Cell Unit I: Organelles and Cell
Membranes - Chapters 7 and 8
Chapter 7: A Tour of the Cell
• Themes: THE CELL, Structure and Function,
Evolution, Regulation, Heritable Information,
• Objectives:
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Microscopes
Organelles
Prokaryotic vs. Eukaryotic
Membranes
Cytoskeleton
Cell Surface and Junctions
Root Words
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CentroChloroCiliCyto –
-ell
Endo –
Eu –
ExtraFlagellGlyco –
-tubul
-oid
- pod
Thylaco -
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Lamin –
Lyso –
Micro –
Nucle –
Phago –
Plasm –
Pro-karyo
-soma
-kytos
-desma
Pseudo –
Tono –
-plast
Note: MOST CELLS ARE
BETWEEN 1 & 100
MICROMETERS.
Human cells - 60 trillion in
the human body; 200
different kinds of cells.
Size: red blood cells 1/25,000 of inch in
diameter (250 side by
side would fit in period at
end of this sentence).
SIZES: Larger muscle cells - few inches long
Nerve cells - run from base of spine to
the tip of the toe (many feet long!!)
CELLS VARY IN: size, color, shape & function.
Since all living things have cells, cells hold the
secrets to many of life’s most intriguing
questions:
(A) Aging (telomeres)
(B) Cures to most if not all diseases. Example:
4,200 human diseases are caused by a defect
in a single gene (which lead to mis-shapened
proteins.)
(C) Stem cell research.
(D) Evolutionary questions & problems
(E) Behavior of cells.
(F) Cancer
CYTOLOGY: The study of cells.
MICROSCOPY: The art of examining
objects under the microscope.
Electron Microscopes (EM). 2 types:
(A) Transmission electron microscope
(TEM)
(B) Scanning electron microscope (SEM)
EUKARYOTIC & PROKARYOTIC CELLS:
Prokaryotic: no
nucleus (have a
nucleoid) but do have
ribosomes & plasma
membrane. They lack
membrane enclosed
organelles. Only
member of this
group are
BACTERIA.
EUKAROYTIC CELLS: Have extensive and elaborately
arranged internal membranes surrounding their organelles to
allow for COMPARTMENTALIZATION.
This allows different metabolic processes to go
on simultaneously inside the cell without one
process interfering with another.
EX: The lysosome digests macromolecules that are
worn out or no longer needed. The enzymes that do
the digesting need a pH of around 5.
What problems would be caused if this organelle did
not have a membrane????
NUCLEUS & PARTS: Nucleolus - Components
of ribosome (precursors) are synthesized.
Remember - Nuclear envelope is a double
membrane as is all membranes. (See Fig. 7.6).
CHROMATIN: Contains nuclear DNA.
When a cell divides this becomes the
chromosomes.
RIBOSOMES - MAKE PROTEINS, 2 TYPES:
• FREE RIBOSOMES - SUSPENDED IN THE
CYTOSOL.
• BOUND RIBOSOMES - ATTACHED TO THE
OUTSIDE OF THE ER
ENDOMEMBRANE SYSTEM: RELATED THROUGH
DIRECT PHYSICAL CONTINUITY OR BY THE
TRANSFER OF MEMBRANE SEGMENTS AS TINY
VESICLES (MEMBRANE ENCLOSED SACS).
Include the nuclear envelope, ER, Golgi apparatus,
lysosomes, various kinds of vacuoles, and the plasma
membrane.
ENDOPLASMIC RETICULUM: Made of membranous
tubules and sacs called cisternae.
SMOOTH ER: No ribosomes.
ROUGH ER: Ribosomes on the outside edge.
Index Cards
• On each card, draw a picture and write a
description:
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Peroxisome
Centrosome
Microfilaments and Microtubules
Plasmodesmata
Tonoplast
Plastid
NOTE: The ER and the
nuclear membrane are
continuous.
FUNCTION - SMOOTH ER:
synthesis of lipids, metabolism of
carbohydrates
FUNCTION - ROUGH ER
Ribosomes making protein release
protein into ER. ER attaches
carbohydrate to protein
(glycoprotein). New proteins
wrapped in membranes of vesicles
for transport (TRANSPORT
VESICLES).
GOLGI APPARATUS - Center for manufacturing,
warehousing, sorting and shipping. Products of ER are
modified, stored & sent to other places. They also
manufacture some macromolecules themselves.
