Transcript Ch 3 Parts of Cell-Junctions-Types pages 62-75

Pages 62-75
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It is important to know the organelles within
the cell and to understand the general
functions of each
◦ Organelles > cell
◦ Organs > system
◦ Organ systems > human body
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Nucleus = control center; houses DNA
Plasma Membrane = selective; boundary
Ribosomes = site of protein synthesis
Mitochondria = site of cellular respiration
Endoplasmic Reticulum = transportation network
◦ Rough = finalizing protein synthesis - folding
◦ Smooth = fat metabolism and detoxing
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Golgi Bodies =protein packaging; become vesicles
Vesicles = move products via endocytosis/exocytosis
Lysosomes = garbage crew
Peroxisomes = detoxification/neutralizers
Cytoskeleton = structural organelle
Centrioles =direct cell division via mitotic spindle
Smooth
endoplasmic
reticulum
Chromatin
Nucleolus
Nuclear envelope
Nucleus
Plasma
membrane
Lysosome
Mitochondrion
Rough
endoplasmic
reticulum
Centrioles
Ribosomes
Golgi
apparatus
Peroxisome
Secretion being
released from cell
by exocytosis
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Plasma Membrane Junctions
◦ Cells are bound together in three ways:
1. Glycoproteins act as an adhesive or cellular glue
2. Wavy contours of the membranes of adjacent cells
fit together in a tongue-and-groove fashion
3. Special membrane junctions are formed, which
vary structurally depending on their roles
1. 3 different junctions
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Extracellular fluid
(watery environment)
Glycoprotein Glycolipid
Cholesterol
Sugar
group
Polar heads
of phospholipid
molecules
Bimolecular
lipid layer
containing
proteins
Nonpolar tails
of phospholipid
molecules
Channel
Proteins Filaments of
cytoskeleton
Cytoplasm
(watery environment)
Tight
(impermeable)
junction
Microvilli
Desmosome
(anchoring
junction)
Plasma
membranes of
adjacent cells
Connexon
Gap
Underlying Extracellular
basement space between (communicating)
junction
membrane cells
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Tight junctions
◦ Impermeable junctions made up of the plasma
membrane
◦ Bind cells together into leakproof sheets
◦ Prevent substances from passing through
extracellular space between cells
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Desmosomes
◦ Anchoring junctions that prevent cells from being
pulled as a result of mechanical stress
◦ Created by “buttonlike” thickenings of adjacent
plasma membranes
 kind of like the rivets in the pockets of your jeansthey keep the material together
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Gap junctions
◦ allow direct diffusion of ions and small molecules
between adjacent cells
◦ Hollow cylinders of proteins (connexons) function
like tunnels to send messages
 Molecules can travel directly from one cell to the next
through these channels
© 2015 Pearson Education, Inc.
Tight
(impermeable)
junction
Microvilli
Desmosome
(anchoring
junction)
Plasma
membranes of
adjacent cells
Connexon
Gap
Underlying Extracellular
basement space between (communicating)
junction
membrane cells
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Active Transport of bulk materials
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Endocytosis:
◦ Plasma membrane engulfs product from
extracellular space to bring into cell
◦ Becomes travelling vesicle inside cell
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Exocytosis:
◦ Vesicle from inside the cell fuses with plasma
membrane to dump contents outside of cell
Extracellular Plasma
membrane
fluid
SNARE
(t-SNARE)
Secretory
vesicle
1 The membranebound vesicle
Vesicle
migrates to the
SNARE
(v-SNARE) plasma membrane.
Molecule
to be
secreted
Cytoplasm
Fusion pore formed
Fused
SNAREs
2 There, v-SNAREs
bind with t-SNAREs,
the vesicle and
plasma membrane
fuse, and a pore
opens up.
3 Vesicle contents
are released to the
cell exterior.
(a) The process of exocytosis
(b) Electron micrograph of a
secretory vesicle in
exocytosis (190,000×)
Extracellular
fluid
Cytosol
Vesicle
1 Vesicle fusing
with lysosome
for digestion
Plasma
membrane
Lysosome
Release of
contents to
cytosol
2 Transport to plasma
membrane and exocytosis
of vesicle contents
Detached vesicle
Ingested
substance
Pit
(a)
3 Membranes and receptors
(if present) recycled to plasma
membrane
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Cilia: whiplike extensions
◦ Propels substances along passageways
 Found in respiratory passageways, uterine tubes,
kidneys, inner ear
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Flagella: longer whiplike extensions
◦ Propels the cell
 The sperm is the only flagellated cell in the human
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Microvilli: extensions of cell membrane
◦ Increases cell surface area (often for absorption)
 Found along entire small intestine; large numbers
along the proximal convoluted tubule in the nephron
Blood vessels
serving the small
intestine
Muscle
layers
Villi
Microvilli
(brush border)
Lumen
Circular folds
(plicae circulares)
Absorptive
cells
Lacteal
(a) Small intestine
(c) Absorptive
cells
Villus
Blood
capillaries
Lymphoid
tissue
Intestinal
crypt
Muscularis
mucosae
Venule
Lymphatic vessel
Submucosa
(b) Villi
Flagellum
Nucleus
Sperm
(g) Cell of reproduction
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Cells can vary in structure and function
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Variations include:
◦ Modified shape
◦ More of a particular organelle
◦ Modified organelles
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Cells are classified based on their structure
and function
This is known as Histology
◦ the study of the structure of cells and their
formation into tissues and organs
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An Histologist can identify abnormalities in
tissues obtained from cultures/biopsies
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Epithelial
◦ Secrete and aborb
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Connective
◦ Hold structures together, store nutrients
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Muscular
◦ Movement
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Nervous
◦ communication
EPITHELIAL
Epithelial
cells
Nucleus
Intermediate
filaments
MUSCULAR
Skeletal
muscle cell
Contractile
filaments
Nuclei
Smooth
muscle cells
CONNECTIVE
Fibroblasts
Rough ER and Golgi
apparatus
No organelles
Nucleus
Erythrocytes
NERVOUS
Processes
Rough ER
Nerve cell
Nucleus