Chapter 7 Body Systems
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Transcript Chapter 7 Body Systems
Chapter 3
Anatomy of Cells
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Slide 1
Functional Anatomy of Cells
The typical cell (Figure 3-1)
Also called composite cell
Varies in size; all are microscopic (Table 3-1)
Varies in structure and function (Table 3-2)
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Slide 2
Functional Anatomy of Cells
Cell structures
Plasma membrane—separates the cell from its
surrounding environment
Cytoplasm—thick gel-like substance inside of the
cell composed of numerous organelles suspended
in watery cytosol; each type of organelle is suited
to perform particular functions (Figure 3-2)
Nucleus—large membranous structure near the
center of the cell
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Slide 3
Cell Membranes
Each cell contains a variety of membranes:
Plasma membrane (Figure 3-3)
Membranous organelles—sacs and canals made
of the same material as the plasma membrane
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Slide 4
Cell Membranes
Fluid mosaic model—theory explaining how
cell membranes are constructed
Molecules of the cell membrane are arranged in a
sheet
The mosaic of molecules is fluid; that is, the
molecules are able to float around slowly
This model illustrates that the molecules of the cell
membrane form a continuous sheet
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Slide 5
Cell Membranes
Chemical attractions are the forces that hold
membranes together
Groupings of membrane molecules form rafts,
each of which float as a unit in the membrane
(Figure 3-4)
Rafts may pinch inward, bringing material into the
cell or organelle
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Slide 6
Cell Membranes
Primary structure of a cell membrane is a double
layer of phospholipid molecules
Heads are hydrophilic (water-loving)
Tails are hydrophobic (water-fearing)
Molecules arrange themselves in bilayers in water
Cholesterol molecules are scattered among the
phospholipids to allow the membrane to function
properly at body temperature
Most of the bilayer is hydrophobic; therefore water or
water-soluble molecules do not pass through easily
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Slide 7
Cell Membranes
Membrane proteins (Table 3-4)
A cell controls what moves through the membrane
by means of membrane proteins embedded in the
phospholipid bilayer
Some membrane proteins have carbohydrates
attached to them, forming glycoproteins that act as
identification markers
Some membrane proteins are receptors that react
to specific chemicals, sometimes permitting a
process called signal transduction
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Slide 8
Cytoplasm and Organelles
Cytoplasm—gel-like internal substance of
cells that includes many organelles
suspended in watery intracellular fluid called
cytosol
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Slide 9
Cytoplasm and Organelles
Two major groups of organelles (Table 3-3):
Membranous organelles are specialized sacs or
canals made of cell membranes
Nonmembranous organelles are made of
microscopic filaments or other nonmembranous
materials
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Slide 10
Cytoplasm and Organelles
Endoplasmic reticulum (Figure 3-5)
Made of canals with membranous walls and flat,
curving sacs arranged in parallel rows throughout
the cytoplasm; extend from the plasma membrane
to the nucleus
Proteins move through the canals
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Slide 11
Cytoplasm and Organelles
Endoplasmic reticulum (cont.)
Two types of endoplasmic reticulum:
• Rough endoplasmic reticulum
Ribosomes dot the outer surface of the membranous walls
Ribosomes synthesize proteins, which move toward the
Golgi apparatus and then eventually leave the cell
Function in protein synthesis and intracellular
transportation
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Slide 12
Cytoplasm and Organelles
Two types of endoplasmic reticulum (cont.)
• Smooth endoplasmic reticulum
No ribosomes border membranous wall
Functions are less well established and probably more
varied than for rough endoplasmic reticulum
Synthesizes certain lipids and carbohydrates and creates
membranes for use throughout cell
Removes and stores Ca++ from cell’s interior.
