has been stained. 2
dimensional picture. Magnify up to
200,000x. Always black and white.
2. Scanning (SEM)- 3 dimensional
image of the specimens surface only.
Specimen is coated in a thin layer of
metal. Magnify up to 60,000x.