A.Base
B.Pillar
C.Arm
D.Stage
E. Slide
F. Cover slip
G.Stage clip
H.Light source
I. Low power objective lens
J. High power objective lens
K. Body tube
L. Ocular (eyepiece)
M. Coarse adjustment knob
N. Fine adjustment knob
O. Nosepiece
P. Diaphragm
Chapter 7: Cells
Microscopes
•Magnification – increase of an object’s
apparent size
•Total magnification – mag. of eyepiece x
mag. of objective lens
Ex: (10X) x (4X) = 40X
•Resolution (resolving power) – the distance
needed to distinguish 2 points as separate
•Types of microscopes: compound light,
transmission electron, scanning electron
Compound light microscope:
•Specimen is enlarged as light
passes through set of glass
lenses
•Magnification – up to 2000X
•Resolving power – up to 200nm
•Can be used to view living
specimens
Transmission electron microscope:
•Electrons passing through a
specimen are brought into focus by a
set of magnetic lenses
•Image is projected onto a fluorescent
screen or photographic film; flat
image
•Magnification – up to 500,000X
•Resolving power – 0.2nm
•Cannot be used to view living
specimens
Scanning electron microscope:
•A narrow beam of electrons is scanned
over the surface of the specimen,
which is coated with a thin layer of
metal
•Metal gives off secondary electrons,
which are collected to produce a
picture of the specimen on the screen
•Magnification – up to 100,000X
•Resolving power – 1 nm
•Cannot view living specimen; 3D
image
Microscope images:
http://remf.dartmouth.edu/imagesindex.html
•
•
•
•
•
The Cellular Level of Organization
Living things are made of cells.
Living things may be unicellular or
multicellular.
Cells can be prokaryotic or eukaryotic
Cell structure is diverse (different shapes
& sizes based on jobs) but all cells share
common characteristics.
Organelles – tiny specialized structures
performing specific cellular functions
•First cells observed in 17th century by
Anton van Leeuwenhoek
•Term “cell” coined by Robert Hooke observing cork cells, reminded him of
cells (rooms) in a monastery.
•Observations by Matthias Schleiden,
Theodor Schwann, and Rudolf Vichow
contributed to the development of the
cell theory.
• The cell theory states:
1. All organisms are composed of one
or more cells.
2. Cells are the basic unit of structure
and function in organisms.
3. All cells come only from other cells.
Sizes of living things
Prokaryotic cells
• Include the bacteria and archaea; adapted to
live anywhere.
• Outer Boundary: Cell wall & plasma
membrane
– In some cells, wall is surrounded by a capsule or
slime layer
• Cytoplasm: Ribosomes, enzymes, &
thylakoids (in Cyanobacteria only – for
photosynthesis)
• Nucleoid: Region (not bound by a
membrane) where DNA is found on a single
chromosome
• Plasmids – small accessory rings of DNA
that may be found in bacterial cells
• Most bacteria have flagella composed of
the protein flagellin - for movement
• Some also have fimbriae (short
appendages) that help cells attach to
surfaces.
• Bacteria have a great metabolic diversity
– Can use any type of organic matter for
nutrients
– Are able to synthesize any needed molecules
given an energy source
Prokaryotes vs. eukaryotes
Prokaryotes Eukaryotes
Organisms
Bacteria
Protists,
Fungus,
Plants, &
Animals
Nucleus
No
Yes
Cell wall/membrane
Yes
Yes
Ribosomes
Yes
Yes
Other organelles
No
Yes
Cytosol
Yes
Yes
Cilia or
flagella
DNA
Cell
specialization
Prokaryotes
Eukaryotes
Yes
Yes
Single loop
in nucleiod
No
In nucleus
If multicelled
Evolution of the Eukaryotic Cell
• Organelles like nuclear envelope, ER, &
golgi apparatus may have appeared when
plasma membrane folded inward
• Endosymbiotic theory: eukaryotes arose
from a symbiotic relationship between
various prokaryotes.
• Flagella, mitochondria & chloroplasts were
taken in by a larger cell, yet not destroyed.
