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A Tour of the Cell
Chapter 4
Cell Organelles
Wakefield
2015
Cells
• Made primarily of H, O, C,
&N
• Though it also needs trace
elements
• Contains about 60% water
• Extracellular and Interstitial
• Main solid consists mainly of
proteins
Macromolecule Structure
Carbohydrate – C, H, O
Protein – C, H, O, N
Lipid – C, H, O, P
Nucleic Acids – C, H, O, N
Water – H, O
Cells
• Cells are very diverse
• Vary in length
• 2 micrometers to more than
3 feet
• Structure defines its
function which are also very
diverse
Microscopy
• Resolution
• A measurement of the clarity of the image
• The minimum distance between 2 points
• Magnification
• A ratio of an object’s image size to its real size
• Contrast
• The difference in brightness between the light and dark areas of an image
Cells
• Robert Hooke discovered the cell
in the late 1600’s
• The smallest part of any living
organism
• Contains all parts necessary to
survive in changing environments
Microscopy
• Light Microscope (LM)
• Visible light passes through
the specimen then magnified
by glass lenses
• Uses prepared slides
• Wet mount
• Dry mount
Microscopy
• Transmission Electron Microscope (TEM)
• Used to study the internal structure of the cell
• Aims an electron beam through a very thin
section of a specimen which has been stained
with heavy metals to enhance the structure
• Uses magnets as lenses rather than glass
• Focuses on a monitor for viewing
• Disadvantage – specimen must be dead
Microscopy
• Scanning electron Microscope (SEM)
• Used to study detailed topographical
images of a specimen
• Uses electromagnetic lenses to scan
the surface of the sample –
• Usually coated with fine film of gold
• Disadvantage – specimen must be dead
Cytology – the study of the cell
Prokaryotic Cells vs. Eukaryotic Cells
• All cells have generalized features:
• Cytosol – semi-liquid fluid in which organelles are suspended – found in
both pro & eukaryotic cells
• Organelles – small organs of cell – most found only eukaryotic cells
• Plasma Membrane – double layer of phospholipids which surrounds cell –
found in both pro & eukaryotic cells
• Inclusions – Non-functioning parts of cell
NUCLEUS – CONTROL CENTER
• Located near the center of the cell
• Found in both plants & animals
• Found only in eukaryotic cells
• Contains the organism’s genetic material
• The cell (and organism’s) “blueprint”
• DNA – Deoxyribonucleic Acid
• Chromatin
• Genes
• Chromosomes
NUCLEOLUS – 1 OR MORE SMALL BODIES IN
CENTRAL AREA OF NUCLEUS
• Located near the center of nucleus
• Found in both plants & animals
• Found only in eukaryotic cells
• Site for ribosome production which will
migrate to cytoplasm
NUCLEAR ENVELOPE – (aka) NUCLEAR MEMBRANE
• Located surrounding the nucleus
• Found in both plants & animals
• Found only in eukaryotic cells
• Consists of a double-layer selectively
permeable membrane with relatively
large pores (nuclear pores)
• Serves to protect the nucleus and
determines what enters & leaves
nucleus
CHROMATIN– DNA (when it is not dividing)
• Located inside the nucleus
• Found in both plants & animals
• Found only in both prokaryotic and
eukaryotic cells – just not within a
membrane bound nucleus
• Consists of DNA (Genetic Material)
• Appears as loose bumpy granular
material scattered throughout the
nucleus
CHROMOSOME – DNA (when it is dividing)
• Located inside the nucleus
• Found in both plants & animals
• Found only in both prokaryotic &
eukaryotic cells
• Consists of DNA (Genetic Material)
• Appears as shortened thick
structures resembling X’s or curved
lines – condensed chromatin
material
CHROMASOME – CONDENSED CHROMATIN / DNA
PLASMA MEMBRANE – (aka) CELL MEMBRANE
• Surrounds the outside of the cell’s
cytoplasm
• Found in both plants & animals
• Found only in eukaryotic cells &
prokaryotic cells
• Consists of phospholipid bi-layer
• With a hydrophobic & hydrophilic side
• Functions to determine what enters
and leaves the cell – is selectively
permeable – selects which materials
can pass across the membrane
PLASMA MEMBRANE – (aka) CELL MEMBRANE
• Specializations –
• Microvilli – tiny fingerlike
projections that greatly
increase the cell’s surface
area
• Enhances cell’s absorption
ability
• Small intestines
PLASMA MEMBRANE – (aka) CELL MEMBRANE
• Specializations –
• Membrane Junctions –
varies structurally
• Tight Junctions
• Impermeable
• Bind cells together like a
zipper
• Desmosomes
• Anchoring junctions which
prevent cells from tearing
apart (i.e. – skin to skin or
skin to muscle)
PLASMA MEMBRANE – (aka) CELL MEMBRANE
• Specializations –
• Membrane Junctions –
varies structurally
• Gap Junctions
• Connects adjacent cells
with tubular connexons
which look like hollow
cylinders
• Found in the heart,
embryonic cells
• Functions mainly in cell to
cell communication
CYTOPLASM –
• Located outside the nucleus and
inside the plasma membrane
• Found in both plants & animals
• Found in prokaryotic & eukaryotic
cells
• Consists of 3 major elements
• Cytosol
• Organelles
• inclusions
Plasmodesmata
• Channels (in plants)
which function to
connect the
cytoplasms of
adjacent plants
• Similar to the
desmosomes and
gap junctions in
animals
CYTOPLASM –
• 3 major elements of cytoplasm
• Cytosol – semitransparent fluid
which suspends the organelles
• Organelles – “little organs” of cell
where all cell functioning occurs
• Inclusions – non-functioning units of
the cell such as lipid droplets,,
melanin (color pigment), etc.
