Bio 111 Exam 2 Notes
Bio 111 Exam 2 Notes Biology 111
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This 17 page Class Notes was uploaded by Mallori Wisuri on Thursday February 18, 2016. The Class Notes belongs to Biology 111 at Ball State University taught by Dr. Metzler in Winter 2016. Since its upload, it has received 35 views.
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Date Created: 02/18/16
Bio 111 Exam 2 Ch. 6 Notes 2/02/16 • Organization of the Cell -‐Microscopy (online video) -‐Experimental Techniques (online video) -‐Structures • Cell Theory: 1. Cells are the smallest living unit of organization 2. All cells come from other cells through process of cell division LC: All cells have a plasma membrane? TRUE; if you are a cell plasma membrane separates you from everything around you. All plant, prokaryotes and eukaryotes have a plasma membrane. • Shared Features of Cells o Plasma Membrane o Chromosomes: genetic material -‐Prokaryotes (circle) -‐Eukaryotes (linear) o Ribosomes: make proteins o Cytosol: goo gel component in the cell o Small: size o Dynamic • Two types of cells Eukaryotes: -‐Animal cell: blob like structure because lack of cell wall, will have vacuole but will not have a central vacuole. -‐Plant cell: have cell wall give them a defined structure, chloroplast (green) which perform photosynthesis and central vacuole which takes up 90% of the cell, plants have mitochondria. • Function Relates to Size and Shape -‐Specific structure that relates directly to the function it performs -‐Examples: Neuron: long connections with other cells Macrophage: extensions to grab bad guys that will make you sick. LC: Proteins are bigger then cells? FALSE; Proteins are much smaller then cells and animal cells are built of lots of proteins. • Surface Area to Volume -‐Allows them to have maximum ability to exchange material -‐Bring in nutrients and expel waste material -‐If cell gets too big it won’t be able to exchange material fast enough to survive -‐Why cells stay small on purpose -‐Cells work hard to maximize surface area and is why they don’t have a smooth surface because this limits surface area. -‐Example: Small intestines Tissue layer goes up and down in structures called villi. Then look at 1 individual cell have microvilli. This allows for maximum nutrient absorbance when food passes by it. • Prokaryotes -‐Smaller than eukaryotes (harder to find on microscopes) -‐No membrane bound organelles -‐Have a cell wall structure; single-‐celled -‐Ribosomes are smaller in size compared to eukaryotes -‐Genetic material located in nucleoid • Eukaryotes -‐Larger in size than prokaryotes -‐Contain membrane bound organelles -‐Highly organized; put everything into compartments (organelles) -‐Larger ribosomes compared to prokaryotes • Organelles! o Nucleus -‐Most prominent organelles -‐Near the center of the cell Plant cell the nucleus is shoved to side Animal cell in middle -‐Control center of cell structure that houses DNA -‐DNA controls activity that goes on inside of the cell -‐Double membrane: layer 1 and 2; called the Nuclear envelope -‐Nuclear pores are studded on the nuclear envelope. Pores made up of proteins to allow pore to open and close -‐Regulation of what goes in and out -‐Nucleolus: darker staining region in nucleus; ribosomes are created and no envelope surround it -‐Chromatin: form of DNA + proteins called histones that help condense DNA (bowl of spaghetti) -‐Nuclear lamina: located directly underneath nuclear envelope (Put rebar in concert); it’s a support structure that creates the circle that is the nucleus (On DNA side). -‐Example: Scientist who try to clone things and remove nucleus from a cell and put it in another cell. Shock the cell then cell starts to divide and end up with a clone. o Ribosomes -‐Don’t have a membrane and is why they are found in prokaryotes -‐Job is to make proteins -‐Composed of 2 subunit (large and small) -‐Made up of RNA molecules -‐2 varities: 1. Bound ribosomes: attach to the Endoplasmic Reticulum. Make proteins that are going to leave the cell or sit in membrane somewhere. 2. Free ribosomes: floating around cytosol of cell. Make proteins that are going to be floating around in cytosol. -‐Ex. Tadpoles 2/04/16 LC: Advantage of light microscopy over electron microscopy. Light microscope can watch dynamic movement, which you can’t in electron microscope because that organism/cell is dead. LC: Image shown was with what type of microscopy (pollen grain). SEM because its 3D and looking out the outside (surface). LC: In microscopy staining improves what? LC: What would be the outcome f the nucleolus was disrupted and no ribosomes Protein mediated LC: What would happen is lysosomes wouldn’t function? LC: Why do plants wilt? Central vacuole emptied out because you did not water the plant. o Endomembrane System -‐Has ability to move proteins to the interior of cell or to be secreted from the cell. -‐Play a role in metabolism to synthesis lipid and move lipids around. -‐Parts can help detoxify substances COMPONENTS INCLUDE of Endomembrane System: • Nuclear envelope • Endoplasmic Reticulum: All membranes of ER are connected to one another. Variation(percentages) in quantity of ER present; all cells will have both types. 