CellsCells

Chapter 3Chapter 3

I. OverviewI. Overview

Cell Membrane Cell Membrane Cytoplasm Cytoplasm

Cytosol Cytosol Organelles Organelles

Nonmembranous: Cytoskeleton, Microvilli, Nonmembranous: Cytoskeleton, Microvilli, Centrioles, Cilia, Flagella, Ribosomes Centrioles, Cilia, Flagella, Ribosomes

Membranous: Mitochondria, Nucleus, Membranous: Mitochondria, Nucleus, Endoplasmic Reticulum, Golgi Apparatus, Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Peroxisomes, Vesicles Lysosomes, Peroxisomes, Vesicles

II. II. Plasma MembranePlasma Membrane (Cell Membrane) (Cell Membrane) "Fluid Mosaic Model" - plasma membrane "Fluid Mosaic Model" - plasma membrane

is composed of a double layer (bilayer) of is composed of a double layer (bilayer) of     phospholipid molecules with proteins     phospholipid molecules with proteins that float/move among the phospholipids, that float/move among the phospholipids, yet the yet the     plasma membrane is stable.     plasma membrane is stable.

Proteins function.... Proteins function.... As cell markers for recognition by immune As cell markers for recognition by immune

system system As receptors (e.g for hormones) As receptors (e.g for hormones) As catalysts As catalysts Transportation Transportation

Proteins in the membrane... Proteins in the membrane... integral proteins (maintain selective integral proteins (maintain selective

transport) transport) peripheral proteins (catalyst and peripheral proteins (catalyst and

mechanical function) mechanical function)

The plasma membrane also contains a The plasma membrane also contains a myriad of biological compounds such myriad of biological compounds such as glycoproteins, glycolipids, and as glycoproteins, glycolipids, and proteoglycans (all referred to as proteoglycans (all referred to as glycocalyx) that extend outward from glycocalyx) that extend outward from

the plasma membranethe plasma membrane

III. III. CytoplasmCytoplasm Cytoplasm is the material found inside the cell Cytoplasm is the material found inside the cell

and is divided into two subdivisions: cytosol and is divided into two subdivisions: cytosol     and organelles.     and organelles. CytosolCytosol (intracellular fluid) contains dissolved (intracellular fluid) contains dissolved

nutrients, ions, soluble and insoluble nutrients, ions, soluble and insoluble     proteins, and waste products.     proteins, and waste products.

OrganellesOrganelles are structures that perform are structures that perform specific functions within the cell and are specific functions within the cell and are classified as classified as     membranous and non-membranous    membranous and non-membranous. .

Mitochondria Rod-like, double membrane, inner membrane folded into projections called cristae; Site of ATP synthesis.

Ribosomes Dense particles consisting of two subunits, each composed of ribosomal RNA and proteins; can be free or it can be attached to ER; site of protein synthesis

E. R. (rough) Coiling membrane system with ribosomes attached; proteins synthesized are packaged into vesicles for transport to the golgi apparatus

E. R. (smooth) Coiling membrane system lacking ribosomes; synthesizes lipids and carbohydrates

Golgi apparatus 

Stack of smooth membrane sacs adjacent to the nucleus; modifies synthesized proteins, then packages the proteins (e.g. lysosomes & peroxisomes) in vesicles for transport around/out of cell

Lysosomes Membranous sacs containing hydrolytic enzymes used in cell digestion

Peroxisomes Membranous sacs containing oxidative enzymes (e.g. peroxidase) that degrade toxic compounds such as hydrogen  peroxide

Vesicles  Membrane bound sac that transports cellular material

MicrofilamentsFilaments containing the contractile protein actin; part of the cytoskeleton and functions in intracellular movement

Intermediate filamentsProtein fibers that provides strength, stabilize the position of organelles, and transport materials within the cytoplasm

Microtubules Hollow tubes composed of the globular protein tubulin; microtubules provide strength and rigidity and anchoring major organelles

Thick filaments   Large and long strands of myosin protein found in muscle cells that interact with thin actin filaments to produce muscle contraction

