Chapter 3 - Cellular Structure and Function

Cellular Structure and Function

1. Chapter 3
Cellular structure and function
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2. 3-2
Cell Shapes and Sizes
Squamous
Polygonal
Cuboidal Columnar
Spheroid
Discoid Fusiform (spindle-shaped)
Stellate
Fibrous
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Figure 3.1

3. 3-3
Cell Shapes and Sizes
•About 200 types of cells in the human body
•Squamous—thin and flat with nucleus creating bulge
•Polygonal—irregularly angular shapes with four or more
sides
•Stellate—starlike shape
•Cuboidal—squarish and about as tall as is wide
•Columnar—taller than wide
•Spheroid to ovoid—round to oval
•Discoid—disc-shaped
•Fusiform—thick in middle, tapered toward the ends
•Fibrous—threadlike shape
•Note: Some of these cell shapes appear as in tissue
sections, but not their three-dimensional shape

4. 3-4
Basic Components of a Cell
•Light microscope reveals plasma membrane, nucleus,
and cytoplasm
–Cytoplasm—fluid between the nucleus and surface
membrane
•Resolution (ability to reveal detail) of electron
microscopes reveals ultrastructure
–Organelles, cytoskeleton, and cytosol or intracellular
fluid (ICF)
Nucleus
Plasma membrane
Nuclear envelope
Golgi vesicle
Golgi complex
Mitochondria
Ribosomes
2.0m
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© K.G. Muri/Visuals Unlimited
Figure 3.3

5. 3-5
Basic Components of a Cell

6. 3-6
Figure 3.5
Apical cell surface
Microfilaments
Secretory vesicle
undergoing exocytosis
Golgi vesicles
Golgi complex
Lateral cell surface
Intermediate filament
Lysosome
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Microtubule
Plasma membranes
Basement
membrane
Basal cell surface
Free ribosomes
Mitochondrion
Nucleolus
Nuclear envelope
Nucleus
Intercellular space
Centrosome
Centrioles
Secretory vesicle
Desmosome
Fat droplet
Hemidesmosome
Terminal web
Microvillus
Cell Organelles

7. Basic Components of a Cell
•Plasma membrane or cell membrane
–Surrounds cell, defines boundaries
–Made of proteins and lipids
–Composition and function can vary from one
region of the cell to another
•Cytoplasm or cytosol
–Organelles
–Cytoskeleton
–Cytosol (intracellular fluid, ICF)
•Extracellular fluid (ECF)
–Fluid outside of cell

8. 3-8
The Plasma Membrane
•Oily film of lipids with diverse proteins embedded
Figure 3.6b
Extracellular
face of
membrane
Intracellular
face of
membrane
(b)
Peripheral
protein
Extracellular fluid
Glycolipid
Glycoprotein
Carbohydrate
chains
Transmembrane
protein
Peripheral
protein
Channel
Intracellular fluid
Cholesterol
Proteins of
cytoskeleton
Phospholipid
bilayer
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9. 3-9
The Glycocalyx
(Glycolipids & Glycoproteins)
of Cell Membrane
•Unique fuzzy coat external to the plasma membrane
–Carbohydrate moieties of membrane glycoproteins and glycolipids
–Unique in everyone but identical twins
•Functions
–Protection – Cell adhesion
–Immunity to infection – Fertilization
–Defense against cancer – Embryonic development
–Transplant compatibility

10. 3-10
Membrane Proteins
•Functions of membrane proteins include the
following:
–Receptors, second-messenger systems, enzymes, ion
channels, carriers, cell-identity markers, cell-adhesion
molecules
Figure 3.8
Chemical
messenger Breakdown
products
Ions
CAM of
another cell
(a) Receptor
A receptor that
binds to chemical
messengers such
as hormones sent
by other cells
(b) Enzyme
An enzyme that
breaks down
a chemical
messenger and
terminates its
effect
(c) Ion Channel
A channel protein
that is constantly
open and allows
ions to pass
into and out of
the cell
(d) Gated ion channel
A gated channel
that opens and
closes to allow
ions through
only at certain
times
(e) Cell-identity marker
A glycoprotein
acting as a cell-
identity marker
distinguishing the
body’s own cells
from foreign cells
(f) Cell-adhesion
molecule (CAM)
A cell-adhesion
molecule (CAM)
that binds one
cell to another
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11. 3-11
Membrane Channel Proteins
•Transmembrane proteins with pores that
allow water and dissolved ions to pass through
membrane
–Some are constantly open
–Some are gated channels that open and close in
response to stimuli
•Ligand (chemically)-regulated gates
•Voltage-regulated gates
•Mechanically regulated gates (stretch and pressure)
•Play an important role in the timing of nerve
signals and muscle contraction

12. Plasma membrane
EXTRACELLULAR FLUID
CYTOPLASM
Lipid-soluble molecules diffuse
through the plasma membrane
Channel
protein
Small water-soluble
molecules and ions
diffuse through
membrane channels
Large molecules that cannot
diffuse through lipids cannot
cross the plasma membrane
unless they are transported
by a carrier mechanism
Figure 3-15 Diffusion across the Plasma Membrane

