Biology 1020-Study Guide for Exam 2-Dr. Sundermann
Biology 1020-Study Guide for Exam 2-Dr. Sundermann Biol 1020 - 001 (BIOL, Christine A. Sunderman, Principles of Biology (1020))
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Study Guide for Exam 2 Biology 1020 Dr. Sundmermann All information comes from Textbook and Class Lectures Chapter 6: Cell Structure and Function The Fundamental Unit of Life: o All organisms are made of cells o A cell is the simplest collection of matter that can be alive Eukaryotic Cells and Prokaryotic Cells o There are two distinct types of cells: 1) Prokaryotic 2) Eukaryotic o Prokaryotic= organisms in the domains Bacteria and Archaea o Eukaryotic= organisms in the domains Protists, fungi, animals, and plants Comparing Prokaryotic and Eukaryotic Cells: o All cells have three basic features: 1) They are all bound by a plasma membrane which is a selective barrier 2) They all have a cytoplasmthis is where all the subcellular components are suspended 3) All cells must have nucleic acid: they contain chromosomes which carry genes in the form of DNA and they have ribosomes which make proteins o Major difference between prokaryotic and eukaryotic cells is the location of their DNA o DNA is located: 1) Eukaryotic cell = most of the DNA is in an organelle called the nucleus, which is bounded by a doublemembrane 2) Prokaryotic = the DNA is concentrated in a region that is not membraneenclosed called the nucleoid o Interior of either type of cell is called the cytoplasm Eukaryotic cell = cytoplasm is the region between the nucleus and the plasma membrane; in the cytoplasm, suspended in cytosol, are a variety of different organelles of specialized form and function Prokaryotic cell = cytoplasm is organized into different regions; do not have a variety of different organelles of specialized form and function suspended in the cytosol which is within the cytoplasm o Eukaryotic generally larger in size than prokaryotic cells o Size is a general feature of the cell structure that relates to its function o The logistics of carrying out cellular metabolism sets limits on cell size o Plasma membrane: functions as a selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell o Ratio of surface area to volume is critical because only a limited amount of a particular substance can cross per second o As a cell increases in size, its surface area grows proportionately less than its volume o Features of a plasma cell membrane: 1) Phospholipid bilayer 2) Integral membrane proteins 3) Peripheral membrane proteins 4) Cholesterol 5) Carbohydrate receptors 6) Glycolipid 7) Glycoprotein BE ABLE TO IDENTIFY PARTS OF THE PLASMA MEMBRANE OF THE FLUID MOSAIC MODEL OF MEMBRANE STRUCTURE Here are two different representations of the plasma membrane o 3 Types of Bacteria: 1) Rods 2) Cocci 3) Spirilla o These bacteria do not have a nucleus o All they have is a structure called a nucleoid that contains 1 molecule of DNA o Major Structural Features of a Prokaryotic: Nucleoid Ribosomes Plasma Membrane Cell Wall B E ABLE TO TELL THE FUNCTION OF EACH OF THESE STRUCTURES AND BE ABLE TO LABEL THEM ON A DIAGRAM OF A CELL AND BE ABLE TO RECOGNIZE WHAT THEY LOOK LIKE FROM THEIR ELECTRON MICROGRAPH Cell Structure of Eukaryotic Cells 1) Nucleus: Contains most of the genes in the eukaryotic cell Nuclear envelope: encloses the nucleus separating its contents from the cytoplasm Nucleus is doublemembrane bound Nuclear pores: regulates the entry and exit of proteins and RNS as well as large complexes of macromolecules in and out of the nucleus Nuclear lamina: a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope Nuclear matrix: a framework of protein fibers extending throughout the nuclear interior The nucleus is where we will find the DNA DNA exists in the nucleus in two states: 1. Chromosomes: structures that carry the genetic material; cell is dividing/cell will divide; DNA is highly condensed 2. Chromatin: complex of DNA and proteins making up chromosomes; cell not dividing therefore DNA is uncondensed or dispersed Nucleolus: ribosomal RNA is synthesized from instructions in the DNA; proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes The subunits of ribosomes then exit the nucleus through the nuclear pores to the cytoplasm where a large and a small subunit can assemble into a ribosome Nucleus known as the “control center” of the cell There is a lot of DNA in each nucleus 2) Ribosomes: Complexes made of ribosomal RNA and protein Ribosomes: carry our protein synthesis Ribosomes are not membrane bound and therefore not technically considered an organelle Cells that have high rates of protein synthesis have particularly large numbers of ribosomes Ribosomes build proteins in two cytoplasmic locations Two types of ribosomes: 1. Free Ribosomes: suspended in the cytosol; these ribosomes make protein to use within the cytosol 2. Bound Ribosomes: attached to the outside of the endoplasmic reticulum or nuclear envelope; these ribosomes make proteins that are destined for insertion into