Biology 1113 Week 4 Notes
Biology 1113 Week 4 Notes Biology 1113
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This 19 page Class Notes was uploaded by Emily Notetaker on Wednesday September 14, 2016. The Class Notes belongs to Biology 1113 at Ohio State University taught by Dr. Ball and Dr. Weinstein in Fall 2016. Since its upload, it has received 13 views.
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Date Created: 09/14/16
A T our of the Cell Monday, September 12, 2016 9:22 AM Sections 6.2 - 6.7 Learning Outcomes o Successful students will be able to Explain the activities of the cell by relating cellular structure and function Explain the relationship between cell size and the surface area to volume ratio Explain the major differences between prokaryotes and eukaryotes Explain the major functions cellular organelles Chapter 6 Lecture Notes Monday, September 12, 2016 9:18 AM Cells All organisms are made of cells o The human body is made of 50-90 trillion cells o Lined up they would circle the earth 4.5x So how small are we talking? o Eukaryotic cells = 0.005 - 0.1 mm o Bacterial cells = less than 0.003 mm What is the largest cell? o An ostrich egg Why are cells so small o Cells take in raw materials and get rid of waste through the cell membrane o If a cell gets too large, there is not enough surface area (membrane) to let everything pass o Remember SA and volume formulas SA = 4πr 2 3 Volume = (4/3)πr Prokaryotes Eukaryotes Bacteria Everything else (plants, Much smaller animals, fungi, protists) NO defined True Nucleus nucleus (nucleoid) More complex NO membrane Have variety of bound organelles organelles DO have Surrounded by cell ribosomes membrane DO have cell membrane Parts of the cell: (Inside the cell) Nucleus (command central) o Holds most of the cell's DNA o Surrounded by nuclear membrane Nuclear pores control entry and exit o Nucleolus - synthesis of rRNA and assembly of ribosome subunits Ribosomes (protein factories) o Complexes of RNA and proteins o Carry out protein synthesis o Two types Free ribosomes = make proteins which will function in the cytosol Bound ribosomes = make proteins which will be inserted into membranes or secreted o Cells with high rates of protein synthesis have a lot of ribosomes Pancreatic cells have a few million ribosomes Endomembrane system o Composed of several different membranes Plasma membrane Nuclear envelope Endoplasmic Reticulum (smooth and rough) Golgi apparatus Lysosomes Vesicles/vacuoles o Carries out a variety of functions Protein synthesis Transport Metabolism Synthesis of lipids detoxification of poisons Endoplasmic Reticulum o Extensive network of membranes o Two distinct regions Smooth ER (Lacks ribosomes) Synthesis of lipids Metabolism of carbohydrates Storage of calcium ions Detoxification of drugs and poisons Drug tolerance increases because more and more smooth ER will be built Rough ER (studded with ribosomes) Synthesis of secretory proteins Expansion of membranes Golgi Apparatus (post office) o Modifies, stores and ships proteins Adds molecular tags (like zip codes) to proteins bound for secretion o Stacks of membranous sacs (not physically connected) Products transported by vesicles Lysosomes - waste receptacles of the cell o Membranous sac of enzymes that digest macromolecules Phagocytosis = engulfing solid particles and breaking them down Autophagy = recycles the cell's own organic material What would happen if your lysosomes did not work? You would get sick more often and it would be harder for you to get well Tay-Sachs Disease - There is a build-up of lipids in the brain cells and the brain starts to hurt, most children die from this Vacuoles (The handyman) o Perform a variety of functions Food vacuoles (formed by phagocytosis) Contractile vacuoles Pump out excess water Storage Reserves of important organic compounds Poisonous compounds Pigments Central Vacuole (plants) Stores inorganic ions Allows cells to grow large without increasing cytoplasm Help plant remain rigid Mitochondria (The powerhouse of the cell) o Found in almost all eukaryotic cells o Double membrane Smooth outer membrane Inner membrane has lots of folding (increases SA) o Contain their own DNA and ribosomes Inherited from mom o Site of Cellular Respiration (produces energy for the cell in the form of ATP) o Increasing mitochondrial density = increased metabolism?? This is true, metabolism is the rate at which stored material can be converted to energy Peroxisomes (The Detoxifier) o Contain enzymes that remove H+ ions from substrates and add them to O2 --> H2O2 (toxic) Also contain enzymes which convert into H2O2 --> H2O o Breakdown fatty acids o Detoxify alcohol and other toxic compounds Chloroplasts (The Sugar Factory) o Double membrane o Contain their own DNA and proteins o Contain chlorophyll o Site of photosynthesis Cytoskeleton o Structure Maintains cell shape Anchors cellular components o Motility Cellular movement Cellular highways Motor proteins "walk" organelles along cytoskeleton Composed of 3 main types of fibers Microtubules - cell motility (cilia or flagella) and chromosome movements in cell