BIOLOGY 1 EXAM 2 STUDY GUIDE Chapter 6 Tour of the Cell Understand the process of cell fractionation specifically focusing on how this technique has furthered our understanding of the structure of cells As stated in class cell fractionation takes cells apart and separates the major organelles from one another Cell fractionation is what allows scientists to analyze each organelle by itself to determine the function of the organelle specifically One method of cell fractionation is centrifugation A centrifuge spins down the particles in a cell and separates the heavier larger particles and the smaller particles in a sample As a result of centrifuging a sample we will get a solid pellet at the base of our centrifuge tube and a supernatant liquid at the top The faster and longer the centrifuge the more the particles will be separated A ribosome so this would be the most difficult to fully centrifuge is the smallest component listed and separate as the mass is not that different We can continue centrifuging to dilute the sample I e taking the supernatant out of the separated sample centrifuging it taking the next supernatant out of this separated sample then centrifuging this to carefully separate the components of a cell nuclei mitochondria and chloroplasts microsomes and ribosomes respectively Note Centrifugation is the most common first step in most fractionations but it only separates components that differ greatly in size If we wanted a finer degree of separation that could be achieved by layering homogenate in a thin band on top of a dilute salt solution that fills a centrifuge tube This helps scientists purify and separate each of the individual macromolecules they would like to study from each other Be able to compare and contrast prokaryotic and eukaryotic cells with respect to general structure and the presence and appearance of particular organelles All Cells have a plasma membrane cytosol cytoplasm chromosomes and ribosomes This makes sense as a cell would need a barrier to protect it from the outside a substance in which to suspend particles in a genetic component and a site of protein synthesis in order to function Prokaryotic Cells DNA content These don t have a nucleus DNA is in an unbound region called a nucleoid instead These cells don t have membrane bound organelles My helpful hint Let s break the word prokaryote down Pro means before whereas karyote roughly means nut or kernel which we have adapted to the modern form of nucleus so the word prokaryote literally means before a nucleus This is an easy way to remember prokaryotes DON T have a nucleus the word itself is the definition 1 BIOLOGY 1 EXAM 2 STUDY GUIDE Eukaryotic Cells DNA content These have their DNA in a nucleus not a nucleoid Bounded by a membranous nuclear envelope Membrane Bound organelles Mitochondria Nucleus Endomembrane system to regulate protein traffic and perform metabolic fxns o Golgi Apparatus o Endoplasmic reticulum where ribosomes are o Lysosomes o Centrosomes o Chloroplast respective only to plant cells Also eukaryotic cells are much more complex than prokaryotic cells and are therefore larger in size and have cytoskeleton My helpful hint Let s break the word eukaryote down Eu means normal or good whereas as we know karyote roughly translates to nucleus So the word eukaryote therefore literally means a true nucleus this hopefully will help with understanding not just memorizing the term eukaryote Identify the different organelles of eukaryotic cells and understand the general function of each Nucleus This organelle contains most of the cell s genes and is usually the most conspicuous organelle It houses the cell s chromosomes and is the place where almost all DNA replication and RNA synthesis occur in a Eukaryote Ribosomes These are particles made of ribosomal RNA and protein this is commonly known as the site of protein synthesis Ribosomes are found in the Cytosol free and on the ER nuclear envelope bound Plasma Membrane a selectively permeable phospholipid bilayer with embedded proteins This structure controls movement of substances in and out of the cell Eukaryotic Specific Endomembrane System Nuclear Envelope The nuclear envelope is what houses the nucleus and separates it from the cytoplasm in a eukaryote of course as we understood from the above question prokaryotes have no nucleus This envelope has our standard double lipid bilayer membrane Endoplasmic Reticulum Accounts for more than half of the total membrane in many eukaryotic cells continuous with nuclear envelope o Smooth ER no ribosomes present Involved with production of lipids and steroids carb metabolism and detoxification o Rough ER ribosomes are bound to surface and these produce membrane associated proteins Similar in fxn to the Smooth ER This distributes transport vesicles proteins surrounded by membranes Aka Membrane factory for the cell Golgi Apparatus contains flattened membranous sacs called cisternae This structure is active in synthesis modification of ER products sorting and secretion of cell products into transport vesicles 2 BIOLOGY 1 EXAM 2 STUDY GUIDE o The cis face is our receiving side while the trans face is our shipping side o Think of the Golgi as our post office organelle as the post office does a majority of the same shipping and receiving activities Lysosomes A membranous sac of hydrolytic enzymes that can digest macromolecules These enzymes hydrolyze proteins fats polysaccharides and nucleic acids The optimal environment for lysosomal enzymes is an acidic environment inside the lysosome o Helpful Hint I like to think of the cleaner Lysol to remember lysosomes Lysosomes clean up debris and other unwanted byproducts we don t want similar to the cleaning solution Lysol o The lysosomes also use enzymes to help recycle the cell s own organelles and macromolecules a process called autophagy Auto means self Phago roughly means eating Therefore autophagy literally means eating oneself in other words part of the cell the lysosome is eating itself to help rebuild itself Vacuole a storage bubble created within a cell Vacuoles store food nutrients or even waste through a process called phagocytosis phago eating cytosis pertaining to the cell Therefore phagocytosis means The cell is eating o Often a lysosome will fuse with a vacuole to digest the waste being stored here So if we say our vacuole is a house and we know that the Lysosome is our cleaner this can be comparable to our house cleaner coming to our house
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