Transcript cell theory

Chapter 4
Structure and
Function
of Cells
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Cells Are the Basic
Units of Life
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4.1 All organisms are
composed of cells
 The cell theory states
 A cell is the basic unit of life
 All living things are made up of cells
 New cells arise only from preexisting cells
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Figure 4.2A The sizes of living things and their components
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4.2 Metabolically active cells
are small in size

Surface-area-to-volume ratio
constrains increases in a cell’s size


Actively metabolizing cells need to be small
Cells that specialize in absorption have
modifications to increase the surface-areato-volume ratio
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Figure 4.2B Surface-area-to-volume relationships
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APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES
4.3 Microscopes allow
us to see cells
 Compound light microscope
 Multiple lenses increase magnifying power
 A condenser lens focuses light through specimen
 An objective lens magnifies the specimen’s image
 An ocular lens magnifies the image into the eye
 Electron microscope
 More magnifying power than light microscope
 Transmission electron microscope passes electrons
through specimen
 Scanning electron microscope collects and focuses
electrons scattered by the specimen
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Figure 4.3 Comparison
of three microscopes
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4.4 Prokaryotic cells
evolved first
 Prokaryotic cells
 Lack a membrane-bound nucleus
 Smaller than eukaryotic cells
 Have a single chromosome, semifluid
cytoplasm, and thousands of ribosomes
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Figure 4.4B
Prokaryotic cell
structure
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Figure 4.4A Size comparison of a eukaryotic cell and a prokaryotic cell
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Archaea and Bacteria
 Two domains of prokaryotic cells
 Different nucleic acid bases
 Bacteria cause many diseases, but are also
important in the environment for recycling
nutrients
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4.5 Eukaryotic cells contain
specialized organelles:
An overview
 Eukaryotic cells are third domain of cells
 Cytoskeleton - protein fibers that maintain cell
shape
 Have membrane-bound nucleus and organelles
 Endomembrane system: endoplasmic reticulum,
Golgi apparatus, and lysosomes
 Energy-related organelles: mitochondria and
chloroplasts
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Figure 4.5A Animal cell anatomy
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Figure 4.5B Plant cell anatomy
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Protein Synthesis Is a Major
Function of Cells
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4.6 The nucleus contains the cell’s
genetic information
 Nucleus contains chromatin, a network
of strands that condenses to form
chromosomes
 Chromosomes contain DNA which carries
genes, the units of heredity
 Nucleolus - dark region of chromatin with
ribosomal RNA (rRNA)
 Nuclear envelope separates the nucleus
from the cytoplasm, but has nuclear pores to
permit passage of ribosomal subunits
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Figure 4.6 Anatomy of the nucleus
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4.7 The ribosomes carry out
protein synthesis
 Ribosomes – non-membrane-bound
particles where protein synthesis occurs
 Endoplasmic reticulum (ER) – a
membranous system where ribosomes
attach and aid in protein synthesis
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Figure 4.7 Function of ribosomes
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4.8 The endoplasmic reticulum
synthesizes and transports
proteins and lipids
The ER attaches to the nuclear envelope
 Rough ER is studded with ribosomes that
synthesize proteins
 Smooth ER lacks proteins and is where lipids
are made
 Transport vesicles carry proteins and
lipids to Golgi apparatus for modification
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Figure 4.8 Rough ER (RER) and smooth ER (SER)
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4.9 The Golgi apparatus modifies
and repackages proteins
for distribution
 One side is directed toward the ER and
the other toward the cytoplasm
 Golgi apparatus sorts and packages
proteins and lipids in vesicles
 Vesicles are secreted from the cell membrane
via exocytosis
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Figure 4.9 Golgi
apparatus (graygreen) and
transport vesicles
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APPLYING THE CONCEPTS - HOW SCIENCE PROGRESSES
4.10 Pulse-labeling allows
observation of the
secretory pathway
 George Palade pulse-labeled the rough ER with
radioactive amino acids to observe the pathway
of protein secretion
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Vesicles and Vacuoles Have
Varied Functions
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4.11 Lysosomes digest
macromolecules and cell parts
 Lysosomes - membrane-bound vesicles produced by the
Golgi apparatus
 Important in recycling cellular material and digesting worn-out
organelles
