Essentials of Anatomy & Physiology, 4th Edition Martini / Bartholomew Cell Structure and Function PowerPoint Lecture Outlines prepared by Alan Magid, Duke University Slides 1 to 102
Studying Cells Cell Theory: Four Basic Concepts Basic building blocks of all animals and plants Smallest functional units of life Products of cell division Basic homeostatic units
Studying Cells The Diversity of Cells in the Human Body Figure 3-1
Studying Cells Cytology Study of structure and function of cells Cytology depends on seeing cells Light microscopy (LM) Electron Microscopy (EM) Scanning EM (SEM) Transmission EM (TEM)
Studying Cells Overview of Cell Anatomy Extracellular fluid Also called interstitial fluid Cell Membrane Lipid barrier between outside and inside Cytoplasm (intracellular fluid) Around nucleus Cytosol + organelles
Studying Cells Anatomy of a Representative Cell Figure 3-2
The Cell Membrane Functions of the plasma membrane Physical isolation Regulation of exchange with the environment Sensitivity Structural support
The Cell Membrane Membrane Structure Phospholipid bilayer Molecular components Lipids Proteins Carbohydrates
The Cell Membrane The Cell Membrane Figure 3-3
The Cell Membrane Functions of Membrane Proteins Receptors Channels Carriers Enzymes Anchors Identifiers
The Cell Membrane Table 3-2
The Cell Membrane Membrane Transport Selective permeability Permeability factors Molecular size Electrical charge Molecular shape Lipid solubility PLAY Doors and Channels
The Cell Membrane Membrane Transport Processes Passive transport Diffusion Filtration Carrier-Mediated transport Facilitated transport Active transport PLAY Membrane Transport: Cell Membrane Barrier
The Cell Membrane Membrane Transport Definitions Diffusion Random movement down a concentration gradient (from higher to lower concentration) Osmosis Movement of water across a membrane down a gradient in osmotic pressure (from lower to higher osmotic pressure)
The Cell Membrane Diffusion PLAY Membrane Transport: Diffusion Figure 3-4
The Cell Membrane Diffusion Across Cell Membranes Figure 3-5 PLAY Membrane Transport: Fat- and Water-Soluble Molecules
The Cell Membrane Osmosis Figure 3-6
The Cell Membrane Key Note Things tend to even out, unless something like a cell membrane prevents this from happening. Across a freely permeable or water permeable membrane, diffusion and osmosis will quickly eliminate concentration gradients.
The Cell Membrane Osmotic Effects of Solutions on Cells Isotonic Cells maintain normal size and shape Hypertonic Cells lose water osmotically and shrink and shrivel Hypotonic Cells gain water osmotically and swell and may burst.
The Cell Membrane Osmotic Flow across a Cell Membrane Figure 3-7
The Cell Membrane Passive Membrane Transport Filtration Hydrostatic pressure pushes on water Water crosses membrane Solute follows water Filtration initiates urine formation
The Cell Membrane Carrier-Mediated Transport Membrane proteins as carriers Facilitated diffusion (no ATP required) Co-transport Counter-transport Active transport (ATP consumed) Independent of concentration gradients Ion pumps (e.g., Na-K exchange)
The Cell Membrane Facilitated Diffusion PLAY Membrane Transport: Facilitated Diffusion Figure 3-8
The Cell Membrane The Sodium- Potassium Exchange Pump Figure 3-9 PLAY Membrane Transport: Active Transport
The Cell Membrane Vesicular Transport Membranous vesicles Transport in both directions Endocytosis Movement into cell Receptor-mediated Pinocytosis Phagocytosis Exocytosis Movement out of cell
EXTRACELLULAR FLUID Ligands binding to receptors Exocytosis Ligand receptors Ligands Endocytosis Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Ligands removed Fused vesicle and lysosome Lysosome The membrane containing the receptor molecules separates from the lysosome. The vesicle returns to the surface. Figure 3-10 1 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Ligand receptors CYTOPLASM Figure 3-10 2 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Figure 3-10 3 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Figure 3-10 4 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. Fused vesicle and lysosome Lysosome Figure 3-10 5 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Fused vesicle and lysosome Lysosome Figure 3-10 6 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Ligands Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Lysosome The membrane containing the receptor molecules separates from the lysosome. Ligands removed Fused vesicle and lysosome Figure 3-10 7 of 8
EXTRACELLULAR FLUID Ligands binding to receptors Exocytosis Ligand receptors Ligands Endocytosis Receptor-Mediated Endocytosis Target molecules (ligands) bind to receptors in cell membrane. Areas coated with ligands form deep pockets in membrane surface. CYTOPLASM Coated vesicle Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Ligands removed Fused vesicle and lysosome Lysosome The membrane containing the receptor molecules separates from the lysosome. The vesicle returns to the surface. Figure 3-10 8 of 8
