2 Generalized View of the Cell There are three main parts to a cell and each part has a very specific function.Read pages to discover them on your own….
3 The Plasma Membrane Sturdy barrier; made mainly of proteins and lipids Lipid bilayer made of three types of lipid molecules: Phospholipids (lipids that contain phosphorus), cholesterol , glycoproteins (lipids that contain carbohydrates)Two types of proteins:Intergral protein extend through(2) Peripheral loosely attached to interior/exteriorexample: glycoproteins –proteins attached to carbohydratesSelectively permeable--controls what in/out;to water, most nonpolar lipid soluble molecules: fatty acids, fat-soluble vitamins, steroids, oxygen, carbon dioxideImpermeable to: ions (cross through ion channels), charged or polar molecules: glucose, amino acids (these cross through integral protein assist, channels; transporters change shape from one side to other)Receptors (integral proteins) recognize & bind to specific molecules; i.e. hormonesEnzymes (integral and peripheral proteins)Membrane glycoproteins and glycolipids = cell identity markers id same cell tissue or foreign cells (danger)
4 Transport Across the Plasma Membrane Fluids in average body = ~60%ICF -- inside the cell (cytosol)ECF – outside the cellInterstitial fluid (between cells of tissues)Plasma (blood vessels)Lymph (lymphatic vessels)Cerebrospinal fluid (within and around brain/spinal cord)Materials dissolve into these body fluids; direction of movement dependent upon concentration (amount of solute in solution)
5 Concentration Gradients Differences between ICF and ECF in solute concentration3% salt solution % salt solution??? Water ??? WaterPassive ActiveHigh to low Low to highNo energy needed Energy neededWould this be passive or active
6 Concentration Gradients Differences between ICF and ECF in solute concentration3% salt solution % salt solution97% Water % WaterPassiveHigh to low until dynamic equilibrium reachedDown concentration gradientNo energy needed
7 Passive Processes Does not require the use of energy Diffusion defined:Substance moves due to kinetic energyMovement from high concentration to low concentrationMovement of more molecules in one direction is called net diffusionMovement ‘down the concentration gradient’Continues until equilibrium is reached
8 Two types of diffusionSimple diffusion: lipid-soluble substances, simple cross membrane down the gradientFacilitated diffusion: ions, through pores of ion channels of integral proteinsNO ENERGY NEEDEDSimple: oxygen, carbon dioxide, nitrogen gases; fatty acids, steroids, fat-soluble vitamins (A, D, E, and K), glycerol, small alcohol and ammonia, water, (polar) and urea (polar)SIMPLE DIFFUSION ALLOWS GAS EXCHANGES BETWEEN BODY AND BLOOD CELLS AND BLOOD AND AIR WITHIN THE LUNGSALLOWS WASTE TO LEAVE THE BODYFacilitated through pores: ions of potassium, chloride, sodium, calcium through gatedFacilitated: through integral protein assist; substance binds to specific transporter, transporter changes shape, release substance on other side (hormone directed process)glucose, fructose, galactose, urea, and some vitamins
9 OsmosisNet movement of water down the gradient; lower solute concentration to higher solute concentration throughLipid bilayerIntegral proteinsBook problem and packet, sac permeable to water not sucrose; filled with solution is 20% sucrose & 80% water placed in 100% waterMine one side 20 sucrose 80 water, mine moves from high water concentration to low, levels go up because water moves in but sucrose cannot move out, pressure forces some water back out thus maintaining equilibrium, movement equal back and forthDo practice problem in packetWILL LEVELS CONTINUE TO GO UP UNTIL =???? YES!!!! YOUR LEVELS CONTINUE TO GO UP UNTIL EQUILIBRIM IS REACHED20% sucrose80% water
10 Osmotic PressurePressure exerted on plasma membrane due to a solution containing solute particles that cannot pass through membraneHigher solute concentration = higher osmotic pressureLower solute concentration = lower osmotic pressure
11 Osmotic SolutionsIsotonic solution: cells maintain normal shape and volume; concentration of solutes equal on both sides of membraneHypotonic solution: higher concentration of water outside; higher concentration of solutes than cytosol inside cellWater molecules will enter cell faster than they leave it = cell will swell, eventually burstBursting of red blood cells referred to as hemolysisHypertonic solution: higher concentration of water inside; lower concentration of solutes than cytosol inside cellWater molecules will leave cell faster than they enter it = cell will shrinkShrinkage of red blood cells referred to as crenation