 Tay Sachs disease – when a particular lysosomal enzyme is
nonfunctional
Figure 4.11 Lysosome
fusing with and destroying
spent organelles
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4.12 Peroxisomes break down
long-chain fatty acids
 Peroxisomes - small, membrane-bound
organelles resembling empty lysosomes
 Contain enzymes to digest excess fatty
acids
 Produces products used by mitochondria to
make ATP
 Produce cholesterol and phospholipids
found in brain and heart tissue
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4.13 Vacuoles have varied functions
in protists and plants
 Vacuoles – membranous sacs larger than vesicles and
usually store substances
 Example: toxic substances used in plant defense
 Central vacuole – found in plants, contains watery sap
and maintains turgor pressure
Figure 4.13 Central
vacuole of a plant cell
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4.14 The organelles of the
endomembrane system
work together
 Endomembrane system is a series of
membranous organelles that work together and
communicate via transport vesicles
 Includes: ER, Golgic apparatus, lysosomes and
transport vesicles
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Figure 4.14 The organelles of the endomembrane system
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A Cell Carries Out Energy
Transformations
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4.15 Chloroplasts capture solar
energy and produce carbohydrates
 Chloroplasts - type of plastid, an
organelle bounded by a double membrane
with a series of internal membranes
separated by a ground substance
 Endosymbiotic theory - from eukaryotic cell
engulfing a photosynthetic bacteria
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Figure 4.15
Chloroplast
structure
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4.16 Mitochondria break down
carbohydrates and produce ATP
 Mitochondria were also derived from
bacteria and therefore have a double
membrane
 Often called the powerhouse of the cell
because they produce most of the ATP
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Figure 4.16
Mitochondrion
structure
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APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES
4.17 Malfunctioning mitochondria
can cause human diseases
 Mutations in
mitochondrial DNA
(mtDNA) have been
linked to diseases
 Bi-products of ATP
formation can damage
mtDNA
 mtDNA mutations can be
inherited
 Example: Parkinsons or
Alzheimer patients have
more mtDNA mutations
Figure 4.17 Mitochondria within a
muscle cell
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The Cytoskeleton Maintains Cell
Shape and Assists Movement
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4.18 The cytoskeleton consists of
filaments and microtubules
 Actin filaments - long, thin flexible fibers in
bundled or mesh-like networks
 Play a structure role in the plasma membrane
 Creates pseudopods amoebas to crawl
 Actin filaments interact with motor molecules,
proteins that attach, detach, and reattach
causing movement
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Intermediate Filaments and
Microtubules
 Intermediate filaments - size between actin
filaments and microtubules
 Support nuclear envelope or plasma membrane and
are in cell-to-cell junctions
 Microtubules – made of globular protein tubulin
 Radiate from centrosome and maintain cell shape
and create tracks along which organelles move
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Figure 4.18 The
three types of
protein components
of the cytoskeleton
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4.19 Cilia and flagella
contain microtubules
 Cilia and flagella - whiplike structures of
cells
 Unicellular protists use them to move
 In our bodies cilia remove debris from
respiratory tract and move eggs along oviduct
 Grow from basal bodies - same structure
as centrioles, structures located outside
the nucleus and used in mitosis
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Figure 4.19 Flagellum
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In Multicellular Organisms,
Cells Join Together
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4.20 Modifications of cell surfaces
influence their behavior
 Plants have a primary cell wall of cellulose
microfibrils and a middle lamella of pectin
 Channels, plasmodesma, connect adjacent
cells allowing water and solutes through
 Animals cells have junctions between
plasma membranes
 Anchoring junctions prevent leakage
 Tight junctions seal in digestive justices
 Gap junctions allow cells to communicate
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Figure 4.20A Plant cells are joined by plasmodesmata
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Figure 4.20B Animal
cells are joined by
three different types
of junctions
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Connecting the Concepts:
Chapter 4
 Eukaryotic cells contain several types of
organelles.
 But not all eukaryotic cells contain every type of
organelle. Cells have many specializations of
structure for their particular functions.
 Red blood cells lack a nucleus allowing more room for
molecules of hemoglobin, the molecule that
transports oxygen in the blood
 Muscle cells are tubular and specialized to contract
 Nerve cells have very long extensions that facilitate
the transmission of impulses
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