Cell membrane of phagocytic cell Lysosomes Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Undissolved residue This fusion activates digestive enzymes. The enzymes break down the structure of the phagocytized material. Residue is then ejected from the cell by exocytosis. Figure 3-11 1 of 8
Cell membrane of phagocytic cell Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Figure 3-11 2 of 8
Cell membrane of phagocytic cell Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Figure 3-11 3 of 8
Cell membrane of phagocytic cell Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Figure 3-11 4 of 8
Cell membrane of phagocytic cell Lysosomes Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Figure 3-11 5 of 8
Cell membrane of phagocytic cell Lysosomes Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM This fusion activates digestive enzymes. Figure 3-11 6 of 8
Cell membrane of phagocytic cell Lysosomes Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM This fusion activates digestive enzymes. The enzymes break down the structure of the phagocytized material. Figure 3-11 7 of 8
Cell membrane of phagocytic cell Lysosomes Phagocytosis A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Pseudopodium (cytoplasmic extension) Foreign object EXTRACELLULAR FLUID CYTOPLASM Undissolved residue This fusion activates digestive enzymes. The enzymes break down the structure of the phagocytized material. Residue is then ejected from the cell by exocytosis. Figure 3-11 8 of 8
The Cytoplasm Cytoplasm All the stuff inside a cell, not including the cell membrane and nucleus. The stuff : The cytosol The organelles
The Cytoplasm The Cytosol Intracellular fluid Dissolved nutrients and metabolites Ions Soluble proteins Structural proteins Inclusions
The Cytoplasm Intracellular-Extracellular Differences Substance Inside Outside K + High Low Na + Low High Enzymes High Low
The Cytoplasm Organelles Membranous organelles Isolated compartments Nucleus Mitochondria Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes
The Cytoplasm Organelles Nonmembranous organelles Cytoskeleton Microvilli Centrioles Cilia Flagella Ribosomes Proteasomes
The Cytoplasm Organelles: The Cytoskeleton Cytoplasmic strength and form Main components Microfilaments (actin) Intermediate filaments (varies) Microtubules (tubulin)
The Cytoplasm The Cytoskeleton Figure 3-12
The Cytoplasm Nonmembranous Organelles Centrioles Direct chromosomes in mitosis Microvilli Surface projections increase external area Cilia Move fluids across cell surface Flagella Moves cell through fluid Ribosome Makes new proteins Proteasome Digests damaged proteins
The Cytoplasm Membranous Organelles Endoplasmic reticulum Network of intracellular membranes for molecular synthesis Rough ER (RER) Contains ribosomes Supports protein synthesis Smooth ER (SER) Lacks ribosomes Synthesizes proteins, carbohydrates
The Cytoplasm The Endoplasmic Reticulum Figure 3-13
The Cytoplasm Membranous Organelles Golgi apparatus Receives new proteins from RER Adds carbohydrates and lipids Packages proteins in vesicles Secretory vesicles Membrane renewal vesicle Lysosomes
Endoplasmic reticulum CYTOSOL Lysosomes EXTRACELLULAR FLUID Cell membrane Secretory vesicles Transport vesicle Golgi apparatus (a) Membrane renewal vesicles (b) Exocytosis Vesicle Incorporation in cell membrane Figure 3-14 1 of 7
Endoplasmic reticulum CYTOSOL EXTRACELLULAR FLUID Cell membrane Transport vesicle (a) Figure 3-14 2 of 7
Endoplasmic reticulum CYTOSOL EXTRACELLULAR FLUID Cell membrane Transport vesicle Golgi apparatus (a) Figure 3-14 3 of 7
Endoplasmic reticulum CYTOSOL Lysosomes EXTRACELLULAR FLUID Cell membrane Transport vesicle Golgi apparatus (a) Figure 3-14 4 of 7
Endoplasmic reticulum CYTOSOL Lysosomes EXTRACELLULAR FLUID Cell membrane Transport vesicle Golgi apparatus (a) Membrane renewal vesicles Vesicle Incorporation in cell membrane Figure 3-14 5 of 7
Endoplasmic reticulum CYTOSOL Lysosomes EXTRACELLULAR FLUID Cell membrane Secretory vesicles Transport vesicle Golgi apparatus (a) Membrane renewal vesicles Vesicle Incorporation in cell membrane Figure 3-14 6 of 7
Endoplasmic reticulum CYTOSOL Lysosomes EXTRACELLULAR FLUID Cell membrane Secretory vesicles Transport vesicle Golgi apparatus (a) Membrane renewal vesicles (b) Exocytosis Vesicle Incorporation in cell membrane Figure 3-14 7 of 7
The Cytoplasm Membranous Organelles Lysosomes Packets of digestive enzymes Defense against bacteria Cleaner of cell debris Hazard for autolysis Suicide packets
The Cytoplasm Key Note Cells respond directly to their environment and help maintain homeostasis at the cellular level. They can also change their internal structure and physiological functions over time.