13. EXTRACELLULAR
FLUID
Sodium
potassium
exchange
pump
CYTOPLASM
Figure 3-19 The Sodium-Potassium Exchange Pump

14. 3-14
Membrane Transport
•Plasma membrane—a barrier and a gateway between the
cytoplasm and ECF
–Selectively permeable—allows some things through, and prevents
other things from entering and leaving the cell
•Passive transport mechanisms require no ATP
–Random molecular motion of particles provides the necessary energy
–Filtration, diffusion, osmosis
•Active transport mechanisms consumes ATP
–Active transport and vesicular transport
•Carrier-mediated mechanisms use a membrane protein to
transport substances from one side of the membrane to the
other

15. 3-15
Simple Diffusion
•Simple diffusion—the net
movement of particles from
area of high concentration
to area of low concentration
–Due to their constant,
spontaneous motion
•Also known as movement
down the concentration
gradient—concentration of
a substance differs from
one point to another
Figure 3.14
Down
gradient
Up
gradient
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16. 3-16
Osmosis
•Osmosis—flow of water
from one side of a selectively
permeable membrane to the
other
–From side with higher water
concentration to side with
lower water concentration
–Reversible attraction of water
to solute particles forms
hydration spheres
–Makes those water molecules
less available to diffuse back to
the side from which they came
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Side B
(a) Start
Solute
Water
Side A

17. 3-17
Effects of Tonicity on RBCs
Hypotonic, isotonic, and hypertonic solutions affect the fluid
volume of a red blood cell. Notice the crenated and swollen cells.
Figure 3.16a Figure 3.16b Figure 3.16c
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(a) Hypotonic (b) Isotonic (c) Hypertonic
© Dr. David M. Phillips/Visuals Unlimited

18. 3-18
Osmolarity and Tonicity
•Hypotonic solution
–Has a lower concentration of nonpermeating solutes than
intracellular fluid (ICF)
•High water concentration
–Cells absorb water, swell, and may burst (lyse)
•Hypertonic solution
–Has a higher concentration of nonpermeating solutes
•Low water concentration
–Cells lose water + shrivel (crenate)
•Isotonic solution
–Concentrations in cell and ICF are the same
–Cause no changes in cell volume or cell shape
–Normal saline

19. Solute
molecules
Water
molecules
In an isotonic saline solution, no osmotic flow occurs, and
these red blood cells appear normal as biconcave disc shape.
SEM of normal RBC
in an isotonic solution
Figure 3-17a Osmotic Flow across a Plasma Membrane

20. SEM of RBC in a
hypotonic solution
Immersion in a hypotonic saline solution results
in the osmotic flow of water into the cells. The
swelling may continue until the plasma membrane
ruptures or lyses by “hemolysis”.
Figure 3-17b Osmotic Flow across a Plasma Membrane

21. SEM of crenated RBCs
in a hypertonic solution
Exposure to a hypertonic solution results in the movement
of water out of the cell. The red blood cells shrivel and
become crenated.
Figure 3-17c Osmotic Flow across a Plasma Membrane

22. 3-22
Vesicular Transport
Phagocytosis keeps tissues free of debris and infectious microorganisms
Figure 3.21
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Particle
Pseudopod
Nucleus
Residue
Phagosome
Lysosome
Vesicle fusing
with membrane
Phagolysosome
1
2
3
4
5
6
7
A phagocytic cell encounters a
particle of foreign matter.
The cell surrounds
the particle with its
pseudopods.
The particle is phagocytized
and contained in a
phagosome.
The phagosome fuses
with a lysosome and
becomes a phagolysosome.
The indigestible
residue is voided by
exocytosis.
The phagolysosome
fuses with the
plasma membrane.
Enzymes from the
lysosome digest the
foreign matter.

23. 3-23
Cytoskeleton
Figure 3.25a
Microvilli
Microfilaments
Secretory
vesicle in
transport
Desmosome
Intermediate
filaments
Centrosome
Microtubule
undergoing
disassembly
Mitochondrion
Terminal web
Lysosome
Microtubule
Nucleus
Microtubule
in the process
of assembly
Intermediate
filaments
(a)
Basement
membrane
Hemidesmosome
Kinesin
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24. 3-24
The Nucleus
Figure 3.27a Figure 3.27b
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Nucleolus
Nucleoplasm
Nuclear
envelope
2 m(a) Interior of nucleus
Nuclear
pores
1.5 m(b) Surface of nucleus
a: © Richard Chao; b: © E.G. Pollock

25. 3-25
The Nucleus
•Nucleus—largest organelle (5 m in diameter)
–Most cells have one nucleus
–A few cells are anuclear or multinucleate
•Nuclear envelope—two unit membranes surround
nucleus
–Perforated by nuclear pores formed by rings of protein
•Regulate molecular traffic through envelope
•Hold two unit membranes together
•Nucleoplasm—cytoplasm of nucleus
–Chromatin (threadlike matter) composed of DNA and
protein
–Nucleoli—one or more dark masses where ribosomes
are produced