2 types: -‐Rough ER: bumpy because studded with bound ribosomes on its surface. Flattened out. Involved in protein production. Make glycoproteins which is a protein with carbohydrate added to it. -‐Smooth ER: no ribosomes on its surface. Tubular in appearance. Importance in synthesis of lipids, help to detoxify drugs, storage in calcium ions (muscle contraction). Ex. Ovaries/Testis, Liver, skeletal muscle cells o Importance of the ER -‐Clumping/Tangling of proteins leading to diseases such as Alzheimers. Brain of individual with this disease will slowly shrink. • Golgi: reads the tags on proteins and determines where they are suppose to go in the cell. -‐Made up of flattened membranes(cisternae) that are not connected to each other. -‐Specific sides Cis side: receives proteins from the ER. Proteins come in vesicles that fuse with golgi membrane stack. Medial side: middle Trans side: faces out toward plasma membrane and where proteins exit the Golgi. Proteins exit in vesicles. -‐Haley-‐Haley disease: cause skin irritation disease is related to a golgi defect. • Lysosomes: Garbage disposal of your cell. Can destroy any biomolecule! -‐Membrane sac spherical in shape -‐Over 40 different enzymes inside lysosome -‐It’s job is to break things down -‐pH inside of lysosome is slightly acidic(pH 5). Enzymes in lysosomes are only active in pH of 5. IMPORTANT because if they were to get out of lysosome they would be able to destroy everything in/out of cell. This is a protective mechanism! -‐40 different genetic disorders related to lysosomes o Phagocytosis: cell eating -‐How a lot of protist get their food. -‐Food vacuoles fuse with lysosome and this is how food gets broken down. o Autophagy: self-‐eating -‐Lysosomes used to destroy damaged organelles • Vacuoles: membrane bound sac. -‐Several different types. Plants cells 1. Central vacuole: storage of mostly water, but also can store pigments or wastes. Watering the plant generate turgor pressure which exerts against the cell was and is why plants perks up. Animal Cells 2. Food vacuole: same concept in phagocytosis 3. Contractile vacuole: fills up with water then contracts and squeezes water out of cell in protists. This helps them get ride of that extra water from their aquatic environment so they don’t explode. Helps the organism maintain its osmotic balance. • Plasma membrane o Energy Conversion -‐Aerobic respiration: Mitochondria: location for aerobic respiration to convert energy into ATP. *Have a double membrane; inner membrane folded and called cristae. Increase SA for aerobic respiration to take place. *Have own DNA; dependent on DNA in nucleolus still *Reproduce on their own *Posses their own ribosomes -‐Photosynthesis: Chloroplast: light is converted into chemical energy, which is converted to make food. Plants make all food and oxygen. *Have a double membrane; inner membrane folded and called thylakoids. Increase SA for steps of photosynthesis. *Have own DNA; dependent on DNA in nucleolus still *Reproduce on their own *Posses their own ribosomes o Endosymbiosis Theory Mitochondria and chloroplast came from prokaryotic cells that eukaryotic cell engulfed and eventually lost their function to be on their own. (JEOPARDY GAME) http://www.superteachertools.us/jeopardyx/jeopardy-‐review-‐ game.php?gamefile=1482820#.Vf9bzXt4hpl Ch. 6 Video Lecture Notes 2/04/16 Microscopy • Magnify: making the image bigger • Resolution: the ability of micro to distinguish between two separate points. • Light Microscopes: use different types of light microscopes to manipulate the image you want. 1. Brightfield: are scopes where you are just shining light Want to see cells better well want to stain the cells to provide contrast to see the shape of the cell, nucleus, membrane etc. (Brightfield stained specimen) 2. Confocal: light microscopes are specific wave of lights that can excite fluorescent dyes or give off color. -‐Hooked up to a computer 3. Fluorescent: stain specimen with dye so when you hit it with a specific wavelength of light it will give off a color. -‐Very specifically stain individual components of the cell. o Light Microscopy: -‐Big pro lets us look at living organisms; you can see them moving, functioning, see things inside of them moving. -‐Use stains/dyes -‐Negative is that detail is limited because most microscopes will max out magnification at 1000X. Maximum resolution is 0.2microns. -‐Example: amoebae o Electron Microscopy: shooting a beam of electrons at specimen not a beam of light 1. Scanning Electron Microscopy (SEM) -‐Use them to look at fine surface