The Cytoplasm Membranous Organelles Mitochondria 95% of cellular ATP supply Double membrane structure Outer membrane very permeable Inner membrane very impermeable Folded into cristae Filled with matrix Studded with ETS complexes
The Cytoplasm Mitochondria Figure 3-15
The Cytoplasm Key Note Mitochondria provide most of the energy needed to keep your cells (and you) alive. They consume oxygen and organic substrates, and they generate carbon dioxide and ATP.
The Nucleus Properties of the Nucleus Exceeds other organelles in size Controls cellular operations Determines cellular structure Directs cellular function Nuclear envelope separates cytoplasm Nuclear pores penetrate envelope Enables nucleus-cytoplasm exchange
The Nucleus The Nucleus Figure 3-16
The Nucleus Chromosome Structure Location of nuclear DNA Protein synthesis instructions 23 pairs of human chromosomes Histones Principal chromosomal proteins DNA-Histone complexes Chromatin
The Nucleus Chromosome Structure Figure 3-17
The Nucleus Key Note The nucleus contains DNA, the genetic instructions within chromosomes. The instructions tell how to synthesize the proteins that determine cell structure and function. Chromosomes also contain various proteins that control expression of the genetic information.
The Nucleus The Genetic Code Triplet code Comprises three nitrogenous bases Specifies a particular amino acid A Gene Heredity carried by genes Sequence of triplets that codes for a specific protein
The Nucleus Protein Synthesis Transcription the production of RNA from a single strand of DNA Occurs in nucleus Produces messenger RNA (mrna) Triplets specify codons on mrna
DNA RNA polymerase Codon 1 mrna strand Promoter Codon 2 Gene Triplet 1 Triplet 2 Triplet 3 Triplet 4 1 2 3 4 Complementary triplets 2 Codon 1 RNA nucleotide Codon 3 Codon 4 (stop signal) KEY Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 1 of 5
DNA Gene KEY Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 2 of 5
DNA RNA polymerase Promoter Gene Triplet 1 Triplet 2 Triplet 3 1 2 3 Complementary triplets 2 Triplet 4 4 KEY Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 3 of 5
DNA RNA polymerase Promoter Gene Triplet 1 Triplet 2 Triplet 3 1 2 3 Complementary triplets 2 Codon 1 RNA nucleotide KEY Triplet 4 4 Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 4 of 5
DNA RNA polymerase Codon 1 mrna strand Promoter Codon 2 Gene Triplet 1 Triplet 2 Triplet 3 1 2 3 Complementary triplets 2 Codon 1 RNA nucleotide Codon 3 Codon 4 (stop signal) KEY Triplet 4 4 Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 5 of 5
The Nucleus Protein Synthesis Translation the assembling of a protein by ribosomes, using the information carried by the mrna molecule trnas carry amino acids Anticodons bind to mrna Occurs in cytoplasm PLAY Protein Synthesis: trna
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid The small and large ribosomal subunits interlock around the mrna strand. KEY Adenine Guanine Small ribosomal subunit trna Anticodon trna binding sites Cytosine Uracil (RNA) Thymine Start codon mrna strand Large ribosomal subunit A second trna arrives at the adjacent binding site of the ribosome. The anticodon of the second trna binds to the next mrna codon. The first amino acid is detached from its trna and is joined to the second amino acid by a peptide bond. The ribosome moves one codon farther along the mrna strand; the first trna detaches as another trna arrives. Peptide bond The chain elongates until the stop codon is reached; the components then separate. Small ribosomal subunit Stop codon Large ribosomal subunit Completed polypeptide Figure 3-19 1 of 6
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid KEY Adenine Guanine Cytosine Uracil (RNA) Thymine Small ribosomal subunit Start codon trna Anticodon trna binding sites mrna strand Figure 3-19 2 of 6
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid The small and large ribosomal subunits interlock around the mrna strand. KEY Adenine Guanine Small ribosomal subunit trna Anticodon trna binding sites Cytosine Uracil (RNA) Thymine Start codon mrna strand Large ribosomal subunit Figure 3-19 3 of 6
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid The small and large ribosomal subunits interlock around the mrna strand. KEY Adenine Guanine Small ribosomal subunit trna Anticodon trna binding sites Cytosine Uracil (RNA) Thymine Start codon mrna strand Large ribosomal subunit A second trna arrives at the adjacent binding site of the ribosome. The anticodon of the second trna binds to the next mrna codon. Stop codon Figure 3-19 4 of 6
