BIO 141 Exam 1 study guide
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This 14 page Study Guide was uploaded by Camryn McCabe on Saturday January 30, 2016. The Study Guide belongs to Biol 141 at a university taught by Janelle Malcos in Spring 2016. Since its upload, it has received 280 views.
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Date Created: 01/30/16
Bio 141 exam 1 Lecture 1 Homeostasis- how the body maintains a constant environment; maintains certain set point rangers o Large external fluctuations; ex. Temperature outside o Small internal fluctuations; ex. Body pH level o Maintains by negative or positive feedback loops Negative: change is detected by the body, body reacts to reverse the condition Ex. (outside of the human body) o A room drops below the set temperature of 72 degrees o The thermostat senses the change and turns on the furnace o The furnace warms the room back up to 72 o The thermostat senses that the room is back at 72 and turns off furnace Positive: self-amplifying cycles; an initial change leads to a greater change Used for rapid change in the body Ex. Contractions during labor o Baby’s head presses on cervix o Pressure promote stronger and stronger contractions o …until eventually the baby’s head is in the birth canal Chemistry o Subatomic particles atoms elements o Subatomic particles: protons, neutrons, electrons # of protons = atomic number of an element For neutral atoms: # protons = # electrons Located in nucleus: protons and neutrons o Ions- atoms/molecules where # protons ≠ # electrons Cations: (+) charge Easily give up electrons Anions: (-) charge Easily accept electrons Also can be complex compounds (bicarbonate, HCO ) - 3 Bio 141 exam 1 Organic molecules (contain carbon) o Four primary categories: Carbohydrates Lipids/fats Proteins Nucleic acids o Monomer- single molecular unit of a polymer o Polymer- contains many repeating molecular units (the monomers) o Carbs Important functions Energy source o Immediate energy source (in form of glucose) o Stored energy (can be stored in form of glucose as well) Carb monomers Glucose (direct energy source) and fructose (can be made into glucose, but extra steps; comes from fruit; important in moderation and through fruits; not good in high-fructose corn syrup) Carb polymers (of glucose monomers) Starch- found in plants (how plants store glucose) Cellulose- found in plants (makes up structure of plants; cell walls; our body’s don’t break down cellulose well; not good source of energy) Glycogen- found in animals (form of storage of glucose; commonly stored in muscles for easy access of direct energy) o Lipids 3 main types Triglycerides Phospholipids Steroids Triglycerides- structure of 3 repeating structures (the polymer) Consist of fatty acids (3) (the monomer) o Primarily function as energy storage o And insulation (temp/organs) o What we think of as fat 3 fatty acids are connected by glycerol All single bonds o Different bonds present in different types of triglycerides Bio 141 exam 1 o Saturated and unsaturated fatty acids Saturated v. unsaturated- depends on amount of hydrogen Single bond- completely saturated w/hydrogen o Double bond (anything more than single)- break a bond and add hydrogen; unsaturated- ability to add hydrogen o Unsaturated- contain megafatty acids (humans can’t make them, have to consume them) Phospholipids- cell/organelle membranes Consist of fatty acids, phosphate group, and glycerol Glycerol- backbone that holds everything together Difference from triglycerides- 2 fatty acids + 1 phosphate group (just look for P) Can interact w/water; at the same time is propelled by water Hydrophilic- phosphate group (attracted to water) (has – charge) Hydrophobic- fatty acid chains (fear water) (neutral charge) Steroids- found in membranes and as hormones Proteins- polymers of amino acid monomers o Control multiple reactions to help maintain homeostasis o Primary structure- sequence of amino acids Fold to make final protein shape o Enzymes- important for physiological processes Nucleic acids o Function in… Energy transport (ATP) Hereditary (DNA) Protein syntheses (RNA) o ATP- monomer consisting of adenine, a sugar, and 3 phosphate groups o DNA- polymer consisting of 4 different nucleotides (monomers) Adenine, thymine, guanine, cytosine A with T G with C o Gene expression- process of making proteins from our DNA Within DNA, nucleotides are arranged into genes Bio 141 exam 1 Transcription- makes a working copy of the gene (to get RNA) (in nucleus) Translation- translate nucleotides to amino acids (take the working copy and make it into protein) (in ER) Cellular structure- composed