Cellular Anatomy

Chapter 2

Foundations

The Cell

Lecture Presentation by Steven Bassett Southeast Community College

• There are trillions of cells in the body • Cells are the structural “building blocks” of all plants and animals • Cells are produced by the division of preexisting cells • Cells form all the structures in the body • Cells perform all vital functions of the body

• There are two types of cells in the body: • Sex cells • Sperm in males and oocytes in females • Somatic cells • All the other cells in the body that are not sex cells

• The cell consists of: • Cytoplasm • Cytosol • Organelles • Plasmalemma • Cell membrane

Plasmalemma

Cytoplasm Divided into

Cytosol Organelles subdivided into

Nonmembranous Membranous Organelles Organelles

• Cytoskeleton • Mitochondria • Microvilli • Nucleus • Centrioles • Endoplasmic • Cilia reticulum • Flagella • Golgi apparatus • Ribosomes • Lysosomes • Peroxisomes

• Anatomical Structures of the Cell • Organelles • Nonmembranous organelles • Membranous organelles

• Organelles of the Cell • Nonmembranous organelles • Cytoskeleton • Microvilli • Centrioles • Cilia • Flagella • Ribosomes

Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion

Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum

Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes

• Organelles of the Cell • Membranous organelles • Mitochondria • Nucleus • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Peroxisomes

Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion

Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum

Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes

• Plasmalemma • A cell membrane composed of: • Phospholipids • Glycolipids • Protein • Cholesterol

Hydrophilic heads Hydrophobic tails Cholesterol

EXTRACELLULAR FLUID

Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer

Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM

a The plasmalemma

• Functions of the Plasmalemma • Cell membrane (also called phospholipid bilayer) • Major functions: • Physical isolation • Regulation of exchange with the environment (permeability) • Sensitivity • Cell-to-cell communication/Adhesion/Structural support

• Structure of the Plasmalemma • Called a phospholipid bilayer • Composed of two layers of phospholipid • Hydrophobic heads are at the surfaces (inside lining and outside lining) • Hydrophilic fatty acids (tails) “face toward each other” • Outer layer consists of glycolipids and glycoproteins • Glycolipids and glycoproteins form a glycocalyx coating • Inner layer does not consist of glycolipids or glycoproteins

Hydrophilic heads Hydrophobic tails Cholesterol

EXTRACELLULAR FLUID

Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer

Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM

a The plasmalemma

• Structure of the Plasmalemma • Composed of protein molecules • Peripheral proteins: attached to the glycerol portions of the fatty acids • Integral proteins: embedded within the cell membrane • Form channels such as gated channels • Channels open and close

Hydrophilic heads Hydrophobic tails Cholesterol

EXTRACELLULAR FLUID

Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer

Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM

a The plasmalemma

• Structure of the Plasmalemma • Composed of sterol molecules • Function to maintain fluidity of the membrane • An example is cholesterol

Hydrophilic heads Hydrophobic tails Cholesterol

EXTRACELLULAR FLUID

Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer

Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM

a The plasmalemma

• Membrane Permeability of the Plasmalemma • Passive processes • Diffusion • Osmosis • Facilitative diffusion • Active processes • Active transport • Endocytosis • Exocytosis

• Membrane Permeability of the Plasmalemma • Passive process: diffusion • Movement of molecules from an area of high concentration to an area of low concentration • Permeablity, concentration gradient, molecule size and charge, temperature affect the rate of movement • Small inorganic ions and small molecules are involved

Diffusion

Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. The difference between the high and low concentrations is Plasmalemma a concentration gradient. In diffusion, molecules move down a concentration Example:

gradient until the gradient is eliminated. When the concentration of CO2 inside a cell is greater than outside Factors Affecting Rate: the cell, CO2 diffuses out of the cell Membrane permeability; magnitude of the and into the extracellular fluid. concentration gradient; size, charge, and lipid solubility of the diffusing molecules; presence of membrane channel proteins; Extracellular CO2 temperature fluid Substances Involved (all cells): Gases, small inorganic ions and molecules, lipid-soluble materials

• Membrane Permeability of the Plasmalemma • Passive process: osmosis • Movement of water molecules from an area of high concentration of water to an area of low concentration of water • Permeability, concentration gradient, and opposing pressure affect the rate of movement • Only water molecules are involved