detail of organisms -‐Beams bounce off surface of specimen -‐Kill the specimen and coat it with thin layer of golds -‐3D image -‐Example: amoebae looks differently and can see its covered with cilia 2. Transmission Electron Microscopy (TEM) -‐Use them to look at the very fine inside detail of organisms -‐Beams goes through the specimen -‐Organism are cut it very thin sections and then coated heavy metal atoms -‐Kill the specimen o Cell Fractionation(animation on BB) -‐Technique used to purify organelles -‐Take a big tube of cells that you need to rupture called homogenization -‐Rupturing cell membrane and releasing all interior contents of cell -‐Next, you put the tube into a centrifuge -‐Different parts of cell have different densities so by spinning homogenized cells you can separate out different components/fractions of the cell you want to study -‐Pellet and supernatant -‐Used for experiments to study function of specific organelles Ch. 6 Organization of the Cell 2/09/16 LC: Do prokaryotes perform cellular respiration? Yes, they have to harvest energy. Use cellular membrane to perform these types of reactions. LC: Did the protein go through entire the Entire Membrane system based off the radioactive data? -‐No, but it was in the ER. Started in the ER, and then went to the Golgi, last place it went to the cell membrane. Got stuck in the membrane but never left the cell. -‐Proteins in the membrane don’t work properly in cystic fibrosis patients. • Peroxisome: look very similar to lysosome or small vacuole. It’s a little membranous sac in the cytoplasm. -‐Doesn’t have ability to break down as much as a lysosome -‐Can break down fatty acids and hydrogen peroxide. -‐Helps to get rid of membrane components and hydrogen peroxide generated because of aerobic respiration pathway -‐Catalase destroys the hydrogen peroxide (bubbling when put hydrogen peroxide in a cut on skin) -‐Defective enzyme causes X-‐linked adrenoleukodystrophy (X-‐ALD) -‐Glyoxysomes special versions found in plant cells. LC: Given organelle and match the appropriate function of the cell. -‐Macrophage-‐Lysosome -‐Algae phtotoautotrophs–Chloroplast -‐Cardiac muscles need energy-‐Mitochondria -‐Plasma cells secrete antibodies (proteins)-‐Rough ER -‐Epididymis secrete glycoproteins-‐Golgi • Cytoskeleton: 3 components. They all support the basic structure of the cell. Very dynamic structures; constantly breakdown and build them back up. 1. Microtubules: movement of cell and components inside cell -‐Largest component -‐Hollow tube (looks like straw) -‐Made of protein called tubulin -‐Have a plus end and a minus end. Both ends tubulin can come on and off (extend or shorten microtubule). Most occurs at the plus end while the minus end is anchored toward the center of the cell. -‐Several Roles: *Pull chromosomes apart during mitosis and meiosis. Spindle fiber is built from microtubule. *Serve as the highway of your cell. Motor proteins drag vesicles along microtubules *Anchor points for organelles. *Major component of cilia and flagella to allow entire cell to move around o Centrosome: microtubule organizing center in animal cells(MTOC) -‐Inside are two centrioles are made up of microtubules. -‐Oriented at right angles to one another. -‐Plants do not have these o Cilia and Flagella: extra cellular projections; important for movement. -‐9+2 arrangement of microtubules. -‐Paris of microtubules: 9 around the outside and 2 in the middle -‐Flagella: acts like a motor and spins in corkscrew manner to propel cell(looks to us like a whip like motion) -‐Cilia: function like ore on a row boat; flip back and forth. o Role of Dynein -‐Motor protein help to carry proteins across the cell -‐Play a role inside the cilia and flagella Ex. Dynein -‐Set of microtubules connected by cross linking proteins, cause the whole thing to bend (cilia and flagella to move). LC: Drug effects microtubules, move chromosomes in cell divisions of cancer cells. 2. Microfilaments: movement of cell and components inside cell -‐Form cleavage furrow -‐Made of protein called actin -‐Strands twisted around one another (2 chains of actin) -‐Found right underneath plasma membrane Roles: -‐Muscle contraction -‐Protist use microfilaments to help them move around via amoeboid movement by extending components of cytoplasm. -‐Cytoplasmic streaming is seen in plant cells where they actively circulate components in cytoplasm. 3. Intermediate filaments: important in cell structure. -‐No role in movement -‐Give strength and stability in cell -‐Not dynamic (You don’t build up them up or break down them down) -‐Made of many different types of proteins (ex. keratin) -‐Like a big wire cable holding up a suspension bridge -‐ALS is related to defect in intermediate filament. Skin has no strength or stability • Extracellular Components o Cell Wall -‐Most prokaryotes and plant cells have a cell wall -‐In single celled-‐organisms the major function is to be protective -‐In plant cells the cell wall is important structurally o Extracellular Matrix (ECM): animal cells build; secrete it to outside of the cell. 4 main components make this up. 1. Collagen: protein, big fibrous protein runs parallel to surface of cell. Provides flexibility/stability. They fill up the gaps between the cells. 