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CH 4: Cell Structure and Function Notes: Copy into Notebook
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 4Structure 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-area-to-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 (gray-green) 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