26. 3-26
Ribosomes
•Ribosomes—small circular granules that make
protein and RNA
–Found in nucleoli, cytosol, and surface of rough ER,
and nuclear envelope
•They “read” coded genetic messages
(messenger RNA) and assemble amino acids
into proteins

27. Golgi apparatus
Stacks of flattened
membranes (cisternae)
Functions:
Storage and packaging
of products and lysozyme
enzymes as vesicles
Mitochondria
Double membranes where
Inner membrane (cristae)
contains important enzymes
for metabolism
Function:
Produce ATP energy
Endoplasmic reticulum (ER)
Network of
membranous
channels
Functions:
Synthesis, storage,
and transport of
products
Rough ER
packages
newly made
proteins
Smooth ER
synthesizes
lipids and
carbohydrates
Peroxisomes
Vesicles that contain
enzymes
Functions:
Catabolism of organic
compounds and neutralization
of toxic compounds
NUCLEUS
 Plasma membrane
 Nonmembranous organelles
 Membranous organelles
Figure 3-1 Anatomy of a Cell (Part 5 of 8)

28. 3-28
•Endoplasmic reticulum—interconnected channels
called cisternae enclosed by unit membrane
•Rough endoplasmic reticulum—composed of
parallel, flattened sacs covered with ribosomes
–Produces proteins of the plasma membrane
–Synthesizes proteins that are packaged in other
organelles or secreted from cell
•Smooth endoplasmic reticulum
–Lack ribosomes so no protein synthesis
–Synthesizes steroids and lipids instead
–Manufactures lipid membranes of the cell
Endoplasmic Reticulum

29. 3-29
Golgi Complex
Figure 3.29
600nm
Golgi vesicles
Golgi
complex
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Visuals Unlimited

30. 3-30
Golgi Complex
•Golgi complex—a small system of cisternae that
synthesize carbohydrates and put the finishing
touches on protein and glycoprotein synthesis
–Receives newly synthesized proteins from rough ER
–Sorts them, cuts and splices some of them, adds
carbohydrate moieties to some, and packages the
protein into membrane-bound Golgi vesicles
•Some become lysosomes
•Some migrate to plasma membrane and fuse to it
•Some become secretory vesicles for later release

31. Golgi
apparatus
Autolysis
liberates
digestive
enzymes
Primary
lysosome
Reabsorption
Endosome
Damaged
organelle
Secondary
lysosome
Reabsorption
Secondary
lysosome
Endocytosis
Extracellular
solid or fluid
Exocytosis
ejects residue
Exocytosis
ejects residue
The lysosomal membrane
breaks down during autolysis
following injury to or death
of the cell.
A primary lysosome fuses
with an endosome containing
fluid or solid materials from
outside the cell.
A primary lysosome fuses
with the membrane of
another organelle like the
mitochondrion.
Activation of lysosomes
occurs when:
Figure 3-8 Lysosome Functions

32. 3-32
Lysosomes & Peroxisomes
•Lysosomes—vesicles that contain digestive
enzymes to digest food or kill pathogens (bacteria
and viruses)
–Autophagy—digest and dispose of worn out
mitochondria and other organelles
–Autolysis—“cell suicide”: some cells are meant to do a
certain job and then destroy themselves
•Peroxisomes—resemble lysosomes but contain
enzymes to detoxify or neutralize poisons
- Abundant in liver and kidney

33. 3-33
Lysosome and Peroxisomes
Figure 3.30a Figure 3.30b
1 m
(a) Lysosomes
Mitochondria
Lysosomes
Golgi
complex
0.3 m
(b) Peroxisomes
Smooth ER
Peroxisomes
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© Don Fawcett/Photo Researchers, Inc.

34. 3-34
Mitochondria
•Mitochondria—organelles specialized
for synthesizing ATP
•Variety of shapes: spheroid, rod-shaped,
kidney-shaped, or threadlike
•Surrounded by a double unit membrane
–Inner membrane has folds called cristae
–Spaces between cristae called matrix
•Matrix contains ribosomes, enzymes
used for ATP synthesis, small circular
DNA molecule
– Mitochondrial DNA (mtDNA)
•“Powerhouses” of the cell
–Energy is extracted from organic
molecules and transferred to ATP
Figure 3.31
Matrix
Crista
Outer membrane
Inner membrane
Intermembrane
space
Mitochondrial
ribosome
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35. CYTOPLASM
MATRIX
Pyruvate
Glycolysis
Glucose
Citric Acid
Cycle
ADP 
phosphate
Enzymes
and
coenzymes
of cristae
MITOCHONDRION
This is an overview of the role of mitochondria in energy
production. Mitochondria absorb short carbon chains (such as
pyruvate) and oxygen and generate carbon dioxide and ATP.
Figure 3-9b Mitochondria