• Symbiotic relationship would have been
established within that larger cell (a
eukaryotic cell)
-Spirochete would become flagellum
-Heterotrophic bacteria became mitochondria.
-Cyanobacteria became chloroplasts.
-Would explain the following about
mitochondria & chloroplasts:
•Similarity to bacteria in size & structure
•Double membrane surrounding them
•Small amount of DNA found inside each
•Each contain own ribosomes resembling
those of bacteria
•RNA base sequence of their ribosomes
suggests prokaryotic origin
Evolution of the eukaryotic cell
Eukaryotic cells
• Have a nucleus that controls all cell
activities.
• Contain many cell organelles that
perform specific jobs.
• Organisms in the following kingdoms
are eukaryotic: Protists, Fungus,
Plants, and Animals
Plasma (cell) membrane – A
Nucleus*
Nuclear membrane – B
Nuclear Pore – C
Nucleolus – D
Chromatin – E
Cytoplasm*
Cytosol – F
Mitochondria – G
Golgi apparatus – H
Centriole – I
Cytoskeleton*
Microtubules – J
Microfilaments – N
Vacuole – K
Lysosome – L
Ribosome – O
Endoplasmic reticulum*
Rough ER – Q
Smooth ER - P
Plasma (cell) membrane – A Cytoskeleton*
Cell wall – B
Microtubules – M
Cytoplasm*
Microfilaments – N
Cytosol – C
Lysosome – O
Vacuole – D
Nucleus*
Chloroplast – F
Nuclear membrane – R
Golgi apparatus – I
Nuclear pores – S
Ribosome – J
Nucleolus (not shown)
Endoplasmic reticulum*
Chromatin (not shown)
Rough ER – K
Smooth ER – T
Mitochondria
•Plasma membrane:
•Surround all cells
•Made of phospholipids and proteins.
•Regulates what materials enter & leave
cell
• Cell wall:
–Found in plant cells in addition to
the plasma membrane.
–Protects and supports the cell
• Cytoplasm – area between the
nucleus and the plasma membrane
–Contains all cell organelles
• Cytosol - The fluid in-between the
organelles
Structure of the Nucleus
• Nucleus: stores genetic information
and controls metabolic activities
• Nucleus contains the following:
• Chromatin
• Nucleoplasm
• Nucleolus
• Nuclear envelope
• Nuclear pores
•Chromatin: DNA and protein
•Will coil to form chromosomes just before cell
division
•Nucleoplasm: semifluid material inside the
nucleus
•Nucleolus: Darkened region in chromatin
•Makes ribosomal RNA, which will leave
nucleus to form ribosomal subunits in
cytoplasm
•Nuclear envelope: Double membrane around
nucleus
•Nuclear pores: openings in nuclear membrane
to allow proteins into the nucleus and rRNA out of
the nucleus
Nucleus and nuclear envelope
Ribosomes
• Location where protein synthesis
occurs
• Ribosomes are composed of a large
subunit and a small subunit.
• Where ribosomes can be found:
– alone in the cytoplasm
– in groups called polyribosomes
– attached to the endoplasmic reticulum
• ER with ribosomes is called rough ER
•Ribosomes in cytoplasm:
•Proteins made here are used by
cell at structures such as
mitochondria and chloroplasts
•Ribosomes on ER:
•Proteins made here are eventually
sent out from cell or become part of
cell membrane
Ribosomes on ER
The Endomembrane System
• Consists of:
–Nuclear envelope
–Endoplasmic reticulum (ER)
–Golgi apparatus
–Vacuoles and Vesicles
• All parts are connected either directly
or through transport vesicles
Endoplasmic reticulum
• System of membranous channels and
saccules (flattened vesicles).
• Rough ER - has ribosomes
– Makes proteins that will be used outside
of the cell.
• Smooth ER - lacks ribosomes
– Site of synthesis of complex
carbohydrates and lipids, including
phospholipids
– Packaging of proteins into vesicles and
transported to golgi apparatus
The endoplasmic reticulum
Golgi apparatus
• Consists of a stack of curved saccules
(often compared to stack of plates).
• Receives vesicles (containing protein and
lipids from the smooth ER)
• Packages, processes, and distributes
them within the cell.
