Week 5 Notes
Week 5 Notes Bio 208
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This 7 page Class Notes was uploaded by Kylie McLaughlin on Monday September 28, 2015. The Class Notes belongs to Bio 208 at Northern Illinois University taught by Dr. Ed Draper in Fall 2015. Since its upload, it has received 15 views. For similar materials see Fundamentals of Cell Biology in Biological Sciences at Northern Illinois University.
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Date Created: 09/28/15
Week 5 Notes Chapter 6 cont Goloi apparatus group of stacked cisternae interconnected 2 sides 1 or forming face 2 or maturing face proteins from RER are delivered in to the cis face proteins go through each cisternae sequentially proteins and attached sugars are matu re proteins are 1 Sorted 2 Packaged into vesicles 3 Delivered to other parts of the cell Examples of lecosvlation 1 quotcore sugarsquot are added in the RER 2 Processing occurs in the GA a Some core sugars are removed b Other sugars are added 3 Glycosylation is important for a Proper protein folding b Protein stability c Cellcell adhesion Lvsosomes animals onlv hydroytic digestive enzymes degrade macromolecules protease nuclease lipase glycosidase maximum enzyme activity is at pH 5 cytoplasmic pH is about 7 1 Degrade food ingested by amino acids are released and used by the cell 2 breakdown and recycle a cells own organelles and macromolecules Central Vacuole is surrounded by a tonoplast membrane plants only FuncUons 1 Stores water vacuole is up to 95 of a cells volume 2 Stores ions water enters cell and vacuole due to and creates turgor pressure 3 Stores proteins protein bodies in seeds 4 Contains hydrolytic enzymes similar to animal lysosomes Peroxisomes also called olvoxisomes 1 Surrounded by a lipid bilayer membrane 2 Peroxisomes use 02 to cell compounds 3 H202 hydrogen peroxide is made which is toxic Must eliminate H202 4 an enzyme breaks down H202 Enerov Transducers endosvmbiont organelles 1 InfoIding of PM gt NE and other endomembranes 2 Endosymbiosis of aerobic heterotrophic bacteria gt mitochondria 3 Endosymbiosis of photosynthetic cyanobacteria gt chloroplasts endosymbiont organelles have bacterial features bacterialike ribosomes circular DNA Mitochondria site of oxidative phosphorylation 02 is used to break down food and make ATP mitochondria occur in nearly I eukaryotic cells basic features 1 Inner membrane from bacterial PM contains an ETC electron transport chain infoldings are cristae 2 Outer membrane from host PM 3 Matrix from cytoplasm of bacterial cell contains ribosomes DNA Krebs cycle enzymes Chloroplasts convert light energy to chemical energy in plants and algae basic features 1 Inner and outer envelope membrane inner from bacterial PM outer from host PM 2 Thylakoid membranes are in stacks or gana contain light reaction proteins and ETC 3 Stroma from cytoplasm of bacterial cell contains ribosomes DNA caIvin cycle enzymes the is a network of bers that organizes structures and activities in the cell the cytoskeleton is a network of bers extending throughout the cytoplasm it organizes the cells structures and activities anchoring many organelles it is composed of three types of molecular structures 1 Microtubules 2 Micro laments 3 Intermediate laments ce components can be revealed in living cells using speci c uorescent markers Roles of the Cvtoskeleton support and motility the cytoskeleton helps to support the cell and maintain its shape it interacts with to produce motility inside the cell vesicles can travel along tracks provided by the cytoskeleton Components of the Cytoskeleton three main types of bers make up the cytoskeleton microtubues are the thickest of the three components of the cytoskeleton micro aments also called actin laments are the thinnest components intermediate laments are bers with diameters in a middle range microtubues are hollow rods about 25nm in diameter and about 200m to 25 microns long functions of microtubules shaping the cell guiding movement of organelles separating chromosomes during cell division Centrosomes and Centrioles in animal cells microtubules grow out from a near the nucleus centrosome is also known as the microtubue organizing center or MTOC microtubues of the agellacilia do not originate from the centrosome in animal cells the centrosome has a pair of each with 9 triplets of microtubules arranged in a ring Cilia and Flagella microtubues contro beating of agea and ciia microtubuIecontaining extensions that project from some cells ciia and agella differ in their beating patterns agela long one or few per cell Flagellates human sperm ciia short many per cell Ciliates human trachea ciia and agea share a common structure a core of microtubules sheathed by the plasma membrane a that anchors the cilium or agellum a motor protein called which drives the bending movements of a cilium or agellum Unity agea cilia are used to move a cell or to move material past cells The structure of agella in all eukaryotes is identical We hypothesize that the ancestor of all eukaryotes had this type of ageum a homologous trait Analogous structure are structurally or functionally simiar due to adaptation to similar environmental pressures or challenges but evolved independently FageIar motility one end of the dynein molecule is permanently attached to a MT doublet The other end attaches temporarily to another MT doublet Cycles of attachmentdetachment requires ATP gt bending gt swimming motility Micro laments Actin Filaments micro aments are solid rods about 7nm in diameter built as a twisted double chain of actin subunits the structural role of micro laments is to bear tension resisting pulling forces within the cell they form a 3D network called the just inside the plasma membrane to help support the cells shape bundes of micro laments make up the core of microvilli of intestinal cells intestinal epithelial cells absorb digested food microvili give a large surface area for absorption