Cell Membrane
• Also called Plasma Membrane
• Controls what crosses membrane
• Selectively PERMIABLE
• Fluid Mosaic Model
Cellular Organelles
Cell Membrane and
Organelles
–Contains: proteins, phospholipids,
Cholesterol, channels, pumps ...
Cellular Organelles
• Nucleus
• Mitochondria
–Nucleolus
• Plastids
• Ribosome
• Vacuoles
• Endoplasmic
• Lysosomes
Recticulum
• Chloroplasts
–Smooth & rough
• Cilia, Flagella
• Golgi
• Other
Structure of a Generalized Cell
Cytoplasm
Figure 3.2
• Cytoplasm – material between plasma
membrane and the nucleus
• Cytosol – largely water with dissolved
protein, salts, sugars, and other solutes
• Cytoplasmic organelles – metabolic
machinery of the cell
• Inclusions – chemical substances such as
glycosomes, glycogen granules, and
pigment
1
Cytoplasmic Organelles
• Specialized cellular compartments
• Membranous
– Mitochondria
Mitochondria, peroxisomes,
peroxisomes lysosomes
lysosomes,
endoplasmic reticulum, and Golgi apparatus
• Nonmembranous
– Cytoskeleton, centrioles, and ribosomes
Nucleus
• Nuclear membrane
–controls movement
–porous
• Contains DNA & Nucleolus
• Control Center
Nucleus
• Contains nuclear envelope, nucleoli,
chromatin, and distinct compartments rich
in specific
p
pprotein sets
• Gene-containing control center of the cell
• Contains the genetic library with blueprints
for nearly all cellular proteins
• Dictates the kinds and amounts of proteins
to be synthesized
2
Nucleus
Nuclear Envelope
• Selectively permeable double membrane barrier containing
pores
y
nucleoplasm,
p
which contains essential
• Encloses jjellylike
solutes
• Outer membrane is continuous with the rough ER and is
studded with ribosomes
• Inner membrane is lined with the nuclear lamina, which
maintains the shape of the nucleus
Figure 3.28a
Nucleoli
• Dark-staining spherical bodies within the nucleus
• Site of ribosome production
• Pore complex regulates transport of large molecules into
and out of the nucleus
Chromatin
• Threadlike strands of
DNA and histones
• Arranged in
fundamental units
called nucleosomes
• Form condensed,
barlike bodies of
chromosomes when
the nucleus starts to
divide
Figure 3.29
Endoplasmic Recticulum
• Connects Nucleus to Golgi
p of Chemicals
• Internal transport
• Rough - has ribosomes
–Makes Protiens
• Smooth - no ribosomes
–makes lipids, Neutralizes toxins
3
Ribosome
• Made of RNA
• Make Proteins
• Found in RER
• Found in Cytoplasm
Endoplasmic Reticulum (ER)
Ribosomes
•
•
•
•
Granules containing protein and rRNA
Site of protein synthesis
Free ribosomes synthesize soluble proteins
Membrane-bound ribosomes synthesize
proteins to be incorporated into membranes
Endoplasmic Reticulum (ER)
• Interconnected tubes and parallel
membranes enclosing cisternae
• Continuous with the nuclear membrane
• Two varieties – rough ER and smooth ER
Figure 3.18a and c
Smooth ER
Rough (ER)
• Tubules arranged in a looping network
• Catalyzes the following reactions in various
organs of the body
– In the liver – lipid
p and cholesterol metabolism,,
breakdown of glycogen and, along with the kidneys,
detoxification of drugs
– In the testes – synthesis of steroid-based hormones
– In the intestinal cells – absorption, synthesis, and
transport of fats
– In skeletal and cardiac muscle – storage and release
of calcium
• External surface studded with ribosomes
• Manufactures all secreted proteins
• Responsible for the synthesis of integral
membrane proteins and phospholipids for
cell membranes
4
Signal Mechanism of Protein
Synthesis
Signal Mechanism of Protein
Synthesis
• mRNA – ribosome complex is directed to
rough ER by a signal-recognition particle
(SRP)
• SRP is released and polypeptide grows into
cisternae
• The protein is released into the cisternae
and sugar groups are added
• The protein folds into a three-dimensional
conformation
• The p
protein is enclosed in a transport
p vesicle and
moves toward the Golgi apparatus
Signal Mechanism of Protein
Synthesis
Figure 3.19
Golgi Bodies
• Shipping Warehouse
p compounds
p
• wraps
in membranes
• Complex
or apparatus
Golgi Apparatus
• Stacked and flattened membranous sacs