of organelles o Cytoplasm- fluid inside cell Where many chemical reactions take place Ex. Cellular respiration o Nucleus- where DNA is o Endoplasmic reticulum- membrane Where translation takes place Via ribosomes (organelles made of proteins and RNA) o Golgi bodies- stacks of membranes Where packaging of proteins for transport into vesicles takes place o Mitochondria- ATP production Cell respiration Contain small circular piece of DNA o Cytoskeleton- network of proteins in cytoplasm Structural support Tracks for transport of vesicle Muscle function Actin allows for muscle contraction o Plasma membrane- made of phospholipids and cholesterol w/membrane proteins Bilayer is hydrophobic and hydrophilic due to lipids Selectively permeable Membrane proteins control what enters and exits cell Phosphate Hydrocarbon tails (fatty acids) Very little H2O in center, if any (why membrane is semi permeable Only things that can pass through without any help: very small, uncharged (AKA hydrophobic/non-polar) Transport of molecules across a membrane Bio 141 exam 1 Passive- doesn’t require energy o Ex. Diffusion o Requires concentration gradient (movement of particles from high to low concentration) Simple diffusion- molecule can travel through the membrane (small and uncharged) Channel-mediated diffusion- protein creates a channel in the membrane for a molecule to travel through (can be larger and have a charge) Gated channel or non-gated channel (AKA leak channels OR open all the time) Carrier-mediated transport: facilitated diffusion Carrier proteins- move solutes down concentration gradient Solute (or molecule) must bind to the membrane protein Protein changes shape and moves molecule across membrane Active- requires energy (usually ATP) o Carrier-mediated transport o Pumps- membrane proteins involved Require ATP hydrolysis to function + + Ex. Na /K pump Both molecules are being pumped up their gradient o Molecules “up their gradient” (low high) Creates stockpile, huge gradient Osmosis- diffusion of water across a membrane o Membrane is partially permeable (only permeable to H O2 o Depends on how much “stuff” is dissolved in the water o Water diffuses from where IT is highly concentrated (dilute solute) to where IT is lowly concentrated (concentrated solute) o Always think, “Where is the water going?” Water goes to where it is needed “Where is H 2 high? Where is H O 2 low? Bio 141 exam 1 If it’s low outside and high inside, it moves out of the cell (high low) o Hypertonic (more solute)- if A is hypertonic to B, A has more solute than B The solution is hypertonic to the cell) o Hypotonic (less solute)- the cell is hypotonic to the solution o Isotonic (the same)- the solutes are the same in both solutions Lecture 2- the Nervous system o Regulation- maintaining homeostasis (stable internal environment) o Systems that work for regulation Endocrine- sends chemical messages Works slowly; hormones Nervous- sends electrical signals and chemical messages Works fast; neurotransmitters o Structure o Two major subdivision Central nervous system (CNS)- brain and spinal cord Integration center Peripheral nervous system (PNS)- nerves Delivers/sends information to CNS o Nervous tissue o Neurons- specialized cells that make up nervous tissue Main characteristics: Excitability (uses ions) o Cells respond to stimuli from environment OR other cells o Results in electrical signal (action potential) – form of communication o Major evolution pressure to maintain this function for communication Conductivity- sending the message o Neurons propagate an electrical signal over a distance from its origin Secretion- passing on the signal o Neurons translate electrical signal to chemical signal Neuron structure Bio 141 exam 1 Cell body (Soma) o Contains ONE nucleus Dendrites- short and thick extensions off cell body o Receives signals from other neurons Axon- extension away from cell body o Some are covered by myelin sheath (myelinated)- improves conductivity Synapse- site of communication between neurons or between neuron and target tissue o Secretion Structural classes Multipolar- cell body at the end o Most common Bipolar- cell body is more centrally located Unipolar- cell body is off to the side o Axon comes after the cell body Functional classes Afferent neurons (sensory) o Sometimes called receptors o Specialized to detect stimuli o Start in PNS and travel to CNS o Delivers information about environment/condition of body to CNS Internuerons o In CNS o Receives and integrates information Efferent neurons (motor) o Send signals from CNS to effectors (targets) Muscles, organs, glands All of these pathways work by communication