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid The small and large ribosomal subunits interlock around the mrna strand. KEY Adenine Guanine Small ribosomal subunit trna Anticodon trna binding sites Cytosine Uracil (RNA) Thymine Start codon mrna strand Large ribosomal subunit A second trna arrives at the adjacent binding site of the ribosome. The anticodon of the second trna binds to the next mrna codon. The first amino acid is detached from its trna and is joined to the second amino acid by a peptide bond. The ribosome moves one codon farther along the mrna strand; the first trna detaches as another trna arrives. Peptide bond Stop codon Figure 3-19 5 of 6
NUCLEUS mrna The mrna strand binds to the small ribosomal subunit and is joined at the start codon by the first trna, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid The small and large ribosomal subunits interlock around the mrna strand. KEY Adenine Guanine Small ribosomal subunit trna Anticodon trna binding sites Cytosine Uracil (RNA) Thymine Start codon mrna strand Large ribosomal subunit A second trna arrives at the adjacent binding site of the ribosome. The anticodon of the second trna binds to the next mrna codon. The first amino acid is detached from its trna and is joined to the second amino acid by a peptide bond. The ribosome moves one codon farther along the mrna strand; the first trna detaches as another trna arrives. Peptide bond The chain elongates until the stop codon is reached; the components then separate. Small ribosomal subunit Stop codon Large ribosomal subunit Completed polypeptide PLAY Transcription and Translation Figure 3-19 6 of 6
The Nucleus Key Note Genes are the functional units of DNA that contain the instructions for making one or more proteins. The creation of specific proteins involves multiple enzymes and three types of RNA.
The Cell Life Cycle Cell division The reproduction of cells Apoptosis Genetically programmed death of cells Mitosis The nuclear division of somatic cells Meiosis The nuclear division of sex cells
The Cell Life Cycle The Cell Life Cycle Highly Variable Interphase duration Mitotic frequency Figure 3-20
The Cell Life Cycle DNA Replication Figure 3-21
The Cell Life Cycle Mitosis A process that separates and encloses the duplicated chromosomes of the original cell into two identical nuclei Four phases in mitosis Prophase Metaphase Anaphase Telophase
The Cell Life Cycle Cytokinesis Division of the cytoplasm to form two identical daughter cells
The Cell Life Cycle Mitotic Phases Prophase Chromosomes condense Chromatids connect at centromeres Metaphase Chromatid pairs align at metaphase plate Anaphase Daughter chromosomes separate Telophase Nuclear envelopes reform
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Metaphase Anaphase Telophase Separation Daughter chromosomes Metaphase plate Cleavage furrow Cytokinesis Daughter cells Figure 3-22 1 of 8
Nucleus Interphase Figure 3-22 2 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Centrioles (two pairs) Figure 3-22 3 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Figure 3-22 4 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Metaphase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Metaphase plate Figure 3-22 5 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Metaphase Anaphase Daughter chromosomes Metaphase plate Figure 3-22 6 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Metaphase Anaphase Telophase Daughter chromosomes Metaphase plate Cleavage furrow Figure 3-22 7 of 8
Interphase Nucleus Mitosis begins Early prophase Spindle fibers Late prophase Centrioles (two pairs) Centromeres Chromosome with two sister chromatids Metaphase Anaphase Telophase Separation Daughter chromosomes Metaphase plate Cleavage furrow Cytokinesis Daughter cells Figure 3-22 8 of 8
The Cell Life Cycle Key Note Mitosis is the separation of duplicated chromosomes into two identical sets and nuclei in the process of somatic cell division. PLAY Interphase, Mitosis, and Cytokinesis
The Cell Life Cycle Cell Division and Cancer Abnormal cell growth Tumors (also called, neoplasm) Benign Encapsulated Malignant Invasion Metastasis Cancer Disease that results from a malignant tumor
The Cell Life Cycle Key Note Cancer results from mutations that disrupt the control mechanism that regulates cell growth and division. Cancers most often begin where cells are dividing rapidly, because the more chromosomes are copied, the greater the chances of error.
Cell Diversity and Differentiation Somatic Cells All have same genes Some genes inactivate during development Cells thus become functionally specialized Specialized cells form distinct tissues Tissue cells become differentiated