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BIO 141 Exam 1 study guide

by: Camryn McCabe

BIO 141 Exam 1 study guide Biol 141

Marketplace > Science > Biol 141 > BIO 141 Exam 1 study guide
Camryn McCabe
Penn State
GPA 3.81

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study guide for the first exam on 2/2-2/3 info from lectures 1-3
Janelle Malcos
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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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