13 Passive or Active?Have I been talking about passive, active, or passive and active transport?
14 Active TransportFrom low to high concentration; ‘up the concentration gradient’Requires the use of energyComes from splitting of ATP moleculeChanges shape of transporter protein, called a pumpTransports ions: Na+, K+, H+, Ca+2, I-, Cl-Example: sodium-potassium pump40% of a cell’s ATP expended on active transportDrugs like cyanide can turn off ATP production--FATALSodium-potassium pump expels sodium (3) from cell and brings in potassium (2) and acts as an enzyme to split ATPAlso extremely important because it maintains osmotic balance of fluids out v. inside the cell by constantly regulating sodium and potassium that easily leaks into and out of a cell; osmotic balance is needed for the ability of cells to generate electrical signals for action potentials
15 CyanideCyanide can be a colorless gas, such as hydrogen cyanide (HCN) or cyanogen chloride (CNCl), or a crystal form such as sodium cyanide (NaCN) or potassium cyanide (KCN).Cyanide sometimes is described as having a “bitter almond” smell, but it does not always give off an odor, and not everyone can detect this odor.You could be exposed to cyanide by breathing air, drinking water, eating food, or touching soil that contains cyanide.Cyanide enters water, soil, or air as a result of both natural processes and industrial activities. When present in air, it is usually in the form of gaseous hydrogen cyanide.Smoking cigarettes is probably one of the major sources of cyanide exposure for people who do not work in cyanide-related industries.
16 Transport in VesiclesVesicles small sacs formed by budding off of membranesTransport substances within the cell from one structure to anotherEnergy source again is ATPTake in substances from ECF and transport substances out to ECFEndocytosis: materials moved into cellPhagocytosis ‘to eat’ - solidsBulk-phase endocytosis(pinocytosis) liquidsExocytosis: materials moved out of cell
17 EndocytosisEndocytosis: capturing substance or particle from outside the cell by engulfing it within membrane folds from the cell membrane and releasing it into cytosol.There are two main kinds of endocytosis:PhagocytosisBulk-phase endocytosis (pinocytosis)
18 Phagocytosis Phagocytosis ”cellular eating” Occurs only in phagocytes Particles bind to plasma membrane receptorsProjections called pseudopods extend surround particles and portions of the membrane fuse to form a vesicleExtensions of the plasma membrane and cytoplasmPseudopods vesicle formed called a phagosomePhagosome enters the cell, fuses with lysosomesLysosome enzymes break down phagosome’s contentsAny undigested content remains in the phagosome, now called a residual bodyOccurs only in phagocytes(certain white blood cellsand macrophages), cellsspecialized to engulf anddestroy bacteria, viruses,aged dying cells, and foreignmatters protecting body fromdisease
19 Bulk-phase endocytosis (pinocytosis) Bulk-phase endocytosis (pinocytosis) ”cellular drinking”Plasma membrane folds inward, forming a vesicle allowing tiny droplets of extracellular fluid that contain dissolved substances to be surroundedVesicle detaches or “pinches off” of the plasma membrane and enters the cytosolLiquid is encircled within a pinocytic vesicleVesicle fuses with a lysosome, enzymes degrade engulfed solutesDegraded solutes; like amino acids and fatty acids leave the lysosome to be used elsewhere in the cell
20 ExocytosisExocytosis: process of vesicles fusing with the plasma membrane and secretes their contents to the outside of the cell.All cells do exocytosis process, but most important in:Secretory cellsRelease digestive enzymes, hormones, mucus, and other secretionsNerve cellsRelease neurotransmitters
21 CytoplasmConsists of all the cellular contents between the plasma membrane and the nucleus and includes both cytosol and organelles.