Osmosis

Osmosis is the diffusion of water molecules (rather than solutes) across a selectively permeable membrane. Note that water molecules diffusing toward an area of lower Example: water concentration are moving toward an area If the solute concentration outside of higher solute concentration. Because solute a cell is greater than the inside the cell, water molecules will move concentrations can easily be determined, they across the plasmalemma into the are used to determine the direction and force extracellular fluid. of osmotic water movement. Factors Affecting Rate: Size of the solute concentration gradient; opposing pressure Substances Involved: Water only Water Solute

• Membrane Permeability of the Plasmalemma • Passive process: facilitated diffusion • Solutes are passively transported by a carrier protein • Concentration gradient, size and charge of the solute, temperature, and number of carrier proteins affect the rate of movement • Glucose and amino acids are involved

Plasmalemma Facilitated diffusion Glucose

In facilitated diffusion, solutes are Extracellular Example: fluid Nutrients that are insoluble passively transported across a in lipids or too large to fit plasmalemma by a carrier protein. As through membrane in simple diffusion, the direction of channels may be trans- movement follows the concentration ported across the plasma- gradient. lemma by carrier proteins. Many carrier proteins move Factors Affecting Rate: a specific substance in one Magnitude of the concentration direction only, either into or gradient; size, charge, and solubility of Cytoplasm out of the cell, after first the solutes; temperature; availability binding the substance at a of carrier proteins Receptor Carrier Carrier protein releases specific receptor site. Substances Involved (all cells): site protein glucose into cytoplasm Glucose and amino acids

• Membrane Permeability of the Plasmalemma • Active process: active transport • Solutes are actively transported by a carrier protein regardless of the concentration gradient • ATP, number of carrier proteins affect the rate of movement • Sodium, potassium, calcium, and magnesium ions are involved

Extracellular fluid Active transport 3 Na+ Example: Using active transport, carrier proteins can move One of the most common specific substances across the plasmalemma despite an examples of active transport opposing concentration gradient. Carrier proteins that is the sodium–potassium Sodium–potassium move one solute in one direction and another solute in exchange pump. For each exchange pump the opposite direction are called exchange pumps. molecule of ATP consumed, three sodium ions are Factors Affecting Rate: ejected from the cell and two + Availability of carrier proteins, solutes, and ATP 2 K ATP ADP potassium ions are reclaimed Substances Involved: Cytoplasm from the extracellular fluid. Na+, K+, Ca2+, Mg2+ (all cells); other solutes in special cases

• Membrane Permeability of the Plasmalemma • Active process: endocytosis • Pinocytosis: vesicles bring small molecules into the cell • A variety of stimuli affect the rate of movement (not fully understood) • Extracellular fluid is involved • Phagocytosis: vesicles bring solid particles into the cell • Presence of extracellular pathogens affects the rate of movement • Bacteria, viruses, foreign matter, and cell debris are involved

Endocytosis Endocytosis is the packaging of extracellular materials into a vesicle (a membrane-bound sac) for importation into the cell.

Pinocytosis Phagocytosis Receptor-mediated endocytosis In pinocytosis, vesicles form at the In phagocytosis, vesicles form at plasmalemma and bring extracellular fluid the plasmalemma to bring solid Target molecules Extracellular fluid and small molecules into the cell. This particles into the cell. This process is process is often called “cell drinking.” often called “cell eating.” Factors Affecting Rate: Pinocytotic Example: Presence and abundance of Receptor vesicle Water and small extracellular pathogens or debris proteins Vesicle forming molecules within a containing vesicle may enter Substances Involved: target the cytoplasm Bacteria, viruses, cell debris, and Cytoplasm molecules through carrier- other foreign material Example: mediated transport Each cell has or diffusion. In receptor-mediated specific sensitivities Example: endocytosis, target molecules to extracellular Large particles are bind to specific receptor proteins materials, depend- brought into the cell Cell on the membrane surface, ing on the kind of when cytoplasmic Pseudopodium triggering vesicle formation. receptor proteins extends to extensions (called present in the surround object pseudopodia) engulf Factors Affecting Rate: plasmalemma. the particle and form Number of receptors on the a phagocytic vesicle. plasmalemma and the concentration of target molecules (called ligands) Factors Affecting Rate: Cell Stimulus and mechanism not under- Substances Involved (all cells): stood Many examples, including cholesterol and iron ions Substances Involved: Extracellular fluid and its associated solutes Phagocytic vesicle

• Membrane Permeability of the Plasmalemma • Active process: exocytosis • The release of intracellular material to the extracellular area • Requires ATP and calcium ions for movement • Fluid and cellular waste and secretory products are involved