LYSOSOME- Contains enzymes used to digest
macromolecules. Once molecules are broken down, they
can be recycled. Tadpole to Frog, webbed to normal hands
and toes in humans.
Tay-Sachs disease- a lipid digesting enzyme is missing or
inactive and lipid accumulates and causes brain and nerve
disorder & leads to death.
THE CELL’S “GARBAGE DISPOSAL.”
VACUOLES: 3 typesFood vacuole - store food
Contractile vacuole - pumps excess water out of a cell.
CENTRAL VACUOLE:
Makes up 80% of most
mature plant cells. The
membrane is called the
tonoplast. This vacuole
stores materials,
involved in waste
disposal, protection &
growth.
MITOCHONDRIA - Site of cellular respiration.
Sometimes called the “Powerhouse” of the cell.
Has its own DNA & ribosomes. Note the parts:
especially Cristae.
More
mitochondria
are located
in cells like
muscle since
they need
more energy
per given
time.
CHLOROPLAST - Sites of photosynthesis. They
contain grana, which are stacks of thylakoids and open
spaces called stroma. They also have their own DNA &
ribosomes.Also enclosed in an envelope of 2
membranes. Take in CO2 & release O2.
PEROXISOMES: Contain enzymes that transfer
hydrogen from various substrates to oxygen
making H2O2.
Later hydrogen
peroxide is
converted to
water & oxygen.
Also contains
enzymes that
convert fats to
sugar. Also have
many other
functions.
A NETWORK OF
FIBERS EXTENDING
THROUGH THE
CYTOPLASM. It plays a
major role in organizing
the structures and
activities of the cell.
MICROTUBULES: The
thickest.
MICROFILAMENTS:
the thinnest. (ACTIN)
INTERMEDIATE
FILAMENTS: middle
range.
THE CYTOSKELETON
MICROFILAMENTS: Participate in the formation of
cell cleavage furrow during cell division.
**9 + 2 Arrangement of microtubules makes up
a cilia & flagella - used in movement of some
cells. **
CYTOSKELETON
CAN:
PROVIDE
MECHANICAL
SUPPORT; MAINTAIN
CHARACTERISTIC
SHAPE OF CELLS.
They also hold
organelles in place &
assist in cell motility.
CELL SURFACES & JUNCTIONS:
----------------------------------------------------------CELL WALLS: (Plants, Prokaryotes, Fungi & some
Protists)
Young Plant: Primary cell wall.
Middle lamella; between primary walls of adjacent
cells. This “glues” the cells together.
Secondary cell wall - between the plasma membrane
& the primary wall. Innermost portion of a mature
plant cell wall.
PLASMODESMA: Connecting openings between plant
cells. This makes plant cells one living continuum.
Water & small solutes pass freely from cell to cell.
PLASMODESMATA - PLURAL
INTERCELLULAR JUNCTIONS IN ANIMALS:
DESMOSOMES -Anchoring junctions.
GAP JUNCTIONS- Communicating junctions. Allow
things to move from cell to cell like plasmodesmata
in plants..
CHAPTER 8
MEMBRANE STRUCTURE AND
FUNCTION
Membranes are SELECTIVELY PERMEABLE.
Membranes are about 8 nm thick (8,000 of them would
be the thickness of the page of your book).
A membrane is a phospholipid bilayer that has
cholesterol & integral protein molecules that are
receptors, channels, & pumps with outside surfaces made
of glycolipids & glycoproteins.
Peripheral proteins line some of the inside of the cell.
Each type of cell in the body has its own receptors,
channels, pumps. The number and type varying with the
cell’s specialized needs.
TENS OF THOUSANDS OF RECEPTORS,
SOMETIMES HUNDREDS OF THOUSANDS, ARE
EMBEDDED IN THE OUTER MEMBRANE OF MOST
CELLS.
***Know these parts and functions of the
Fluid Mosaic Model of a cell membrane.***
This model is only a theory. You will see an
image similar to this on your test.
Important concepts to know about cell
membrane structure:
•The membrane is called fluid because it moves
•The phospholipids move laterally along the plane of the
membrane. (Membranes are asymmetric & fluid)
•Glycoproteins & Glycolipids in animal cells are used to
recognize similar and different cells. (Glyco- means a
sugar has been added to the molecule).
•Cholesterol in animal cells is used to maintain membrane
fluidity & stabilize the membrane. Especially helps cells
stay fluid when temperatures drop.
•Integral proteins (embedded in the membrane) help
cells recognize each other. These are usually
glycoproteins. (Usually transmembrane proteins).