membranes, for packaging within certain organelles (such as lysosomes), or for export from the cell 3) Smooth Endoplasmic Reticulum: Functions in diverse metabolic processes: synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions Enzymes of the smooth ER are important in the synthesis of lipids, including oils, steroids, and new membrane phospholipids Cells that synthesize and secrete these hormones are rich in smooth ER Other enzymes of smooth ER help detoxify drugs and poisons, especially in liver cells Detoxification usually involves adding hydroxyl groups to drug molecules, making them more soluble and easier to flush from the body Smooth ER also stores calcium ions When a muscle cell is stimulated by a nerve impulse, calcium ions rush back across the ER membrane into the cytosol and trigger contraction of the muscle cell 4) Rough Endoplasmic Reticulum: Many cells secrete proteins that are produced by ribosomes attached to rough ER Certain pancreatic cells synthesize the protein insulin in the ER and secrete this hormone into the bloodstream Glycoproteins: secretory proteins with carbohydrates covalently bonded to them After secretory proteins are formed, the ER membrane keeps them separate from proteins that are produced by free ribosomes and that will remain in the cytosol Secretory proteins depart from the ER wrapped in the membranes of vesicles that bud like bubbles from a specialized region called transitional ER Transport vesicles: vesicles in transit from one part of the cell to another Rough ER is a membrane factory for the cell It can grow in place by adding membrane proteins and phospholipids to its own membrane Makes membrane phospholipids 5) Golgi Apparatus: The transport vesicles that leave the rough ER then go to the Golgi Apparatus The Golgi Apparatus is the warehouse for receiving, sorting, shipping, and even some manufacturing Products of the rough ER, such as proteins, are modified and stored and then sent to other destinations Golgi apparatus is especially extensive in cells specializing in secretion It consists of flattened membranous sacscisternae Vesicles concentrated in the vicinity of the Golgi apparatus are engaged in the transfer of material between parts of the Golgi and other structures There are two sides of the Golgi apparatus: 1. Cisface: receiving department; located near the ER; convex side 2. Transface: shipping department; concave side A vesicle buds from the ER and adds its membrane and the contents of its lumen to the cisface by fusing to the Golgi membrane The vesicles pinch off of the transface and travel to other sites Products of the ER are usually modified during their transit from the cisregion to the trans region The Golgi apparatus can remove some sugar monomers and substitutes other which produces large varieties of carbohydrates Golgi apparatus can also alter membrane phospholipids It can manufacture some macromolecules Cargo is carried through and modified from the point it enters on the cisface to when it departs from the transface Before the vesicle of modified product leaves the Golgi apparatus in a budding vesicle, it sorts the products and targets them for various parts of the cell Is like the “packaging center” Recap of Protein Travel from synthesis to final product: Protein synthesized in the ribosomesleaves ribosomes in little vesiclesvesicles attach to the Golgi apparatusprotein sorted insidefinished protein leaves the Golgi apparatus 6) Lysosome: Membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest (hydrolyze) macromolecules Hydrolytic enzymes and lysosomal membrane are made by rough ER and then transferred to the Golgi apparatus for further processing Amoebas and many other unicellular eukaryotes eat by engulfing smaller organisms or food particlesthis is called phagocytosis The food vacuole formed then fuses with a lysosome whose enzyme digests the food Digestion products pass into the cytosol and become nutrients for the cell They can kill bacteria by fusing to them Apoptasis: programmed cell death Ex. Fetal development: digest tissue to make the five fingers of our hands (this is a type of remodeling) Some genetic diseases are called lysosomal storage diseases which is due to the lack of one or more crucial lysosomic enzymes Ex. Tay Sachs: missing an enzyme important for lipid digestion Lysosomes also use their hydrolytic enzymes to recycle the cell’s own organic materialcalled autophagy They maintain a fairly low pH inside by actively pumping protons into themselves 7) Vacuole: Large vesicles derived from the endoplasmic reticulum and Golgi apparatus Food vacuoles: engulfed smaller molecules or food particles process called phagocytosis Contractile vacuoles: pump excess water out of cells thereby maintain a suitable concentration of ions and molecules inside the cell; found in eukaryotes living in fresh water Central vacuoles: solution inside central vacuoles are the plant cell’s main repository of inorganic molecules, including potassium and chloride; plays a major role in the growth of plant cells