Material ejected from cell Exocytosis

Exocytosis is the release of Factors Affecting Rate: fluids and/or solids from cells Stimulus and mechanism incompletely Example: when intracellular vesicles fuse understood; requires ATP and calcium Cellular wastes that with the plasmalemma. ions accumulate in vesicles Cell are ejected from the cell. Substances Involved (all cells): Fluid and cellular wastes; secretory products are released by some cells

• Extensions of the Plasmalemma: Microvilli • Fingerlike projections of the plasmalemma • Absorb material from the ECF • Increase the surface area of the plasmalemma • Microvilli can bend back and forth in a waving manner • This movement helps to circulate extracellular fluid • This movement helps absorb nutrients

Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion

Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum

Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes

• The Cytoplasm • Term for all of the intracellular material • Cytosol • Consists of the ICF (intracellular fluid) • Consists of nutrients, protein, and waste products • Organelles • These are intracellular structures that perform specific functions

Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion

Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum

Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes

• The Cytoplasm • Cytosol • Contains a higher concentration of potassium ions and a lower concentration of sodium ions as compared to the ECF • Consists of a net negative charge • Contains a high concentration of protein • Contains a small quantity of carbohydrates • Contains a large reserve of amino acids and lipids • Contains large amounts of inclusions

• The Cytoplasm • Organelles • Nonmembranous organelles • Cytoskeleton Centrioles Cilia Flagella Ribosomes • Membranous organelles • Mitochondria Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes

• Nonmembranous Organelles (details) • The cytoskeleton consists of: • Microfilaments • Intermediate filaments • Thick filaments • Microtubules

• Nonmembranous Organelles (details) • Microfilaments: consist of actin protein • Anchor cytoskeleton to integral proteins • Stabilize the position of membrane proteins • Anchor plasmalemma to the cytoplasm • Produce movement of the cell or a change in the cell’s shape

• Nonmembranous Organelles (details) • Intermediate filaments • Provide strength • Stabilize organelle position • Transport material within the cytosol

• Nonmembranous Organelles (details) • Thick filaments: composed of myosin protein • Found in muscle cells: involved in muscle contraction

• Nonmembranous Organelles (details) • Microtubules: composed of tubulin protein • Involved in the formation of centrioles • perform a function during cell reproduction • Involved in moving duplicated chromosomes to opposite poles of the cell • perform a function during cell reproduction • Involved in anchoring organelles • Involved in moving cell organelles • Involved in moving the entire cell • Involved in moving material across the surface of the cell

Microvilli

Microfilaments

Plasmalemma SEM × 30,000

b A SEM image of the Terminal web microfilaments and microvilli of an intestinal cell.

Mitochondrion

Intermediate filaments

Endoplasmic reticulum a The cytoskeleton provides strength and structural Microtubule support for the cell and its organelles. Interactions Secretory LM × 3200 between cytoskeletal elements vesicle are also important in moving c Microtubules in a living organelles and in changing cell, as seen after the shape of the cell. fluorescent labeling.

• Nonmembranous Organelles (details) • Examples of microtubules • Centrioles • Cilia • Flagella

a A centriole consists of nine microtubule triplets (9 + 0 array). The centrosome contains a pair of centrioles oriented Plasmalemma at right angles to Microtubules one another.

Basal body

b A cilium contains nine pairs of microtubules surrounding a central pair (9 + 2 array).

Power stroke Return stroke

c A single cilium swings forward TEM × 240,000 and then returns to its original position. During the power stroke, the cilium is relatively stiff, but during the return stroke, it bends and moves parallel to the cell surface.

• Nonmembranous Organelles (details) • Ribosomes • Free ribosomes: float in the cytoplasm • Fixed ribosomes: attached to the endoplasmic reticulum • Both are involved in producing protein

Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion

Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum

Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes

a A centriole consists of nine microtubule triplets (9 + 0 array). The centrosome contains a pair of centrioles oriented Plasmalemma at right angles to Microtubules one another.

Basal body

b A cilium contains nine pairs of microtubules surrounding a central pair (9 + 2 array).

Power stroke Return stroke

• Membranous Organelles (details) • Double-membraned organelles • Mitochondria: produce ATP • Nucleus: contains chromosomes • Endoplasmic reticulum: network of hollow tubes • Golgi apparatus: modifies protein • Lysosomes: contain cellular digestive enzymes • Peroxisomes: contain catalase to break down hydrogen peroxide

• Membranous Organelles (details) • Mitochondria • Consist of cristae • Consist of mitochondrial matrix • Produce ATP

Inner membrane Cytoplasm of cell Cristae Matrix

Organic molecules and O2

CO2 Outer membrane ATP

Matrix Cristae Enzymes

TEM × 61,776

• Membranous Organelles (details) • Nucleus: control center of the cell • Nucleoplasm • Nuclear envelope • Perinuclear space • Nuclear pores • Nuclear matrix

Perinuclear space

Nucleoplasm

Chromatin

Nucleolus

Nuclear envelope

Nuclear pores

TEM × 4828

a TEM showing important nuclear structures.