MITOCHONDRIA – (aka) POWERHOUSE OF CELL
• In the cell’s cytoplasm
• Found in both plants & animals
• Found only in eukaryotic cells only
• Consists of a double layer membrane
surrounding “sausage-like” structures
which can move and wriggle about
• Functions to carry out the reactions
which use O2 to break down food into
cellular energy (ATP)
• Found most in metabolically busy
cells such as the liver & muscle cells
RIBOSOME – cell’s protein factories
• In the cell’s cytoplasm – tiny dark
bilobed bodies of protein
• Ribosomal RNA – (rRNA)
• Some float free but most are attached to
the Rough Endoplasmic Reticulum
• Found in both plants & animals
• Found in eukaryotic cells as well as
prokaryotic cells
• Not membrane bound in prokaryotic cells
• Functions synthesize proteins for cell
ENDOPLASMIC RETICULUM – (aka) ER
•
•
•
•
•
In the cell’s cytoplasm
Found in both plants & animals
Found only in eukaryotic cells ONLY
A “network” of tubules or “cisterns”
Accounts for about ½ of cell’s
membranes
• Location for ribosomes protein systhesis
• Functions to carry substances (primarily
proteins) from 1 part of cell to another
part of cell
• 2 forms –
• Rough ER & Smooth ER
ROUGH ENDOPLASMIC RETICULUM – (aka) ROUGH ER
Rough ER
• Studded with ribosomes
• Site of ribosomsal protein
synthesis
• Abundant in cells that export
protein products
• Pancreas – insulin & other
digestive fluids
SMOOTH ENDOPLASMIC RETICULUM – (aka) SMOOTH ER
Smooth ER
• Plays no actual role in protein
synthesis –
• Communicates with the Rough
ER & functions in lipid
metabolism
• Synthesis of lipids & steroid
hormones
• Metabolism of carbs
• Detoxifies drugs & pesticides;
• Storage of Ca ions
• Abundant in:
• Liver
• Testes – to produce testosterone
GOLGI APPARATUS – (aka) GOLGI BODY
• Located in the cytoplasm of cell
• Found in both plant & animal
cells
• Found in Eukaryotic cells only
• Functions to modify, package and
transport proteins
• 2 types –
• Transport Vesicles – modifies &
packages proteins
• Secretory Vesicles – transports
proteins from Golgi Apparatus to
plasma membrane
LYSOSOME – (aka) cell’s demolition sites
• Located in the cytoplasm of cell
• Found in animal cells
• Found in Eukaryotic cells only
• Functions to breakdown other
materials
• Contain powerful “digestive” enzymes
• “digest worn-out or non-usable” cells or
cell parts
• Exocytosis – transporting materials out
of cell
• Abundant in white blood cells
• “digest” bacteria & other foreign
substances
Cellular Digestive & Excretory Processes
• Endocytosis – cells taking materials INTO the cell
• Phagocytosis – taking in solid molecules
• Pinocytosis – taking in liquid molecules
• Exocytosis – cells passing materials OUT of the cell
PEROXISOME –
• Located in the cytoplasm of cell
• Found in both plant & animal
cells – Eukaryotic only
• Contains powerful oxidase
enzymes that use molecular O2
to detoxify harmful substances
• Functions to disarm free radicals
– highly reactive chemicals
• Can also convert H2O2 to H2O
• Look like small lysosomes
• Abundant in the liver & kidneys
CYTOSKELETON –
• Located in the cytoplasm of cell
• Found in both plant & animal cells
• Functions to provide form &
structure to cells
• Found in Eukaryotic cells only
• Made of protein components
CYTOSKELETON –
• Consists of 3 types of protein
filaments
• Intermediate filaments – help form
desmosomes to provide internal guy
wires to resist pulling forces
• Microfilaments – such as actin &
myosin – involved in cell motility
and changes in cell shape (muscle
cells)
• Microtubules – determine the
overall shape of the cell and the
distribution of organelles
• Important during cell division
CENTRIOLES –
• Located in the cytoplasm of cell –
usually near the nucleus
• Found in both plant & animal cells
• Found in Eukaryotic cells only
• Rod-shaped bodies that lie at right
angles to each other Made up of
fine microtubules and form the
mitotic spindle during cell division
• Some have cilia and/or flagella
Cilia & Flagella –
• Cilia - Microtubules used to move materials around outside of cell
• Usually many of these small projections surrounding the cell or at least the exterior
surface of a cell
• Flagella – responsible for motility of the cell as a whole
• Usually only one or a few and are long whip-like structures
Vacuole
• Predominantly found in
eukaryotic / plants
• Functions to
• Storage of water & other nutrients
• Breakdown wastes to be disposed
of
• Hydrolysis of macromolecules
• Enlargement of vacuole is major
mechanism in plant growth
• Can act as a pump to rid the plant
of excess water
• Contractile Vacuoles
Chloroplasts
• Predominantly found in eukaryotic
/ plants
• Sit of photosynthesis – in leaf 7 other
green organ of plants
• Contain the green pigment –
chlorophyll
• Membranous system
• Thylakoid
• Granum
• Stroma
• a type of plastid
• Other examples are
• Amyloplast
• Chromoplast