2Cell TheoryCells represent the basic structural and functional unit of life.Important unifying concept in biology.All organisms are composed of one or more cells.All tissues & organs are composed of cells.There is no life without cells!
3Cell TheoryCell theory states that all living organisms are composed of cells.Cells come from preexisting cells.
4Prokaryotic vs. Eukaryotic Cells All cells:Have DNAUse the same genetic codeSynthesize proteinsUse ATP in similar waysThis implies common ancestry.
5Prokaryotic vs. Eukaryotic Cells Prokaryotic cells – no nucleus or other membrane-bound organelles.Kingdom ArchaebacteriaKingdom EubacteriaEukaryotic cells – do have nucleus and membrane-bound organelles.Kingdom ProtistaKingdom FungiKingdom PlantaeKingdom Animalia
6Components of Eukaryotic Cells The plasma membrane surrounds the cell.The nucleus is the largest organelle.Double layered nuclear envelope.Cell Model
7Components of Eukaryotic Cells Cytoplasm refers to the cellular material between the cell membrane and nuclear envelope.Organelles such as the mitochondria, Golgi complex, centrioles, and endoplasmic reticulum are found in the cytoplasm.
8Plasma MembranePlasma membrane structure is described using the fluid mosaic model.
9Plasma MembraneTwo layers of phospholipid molecules oriented with hydrophilic heads toward the outside and hydrophobic tails inside.Fluid-like – flexible
10Plasma MembraneThe nonpolar nature of the hydrophobic ends in the interior of the membrane prohibit polar substances from crossing the membrane.Glycoproteins embedded in the membrane function in the transport of molecules across the membrane.
11NucleusThe nuclear envelope contains pores to allow molecules to move between nucleus & cytoplasm.Chromosomes are contained in the nucleus.Chromatin refers to loosely condensed DNA & proteins.
12NucleusNucleoli are specialized parts of certain chromosomes that carry multiple copies of the DNA used to synthesize ribosomal RNA.This rRNA combines with protein to from the two subunits of ribosomes.Ribosomes leave the nucleus through pores in the nuclear envelope.
13Endoplasmic Reticulum The nuclear envelope joins with a cytoplasmic membranous system – the endoplasmic reticulum (ER).Rough endoplasmic reticulum (RER) is covered with ribosomes. Smooth (SER) is not.
14Endoplasmic Reticulum Ribosomes on the RER synthesize proteins that enter the ER that will either be incorporated into the plasma membrane, exported from the cell, or they may be bound for lysosomes.Lipids and phospholipids are synthesized in the SER.
15Golgi ComplexThe Golgi complex is a stack of membranous vesicles where storage, modification, and packaging of protein products occurs.
17LysosomesLysosomes contain enzymes (proteins) that can breakdown foreign material like bacteria or worn out cellular components.Contents of lysosome would kill cell if membrane ruptured.May pour enzymes into food vacuoles.
18MitochondriaMitochondria are the powerhouses of cells – they contain enzymes that carry out the energy-yielding steps of aerobic metabolism. ATP is produced here.Composed of a double membrane – the inner membrane is folded into cristae.Mitochondria are self-replicating, containing their own circular DNA molecule.
19CytoskeletonEukaryotic cells have a cytoskeleton that provides support and often locomotion and movement of organelles.Composed of microfilaments, microtubules, and intermediate filaments.
20CytoskeletonMicrofilaments are made of the proteins actin and myosin and function in a cell’s ability to contract as seen in muscle cells.Actin microfilaments move molecules and organelles through the cytoplasm.
21CytoskeletonMicrotubules are larger tubular structures composed of the protein tubulin.Move chromosomes during cell division.Part of the structure of cilia & flagella.
22CytoskeletonMicrotubules radiate out from the centrosome – the microtubule organizing center.Located near nucleus.Not membrane bound.Centrioles are found in the centrosome.Centrioles composed of 9 triplets of microtubules.Replicate before cell division.
23CytoskeletonIntermediate fibers fall in between microfilaments and microtubules in size.There are five biochemically distinct types of intermediate fibers.
24Cilia & FlagellaCilia & flagella are motile extensions of the cell surface.In many single celled organisms they are a source of locomotion.In multicellular animals they usually sweep material past the fixed cell.Nine pairs of microtubules enclose a central pair.At the base is a basal body - identical to a centriole.
25PseudopodiaSome single-celled organisms, migrating cells in embryos, and white blood cells show ameboid movement.Cytoplasmic streaming through the action of actin microfilaments extends a pseudopodium outward.Some have specialized pseudopodia with microtubules that are assembled & disassembled to allow movement.
