The Cell: An Overview Ch. 5; 5.3-5.5

The Cell: An OverviewCh. 5; 5.3-5.5

Eukaryotes: The NucleusNucleus is membrane bound nuclear envelope (2x layer)How do things move through the envelope?Just like the plasma membrane, proteins (nucleoporins) channels allow entrance (nuclear pore complexes)How do they know what goes in?Short AA sequence (nuclear localization signal) acts like a zip code for the nucleus

Eukaryotes: The NucleusWhat do you find inside the nucleus?nucleoplasm cytoplasm in nucleusChromatin DNA/Protein complexChromosomes condensed DNANucleolus mixture of gene regions and RNA complexes

Eukaryotes: RibosomesWhy do we have free floating and membrane bound ribosomes?Different products for different environments1) Free ribosomes produce proteins to be used in the cytosol2) Attached ribosomes produce proteins to be embedded in membranes or secretedBoth have complex organelle path after completion

Eukaryotes: Endoplasmic ReticulumSmooth ER makes lipids and digestive enzymes for drugs and toxinsRough ER makes secreted proteins and digestive enzymesWhat cells in the body would have the largest smooth and rough ER?Liver cells (smooth)Digestive tract (rough)

Eukaryotes: Golgi ComplexRows of flatten sacs (cisternae) receive vesicles from areas of the cell (at cis face), modify the contents, and send them to their next location (at trans face)Most proteins are embedded or secreted (exocytosis)Some molecules drawn into the cell (endocytosis) and destroyed by fusion with lysosomes

Eukaryotes: LysosomesDigestive sacs in animals cells (over 300) that act like recycling centersAcidic (pH ~5)Why is it important they only work in a high pH?Lowers risk of activity outside of lysosome; wont work in basic cytosolEnzymes made in rough ER and then vesicle formed from Golgi complexRoles:Autophagy digest useless organellesPhagocytosis digest bacteria pulled into the cell

Eukaryotes: MitochondriaSite of cellular respirationDouble layered membrane with reactions between the cristae and the matrixWhat about mitochondria suggest that they used to be independent organisms?The have their own DNA and ribosomes

Eukaryotes: MicrobodiesLarge vesicles that do various tasks:Phospholipid synthesisBreakdown fats and proteins to make ATPBreakdown toxinsPeroxisomes vesicles of catalaseWhat do they do?Breakdown hydrogen peroxide

Eukaryotes: CytoskeletonReinforce cell shape and allow movement around the cellLike your organs, a cells organelles must be held in place3 groups:MicrotubulesIntermediate FilamentsMicrofilaments

Eukaryotes: MicrotubulesLong, wide tubes (25nm) made of and tubulinCharge ends, with more activity on the + endWhy do they need charged ends?Can use ionic forces to hold them in place in the cellNetwork radiates from the cell center (centrosome) and have two perpendicular barrels (centrioles)Hold organelles in place and are tracks for vesicle movementMotor proteins (kinesins and dyneins)

Eukaryotes: MicrotubulesMain part of flagella and cilia9 + 2 complex 9 double tube units around 2 single tube unitsWave and oar-like movements push cell through mediumsFlagella are found in all 3 domains, but their genes are different. What does this tell us about flagella evolution?It was independent even though they have the same structure and function

Eukaryotes: Intermediate FilamentsMedium sized (8-12nm) fibers that connect microtubules/ microfilaments together; adds stabilityNot found in single-cell organismsTissue specific have different proteins depending on the what part of the organism they are in

Eukaryotes: MicrofilamentsThin fibers (5-7nm) of actin unitsCharged ends with more growth on the + endMain part of muscle tissueMyosin (motor protein) moves back and forth along microfibers causing contractionsCytoplasmic streaming movement of the cytoplasmCause amoeboid movementDivided cytoplasm during division

Eukaryotes: ChloroplastsPlastidAmyloplasts starch forming cells (potato)Chromoplasts red and yellow pigments give color to fruits and autumn leavesDouble membrane around the stroma (inner area) which is filled with a 3rd membrane that makes the thylakoids/granaThylakoids have chlorophyll pigments that absorb light energyHow are chloroplast and mitochondria similar?Both have their own DNA and ribosomes

Eukaryotes: Central VacuoleFunctions are giant lysosome for the cell; also a storage unitStores pigments that give flowers their colorTonoplast channels that allow transportation of materialsTurgor pressure pushes against weight of cell wellWhat happens with plants are low on water?The wilt; sag because turgor pressure drops

Eukaryotes: Cell WallExtracellular StructurePrimary soft/flexible layer expands as cell growsSecondary harder cellulose fibers used to strengthen walllignin complex alcohol structure stronger than concrete (by weight)Polysaccharide layer (middle lamella) acts like glue to hold plant cells togetherPectin used in syrup and jamsHow do cells communicate through these think walls?Channels (plasmodesmata) allow instant communication between plant cells

HomeworkRead Ch. 6Vocabulary for Ch. 6Test Your Knowledge Multiple choice questions on p. 114 and Interpret the Data on p. 115

There is too much vocabulary!