which enlarge as the vacuole absorbs water 8) Mitochondria: Sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugar, fats, and other fuels Some cells have a single large mitochondrion, but more often a cell has hundreds or even thousands of mitochondria The number of mitochondria correlates with the cell’s level of metabolic activity Mitochondria are doublemembrane bound Each of the two membranes enclosing the mitochondrion is a phospholipid bilayer with a unique collection of embedded proteins The outer membrane: smooth Inner membrane: also called cristaeis convoluted; divides mitochondrion into two internal compartments 1. First intermembrane space is the narrow region between the inner and outer membranes 2. Second compartmentcalled mitochondrial matrix is enclosed by the inner membrane Mitochondrial matrix: contains many different enzymes as well as the mitochondrial DNA and ribosomes Enzymes in the matrix catalyze some of the steps of cellular respiration The cristae give the inner mitochondrial membrane a large surface area, thus enhancing the productivity of cellular respiration Produces the majority of energy in the form of ATP for the cell/organism The DNA in the mitochondria is prokaryotic like They make their own DNA therefore they are “selfreplicating” 9) Chloroplasts: Contain the green pigment chlorophyll, along with enzymes and other molecules that function in the photosynthetic production of sugar Contents of chloroplasts are partitioned from the cytosol by an envelope consisting of two membranes separated by a very narrow intermembrane spacedoublemembrane bound Thylakoids: inside the chloroplast is another membranous system in the form of flattened, interconnected sacs Granum: the name of thylakoid stacks Stroma: fluid outside the thylakoids; contains the chloroplast DNA and ribosomes as well as many enzymes Membranes of the chloroplast divide the chloroplast space into three compartments: 1. Intermembrane space 2. The stroma 3. The thylakoid space Chloroplasts are mobile and move around the cell along tracks of cytoskeleton Contain their own DNA therefore they are “selfreplicating” Specialized member of a family of closely related plant organelles called plastids Two types of plastids are amyloplast and chromoplast Amyloplast: a colorless organelle that stores starch in plants Chromoplast: pigments that gives fruits and flowers their orange and yellow hues 10)Peroxisomes: Special metabolic compartment bounded by a single membrane Contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen which produces hydrogen peroxide as a byproduct Some peroxisomes use oxygen to break fatty acids down into smaller molecules that are transported to mitochondria and used as fuel for cellular reparation Peroxisomes in the liver detoxify alcohol and other harmful compounds by transferring hydrogen from the poisons to oxygen The enzymes that produce hydrogen peroxide and those that dispose of this toxic compound are sequestered away from other cellular components that could be damaged Glyoxysomes: specialized peroxisomes are found in the fatstoring tissues of plant seeds; membrane bound; will convert oil into carbohydrates (simple sugars) that are then converted into energy; they use glyoxysomes for energy until they sprout their first leaves which is when they use photosynthesis Organelles contain enzymes that initiate the conversation of fatty acids to sugar, which the emerging seedling uses as a source of energy and carbon until it can produce its own sugar by photosynthesis Cytoskelton of Cells: o Cytoskeleton: a network of fibers extending throughout the cytoplasm o The eukaryotic cytoskeleton, which plays a major role in organizing the structures and activities of the cell, is composed of three types of molecular structures: 1. Microtubules 2. Microfilaments 3. Intermediate filaments o Most obvious function of the cytoskeleton is to give mechanical support to the cell and maintain its shape o The cytoskeleton is stabilized by a balance between opposing forces exerted by its elements o Provides anchorage for many organelles and even cytosolic enzyme molecules o Cell motility: both changes in cell location and movements of cell parts o Motor proteins interact with cytoskeleton to cause cell motility o Cytoskeletal elements and motor proteins work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell o Microtubules = thickest o Microfilaments = thinnest o Intermediate filaments = bigger than microfilaments but smaller than microtubules 1) Microtubules: Thickest in diameter Hollow rods constructed from a globular protein called tubulin Each tubulin protein is a dimer which means it’s a molecule made up of two subunits Microtubules grow in length by adding tubulin dimers; they can also be disassembled and their tubulin used to build microtubules elsewhere in the cell They shape and support the cell and also serve as tracks along which organelles equipped with motor proteins can move Microtubules guide vesicles from the ER to the Golgi apparatus and from the Golgi to the