Physiology of Cells Chapter 4. Cell Cycle The events that occur during the life cycle of a cell. 3 stages: The events that occur during the life cycle.

Physiology of Physiology of CellsCells

Chapter 4Chapter 4

Cell CycleCell Cycle

The events that occur The events that occur during the life cycle during the life cycle of a cell. 3 stages:of a cell. 3 stages:–InterphaseInterphase–MitosisMitosis–cytokinesiscytokinesis

InterphaseInterphase Period of time from cell Period of time from cell

formation to cell divisionformation to cell division–G1G1 – active cell metabolism – active cell metabolism–SS – DNA replication – DNA replication–G2G2 – enzymes and proteins – enzymes and proteins needed for division are needed for division are produced; organelles are produced; organelles are duplicatedduplicated

MitosisMitosis ProphaseProphase – –

– chromatin shortens, chromatin shortens, thickens, becomes visible as thickens, becomes visible as chromosomeschromosomes

– nuclear membrane nuclear membrane disappearsdisappears

– centrioles and spindle fibers centrioles and spindle fibers appearappear

MetaphaseMetaphase – ––chromosomes line up chromosomes line up along equator of the along equator of the cellcell

–attach to spindle attach to spindle fibers fibers

AnaphaseAnaphase – – –spindle fibers contractspindle fibers contract–pull the chromatids of pull the chromatids of the chromosomes the chromosomes apart.apart.

TelophaseTelophase – – –spindle fibers and spindle fibers and centrioles disappearcentrioles disappear

–chromosomes continue chromosomes continue to move to opposite to move to opposite polespoles

CytokinesisCytokinesis

Chromosomes lengthen Chromosomes lengthen and become chromatin and become chromatin againagain

nuclear membrane nuclear membrane reformsreforms

Cytoplasm dividesCytoplasm divides

Interphase

Signals For Cell Signals For Cell DivisionDivision Surface to volume ratioSurface to volume ratio Frequency of division is Frequency of division is

dependent of the type of dependent of the type of cellcell

Availability of spaceAvailability of space Release of inhibitory or Release of inhibitory or

stimulatory chemicals by stimulatory chemicals by surrounding cellssurrounding cells

Plasma MembranePlasma Membrane Flexible, Flexible,

selectively selectively permeablepermeable

composed composed chiefly of chiefly of phospho-phospho-lipid and lipid and protein protein bilayerbilayer

Phospholipids Phospholipids –impermeable to water impermeable to water soluble materialssoluble materials

–Polar, phosphorus Polar, phosphorus containing heads containing heads (hydrophilic) are exposed to (hydrophilic) are exposed to water both inside and water both inside and outside the cell (2 layers)outside the cell (2 layers)

–Nonpolar tails (hydrophobic) Nonpolar tails (hydrophobic) are sandwiched between 2-are sandwiched between 2-layered heads layered heads

Passive Processes Passive Processes – requires no – requires no energyenergySimple diffusionSimple diffusion

– movement of lipid soluble movement of lipid soluble materials across the materials across the plasma membraneplasma membrane

– molecules move down a molecules move down a “concentration gradient” “concentration gradient” using kinetic energy as the using kinetic energy as the driving force.driving force.

DialysisDialysis –Process in which solutes of Process in which solutes of differing sizes are differing sizes are separated from each other separated from each other as they may (or may not) as they may (or may not) diffuse across a selectively diffuse across a selectively permeablepermeable membrane membrane

OsmosisOsmosis –diffusion of water diffusion of water through the plasma through the plasma membranemembrane

–occurs when there is a occurs when there is a difference in water difference in water concentration on either concentration on either side of the membrane. side of the membrane.

Net movement (unequal) of Net movement (unequal) of water occurs until a water occurs until a balance is reached between balance is reached between the the hydrostatic pressurehydrostatic pressure (pressure of water inside (pressure of water inside the cell trying to push out) the cell trying to push out) is equal to the is equal to the osmotic osmotic pressurepressure (tendency of a cell (tendency of a cell to pull water in). to pull water in).

Hydrostatic Pressure

Osmotic Pressure

The net movement is The net movement is determined by the determined by the “tonicity”“tonicity” (concentration of (concentration of solutes) of the solutes) of the solutionsolution

–Hypertonic solutionsHypertonic solutions – – solutions that contain solutions that contain greater amounts of greater amounts of solutes than solutes than comparable solutions. comparable solutions. If a cell is placed in a If a cell is placed in a hypertonic solution…hypertonic solution…

–Hypotonic solutionsHypotonic solutions-- solutions that contain solutions that contain smaller amounts of smaller amounts of solutes than solutes than comparable solutions. comparable solutions. If a cell is placed in a If a cell is placed in a hypotonic solution…hypotonic solution…

–Isotonic solutionsIsotonic solutions – – solutions that contain solutions that contain equal amounts of equal amounts of solutes with solutes with comparable solutions. comparable solutions. If a cell is placed in an If a cell is placed in an isotonic solution…isotonic solution…

A cell containing 75% water and A cell containing 75% water and 25% solutes is placed in a 25% solutes is placed in a solution of 100% water. What solution of 100% water. What will the cell do?will the cell do?