Nuclear envelope

Perinuclear space

Nuclear pore

b A nuclear pore and the perinuclear space.

Inner membrane of nuclear envelope

Broken edge of outer membrane

Outer membrane of nuclear envelope

SEM × 9240

c The cell seen in this SEM was frozen and then broken apart so that internal structures could be seen. This technique, called freeze-fracture, provides a unique perspective on the internal organization of cells. The nuclear envelope and nuclear pores are visible; the fracturing process broke away part of the outer membrane of the nuclear envelope, and the cut edge of the nucleus can be seen.

• Membranous Organelles: Nucleus • Chromosomes: • DNA wrapped around proteins called histones • Nucleosomes • Chromatin

Histones

Nucleosome

Chromatin in nucleus Loosely coiled nucleosomes, Nucleus of nondividing cell forming chromatin.

a In cells that are not dividing, the DNA is loosely coiled, forming a tangled network known as chromatin. DNA double helix

Sister chromatids

Centromere Kinetochore

Supercoiled region

Dividing cell Visible chromosome

b When the coiling becomes tighter, as it does in preparation for cell division, the DNA becomes visible as distinct structures called chromosomes. Chromosomes are composed of two sister chromatids which attach at a single point, the centromere. Kinetochores are the region of the centromere where spindle fibers attach during mitosis.

• Membranous Organelles (details) • Endoplasmic reticulum (ER) • There are two types • Rough endoplasmic reticulum (RER) • Smooth endoplasmic reticulum (SER)

• Membranous Organelles (details) • Rough endoplasmic reticulum • Consists of fixed ribosomes • Proteins enter the ER

Rough endoplasmic reticulum with fixed Ribosomes (attached) ribosomes

Free ribosomes Smooth endoplasmic reticulum

Endoplasmic TEM × 11,000 Reticulum

Cisternae

Free Nucleus ribosomes

Small ribosomal subunit

Large ribosomal Endoplasmic subunit reticulum with attached fixed ribosomes b An individual ribosome, TEM × 73,600 consisting of small a Both free and fixed ribosomes can and large subunits. be seen in the cytoplasm of this cell.

• Membranous Organelles (details) • Smooth endoplasmic reticulum • Synthesizes lipids, steroids, and carbohydrates • Storage of calcium ions • Detoxification of toxins

• Membranous Organelles (details) • Golgi apparatus • Synthesis and packaging of secretions • Packaging of enzymes (modifies protein) • Renewal and modification of the plasmalemma

Vesicles

Maturing (trans) face Forming (cis) face

Golgi apparatus TEM × 83,520

• Membranous Organelles (details) • Lysosomes • Fuse with phagosomes to digest solid materials • Recycle damaged organelles • Sometimes rupture, thus killing the entire cell (called autolysis)

• Membranous Organelles (details) • Peroxisomes • Consist of catalase • Abundant in liver cells • Convert hydrogen peroxide to water and oxidants

• Membrane Flow • This is the continuous movement and recycling of the cell membrane • Transport vesicles connect the endoplasmic reticulum with the Golgi apparatus • Secretory vesicles connect the Golgi apparatus with the plasmalemma • Vesicles remove and recycle segments of the plasmalemma

Cisterna Forming (cis) face

Golgi Apparatus Synthesis and Cytoplasm Packaging of Secretions: Steps

Transport vesicle 2 Secretory products are packaged into transport vesicles that eventually bud off from the ER. These transport vesicles then fuse to create the forming (cis) face of the Golgi apparatus.

1 Protein and glycoprotein Rough ER synthesis occurs in the rough endoplasmic reticulum (RER). Some of these proteins and glycoproteins remain within the ER.

Endoplasmic Reticulum mRNA Ribosome

Plasmalemma Secretory material Packaging of Renewal or Synthesis and Enzymes for Use Modification of Packaging in the Cytosol the Plasmalemma of Secretions

Secretory Exocytosis vesicle at the surface of a cell

TEM × 75,000 Plasmalemma Cytoplasm

Maturing (trans) face Secretory vesicle Synthesis and Packaging of Secretions: Steps Lysosome

4 The maturing (trans) face generates vesicles that carry materials away from the Golgi apparatus.

3 Each cisterna physically moves from the forming face to the maturing face, carrying with it its Cisterna Forming (cis) face associated proteins. This process is called cisternal progression.