Oligosaccharides (short polysaccharides) attached to
lipids are called glycolipids; attached to proteins, they are
called glycoproteins. (These aid in cell to cell recognition).
MEMBRANE POTENTIAL: All cells have voltage across
their membrane. (The inside is (-) compared to the
outside).
IONS - Pass through a membrane down an
ELECTROCHEMICAL GRADIENT. (Imp. Concept)
Outside of membrane - proteins are attached to
fibers of the EXTRACELLULAR MATRIX.(ECM).
Small polar molecules that are uncharged like water &
ethanol can pass easily through the lipid membrane as
well as small molecules (O2 )
Fig. 8.9 Some
Functions of membrane
proteins:
A single protein can
sometimes perform
combinations of these
functions.
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Other concepts about
membrane (Due to Lipid
bilayer):
•Hydrophobic molecules
(CO2 & O2) can dissolve
membrane & cross it.
Relatively impermeable
to ions (Like H+ & Na+)
Cell Signaling (Chapter 11)
Signal Transduction
Pathway
• Hormones -
3 Stages of Cell Signaling:
• Reception
• Transduction
• Response
Cell Signaling
• Ligand Gated Ion Channels –
– Ligands are small molecules that bind to a
specific larger one
– Channels are part of plasma membrane that
allows the flow or blockage of ions (Ca2+)
– EX: Synapse between nerve cells
History of Cell Signaling
• How do yeasts and sex show the history of
cell signaling? (5 lines) Page 197
Intracellular Receptors
• Not within the membrane, in cytoplasm
• Transcription factors – special proteins that
control which genes are transcribed into
mRNA (we get into this more in Cell Unit
3)
– Ex: testosterone and thyroid hormones
• Protein Kinase – enzymes that transfer
phosphate groups from ATP to a protein to
activate it (phosporylation)
• Review Sutherland’s work with Cyclic
AMP
DIFFUSION: (Fig. 8.10)
Down a concentration
Gradient. (From high conc. to
low conc. until equal)
PASSIVE TRANSPORT:
Diffusion across a membrane
with conc. gradient & w/o the
use of energy (ATP).
OSMOSIS:
Movement of water
across a membrane
(passive transport)
AP LAB: #1
Osmosis and Diffusion
OSMOSIS & THE PASSIVE TRANSPORT OF WATER:
HYPERTONIC (Solution). One that has higher
concentration of solute than solvent compared to another
solution.
HYPOTONIC (Solution). One that has a lower
concentration of solute than solvent compared to
another solution.
ISOTONIC (Solution). 2 Solutions are equal in
solute concentration.
EXAMPLE: Tap water is hypertonic to distilled water
but hypotonic to seawater. These terms are relative
terms & only meaningful in a comparative sense.
Remember Lab. 1 !!
This Drawing & many problems associated with it are in
both Test & Lab. # 1. (Fig. 8.11)
Water always moves from a HYPO to a HYPERTONIC
solution until a isotonic situation is met.
REMEMBER:
Hyper (high) &
hypo (low) refers
to SOLUTE not
SOLVENT
(water).
Fig. 8.12 THE WATER BALANCE OF LIVING CELLS:
NOTE: Terms & concepts of water
movement.
FACILATED DIFFUSION: (Use Transport Proteins) (Fig. 8.14)
PASSIVE TRANSPORT of selected solutes.
(Remember) - Passive transport always goes with
concentration gradient.
If a substance is
diffusing much
faster than the
physical
environment
indicates it should
than it is
Facilated
Diffusion.
Glucose
sometimes does
this.
ACTIVE TRANSPORT: “Pumping” a molecule against it’s
concentration gradient (LOW TO HIGH CONC).
• Involves the expenditure of energy by the cell (ATP).
• Involves the action of specific proteins embedded in the
membrane.
COMPARSIONS OF TRANSPORTS
EXAMPLE OF ACTIVE TRANSPORT:
Sodium-Potassium Pump.
ACTIVE TRANSPORT – SODIUM POTASSIUM PUMP
COTRANSPORT PROTEIN: This allows 2 different
substances to pass through a membrane in the same
direction.
NOTE:
Here H+
(with the
help of ATP)
moves out
of the cell
but escorts
sucrose
back into
the cell.
Test Hints: Use your CD & look at
all the videos.
Make sure your study Fig. 8.18 and know
the difference between:
Exocytosis & Endocytosis
Types of Endocytosis: Phagocytosis &
Pinocytosis.