BIOL 1107 1nd EditionExam # 2 Study Guide Lectures: 11 - 18Each 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 glasslenses; 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 electronmicroscopes (TEMs)- Scanning electron microscopes (SEMs)- focus beam of electrons onto surface of aspecimen, 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 organellesEukaryotic 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 cellso They have internal membranes that partition cells into organelleso Plant and animal cells have most of same organelles (see plant vs animal)Eukaryotes Similarities ProkaryotesPlasma membrane No nucleusDNA in nucleus that isbounded by a membranousCytosol (semifluid substance) DNA in an unbound regioncalled the nucleoidnuclear envelopeMembrane-bound organelles Chromosomes (carry genes) No membrane-boundorganellesCytoplasm in region betweenplasma membrane andnucleusRibosomes (make protein) Cytoplasm bound by plasmamembrane- 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 volumeAnimal Cells Similarities Plant CellsNucleus, Nucleolus, DNA, Cell wallRibosomes, E.R Large central vacuoleChloroplastsUsually 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) synthesisRibosomes- 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 vesiclesEndoplasmic 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 studdedw/ 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 ERlumen. When muscle cell is stimulated by a nerve impulse, calcium ions rush back acrossER membrane into cytosol & trigger contraction of muscle cellsRough 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 vesiclesGolgi 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