Cells The Basic Unit of Life.

Cells The Basic Unit of Life

How to Study Cells Microscopes
Produce magnified images of structures too small to see with the unaided eye.

Types of Microscopes Light Microscope
Produce magnified images using rays of light Used to study living and dead material X magnification

Types of Microscopes Electron Microscopes
Use beams of electrons to produce magnified images Scanning Electron Microscopes Transmission Electron Microscopes Up to 1000 times more powerful than light microscopes

Types of Microscopes Scanning Electron Microscopes (SEM)
Scan the outside surface Produce 3D images Used to study dead organisms

SEM Images

Types of Microscopes Transmission Electron Microscopes (TEM)
Shine beams of electrons through a thin slice of a specimen Used to study internal structures Used to study dead organisms

TEM Images

Cell Theory All living things are made up of cells.
Cells are the basic units of structure and function in living things. New cells are produced from existing cells. Products of cell division Basic homeostatic units

The Diversity of Cells in the Human Body
Studying Cells The Diversity of Cells in the Human Body Figure 3-1

Studying Cells Cytology Cytology depends on seeing cells
Study of structure and function of cells Cytology depends on seeing cells Light microscopy (LM) Electron Microscopy (EM) Scanning EM (SEM) Transmission EM (TEM) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Studying Cells Figure 3-2

Organelles Membranous organelles Isolated compartments Nucleus
Mitochondria Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes

Organelles Nonmembranous organelles Cytoskeleton Microvilli Centrioles
Cilia Flagella Ribosomes Proteasomes

The Cytoplasm Cytoplasm The “stuff”:
All the “stuff” inside a cell, not including the cell membrane and nucleus. The “stuff”: The cytosol The organelles Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cytoplasm The Cytosol Intracellular fluid
Dissolved nutrients and metabolites Ions Soluble proteins Structural proteins Inclusions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cytoplasm Organelles: The Cytoskeleton
Cytoplasmic strength and form Main components Microfilaments (actin) Intermediate filaments (varies) Microtubules (tubulin) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

CYTOSOL (b) Golgi apparatus (a)
EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Lysosomes Secretory vesicles Transport vesicle (b) Exocytosis Golgi apparatus Membrane renewal vesicles Vesicle Incorporation in cell membrane (a) Figure 3-14 1 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID CYTOSOL (a) Endoplasmic reticulum Cell membrane
Transport vesicle (a) Figure 3-14 2 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

CYTOSOL Golgi apparatus (a)
EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Transport vesicle Golgi apparatus (a) Figure 3-14 3 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Lysosomes Transport vesicle Golgi apparatus (a) Figure 3-14 4 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Lysosomes Transport vesicle Golgi apparatus Membrane renewal vesicles Vesicle Incorporation in cell membrane (a) Figure 3-14 5 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Lysosomes Secretory vesicles Transport vesicle Golgi apparatus Membrane renewal vesicles Vesicle Incorporation in cell membrane (a) Figure 3-14 6 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

CYTOSOL (b) Golgi apparatus (a)
EXTRACELLULAR FLUID Endoplasmic reticulum CYTOSOL Cell membrane Lysosomes Secretory vesicles Transport vesicle (b) Exocytosis Golgi apparatus Membrane renewal vesicles Vesicle Incorporation in cell membrane (a) Figure 3-14 7 of 7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cytoplasm Membranous Organelles Lysosomes
Packets of digestive enzymes Defense against bacteria Cleaner of cell debris Hazard for autolysis “Suicide packets” Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cytoplasm Membranous Organelles Vacuoles & Vesicles Storage Water
Nutrients Salts Proteins Carbohydrates

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cytoplasm Figure 3-15

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Nucleus Chromosome Structure Figure 3-17

Plasma Membrane Functions of the plasma membrane Physical isolation
Regulation of exchange with the environment Sensitivity Structural support

Membrane structure Phospholipid bilayer Molecular components Lipids
Proteins Carbohydrates

Functions of Membrane Proteins
Receptors Sensitive to specific extracellular materials that bind to them and trigger a change in the cell’s activities Ex. Insulin increases rate of glucose absorption Channels Permits water, ions, or other solutes to pass through Ex. Calcium ion movement allows for muscle contraction

Carriers Bind and transport solutes across the cell membrane May or may not require energy Ex. Transport of glucose, potassium, and calcium ions in and out of the cell Enzymes Catalyze reactions in the extracellular fluid or within the cell

Anchors Attach the cell membrane to other structures to stabilize Inside the cell – anchor proteins bind to cytoskeleton Outside the cell – bind to extracellular proteins or other cells Identifiers (recognition) Identify cell as self or non-self, normal or abnormal, to the immune system

