Cell -Cell - Basic unit of all living Basic unit of all living thingsthings

Plasma membrane –Plasma membrane – Outer Outer boundary of the cellboundary of the cell Nucleus –Nucleus – Located centrally Located centrally Directs cell activitiesDirects cell activities Cytoplasm –Cytoplasm – Located between Located between

plasma membrane & nucleus plasma membrane & nucleus Contains cytosol and Contains cytosol and

organellesorganelles

• Outermost component of cellOutermost component of cell• Boundary that separates Boundary that separates

substances Intracellular substances Intracellular (inside the cell) vs. (inside the cell) vs. extracellular (outside the cell) extracellular (outside the cell) materialsmaterials

• Selective permeableSelective permeable• Allows some substances to Allows some substances to

cross it more easily than cross it more easily than othersothers

• Consists of lipids and proteinsConsists of lipids and proteins• Consists of 45-50% lipidsConsists of 45-50% lipids• 45-50% of protein45-50% of protein• 4-8% of carbohydrates4-8% of carbohydrates

• Predominate lipids are: Predominate lipids are: • Phospholipids and cholesterol Phospholipids and cholesterol • PhospholipidsPhospholipids:: lipid bilayer lipid bilayer• Polar heads facing water in the Polar heads facing water in the

interior and exterior of the cell interior and exterior of the cell (hydrophilic); nonpolar tails (hydrophilic); nonpolar tails facing each other on the interior facing each other on the interior of the membrane (hydrophobic)of the membrane (hydrophobic)

• CholesterolCholesterol:: Interspersed Interspersed among phospholipidsamong phospholipids

• Determines fluid nature of the Determines fluid nature of the membranemembrane

• Provides stabilityProvides stability

• Fluid-mosaic model:Fluid-mosaic model:

• Plasma membrane is neither Plasma membrane is neither rigid nor staticrigid nor static

• Highly flexibleHighly flexible• Fluid nature of membrane Fluid nature of membrane

provides provides – Distribution of molecules Distribution of molecules

within the membranewithin the membrane– Phospholipids automatically Phospholipids automatically

reassembled if membrane reassembled if membrane is damagedis damaged

Proteins Proteins are dispersed into the are dispersed into the phospholipid bilayer of phospholipid bilayer of

plasma membraneplasma membrane Integral or Intrinsic ProteinsIntegral or Intrinsic Proteins

– Embedded in the membrane Embedded in the membrane Peripheral or extrinsic ProteinsPeripheral or extrinsic Proteins

– Attached to either the inner or Attached to either the inner or outer surfaces of the lipid outer surfaces of the lipid bilayerbilayer

Membrane proteins function as:Membrane proteins function as: Markers, attachment sites, Markers, attachment sites, channels, receptors, enzymes, or channels, receptors, enzymes, or carrierscarriers

• Marker MoleculesMarker Molecules • Allow cells to identify one Allow cells to identify one

another or other molecules another or other molecules • Are mostly glycoproteinsAre mostly glycoproteins

and glycolipidsand glycolipids• eg. Ability of immune eg. Ability of immune

system to distinguish system to distinguish between self and foreign between self and foreign cells cells

• Organ transplantOrgan transplant

• Attachment ProteinsAttachment Proteins

• Integral proteins function Integral proteins function as attachment proteinas attachment protein

• Allow cell to attach to Allow cell to attach to other cellsother cells

• Or to extracellular Or to extracellular molecule &molecule & intracellular intracellular moleculesmolecules

• Also function as cellAlso function as cell

communicationcommunication

Transport ProteinsTransport ProteinsAre integral proteins, allow ions or molecules Are integral proteins, allow ions or molecules

to move from one side of plasma membrane to move from one side of plasma membrane to otherto other

Transport proteins are:Transport proteins are: Channel proteinsChannel proteins Carrier ProteinsCarrier Proteins ATP-powered pumps ATP-powered pumps

Channel ProteinsChannel Proteins Hydrophilic region of integral protein Hydrophilic region of integral protein

faces inwardfaces inward Ions or small molecules of rightIons or small molecules of right

size, charge and shape can pass size, charge and shape can pass through the channelthrough the channel