22 CytosolCytosol is the liquid portion of the cytoplasm that surrounds the organelles and makes up about 55% of the cell’s volume.75%-90% of cytosol is water, the rest is composed of dissolved solutes and suspended particles.Examples: ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste.Site of many chemical reactionsMaintain cell structure and enable cell growth
23 Cytoskeleton Extends throughout cytosol Network of three different types of protein filaments:MicrofilamentsIntermediate filamentsMicrotubules
24 Microfilaments Contribute to cell strength and shape Function: Provide mechanical support and help generate movementAnchor cytoskeleton to integral proteinsProvide support for microvilliMicrovilliFingerlike projections of the plasma membraneIncrease cell surface areaFound mostly in areas with great absorption needs like the small intestinesHelp cells attach to one another or extracellular materialsInvolved in muscle contractions, cell division, and cell locomotionMigration of embryonic cellsInvasion of tissues by white blood cells (WBCs) to fight diseaseMigration of skin cells in wound healing
25 Intermediate Filaments & Microtubules Found in parts of cells subjected to tension (stretching)Hold organelles in placeAttach cells to one anotherMicrotubulesLong, hollow tubesHelp determine cell shapeFunction as transport system forOrganelle movementSecretory vesiclesMigration of chromosomesCreate movement of cilia and flagella
26 OrganellesFunctions and identification of the organelles are your responsibility since this a total biology review areaInformation found on pages of your textbookAssign for homework, then do lysosomes, peroxisomes, and proteasomes slides and assign functions of the rest for homework…
27 Lysosomes Membrane-enclosed vesicles May contain up to 60 different digestive enzymesFuse with other vesicles during endocytosisRecycle the cell’s own structures (worn-out organelles) autophagyMay destroy own cell autolysisThis cause tissue deterioration after deathFaulty lysosomes can contribute to certain diseases, i.e. Tay-Sachs diseasePage 13 of packet…. Tay-sachs children jewish nerve cells accumulate glycolipid ganglioside causes muscle rigidity leads to blindness, dementia, lose of coordination die by age 5
28 Peroxisomes Smaller than lysosomes Contain enzymes called oxidases that oxide (remove hydrogen atoms from) various substancesCreating a by-product of hydrogen peroxide H2O2Potentially toxic compound associated with free radical superoxidesBUT peroxisomes also contain catalase which breaks down H2O2Oxidize toxic substancesAbundant in liver
29 Proteasomes Tiny, barrel-like structure Destroys unneeded, damaged, or faulty proteins from the cytosolContain enzyme called proteaseCuts proteins into small peptidesSo other enzymes can break them down to amino acids from which new proteins can be builtRemind them to do rest on their own…
30 Nucleus On your own, this is also a biology review topic Label the diagram on page 14 of your packetList the functions of the nucleus alsoInformation found on page 62 of your textbook
31 Gene Action: Protein Synthesis On your own, this is also a biology review topicInformation found on pages of your textbook.Show next slide and briefly refresh them on synthesis process…
32 Protein SynthesisDNA transcribed in nucleus to mRNA, leaves nucleus goes to ribosome there translated into amino acids, peptide bonds form between amino acids and polypeptide chain grows….
33 Somatic Cell DivisionDamaged, diseased, or worn out cells are replacedTwo types of cell division:Reproductive cell division-meiosisWill be discussed in later chaptersSomatic cell division-mitosisDivision into two identical cellsDivision occurs through a sequence of changes called the cell cycleTwo major parts to cell cycleInterphase: when cell is not dividingMitotic phase: when cell is dividingSomatic cell replacement replaces dead and injured cells and adds ones for tissue growth
34 Interphase 1st step is DNA replication Then production of new organelles and cytoplasmic components fro the new cellHigh metabolic activityA lot of cell growth
35 Mitotic PhaseMitosis followed by Cytokinesis (splitting of the cytoplasm)Chromosomes are visible during this phase under a microscopeCan you identify this phase? CLICK…prophaseCan you identify this phase? CLICK…anaphase
36 Nuclear Division: Mitosis Four stages:ProphaseChromatin condenses into visible chromosomesCentrioles migrate to opposite polesMitotic spindles form attach to centromeres ofchromatidsNuclear envelop breaks downMetaphaseChromatids line up at equator (metaphase plate)AnaphaseCentromeres split chromatids into chromosomesChromosomes dragged towards the polesTelophaseChromosomes uncoil into chromatinNuclear envelops reformsNucleolus reappearMitotic spindles break down
37 Cytoplasmic Division: Cytokinesis Division of cytoplasm and organelles between two new cellsBegins with formation of a cleavage furrow in plasma membrane that pinches inwardCells return to Interphase
39 Cellular DiversityAverage humans has about 100 trillion cells of varying sizesCell size is measured in micrometers (µm)1 micrometer = 1 one-millionth of a meterLargest cell in human body is an oocyte with a diameter of 140 µmAverage hair strands is ~100 µm in diameterCells can be round, oval, flat, cube-shaped, column-shaped, elongated, star-shaped, cylindrical, or disc-shapedShape is related to function