Download Cell organelle notes pt 1

Cell Structure
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Don’t Freak Out
• Test on cell organelle on Friday!
• This test should be a buffer test and help raise
your overall test score.
• All information will come from this week!
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Cells Provide Compartments for
Biochemical Reactions
Cells contain
•
water, small and large molecules
• Each cell contains at least 10,000 different
molecules (many copies of most)
• Cells use these molecules to transform matter
and energy, respond to their environments
and to reproduce
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First Unifying Theme of Biology
Cell Theory
1. The cell is the basic unit of life.
2. All living things are composed of
cells.
3. All cells come from preexisting cells.
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Two Conceptual Implications of
Cell Theory
• Studying cell biology is in some sense the
same as studying life– The principles that
cause bacterial functioning are similar to
those governing the approx. 60 trillion
cells in an adult human.
• Life is continuous– All those human cells
came from a single fertilized cells which
were cells from parents whose cells came
from parents and so on– all the way back
to the evolution of the first living cells.
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Cell size– limited by surface area to
volume ratio
• As a living cell grows larger, its metabolic
activity and need for resources increases
faster than its surface area.
• Cells must maintain a large SA/V ratio in order
to function.
• This explains why multicellular organisms
must be composed of many small cells rather
than a few large ones.
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Cell Membrane forms the outer
surface of every cell
• Remember, a key to the origin of life was the
enclosure of biochemical functions within a
cell membrane.
• Phospholipid bilayer with proteins.
– Selectively permeable
– Communication with other cells and gets signals
from environment
– Proteins can bind and adhere to surrounding
environment
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Cells are classified as prokaryotic
or eukaryotic
• Prokaryotes
– Does not have membrane-enclosed internal
compartments (organelles); in particular, no
nucleus
• Eukaryotes- contain membrane-bound
compartments (organelles!) where specific
metabolic functions occur
– Organelles allow a “division of labor” that was
important for the evolution of more complex
organisms
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Prokaryotic Cells Do Not Have a
Nucleus (Review)
• 1-10 micrometers in length (smaller than
eukaryotes)
• Have cell membrane
• Have nucleoid region where DNA is stored
• Have cytoplasm- consists of a liquid
component, other particles, and ribosomes
• Has ribosomes- RNA and proteins– sites of
protein synthesis.
• “Sticky” cell wall (different than plant cell wall)
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Prokaryotes
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Prokaryote
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Compartmentalization is key to
eukaryotic cell function
• Each type of organelle has a specific role in
the cell.
• Plant and animal cells have organelles in
common as well as differences in organelles.
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Eukaryotic Animal Cell
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Ribosomes are factories for protein
synthesis (making)
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Translate mRNA into a polypeptide chain
Consists of a large subunit and a small subunit
Consists of rRNA (ribosomal RNA) and proteins
Not membrane-enclosed
In prokaryotes, float freely in cytoplasm
In eukaryotes, float in cytoplasm and on rough
ER
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Nucleus contains cell’s DNA
• DNA- hereditary information
(chromosomes/chromatin)
• Nucleus is usually the largest organelle.
• Functions:
– Location of DNA and DNA replication
– Where DNA is transcribed to RNA
– Contains the nucleolus, a region where ribosomes
assembly begins
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Nucleus
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Nucleus
• Two lipid bilayers (two membranes) that form
the nuclear envelope.
• Separates DNA transcription from translation
• Has nuclear pores which regulate movement
of molecules into and out of the nucleus.
• Nucleus is continuous with the endoplasmic
reticulum.
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Nuclear Envelope and E.R. Connection.
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Endomembrane System
• A group of interrelated organelles
• And interconnected system of membraneenclosed compartments and contains the
nuclear envelope, endoplasmic reticulum,
Golgi apparatus, and lysosomes.
• Vesicle shuttle substances between the
various components of the endomembrane
system and the cell membrane.
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The Endomembrane System
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Endoplasmic Reticulum
• Network of interconnected membranes
branching through the cytoplasm
• Tubes and flattened sacs
• Collectively called the ER
• Interior is distinct from the outer cytoplasm
• Two types!