Charge in hydrophilic part of channel Charge in hydrophilic part of channel proteins determine proteins determine

molecules can passmolecules can pass eg. Flow of Heg. Flow of H+ + to inner mitochondrial to inner mitochondrial

membrane for ATP productionmembrane for ATP production

Carrier Proteins Carrier Proteins (transporters)(transporters)

Are Integral proteins move Are Integral proteins move ions from one side of ions from one side of membrane to the othermembrane to the other– Have specific binding sitesHave specific binding sites– Protein changes shape to Protein changes shape to

transport ions or moleculestransport ions or molecules– Resumes original shape after Resumes original shape after

transporttransport– eg. Transports sodium and eg. Transports sodium and

potassium ions across a nerve potassium ions across a nerve cell membranecell membrane

• ATP-Powered PumpsATP-Powered Pumps• Are transport proteins thatAre transport proteins that

move specific ions and move specific ions and molecules from one side of molecules from one side of plasma membrane to the plasma membrane to the other other

• Requires ATPRequires ATP

• Receptor ProteinsReceptor Proteins• Are Proteins or glycoproteins Are Proteins or glycoproteins

in membranes with an in membranes with an exposed receptor siteexposed receptor site

• Can attach to specific Can attach to specific chemical signal moleculeschemical signal molecules

• Chemical signal can attach Chemical signal can attach only to cells with that specific only to cells with that specific receptorreceptor

• Binding acts as a signal that Binding acts as a signal that triggers a response triggers a response

Receptors Linked to Channel Receptors Linked to Channel ProteinsProteins

Attachment of specific chemical signals Attachment of specific chemical signals (e.g., acetylcholine) to receptors causes (e.g., acetylcholine) to receptors causes change in shape of channel proteinchange in shape of channel protein

Causes channel opens or closesCauses channel opens or closes

Changes permeability of plasma Changes permeability of plasma membrane and some ions can pass membrane and some ions can pass through ion channelsthrough ion channels

• EnzymesEnzymes:: • Some membrane proteinsSome membrane proteins

functions as enzymesfunctions as enzymes• Catalyze reactions at Catalyze reactions at

outer/inner surface of outer/inner surface of plasma membraneplasma membrane

• Eg. Surface cells of small Eg. Surface cells of small intestine produce enzymes intestine produce enzymes that breaks dipeptide into that breaks dipeptide into amino acidsamino acids

• Diffusion/OsmosisDiffusion/Osmosis• water diffuses through the membranewater diffuses through the membrane• Lipid soluble substances go acrossLipid soluble substances go across

• FiltrationFiltration• Moves particles with pressure differenceMoves particles with pressure difference

• Passive Transport (= facilitated diffusion)Passive Transport (= facilitated diffusion)• No energy requiredNo energy required• selectively allow certain types of molecules in selectively allow certain types of molecules in

and out through channel proteinsand out through channel proteins• Active TransportActive Transport

• Required energy = ATPRequired energy = ATP• Endocytosis and ExocytosisEndocytosis and Exocytosis

• Large mol. enters to cell by endocytosisLarge mol. enters to cell by endocytosis• Large mol. leaves cell via exocytosisLarge mol. leaves cell via exocytosis

• DiffusionDiffusion: : – net movement of molecules net movement of molecules

down a concentration gradient down a concentration gradient towards areas of lower towards areas of lower concentrationconcentration

– Allows oxygen, carbon Allows oxygen, carbon dioxide, and lipids to crossdioxide, and lipids to cross

• Concentration GradientConcentration Gradient– Conc. Of ions/molecules on Conc. Of ions/molecules on

one side not same as otherone side not same as other

• Diffusion affected by different Diffusion affected by different conditionsconditions– Temperature:Temperature:

• High temp increases rate of High temp increases rate of diffusiondiffusion

– Size:Size:• Small molecules go down Small molecules go down

conc. gradient fasterconc. gradient faster– Electronic gradient:Electronic gradient:

• charges of molecules/ions charges of molecules/ions affect diffusion rateaffect diffusion rate

