Download Chapter 3 Cells- Structure & Function Part II

3
Cells and Tissues
PART B
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
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Selective Permeability
 The plasma membrane allows some materials
to pass while excluding others
 This permeability includes movement into
and out of the cell
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Cellular Physiology: Membrane Transport
 Membrane Transport – movement of
substances into and out of the cell
 Transport is by two basic methods
 Passive transport
 No energy is required
 Active transport
 The cell must provide metabolic energy
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Movement Through Cell Membrane
 Passive Mechanisms of transport require no
cellular energy
 Ex:
 Simple Diffusion
 Facilitated Diffusion
 Osmosis
 Filtration
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Passive Transport Processes
 Diffusion
 Molecules move
from high
concentration
to low
concentration,
or down a
concentration
gradient
 Equilibrium- Molecules tend to distribute
themselves evenly within a solution
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DIFFUSION ANIMATION
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Figure 3.9
Diffusion through the Plasma Membrane
Figure 3.10
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Passive Transport Processes
 Facilitated diffusion
 Substances require a protein carrier (or
Carrier Molecule) for passive transport
 The rate of facilitated diffusion is limited to
the number of carrier molecules in the
membrane and/or the number of molecules
available for transport.
 Insulin promotes facilitated diffusion of
glucose
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Facilitated Diffusion
• diffusion across a membrane with the help of a channel
or carrier molecule
• glucose and
amino acids
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Passive Transport Processes
 Osmosis –
 simple diffusion of water from area of higher
concentration to lower concentration
 Osmotic Pressure- the amount of pressure (on
surface of liquid) needed to stop osmosis
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Osmosis
• movement of water through a selectively permeable membrane
from region of higher concentration to region of lower concentration
• water moves toward a higher concentration of solutes
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Osmosis
Osmotic Pressure – ability of osmosis to generate enough
pressure to move a volume of water
Osmotic pressure increases as the concentration of nonpermeable
solutes increases
• hypertonic – higher
osmotic pressure
• hypotonic – lower
osmotic pressure
• isotonic – same
osmotic pressure
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Passive Transport
 These are red blood cells in three
different solutions:
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Passive Transport
 Hypertonic Solution
 Has more solute
particles (thus less
H2O) than a cell in
that solution
 Result: Plasmolysiscell shrinks
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Passive Transport
 Hypotonic Solution
 Has less solute particles
(thus more H2O) than a
cell in that solution
 Result: Cytolysis- cell
bursts
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Passive Transport
 Isotonic Solution
 Has the same
concentration of
solute particles as a
cell in that solution
 Result: Cell remains
unchanged
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Passive Transport
 Can you identify the solution each cell
is in and explain what happens to each
cell?
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Passive Transport Processes
 Filtration
 Water and solutes are forced through a
membrane by fluid, or hydrostatic pressure
 Ex: Blood pressure forces small molecules &
water out through capillary walls creating tissue
fluid while larger protein molecules remain
inside capillary.
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Filtration
• smaller molecules are forced through porous membranes
• hydrostatic pressure important in the body
• molecules leaving blood capillaries
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Active Transport Processes
 Transport substances that are unable to pass by
diffusion
 They may be too large
 They may not be soluble in the fat core of the
membrane
 They may have to move against a concentration
gradient
 Two common forms of active transport
 Solute pumping – Active Transport
 Bulk transport – Endocytosis, Exocytosis
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Active Transport Processes
 Active Mechanisms require
cellular energy (ATP)
 Active Transport Particles move from
an area of lower
concentration to
higher concentration
 Up to 40% of cell’s
energy supply is
used for active
transport
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Active Transport Processes
 Solute pumping
 Amino acids, some sugars and ions are
transported by solute pumps
 ATP energizes protein carriers, and in
most cases, moves substances against
concentration gradients
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ACTIVE TRANSPORT ANIMATION
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Active Transport Processes
Figure 3.11
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Active Transport Processes
 Bulk transport
 Endocytosis
 A portion of the cell membrane forms
vesicle to carry in particles too large for
diffusion or pumping
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Endocytosis
Figure 3.13a
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Active Transport Processes
 Types of endocytosis
 Pinocytosis – cell drinking:
 Portion of cell membrane becomes indented
and surrounds tiny droplets of liquid.
Membrane pinches off and carries liquid into
cytoplasm where it releases contents
 Phagocytosis – cell eating:
 Solids are engulfed by indented portion of
cell membrane which then pinches off and
acts as vesicle to carry & empty solids into
cytoplasm
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Active Transport Processes
 Bulk transport
 Exocytosis
 Moves materials out of the cell
 Material is carried in a membranous vesicle
 Vesicle migrates to plasma membrane
 Vesicle combines with plasma membrane
 Material is released to the outside
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Exocytosis
Figure 3.12a
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Cell Life Cycle
 Cells have two major periods
 Interphase
 Cell grows
 Cell carries on metabolic processes
 Cell division
 Cell replicates itself
 Function is to produce more cells for growth
and repair processes
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DNA Replication
 Genetic material
duplicated and readies
a cell for division into
two cells
 Occurs toward the
end of interphase
 DNA uncoils and
each side serves
as a template
Figure 3.14
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Events of Cell Division
 Mitosis
 Division of the nucleus
 Results in the formation of two daughter nuclei
 Cytokinesis
 Division of the cytoplasm
 Begins when mitosis is near completion
 Results in the formation of two daughter cells
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Cell Life Cycle
 Interphase
 Cell growth
 The cell carries out
normal metabolic
activity (life processes)
 Not cell division
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Stages of Mitosis
 Prophase
 Nuclear membrane
breaks down
 Spindle fibers form
 Centrioles move to
opposite poles
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Stages of Mitosis
 Metaphase
 Chromosomes line
up in middle of cell
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Stages of Mitosis
 Anaphase
 Chromosomes pull
apart
 Chromosomes move
across cell toward
opposite poles
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Stages of Mitosis
 Telophase
 Chromosomes arrive at
poles
 Nuclear membrane
reforms
 Spindle fibers break down
 Cytokinesis- cell divides
into 2 new cells
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Stages of Mitosis
Figure 3.15
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Stages of Mitosis
Figure 3.15(cont)
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Mitosis
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Stem and Progenitor Cells
 Differentiation:
 Cellular
specialization
 DNA turned
on/off
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