Centrioles  Cylindrical structure composed of nine triplets of microtubules; centrioles direct the movement of DNA during cell division as well as form the bases of cilia and flagella

Microvilli  Small, finger-shaped projections of the cell membrane that actively absorb fluid and nutrients

CiliaCell surface projections composed of microtubules; cilia move to propel substance across the cell surface

Flagella Larger and longer cilia that provides cellular locomotion (e.g. human sperm)

Nucleus Structure housing genetic information and is surrounded by a membrane (nuclear envelope)

Endoplasmic ReticulumEndoplasmic Reticulum

IV. IV. Membrane Transport ProcessesMembrane Transport Processes Transportation of materials across the cell Transportation of materials across the cell

membrane is determined by the components in the membrane is determined by the components in the membrane that impart permeability. membrane that impart permeability.

Most cells have Most cells have selective permeabilityselective permeability, free , free passage of some materials and restricts the passage passage of some materials and restricts the passage of others. of others.

Permeability may be based on size, electrical charge, Permeability may be based on size, electrical charge, molecular shape, solubility, etc... Passage across the molecular shape, solubility, etc... Passage across the membrane is classified as membrane is classified as activeactive (requiring energy) (requiring energy) andand passive passive (not requiring energy) (not requiring energy)

Membrane transport processes: Membrane transport processes: PassivePassive

DiffusionDiffusion - net movement of particles from an area of - net movement of particles from an area of higher concentration to an area of lower concentration. higher concentration to an area of lower concentration.

OsmosisOsmosis - diffusion of water through a selectively - diffusion of water through a selectively permeable membrane permeable membrane

Facilitated diffusionFacilitated diffusion - diffusion of a substance with - diffusion of a substance with the aid of a membrane carrier. the aid of a membrane carrier.

FiltrationFiltration - movement of water and solutes through a - movement of water and solutes through a semipermeable membrane from a region of higher semipermeable membrane from a region of higher hydrostatic pressure to a region of lower hydrostatic hydrostatic pressure to a region of lower hydrostatic pressure pressure

b) b) Osmosis Osmosis – movement of a solvent – movement of a solvent (water) through a semi- permeable (water) through a semi- permeable membrane down a concentration membrane down a concentration gradient (higher to lower)gradient (higher to lower)

Solutions:Solutions:

IsotonicIsotonic

HypertonicHypertonic

Hypotonic Hypotonic

A human red blood cell is composed of A human red blood cell is composed of 0.9% salt and 99.1% water. If this cell 0.9% salt and 99.1% water. If this cell is placed in a solution of 0.9% salt is placed in a solution of 0.9% salt and 99.1% water (saline) the solution and 99.1% water (saline) the solution is is isotonicisotonic and the blood cell will and the blood cell will remain unchangedremain unchanged

IsotonicIsotonic

The same RBC is placed in a beaker The same RBC is placed in a beaker of distilled water (100% Hof distilled water (100% H22O and 0% O and 0% salt), water will enter the cell and salt), water will enter the cell and cause it to burst (lysis). Water goes cause it to burst (lysis). Water goes from higher conc. to lower conc. This from higher conc. to lower conc. This solution is solution is hypotonichypotonic (hypo=less salt (hypo=less salt in solution).in solution).

HypotonicHypotonic

The same RBC is placed in a beaker of The same RBC is placed in a beaker of 50% salt water (50% H50% salt water (50% H22O and 50% O and 50% salt), water will leave the cell and salt), water will leave the cell and cause it to shrink (crenation). Water cause it to shrink (crenation). Water goes from higher conc. to lower conc. goes from higher conc. to lower conc. This solution is This solution is hypertonichypertonic (hyper=more salt in solution).(hyper=more salt in solution).

HypertonicHypertonic

ActiveActive Active transport Active transport - movement of a substance (with - movement of a substance (with

the aid of a membrane carrier) through a membrane the aid of a membrane carrier) through a membrane against its concentration gradient. against its concentration gradient.