• Dropping a dye in a cup of waterDropping a dye in a cup of water– drop drop diffusesdiffuses to the areas of to the areas of

the cup w/out the dyethe cup w/out the dye– goes down the goes down the concentration concentration

gradientgradient– dye goes towards a uniform dye goes towards a uniform

mixture in watermixture in water

– In osmosis,In osmosis, water molecules diffuse across a water molecules diffuse across a selectively permeable membraneselectively permeable membrane• From an area of low solute concentrationFrom an area of low solute concentration• To an area of high solute concentrationTo an area of high solute concentration• Until the solution is equally concentrated on both sides Until the solution is equally concentrated on both sides

of the membraneof the membrane

• Osmotic concentrationOsmotic concentration– concentration of all molecules dissolved in a solutionconcentration of all molecules dissolved in a solution

• Hypertonic solutionHypertonic solution– solution with higher concentration of solutessolution with higher concentration of solutes

• Hypotonic solutionHypotonic solution– Solution with lower conc. of solutesSolution with lower conc. of solutes

• Isotonic solutionsIsotonic solutions– solutions with equal conc.solutions with equal conc. of soluteof solute

The survival of a cell depends on its ability to balance The survival of a cell depends on its ability to balance water uptake and losswater uptake and loss– IsotonicIsotonic:: cell neither shrinks nor swells cell neither shrinks nor swells– HypertonicHypertonic:: cell shrinks (crenation) cell shrinks (crenation)– HypotonicHypotonic:: cell swells (lysis) cell swells (lysis)

• Works like a sieveWorks like a sieve• Depends on pressure difference on either Depends on pressure difference on either

side of a partitionside of a partition• Moves from side of greater pressure to Moves from side of greater pressure to

lowerlower• Eg: Eg: urine formation in the kidneysurine formation in the kidneys Blood Blood

pressure moves water and small molecules pressure moves water and small molecules from the blood through the filtration from the blood through the filtration membrane while large molecules remain in membrane while large molecules remain in the bloodthe blood

• Like diffusion, but uses Like diffusion, but uses carrier or channel proteincarrier or channel protein

• Selective PermeabilitySelective Permeability– Cell controls what comes in Cell controls what comes in

and goes outand goes out

• Certain channel or carrier Certain channel or carrier proteinsproteins– allow only certain molecule allow only certain molecule

types entrytypes entry

• Molecules/ions goMolecules/ions go with with concentration gradientconcentration gradient

• No energy requiredNo energy required

– Active transport requires energy to move solutes Active transport requires energy to move solutes against a concentration gradientagainst a concentration gradient

• ATP supplies the energyATP supplies the energy• Transport proteins move solute molecules across the Transport proteins move solute molecules across the

membranemembrane• Eg. Glucose, amino acids Eg. Glucose, amino acids

• Macromolecules transported into or out of the Macromolecules transported into or out of the cell through plasma membrane by vesicle cell through plasma membrane by vesicle formationformation– Endocytosis –Endocytosis – Cells engulf substances and plasma Cells engulf substances and plasma

membrane extends outward and surround food membrane extends outward and surround food particle and pinches off and forms the vesicleparticle and pinches off and forms the vesicle

• PhagocytosisPhagocytosis– Vesicle contains large Vesicle contains large

solid particlessolid particles• PinocytosisPinocytosis

– Vesicle contains liquidVesicle contains liquid

or small particleor small particle• Receptor-MediatedReceptor-Mediated

– Plasma membrane Plasma membrane contain specific contain specific receptor that allows receptor that allows certain substances to certain substances to be transported by be transported by phagocytosis or phagocytosis or pinocytosispinocytosis

• A vesicle may fuse with the membrane and expel its contents A vesicle may fuse with the membrane and expel its contents outside the cell outside the cell

• ExamplesExamples– Secretion of digestive enzymes by pancreasSecretion of digestive enzymes by pancreas– Secretion of mucous by salivary glandsSecretion of mucous by salivary glands– Secretion of milk by mammary glandsSecretion of milk by mammary glands

• Cytoplasm:Cytoplasm: Cellular Cellular material outside nucleus material outside nucleus but inside plasma but inside plasma membranemembrane

• Composed of Cytosol, Composed of Cytosol, Cytoskeleton, Cytoplasmic Cytoskeleton, Cytoplasmic Inclusions, OrganellesInclusions, Organelles

• CytosolCytosol:: fluid portion fluid portion • Dissolved molecules (ions Dissolved molecules (ions

in water) and colloid in water) and colloid (proteins in water)(proteins in water)

