MCB 150 Lecture Notes Lecture 3 8 29 14 Eukaryotic Cell Plasma membrane is boundary that separates the cell from its surrounding It s has selective permeability Formed by a lipid bilayer usually separate cells by 15 nm Electron microscopy is used to look at cell membranes Nucleus is the control center of the cell Separates eukaryotes from prokaryotes It s separated from the cytoplasm by TWO lipid bilayers Nuclear pore complexes allow for the passage of materials into and out of nucleus 1 Maintenance and replication of the genome It stores DNA 2 Distribution of genetic information aka transcription It makes copies of the blueprints or regions of DNA 3 Production and assembly of ribosomal subunits They make proteins by carrying out the process known as transcription Dark areas are usually denser than others in electron microscopy or there s more stuff there Nuclei usually are dark regions in an electron microscopy Nucleolus is a region within the nucleus where ribosomes are made The mitochondrion is the cell powerhouse that creates ATP molecules that power the pro cesses of the cell There could be a thousand of mitochondria or barely any depending on the cell This depends on the function of the cell cells adapt to their needs The rough endoplasmic reticulum is a physically continuos region with the outer membrane of the nuclear membrane Used for synthesis of proteins the dots on the RER are ribosomes that create proteins Other ri bosomes are available in the cell however Any protein that is created to be secreted OUTSIDE the cell HAS to start by being translated on a ribosome on the surface of the RER It s also used for modification of proteins that are synthesized on the surface of the RER The smooth endoplasmic reticulum is physically continuous with the RER it has no ribosomes so no translation occurs there Lipid production Cellular detoxification by enzymes that dissolve them in water to be released as waste such as urine Stores calcium The Golgi apparatus is the physically connected to the RER and it continues modification of proteins released from the RER It takes proteins or molecules to where they are supposed to be Ribosomes are NOT organelles this is because it s not separated by a membrane It just con tains proteins and RNA They are machines that make proteins They are REALLY small 50 nm in length at times Multiple ribosomes can work together but not on the same molecule These groups are called polysomes or polyribosomes The eukaryotic cytoskeleton is appropriately named because at the cellular level these fibers and their associated motor proteins perform similar roles as an animal s musculoskeletal sys tem Microfilaments are responsible for cell locomotion and the cell s structural characteristics Microtubules serve as intracellular highways for transporting vesicles and organelles they are also required for cellular locomotion via flagella and cilia Intermediate filaments are rope like structures that anchor organelles and intercellular junc tions called desmosomes They are specialized for bearing tension Macromolecules polymers represent 26 of the cell and are made up of monomers Four types of macromolecules and their monomers 1 Proteins amino acids 2 Lipids 3 Carbohydrates monosaccharides 4 Nucleic Acids nucleotides Membrane lipids are composed of fatty acids and glycerol Condensation or dehydration synthesis is the process in which two monomers are bound to gether by the release of one water molecule In hydrolysis a water molecule is consumed to break off two monomers Polysaccharides Carbohydrates are made from condensation reactions bringing together monosaccharides Used as Energy source Structural roles like insect exoskeletons and cell wall Cell identification recognition The word carbohydrate can refer to either the polymer cellulose or the monomer glucose The general empirical or simplified formula of a carbohydrate is CH2O It has H C OH as the backbone of each carbohydrate Lecture 4 9 3 14 Polysaccharides Monosaccharides are typically found with 3 5 or 6 car bons Linear chains show the carbon chains as vertical diagrams with 1 6 or whatever the number of carbons may be In circular or ring chains Carbon 1 is usually on the right edge of the diagram and the sequence then moves clock wise until it reaches Carbon 6 which is show above the ring structure In the circularization of glucose either alpha glucose or beta glucose forms because the hydrox ide right after Carbon 5 can spontaneously rotate without needing any enzymes or catalysts to make this happen In alpha glucose the lone hydrogen atom is above Carbon 1 and in beta glucose the lone hydrogen atom is below Carbon 1 with the hydroxide on either side of the first carbon Some monosaccharides have identical formulas they are known as isomers When a carbonyl group C O is at the end of the chain the sugar is known as a aldehyde sugar or aldose When the carbonyl group is in the middle of the chain it s known as a ketone sugar or a ketose All of these are hexoses 6 carbon sugars however When circularizing a ketone structure it has one fewer side on its structure because on of the carbons the first one branches out to the bottom In aldoses however the structure has as many sides as the number of sugars it has Other monosaccharides have similar but not identical formulas similar structures and related figures However they are very similar in function which is beneficial in cells Trioses or three carbon sugars C3H6O3 also exist as aldoses and ketoses Glyceraldehyde is a conversion of the molecule glycerol and it is an example of a triose It s very important in biological pro cesses it s also an aldose Trioses are too small to circularize so they appear in their linear forms Five carbon sugars include ribose aldose and ribulose ke tose The same rules of ring structures of hexoses apply in pentose aldehyde sugars Two monosaccharides can be brought together to form a very simply polysaccharide called a disaccharide via a cova lent bond called a glycosidic linkage However this has to be more specific For maltose disaccharide in the image on the right it s known for having an alpha 1 4 glycosidic link age Cellobiose not shown is a disaccharide of beta glucose and another glucose Glucose and galactose together form lactose Glucose and fructose together form sucrose ta ble sugar Several monosacharrides 50 ish form a oligosaccharides These are significant because they usually link to other molecules When covalently bonded