Exocytosis Exocytosis - substances enclosed in a vesicle fuses - substances enclosed in a vesicle fuses with the plasma membrane, the vesicle then with the plasma membrane, the vesicle then ruptures, releasing the substances outside the cell. ruptures, releasing the substances outside the cell.

Endocytosis Endocytosis (types): (types): PhagocytosisPhagocytosis - the cell membrane extends - the cell membrane extends

outward and encloses large particles which are outward and encloses large particles which are then transported into the cell.then transported into the cell.

PinocytosisPinocytosis - particles attach to the cell - particles attach to the cell membranes which collapses, causing particles to membranes which collapses, causing particles to be taken into the cell. be taken into the cell.

Receptor-mediatedReceptor-mediated - pinocytotic movement - pinocytotic movement initiated by protein receptors on the plasma initiated by protein receptors on the plasma membrane. membrane.

Movement of particle may be.... Movement of particle may be.... Symport - movement of two or more Symport - movement of two or more

different kinds of material in the same different kinds of material in the same direction across the cell membrane. direction across the cell membrane.

Uniport - movement of one type of Uniport - movement of one type of material in one direction across the cell material in one direction across the cell membrane. membrane.

Antiport - moving two types of material Antiport - moving two types of material across the cell membrane in opposite across the cell membrane in opposite directions. directions.

V. V. Cell DivisionCell Division (Cell Life Cycle) (Cell Life Cycle) Multicellular organisms develop from a Multicellular organisms develop from a

zygote, which is formed by the fusion of a zygote, which is formed by the fusion of a sperm and an egg (gametes). Each gamete sperm and an egg (gametes). Each gamete has half the compliment of chromosomes has half the compliment of chromosomes (haploid number) and when combined gives (haploid number) and when combined gives rise to a zygote with a complete set (diploid rise to a zygote with a complete set (diploid number) of chromosomes. In order for the number) of chromosomes. In order for the zygote to develop into a multicellular zygote to develop into a multicellular organism, it must repeatedly undergo organism, it must repeatedly undergo cellular divisions. The series of events a cell cellular divisions. The series of events a cell (or zygote) undergoes that ultimately (or zygote) undergoes that ultimately produces a new cell is called the cell cycle. produces a new cell is called the cell cycle.

NucleusNucleus- located in the center of the cell- located in the center of the cell- controls all functions of organelles- controls all functions of organelles- cell reproduction/division takes place- cell reproduction/division takes place- DNA (Deoxyribonucleic Acid) is housed- DNA (Deoxyribonucleic Acid) is housed

- blueprint of heredity- blueprint of heredity- as cell divides the DNA coil tightly, - as cell divides the DNA coil tightly,

called called chromatin, to form chromosomes chromatin, to form chromosomes (46)(46)- bound by nuclear envelope: double layered - bound by nuclear envelope: double layered membrane enclosing nucleoplasmmembrane enclosing nucleoplasm

Nucleoli: are darkly stained areas within the Nucleoli: are darkly stained areas within the nucleus that indicate rapid RNA synthesis. nucleus that indicate rapid RNA synthesis.

Cell Growth and reproduction: Cell Growth and reproduction: produces two identical daughter cells produces two identical daughter cells from one parent cellfrom one parent cell

- cell life cycle has two major sections- cell life cycle has two major sections

Interphase (cell growth; Interphase (cell growth; notnot dividing)dividing)

GG11 phase : growthphase : growth

SS phase: growth and DNA phase: growth and DNA synthesissynthesis

GG22 phase: growth and final phase: growth and final preparation for cell preparation for cell

divisiondivision

Mitotic phase (M): dividing phaseMitotic phase (M): dividing phase

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase

IPMATIPMAT

Interphase: GInterphase: G1 1 , S and G, S and G22 phases. (90% of phases. (90% of its time)its time)

GG11 (gap 1): (gap 1): cell grows vigorously and cell grows vigorously and metabolically very active. metabolically very active.

- depending on cell type, this - depending on cell type, this phase may last minutes to years.phase may last minutes to years.