Selective Permeability
The cell membrane is selectively permeable Some substances can pass through others cannot

Cell Membrane Structure
Integral proteins Embedded into the phospholipid bilayer among the fatty acid tails lie at or near the inner or outer membrane or penetrate completely Form channels Receptor sites (with oligosaccharides attached)

Peripheral Proteins Loosely bound to membrane surface, easily detached Functions: Enzymes Scaffolding for plasma membrane Help change membrane shape during cell division, locomotion, and ingestion

Fluid Mosaic Model

Osmosis Diffusion Facilitated Diffusion Active Transport
Molecular Transport Osmosis Diffusion Facilitated Diffusion Active Transport

Membrane Transport Selective Permeability Permeability factors
Molecular size Very large molecules cannot pass through the protein channels Solubility in lipids Substances that dissolve easily in lipids are able to pass through the membrane more readily (ex. Oxygen, carbon dioxide, steroid hormones)

Charge of ions If an ion has a charge opposite that of the membrane are more attracted and pass through more readily Presence of carrier molecules Some integral proteins are capable of attracting and transporting substances across the membrane regardless of size, ability to dissolve in lipids, or charge

Membrane Transport Processes
Passive (physical) processes Diffusion Facilitated diffusion Osmosis Bulk flow Filtration Dialysis Active (physiological ) processes Active transport Endocytosis Phagocytosis

Transport Passive (physical) processes
Movement across the membrane without the use of energy Movement dependent on kinetic energy Molecules move on their own down a concentration gradient From high concentration to low concentration

Passive Transport Diffusion movement from high to low concentration
Movement continues until the rate of movement is equal in both directions Equilibrium Ex. Oxygen, carbon dioxide (lipid soluble) Ex. Sodium, potassium, chloride (diffuse through channels)

Passive Transport Facilitated Diffusion
Diffusion with help of integral proteins Can occur with large and/or lipid insoluble molecules Rate faster than simple diffusion; rate depends on: The difference in concentration Amount of carrier proteins available How quickly the carrier and substance combine Ex. Glucose

Passive Transport Osmosis Movement of water
Pass through integral protein channels Passage of water through a membrane creates osmotic pressure The pressure required to stop the flow of water through a membrane

Solutions Solute Solvent Concentration The dissolved substance
The substance the the solute is dissolved into Concentration The mass of the solute for a given volume of solvent

Passive Transport Bulk Flow
The movement of large numbers of ions, particles, or molecules in the same direction as a result of forces that push them Forces Osmotic or hydrostatic (water) pressure at rates greater than diffusion or osmosis alone Ex. Movement of substances through blood capillary membranes

Passive Transport Filtration
Movements of solvents (ie. Water and dissolved substances) across a membrane by gravity or mechanical pressure Usually hydrostatic pressure Movement form area of high pressure to area of lower pressure Occurs with small to medium sized molecules Ex. Kidneys

Passive Transport Dialysis
Separation of small molecules from large molecules by diffusion across a selectively permeable membrane Ex. Artificial kidney machines Patients blood exposed to dialysis membrane outside the body Small particle waste products pass from the blood into the solution surrounding the membrane Nutrients can pass from solution into blood

Types of Solutions Isotonic Solution Hypotonic Solution
Total concentrations of water molecules and solute molecules are the same on both sides of the membrane Movement occurs in both directions at equal rates Hypotonic Solution Lower concentration of solutes and higher concentration of water Water enters cells a faster rate than it leaves

Types of Solutions Hypertonic Solutions
Higher concentration of solutes and lower concentration of water Water leaves the cell faster than it enters

Active Transport Active Transport Transport across the cell membrane
Usually from areas of low concentration to areas of high concentration Requires the use of ATP Up to 40% of ATP is used for active transport

Active Transport Section 7-3 Molecule to be carried Low Concentration
Cell Membrane High Concentration Molecule being carried Low Concentration Cell Membrane High Concentration Energy Energy Go to Section:

Active Transport Endocytosis Large molecules and particles
Plasma membrane surrounds the substance, encloses it, and brings it into the cell 3 types Phagocytosis Pinocytosis Receptor-mediated endocytosis

Active Transport Phagocytosis Type of endocytosis “cell eating”
Use of pseudopodia to engulf large particles Phagocytic vesicle digested by enzymes from lysosome

Active Transport Pinocytosis “cell drinking”
Engulfed material consists of extracellular fluid rather than solid material Membrane folds inward, forms pinocytic vesicle that surrounds the liquid

