NPB 101 FINAL QUESTIONS & ANSWERS
What is homeostasis? - Answers --maintenance of a relatively constant internal
environment; the internal environment is in a steady state but not an EQUILIBRIUM
STATE
-This steady state can be restored even in the face of significant deviations from normal
in environmental or internal conditions
What are homeostatic reflexes? - Answers -Negative feedback loops
-Stimulus --> Sensory (sends data to) --> Control Center (directs response to stimulus) -
-> Effector (negative feedback and return to normal)
What is negative feedback? - Answers -A response to a change in the body that
counteracts or opposes the initial change. Returns back to normal
What is positive feedback? - Answers -Feedback that increases the output of a process
What is an example of negative feedback? - Answers -Body temperature
What is homeostatically regulated? - Answers -Nearly every organ system
homeostatically regulates a systemic (body-wide, or nearly so) parameter: body
temperature, blood glucose, gas concentrations in the blood, concentration of water
(salt & other electrolytes) and Body pH
What system isn't concerned with homeostasis in this course? - Answers -Reproductive
What are the proximate and ultimate explanations for different cell types? - Answers -
Differential Gene expression
What are the types of Intercellular communications? - Answers --Gap junctions:
Proteinaceous tunnels that permit free diffusion of small molecules from one cell to the
other
-Transcient direct contact via cell surface receptors. They can be linked to intracellular
cascades
What are the types of Extracellular chemical messengers? - Answers --Paracrine
secretion: spatial range = neighboring cells
-Neurotransmitter secretion
-Hormonal secretion: spatial range = body-wide
-Neurohormone secretion
Define the nervous system - Answers --Process fast, short-acting signals.
-It accomplishes this through a network of precise, direct connections between cells
(synapses)
,Define Neuron - Answers --Main cell type responsible for electrical-chemical signaling
in the brain
-Spikes (action potentials) are electrical events that spread rapidly thru a neuron
-Synapses are connections where a chemical message (neurotransmitter) is released
from the presynaptic terminal and detected by postsynaptic receptors
What is the brain? - Answers -A synaptic network
How are extracellular chemical messengers secreted by one cell detected by a target
cell? - Answers --These are specific ligand-receptors interactions. Typically, the ligand
activates the receptor
-The cellular response depends on the molecular identity of the receptor
-While there are many different types of receptors (= different proteins encoded by
different genes), they fall into 3 types:
1.)Nuclear receptors
2.)Metabotropic receptors
3.)Ionotropic receptors
What makes Nuclear receptors unique? - Answers --Intracellular
-Activate gene expression
What makes Metabotropic receptors unique? - Answers --Cell surface
-Activate biochemical cascades via protein-protein interactions
-2nd messenger
-cAMP pathway & IP3 pathway
What makes Ionotropic receptors? - Answers --Cell surface
-Themselves are ion channels
What are the relative speeds of signaling: nuclear receptors vs metabotropic vs
ionotropic? - Answers -Ionotropic > Metabotropic > Nuclear Receptors
What is the Plasma Membrane? - Answers --The outer boundary of the cell
-PM's of all cell types exhibit characteristic trilaminar appearance in electron
micrographs
What are the functions of cell membranes? - Answers --Regulate the passage of
substances into and out of cells and between cell organelles and cytosol
-Detect chemical messengers arriving at the cell surface
-Link adjacent cells together by membrane junctions
-Anchor cells to the extracellular matrix
-Anchor the cell to the cytoskeleton
Plasma membrane parts: - Answers -phospholipid bilayer + proteins, cholesterol and
other embedded within
,Fluid mosaic model parts: - Answers -lateral diffusion of phospholipids, cholesterol and
proteins
Membrane proteins perform a variety of functions vital to survival: - Answers --
Receptors proteins relay signals between the cell's internal and external environments
-Membrane enzymes can activate/deactivate intracellular or extracellular processes
-Cell adhesion molecules allows cells to identify each other and interact
-Transporter proteins and ion channels move molecules and ions across the membrane
What are lipids? - Answers --Polar head (charged) = hydrophilic
-Nonpolar tails (not charged) = hydrophobic
Compare hydrophobic and hydrophilic - Answers -Hydrophilic (head groups) = water
loving & Hydrophobic (tails) = water repelling
Lipids are mobile in Bilayer....How? - Answers --Thermal motion permits lipid molecules
to rotate freely around their long axes and to diffuse laterally within each leaflet
-A typical lipid molecule (at 37 C)
-Can switch to a gel like consistency at lower temperatures (gel-like consistency -->
(heat) Fluidlike consistency)
What are membrane proteins? - Answers --Membrane proteins attach to the bilayer
asymmetrically, giving the membrane a distinct "sidedness"