plasma membrane Variety of Functions: Skeletal means it participates in structural support of the cell Ex. Cytoplasmic microtubules Participates in motility Ex. Forms structures called cilia: Cilia found in ciliates which are protists Cilia are like oars on a boat In humans, ciliated cells line the repertory tract or in females it lines the oviduct Also found in flagella Flagella found in flagellates They are long They are whiplike Usually only find one or two Found in protists like euglena In humans, found in sperm cells The function of flagella is motility Flagella and Cilia: Specialized arrangements of microtubules are responsible for the beating of flagella and cilia which are microtubulecontaining extensions that project from some cells Many unicellular eukaryotes are propelled through water by cilia and flagella that act as locomotor appendages When cilia or flagella extend from cells that are held in place as part of a tissue layer, they can move fluid over the surface of the tissue Motile cilia usually occur in large numbers on the cell surface Flagella and cilia differ in their beating patterns Flagellum has an undulating motion like the tail of a fish Cilia work more like oars, with alternating power and recovery strokes, much like the oars of a racing crew boat Cilium may also act as a signalreceiving “antenna” for the cell Cilia that have this function are generally nonmotile, and there is only one per cell Membrane proteins on this kind of cilium transmit molecular signals from the cell’s environment to its interior, triggering signaling pathways that may lead to changes in the cell’s activities Motile cilia and flagella share a common structure Each motile cilia or flagella has a group of microtubules sheathed in an extension of the plasma membrane Nine doublets of microtubules are arranged in a ring, with two single microtubules in its center This arrangement”9+2” pattern found in nearly all eukaryotic flagella and motile cilia Basal body: the microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body which is structurally similar to a centriole Centrosome: microtubules grow out from this region that is often located near the nucleus Centrioles: each composed of nine sets of triplet microtubules arranged in a ring within the centrosome “9+0” pattern Dyeins: how flagella or cilia move; bending involves these large motor proteins that are attached along each outer microtubule doublet Typical dyein proteins each have two “feet” that “walk” along the microtubule of the adjacent doublet, using ATP for energy The outer doublets and the two central microtubules are held together by flexible crosslinking proteins and the walking movement is coordinated so that it happens on one side of the circle at a time 2) Intermediate Filaments: Intermediate filaments are intermediate in size compared to microtubules and microfilaments Intermediate filaments are only found in the cells of some animals including vertebrates Specialized for bearing tension Each type is constructed from a particular molecular subunit belonging to a family of proteins whose members include the keratins Even after cells die, intermediate filament networks often persist Intermediate filaments are especially sturdy and that they play an important role in reinforcing the shape of a cell and fixing the position of certain organelles Other intermediate filaments make up the nuclear lamina, which lines the interior of the nuclear envelope By supporting a cell’s shape, intermediate filaments help the cell carry out its specific function They are found in skin cells in the collagen in skin cells They are solid in the center Found in myosin which are muscle cells; they give a lot of strength to the muscles 3) Microfilaments: Thin solid rods Also called actin filaments because they are built from molecules of actin Actin: a globular protein Microfilaments are twisted double chains of actin subunits Can form structural networks when certain proteins bind along the side of such a filament and allow a new filament to extend as a branch The structural role of microfilaments in the cytoskeleton is to bear tension Microfilaments are well known for their role in cell motility Thousands of actin filaments and thicker filaments made of a protein called myosin interact to cause contraction of muscle cells Unicellular eukaryote Amoeba and some of our white blood cells, localized contractions brought about by actin and myosin are involved in the amoeboid movement of the cells Pseudopodia: cell crawls along a surface by extending cellular extensions and moving toward them Cytoplasmic streaming: both actinmyosin interactions contribute to this circular flow of cytoplasm within cells Cell Junctions in Animal or Plant Cells: o Cell junctions are located between 2 cells o Four types of cell junctions: 1. Plasmodesmata (plant) 2. Tight Junctions (animal) 3. Desmosomes (animal) 4. Gap Junctions (animal) 1) Plasmodesmata: Found only in plant cells They are channels that connect plant cells together so that water and nutrients can