• Is a network of fibers Is a network of fibers extending throughout the extending throughout the cytoplasmcytoplasm

• Gives mechanical support to Gives mechanical support to the cell the cell

• Maintain cell shapeMaintain cell shape• Assists in cell movementAssists in cell movement• Consists of three types of Consists of three types of

protein fibers: protein fibers: • MicrotubulesMicrotubules• Actin or MicrofilamentsActin or Microfilaments• Intermediate filamentsIntermediate filaments

MicrotubulesMicrotubules Found in cytoplasmFound in cytoplasm Hollow rods – 25 nm in diameter, Hollow rods – 25 nm in diameter,

0.25 0.25 m – 25 m – 25 m in lengthm in length made up of protein – made up of protein – tubulintubulin Shape and support the cellShape and support the cell Guide movement of organellesGuide movement of organelles Responsible for separation of Responsible for separation of

chromosomes during cell divisionchromosomes during cell division Essential components of Essential components of

centrioles, spindle fibers, cilia and centrioles, spindle fibers, cilia and flagellaflagella

Actin filaments or MicrofilamentsActin filaments or Microfilaments Solid rods – 7 nm in diameterSolid rods – 7 nm in diameter Twisted double chain of actin – Twisted double chain of actin –

globular proteinglobular protein Mechanical support for microvilliMechanical support for microvilli

in intestinal cellsin intestinal cells Enable cells to change shape Enable cells to change shape

and moveand move Eg. Muscle cells, actin filaments Eg. Muscle cells, actin filaments

are responsible for muscle`s are responsible for muscle`s contractioncontraction

Intermediate filamentsIntermediate filamentsfibrous proteinsfibrous proteins supercoiled into supercoiled into

thicker cablethicker cable10 nm in diameter10 nm in diameter larger than microfilaments but larger than microfilaments but

smaller than microtubulessmaller than microtubulesSupport cell shapeSupport cell shapeProvide mechanical strength Provide mechanical strength

to cellsto cellseg. Support the extensions of eg. Support the extensions of

nerve cellsnerve cells

• Are aggregates of chemicals either producedAre aggregates of chemicals either produced or taken in by cellsor taken in by cells

• For eg. Lipid droplets store energy-rich For eg. Lipid droplets store energy-rich moleculesmolecules

• hemoglobin in red blood cells transport oxygenhemoglobin in red blood cells transport oxygen

• melanin – skin color pigmentmelanin – skin color pigment

• Minerals, dye etc.- cytoplasmMinerals, dye etc.- cytoplasm

• Small specialized structures Small specialized structures with particular functionswith particular functions

• Most have membranes that Most have membranes that separate interior of separate interior of organelles from cytoplasmorganelles from cytoplasm

• Each organelle is Each organelle is responsible for performing responsible for performing specific functionspecific function

• Nucleus is the largest Nucleus is the largest organelle of the cellorganelle of the cell

• The nucleus is the cell's genetic control centerThe nucleus is the cell's genetic control center• Contains the cell's DNAContains the cell's DNA

• Forms long fibers of chromatin that make Forms long fibers of chromatin that make up up chromosomeschromosomes

• Human body cell has Human body cell has 46 chromosomes46 chromosomes• Nucleus is large, membrane-bound structureNucleus is large, membrane-bound structure• Consists of Consists of nucleoplasmnucleoplasm and and

surrounded by double membrane surrounded by double membrane

nuclear envelopenuclear envelope• Pores in the envelope control Pores in the envelope control

flow of materials in and outflow of materials in and out• Nucleus contains ball-likeNucleus contains ball-like

structure – structure – nucleolusnucleolus• Ribosomes Ribosomes are synthesized in the nucleolusare synthesized in the nucleolus

• Chromosome Structure:Chromosome Structure:• Consist of chromatin, a complexConsist of chromatin, a complex of DNA and histone proteinsof DNA and histone proteins

• Before cell division, chromosomeBefore cell division, chromosome duplication takes placeduplication takes place

• Each chromosome consists of Each chromosome consists of two chromatidstwo chromatids

• Chromatids are Chromatids are joined togetherjoined together at the at the centromerecentromere

•Chromosome Structure:Chromosome Structure:

• When the cell divides, the sister When the cell divides, the sister chromatids separate from each chromatids separate from each otherother

• Cell divides into Cell divides into two daughter two daughter cellscells

• Each with a complete and Each with a complete and identical set of chromosomesidentical set of chromosomes

– DNA Controls cellular DNA Controls cellular activities by directing activities by directing protein protein synthesissynthesis

– Protein regulate most Protein regulate most chemical reactionschemical reactions

– DNA transfers its coded DNA transfers its coded information to RNAinformation to RNA• RNA carries the RNA carries the

information from nucleus information from nucleus to cytoplasm to make to cytoplasm to make proteinsproteins

– Sites for protein synthesisSites for protein synthesis– Assembled in nucleolus of Assembled in nucleolus of

nucleusnucleus– Then move through nuclear Then move through nuclear

pores into the cytoplasmpores into the cytoplasm– Composed of a large and a Composed of a large and a

small subunitsmall subunit– Consists of ribosomalConsists of ribosomal

RNA (rRNA) & proteinRNA (rRNA) & protein– Some ribosomes are Some ribosomes are

suspended in cytosol, other suspended in cytosol, other are attached to ERare attached to ER

– The endoplasmic The endoplasmic reticulum (ER)reticulum (ER)

• Main manufacturing Main manufacturing facilities within the cellfacilities within the cell

• A continuous network of A continuous network of flattened sacs and tubesflattened sacs and tubes

in the cytoplasm in the cytoplasm • Internal spaces of sacsInternal spaces of sacs

and tubes - and tubes - CisternaeCisternae• ER is composed of ER is composed of • Rough ERRough ER• Smooth ERSmooth ER

– Rough endoplasmic reticulum (rough ER) is studded Rough endoplasmic reticulum (rough ER) is studded with ribosomes with ribosomes • Are place where proteins are produced and modifiedAre place where proteins are produced and modified

– Transported to other organellesTransported to other organelles

– Smooth endoplasmic reticulum (smooth ER) Smooth endoplasmic reticulum (smooth ER) lacks attached ribosomeslacks attached ribosomes

– Has variety of functionsHas variety of functions• Synthesizes lipids, including fatty acids, phospholipids Synthesizes lipids, including fatty acids, phospholipids

and steroids and steroids • Detoxify toxins and drugs inDetoxify toxins and drugs in

liver cellsliver cells• Stores calcium ions that Stores calcium ions that

function in muscle function in muscle

contractioncontraction

• The Golgi apparatus consists of The Golgi apparatus consists of stacks of flattened membranous stacks of flattened membranous sacs sacs

• Packaging and distribution Packaging and distribution centercenter

• Receives, modifies, Receives, modifies, packages and distributes packages and distributes proteins & lipids proteins & lipids manufactured by ERmanufactured by ER

• Ships modified products to Ships modified products to other organelles or the cell other organelles or the cell surface via secretorysurface via secretory

vesiclesvesicles

– A lysosome is a membrane-A lysosome is a membrane-enclosed sac form from Golgi enclosed sac form from Golgi apparatusapparatus

• It contains digestive enzymesIt contains digestive enzymes• The enzymes break down The enzymes break down

macromoleculesmacromolecules• Lysosomes have several Lysosomes have several

types of digestive functionstypes of digestive functions• They fuse with food vacuoles They fuse with food vacuoles

to digest the foodto digest the food• Destroy bacteria that have Destroy bacteria that have

been ingested into white been ingested into white blood cellsblood cells

• Recycle damaged organellesRecycle damaged organelles

• Abnormal lysosomes can cause fatal diseasesAbnormal lysosomes can cause fatal diseases– Lysosomal storage diseases Lysosomal storage diseases

• Result from an inherited lack of one or more digestive Result from an inherited lack of one or more digestive enzymes found in lysozymesenzymes found in lysozymes

• Seriously interfere with various cellular functionsSeriously interfere with various cellular functions• eg. eg. Pompe`s diseasePompe`s disease – lack of – lack of glycogenglycogen-digesting -digesting

enzymeenzyme• Cause weakening of heart muscleCause weakening of heart muscle• Tay-Sachs diseaseTay-Sachs disease – lack of – lack of lipidlipid –digesting enzyme –digesting enzyme• Accumulation of excess lipid damage brainAccumulation of excess lipid damage brain

