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Cells Overview
Chapter 3 for Anatomy
Chapter 7 for Biology
Life is Cellular
A cluster of neural cells were derived from human
embryonic stem cells in the lab. The motor neurons are
shown in red; neural fibers appear green and the blue
specks indicate DNA in cell nuclei.
Microscopes
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Mid 1600s
1665 Robert Hooke
1st Compound Microscope
After looking at Cork
Saw cambers called Cells
Anton Van Leeuwenhoek
Pond water (animalcules)
Cork Cells / Microscopic Animals
• Cork Cells at 100X Magnification / Plankton have limited powers of
locomotion
Scanning Electron Microscope
• SEM is a type of electron microscope that images the samples
surface by scanning it with a high-energy beam of electrons.
Transmission Electron Microscope
• TEM uses a beam of highly energetic electrons to examine objects
very closely, on a fine scale. A TEM shines a beam of electrons
through an object.
Scanning Probe Microscope
• SPM is a branch of microscopy that forms images of surfaces using
a physical probe that scans the specimen.
Cell theory
• All organisms are comprised of more than
one cell
• Cell is the basic unit of life
• All cells come from preexisting cells
What is an organelle?
Membrane bound structures with particular
functions within eukaryotic cells
Types of Organelles
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Nucleus
Cell membrane
Ribosomes
Endoplasmic reticulum
Golgi Apparatus
Lysosomes
Vacuoles
Mitochondria
Chloroplast – Plants only
Cell wall – plants only
Cytoskeleton
Bacteria
cell
Cell Wall
• The rigid cell wall of
plants is made of fibrils
of cellulose embedded in
a matrix of several other
kinds of polymers
• Bacteria cell wall is
made up of
polysaccharides and
protein.
Chloroplast
• Captures light energy in plants and
produces ATP and reduce NADP to
NADPH through a complex set of
processes called photosynthesis.
Endoplasmic Reticulum
• Synthesis of protein and lipids
– Rough ER – protein synthesis – can exsist in
cytoplasm
– Smooth ER – lipid synthesis
Ribosomes
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Sites of protein synthesis
Scattered throughout cytoplasm
Comprised of protein and RNA molecules
Provide structural support for RNA during
protein synthesis from amino acids
Golgi Bodies
• Composed of six flattened membranous
sacs
• Packages and delivers proteins
synthesized by ribosomes
• Proteins arrive at this spot in vesicles,
where glycoproteins are to be received
Golgi Bodies
• They pass through one end and continue
to pass over the sac until the protein is
chemically processed
• When the altered glycoprotein reaches
outermost layer, then bubblelike structures
form and move throughout the cell
membrane – exocytosis
Mitochondria
• Elongated fluid filled sacs
• Move slowly through cytoplasm and
reproduce by dividing
• Has inner and outer layers
Mitochondria
• Inner layer has cristae that control some
chemical reactions, through enzymatic
processes
• Chemical reactions release energy
• Major site of ATP production – energy for
the cell
Lysosome
• “garbage men” of the cell
• Membranous sacs
• Powerful enzymes that breakdown nutrient
molecules or foreign particles
• In blood cells – can destroy bacteria
• In cells in general – can breakdown dead
cell parts
Microfilaments
• Tiny rods of actin protein that form
meshwork or bundles
• Provide cell mobility
• In muscle cells – they aggregate to form
myofybrils, which help the cells to contract
Microtubules
• Long slender tubes with diameter two to
three times that of microfilaments
• Composed of globular tubulin proteins –
9+2 array (9 outside, 2 inside)
Centrosome
• Structure near Golgi Apparatus and
nucleus
• Consists of two hollow cylinders called
centrioles
• Lie at right angles and distribute
chromosomes evenly to new cells during
mitosis.
Cilia
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Motile extensions from certain cells
Comprised of microtubules in 9+2 array
Tiny hairlike structures
Move to and fro, in succession, so that
there is a wavelike motion
Flagella
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Motile extensions from certain cells
Comprised of microtubules in 9+2 array
A cell will only normally have one flagellum
Swim motion
Vesicles
• Or vacuoles
• Membranous sacs formed by part of the
cell membrane folding inward and pinching
off
• Material outside the cell is now inside and
in the cytoplasm
Cell Nucleus
• Houses genetic material
• Enclosed in a double layer nuclear
envelope – inner and outer lipid bilayer
membranes
• Protein-lined channels called nuclear
pores that allow for certain molecules to
exit
Nucleolus
• Small dense body composed largely of
RNA and protein
• No surrounding membrane
• Forms in specialized regions of certain
chromosomes
• Ribosomes form in the nucleolus and
move through nuclear pores to the
cytoplasm
Chromatin
• Loosely coiled fibers of DNA and proteins
= chromosomes
• DNA = information for protein synthesis
• Beginning of cell division – chromatin coil
tightly and individual chromosomes
become visible
Cell Membrane Structure
• A phospholipid consists of a
– polar portion, called the head,
– two longer fatty acids, called the tail.
Cell Membrane Structure
http://www.mhhe.com/biosci/esp/2002_general/Esp/default.htm
When mixed with water, the heads are attracted to the
polar water molecules.
The nonpolar tails move as far from water as possible,
and a double layer of phospholipids with tails to the
interior results.
Phospholipid bi-layer of a cell
membrane