pass between two cells Cytosol passing through the plasmodesmata joins the internal chemical environments of adjacent cells The plasma membranes of adjacent cells line the channel of each plasmodesma and thus are continuous 2) Tight Junctions: The plasma membranes of neighboring cells are very tightly pressed against each other They are bound together by specific proteins Tight junctions establish a barrier that prevents leakage of extracellular fluid across a layer of epithelial cells Ex. Gut tissue you do not want the fluid in the gut to leak between cells 3) Desmosomes: Function like rivets, fastening cells together into strong sheets Ex. attach muscle cells to each other in a muscle Ex. Skin cells they hold skin cells together to allow for tension and movement 4) Gap Junctions: Provide cytoplasmic channels from one cell to an adjacent cell and in this way are similar in their function to the plasmodesmata in plants They are necessary for communication between cells in many types of tissues, such as heart, muscle, and in animal embryos Ex. Cardiac tissue/musclehelps chemical and electrical signals pass between cells Chapter 7: Movement Across Plasma Membranes BE ABLE TO LABEL THE PLASMA MEMBRANE STRUCTURAL COMPONENTS IN THE FLUID MOSCAIC MODEL AND EXPLAIN THE FUNCTION OF THE PARTS A: glycolipid B: glycoprotein, integral membrane protein C: integral membrane protein D: phospholipid E: peripheral membrane protein F: carbohydrate receptor Fluid Mosaic Model: o Fluid mosaic model: the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids Phospholipids: o Lipids and proteins are the staple ingredients of membranes although carbohydrates are important to o Most abundant lipids in most membranes are phospholipids o A phospholipid is amphipathic which means it has both a hydrophobic region and a hydrophilic region o Phospholipid bilayer can exist as a stable boundary between two aqueous compartments because the molecular arrangement shelters the hydrophobic tails of phospholipids from water while exposing the hydrophilic heads to water o This molecular orientation maximizes the contact of hydrophilic regions of proteins with water in the cytosol and extracellular fluid while providing their hydrophobic parts with a nonaqueous environment o A membrane is held together primarily by hydrophobic interactions which are much weaker than covalent bonds Fluidity: o A membrane remains fluid as temperature decreases until the phospholipids settle into a closely packed arrangement and the membrane solidifies o Temperature at which a membrane solidifies depends on the types of lipids it is made of o Membrane remains fluid to a lower temperature if it is rich in phospholipids with unsaturated hydrocarbon tails o Kinks in the tails due to double bonds, make unsaturated hydrocarbons tails not pack as closely together therefore making the membrane more fluid o The steroid cholesterol gets in between phospholipid molecules in the plasma membranes of animal cells causing different effects on plasma membrane’s fluidity Ex. Hibernating animals have the most cholesterol rich membranes o Temperature also influences fluidityincreasing temperatures causes fluidity to increase o Fluidity of a membrane affects both its permeability and the ability of membrane proteins to move to where their function is needed Proteins: o The mosaic aspect of the fluid mosaic model is that the membrane is a collage of different proteins often clustered together in groups embedded in the fluid matrix of the lipid bilayer o Phospholipids form the main fabric of the membrane, but proteins determine most of the membrane’s functions o Different types of cells contain different sets of membrane proteins, and the various membranes within a cell each have a unique collection of proteins o Two major types of membrane proteins: 1. Integral proteins: Penetrate the hydrophobic interior of the lipid bilayer Majority are transmembrane proteins: which span the membrane Some only extend partway into the hydrophobic interior Hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids Hydrophilic parts of the molecule are exposed to the aqueous solutions on either side of the membrane Some proteins also have one or more hydrophilic substances Some have channels that allow stuff to pass through the membrane Aquaporin protein: allows water to pass through the channel some integral membrane proteins are actually “carrier proteins” that move ions or large molecules into the cell some proteins are actual receptors themselves which means they receive chemical signals some proteins function as enzymes 2. Peripheral proteins: Not embedded in the lipid bilayer They are appendages loosely bound to the surface of the membrane, often to exposed parts of integral proteins Some membrane proteins are held in place by attachment to the cytoskeleton o Six major functions performed by proteins of the plasma membrane: 1. Transport 2. Enzyme 3. Cell surface receptor 4. cell surface identity marker 5. cell adhesion 6. attachment to the cytoskeleton o Cells