26JunctionsTight junctions form when cell membranes ofadjacent cells fuse.Function as seals.Adhesion junctions occur under tight junctions. Transmembrane proteins link across a small space and connect to microfilaments.
27JunctionsDesmosomes act as spot welds and increase the strength of the tissue.Hemidesmosomes are found at the base of cells and anchor them to connective tissue.Gap junctions are canals between cells that provide intercellular communication.
28MicrovilliMicrovilli are small fingerlike projections that have bundles of actin microfilaments.They serve to increase the surface area of the tissue as in the intestine.
29Membrane FunctionMembranes surround the outside of the cell and the organelles inside it.The plasma membrane acts as a selective gatekeeper.A substance may cross the membrane:By diffusionBy a mediated transport systemBy endocytosis
30Diffusion & OsmosisDiffusion is the movement of molecules from an area of high concentration to an area of low concentration. This tends to equalize the concentration.Down the concentration gradient.Solutes are molecules (e.g. salt) that are found in a solution.
31Diffusion & OsmosisCell membranes are selectively permeable – water can pass through, but not most solutes.Gases (oxygen & carbon dioxide), urea, lipid soluble solutes can cross the membrane.
32Diffusion & OsmosisOsmosis - if there is a membrane between two solutions with unequal concentration of solutes that can not cross the membrane, water will flow toward the side with less water / more solute until the two sides have equal concentrations.
34Diffusion & OsmosisAnimals utilize osmosis to control internal fluid and solute levels.The blood of marine fishes has 1/3 the salt content of the water. They are hypoosmotic to seawater.Freshwater fishes have blood that is saltier than the water. They are hyperosmotic to the water.If the solute concentrations were the same, the two solutions would be isoosmotic.
35Diffusion Through Channels Charged substances, like water and dissolved ions, can’t simply diffuse across the cell membrane.They pass through channels created by transmembrane proteins.Some channels always open.Some are gated channels.
36Diffusion Through Channels Gated channels require a signal to open or close them.Chemically-gated channels open or close when a signaling molecule binds to a binding site on the transmembrane protein.Voltage-gated channels open or close when the ionic charge across the membrane changes.
37Carrier Mediated Transport Sugars & amino acids must be able to enter cells and waste products must be able to leave.These molecules cross the membrane with the help of transporter proteins.Transporter proteins are specific.Facilitated diffusionActive transport
38Facilitated Diffusion In facilitated diffusion, the transporter protein binds to the substrate molecule on one side of the plasma membrane then changes shape to release it on the other side.Takes place in the direction of the concentration gradient.
39Active TransportActive transport requires energy (ATP) to transport molecules in the direction opposite the concentration gradient.
40Endocytosis Endocytosis is the ingestion of material by cells. Phagocytosis – cell eating – method of feeding by single- celled organisms.Pinocytosis – small molecules or ions are enclosed in vesicles called caveolae.Receptor-mediated endocytosis – method of bringing large molecules into a cell with the help of the protein clathrin.
42ExocytosisExocytosis - membranes of a vesicle inside the cell can fuse with the plasma membrane to discharge the contents of the vesicle outside the cell.Transcytosis – a substance may be picked up on one side of the cell, transported completely across the cell and discharged on the other side.
43Mitosis and Cell Division Mitosis is the process of nuclear cell division in nonreproductive, or somatic, cells.A fertilized egg, or zygote, divides by mitosis to produce a multicellular organism.Damaged cells are replaced by mitosis.
44ChromosomesIn cells that are not dividing, the DNA is loosely organized so that individual chromosomes can’t be distinguished – it is now referred to as chromatin.Before division, chromatin becomes more compact and chromosomes can be recognized.
45ChromosomesAll nonreproductive cells in a species have the same number of chromosomes.46 in humansHalf of these chromosomes come from each parent.Result is two sets of chromosomes.DiploidChromosome 1 from Mom and chromosome 1 from Dad are called homologous chromosomes.
46The Cell CycleCells come from preexisting cells through the process of cell division.Cell division – mitosis and cytokinesis – occupy a very small portion of the cell cycle.
47The Cell Cycle Interphase includes: Mitosis Cytokinesis G1 – growth phase where RNA and functional proteins are synthesized.S – DNA replication.G2 – growth phase where structural proteins are made.MitosisCytokinesis
48Chromosome StructureDuring S phase, each of the 2 homologues replicates, resulting in identical copies called sister chromatids.Chromatids remain connected at a linkage site called the centromere.
49Cell Division There are two phases of cell division: Mitosis – nuclear cell divisionProphaseMetaphaseAnaphaseTelophaseCytokinesis – division of the cytoplasmMultiple nuclear divisions not accompanied by cytokinesis result in a multinucleate cell.