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Biology
Ch. 7
A View of
the Cell
CH. 7 A View of the Cell
I. The Cell Theory:
A. History
-
before 1600’s - fiber/tissue
thought to be the basic unit
of life
spontaneous generation
1. Robert Hooke (1665)
- observed cork cells
Robert Hooke (1665)
- Coined term ‘Cell’
2. Van Leeuwenhoek (1683)
- first to
see living
cells
Von Leeuwenhoek (1683)
- first to see living cells
3. Mathias Schleiden (1838)
- plants made
up of cells
4.Theodor Schwann (1838)
- animals made
up of cells
5. Rudolph Virchow (1855)
- cells come from
other cells
B. The Cell Theory
(3 parts):
1. All living things are made
of cells.
2. All cells come from
preexisting cells.
3. Cells are the basic units
of structure and function.
- developed over several hundred
years involving many scientists
- followed the development of
the microscope
Research Method: Light Microscopy
TECHNIQUE
RESULTS
(a) Brightfield (unstained specimen).
Passes light directly through specimen.
Unless cell is naturally pigmented or
artificially stained, image has little
contrast. [Parts (a)–(d) show a
human cheek epithelial cell.]
50 µm
(b) Brightfield (stained specimen). Staining
with various dyes enhances contrast, but
most staining procedures require that cells
be fixed (preserved).
(c) Phase-contrast. Enhances contrast
in unstained cells by amplifying
variations in density within specimen;
especially useful for examining living,
unpigmented cells.
(d) Differential-interference-contrast (Nomarski).
Like phase-contrast microscopy, it uses optical
modifications to exaggerate differences in
density, making the image appear almost 3D.
(e) Fluorescence. Shows the locations of specific
molecules in the cell by tagging the molecules
with fluorescent dyes or antibodies. These
fluorescent substances absorb ultraviolet
radiation and emit visible light, as shown
here in a cell from an artery.
50 µm
(f) Confocal. Uses lasers and special optics for
“optical sectioning” of fluorescently-stained
specimens. Only a single plane of focus is
illuminated; out-of-focus fluorescence above
and below the plane is subtracted by a computer.
A sharp image results, as seen in stained nervous
tissue (top), where nerve cells are green, support
cells are red, and regions of overlap are yellow. A
standard fluorescence micrograph (bottom) of this
relatively thick tissue is blurry.
50 µm
Micrograph of
a neuron and
dendrites using
antibodies,
fluorescent
proteins, and
confocal
microscope
Research Method: Electron Microscopy
TECHNIQUE
(a) Scanning electron microscopy (SEM). Micrographs taken
with a scanning electron microscope show a 3D image of the
surface of a specimen. This SEM
shows the surface of a cell from a
rabbit trachea (windpipe) covered
with motile organelles called cilia.
Beating of the cilia helps move
inhaled debris upward toward
the throat.
RESULTS
Cilia
Longitudinal
section of
cilium
(b) Transmission electron microscopy (TEM). A transmission electron
microscope profiles a thin section of a
specimen. Here we see a section through
a tracheal cell, revealing its ultrastructure.
In preparing the TEM, some cilia were cut
along their lengths, creating longitudinal
sections, while other cilia were cut straight
across, creating cross sections.
1 µm
Cross section
of cilium
1 µm
Light Microscopes vs. Electron Microscope
Light Microscope
Electron Microscope
Weak Magnification—up to 1000x
Strong Magnification—500,000x
Cheap
Expensive
Can look at living organism
Can only look at dead organism
Everything that lives is made of cells.
C. Two Basic Cell Types:
1. Prokaryotes:
- no nucleus nor organelles
- simple internal structure
- very small, primitive,
unicellular
- bacteria
Prokaryote
Bacteria Cell
2. Eukaryotes:
- have a nucleus and membranebound organelles
- complex internal structure
- animals, plants, fungi, protists
Eukaryote
Animal Cell
Eukaryote
Plant Cell
Prokaryotes vs Eukaryotes
Prokaryotes
Eukaryotes
Plasma membrane
Plasma membrane
Cytoplasm
Cytoplasm
Ribosomes (makes proteins)
Ribosomes(makes proteins)
DNA
DNA
Prokaryotes
Eukaryotes
No nucleus
nucleus
No membrane bound organelles
Membrane bound organelles
DNA is not associated with
proteins
DNA is associated with
protiens (histones)
DNA not in nucleus
DNA is in nucleus
II. Cell Structure
- 3 main parts of cells:
1. Plasma membrane
2. Nucleus
3. Cytoplasm
A.Plasma membrane:
1.Composition
- bilayer of phospholipids
embedded with proteins
- “fluid mosaic” theory
Plasma membrane
lipid
bilayer
proteins
Plasma membrane
Fibers of
extracellular
matrix (ECM)
Glycoprotein
Carbohydrate
Glycolipid
Microfilaments
of cytoskeletonCholesterol Peripheral
protein
Integral
protein
EXTRACELLULAR
SIDE OF MEMBRANE
CYTOPLASMIC SIDE
OF MEMBRANE
2. Function:
- holds cell together
- regulates movement of
molecules into or out of the
cell
3. Cell
Wall
- Prokaryotes (bacteria), fungi and
plants have a cell wall
- Animal cells do NOT have a cell wall.
