Lecture Presentations
for Integrated Biology and Skills for Success in Science
Banks, Montoya, Johns, & Eveslage
Week # 8 Lecture – pp 15-128
Cells and Their Membranes
 By the end of the lecture today, students will be
able to:
State the cell theory
Define cell biology
Describe the different classes of cells in the human body
Describe the functions of the plasma membrane
Describe the components of the plasma membrane and explain the role of
each component, including lipids and proteins
 Differentiate between microvilli, cilia and flagellum
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Modern Cell Theory
 All organisms are composed of cells and cell products
 Cell is the simplest structural and functional unit of life
 cells are alive
 An organism’s structure and functions are due to the activities of its
cells
 Cells come only from preexisting cells, not from nonliving matter
 therefore, all life traces its ancestry to the same original cells
 Cells of all species have many fundamental similarities in their
chemical composition and metabolic mechanisms
 Cell biology  study of cells (i.e., their morphology, physiological
properties, organelles, interactions with the environment, life cycles,
division and death)
http://www.youtube.com/watch?v=4OpBylwH9D
U
Cell Shapes
 about 200 types of cells in the human body
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Squamous - thin and flat with nucleus creating bulge
Polygonal - irregularly angular shapes with 4 or more sides
Stellate – starlike shape
Cuboidal – squarish and about as tall as they are 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 shapes are cell appearance in tissue sections, but
not their 3 dimensional shape
Cell Shapes
Squamous
Cuboidal
Columnar
Polygonal
Stellate
Spheroid
Discoid
Fusiform (spindle-shaped)
Fibrous
Two Classes of cells in the Human
Body
 Sex cells, also known as germ cells or reproductive cells,
are either sperm cells of males or oocyte cells of females.
 Somatic cells are the cells that make up everything else in
the body.
Cell Size
 Human cell size
 most from 10 - 15 micrometers (µm) in diameter
 egg cells (very large)100 µm diameter
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barely visible to the naked eye
 nerve cell at 1 meter long
longest human cell
 too slender to be seen with naked eye
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 Limitations on cell size
 cell growth increases volume more than surface area
 surface area of a cell is proportional to the square of its diameter
 volume of a cell is proportional to the cube of its diameter
 nutrient absorption and waste removal utilize surface area
 if cell becomes too large, may rupture like overfilled water balloon
 http://projects.cbe.ab.ca/ict/udlsci/udlscience/biology/cells/saVol/notes
/saVol.htm
Major Constituents of Cell
 plasma (cell) membrane
 surrounds cell
 made of proteins and lipids
 composition and function can vary from one
region of the cell to another
 cytoplasm
 organelles
 cytoskeleton
 cytosol (intracellular
fluid - ICF)
 extracellular fluid – ECF
 fluid outside of cell
Apical cell surface
Microfilaments
Microvillus
Terminal web
Desmosome
Secretory vesicle
undergoing
exocytosis
Fat droplet
Secretory vesicle
Intercellular
space
Centrosome
Centrioles
Golgi vesicles
Golgi complex
Lateral cell surface
Free ribosomes
Intermediate filament
Nucleus
Lysosome
Nucleolus
Microtubule
Nuclear
envelope
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Mitochondrion
Plasma membranes
Hemidesmosome
Basal cell surface
Basement
membrane
Plasma Membrane
unit membrane – forms the border of the cell and many of its organelles
-appears as a pair of dark parallel lines around cell
(viewed with the electron microscope)
plasma membrane – unit membrane at cell surface
-defines cell boundaries
.
Plasma membrane
of upper cell
-governs interactions with other cells
Intercellular space
Plasma membrane
of lower cell
-controls passage of materials in and out of cell
-intracellular face – side that faces cytoplasm
-extracellular face – side that faces outward
Nuclear envelope
Nucleus
(a )
100 nm
.
Membrane Lipids
 98% of molecules in plasma membrane are lipids
 Phospholipids
 75% of membrane lipids are phospholipids
 amphiphilic molecules arranged in a bilayer
 hydrophilic phosphate heads face water on each side of membrane
 hydrophobic tails – directed toward the center, avoiding water
 drift laterally from place to place
 movement keeps membrane fluid
Plasma Membrane
Extracellular fluid
Peripheral
protein
Glycolipid
Glycoprotein
Carbohydrate
chains
Extracellular
face of
membrane
Phospholipid
bilayer
Channel
Peripheral
protein
Cholesterol
Transmembrane
protein
Intracellular fluid
Intracellular
face of
membrane
Proteins of
cytoskeleton
(b)
 Oily film of lipids with diverse proteins embedded
Membrane Protein Functions
 receptors, second-messenger systems, enzymes, ion channels,
carriers, cell-identity markers, cell-adhesion molecules
.
Chemical
messenger
Breakdown
products
Ions
(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
CAM of
another 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 cellidentity 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
http://www.youtube.com/watch?v=y31DlJ6uGgE
Microvilli
 Extensions of membrane (1-2 m)
 serves to increase cell’s surface area
 best developed in cells specialized in absorption
 gives 15 – 40 times more absorptive surface area
 on some cells they are very dense and appear as a fringe – “brush
border”
 milking action of actin
 actin filaments shorten microvilli

pushing absorbed contents down into cell
Microvilli
.
Glycocalyx
Microvillus
Actin
microfilaments
(a)
(b)
1.0 µm
.
Actin microfilaments are found in center of each microvilli.
0.1 µm
Cilia
 Hairlike processes 7-10m long
 single, nonmotile primary cilium found on nearly every cell
 “antenna’ for monitoring nearby conditions
 sensory in inner ear, retina, nasal cavity, and kidney
 Motile cilia – respiratory tract, uterine tubes, ventricles of the brain, efferent ductules of
testes
 beat in waves
 sweep substances across surface in same direction
 power strokes followed by recovery strokes
.
Mucus
Saline
layer
Epithelial
cells
1
2
3
Power stroke
(a)
(b)
4
5
6
Recovery stroke
7
Structure of Cilia
.
Cilia
(a)
.
10 m
Flagella
 tail of the sperm - only functional flagellum
 whiplike structure with axoneme identical to cilium
 much longer than cilium
 stiffened by coarse fibers that supports the tail
 movement is more undulating, snakelike
 no power stroke or recovery stroke as in cilia
http://www.youtube.com/watch?v=dXVGDwOtKU
Exit Quiz
 1).
 2).
 3).
 4).
 5).
Name the three fundamental parts of the cell theory and
identify who introduced each of these parts to the scientific
community.
Why are the majority of cells observed to be so small?
What are the major components to a cell? What are the
primary functions of each of these components?
What are the seven major functions of proteins in a cell
membrane?
What are the fundamental differences between cilia and
flagella?