recognize other cells by binding to molecules often containing carbohydrates on the extracellular surface of the plasma membrane they are like carbohydrate receptors o Glycolipids: carbohydrates covalently bonded to lipids membrane carbohydrates are usually short, branched chains of fewer than 15 sugar units o Glycoproteins: carbohydrates covalently bonded to proteins Ways that Molecules Move Across Membranes: o The ability to regulate transport across cellular boundaries, a function essential to the cell’s existence o The fluid mosaic model helps explain how membranes regulate the cell’s molecular traffic o A steady traffic of small molecules and ions move across the plasma membrane in both directions o Cell membranes are selectively permeable and substances do not cross the barrier indiscriminately o Nonpolar molecules are hydrophobic and can therefore dissolve in the lipid bilayer of the membrane and cross it easily, without the aid of membrane proteins o The hydrophobic interior of the membrane impedes direct passage through the membrane of ions and polar molecules which are hydrophilic o Proteins built into the membrane play key roles in regulating transport o Transport proteins: these hydrophilic substances can avoid contact with the lipid bilayrer by passing through these proteins that span through the membrane o Channel proteins: function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane o Carrier proteins: hold onto their passengers and change shape in a way that shuttles them across the membrane o Transport protein is specific for the substance it movesit allows only a certain substance to cross the membrane Passive Transport: o Diffusion: the movement of particles of any substance so that they spread out into the available space o In diffusion, a substance will diffuse from where it is more concentrated to where it is less concentrated o Diffusion molecules tend to go down a gradient because it is natural when means there is no energy required o The concentration gradient is the region along with the density of a chemical substances increases or decreases o Much of the traffic across cell membranes occurs by diffusion o When a substance is more concentrated on one side of a membrane than on the other, there is a tendency for the substance to diffuse across the membrane down its concentration gradient o Passive transport: diffusion of a substance across a biological membrane because the cell does not have to expend energy to make it happen o If there is no net movement between two substances, then equilibrium has been reached Osmosis: o The solution with a higher solute concentration has a lower free water concentration o Water diffuses across the membrane from the region of higher free water concentration (lower solute concentration) to that of lower free water concentration (higher solute concentration) until the solute concentrations on both sides of the membrane are more nearly equal o Osmosis: diffusion of free water across a selectively permeable membrane o Movement of water across cell membranes and the balance of water between the cell and its environment are crucial to organisms o Tonicity: the ability of a surrounding solution to cause a cell to gain or lose water o Tonicity of a solution depends in part on its concentration of solutes that cannot cross the membrane relative to that inside the cell o Higher concentration of nonpenetrating solutes in the surrounding solution, water will tend to leave the cell and vice versa o Solution: made up of 2 componentsthe solute and the solvent o Solute: molecule in lower concentration o Solvent: molecule in lower concentration Ex. Solute would be the salt and solvent would be the water in making salt water o Hypertonic: more solute than water o Hypotonic: more water than solute o Osmoregulation: the control of solute concentrations and water balance for organisms that lack rigid cell walls in hypertonic or hypotonic environments o Isotonic: same amount of solute and water o Hypertonic solutions have a higher “osmotic potential” which means it has a greater tendency to take on water o Water potential: means the solution that has the lowest amount of solvent which one has more water molecules Ex. Red Blood Cells: If you put RBC in an isotonic solution, there should no change ( Ex. About 0.9% saline ) If you put RBC in a hypertonic solution, the cell would shrivel up or crenates ( Ex. 5% NaCl ) If you put RBC in a hypotonic solution, water would go into RBC until it gets too big and then it would burst ( Ex. Distilled, deionized water ) Ex. Plant Cells: Plant cells have rigid cellulose walls If you put a plant cell in a hypertonic solution, it will shrink If you put a plant cell in a hypotonic solution, it will create pressure between the plasma membrane and the cell wall Turgor pressure: when the inelastic cell wall will expand only so much before it exerts a back pressure on the cell Turgid: the cell is very firm which means the plant is healthy If you put a plant cell in an isotonic solution, it will wilt because