A.A. ShrivelShrivel

B.B. SwellSwell

C.C. NothingNothing

D.D. Step out for a cup of Step out for a cup of Starbuck’s coffeeStarbuck’s coffee

A cell containing 75% water and A cell containing 75% water and 25% solutes is placed in a 25% solutes is placed in a solution of 100% water. What solution of 100% water. What type of solution is the cell in?type of solution is the cell in?

A.A. HypotonicHypotonic

B.B. HypertonicHypertonic

C.C. IsotonicIsotonic

D.D. Cannot tell for the Cannot tell for the information giveninformation given

A A cell containing 75% water and cell containing 75% water and 25% solutes is placed in a solution 25% solutes is placed in a solution of 65% water and 35% solutes. of 65% water and 35% solutes. What type of solution is the cell What type of solution is the cell in?in?

A.A. HypotonicHypotonic

B.B. HypertonicHypertonic

C.C. IsotonicIsotonic

D.D. Cannot tell from the Cannot tell from the information given.information given.

A A cell containing 75% water and cell containing 75% water and 25% solutes is placed in a 25% solutes is placed in a solution of 65% water and 35% solution of 65% water and 35% solutes. What will happen to the solutes. What will happen to the cell?cell?

A.A. SwellSwell

B.B. ShrivelShrivel

C.C. NothingNothing

D.D. Go to the Klein Go to the Klein Collins/Tomball football Collins/Tomball football game.game.

Facilitated diffFacilitated diffusionusion– lipid insoluble lipid insoluble

substances substances (usually (usually glucose): glucose): ““hitch a ride” hitch a ride” with a lipid with a lipid soluble carrier soluble carrier moleculemolecule

OROR Travel through a channel protein Travel through a channel protein

– process is highly selective, but process is highly selective, but requires no cell energy.requires no cell energy.

Small molecules forced out of tissues Small molecules forced out of tissues due to hydrostatic pressuredue to hydrostatic pressure

Ex. Fluids, but not larger particles, Ex. Fluids, but not larger particles, leave the capillaries and enter leave the capillaries and enter tissuestissues

FiltrationFiltration

Active Processes – Active Processes – Requires cell energy in Requires cell energy in the form of ATPthe form of ATP

Active transportActive transport – (ex: – (ex: solute pump) the solute pump) the movement of ions and/or movement of ions and/or amino acids “uphill” amino acids “uphill” against the against the concentration gradientconcentration gradient

CotransportCotransport – – insoluble or large insoluble or large molecule is allowed molecule is allowed through a protein pore through a protein pore only when another only when another entering molecule entering molecule causes a change in the causes a change in the shape of the protein shape of the protein pore. pore.

(hint: think about (hint: think about entering a gated entering a gated apartment complex in apartment complex in your car by driving in your car by driving in behind someone who behind someone who knows the code to the knows the code to the gate… same idea…)gate… same idea…)

Bulk transportBulk transport –ExocytosisExocytosis – movement of – movement of macromolecules out of the macromolecules out of the cell (hormones, cell (hormones, neurotransmitters, mucus, neurotransmitters, mucus, wastes); this is wastes); this is accomplished by fusing a accomplished by fusing a sac, containing the sac, containing the material, with the plasma material, with the plasma membrane.membrane.

EndocytosisEndocytosis – movement of movement of

macromolecules into macromolecules into the cellthe cell

PhagocytosPhagocytosisis – solids – solids

PinocytosisPinocytosis – liquids– liquids

Receptor mediatedReceptor mediated – – (ex: cholesterol)(ex: cholesterol)–taken into the liver by first taken into the liver by first binding to a cholesterol binding to a cholesterol receptor on the surface of receptor on the surface of liver cellsliver cells

–““hypercholesterolemia”hypercholesterolemia” results when there is a results when there is a lack of these lack of these receptorsreceptors

DisordersDisordersCell TransportCell Transport

–Cystic FibrosisCystic Fibrosis; Cl; Cl-- ion ion pumps in cell pumps in cell membranes are missingmembranes are missing

–Duschene’s Muscular Duschene’s Muscular DystrophyDystrophy – leaky Ca – leaky Ca++ channelschannels

Cell Membrane Cell Membrane ReceptorsReceptors –Type 2 DiabetesType 2 Diabetes – – obesity triggers a obesity triggers a reduction in the number reduction in the number of insulin receptors on of insulin receptors on cell surfacecell surface

Cell ReproductionCell Reproduction

–CancersCancers

DNA and Protein SynthesisDNA and Protein Synthesis– MutationsMutations– Sickle cell anemiaSickle cell anemia – produces – produces abnormal hemoglobin from abnormal hemoglobin from an error in DNA strandan error in DNA strand

– Inborn metabolic disorders Inborn metabolic disorders - - due to improper protein due to improper protein synthesis ex: PKU, albinism, synthesis ex: PKU, albinism, etc.etc.

Review of transport of small substancesReview of transport of small substances

nonpolar

passive

dialysis

polar/ionic

facilitated diffusion

active transport

active

water

osmosis

passive

hypotonic

hypertonic