through electrical and chemical signals o Neural circuits Allows the body to monitor the environment (or itself) and decide on an appropriate response to maintain homeostasis o Electrical/chemical function of neurons Use electrical currents to communicate This speedy diffusion of ions across the membrane has been favored as form of rapid communication throughout evolution No concentration gradient = no communication Bio 141 exam 1 o If potential is 0 no flow of ions no communication Electrical potential (voltage) Voltage- concentration gradient of charged particles (the separation) Requires potential to create a current Electrochemical gradient- concentration gradient of charged particles Electrical current Flow of charged particles from one point to another Current- flow of charged particles from high to low o Example of passive transport In a battery… Flow of electrons in a battery circuit produces an electrical current A semipermeable membrane separates charges, creating voltage Flow of ions in/out of a cell (through protein channel) produces an electrical current Extracellular fluid (ECF)- outside the cell Intracellular fluid (ICF)- inside the cell EFC and ICF are separated by semipermeable membrane + + Main ions separated: Na and K o Electrochemical gradient o Consists of a concentration gradient of charged particles Na and K + o 2 components Chemical gradient- uneven distribution of molecules Electrical gradient- uneven distribution of charge Because molecules are ions Movement of ions through protein channels Driven by chemical gradient (diffusion) AND Electrical gradient (attraction/repulsion of charges) o How electrochemical gradient is established Chemical gradient- created by Na /K protein pumps The pump (active; requires energy) Moves 3 Na ions out and 2 K ions in Bio 141 exam 1 Creates slightly more positive environment outside the cell, and slightly more negative environment inside the cell The pump works to move Na ions out of the cell, but they can leak back in if there are leak channels + o Same goes for K ions; they will leak back out of the cell if there are leak channels These leak channels counteract the pump o But the pump works hard enough that the gradient is still there o The leak channels keep the gradient from getting bigger and bigger Electrical gradient- permeability and trapped anions More K leak channels than Na channels o More K leaves the cell than Na entering the cell + Cell is more permeable to K Inner membrane is more negative than outer membrane Trapped anions inside the cell o More anions are proteins and huge o They can’t get through trapped inside make inside more negative o Sodium- chemical and electrical gradient go in the same direction; enforce each other Wants to get into the cell because of chemical gradient (+) is attracted to (-) electrical gradient inside o Potassium- chemical and electrical gradient go in the opposite direction Coming out because of the chemical gradient But goes in because of the electrical gradient (+) attracted to (-) o Resting Membrane Potential (RMP)- balance of diffusion between chemical and electrical gradients o At rest; unexcited o Balance between chemical and electrical gradients = Electrochemical gradient o RMP = -70mV in neurons o All cells have a resting membrane potential o Changes in RMP lead to currents Currents are the communication (flow of charged molecules from high to low)- local action potential Bio 141 exam 1 o Local action potential- when a stimulus causes a change in RMP o Usually occurs at dendrite/cell body At stimulus sight, communication btw neuron 1 and 2, communication btw neuron 2 and 3 Effects are close to the origin, not down axon o If local potential is large enough (reaches the threshold) it activates action potential Threshold = -55mV o Usually excitartory in PNS From stimuli in the environment OR from organs inside the body o Excitatory or inhibitory in CNS Communication btw neurons via neurotransmitters o Ion movement is regulated by gated protein channels Certain stimulus opens it, allows current o Reversible to a certain point (like when dust lands on you) o Stimulus local potential reach threshold action potential communication to CNS o Ion movement during Local Potentials o Regulated by gated protein channels Respond to stimuli All passive o These function in addition to pumps and leak channels already working o Chemical gated channels (ligand) Usually a chemical binds and causes channel to open Ex. Taste, smell o Voltage gated channels (potential) Open in response to change in voltage o Mechanical gated channels Respond to force (vibration, touch); forces channel to open