there is no turgor pressure Flaccid: there is no net tendency for water to enter the cell therefore it becomes limp meaning a sickly plant If a plant cell or an animal cell loses water to its surroundings, it shrinks When plant cells shrivel, its plasma membrane pulls away from the cell wall at multiple places Plasmolysis: causes the plant to wilt and can lead to plant death Many plant cells have to have a way to control the amount of water Ex. Tetrahymena o Eukayotic cell o Found in freshwater o Can handle hypotonic solution for a little while but not for long and eventually it will explode Ex. Salting meat o Inhibiting bacteria o Salt creates a hypertonic environment Ex. Preserves o Fruit and sugar o Sugar is the hypertonic environment Types of Transports that Use Carrier Proteins: 1) Facilitated Diffusion: Many polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane Goes down the gradient therefore does not require an input in energy This is a type of passive diffusion because it goes with the gradient Ex. Moving glucose into most cells It is the ring form of glucose Glucose binds to the carrier protein and is taken into the cell and released A phosphate is added in most cells to the glucose once it enters the cell Glucose then becomes very charged and changes from pure glucose to glucose with a phosphate attached to carbon # 6 Ex. Moving cysteine out of kidneys o There are two types of transport proteins: channel proteins and carrier proteins o Channel proteins simply provide corridors that allow specific molecules or ions to cross the membrane o Ion channels: channel proteins that transport ions o Gated channels: ion channels function as gated channels which open or close in response to a stimulus o Other gated channels open or close when a specific substance other than the one to be transported binds to the channel o Carrier proteins: intramembranous proteins that extend through the plasma membrane; seem to undergo a subtle change in shape that somehow translocates the solutebinding site across the membrane o Carrier proteins involved in facilitated diffusion result in the net movement of a substance down its concentration gradient 2) Active Transport: Moves molecules, ions, etc. up the gradientit moves it against the gradient This means that energy is required Transport proteins that move solutes against their concentration gradients are all carrier proteins rather than channel proteins ATP supplies the energy for most active transport Ex. Moving glucose from the blood into liver cells Glucose concentration is high in the liver cells and low concentration in the blood It requires ATP to go from low concentration to high concentration Ex. SodiumPotassium pump Extremely important for cells All cells have to be able to pump sodium and potassium in and out of the cell to maintain the ratio of 2 potassiums (K ) inside to 3 sodiums (Na ) outside The sodiumpotassium pump keeps your membranes polarized The pump is an intramembranous protein Has binding sites for sodium and potassium ions Positive charge on the outside which makes the inside have a negative charge When a nerve impulse arrives at a cell, the membrane depolarizes and therefore the ions leak in and out However, the pumps kick in and restore polarization by restoring the 2 potassium to 3 sodium ratio They extend ATP in order to accomplish this task 3) CoTransport: Movement of an ion across the plasma membrane will drive the transport of some other molecules Ex. Moving protons and glucose into a cell As the proton is going down the gradient, glucose tags along and binds to the carrier protein too and follows the proton inside the cell Types of Endocytosis: o Endocytosis: the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane 1) Pinocytosis: Used for small dissolved solutes (small particles) Plasma membrane invaginates slightly where the particles are It then pinches off and moves the particles inside the cell by placing them inside a vacuole 2) Phagocytosis: Used for larger particles ex. bacterium The plasma membrane invaginates around the bacterium Then it pinches off and encloses the bacterium into a vacuole Lysosome will then come over and fuse with it and help kill the bacterium by digesting it 3) Receptormediatied endocytosis: Highly specific Ex. Removal of LDL (which stands for lowdensity lipoprotein”bad cholesterol”) from the blood On the surface of cells are receptors for LDL that bind only with LDL LDL binds to the receptors Where the receptors are is a fuzzy coat called the clathrin coat The membrane then invaginates and the clathrin coat is still around it therefore created what is called a coated pit Then the coated pit pinches off continuing to be covered and this vesicle is called a coated vesicle The receptors then empty themselves and are added back onto the surface of the membrane The number of LDL receptors a person has is genetically determined o Exocytosis: the cell secretes molecules by the fusion of vesicles with the plasma membrane; the contents of the vesicle spill out of the cell