2. Proteoglycans: protein and carbohydrate combination. Provide collagen something to embed itself in. 3. Fibronectin: connects collagen fibers to surface of the cell. 4. Integrins: sitting in the cell membrane they are the anchor point for fibronectin. Important in cell communication. 2/11/16 Ch. 6 continued • Cell Connections (Intracellular junctions-‐4 types): cells means of communication and or holding the cell together. o Communication (2 types) -‐Plasmodesmata: allow for small molecules and ions to directly pass from one cell to another. Cells communication in a rapid manner. Is a hole in the cell wall directly connected between 2 plant cells. -‐Gap Junction: allow for small molecules and ions to directly pass from one cell to another. Cells communication in a rapid manner. It is not a direct connection of membrane. It is produced by several proteins called connexins and they insert them selves into the membrane. They can open and close. Ex. Heart cells that beat together o Connections (2 types) used in creating tissue layer; only found in animal cells. -‐Desmosomes: directly connected to intermediate filament. Do not have capability to seal area off. Ex. Skin to create strong flexible tissue layer -‐Tight junctions: hold cells together so tightly they have ability to completely seal an area off; no molecules can pass. Ex. Blood brain barrier and small intestine in epithelia layer. Ch. 7 Membranes Characteristics and Transport • Phospholipid characteristics: -‐Amphopathic: hydrophilic and hydrophobic qualities -‐Form a lipid bilayers when put in water; this is the backbone of membrane -‐Has a uniform shape overall • Fluid Mosaic Model: -‐Membrane has fluid characteristics; everything in the membrane has capability to move around -‐Mosaic because it’s made up of more then one thing. -‐In membrane have proteins, cholesterol, carbohydrate components. Carbohydrate always added to the protein or phospholipid. • Characteristic that membrane possess o Fluidity: cells work hard to maintain optimal fluidity. Don’t want it to become gel or move around too much. -‐Phospholipids perform lateral movement (moving right to left) on the same leaflet/side. -‐Phospholipid perform flip flop where they flip from one side to the other side. This rarely happens; normally when a cell is about to die. -‐This movement depends on the type of lipids that are present. *Saturated(solid) less fluid membrane because tails interact more through Van Der Waals. *Unsaturated(liquid) more fluid because the tails kink. -‐Insert more cholesterol molecules in the membrane. Serves as a buffer molecule. Inserts itself in between fatty acids tails. -‐The membrane will not rupture because of the fluidity capability that allows the membrane to fill in the gaps when being pulled, poked, etc. LC: Least viscous (most fluid) to most viscous (most solid). Mostly unsaturated(kink tails)-‐-‐-‐partial amount of unsaturated with some saturated-‐-‐-‐-‐-‐all saturated(no kink tails) o Membrane Proteins (Mosaic) Two types of proteins: 1. Integral proteins: tightly connected to the membrane -‐Classified as a transmembrane because it spans the entire membrane. -‐Inserted into the membrane and to get the protein out you would have to destroy the entire membrane. 2. Peripheral proteins: it has a lose connection to cytoplasmic side. -‐Don’t have to destroy membrane to free those proteins. -‐Carbohydrates can be added to proteins and lipids (glycoprotein and glycolipid) LC: What amino acid would most likely present on the transmembrane domain of integral membrane protein. -‐A hydrophobic amino acid like valine. -‐What part of membrane is transmembrane siting it, its sitting in the hydrophobic part. o Membrane Protein Function: 1. Transport(FOCUS ON) 2. Enzymatic activity 3. Signal transduction 4. Cell-‐cell recognition 5. Intercellular joining 6. Attachment to cytoskeleton and extracellular matrix o Asymmetrical: Extracellular and Intracellular leaflets look different from one another. Because they contain different proteins. Which can causes different sides to have different functions because of the proteins presented there. o Selective Permeability -‐Very small you can easily pass through the membrane -‐Lipid soluble and handle hydrophobic core of the membrane -‐Charged you will need assistance -‐Big like amino acid, small sugars you will need assistance LC: Which of the following molecules will diffuse most quickly across a lipid bilayer membrane? -‐Oxygen, yes! Charged molecules no Glucose is a big sugar molecule Water moves into