Active Transport Receptor-mediated endocytosis
Cells take in large molecules Takes in ligands Lower concentration in the extracellular fluid Include amino acids, vitamins, iron, etc. Receptor proteins serve as binding sites Plasma membrane folds inward, creating a vesicle

Active Transport Exocytosis
Removal of large amounts of waste from the cell Membrane of the vesicle surrounding the material fuses to the cell membrane forcing the material out of the cell

EXTRACELLULAR FLUID Ligands Ligands binding to receptors Exocytosis
Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Exocytosis Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Fusion Detachment The membrane containing the receptor molecules separates from the lysosome. Lysosome Ligands removed Fused vesicle and lysosome The vesicle returns to the surface. Figure 3-10 1 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Ligands Ligand receptors CYTOPLASM
EXTRACELLULAR FLUID Ligands Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Ligand receptors CYTOPLASM Figure 3-10 2 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Ligands Receptor-Mediated Endocytosis Ligands binding to receptors 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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Ligands Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Figure 3-10 4 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Ligands Ligand receptors CYTOPLASM Fused vesicle and lysosome
EXTRACELLULAR FLUID Ligands Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Vesicles fuse with lysosomes. Fusion Lysosome Fused vesicle and lysosome Figure 3-10 5 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Ligands Ligand receptors CYTOPLASM Fused vesicle and lysosome
EXTRACELLULAR FLUID Ligands Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Fusion Lysosome Fused vesicle and lysosome Figure 3-10 6 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Ligands Ligands binding to receptors Endocytosis
Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Fusion Detachment The membrane containing the receptor molecules separates from the lysosome. Lysosome Ligands removed Fused vesicle and lysosome Figure 3-10 7 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

EXTRACELLULAR FLUID Ligands Ligands binding to receptors Exocytosis
Receptor-Mediated Endocytosis Ligands binding to receptors Target molecules (ligands) bind to receptors in cell membrane. Exocytosis Endocytosis Ligand receptors Areas coated with ligands form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Coated vesicle CYTOPLASM Vesicles fuse with lysosomes. Ligands are removed and absorbed into the cytoplasm. Fusion Detachment The membrane containing the receptor molecules separates from the lysosome. Lysosome Ligands removed Fused vesicle and lysosome The vesicle returns to the surface. Figure 3-10 8 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Vesicle Foreign object Undissolved residue
Phagocytosis Cell membrane of phagocytic cell Lysosomes 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. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object This fusion activates digestive enzymes. CYTOPLASM Pseudopodium (cytoplasmic extension) Undissolved residue The enzymes break down the structure of the phagocytized material. EXTRACELLULAR FLUID Residue is then ejected from the cell by exocytosis. Figure 3-11 1 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Phagocytosis Foreign object CYTOPLASM EXTRACELLULAR FLUID Figure 3-11
Cell membrane of phagocytic cell A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. Foreign object CYTOPLASM Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID Figure 3-11 2 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Phagocytosis Foreign object CYTOPLASM EXTRACELLULAR FLUID Figure 3-11
Cell membrane of phagocytic cell 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. Foreign object CYTOPLASM Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID Figure 3-11 3 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Vesicle Foreign object
Phagocytosis Cell membrane of phagocytic cell 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. The vesicle moves into the cytoplasm. Vesicle Foreign object CYTOPLASM Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID Figure 3-11 4 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Phagocytosis Cell membrane of phagocytic cell Lysosomes 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. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object CYTOPLASM Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID Figure 3-11 5 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Phagocytosis Cell membrane of phagocytic cell Lysosomes 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. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object This fusion activates digestive enzymes. CYTOPLASM Pseudopodium (cytoplasmic extension) EXTRACELLULAR FLUID Figure 3-11 6 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Phagocytosis Cell membrane of phagocytic cell Lysosomes 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. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object This fusion activates digestive enzymes. CYTOPLASM Pseudopodium (cytoplasmic extension) The enzymes break down the structure of the phagocytized material. EXTRACELLULAR FLUID Figure 3-11 7 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Vesicle Foreign object Undissolved residue
Phagocytosis Cell membrane of phagocytic cell Lysosomes 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. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object This fusion activates digestive enzymes. CYTOPLASM Pseudopodium (cytoplasmic extension) Undissolved residue The enzymes break down the structure of the phagocytized material. EXTRACELLULAR FLUID Residue is then ejected from the cell by exocytosis. Figure 3-11 8 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Protein Synthesis

The Genetic Code Triplet code A Gene Comprises three nitrogenous bases
Specifies a particular amino acid A Gene Heredity carried by genes Sequence of triplets that codes for a specific protein

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 Coded start and stop codons