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Slide 13
Cytoplasm and Organelles
Ribosomes (Figure 3-6)
Many are attached to the rough endoplasmic
reticulum and many lie free, scattered through the
cytoplasm
Each ribosome is a nonmembranous structure
made of two pieces, a large subunit and a small
subunit; each subunit is composed of rRNA
Ribosomes in the endoplasmic reticulum make
proteins for “export” or to be embedded in the
plasma membrane; free ribosomes make proteins
for the cell’s domestic use
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Slide 14
Cytoplasm and Organelles
Golgi apparatus
Membranous organelle consisting of cisternae
stacked on one another and located near the
nucleus (Figure 3-7)
Processes protein molecules from the
endoplasmic reticulum (Figure 3-8)
Processed proteins leave the final cisterna in a
vesicle; contents may then be secreted to outside
the cell
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Slide 15
Cytoplasm and Organelles
Lysosomes (Figure 3-9)
Made of microscopic membranous sacs that have
“pinched off” from Golgi apparatus
The cell’s own digestive system; enzymes in
lysosomes digest the protein structures of
defective cell parts, including plasma membrane
proteins, and particles that have become trapped
in the cell
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Slide 16
Cytoplasm and Organelles
Proteasomes (Figure 3-10)
Hollow, protein cylinders found throughout the
cytoplasm
Break down abnormal/misfolded proteins and
normal proteins no longer needed by the cell
Break down protein molecules one at a time by
tagging each one with a chain of ubiquitin
molecules and unfolding it as it enters the
proteasome, then breaking apart peptide bonds
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Slide 17
Cytoplasm and Organelles
Peroxisomes
Small membranous sacs containing enzymes that
detoxify harmful substances that enter the cells
Often seen in kidney and liver cells
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Slide 18
Cytoplasm and Organelles
Mitochondria (Figure 3-11)
Made up of microscopic sacs; wall composed of
inner and outer membranes separated by fluid;
thousands of particles make up enzyme molecules
attached to both membranes
The “power plants” of cells; mitochondrial
enzymes catalyze series of oxidation reactions
that provide about 95% of cell’s energy supply
Each mitochondrion has a DNA molecule, allowing
it to produce its own enzymes and replicate copies
of itself
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Slide 19
Nucleus
Definition—spherical body in center of cell;
enclosed by an envelope with many pores
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Slide 20
Nucleus
Structure
Consists of nuclear envelope (composed of two
membranes each with essentially the same
molecular structure as plasma membrane)
surrounding nucleoplasm; nuclear envelope has
holes called nuclear pores (Figure 3-12)
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Slide 21
Nucleus
Structure (cont.)
Contains DNA (heredity molecules), which appear
as the following:
• Chromatin threads or granules in nondividing cells
• Chromosomes in early stages of cell division
• Functions of nucleus are functions of DNA molecules;
DNA determines both structure and function of cells and
heredity
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Slide 22
Cytoskeleton
The cell’s internal supporting framework
made up of rigid, rodlike pieces that provide
support and allow movement and
mechanisms that can move the cell or its
parts (Figure 3-13)
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Slide 23
Cytoskeleton
Cell fibers
Intricately arranged fibers of varying lengths that
form a three-dimensional, irregularly shaped
lattice
Fibers appear to support the endoplasmic
reticulum, mitochondria, and “free” ribosomes
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Slide 24
Cytoskeleton
Cell fibers (cont.)
Smallest cell fibers are microfilaments
(Figure 3-14)
• “Cellular muscles”
• Made of thin, twisted strands of protein molecules that lie
parallel to the long axis of the cell
• Microfilaments can slide past each other, causing
shortening of the cell
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Slide 25
Cytoskeleton
Cell fibers (cont.)
Intermediate filaments are twisted protein strands
slightly thicker than microfilaments; they form
much of the supporting framework in many types
of cells
Microtubules are tiny, hollow tubes that are the
thickest of the cell fibers; they are made of protein
subunits arranged in a spiral fashion; their function
is to move things around in the cell
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Slide 26
Cytoskeleton
Centrosome
An area of the cytoplasm near the nucleus that
coordinates the building and breaking of
microtubules in the cell
Nonmembranous structure also called the
microtubule-organizing center (MTOC)
Plays an important role during cell division
The general location of the centrosome is
identified by the centrioles
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Slide 27
Cytoskeleton
Cell extensions
Cytoskeleton forms projections that extend the
plasma membrane outward to form tiny, fingerlike
processes
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Slide 28
Cytoskeleton
There are three types of these processes; each
has specific functions (Figure 3-15):
• Microvilli—found in epithelial cells that line the intestines
and other areas where absorption is important; they help
to increase the surface area manyfold
• Cilia and flagella—cell processes that have cylinders
made of microtubules at their core; cilia are shorter and
more numerous than flagella; flagella are found only on
human sperm cells
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Slide 29
Cell Connections
Cells are held together by fibrous nets that
surround groups of cells (e.g., muscle cells),
or cells have direct connections to each other
There are three types of direct cell
connections (Figure 3-16)
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Slide 30
Cell Connections
Desmosome
Fibers on the outer surface of each desmosome
interlock with each other; anchored internally by
intermediate filaments of the cytoskeleton
Spot desmosomes, connecting adjacent
membranes, are like “spot welds” at various points
Belt desmosomes encircle the entire cell like
a collar
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Slide 31
Cell Connections
Gap junctions—membrane channels of
adjacent plasma membranes adhere to each
other; have two effects:
Form gaps or “tunnels” that join the
cytoplasm of two cells
Fuse two plasma membranes into a single
structure
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Slide 32
Cell Connections
Tight junctions
Occur in cells that are joined by “collars” of tightly
fused material
Molecules cannot permeate the cracks of tight
junctions
Occur in the lining of the intestines and other parts
of the body, where it is important to control what
gets through a sheet of cells
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Slide 33