• PeroxisomesPeroxisomes– Smaller than lysosomesSmaller than lysosomes– Contains two sets of enzymesContains two sets of enzymes– One enzyme break down fatty One enzyme break down fatty

acids and amino acidsacids and amino acids– Hydrogen peroxide is a by-Hydrogen peroxide is a by-

product of breakdown (toxic)product of breakdown (toxic)– Another enzyme Another enzyme Catalase Catalase

convert hydrogen peroxide intoconvert hydrogen peroxide into

water and oxygenwater and oxygen– More peroxisomes – kidney and More peroxisomes – kidney and

liver for detoxificationliver for detoxification

• ProteasomesProteasomes– Tunnel-like structureTunnel-like structure– not surrounded by membrane not surrounded by membrane – Consist of large protein complexesConsist of large protein complexes– Found in nucleus and cytoplasmFound in nucleus and cytoplasm– Include several enzymes that break down and recycle Include several enzymes that break down and recycle

unneeded or damaged proteins in cellunneeded or damaged proteins in cell

• Major site of ATP synthesisMajor site of ATP synthesis• Consists of two membranesConsists of two membranes• Outer membrane – smoothOuter membrane – smooth• Inner membraneInner membrane

– CristaeCristae:: Infoldings of inner Infoldings of inner membranemembrane

– MatrixMatrix:: Enzymes located in space Enzymes located in space formed by inner membraneformed by inner membrane

• Mitochondria increase in number when Mitochondria increase in number when cell energy requirements increase. cell energy requirements increase.

• Mitochondria contain DNA that codes Mitochondria contain DNA that codes for some of the proteins needed for for some of the proteins needed for mitochondria production.mitochondria production.

• Located in Located in CentrosomeCentrosome:: specialized specialized zone near nucleuszone near nucleus

• Center of microtubule formationCenter of microtubule formation• Contains pair of centrioleContains pair of centriole• Each with nine triplets of Each with nine triplets of

microtubule – ringmicrotubule – ring• Before cell division – CentrioleBefore cell division – Centriole

replicatereplicate• During cell division, centrioles divide, During cell division, centrioles divide,

move to ends of cell and organize move to ends of cell and organize spindle fibersspindle fibers

• Facilitate the movement of Facilitate the movement of chromosomes during cell divisionchromosomes during cell division

• Appendages projecting from Appendages projecting from cell surfacescell surfaces

• Capable of movementCapable of movement• Cilia Cilia move in a coordinated move in a coordinated

back-and-forth motion back-and-forth motion • Occur in large no. on cell Occur in large no. on cell

surfacesurface• Cylindrical in shapeCylindrical in shape• 0.25 0.25 m in diameter, 10 m in diameter, 10 m in m in

lengthlength• Moves materials over the cell Moves materials over the cell

surfacesurface• eg. Respiratory tract – eg. Respiratory tract –

removes mucusremoves mucus

• Similar to cilia but longer (45 Similar to cilia but longer (45 m)m)• Usually only one per cellUsually only one per cell• Move the cell itself in wave-like fashionMove the cell itself in wave-like fashion• Eg: sperm cellEg: sperm cell

1 µm

Direction of swimming

Motion of flagella

– The structure and The structure and mechanism of cilia and mechanism of cilia and flagella are similarflagella are similar

• Ring of 9 microtubule Ring of 9 microtubule doublets surrounds a doublets surrounds a central pair of microtubulecentral pair of microtubule

– 9 + 2 arrangement9 + 2 arrangement– Extend into basal Extend into basal

bodiesbodies

– Using energy from ATP, movement of dynein Using energy from ATP, movement of dynein

arms ( motor proteins) produces microtubulearms ( motor proteins) produces microtubule

bendingbending

• Extension of plasma membraneExtension of plasma membrane• Normally many microvilli on each cellNormally many microvilli on each cell• One tenth to one twentieth size of ciliaOne tenth to one twentieth size of cilia• Do not move, supported by actin filamentsDo not move, supported by actin filaments• Increase the cell surface areaIncrease the cell surface area• Found in kidney, intestine Found in kidney, intestine • Main function is absorptionMain function is absorption