Chapter 7: Cell structure
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
•Three types of microscopes: compound
light, transmission electron, scanning
electron
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
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 200,000X
•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 – 10 nm
•Cannot view living specimen; 3D
image
Microscope images:
http://remf.dartmouth.edu/imagesindex.html
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The Cellular Level of Organization
Living things are made of cells.
Living things may be unicellular or
multicellular.
Cell have different shapes & sizes
based on jobs.
Organelles – a structure that carries
out specific activities inside the cell
•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
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
•Cell membrane (plasma membrane):
•Cell’s outer boundary
•Regulates what materials enter & leave
cell
• Cell wall:
–Found in plant cells in addition to
the plasma membrane.
• Cytoplasm – area between the
nucleus and the plasma membrane
–Contains all cell organelles and
cytosol
• Cytosol - The fluid in-between the
organelles
Structure of the Nucleus
• Nucleus: stores genetic information
and controls cell activities
• Nucleus contains the following:
• Chromatin
• Nucleolus
• Nuclear envelope (nuclear
membrane)
• Nuclear pores
•Chromatin: DNA and protein
•Will coil to form chromosomes just
before cell division
•Nucleolus: Darkened region in nucleus
•Makes ribosomes
•Nuclear membrane: surrounds the
nucleus
•Nuclear pores: openings in nuclear
membrane to allow proteins into the
nucleus and rRNA out of the nucleus
Nucleus and nuclear membrane
Ribosomes
• Location where proteins are made
• Where ribosomes can be found:
–alone in the cytoplasm
–attached to the endoplasmic
reticulum
• ER with ribosomes is called rough
ER
Ribosomes on ER
Endoplasmic reticulum
• System of channels – helps transport
materials around the cell.
• Rough ER - has ribosomes; site of
protein synthesis
• Smooth ER - lacks ribosomes;
packages proteins and sends them to
the golgi apparatus
The endoplasmic reticulum
Golgi apparatus
• Often compared to stack of
plates.
• Modifies, sorts, and packages
proteins for distribution.
The Golgi apparatus
Vacuoles
•Stores substances in cell
•Much larger in plants than in
animals – plants make own food
and need to store it for times
when they cannot make food
•Plant vacuoles are typically filled
with fluid to give the cell added
support
Lysosomes
• Produced by the Golgi apparatus.
• Contain enzymes.
• Involved in digestion (even digesting
worn-out cell parts).
• When cells bring in food at plasma
membrane, small vacuoles they are
stored in fuse to lysosome and
contents are digested
• Chloroplasts – use solar energy to make
sugars – photosynthesis; found in plants
• Mitochondria – break down sugars to
produce energy (ATP) – cellular respiration;
found in plants & animals
Chloroplast structure
Mitochondrion structure
Cytoskeleton
• Made up of microfilaments &
microtubules
• Maintain cell shape
• Helps cell move
• Helps cell organize its parts
• Constantly changing
Centrioles
•Only in animal cells
•Roles in cell:
•Help with cell
division
•Help with formation
of cilia and flagella.
Cilia and flagella
• Cilia - small and numerous
• Flagella - large and single
• Involved in cell movement.
Plant vs. animal cells
Plant
Animal
Cell wall
Yes
No
Plasma
membrane
Chloroplasts
Yes
Yes
Yes
No
Centrioles
No
Yes
Vacuoles
1 large central
one
Several small
ones
Organisms can be any of the following:
•Unicellular organisms
•Multicellular
•Colonial
Paramecium
E.Coli bacteria
•Unicellular organisms
•Entire organism is 1 cell
•No specialization – 1 cell does all jobs
for the organism
•Ex: some bacteria, protists and fungi
•Multicellular organisms
•Organism is composed of more than
1 cell
•Cells are specialized – have distinct
jobs; are dependent upon one another
•Ex: All plants & animals, most fungi &
some protists
Mushroom
Lily
Giraffe
Ulva
•Colonial organisms
•Cells live as a connected group, but
do not depend on one another for
survival
•Ex: Some bacteria, protists
Slime molds
Volvox
Bacteria
Levels of cellular organization (in multicellular
organisms):
•Cells  tissues  organs  organ systems
•Tissue – distinct group of cells that have similar
structures and functions
•Ex. in plant: vascular tissue – helps carry
nutrients to various parts of plant
•Ex. in animal: muscle tissue – helps in
movement
Vascular tissue
Cardiac muscle
•Organs – a collection of tissues that carry out
a specific function in the body
•Ex. in plants: leaf (made of vascular tissue
and other tissues that work together to trap
sunlight and produce sugar)
•Ex. in animals: heart (made of muscle,
nerve, and other tissues that work together
to pump blood)
Leaf
Heart
•Organ systems – made up of various organs
that carry out a major body function
•Ex. in plants – shoot system (consists of
stems, leaves, and the vascular tissue that
connects them)
•Ex. in animals – circulatory system (made
up of the heart, blood vessels, and blood)
Shoot system
Circulatory system
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 cytoplasm
No
In nucleus
If multicelled