Cytoplasm Golgi Apparatus

• Many cells form permanent or temporary attachment to other cells • Attach via cell adhesion molecules (CAMs) • Attach via cellular cement (proteoglycans) • Examples of Intercellular Attachment • Communicating junctions • Adhering junctions • Tight junctions • Anchoring junctions

• Communicating Junctions • Also called gap junctions • Two cells held together via protein called connexon • This protein is a type of channel protein • Attach via cell adhesion molecules (CAMs) • Attach via cellular cement (proteoglycans)

Tight junction

Embedded proteins (connexons)

Zonula adherens Terminal web Button desmosome Communicating b Communicating junction junctions permit Hemidesmosome the free diffusion of ions and small molecules between two cells. a A diagrammatic view of an epithelial cell showing the major types of intercellular connections.

• Adhering Junctions • Tight junctions, also called occluding junctions • Prevent the movement of water and other molecules from passing between the cells

• Anchoring Junctions • Zona adherens (adhesion belt) is a sheetlike anchoring material • Provides strong links that cells can shed from the body in sheets (ex. dandruff) • Macula adherens (desmosome) is a small, localized anchoring junction • Most abundant in superficial layers of the skin

Tight junction Interlocking junctional proteins Tight junction

Zonula adherens Terminal web Button desmosome Zonula Communicating adherens junction Hemidesmosome c A tight junction is formed by the fusion of the outer layers of two plasmalemmae. Tight junctions prevent the diffusion of fluids a A diagrammatic view of an epithelial cell showing the major and solutes between the cells. types of intercellular connections.

Tight junction

Zonula adherens Terminal web Button desmosome Communicating junction Hemidesmosome

a A diagrammatic view of an epithelial cell showing the major types of intercellular connections. Intermediate filaments (cytokeratin) d Anchoring junctions attach one cell to another. Cell adhesion A macula adherens has a molecules more organized network (CAMs) of intermediate filaments. Dense area An adhesion belt is a form of anchoring junction that Intercellular encircles the cell. This cement complex is tied to the microfilaments of the terminal web. © 2015 Pearson Education, Inc. Intercellular Attachment

• Anchoring junctions • Focal adhesions (focal contacts) • Connect intracellular microfilaments to protein fibers • Found in epithelial tissue that migrates during wound repair • Hemidesmosomes • Found in connecting cells that are exposed to a lot of abrasion • Examples are the cornea of the eye, skin, vaginal tissue, oral cavity, and esophagus

Tight junction

Zonula adherens Terminal web Button desmosome Communicating junction Hemidesmosome

a A diagrammatic view of an epithelial cell showing the major types of intercellular connections.

Clear layer Basal Dense lamina layer e Hemidesmosomes attach an epithelial cell to extracellular structures, such as the protein fibers in the basal lamina.

• Cell reproduction consists of special events • Interphase • Mitosis • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis • Overlaps with anaphase and telophase

• Cell Reproduction (Interphase) • Everything inside the cell is duplicating

• Consists of G1, S, and G2 phases

• G1: duplication of organelles and protein synthesis • S: Chromosome replication and DNA synthesis and histone synthesis

• G2: protein synthesis

DNA polymerase

Segment 2 DNA nucleotide

KEY Segment 1 Adenine DNA polymerase Guanine

Cytosine Thymine

• Cell Reproduction (Mitosis) • Prophase • The first phase of mitosis • Metaphase • Paired chromatids line up in the middle of the nuclear region • Anaphase • Paired chromatids separate to opposite poles of the cell • Telophase • Two new nuclear membranes begin to form

Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Early prophase Late prophase Nuclear Chromosomal membrane Centromere microtubules

Nucleus

Daughter cells

Chromosome Astral Daughter Cleavage Spindle with two sister Metaphase rays chromosomes furrow fibers chromatids plate Centrioles Chromosomal (two pairs) microtubules

• Cell Reproduction (Cytokinesis) • Cell membrane begins to invaginate, thus forming two new cells • Many times this phase actually begins during anaphase • This is the conclusion of cell reproduction

S INTERPHASE DNA replication, synthesis of histones G2 G1 Protein Normal synthesis cell functions plus cell growth, THE duplication of CELL organelles, CYCLE protein synthesis M

MITOSIS AND CYTOKINESIS Indefinite period (See Figure 2.17)

G0 Specialized cell functions