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1. Rough ER
• Called rough because of attached ribosomes
to outer surface
• Proteins are chemically modified in the rough
ER and “tagged” for delivery
• The rough ER participates in transporting
these proteins to other locations in the cell;
vesicles pinch off to do this
• Most membrane-bound proteins made in
rough ER
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2. Smooth ER
• Lack ribosomes
• Four important roles
– Chemical modification of small molecules
that may be toxic to the cell in order to
remove easier
– Site for glycogen degradation in animal cells
– Site where lipids and steroids are
synthesized
– Stores calcium ions; when release trigger a
number of cell reactions, such as muscle
contractions
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Smooth ER
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Golgi apparatus
• Two Components: 1) Flattened sacs called
cisternae and 2) small membrane enclosed
vesicles
• Protein containing vesicles from rough ER
release into Golgi apparatus cisternae, where
they are further modified.
• Vesicles coming off the Golgi apparatus go to
lysosomes or the cell membrane.
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Golgi Functions
1. Concentrates, packages, and sorts proteins
before they are sent to their cellular or
extracellular destinations
2. It adds some carbohydrates to proteins
3. It is where some polysaccharides for the
plant cell wall are synthesized (made).
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Golgi Apparatus
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3-D Illustration of the Golgi Apparatus
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Electron Micrograph of the Golgi
Apparatus
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Golgi Apparatus Directing Secretions
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Lysosomes
• Originate from the Golgi apparatus
• Contain digestive enzymes and they are the
site where macromolecules are hydrolyzed
into their monomers
• R1+R2 (linked monomers) + H2O  R1-OH + R2H
• **Hydrolysis
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Lysosomes
• Some things hydrolyzed by lysosomes enter by
phago and pinocytosis
• Autophagy is the programmed destruction of
cell components.
• An entire class of diseases called lysosomal
storage diseases can happen if autophagy
does not work properly. Ex: Tay-sachs– a lipid
not broken down and accumulates in brain
cells, damaging them.
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Lysosomes
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Plant cells do not have lysosomes
• But their central vacuole seems to play a
similar role and has many digestive enzymes.
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Mitochondria
The mitochondrion is used to phosphorylate ADP to ATP
(energy). Two membranes- outer and inner. Inner is folded in.
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Mitochondria and Endosymbiosis
Mitochondria evolved from ancient
prokaryotic cells through
endosymbiosis. The evidence includes:
1. Has its own DNA that is circular like
prokaryotes
2. Has prokaryotic like ribosomes
3. Replicates like a prokaryote
4. Does protein synthesis like a
prokaryote
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3-D Illustration of the Mitochondria
In cells, a higher the energy demand, corresponds with an
increase in the number of mitochondria in the cell.
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Eukaryotic Plant Cell- What is
different?
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Plastids-- Chloroplasts
• In plants and algae and can differentiate into
different types of organelles
• Chloroplasts- contains the green pigment
chlorophyll and is the site of photosynthesis.
• Photosynthesis– converts light into food
• Two membranes.
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Chloroplasts
• Thylakoids- stacks of hollow disks. Light energy
converted to chemical energy
• Stroma- aqueous fluid surrounding the
thylakoids. Carbohydrates synthesized here.
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Vesicles and Vacuoles
Vacuoles and vesicles
are membrane bound
compartments used
for storage. Vacuoles
are larger than
vesicles. Plants use a
large central water
vacuole to maintain
their turgor and
structure.
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Contractile Vacuoles
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The Cytoskeleton Provides Strength
and Movement
• Interior of cell– network of protein
filaments
• Filament- each type is a polymer
made up of protein monomers
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Cytoskeleton-- Functions
1. Supports cell and maintains its shape
2. Holds cell organelles and other
particles in position within the cell
3. Moves organelles an other particles
around within the cell
4. Involved in movements of the
cytoplasm called cytoplasmic streaming
5. Interacts with extracellular structures,
helping anchor the cell in place.
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Three components of eukaryotic
cytoskeleton
1.Microfilaments
2.Intermediate filaments
3.Microtubules
Different functions…
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Microfilaments
• Usually in bundles
• Help the entire cell or parts move.
• Determine and stabilize the shape.
• Made up of actin!
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Intermediate Filaments
• Anchor cell structures in place.
• They resist tension!
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Microtubules
• Long, hollow, unbranched cylinders.
• Form rigid internal skeleton for some cells or
cell regions.
• Act as a framework along which motor
proteins can move structures within a cell.
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