- centrioles begin replicating- centrioles begin replicating

SS: DNA replicates itself; chromatin : DNA replicates itself; chromatin condenses. Ensures daughter cells condenses. Ensures daughter cells receive identical genetic information.receive identical genetic information.

DNA replication (S phase)DNA replication (S phase)

GG22: phase is very brief.: phase is very brief.

- centriole replication is complete- centriole replication is complete

- ready to divide- ready to divide

Mitotic phase (M):Mitotic phase (M):

ProphaseProphase: Chromosomes are visible.: Chromosomes are visible.

- early prophase: longest phase of mitosis.- early prophase: longest phase of mitosis.

- chromatin condenses to form - chromatin condenses to form chromosomes.chromosomes.

- centriole pairs start to separate/nuclear - centriole pairs start to separate/nuclear membrane breaks down.membrane breaks down.

- mitotic spindles (microtubules) start to - mitotic spindles (microtubules) start to developdevelop

late prophase: late prophase:

- centrioles migrate away from each - centrioles migrate away from each to opposite poles of cell.to opposite poles of cell.

Metaphase:Metaphase: (meta = middle) (meta = middle)

- chromosomes cluster toward the - chromosomes cluster toward the center of cell. center of cell.

- centromeres align along the equator of - centromeres align along the equator of the spindlethe spindle

- enzyme separase will separate the - enzyme separase will separate the chromatid.chromatid.

Anaphase: Anaphase: (“apart”) shortest phase. (“apart”) shortest phase.

- centromeres of the chromosomes split- centromeres of the chromosomes split

- each chromatid becomes its own - each chromatid becomes its own chromosomechromosome

- Each chromosome is pulled to opposite - Each chromosome is pulled to opposite polepole

Telophase:Telophase: begins when chromosomal begins when chromosomal movement stops.movement stops.

- chromosomes uncoil; goes back to fine - chromosomes uncoil; goes back to fine threads of chromatin.threads of chromatin.

- new nuclear envelope forms- new nuclear envelope forms

- cytoplasm pinches inward forming a - cytoplasm pinches inward forming a cleavage furrow (cytokinesis)cleavage furrow (cytokinesis)

Somatic (body) cells contain a Somatic (body) cells contain a diploid diploid number of chromosomes. number of chromosomes.

Human cells contain two sets of Human cells contain two sets of chromosomes (one member from chromosomes (one member from each pair is inherited from each each pair is inherited from each parent); parent); homologous chromosomeshomologous chromosomes

2n (n= # of different 2n (n= # of different chromosomes). n=23 in humans chromosomes). n=23 in humans 2(23)= 462(23)= 46

22 pairs are called autosomes while 22 pairs are called autosomes while the last pair determines the sex of the last pair determines the sex of the individual; sex chromosomes (X the individual; sex chromosomes (X and Y)and Y)

Mapping of chromosomes is called a Mapping of chromosomes is called a karyotypekaryotype

What can cause abnormal cell division?What can cause abnormal cell division?

- radiation: UV light, x-ray- radiation: UV light, x-ray

- viruses- viruses

- organic chemicals: pesticide, - organic chemicals: pesticide, nicotinenicotine

Teratogens: substances that can cause Teratogens: substances that can cause severe congenital abnormalities.severe congenital abnormalities.

Carcinogens: chemical or environmental Carcinogens: chemical or environmental agent that produces canceragent that produces cancer

Cancer:Cancer:    - The - The p53 genep53 gene prevents these mutations prevents these mutations

from causing problems. from causing problems. - p53 is present in all DNA- p53 is present in all DNA- p53 is responsible for cell division to stop - p53 is responsible for cell division to stop so so that mutated DNA can be repaired.that mutated DNA can be repaired.- If DNA cannot be repaired the cell - If DNA cannot be repaired the cell undergoes undergoes apoptosisapoptosis in which the cell is in which the cell is programmed to die.programmed to die.- Defective or missing p53 can result in the - Defective or missing p53 can result in the cell cell mutating uncontrollably causing a mutating uncontrollably causing a tumor.tumor.- Normal cells will divide on average about - Normal cells will divide on average about 50 50 times then the cell dies. While tumors times then the cell dies. While tumors divide divide without stopping.without stopping.