Figure 3-18 3 of 5 DNA RNA polymerase Promoter Triplet 1 1 1 Gene
Complementary triplets Triplet 2 2 2 3 Triplet 3 3 4 KEY Triplet 4 4 Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 3 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 3-18 4 of 5 DNA RNA polymerase Promoter Triplet 1 1 1 Gene
Codon 1 Gene Complementary triplets Triplet 2 2 2 3 RNA nucleotide Triplet 3 3 4 KEY Triplet 4 4 Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 4 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 3-18 5 of 5 DNA RNA polymerase Codon 1 mRNA strand Codon 2
Promoter Codon 3 Triplet 1 1 1 Codon 1 Gene Codon 4 (stop signal) Complementary triplets Triplet 2 2 2 3 RNA nucleotide Triplet 3 3 4 KEY Triplet 4 4 Adenine Guanine Cytosine Uracil (RNA) Thymine Figure 3-18 5 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

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 20 different types of amino acids 1000s of different types of proteins

NUCLEUS 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 comple-mentary base pairs of the codon and anticodon. mRNA Amino acid Small ribosomal subunit tRNA KEY KEY Anticodon Adenine Guanine tRNA binding sites Cytosine Uracil (RNA) Thymine Start codon mRNA strand Figure 3-19 2 of 6 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

NUCLEUS 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 comple-mentary base pairs of the codon and anticodon. The small and large ribosomal subunits interlock around the mRNA strand. mRNA Amino acid Small ribosomal subunit tRNA KEY KEY Anticodon Adenine Guanine tRNA binding sites Cytosine Uracil (RNA) Large ribosomal subunit Thymine Start codon mRNA strand Figure 3-19 3 of 6 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

NUCLEUS 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 comple-mentary base pairs of the codon and anticodon. The small and large ribosomal subunits interlock around the mRNA strand. mRNA Amino acid Small ribosomal subunit tRNA KEY KEY Anticodon Adenine Guanine tRNA binding sites Cytosine Uracil (RNA) Large ribosomal subunit Thymine Start codon mRNA strand 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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

NUCLEUS 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 comple-mentary base pairs of the codon and anticodon. The small and large ribosomal subunits interlock around the mRNA strand. mRNA Amino acid Small ribosomal subunit tRNA KEY KEY Anticodon Adenine Guanine tRNA binding sites Cytosine Uracil (RNA) Large ribosomal subunit Thymine Start codon mRNA strand 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 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

NUCLEUS 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 comple-mentary base pairs of the codon and anticodon. The small and large ribosomal subunits interlock around the mRNA strand. mRNA Amino acid Small ribosomal subunit tRNA KEY KEY Anticodon Adenine Guanine tRNA binding sites Cytosine Uracil (RNA) Large ribosomal subunit Thymine Start codon mRNA strand 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. The chain elongates until the stop codon is reached; the components then separate. Small ribosomal subunit Peptide bond Completed polypeptide Stop codon Large ribosomal subunit Figure 3-19 6 of 6 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Cell Life Cycle Highly Variable Interphase duration
Mitotic frequency Figure 3-20

DNA Replication The Cell Life Cycle Figure 3-21

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

Four phases in mitosis 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

Cytokinesis Division of the cytoplasm to form two identical daughter cells

Mitotic Phases Prophase Metaphase Anaphase Telophase
Chromosomes condense Chromatids connect at centromeres Metaphase Chromatid pairs align at metaphase plate Anaphase Daughter chromosomes separate Telophase Nuclear envelopes reform

Spindle fibers Mitosis begins Centrioles (two pairs)
Interphase Early prophase Nucleus Spindle fibers Mitosis begins Centrioles (two pairs) Figure 3-22 3 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Nucleus Spindle fibers Mitosis begins Chromosome with two
Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Figure 3-22 4 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Metaphase Metaphase plate Figure 3-22 5 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Metaphase Anaphase Daughter chromosomes Metaphase plate Figure 3-22 6 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Metaphase Anaphase Telophase Daughter chromosomes Metaphase plate Cleavage furrow Figure 3-22 7 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Metaphase Anaphase Telophase Separation Daughter chromosomes Cytokinesis Metaphase plate Cleavage furrow Daughter cells Figure 3-22 8 of 8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Cell Division and Cancer
Abnormal cell growth Tumors (also called, neoplasm) Benign Encapsulated Malignant Invasion Metastasis Cancer Disease that results from a malignant tumor

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

Gametes (sex cells) Female = egg Male = sperm Produced through meiosis
Contain 23 chromosomes 22 autosomal chromosomes (autosomes) 1 sex chromosome All eggs contain X chromosome 50% of sperm contain X, 50% of sperm contain Y

Cells The Basic Unit of Life.

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