Ex. Hearing (vibrations), touch o Can result in excitatory response depolarization Na+ channels open and Na+ ions diffuse INTO cell Membrane potential becomes more POSITIVE (closer to zero) (closer to neutral) o Can result in inhibitory response hyperpolarization K+ channels open and K+ ions diffuse OUT of the cell Membrane potential becomes more NEGATIVE (farther from zero/neutral) o Type of gated channel depends on location in NS In PNS Usually ligand or mechanical Bio 141 exam 1 At interneurons Usually ligand o Ligands are neurotransmitters In CNS Chemical (ligand) o Example of Local potential o Depolarization This example is taking place at interneurons (chemical communication) Ligand binds Na+ chemical-gated channel Na+ channel opens and Na+ enters cell Membrane potential becomes LESS NEGATIVE (towards 0) If potential reaches -55mV (threshold) in cell body, action potential is triggered Electrical signal transmitted down axon o Action potentials o Always depolarize o Regulated by voltage-gated channels Located at axon hillock AP goes down axon Secretion at axon terminal o In LP- lots of (+) coming in, going to reach action potential o Na+ voltage-gated channels open at -55mV Na+ rushes in (to the first part of the axon only) o Membrane depolarizes (becomes LESS NEGATIVE) o Membrane potential reaches +30mV (peak depolarization) Na+ channels close K+ voltage-gated channels open K+ diffuses out of the cell Cell starts to repolarize (become MORE NEGATIVE) o Repolarization K+ channels stay open over a longer voltage More K+ leaves the cell than Na+ enters Hyperpolarization o Na+/K+ pumps actively transport ions back to original state Na+ comes out, K+ back in back to RMP Necessary to get back to RMP before another action potential can occur Absolute refractory period- from when it hits -55 til it gets back to RMP Relative refractory period- when it’s below RMP Bio 141 exam 1 Very strong local potential needed to overcome this o Conduction o Dendrites/cell body axon o After initial action potential Sodium diffuses in cytoplasm from entry point Causes adjacent voltage-gated channels to open Continues down axon One-way bc refractory period o Myelin Sheath o Electrically insulates axons o In CNS- made of oligodendrocytes o In PNS- made of Schwann cells Lipid/protein dense o Important for conductivity Allows for fast propagation o Action potentials only occur at nodes of Ranvier Myelin sheath allows ions to diffuse further bc they can’t be transported to ECF by pumps o Saltatory propagation- allows action potential (signal) to jump down axon between nodes o Not all neurons are myelated That would take up too much space Only ones that need fast conduction are o LP v. AP o LP Triggered by receptors and neurotransmitters Can depolarize or hyperpolarize the membrane Are graded (proportional to strength of stimuli) Reversible (to a certain point…threshold!) Local (effects are close to the origin) Decremental (signal gets weaker as it moves away from origin) o AP Triggered by voltage-gated channels Always depolarizes the membrane Are all-or-nothing (exhibits same peak regardless of stimulus strength Irreversible Self-propagating (effects have a great distance from origin) Non-decremental (signal is the same each time) Bio 141 exam 1 Lecture 3 o Synaptic activity- involves process of secretion Secretion- converting an electrical signal to a chemical signal Electrical signal of presynaptic neuron chemical signal in synapse BACK to electrical signal in postsynaptic neuron Allows neurons to communicate with each other o Neurotransmitters are synthesized in cell body and transported in vesicles to axon terminal Many NTs are derived from amino acids (dopamine/norepinephrine) Some can be gaseous or made of other chemicals (acetylcholine) Vesicle transport down axon to synapse uses microtubules (cytoskeleton) Or can be brought back to cell body for recycling o Postsynaptic neuron Can have 100s/1000s of synapses with presynaptic cells Presynaptic cells may release excitatory OR inhibitory neurotransmitters Some release excitatory; others release inhibitory o Summation- total of all local potential changes at synapses of postsynaptic cell Excitatory postsynaptic potential (EPSP)- depolarization of postsynaptic neuron Inhibitory postsynaptic potential (IPSP)- hyperpolarization of postsynaptic neuron Some neurotransmitters cause EPSP; some cause IPSP o Summation is one component of integration Integration- interneurons and motor neurons receiving info from multiple cells and summing the change to determine if an action potential is initiated Bio 141 exam 1
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