BIOL 1107 1nd Edition Exam 2 Study Guide Lectures 11 18 Each section below includes material from the lecture homework and textbook Lecture 11 12 September 17 19 Chapter 6 A Tour of the Cell Cell simplest collection of matter that can be alive All cells related by their descent from earlier cells Thought usually too small to be seen by the unaided eye cells can be complex Microscopes used to visualize cells too small to see with the naked eye Light microscope LM visible light passed through specimen and then thorough glass lenses lenses refract bend the light so that image is magnified LMs magnify to about 1 000 times size of actual specimen Most subcellular structures including organelles too small to be resolved by LM So what can be used to study sub cellular structures Electron microscopes EMs Two types of EMs scanning electron microscopes SEMs and transmission electron microscopes TEMs Scanning electron microscopes SEMs focus beam of electrons onto surface of a specimen providing images that look 3 D Transmission electron microscopes TEMs focus beam of electrons through specimen mainly used to study internal structure of cells Cell fractionation takes cell apart and separates major organelles from one another centrifuges fractionate cells into component parts This process enables scientists to determine functions of organelles Eukaryotic vs Prokaryotic cells Basic structural and functional unit of every organism is one of two types of cells eukaryotic or prokaryotic Only bacteria and archaea prokaryotic cells Protists fungi animals and plants eukaryotic cells Eukaryotic cells generally much larger than prokaryotic cells o They have internal membranes that partition cells into organelles o Plant and animal cells have most of same organelles see plant vs animal Eukaryotes DNA in nucleus that is bounded by a membranous Similarities Plasma membrane Cytosol semifluid substance Prokaryotes No nucleus DNA in an unbound region called the nucleoid nuclear envelope Membrane bound organelles Cytoplasm in region between plasma membrane and nucleus Chromosomes carry genes Ribosomes make protein No membrane bound organelles Cytoplasm bound by plasma membrane Plasma membrane selective barrier that allows sufficient passage of oxygen nutrients and waste to service volume of every cell General structure of biological membrane is a double layer of phospholipids Metabolic requirements set upper limits on size of cells surface volume ratio of cell is critical As surface area increases by factor of n 2 volume increases by factor of n 3 Small cells have greater surface area relative to volume Animal Cells Similarities Nucleus Nucleolus DNA Ribosomes E R Plant Cells Cell wall Large central vacuole Chloroplasts Usually box square shape Nucleus contains most of DNA in eukaryotic cell Ribosomes use info from DNA to make proteins Nucleus contains most of cell s genes nuclear envelope encloses nucleus separating it from the cytoplasm Nuclear membrane is a double membrane each membrane consists of a lipid bilayer Pores regulate entry and exist of molecules from nucleus Shape of nucleus maintained by nuclear lamina composed of protein DNA in nucleus is organized into discrete units chromosomes Each chromosome is composed of a single DNA molecules associated w proteins DNA and proteins of chromosomes are together called chromatin Chromatin condenses to form discrete chromosomes as a cell prepares to divide Nucleolus located w in nucleus and is site of ribosomal RNA rRNA synthesis Ribosomes particles made of rRNA and protein Carry out protein synthesis in two locations 1 in the cytosol free ribosomes 2 on the outside of the endoplasmic reticulum or nuclear envelope bound ribosomes Endomembrane system regulates protein traffic and performs metabolic functions in cell Components of this system nuclear envelope endoplasmic reticulum ER Golgi apparatus lysosomes vacuoles plasma membrane These components are either continuous or connected via transfer by vesicles Endoplasmic Reticulum ER accounts for more than half of total membrane in many eukaryotic cells Consists of network of membranous tubules and sacs called cisternae Ribosomes are also attached to cytoplasmic side of nuclear envelope s outer membrane which is continuous w rough ER Two distinct regions of ER smooth ER lacks ribosomes and rough ER surface is studded w ribosomes Smooth ER synthesizes lipids metabolizes carbohydrates detoxifies drugs and poisons esp in liver cells store calcium ions esp in muscle cells Enzymes of smooth ER are important in synthesis of lipids including oils phospholipids and steroids For ex sex hormones and various steroid hormones secreted by adrenal glands produced in smooth ER Abuse of certain drugs such as barbiturates can decrease the affectiveness of certain antibiotics and other useful drugs In muscle cells specialized smooth ER membrane pumps cellular ions from cytosol into ER lumen When muscle cell is stimulated by a nerve impulse calcium ions rush back across ER membrane into cytosol trigger contraction of muscle cells Rough ER has ribosomes which secrete glycoproteins proteins covalently bonded to carbohydrates Distributes transport vesicles proteins surrounded by membranes Is a membrane factory for the cells grows in place by adding membrane proteins and phospholipids to its own membrane Ex certain pancreatic cells synthesize protein insulin in ER and secrete hormone into bloodstream Most secretory proteins glycoproteins Proteins produced by free ribosomes remain in cytosol Separatory proteins depart from ER wrapped in membranes of vesicles Golgi apparatus consists of flattened membranous sacs called cisternae Functions modifies products of ER manufactures certain macromolecules sorts and packages materials into transport vesicles After leaving ER many transport vesicles travel to Golgi Golgi apparatus especially extensive in cells specialized for secretion Cis usually located near ER Transport vesicles move material from ER to Golgi Products of ER are usually modified during transit from cis to trans region A vesicle that buds from ER can add its membrane and contents of its lumen to cis face by fusing with Golgi membrane Trans face gives rise to vesicles which pinch off or travel to other sites Lysosome membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins fats polysaccharides and nucleic acids Lysosomal enzymes work best in acidic environment inside