Benign tumorsBenign tumors are cell masses that are cell masses that do not fragment or spread beyond its do not fragment or spread beyond its original area of growth.original area of growth.

        

Malignant tumorsMalignant tumors are cell masses are cell masses that break apart and spread or that break apart and spread or invade other parts of the body.  This invade other parts of the body.  This movement is movement is metastasismetastasis.                                         .                                                                 

CancerCancer is the term used to refer to is the term used to refer to any tumor that has the potential to any tumor that has the potential to become malignant.become malignant.

VI. VI. Protein Synthesis Protein Synthesis Ribonucleic acid (RNA) links DNA's genetic Ribonucleic acid (RNA) links DNA's genetic

instructions for making proteins to the process of instructions for making proteins to the process of protein synthesis protein synthesis

It copies or transcribes the message from DNA It copies or transcribes the message from DNA and then translates that message into a protein. and then translates that message into a protein.

RNA, like DNA, is a nucleic acid or polymer of RNA, like DNA, is a nucleic acid or polymer of nucleotides nucleotides

RNA structure differs from DNA in the following RNA structure differs from DNA in the following ways: ways: The five carbon sugar in RNA nucleotides is The five carbon sugar in RNA nucleotides is

ribose rather than deoxyribose ribose rather than deoxyribose The nitrogenous base uracil is found in place of The nitrogenous base uracil is found in place of

thymine thymine

PROTEIN SYNTHESISPROTEIN SYNTHESIS

The linear sequence of nucleotides in DNA ultimately The linear sequence of nucleotides in DNA ultimately determines the linear sequence of amino acids in a protein. determines the linear sequence of amino acids in a protein.

Nucleic acids are made of four types of nucleotides which Nucleic acids are made of four types of nucleotides which differ in their nitrogenous bases differ in their nitrogenous bases

Hundreds or thousands of nucleotides long, each gene has a Hundreds or thousands of nucleotides long, each gene has a specific linear sequence of the four possible bases. specific linear sequence of the four possible bases.

Proteins are made of twenty types of amino acids linked in a Proteins are made of twenty types of amino acids linked in a particular linear sequence (the protein's primary structure). particular linear sequence (the protein's primary structure).

Information flows from gene to protein through two major Information flows from gene to protein through two major processes, processes, transcriptiontranscription and and translationtranslation. .

Transcription - the synthesis of RNA - the synthesis of RNA using DNA as a template using DNA as a template A gene's unique nucleotide sequence is A gene's unique nucleotide sequence is

transcribed from DNA to a complimentary transcribed from DNA to a complimentary nucleotide sequence in messenger RNA nucleotide sequence in messenger RNA (mRNA). (mRNA).

The resulting mRNA caries this transcript The resulting mRNA caries this transcript of protein-building instructions to the cell's of protein-building instructions to the cell's protein-synthesizing machinery. protein-synthesizing machinery.

Translation - synthesis of a - synthesis of a polypeptide, which occurs under the polypeptide, which occurs under the direction of messenger RNA (mRNA) direction of messenger RNA (mRNA) During this process, the linear sequence of During this process, the linear sequence of

bases in mRNA is translated into the linear bases in mRNA is translated into the linear sequence of amino acids in a polypeptide. sequence of amino acids in a polypeptide.

Translation occurs on ribosomes, complex Translation occurs on ribosomes, complex particles composed of ribosomal RNA particles composed of ribosomal RNA (rRNA) and protein that facilitate the (rRNA) and protein that facilitate the orderly linking of amino acids into orderly linking of amino acids into polypeptide chains. polypeptide chains.

Signals are contained in the RNA to start Signals are contained in the RNA to start and stop translation.and stop translation.

SUMMARY OF PROTEIN SUMMARY OF PROTEIN SYNTHESISSYNTHESIS

GENETIC CODEGENETIC CODE

TranslationTranslation