Introduction to Biology: Study Guide - Exam 2
Introduction to Biology: Study Guide - Exam 2 Biology 1107
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This 11 page Study Guide was uploaded by Cheyenne prather on Friday March 4, 2016. The Study Guide belongs to Biology 1107 at East Georgia State College taught by Dr. Silva in Winter 2016. Since its upload, it has received 46 views. For similar materials see General Biology in Biological Sciences at East Georgia State College.
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Date Created: 03/04/16
Biology: Exam #2 Study Guide Fundamental units of life All living organisms are made of cells, which are the simplest level of matter that can be alive The Microscope Used as a tool for Biologists to study and visualize cells Observation of cells with a microscope is necessary because they are usually too small to be seen with the naked eye Parameters of Psychology Magnification: Ratio of an object’s image size to its real size Resolution: Measure of the clarity of the image or minimum distance of two distinguishable points Contrast: Visible differences in brightness between parts of the sample Microscope Types Electron Microscope (Ems): Used to study subcellular structures Scanning Electron Microscope (SEMs): Focus a beam of electrons onto a specimen’s surface, producing 3D like imageries Transmission Electron Microscope (TEMs): Focus a beam of electrons through a specimen and mainly used to study a cell’s internal structure Cell Fractionation Separates the major organelles from one another Takes cells apart Enables scientists to determine the functions of organelles Biochemistry and Cytology o Help correlate cell function with structure 2 Types of Cells Prokaryotic o Archaea o Bacteria Eukaryotic o Protists o Fungi o Animals o Plants Basic Features of all Cells Plasma Membrane Cytosol Chromosomes Ribosomes Prokaryotic Cells No nucleus DNA in nucleoid: unbound region No membrane bound organelles Cytoplasm bound by plasma membrane Eukaryotic Cells DNA is nucleus bound by nuclear envelope Membrane bound organelles Cytoplasm between plasma membrane and nucleus Endomembrane System – regulates protein traffic and performs metabolic functions in the cell Plasma Membrane Nuclear Envelope Endoplasmic Reticulum Lysosomes Vacuoles The Plasma Membrane Selective barrier that allows passage of: o Oxygen o Nutrients o Waste The Nucleus Contains eukaryotic cell’s genetic instructions (Most DNA) Nuclear Envelope A double membrane that encloses the nucleus, separating it from the cytoplasm Nucleolus Located in the nucleus Ribosomal synthesis takes place Chromosomes Composed of a single DNA molecule associated with proteins (chromatin) Condenses to form discrete chromosomes as a cell prepares to divide Ribosomes Made of protein and ribosomal RNA Carries out protein synthesis in 2 places Smooth ER Synthesizes lipids, metabolizes carbohydrates, detoxifies drugs/poisons, and stores calcium ions Rough ER Contain bound ribosomes that secrete glycoproteins Distributes transport vesicles Considered the membrane factory Golgi Apparatus Consists of flattened membranous sacs called cisternae Works to modify products of the ER Manufactures particular macromolecules Sorts/packages materials into transport vesicles Lysosomes Membranous sac of hydrolytic enzymes that can digest macromolecules Works best in lysosome’s acidic environment Phagocytosis can occur where some types of cells can engulf another cell Lysosome fuses with food vacuole and digests the molecule Also uses enzymes to recycle cell’s own organelles and macromolecules, called autophagy Vacuoles Large vesicles derived from the ER and Golgi Apparatus Functions depend on the type of cell 3 Types of Vacuoles Food Vacuoles: formed by phagocytosis Contractile Vacuoles: pump excess water out of cell Central Vacuoles: hold organic compounds and water Cytoskeleton Network of fibers that: o Support o Motility o Organize structures and activities o Anchors many organelles o Maintains shape Composed of 3 molecular structures: o Microtubules o Microfilaments o Intermediate Filaments Roles: o Interacts with motor proteins to create motility Microtubules Thickest component of cytoskeleton Hollow rods made of tubulin Functions o Shape cell o Guide movement of organelles o Separate chromosomes during cell division Centrosomes and Centrioles Animal Cells o Microtubules grow out from a centrosome near the nucleus o The centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring Cilia and Flagella Microtubules control the beating of the cilia and flagella: microtubulecontaining extensions that project from some cells Differ in beating patterns Share common structure o A core of microtubules sheathed by a plasma membrane o A basal body that anchors the cilium or flagellum o A motor protein, Dynein, that drives the bending movements of a cilium or flagellum Microfilaments Solid rods made of actin and myocin Role o Bear tension, resisting