Transcript Cell Structure and Function - Tri

Cell Structure and Function
Bio 100
Tri-County Tec. College
Pendleton, S. C.
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Tools to observe cells-
Microscopes
– light
– transmission electron
– scanning electron
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Each has a unique value to the person
studying cells.
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The Light Microscope
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uses visible light for illumination
magnifies to 1000x (some to 2000x)
good for looking at most cells
living cells can be observed
not good for looking at cell parts
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Two important concepts
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Magnification defined as “how much
larger/bigger the object appears”
Calculated by multiplying the objective
by the ocular (40X objective x 10X
ocular = 400 X magnification)
Resolution is the ability of a
microscope to show two objects as
distinct or separate from each other
Catch 22 to be sure
Chalk talk time on resolution
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Transmission Electron Micros.
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electron beam for illumination
magnifies 100,000x or more
specimen has to be dead and cut into
thin sections
good for observing cell parts
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Scanning Electron Micros.
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electron beam for illumination
can visualize 3D surfaces of whole
specimens
specimen must be dead
good for looking a surface architecture
of cells
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Let’s Review Cell Theory
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The cell is the structural and functional
unit of life
Whatever “life” is, it begins at the
cellular level
All living things are composed of one or
more cells
Cells can only come from preexisting
cells
Another Catch 22 is spontaneous
generation versus biogenesis
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The Cell Membrane
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Composed of a phospholipid bi-layer
with proteins embedded in it
fluid-mosaic model
– proteins are randomly distributed in the
membrane (mosaic)
– proteins are not static in position (fluid)
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membrane contains pores
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Cell Membrane, ctd.
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movement of materials through pores
– if smaller than the pores
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lipid soluble substances
– dissolve in the membrane and move in on
the other side
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the membrane is selectively permeable
carrier proteins
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Organelles of the cell
“little organs” that carry out the
functions of the cell
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Endoplasmic Reticulum
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Looks like a maize in the cytoplasm
smooth endoplasmic reticulum (SER)
– does not contain ribosomes
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rough endoplasmic reticulum (RER)
– contains ribosomes
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system of channels for internal cellular
transport
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Golgi Apparatus
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Looks like a stack of pancakes
usually near the ER
packages cellular secretions for export
from the cell
In some cells, hormones are produced
in the ER and the Golgi Apparatus
packages these for export.
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Ribosomes
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Some are located in ER
others float free in cytoplasm
both kinds are the places where
proteins are synthesized
composed of RNA (ribosomal-RNA)
protein synthesis takes place in the
cytoplasm
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Mitochondria
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Sites of energy production (ATP
synthesis via cellular respiration)
use oxygen to produce ATP
shaped somewhat like a peanut
reactions of energy production take
place on numerous membranes that
form the inside of the mitochondrion
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Centrioles
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form the structures that are involved in
pulling the chromosomes apart during
cell division.
each cell has two
line up at opposite ends of a dividing
cell and establish the direction at which
division will take place
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Nuclear Organelles
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located in or associated with the
nucleus
– nuclear membrane
– chromatin
– nucleolus
– chromosomes
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nuclear membrane
– controls what enters and exits the nucleus
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Nuclear Organelles--2
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Chromatin
– stretched out chromosomes
– long, thin strands of DNA
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Nucleolus
– looks like a small nucleus inside the
nucleus
– synthesizes ribosomes
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Nuclear Organelles--3
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chromosomes
– before cell division chromatin condenses
into chromosomes
– composed of DNA
– genes are locations on a chromosome that
contain directions for making a specific
human protein
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Cytoskeletal Elements
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Microtubules and microfilaments
microtubules
– hollow cytoskeletal elements
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microfilaments
– solid cytoskeletal elements
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support the cell from the inside
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Organelles of Locomotion
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Cilia and flagella
flagella
– long, whiplike structures that cause certain
cells to move
– human sperm cell has a flagellum
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cilia
– short structures that move materials over
the surfaces of certain human tissues
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Inclusions
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storage areas in the cell
somewhat like closets
surrounded by a membrane
usually spherical in shape like a beach
ball
plant cells usually have more inclusions
than do animal cells
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Lysosomes
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Lysosomes
–membranous sacs of powerful
digestive enzymes
–digest worn out cell parts and
foreign matter in the cytoplasm
–“garbage collectors” of the cell
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Peroxisomes
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membranous sacs of oxidizing enzymes
detoxify poisons by oxidation
cells produce hydrogen peroxide which
is a poison
peroxisomes destroy hydrogen peroxide
“detox” centers
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Chloroplasts
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Found only in plant cells
location for photosynthesis
– production of glucose from carbon dioxide
and water
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contain chlorophyll (a and b)
Also contain carotenoids and
phycobilins
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Meanwhile, back at the ranch..
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Plant cells joined together into tissues
by cell junctions
Sticky middle lamella cements adjacent
cells together
Each plant cell connected to adjoining
cells by plasmodesmata
Tiny channels that allow cytoplasm to
be continuous between the cells
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Extracellular Matrix
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Animal cells have elaborate ECM composed
mostly of glycoproteins
Tight junctions=continuous belts around cells
(membranes of neighboring cells fused at
tight junctions)
Anchoring junctions (desmosomes)=rivets
fastening cells together into strong sheets
Communicating junctions (gap)=provide
cytoplasmic channels between adjacent cells
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Eucaryotic vs. Procaryotic
One is complex, the other is
simple.
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Procaryotic Cell
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simple, unorganized cell
no membrane-bound organelles
no nuclear membrane
– no nucleus
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division by binary fission r/t mitosis
small simple ribosomes
examples: bacteria (K. Procaryotae)
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Eucaryotic Cell
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complex, well organized cell
membrane-bound organelles
nuclear membrane
division involves mitosis
the kind of cell we are composed of and
that we have been discussing
members of all other kingdoms
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The End
The language of the cell is
a key to understanding the
science of Biology.
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