division **We do not need to know size or structure or location, only functions** Microfilaments - Muscle contraction and cell division (cleavage furrow formation) Intermediate Filaments - Anchorage of nucleus and certain other organelles, and formation of nuclear lamina (Outside the cell) Cell Walls o Found in plants (, bacteria, fungi, and some protists o Major function: Protection Maintain shape Prevent excess water uptake Extracellular Matrix o Found in animal tissues The "stuff" found outside of the cell o Main components: Collagen Proteoglycans Fibronectin o Functions: o Support o Segregate tissues o Regulation of intercellular communication Cell Junctions o Plasmodesmata (Plants) - cytoplasm filled channels that allow water and small solutes to pass from cell to cell o Tight Junctions (Animals) - form continuous seals around the cells to prevent leakage of extracellular fluid o Desmosomes (Animals) - fasten cells together into strong sheets o Gap Junction (Animals) - cytoplasmic channels (which allow small molecules to pass) between cells that allow for communication Question: What pathway is the most likely pathway taken by a newly synthesized protein that will be secreted by the cell? Rough ER --> Golgi Apparatus --> vesicles that will fuse with plasma membrane Cannot be lysosomes, because they will break down the newly made proteins Question: Most plant cells contain…? Answer: Both chloroplasts and mitochondria They contain both because they need mitochondria for cellular respiration Question: Which of the following is present in a prokaryotic cell? Answer: Ribosome Book Overview (pg. 97 - 121) Monday, September 12, 2016 1:49 AM Chapter 6 Section 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions All cells share these features: Bounded by a selective barrier (plasma membrane) All cells have a jellylike substance called cytosol Cytoplasm o In eukaryotic this only refers to the region between plasma membrane and nucleus Contain chromosomes Ribosomes There are two distinct types of cells: Prokaryotic (before nucleus) o Bacteria and archaea o DNA is concentrate in nucleoid A nucleoid is not membrane-enclosed o Does not include organelles Eukaryotic (true nucleus) o Protists, fungi, animals, and plants o DNA is an organelle called nucleus (bounded by double membrane) o Has a variety of specialized organelles which are suspended in cytoplasm o Are usually much larger than prokaryotic cells Size generally relates to funtion The cellular metabolism sets limits on cell size Main difference between these two cells is the location of their DNA Metabolic requirements: Plasma membrane - at the boundary of every cell there, it is a selective barrier that allows passage of oxygen, nutrients, and wastes o For each square micrometer of membrane, only a limited amount of a particular substance can cross per second Surface area to volume ratio As a cell increases in size, its surface area grow proportionately less than its volume. Therefore a smaller cell will have a greater ratio A high ratio is important in cells that exchange a lot of material with their surroundings (intestinal cells) Microvilli increases surface are without an increase in volume Eukaryotic Cell: Including the plasma membrane, the eukaryotic cell has many internal membranes that divide it into compartments, or organelles. The compartments allow for the cell to initiate many different metabolic processes in different environments. The plasma membrane and organelle membranes participate in the cell's metabolism. o Enzymes are built into the membranes The membranes are mostly made of phospholipids, other lipids, and proteins. Section 6.3: The eukaryotic cell's genetic instructions are housed in the nucleus and carried out by the ribosomes Nucleus: o Contains most of the genes in the cell (others are located in mitochondria and chloroplasts) o The nucleus is enclosed and separated from cytoplasm by the nuclear envelope The nuclear envelop is a double membrane made of lipids and proteins Perforated which allows for the entry and exit of proteins, RNAs, and complexes of macromolecules At the pores there is a net-like lining made of protein filaments called the nuclear lamina Keeps shape of nucleus Helps to organize material o Chromosomes - DNA is organized into these discrete units Carry genetic information Contains DNA molecule with proteins called chromatin Chromatin help DNA to coil Every species has a characteristic number of chromosomes in each cell Humans have 46 o Nucleolus A structure in the nucleus Synthesizes ribosomal RNA (rRNA) - instructions come from DNA Proteins from cytoplasm are made into subunits of ribosomes with rRNA o mRNA (messenger RNA) The nucleus directs protein synthesis by synthesizing mRNA according to the instructions from the DNA Then transported to cytoplasm and the ribosomes use its message to specify polypeptide functions (translating and transcribing) Ribosomes: o Made from rRNA and protein o Carry out protein synthesis In two cytoplasmic locales: Free ribosomes - suspended in the cytosol Enzymes that catalyze sugar breakdown Bound ribosomes - attached