-They are responsible for most of the differences between cells in their activities
-Membrane proteins can be grouped into three distinct classes: Intergral membrane
protein, peripheral membrane proteins, and GPI-anchored protein
What are the faces of cellular membrane? - Answers -Cytosolic face (inner) and
Exoplasmic face (outer)
Initial experiments showing membrane fluidity? - Answers -The diffusion of Membrane
Proteins after Cell Fusion
-Cell fusion be induced by certain viruses, or with polyethylene glycol
-Membrane proteins (mouse cell + human cell) --> Hybrid cell --> Mixed proteins after 1
hour
Studying Protein Movement in Cell Membranes: Fluorescent Recovery After
Photobleaching (FRAP) - Answers --Proteins containing a fluorescent tag are used to
monitor protein movement
-A laser light is focused on a small area, bleaching the fluorescence
-A microscope is used to measure the fluorescence in the area that was bleached. It
slowly increased, indicating the movement of labeled proteins back into that area
-This allows us to monitor the speed and extent of protein move
-What is the mechanism that makes some proteins immobile? Anchored to the
cytoskeleton
, What affects rate of diffusion across a membrane? - Answers -Size and charge
Selective permeability: give examples of what are easily permeable and impermeable -
Answers --Hydrophobic molecules (O2, CO2, N2): easily permeable
-Small, uncharged polar molecules (H2O): barely permeable
-Large uncharged polar molecules (glucose, sucrose): impermeable
-Ions (Cl-, Na+, K+): IMPERMEABLE
What are the different types of membrane transport? - Answers --Simple diffusion
-Facilitated diffusion
-Membrane pumps
-Ion Channels
Define Ion Channels - Answers --Passive
-different types of membrane proteins needed for electrical signaling in neurons, muscle
and cardiac tissue. They are permeable to specific ions such as Na+ or K+
-Transport ions, water, and small hydrophilic molecule via facilitated transport
Define simple diffusion - Answers -when molecules spread from an area of high to an
area of low concentration
Define facilitated diffusion - Answers --Passive transport (no energy required)
-Movement from high to low concentration
-Carrier protein required (also called carrier-mediated transport)
Define membrane pumps - Answers --Active transport, requires ATP
-Different from facilitated b/c it can pump substances uphill against their concentration
gradient (also called carrier-mediated transport)
-Low concentration to high concentration
1.)What are transporters/carriers?
2.)What are the types? - Answers -1.)Move a variety of ions and molecules through the
membrane
2.)-Uniporters (passive): transport 1 molecule across membrane
-Pumps (active): coupled to hydrolysis of ATP
-Co-transporters (secondary active transport): harness the energy stored in the gradient
of 1 molecule in order to transport another (ex: symporters: same direction &
antiporters: opposite direction)
Difference between passive and active transport - Answers --Passive goes from high
concentration to low concentration & active goes from low concentration to high
concentration
Describe carrier-mediated transport - Answers --A mechanism for moving substances
across the P.M. when the substance across the PM when the substance cannot simply
diffuse or move "unassisted" through the membrane
What is homeostasis? - Answers --maintenance of a relatively constant internal
environment; the internal environment is in a steady state but not an EQUILIBRIUM
STATE
-This steady state can be restored even in the face of significant deviations from normal
in environmental or internal conditions
What are homeostatic reflexes? - Answers -Negative feedback loops
-Stimulus --> Sensory (sends data to) --> Control Center (directs response to stimulus) -
-> Effector (negative feedback and return to normal)
What is negative feedback? - Answers -A response to a change in the body that
counteracts or opposes the initial change. Returns back to normal
What is positive feedback? - Answers -Feedback that increases the output of a process
What is an example of negative feedback? - Answers -Body temperature
What is homeostatically regulated? - Answers -Nearly every organ system
homeostatically regulates a systemic (body-wide, or nearly so) parameter: body
temperature, blood glucose, gas concentrations in the blood, concentration of water
(salt & other electrolytes) and Body pH
What system isn't concerned with homeostasis in this course? - Answers -Reproductive
What are the proximate and ultimate explanations for different cell types? - Answers -
Differential Gene expression
What are the types of Intercellular communications? - Answers --Gap junctions:
Proteinaceous tunnels that permit free diffusion of small molecules from one cell to the
other
-Transcient direct contact via cell surface receptors. They can be linked to intracellular
cascades
What are the types of Extracellular chemical messengers? - Answers --Paracrine
secretion: spatial range = neighboring cells
-Neurotransmitter secretion
-Hormonal secretion: spatial range = body-wide
-Neurohormone secretion
Define the nervous system - Answers --Process fast, short-acting signals.