therefore exiting it Chapter 8: Introduction to Metabolism o Metabolism: how you route molecules o Exergonic Reactions: occurs spontaneously because they release energy; ∆G must be negative which means the reactants have more energy than the products; these tend to be oxidations o Endergonic reactions: do not occur spontaneously because they require energy to happen; ∆G is positive which means that the products that more energy than the reactants o Oxidation: release energy or release hydrogen and replace it often with oxygen o Reduction: requires energyadding hydrogen Ex. Methane is the most reduced carbon that you can makeit is a very saturated hydrocarbon Methane has a lot of eregy in it because of the CH bonds To oxidize methane we take off a H and add a OH group and create methanol Removing another H by oxidizing further creates methanol or formaldehyde Oxidizing further creates methanoic acid or formic acid Oxidizing further which is the fully oxidized state creates CO 2 Each of these reactions are exergonic Oxidizing is taking off H and replacing with oxygen Working backwards from CO to me2hane are reductions because you are adding H o Reductions are endergonic o Exergonic is catabolism in a cell o Oxidation and reduction reactions occur together o This is cell respiration what you do with your food in your body C 6 12 +66 O 26 CO + 62H O + 2nergy which is negative o You want the most reduced molecules for energy o Glucose ends up as CO whic2 is an oxidation o Digesting food for energy is oxidation o The oxygen you inhale ends up as H O whic2 is a reduction o Energy is produced in all of this therefore ∆G is negative o Plant respiration 6 CO 2 6 H O2 C H O6 126 6 2 o Plants take in CO an2 convert to C H O 6(g12c6se) which is a reduction o Plants make water and give off O which is an oxidation 2 o Sun is the energy plants use How to Make Endergonic Reactions Occur: o We make them occur by using coupled reactions (2 reactions) Examples 1) Use ATP (chemical energy): ATP ADP + Pi ∆G = negative When ATP loses a phosphate group it becomes ADP and an inorganic phosphate Ex. Glutamic acid is an amino acid and you eat it by adding an ammonia group to it making it glutamine Glutamic Acid + N2 Glutamine This is an endergonic reaction so it will never happen How your body makes it happen is adding ATP to the reaction ( add energy = ATP ) Glutamic Acid + N2 + ATP Glutamine + ADP + Pi Whole reaction will have a negative ∆G therefore it will occur 2) CoEnzymes: not related to enzymes at all these work different than real enzymes coenzymes are electron donors and electron acceptors coenzymes are not proteins they all have a vitamin portion they have been oxidized and reduced states Reduced form NADH and FADH e2 ctron donors because they can give away the hydrogen Oxidized form NAD and FAD electron acceptors because they can take on a hydrogen this reaction occurs in certain types of yeast cells (the ones used in the alcohol industry) Acetaldehyde or ethanol + NADH + H ethanol + NAD + NADH often travels with an extra H + Yeast uses NADH to reduce the carbon double bonded to oxygen to make ethanol This is a coupled reaction meaning both a reduction and an oxidation happens Enzymes: o Major function is they speed up reactions by lowering the activation energy o Like the spark plug in the reaction o Most are proteins o Many of the names end in “ase” Ex. Lipase, maltase, lactase o Bind to reactants in a reaction and they weaken bonds Active site is where the substrate will bind Enzymes are highlyspecific On some enzymes, there is an allosteric site: where something else binds along with the substrate to activate the enzyme Ex. Sucrose glucose + fructose o Sucrose doesn’t need an enzyme to be broken down but it happens to slow in your body without using on enzyme Sucrose add water and sucrose create glucose + fructose o Sucrose binding to active site o an enzyme substrate complex where the two molecules are held against the enzyme to create pressure on the glycosidic linkages so that they break apart o This reaction is catabolism Things that Influence the Action of Enzymes: o Enzymes work best at about 37ºC (body temperature) Ex. Tyrosinase: production of dark pigments in cats Siamese cats have distinctive markings in the feet and ears This enzyme prefers cooler temperatures o Most enzymes prefer a range of pH from 68 except for the stomach which would be about pH 12 o Some enzymes need cofactors in order to be active + + Examples of some cofactors could be some ions ( Mg , Zn ) or coenzymes These cofactors will bind to the allosteric site Inhibitors of Enzymes: o 2 types of inhibitors of enzymes: 1. Competitive: compete for the active site therefore it will look like the substrate 2. Noncompetitive: not competing for the active site but they may bind to the active site causing the enzyme not to be able to react o Some inhibitors are reversible o Other inhibitors are irreversible Ex. Nerve gas: can’t be unbound Ex. Penicillin for bacteria
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