pulling forces within the cell o Help support the cell’s shape Bunches of microvilli make up the core of microvilli of intestinal cells Intermediate Filaments Mainly made of Keratin Support cell shape and fix organelles in place More permanent cytoskeleton fixtures than microfilaments and microtubules Extracellular Components and Connections Between Cells Help coordinate cell activities Cell walls of plants Extracellular matrix of animal cells Plant’s Cell Wall Distinguish plant cells from animal cells Function o Protects plant cell, maintain shape, and prevents the uptake of excessive water Made up of: o Cellulose fibers embedded in other polysaccharides and protein Animal Cell’s Extracellular Matrix (ECM) Bind to receptor proteins in the plasma membrane called integrans Made up of: o Glycoproteins such as collagen, proteoglycans, and fibronectin Cell Junctions Neighboring cells in tissue, organs, or organ systems often adhere, interact, and communicate through direct physical contact Plant cells o Plasmodesmata Animal cells o Tight junctions o Desmosomes o Gap junctions Plasmodesmata Channels that perforate plant cell walls During the process o Water and small solutes can pass from cell to cell Tight junctions, Desmosomes, and Gap Junctions Animal cells Tight junctions o Pressed cells together preventing leakage of extracellular fluid Desmosomes o Anchoring junctions o Fasten cells together into strong sheets Gap junctions o Communicating junctions o Provide cytoplasmic channels between adjacent cells Mitochondria and Chloroplasts Change energy from one form to another Mitochondria o Sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Chloroplasts o Sites of photosynthesis Mitochondria and Chloroplasts Evolutionary Origin Similarities with bacteria o Enveloped by double membrane o Contain free ribosomes and circular DNA molecules o Grow and reproduce somewhat independently in cells Endosymbiont Theory Suggests and early ancestor of eukaryotes engulfed an oxygenusing nonphotosynthetic prokaryotic cell Engulfed cell becomes the endosymbiont The endosymbiont evolved into mitochondria At least one of these cells may have then taken up a photosynthetic prokaryote, which evolved into a chloroplast Mitochondria Structure o Outer membrane o Inner membrane folded into cristae and creates two compartments called: Intermembrane space Mitochondrial matrix Chloroplasts Contain chlorophyll and other enzymes and molecules that function in photosynthesis Found in leaves and other green plant and algae organs One of a group of plant organelles called plastids Structure o Thylakoids and granum o Stroma: internal fluid Peroxisomes Oxidative organelles Produce hydrogen peroxide and convert it to water Unknown how its related to other organelles Specialized metabolic compartments bounded by a single membrane Plasma Membrane: boundary that separates the living cell from its surroundings It is selective permeable Selective Permeable: allows some substances to cross it more easily than others Cellular Membranes: fluid mosaics of lipids and proteins Amphipathic: contains hydrophobic and hydrophilic regions Fluid Mosaic Model: states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Factors that Affect Membrane Fluidity Temperature Cholesterol Membrane Protein: Peripheral Proteins: bound to the surface of the membrane Integral Proteins: penetrate the hydrophobic core Transmembrane Proteins: integral proteins that span the membrane 6 Major Functions of Membrane Proteins: a. Transport b. Enzymatic activity c. Signal transduction d. Cellcell recognition e. Intercellular joining f. Attachment to the cytoskeleton and extracellular matrix Role of Membrane Carbohydrates Cell recognition Aquaporins: facilitate the passage of water Transport Across Plasma Membrane Passive transport Diffusion Osmosis Facilitated diffusion Active transport Cotransport Bulk transport Exocytosis Endocytosis Passive Transport: substances diffuse down their concentration gradient with no energy investment Dynamic Equilibrium: many molecules cross the membrane in one direction as in the other Osmosis: diffusion of water across a selectively permeable membrane Water Balance of Cells Without Cell Walls Tonicity: the ability of a surrounding solution to cause a cell to gain or lose water Isotonic Solution: solute concentration is the same as that inside the cell; no net water movement across the plasma membrane Hypertonic Solution: solute concentration is greater than that inside the cell; cell loses water Hypotonic Solution: solute concentration is less than that inside the cell; cell gains water Osmoregulation: the control of solute concentrations and water balance, is a necessary adaptation for life in such environments Water Balance of Cells Without Cell Walls • Turgid (firm): a plant cell in a hypotonic solution swells until the wall opposes uptake • Flaccid (limp): if a plant cell and its surroundings are isotonic, there is no net movement of water into the cell • Plasmolysis: in a hypertonic environment, plant cell loses water, the membrane pulls away from the cell wall causing the plant to shrink • Facilitated Diffusion: transport proteins speed the passive movement of molecules across the plasma membrane Transport Proteins: Channel proteins (ion channels) Carrier proteins Aquaporins Active Transport: moves substances against their concentration gradients, requires energy usually in ATP form Cotransport: when active transport of a solute indirectly drives transport of other substances; active transport driven by a concentration gradient Bulk Transport: requires energy and occurs by exocytosis and endocytosis Exocytosis: cell takes in macromolecules by forming vesicles from the plasma membrane 3 Types of Endocytosis Phagocytosis Pinocytosis Receptormediated endocytosis Phagocytosis: cell engulfs a particle in a vacuole, which then fuses with a lysosome to digest the particle Pinocytosis: molecules dissolved in droplets are taken up when extracellular fluid is “gulped” into tiny vesicles ReceptorMediated Endocytosis: binding of ligands to receptors triggers vesicle formation Ligand: any molecule that binds specifically to a receptor site of another molecule Energy Capacity to cause change Requirement of life o Comes from: § Sunlight § Chemical reactions Metabolism: totality of an organism’s chemical reactions Forms of Energy • Kinetic energy: energy associated with motion • Heat (thermal energy): kinetic energy associated with random movement of atoms or molecules • Potential energy: energy that matter possesses because of its location or structure • Chemical energy: potential energy available for release in a chemical reaction The First Law of Thermodynamics • Energy can be transferred or transformed, but it cannot be created or destroyed The Second Law of Thermodynamics • Every energy transfer or transformation increases the entropy (disorder) of the universe Metabolic Pathways Catabolic Pathways: Release energy by breaking down complex molecules into simpler compounds o Example: Cellular Respiration Anabolic Pathways: consume energy to build complex molecules from simpler ones o Example: Synthesis of protein from amino acids Bioenergetics: the study of how energy flows through living organisms Reactions occur: Spontaneously (without input of energy) Or require input of energy Figuring Out When a Reactions Occurs Without Input of Energy Measuring o The free energy change of a reaction Freeenergy: energy that can do work when temperature and pressure are uniform, as in a living cell Only processes with a negative change in free energy are spontaneous Free Energy, Stability, and Equilibrium Freeenergy is a measure of a system’s instability Equilibrium is a state of maximum stability Free Energy and Metabolism Exergonic Reaction: proceeds with a net release of free energy and it is spontaneous Endergonic Reaction: absorbs free energy from its surroundings and is nonspontaneous 3 Main Kinds of Work a Cell Does Chemical Transport Mechanical To do work, cells manage energy resources by: Energy Coupling: the use of an exergonic process to drive an endergonic one o Most energy coupling in cells is mediated by ATP ATP ATP o Composed of: Ribose (a sugar) Adenine (a nitrogenous base) 3 phosphate groups Energy is released from ATP when the terminal phosphate bond is broken Enzymes are Catalytic Proteins Catalyst: a chemical agent that speeds up a reaction without being consumed by the reaction Activation Energy The initial energy needed to start a chemical reaction How Enzymes Speed Up Reactions Enzymes catalyze reactions by lowering the: o Ea (activation energy) barrier Substrate Specificity of Enzymes The reactant is called substrate The enzyme binds to its substrate, forming an enzymesubstrate complex The reaction catalyzed by each enzyme is very specific The Active Site: the region on the enzyme where the substrate binds Catalysis in the Enzyme’s Active Site Substrate binds to the active site in an enzymatic reaction Active site decrease Ea barrier by: o Orienting substrates correctly o Straining substrate bonds o Providing a favorable microenvironment o Covalently bonding to the substrate Effects of Local Conditions on Enzyme Activity Enzyme’s activity affected by: o General environmental factors, such as temperature and pH o Each enzyme has an optimal pH and temperature in which it can function Cofactors Nonprotein enzyme helpers Can be organic or inorganic Coenzyme: organic cofactor o Example: vitamins Enzyme Inhibitors Competitive Inhibitors: bind to the active site of an enzyme, competing with the substrate Noncompetitive Inhibitors: bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective Feedback Inhibition Feedback Inhibition: the end product of a metabolic pathway shuts down the pathway o Important to the cell o It prevents a cell from wasting chemical resources by synthesizing more product than is needed
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