• Functions in modification, concentration, and
packaging of proteins
• Transport vessels from the ER fuse with the cis
face of the Golgi apparatus
• Proteins then pass through the Golgi apparatus to
the trans face
• Secretory vesicles leave the trans face of the Golgi
stack and move to designated parts of the cell
5
Role of the Golgi Apparatus
Golgi Apparatus
Figure 3.20a
Lysosomes
Endomembrane System
• Spherical membranous bags containing digestive enzymes
• Digest ingested bacteria, viruses, and toxins
• System of organelles that function to:
– Produce, store, and export biological molecules
– Degrade potentially harmful substances
• Degrade nonfunctional organelles
• Breakdown glycogen and release thyroid hormone
• System includes:
• Breakdown nonuseful tissue
• Breakdown bone to release
Figure 3.21
Ca2+
• Secretory lysosomes are found in white blood cells, immune
cells, and melanocytes
– Nuclear envelope, smooth and rough ER,
lysosomes, vacuoles, transport vesicles, Golgi
apparatus, and the plasma membrane
Endomembrane System
Peroxisomes
• Membranous sacs containing oxidases and
catalases
• Detoxify harmful or toxic substances
• Neutralize dangerous free radicals
– Free radicals – highly reactive chemicals with
unpaired electrons (i.e., O2–)
Figure 3.23
6
Mitochondria
• Has own DNA
–maternal inheritance
–evolutionary
evolutionary thoughts
• Powers the cell
• Respiration
–2 membranes - Inner folded Cristae (krebs Cycle here)
Mitochondria
Mitochondria
• Double membrane structure with shelflike
cristae
• Provide most of the cell’s ATP via aerobic
cellular respiration
• Contain their own DNA and RNA
Figure 3.17
Vacuoles - Storage tanks
• Play large role in support for plants
• Plastids - specialized vacuole in plant cells
– Chromoplasts
Ch
l
- store pigments
i
- color
l storage
– Leukoplasts - food storage - granules of starch
Lysosome
• lyse break down- some is body - digestive
body
• Only in animal cells
• Break down dangerous & nonfunctional
things
7
Chloroplast
•
•
•
•
Only in Plants
Energy converter
Changes solar energy into chemical energy
All energy for life comes from the sun
Cytoskeleton
Cell structure & support
•
•
•
•
Microtubules - Hollow protein tubes
Shape of cytoplasm, movement of organelles
Form centrioles - only in animal cells
Support for locomotion
– Cilia - basil bodies - 9 triplets
• tiny hairs that beat or wave
– Flagella - 11 microtubules - 9 around 2
• Long whip like tail
Cytoskeleton cont
• Micro filaments - long thin fibers of actin
• Actin is a protein found in muscles
• Specialized for contraction
• Movement of and in cytoplasm
– Oranelle movement
– cytoplasmic streaming
8
Cytoskeleton
Cytoskeleton
• The “skeleton” of the cell
• Dynamic, elaborate series of rods running
through the cytosol
• Consists of microtubules, microfilaments,
and intermediate filaments
Figure 3.24
Microtubules
• Dynamic, hollow tubes made of the
spherical protein tubulin
• Determine the overall shape of the cell and
distribution of organelles
Intermediate Filaments
• Tough, insoluble protein fibers with high
tensile strength
• Resist pulling forces on the cell and help
form desmosomes
Microfilaments
• Dynamic strands of the protein actin
• Attached to the cytoplasmic side of the
plasma membrane
• Braces and strengthens the cell surface
• Attach to CAMs and function in
endocytosis and exocytosis
Motor Molecules
• Protein complexes that function in motility
• Powered by ATP
• Attach to receptors on organelles
9
Motor Molecules
Motor Molecules
Figure 3.25a
Figure 3.25b
Centrioles
Centrioles
• Small barrel-shaped organelles located in
the centrosome near the nucleus
• Pinwheel array of nine triplets of
microtubules
• Organize mitotic spindle during mitosis
• Form the bases of cilia and flagella
Figure 3.26a, b
Cilia
Cilia
• Whiplike,
p
, motile cellular extensions on
exposed surfaces of certain cells
• Move substances in one direction across
cell surfaces
Figure 3.27a
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Cilia
Cilia
Figure 3.27b
Figure 3.27c
Structure of a Generalized Cell
Figure 3.2
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