cell in a different mechanism o Diffusion -‐Does not require a membrane -‐No net energy because it is a passive process -‐Energy comes from the random movement of molecule -‐Net movement down a concentration gradient (high concentration to low concentration) Move to equilibrium -‐Vast majority move down but some high because of that random movement -‐Concentration of 1 molecule does not effect the concentration of another molecule -‐No net flow means they are not moving just moving at equal rates 2/16/16 Ch. 7 continued o Osmosis: movement of water across a membrane. -‐Special case of diffusion movement of water molecules -‐No net energy because it is a passive process -‐High water concentration to low water concentration -‐Important in animal cells because if these cells don’t balance water in and out of the cell it can shrivel up or explode. -‐Terms need to know/understand. These terms are describing solute concentration! You are paying attention to the water movement. *Isotonic: equal solute concentration between cell and an environment is balanced. This is the preferred state by animal cell, but not plant cell because it draw water out of central vacuole. Water moves in and out of cell at an equal rate. *Hypertonic: high solute concentration; therefore water concentration is low. Water is going to leave the cell and the cell will shrivel up. *Hypotonic: low solute concentration; therefore water concentration is high. Water is going to enter the cell and the cell will lyse/explode. Plant cells prefer this situation because their central vacuole will be at maximum and turgor pressure will form. LC: -‐Cell 1: in a hypotonic environment less solute outside the cell so water will go into the cell. -‐Cell 2: in a hypertonic environment more solute outside the cell so water will go out of the cell. Group Work(Real life osmosis examples): -‐Netty pot: this is a hypertonic solution to your cells. It draws the water out of the cells and your nasal passage opens up and you can breathe again! -‐Contact solution in tap water: this is a hypotonic solution. Water will rush into the cells on surface of lens(eye) and thus rupturing them. o Osmoregulation: single celled organisms who live in an aquatic (hypotonic) environment. -‐Have a contractile vacuole to maintain osmotic balance. They have to be able to pump water out. -‐They are not isotonic to their environment. Water is constantly coming across their membrane. LC: Marine algae cell taken from saltwater environment and put into a freshwater environment, what will algae cell immediately do? -‐Absorb water being placed into a hypotonic environment volume of cell will expand. o Facilitated Diffusion -‐Passive process -‐Molecules that are too big, charged, can’t deal with hydrophobic portion of cell membrane will use this process. -‐Diffusion occurs with the help of a transport protein. This protein is a safe tunnel to get through the membrane. -‐2 varieties: *Channel Proteins Ex. Gated ion channel, aquaporin *Carrier Proteins: solute being transported interacts more with the carrier protein and a shape change occurs. Ex. Glucose transporters o Active transport -‐Molecules are being moved against their concentration gradient, which is moving it away from equilibrium. -‐Always requires the use of a transport protein -‐Cellular energy needed in form of ATP; break ATP molecule down -‐Ex. Sodium Potassium Pump: brings two K in and 3 Na out Ion pumps create membrane potential. Creating BOTH a charge and concentration gradient difference. Called an electrochemical gradient! Cell uses this to do work. o Cotransport: cell purposefully sets up a gradient -‐Active transport -‐Coupling active transport and diffusion -‐Manipulate he situation to get what they want • How do we move big stuff (ALL are active transport) o Exocytosis: way to remove things from the cell -‐Material being removed is placed into a vesicle. This vesicle moves along cytoskeleton (microtubules) and once it gets up to plasma membrane then pits its contents out. -‐This does not cause the cell to get bigger; surface area to volume ratio. o Endocytosis: way to bring things into the cell. -‐3 different ways! *Phagocytosis: cell eating; grab insoluble particles like food or bacteria. Bring it inside in a vacuole type structure and degrades the contents. *Pinocytosis: cellular drinking; bringing dissolved material inside. Important in the small intestines and how we absorb nutrients. *Receptor-‐Mediated Endocytosis: involves a receptor/ligand interaction. -‐Way to uptake cholesterol and in the immune system -‐Very specific Ch. 11 Cell Communication 1/18/2016 • Purpose of cell signaling is to get cells or organism to make a response. • Types of signaling: 1. Direct contact: cells physically touch each other. These are cell junction like gap junctions(in animal cells) and plasmodesmata(in plant cells). 