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Biochem 4511 Cogan - ACS Final Questions and Answers Fully Solved
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Biochem 4511 Cogan - ACS Final
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Biochem 4511 Cogan - ACS Finalrandom movement of molecules is impacted by... - answer1. size
2. charge
3. temperature
4. crowding
5. barriers
what can cross the membrane - answer1. hydrophobic molecules (O2, CO2)
2. small uncharged polar (H2O, glycerol)
characteristics unique to carriers - answer1. open to only one side at a time
2. passive or active
3. slower flow (hyperbolic curve)
characteristics unique to channels - answer1. can be gated
2. open to both sides
3. don't cycle in conformations
4. passive only
5. more rapid flow (linear plot)
what is similar for both channels and carriers - answerthey both have a selectivity filter
Bacteria K+ channel - answer1. 4 subunits (each 2 TM)
2. central filter that collects K+ ions
3. desolvated K+ alone is coordinated to backbone carbonyl groups in filter
Voltage gated K+ channels - answer1. channels that conditionally restrict flow
2. can be determined by many factors
what is an example of a voltage gated K+ channel - answerneuronal voltage gated K+
channels
when are neuronal voltage gated K+ channels open - answerS4-S5 helix responds to
voltage, bends upward
when are neuronal voltage gated K+ channels closed - answerS4-S5 helix presses on
S6 closing passageway
aquaporins - answer1. helical-based pores selective for water transport
2. special arrangement of an interrupted hydrogen bonding network (red) restricts flow
of protons
,is the glucose transporter active or passive - answerpassive
glucose transporter - answer1. glucose moves into red blood cells
2. blood glucose = 5mM
uniport - answersingle molecule moves in either direction
symport - answertwo molecules move together in either direction
antiport - answertwo molecules move in opposite direction
primary active transport - answeractive transport through a carrier coupled to ATP
energy source
what is an example of primary active transport - answerNa/K ATPase (only found in
animal cells)
secondary co-transport - answeruses an established gradient for active transport
what can secondary active transport be powered by - answer1. sodium gradient--animal
cells
2. proton gradient--plants and fungi
3. proton gradient--bacteria
functions of Na/K ATPase - answer1. water balance (removal of water)
2. secondary active transport (glucose and amino acid uptake)
3. excitable cells (nerve and muscle)
general features of pumps - answer1. pumps bind their ligands only on one side of the
membrane
2. have two distinct energy states
3. ATP hydrolysis is used to power conversion from low to high energy state
4. phosphate hydrolysis leads to "snap" back to low energy states
** balance between ATP hydrolysis and phosphate hydrolysis
action potential - answera sudden flux of ions across a neuronal cell membrane upon
stimulation
can either depolarize or hyperpolarize
what is the RMP - answer-70
how do action potentials travel - answeralong the axon from node to node (in between
sections of myelin sheaths)
, tetrodotoxin - answertoxin best known in pufferfish
blocks Na+ channels by binding to an amine group containing amino acid in the
selectivity filter of the channel
lidocaine and benzocaine - answerdental anesthetics
scorpion venom - answercan paralyze and kill humans
what is the 4 step scheme involved in signal transduction - answer1. reception:
signaling ligand received by sensor, most often a membrane receptor
2. transduction: conversion of one type of signal to another type of signal
3. amplification: cellular action activates paths (usually through second messengers and
effector enzymes which are turned on or off)
4. cellular response: activation/inhibition of necessary metabolic paths to satisfy the
demand required by the signal
general overview of quorum sensing - answerbacteria sense how many are alike near
them, and then they elicit a response together
signal transduction in quorum sensing - answer1. auto-inducer: alter behavior of
population that wouldnt be accomplished by an individual bacteria cell
2. inducer-receptor (intracellular): operon, receives messages intercellularly then goes
to genome to turn gene on
3. operon induction: makes Lux 1 which is positive feedback, high levels have auto
inducer to a local environment
what makes the auto-inducer? - answerthe enzyme
what happens when levels of operon reach a critical level - answerluciferase is turned
on
vibrio fischeri - answerlive in seawater and some associated organisms
what do G-protein coupled receptors sense - answerlight, taste, smell, nt's, 40 % all
drugs, metabolism
types of G-proteins - answer1. monomeric: single protein
2. heterotrimeric: 3 subunits (alpha, beta, gamma)
what are the domains of G-proteins - answer1. extracellular: ligand-binding, agonist
2. 7 TM alpha helixes
3. intracellular: guanine exchange factor
is G-protein reception extracellular or intracellular - answerextracellular
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