Bio Exam 2 Chapters 4 5 20 Chapter 4 4 1 Microscopes Reveal the World of the Cell Light microscope o Visible light is passed through a specimen or a thin slice of tissue through glass lenses o Can magnify objects about 1 000 times Electron Microscope o Focuses a beam of electrons through a specimen or onto a specimen Scanning Electron Microscope Helps study the detailed architecture of cell surfaces Makes it look 3D Transmission Electron Microscope Used to study the details of internal cell structure o Cannot be used to study living specimens because methods used to prepare the specimen kill the cells o The increase in the apparent size of an object o A measure of the clarity of an image o Ability of an optical instrument to show 2 nearby objects as separate o All living things are composed of cells and all cells come from other Magnification Resolution Cell Theory cells 4 2 Size of Cells Need of Gas Exchange Surface to Volume Ratio o Large cells have a greater surface area than small cells o Large cells have less relative surface to their volume than small cells Plasma Membrane o Boundary between living cell and its surroundings o Composed of 2 regions Two non polar fatty acids Head with negative phosphate group o Hydrophilic end of the bilayer faces outward exposed to the aqueous solutions on both sides of a membrane o Hydrophobic end faces inward mingling together and shielding self from water o Proteins are embedded throughout the bilayer Form channels that shield ions and polar molecules 4 3 Prokaryotic and Eukaryotic Cells Bacteria and Archaea consist of prokaryotic cells All other forms of life are eukaryotic cells Eukaryotic cells have a membrane bound nucleus Prokaryotic cells are structurally simpler All cells have o A plasma membrane o One or more chromosomes carrying DNA o Ribosomes that create protein o Cytoplasm In eukaryotes they bind to organelles Prokaryotes have no nucleus instead they have a nucleoid region which is where the DNA is but it doesn t have a membrane enclosing it The reason antibiotics can kill bacteria in humans is because we lack cell walls to protect entrance Flagella propel the cells in a liquid environment 4 4 Compartmentalization of Eukaryotes Organelles can be separated into 4 major functional groups o Nucleus and Ribosomes Carry out genetic control of the cell o ER Golgi Lysosomes Vacuoles Peroxisomes Involved in the manufacture breakdown and distribution of molecules o Mitochondria in all cells and Chloroplasts in plant cells Energy processing o Cytoskeleton Plasma Membrane and Cell Wall Structural support movement and communication between cells Cellular metabolism o Chemical activities of cells occurring within organelles Enzymes required for certain processes are built into the organelle membranes NOT located in plant cells o Lysosomes and centrioles ONLY located in plant cells o Chloroplasts vacuole cell wall Cell Wall Plasmadesmata o Contains polysaccharide cellulose o Channels in the cell wall that allow connection with other cells 4 5 Nucleus The Command Center Contains most of the cells DNA Controls cell activities by directing protein synthesis When not dividing chromatin appears as a mass Nuclear envelope perforated with protein linked pores to regulate movement of large molecules Nucleolus is the site of rRNA synthesis Nucleus also creates mRNA 4 6 Ribosomes Carry out the commands of the nucleus Free and bound ribosomes bound to the nuclear envelope and the ER Proteins made on free ribosomes function in the cytoplasm 4 7 Endomembrane System Includes the nuclear envelope endoplasmic reticulum Golgi lysosomes vacuoles and the plasma membrane Work together in the synthesis distribution storage and export of molecules Membranes of the ER are continuous with the nuclear envelope 4 8 Endoplasmic Reticulum Rough bound to ribosomes o Bound ribosomes attached to the ER produce proteins that will be inserted into the growing ER membrane transported somewhere else or be secreted o Secretory Proteins Polypeptides are synthesized by ribosomes and threaded into the cavity of the rough ER Sugars linked to the polypeptide making it a glycoprotein When ready for transport packaged into a transport vesicle Vesicle buds off from the ER membrane o Enzymes in the smooth ER are important in synthesis of lipids including oils phospholipids and steroids o In the liver ER has more detoxifying enzymes that ward off drugs and Smooth no ribosomes alcohol o Stores calcium ions 4 9 Golgi Apparatus After the ER transport vesicles arrive at the Golgi of Golgi correlates to how active the cell is in secreting proteins Golgi serves as a molecular warehouse and a finishing factory for the Er Sacs are not connected like the ER o One side of the Golgi serves as a receiving dock for transport vesicles o A vesicle fuses with a Golgi sac adding its membrane and contents to o Products of the ER are modified during their transport through the from the ER the receiving side Golgi o Other side of the Golgi is the shipping side which gives rise to vesicles which bud off and travel elsewhere Golgi enzymes modify the carbohydrates of the glycoproteins made in the ER removing the sugar 4 10 Lysosomes Membranous sac of the digestive enzymes Enzymes membranes of lysosomes are made by the ER and processed by the Golgi Fuse with food vacuoles and digest it Tay Sachs Disease o Lipid digesting enzyme is missing and brain cells become impaired by an accumulation of lipids 4 11 Vacuoles Helps the cell grow in size by absorbing water and enlarging Stockpiles vital chemicals and nets as a trash can In plants can contain poisons that protect the plant against herbivores o Caffeine nicotine 4 12 Review Some peroxisomes break down fatty acids to be used as cellular food Others detoxify harmful compounds or convert toxic to water 4 13 Mitochondria Carry out cellular respiration o Sugar in food to ATP Inner membrane encloses the mitochondrial matrix o Contains mitochondrial DNA and ribosomes Folds of the mitochondria are called cristae o Increase membrane s surface area enhancing mitochondria s ability to produce ATP 4 14 Chloroplasts Photosynthesizing organelles of all photosynthetic eukaryotes Inner membrane holds thick fluid called stroma Stroma contains chloroplast DNA ribosomes Interconnected sacs called thylakoids are inside o Each stack is called a granum Granum solar power packs 4 15 Mitochondria and Chloroplasts evolved by Endosymbiosis Endosymbiont theory o Mitochondria and