Download The Cell

I. The Cell- The basic unit of structure and function in
all living things. Cells are open systems that require an exchange
of materials with their surroundings. Evolution is the basis for the
correlation of structure and function
A. How Cells are Studied
1. Light Microscope- light is refracted through
lenses, magnifying the image. Resolution is limited
to by the wavelength of visible light. Effective
magnification is about 1500 X
a) Magnification- how
large an image appears
b) Resolution- measure
of the clarity of the
image
2. Electron Microscope- focuses a
beam of electrons through the specimen. Resolution
is inversely related to the wavelength of radiation a
microscope uses. Best resolution is about 0.2nm
a) TEM- transmission
electron microscope shoots
beams of electrons through a
specimen. Used to view
internal structure
b) SEM- scanning electron
microscope shoots electrons off
the surface of objects that have
been coated in gold. Used to
study surfaces of specimen
Which is the SEM and which is the TEM?
3. Cell Fractionation- technique
used to study cell parts called organelles
a) Cells are homogenized by
disrupting the cell membrane
b) The remaining liquid is
placed in a centrifuge- a
spinning device which will
separate materials according to
size
B. Types of Cells:
Prokaryotic Vs. Eukaryotic Cells
1. Prokaryotic Cells
• small cells with no
true nucleus and
membrane bound
organelles.
• Examples: Bacteria
and Blue-green
algae
2. Eukaryotic Cells- Cells that have a
nucleus and membrane bound organelles.
Plant
Animal
Fungus
Protist
C. Cell Size
1. Cells have a wide range of sized
A) Mycoplasma: 0.1-1.0 μm
B) Most bacteria: 1 to 10 μm
C) Most Eukaryotic cells: 10 to 100 μm
2. Cell size limitations
A) Based on the ability of the cell to obtain
oxygen, nutrients and to get rid of wastes.
B) Surface area to volume ratios are extremely
important
Surface Area Vs. Volume
Surface Area (Cell
membrane)- place where all
oxygen, food and wastes
must enter and exit the cell
Volume (cytoplasm)substance that uses up food,
oxygen and produces waste
Sammy Cell
Surface area = length X width X number of sides
Surface area = 1 μm X 1 μm X 6
1 μm
1 μm
Surface area = 6 μm2
1 μm
Volume = length X width X height
Volume = 1 μm X 1 μm X 1 μm
Volume = 1 μm3
Surface Area to Volume Ratio = 6 : 1
Cell Double Size
Surface area = 2 μm X 2 μm X 6
2 μm
2 μm
2 μm
Surface area = 24 μm2
Volume = 2 μm X 2 μm X 2 μm
Volume = 8 μm3
Surface Area to Volume Ratio = 3 : 1
Cell Triples Size
Surface area = 3 μm X 3 μm X 6
3 μm
Surface area = 54 μm2
Volume = 3 μm X 3 μm X 3 μm
3 μm
3 μm
Volume = 27 μm3
Surface Area to Volume Ratio = 2 : 1
3. As a cell grows, its need for oxygen increases
faster than its ability to get oxygen. So the cell
must divide or suffocate
3. The Importance of
Compartmental organization
A) Eukaryotic Cells are surrounded by a
plasma membrane and are partitioned
into organelles which provide correct
environments for specific metabolic
processes
B) Many enzymes are built into the
membranes
E. Organelles of the Eukaryotic Cell
1. Nucleus- organelle responsible for the
control of all cellular processes
A) A nuclear envelope determines what materials enter
and exit the nucleus through the nuclear pores
B) In the nucleoplasm are a set number of chromosomes
composed of tightly coiled strands of DNA
C) Segments of DNA that are responsible for the
production of a protein are called genes, which
produce m-RNA
D) While the cell is not dividing, loose strands of DNA
appear grainy and are called chromatin
E) Nucleolus- dark spherical structure in the nucleus that
is rich in RNA and is responsible for the production of
ribosomes
Nuclear membrane
Nuclear pore
Chromatin
Nucleolus
Chromosomes
Chromosome Vs Chromatin
DNA Packing
2. Endoplasmic Reticulum- network of
internal membranes extending through the cell
a) The ER transports materials in the cell
b) Cisternae, flattened sacs where the
ER has expanded, may serve as a
storage area for important substances