2. Distance : a few specific types. *Local signaling: response is local. -‐Paracrine signaling. Have a cell secrete signaling molecule usually protein there are cells close by and that signaling molecule tell those cells to do something. -‐Synapse: signal between neurons *Long distance: gets in circulatory system and the response could be organism wide. -‐Endocrine signaling: hormones get into the circulatory system and then this causes an effect far away from where it was originally generated. • Stages of Cell Signaling: 1. Reception: when cell receives the signal molecule. This involves a ligand binding to a receptor. Receptors can be located on the surface of the cell or inside cell. -‐Ligand and receptors are both proteins. -‐Interaction between ligand and receptor are very specific . Most receptors will only bind one ligand. This allows for a lot of control of this process. -‐This causes a shape change in the receptor. This shape change will allow the receptor to be activated and be able to move on to the next stage in cell signaling. 2. Transduction: transduce the signal, series of molecules that passes the signal along. Moves everything toward where we are going to get a response. -‐2 most frequent ways: *Phosphorylation cascade: keep adding a phosphorylation to the next guy in line or in the chain. Series of activation events and they activate the next guy and continued down the line. -‐Several proteins involved in the process. Their names will always involve kinases! -‐Occur frequently with tyrosine kinase receptors. *Second messengers: 1 messenger is ligand (signal molecule). Most common second messenger is cAMP. -‐Common with G proteins. -‐cAMP or ions t levels increase and activate another relay molecule -‐Second messenger passageways are shorter. 3. Response: cells going to make a response. The signal is telling the cell to do something. -‐2 types: *Nuclear: effector molecule goes inside the nucleus and interact with DNA. Effect protein synthesis up or shut it down. *Cytoplasmic: protein activity is affected. Increase or decrease its activity. • Type of Receptors: 1. G protein-‐coupled receptors: located in cell/plasma membrane -‐Largest group found in cells -‐G protein interacts -‐Receptor binds to the ligand. This causes a shape change, which then allows the receptor to bind to the G protein. The G protein then moves in the plasma membrane and moves to an enzyme in the membrane. This then activates the enzyme and reception is completed. -‐Huge in sensory cells/receptions 2. Tyrosine Kinase receptor: found in the plasma membrane. -‐Important in the growth of cells and immune system -‐Heavy target for cancer cell mutations -‐In their cytoplasmic tails there are several amino acids (Tyrosine). Kinase comes from the phosphorylation which means to add a phosphate group. -‐Signal molecule bind to each individual receptor, which causes receptors to form a dimer, thus activating them. -‐Phosphorylated each other tyrosine once activated. -‐Other proteins in cytoplasm that will interact with phosphorylated tyrosine and then the signal is passed. 3. Membrane receptors-‐Ion Channel: form of facilitated diffusion that helps to send a signal. -‐Chanel protein that also functions as a receptor. -‐Ligand binds to receptors, channel protein changes shape allowing the channel to open. -‐Ions can then move into the cells and thus lead to cellular response. -‐Ligands release and channel protein closes. LC: Which best describes a cell-‐signaling pathway. -‐Binding of a ligand on one side of a membrane that results in a change on the other side. Intracellular receptors-‐steroid hormone: lipid like molecules and can come across the membrane -‐Signal can be passed much more simply. -‐Receptor protein is located in the cytoplasm or nucleus. The ligand molecules come across the cell membrane and binds to the receptor. As a whole unit it interacts with DNA to cause a response. -‐By passes the transduction step! • Signal Amplification: means to increase the response from a few ligand molecules. -‐Allows the cell to make massive response even though it only binds a few signal molecules. • Specificity: cells make different kind of receptors and signal molecules. -‐Different cells act different transduction pathways based on proteins they possess -‐Receptor is the same but what happens inside the cell is different. There are different relay molecules. -‐Due to different cells expressing different genes. • Apoptosis: process of a programmed cell death. -‐Cell decides there is so much wrong with it -‐For infected, damaged or old cells. -‐Doesn’t harm other cells around it. -‐Ex. Sun burned skin cells -‐Signal for apoptosis can come from outside the cell or the own cell can do this as well. -‐Plays a role when developing embryonically. Ex. Fingers/toes -‐Abnormal signaling of cancer cells. They turn off apoptosis and cell can’t kill itself.
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