-It accomplishes this through a network of precise, direct connections between cells
(synapses)
,Define Neuron - Answers --Main cell type responsible for electrical-chemical signaling
in the brain
-Spikes (action potentials) are electrical events that spread rapidly thru a neuron
-Synapses are connections where a chemical message (neurotransmitter) is released
from the presynaptic terminal and detected by postsynaptic receptors
What is the brain? - Answers -A synaptic network
How are extracellular chemical messengers secreted by one cell detected by a target
cell? - Answers --These are specific ligand-receptors interactions. Typically, the ligand
activates the receptor
-The cellular response depends on the molecular identity of the receptor
-While there are many different types of receptors (= different proteins encoded by
different genes), they fall into 3 types:
1.)Nuclear receptors
2.)Metabotropic receptors
3.)Ionotropic receptors
What makes Nuclear receptors unique? - Answers --Intracellular
-Activate gene expression
What makes Metabotropic receptors unique? - Answers --Cell surface
-Activate biochemical cascades via protein-protein interactions
-2nd messenger
-cAMP pathway & IP3 pathway
What makes Ionotropic receptors? - Answers --Cell surface
-Themselves are ion channels
What are the relative speeds of signaling: nuclear receptors vs metabotropic vs
ionotropic? - Answers -Ionotropic > Metabotropic > Nuclear Receptors
What is the Plasma Membrane? - Answers --The outer boundary of the cell
-PM's of all cell types exhibit characteristic trilaminar appearance in electron
micrographs
What are the functions of cell membranes? - Answers --Regulate the passage of
substances into and out of cells and between cell organelles and cytosol
-Detect chemical messengers arriving at the cell surface
-Link adjacent cells together by membrane junctions
-Anchor cells to the extracellular matrix
-Anchor the cell to the cytoskeleton
Plasma membrane parts: - Answers -phospholipid bilayer + proteins, cholesterol and
other embedded within
,Fluid mosaic model parts: - Answers -lateral diffusion of phospholipids, cholesterol and
proteins
Membrane proteins perform a variety of functions vital to survival: - Answers --
Receptors proteins relay signals between the cell's internal and external environments
-Membrane enzymes can activate/deactivate intracellular or extracellular processes
-Cell adhesion molecules allows cells to identify each other and interact
-Transporter proteins and ion channels move molecules and ions across the membrane
What are lipids? - Answers --Polar head (charged) = hydrophilic
-Nonpolar tails (not charged) = hydrophobic
Compare hydrophobic and hydrophilic - Answers -Hydrophilic (head groups) = water
loving & Hydrophobic (tails) = water repelling
Lipids are mobile in Bilayer....How? - Answers --Thermal motion permits lipid molecules
to rotate freely around their long axes and to diffuse laterally within each leaflet
-A typical lipid molecule (at 37 C)
-Can switch to a gel like consistency at lower temperatures (gel-like consistency -->
(heat) Fluidlike consistency)
What are membrane proteins? - Answers --Membrane proteins attach to the bilayer
asymmetrically, giving the membrane a distinct "sidedness"
-They are responsible for most of the differences between cells in their activities
-Membrane proteins can be grouped into three distinct classes: Intergral membrane
protein, peripheral membrane proteins, and GPI-anchored protein
What are the faces of cellular membrane? - Answers -Cytosolic face (inner) and
Exoplasmic face (outer)
Initial experiments showing membrane fluidity? - Answers -The diffusion of Membrane
Proteins after Cell Fusion
-Cell fusion be induced by certain viruses, or with polyethylene glycol
-Membrane proteins (mouse cell + human cell) --> Hybrid cell --> Mixed proteins after 1
hour
Studying Protein Movement in Cell Membranes: Fluorescent Recovery After
Photobleaching (FRAP) - Answers --Proteins containing a fluorescent tag are used to
monitor protein movement
-A laser light is focused on a small area, bleaching the fluorescence
-A microscope is used to measure the fluorescence in the area that was bleached. It
slowly increased, indicating the movement of labeled proteins back into that area
-This allows us to monitor the speed and extent of protein move
-What is the mechanism that makes some proteins immobile? Anchored to the
cytoskeleton
, What affects rate of diffusion across a membrane? - Answers -Size and charge
Selective permeability: give examples of what are easily permeable and impermeable -
Answers --Hydrophobic molecules (O2, CO2, N2): easily permeable
-Small, uncharged polar molecules (H2O): barely permeable
-Large uncharged polar molecules (glucose, sucrose): impermeable
-Ions (Cl-, Na+, K+): IMPERMEABLE
What are the different types of membrane transport? - Answers --Simple diffusion
-Facilitated diffusion
-Membrane pumps
-Ion Channels
Define Ion Channels - Answers --Passive
-different types of membrane proteins needed for electrical signaling in neurons, muscle
and cardiac tissue. They are permeable to specific ions such as Na+ or K+
-Transport ions, water, and small hydrophilic molecule via facilitated transport
Define simple diffusion - Answers -when molecules spread from an area of high to an
area of low concentration
Define facilitated diffusion - Answers --Passive transport (no energy required)
-Movement from high to low concentration
-Carrier protein required (also called carrier-mediated transport)
Define membrane pumps - Answers --Active transport, requires ATP
-Different from facilitated b/c it can pump substances uphill against their concentration
gradient (also called carrier-mediated transport)
-Low concentration to high concentration
1.)What are transporters/carriers?
2.)What are the types? - Answers -1.)Move a variety of ions and molecules through the
membrane
2.)-Uniporters (passive): transport 1 molecule across membrane
-Pumps (active): coupled to hydrolysis of ATP
-Co-transporters (secondary active transport): harness the energy stored in the gradient
of 1 molecule in order to transport another (ex: symporters: same direction &
antiporters: opposite direction)
Difference between passive and active transport - Answers --Passive goes from high
concentration to low concentration & active goes from low concentration to high
concentration
Describe carrier-mediated transport - Answers --A mechanism for moving substances
across the P.M. when the substance across the PM when the substance cannot simply
diffuse or move "unassisted" through the membrane