to outside of ER/nuclear envelope Make proteins that are inserted in membranes for packaging in lysosomes or secretion The two are structurally the same and ribosomes can alternate between both roles o Are not organelles because they are not membrane-bounded Section 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell The endomembrane system includes the nuclear envelope, the endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles and vacuoles, and plasma membrane. This system synthesizes proteins, transports protein into membranes, organelles, or out of the cell, deals with metabolism and movement of lipids, and detoxifies poisons. The membranes are related through physical continuity or the transfer of tiny vesicles (sacs made of membrane) The membranes are not identical in structure or function Endoplasmic Reticulum (Biosynthetic Factory): An extensive network of membranes (accounts for more than half of the total membrane in cells) Consists of a network of membranous tubules and sacs. Separates the cisternal space (reservoir for liquid) from the cytosol Two types of ER o Smooth ER Has no ribosomes so it is smooth Functions in metaboolic processes Synthesis of lipids Among the steroids produced are the sex hormones A lot of smooth ER especially in ovaries and testes Metabolism of carbohydrates Detoxification of drugs and poisons A lot of smooth ER in liver Storage of calcium ions In muscle cells Pumps calcium ions from cytosol to the ER lumen o Rough ER Ribosomes are embedded in rough ER Secrete proteins that are produced by the ribosomes Most secretory proteins are glycoproteins - proteins with carbohydrates covalently bonded to them After they are formed, the ER keeps them separate from the proteins produced by fee ribosomes Vesicles protect the protein and take them to one part of the cell to another Creates membrane proteins that builds to its own membrane The Golgi Apparatus (Shipping and Receiving Center) Receives, shorts, ships, and manufactures proteins Is made from stack of flattened membranous stack call cisternae o Cis face - receiving department of golgi o Trans face - shipping department of golgi Lysosomes (Digestive Compartments) A membranous sac of hydrolytic enzymes that digest (hydrolyze) macromolecules An acidic environment Carry out intracellular digestion o Phagocytosis - engulf smaller particles and food particles that act as nutrient for the cell Macrophages - a white blood cell that defends the body by engulfing and destroying bacteria and other invaders o Autophagy - recycle the cell's own organic material Fixes damaged organelles Continually renews the cell Vacuoles (Diverse Maintenance Compartment) Large vesicles derived from ER and Golgi Vacuolar membrane is selective in transporting solutes, therefore the solution inside is different from the cytosol Kinds of vacuoles: o Food vacuoles - formed by phagocytosis o Contractile vacuoles - pump excess water from cell o Central vacuole - develops the smaller vacuoles Plays a major role of growth in plant cells Section 6.5: Mitochondria and chloroplasts change energy from one form to another Mitochondria and chloroplasts are the organelles that convert energy to forms that cells can use for work. Mitochondria (powerhouse of the cell) o The site of cellular respiration Uses oxygen to make ATP from energy from sugars, fats, other fuels o Are found in all eukaryotic cells including plants, animals, fungi, and unicellular eukaryotes o The number of mitochondria depends upon the cell's level of metabolic activity o The mitochondrion has two internal compartments Intermembrane space Mitochondrial matrix - contains enzymes as well as mitochondrial DNA and ribosomes The large surface are of the inside allows for more productivity of cellular respiration Chloroplasts o Converts solar energy to chemical energy o Contains chlorophyll - a green pigment o Thylakoids - membranous system in the form of flattened, interconnected sacs that are inside the chloroplasts o Three compartments Intermembrane space Stroma - contains chloroplast DNA Thylakoid space o Photosynthesis o Is a plastid - specialized member of plant organelles Peroxisomes (oxidation) o A specialized metabolic compartment bounded by a single membrane o Contains enzymes that remove hydrogen atoms from substrates and transfer them while producing hydrogen peroxide and then eventually to water Section 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell Cytoskeleton - a network of fibers extending throughout the cytoplasm; plays a huge role in organizing the structures and activities of the cell Functions: o Mechanical support o Maintains shape of cell Balance by opposing forces Strong and resilient o Provides anchorage for the organelles o Can be easily disassembled in one part of cell and reassembled in another o Motility - changes in cell location and movements of parts Cytoskeleton must interact with motor proteins The organelles and vesicles can then use the motor proteins to "walk" along the cytoskeleton o Manipulates plasma membrane into being for food vacuoles and phagocytic vesicles Composed of three structures: Microtubules Microfilaments Intermediate Filaments Structure Hollow tubes Two intertwined strands Fibrous proteins coiled constructed from of actin, thin solid rods into cables, only found in tubulin the cells or some cells and vertebrates, made from proteins like keratins Shape Form Specialized Main and support the structural networks for bearing tension functions cell when proteins bind More Serve along the side permanent fixtures in as tracks so that Bear cells motor proteins can tension (pulling Reinforce move organelles forces) the cell and fix Cell Supports positions of motility (cilia or the cell's shape organelles, permanent flagella) Cell framework of entire Compre motility cell ssion resistant Contractio Often n of muscle cells disassemble and Contribute reassemble s to cytoplasmic streaming (speed the distribution of materials) Often disassemble and reassemble o Centrosomes and centrioles: Centrosome - where microtubules grow out from Often located near the nucleus Function as compression-resisting girders of the cytoskeleton Centrioles - a ring of nine sets of triplet microtubules that are within the centrosome as a pair Centrosomes with centrioles help to organize microtubule assembly However they are not in every animal cell or eukaryotic cell o Cilia and flagella: Microtubule-contain extensions that project from cells Cilia and flagella help propel unicellular eukaryotes through water Motile cilia occur in large numbers while flagella occur in one or a few Flagella are longer Flagella has a fish tail-like motion (sperm), and cilia has an oar motion Primary cilium - acts as a signal-receiving "antenna" for the cell Basal body - the anchor in the cell that holds the assembly for the microtubule assembly of cilium or flagellum Dynein - produce the bending movements of flagella and motile cilia Section 6.7: Extracellular components and connections between cells help coordinate cellular activities Cell wall - an extracellular structure of plant cells that distinguishes them from animal cells o Protects plant cell, maintains shape, and prevents excessive water uptake o Much thicker than plasma membrane o Made of polysaccharide cellulose microfibrils o There are three cell walls: Primary cell wall - a thin flexible wall Middle lamella - a thin layer rich in sticky polysaccharides called pectin Glues adjacent wall together Eventually strengthens wall once cell is fully grown Secondary cell wall - between plasma membrane and primary wall Deposited in several laminated layers Strong and durable matrix that is in charge of cell protection and support Extracellular Matrix (ECM) - equivalent to plant's cell walls o Made of glycoproteins like collagen that are embedded in a network woven proteoglycans and carbohydrate molecules o Cells attach to the ECM by fibronectin o Integrin binds to the plasma membrane and ECM and send signals back and forth between the two in order to integrate changes occurring inside and outside of the cell Cell Junctions o Plasmodesmata - channels that connect plant cells Cytosol pass through them in order to join the internal chemical environments of the cells This unifies them into one organism Water and solutes can pass freely from cell to cell o Animal cell junctions: Tight junctions - plasma membranes of other cell are bound together by proteins, very tightly pressed to each other in order to prevent leakage of extracellular fluid Desmosomes - Function like rivets that fasten cell together, intermediate filaments anchor them into place Gap Junctions - Like Plasmodesmata All are common in epithelial tissue (lines the external and internal surfaces of the body Ch.7 Lecture Notes Wednesday, September 14, 2016 9:22 AM Plasma Membrane: What's it made of? Lipids and Proteins o Phospholipids What property allows them to easily form membranes? Hydrophobic and hydrophilic ends Fluid Mosaic model o Fluid structure with a variety of proteins embedded or attached to it Membrane Proteins Different types of cells contain different membrane proteins 2 Major types: o Integral: embedded in the membrane Nonpolar portion of protein extends into the hydrophobic interior of the bilayer o Peripheral: loosely bound to surface of membrane Often interact with exposed surface of integral proteins Functions: o Transport o Enzymatic activity o Signal transduction o Cell-cell recognition o Intercellular joining o Attachment to the cytoskeleton and extracellular matrix **Don't need to memorize these** Question: Which of the following is true of integral membrane proteins? Answer: They are usually transmembrane proteins (a portion inside and outside) o All proteins have a tertiary structure o They are mobile within the bilayer Question: In order for a protein to be embedded in the cell membrane it would have to be… Answer: Both hydrophobic and hydrophilic Importance of Carbohydrates Necessary for cell-cell recognition o How liver cells distinguish themselves from muscle cells o How your body recognizes foreign invaders This is why you can't just give someone blood or a kidney ________________________________________________________________________