c) lipids, proteins and complex
carbohydrates are also synthesized
in the ER
d) Smooth ER (SER) produces
steroids, stores calcium and
detoxifies certain poisons
e) Rough ER (RER) ER with ribosomes
3. Ribosomes The site of protein synthesis
a) Polyribosomes- clusters of 5or 6 ribosomes working
together to produce a protein
b) Ribosomes are assembled in the nucleus and then enter the
cytoplasm where they may attach to the RER or float free
4. Golgi Apparatus- layers of plate-like membranes
which store and package cell products usually for transport out of
the cell
a) During storage, some materials are
modified
b) Proteins are packaged in a sac
made from the membrane. The sacs
are called secretory vessicles
5. Lysosome- golgi vesicle containing digestive
enzymes that fuse with vacuoles and digest food
a) Lysosomes fuse with food vacuoles to hydrolize proteins,
polysaccarides and nucleic acids
b) Autophagy- digesting cell components for fuel
Organelles work together to carry out life
processes
6. Mitochondria-
power plant of the cell in which
most of the reactions of cellular respiration occur
a) Regulates calcium concentrations in the cell
b) A double folded membrane of lipid bilayers is folded repeatedly
into cristae (the center of mitochondrial activity)
c) The matrix is the fluid that contains the enzymes for respiration
7. Plastids- organelles found only in plant
cells that are involved in the synthesis or storage of
food
a) Chloroplast- contain
chlorphyll and carotenoids
which trap light energy for
photosynthesis
b) Leucoplast- plastid
used in the storage of
starch and other materials
c) Chromoplast- contains
pigments that give flowers
and Fruits their characteristic
colors
Chloroplast
8. Peroxisomes- membranous sacs
that contain oxidative enzymes
A) Fatty acid oxidation occurs in
peroxisomes
B) Peoxisomes carry on metabolic
reactions which break down H2O2
C) Detoxify compounds such as
ethanol
D) Involved in photorespiration in
plants
E) Glyoxysomes convert fatty acids to
sugars in young plants
9. Microtubules
• Hollow, spirally
arrange tubes with
walls of tubulin
protein
• Provide structural
support and may have
a role in cellular
movement
10. Microfilaments Solid rod-like structure
consisting of the contractile proteins actin and mysosin.
Responsible for cell movement
11. Microtrabecular lattice- 3 dimensional
interlinked microfilaments that form the
Cytoskeleton or framework of the cell
12. Centrioles- hollow cylinder composed
of nine triple microtubules that function in
cell division.
a) Anchor spindle fibers during cell division
b) Centrioles are located within a dense area of
cytoplasm called the centrosome near the nucleus
13. Vacuoles- membrane bound area for
digestion, storage or waste disposal. The
surrounding membrane is called the tonoplast
14. Cilia and Flagella- specialized
microtubules used for movement
a) Cilia usually occur in
large numbers on the cell
surface with a 9+2 pattern of
microtubles. Cilia work
together like oars on a boat
b) Flagella- much longer and
fewer in number. 9+2
arrangement. Flagella
undulate or wiggle to produce
movement
E. Motor Molecules- convert
ATP to movement
1. Kinesin- attaches to a vesicle at a receptor
and “walks” along a microtubule
2. Dynein- side arms of dynein on microtubules
of cilia and flagella crawl along neighboring
microtubules causing them to bend
3. Actin and Myosin- interacting threads of
myosin pull themselves along actin causing
muscle contraction or other movement.
E. The Cell Surface
1. Cell Wall- structure in plant, fungus,
bacteria and some protists that provides strength
and structure to a cell
2. Glycocalyx- fuzzy coat of
oligosaccharides on the outer surface of some
animal cells
A) Provides strength to the cell membrane
B) Helps join one cell to another
3. Intercellular Junctions
A) Tight junctionsmembranes of
neighboring cells are
joined
B) Desmosomes- rivit-like
areas that anchor cells
together
C) Gap junctions-contain
channels between
adjacent cells