- rigid, layered structure on the outside
of cells that protects and supports cell
- found on cells of plants, fungi, and
bacteria
- plant cell walls made of cellulose
Cell Wall
Membrane Proteins
Look at the oligosaccharide
Helps with cell to cell recognition
Peripheral proteins
Adhere temporarily
to the plasma
membrane
Regulate cell
signaling
Glycoprotein
Cell Receptor
Structure
Hormones
Cell attachment
Enzyme
Cholesterol
Maintains fluidity
-In the heat
keeps phospholipids
together
- In the cold
prevents phospholipids
from being to close to
each other. **prevents
rigidity.
Glycolipid
Provides energy
Serve as markers
for cell to cell
recognition
B. Nucleus:
- control center of the cell
- contains chromatin (DNA
“blueprint” for cell’s proteins)
Nucleus
End of 7.1 and 7.2 Notes
Stop studying here.
1. Nucleolus:
- makes ribosomes
2. Chromatin:
- active form of chromosomes
- long threads of DNA and
protein
C. Cytoplasm
- liquid interior of the cell
- mostly water with dissolved
substances
(O2,CO2, sugar,
etc.)
Cytoplasm
C. Cytoplasm
- contains Organelles:
tiny structures that carry
out specialized
functions
Organelles
Cytoplasm
D. Assembly, Storage,
and Transport
1. Ribosomes:
- where proteins are made in a cell
- found in both prokaryotes and
eukaryotes
2. Endoplasmic Reticulum:
- produces and
transports
molecules
3. Golgi Body:
- store, modify, and package
proteins,
hormones,
etc.
4. Vacuole:
- stores food, waste, sugar,
water, etc.
Stored food
or waste
Vacuole
5. Lysosome:
- digest food molecules or
worn-out
cells
6. Leucoplasts:
- store starch (plants only)
7. Chromoplasts:
- contain colorful pigments
(plants only)
E. Energy Transformations
1.Mitochondrion:
- "power house" of cells
1.Mitochondrion:
- site of cellular respiration
Glucose + Oxygen
C6H12O6 + O2
Energy + CO2 + H2O
2. Chloroplasts:
- site of
photosynthesis
in plant cells
2.Chloroplasts:
Sunlight + H2O + CO2
C6H12O6 + O2
F. Support and Locomotion
1. Cytoskeleton
- internal framework of cell
a. Microtubules
b. Microfilaments
- contractile proteins
- enable cells to move
2. Centrioles
- aid in the division of animal cells
3. Cell Locomotion
a. Cilia:
- short fibers, usually in
large number
b. Flagella:
- long fibers, usually single
or pairs
III. Cellular Transport
- molecules constantly enter
and leave the cell
A. Diffusion
- movement of molecules from
high concentration to low conc.
- until dynamic equilibrium
reached
- requires no cell energy (passive)
B. Osmosis:
- diffusion of water through a
selectively permeable membrane
C. Effects of Osmosis
1. Isotonic Solution
- concentration of solutes
the same on inside and
outside of cell
2. Hypotonic Solution
- solution outside of cell contains a
lower conc. of solutes than the
cell (more water)
a) Turgor pressure:
- pressure inside plant cells
a) Turgor pressure:
Leaves
and Onion
Epidermis
a) Turgor pressure:
Plant
Movements
from
Osmosis
b) Cytolysis:
- bursting of cells due to
increased osmotic pressure
c) Contractile Vacuoles:
- “pump” water out of cells of
paramecium, ameba, etc. living in
a hypotonic
solution
Paramecium
3.Hypertonic Solution
- solution outside of cell contains
a higher conc. of solutes than
the cell (less water)
a) Plasmolysis:
- loss of cytoplasm
(shrinking of the cell)
b) Wilting:
- loss of turgor in plant cells
D. Passive vs. Active
Transport
1. Passive Transport:
- requires no energy
a) Diffusion and Osmosis
b) Facilitated Diffusion:
- transport proteins in membrane
move sugar, amino acids, etc.
- follows concentration gradient
b) Facilitated Diffusion:
2.Active Transport:
- requires cell energy
a) Carrier proteins
transport molecules from
low. conc. to high conc.
using cell energy
Active Transport:
b) Endocytosis:
b) Endocytosis:
- movement of large amounts of
material into a cell by engulfing
and enclosing within a membrane
- forms a vacuole within cell
b) Endocytosis:
Ameba
c) Exocytosis:
c) Exocytosis:
- expelling large amounts of
material from the cell
c) Exocytosis:
Paramecium
The
End
Elodea Leaf Cells
Tomato Cells
Potato Cells
Human Epithelial Cells
Onion Cells- Unstained (40x)
Onion Cells- Stained (40x)
Bacteria Cells
Coccus
Bacillus
Spirillum
Von Leeuwenhoek (1675)
- first to see live cells