• Also involved in secretion – send vesicles
to plasma membrane where contents are
released
• Involved in formation of lysosomes.
The Golgi apparatus
Vacuoles and vesicles
•Both are membranous sacs in the cell that
store substances
•Vacuoles are large; vesicles are small
•Much larger in plants than in animals
•Plant vacuoles are typically filled with fluid
to give the cell added support – water,
sugars, salts, pigments (for color of flowers)
& toxins (for protection)
•In protists – contractile vacuoles pump out
excess water and digestive vacuoles break
down nutrients
Lysosomes
• Vesicles produced by the Golgi
apparatus.
• Contain enzymes.
• Involved in intracellular digestion
(even digesting worn-out cell parts).
• When cells bring in macromolecules
by vesicle formation at plasma
membrane, vesicle fuses to lysosome
and contents are digested
Energy-Related Organelles
• Chloroplasts – use solar energy to make
sugars - photosynthesis
• Mitochondria – break down sugars to
produce ATP – cellular respiration
Chloroplasts
• Belong to group of organelles called
plastids
• Found in plant cells
• Structure:
– Surrounded by two membranes
– Stroma - a fluid that contains enzymes.
– Thylakoids – sacs/discs inside the
stroma that contain chlorophyll (absorbs
solar energy)
– Grana - stacks of thylakoids
Chloroplast structure
Other examples of plastids:
•Amyloplasts – found in roots; store starch
•Chromoplasts – found in leaves; contain
orange & red pigments
•Elaioplasts - storage organelles of plants that
produce oils.
•Leucoplasts - basically colorless & may not
have specific functions.
•Etioplasts - develop when plants are grown in
the dark and have no chlorophyll; will become
fully functional chlorplasts with chlorophyll
when exposed to light.
****Don’t need to know any of these!!!****
Mitochondria
• Found in plant and animal cells.
• Structure:
– Surrounded by a double membrane
– Matrix – fluid that contains enzymes
– Cristae – folding of inner membrane –
increases surface area - increases space
on which cellular respiration can occur
Mitochondrion structure
Photosynthesis
•Only occurs in plants, algae, and
cyanobacteria
•Solar energy + carbon dioxide + water
 carbohydrate + oxygen
Cellular Respiration
•Occurs in all eukaryotic cells
•Carbohydrate + oxygen  carbon
dioxide + water + energy
Cytoskeleton
• Network of filaments and tubules that
extends from the nucleus to the plasma
membrane.
• Maintain cell shape & cause cell & its
organelles to move
• Constantly changing
• Contains:
– Microfilaments
– Microtubules
Microfilaments
• Thin protein threads that help give the cell
shape and enable the entire cell or parts of the
cell to move
• Play a structural role in intestinal microvilli
• Interact with motor molecules, such as myosin movement
Microfilaments
•
•
•
•
Microtubules
Long, hollow protein cylinders
Form rigid skeleton for the cell
Assist in moving substances within
the cell
Centrosome - microtubule organizing
center; controls microtubule
assembly
Microtubule structure
Centrioles
• Involved in cell
division
• Short cylinders
with a 9 + 0
pattern of
microtubule
triplets.
– Ring with 9 sets of
triplets & none in
the middle
•Only in animal cells
•Plants have centrosome, but no centrioles
within.
•Centrosome contains 2 centrioles at right
angles to each other
•Centrosome organizes microtubules within cell
•Roles in cell:
•Help in organizing spindle fibers (made from
microtubules)
•Direct organization of microtubules within
cilia and flagella.
Cilia and flagella
•
•
•
•
Involved in cell movement.
Cilia – small, numerous hairs
Flagella – large, single hair
9 + 2 pattern of microtubules – 9 sets of
doublet microtubules around 2 central
single ones
• Cilia and flagella move when the
microtubule doublets slide past one
another.
Plant vs. animal cells
Plant
Animal
Cell wall
Yes
No
Plasma membrane
Yes
Yes
Chloroplasts
Yes
No
Centrioles
No
Yes
Vacuoles
1 large central
one
Fewer
Several small
ones
more
Lysosomes