actin MFs are the quotbonesquot that keep microvilli rigid are contractible units laments motor proteins pull on actin MFs in two directions sarcomere shortens gt contraction Amoeboid Movement ocaized contraction brought about by actin and myosin also drives amoeboid ces crawl along a surface by extending cellular extensions and moving toward them Cytoplasmic Streaming is a circular ow of cytoplasm within cells this streaming speeds distribution of materials within the cell in plant cells actinmyosin interactions and sol gel transformations drive cytoplasmic streaming Intermediate Filaments range in diameter from 812 nanometers larger than micro laments but smaller than microtubules they support cell shape and x organelles in place are more permanent cytoskeleton xtures than other two classes Extracellular components and connections between cells help coordinate cellular activities most cells synthesize and secrete materials that are external to the plasma membrane these extracellular structures are involved in a great many cellular functions genera functions 1 Mediates cell interactions with the environment 2 Mediates interactions between cells a Physical connections b Information transfer c Allows cells to interact and thereby build multicellular tissues and organs Cell Walls of Plants the cell wall is an extracellular structure that distinguishes plant cells from animal cells prokaryotes fungi and some unicellular eukaryotes also have cell walls protects the plant cell maintains its shape and prevents excessive uptake of water pant cell walls are made of cellulose bers embedded in other polysaccharides and protein pant cell walls may have multiple layers Plasmodesmata are channels between adjacent plant cells connect the cytoplasms adjacent cells gt celltocell communication through plasmodesmata water and small solutes and sometimes proteins and RNA can pass from cell to cell The Extracellular Matrix ECM of Animal Cells animal cells lack cell wall but are covered by an elaborate extracellular matrix ECM the ECM is made up of gycoproteins such as collagen proteoglycans and bronectin ECM proteins bind to receptor proteins in the plasma membrane called Functions of the ECM the ECM has an in uential role in the lives of cells ECM can regulate a cells behavior by communicating with a cell through integrins the ECM around a cell can in uence the activity of gene in the nucleus mechanica signaling may occur through cytoskeletal changes that trigger chemical signals in the cell CeHlunc ons three types of cell junctions are common in epithelial tissues at membranes of neighboring cells are pressed together preventing leakage of extracellular uid anchoring junctions fasten cells together into strong sheets communicating juntions provide cytoplasmic channels between adjacent cells Chapter 7 Phospholipid Structure 1 Fatty acid tails 2 Glycerol 3 Hydrophilic head group has positive and negative charges 4 Amphipathic hydrophilic and hydrophobic parts in water phospholipids spontaneously assemble no energy required the plasma membrane is the boundary that separates the living cell from its surroundings the plasma membrane exhibits selective permeability allowing some substances to cross it more easily than others Cellular Membranes are Fluid Mosaics of Lipids and Proteins the uid mosaic model states that a membrane is a uid structure with a quotmosaicquot of various proteins embedded in it proteins are not randomly distributed in the membrane phosphoipids in the plasma membrane can move in within the bilayer most of the lipids and some proteins drift literally rarey a lipid may ip op transversely across the membrane membranes must be uid to work properly they are usually about as uid as salad 0 membranes rich in unsaturated fatty acids are more uid than those rich in saturated fatty acids as temperature cools membranes switch from a uid state to a solid state the temperature at which a membrane solidi es depends on the types of lipids the steroid cholesterol has different effects on membrane uidity at different temperatures choestero is a uidity buffer at warm temperatures such as 37 C cholesterol restrains movement of phospholipids at cool temperatures it maintains uidity by preventing tight packing variations in lipid composition of cell membranes of many species appear to be adaptations to speci c environmental conditions abiity to change the lipid compositions in response to temperature changes has evolved in organisms that live where temperatures vary membrane structure results in selective permeability a cell must exchange materials with its surroundings a process controlled by the plasma membrane pasma membranes are selectively permeable regulating the cells molecular traf c pure lipid bilayers don39t exist in cells if they did they would be impermeable to almost everything Permeable few substances 1 Hydrophobic lipids 02 2 Small polar but not charged H20C02 lmpermeable most substances 1 Other polar molecules 2 I charged molecules and ions a membranes properties are mostly due to its associated proteins a membrane is a collage of different proteins often grouped together embedded in the uid matrix of the lipid bilayer proteins determine most of the membranes speci c functions integra proteins penetrate the hydrophobic core integra proteins that span the membrane are called transmembrane proteins an integral protein has hydrophobic and hydrophilic parts it assumes its proper 3D structure 3 formation only within a membrane hydrophobic regions of an integral protein consists of one or more stretches of nonpolar amino acids often called into alpha helices integra proteins are made in the RER lnteoral membrane proteins can move laterally but cannot ip op may be anchored to ECM outside andor to the cytoskeleton inside Peripheral proteins are more loosely associated within the membrane or integral proteins they can be inside or outside the cell
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