exam 2 Flashcards
1
Q
nuerons
A
cells capable of transmitting signals across relatively long distances using electrical current
these signals = nerve impulses
2
Q
Cell membranes regulate
A
ion movement in/out of cell which Maintains different concentrations of various ions inside and outside of the cell; maintains gradient
3
Q
Ion gradient is also known as
A
electrical potential
4
Q
changing ion gradient along length of membrnae =
A
electrical current
5
Q
Sympathetic
A
Sometimes described as the “fight or flight” nerves; movement of skeleton/muscles
6
Q
Parasympathetic
A
Sometimes described as internal organ function nerves; responsible for every day functions (“Feed and Breed”)
7
Q
Sympathetic and parasympathetic nerves work in
A
concert to govern involuntary (visceral) functions in body
8
Q
Two systems in opposition to each other
A
maintains careful equilibrium
9
Q
Organ Systems
A
Cardiovascular Respiratory Digestive Urinary Reproductive
10
Q
afferent
A
Sensor neuron input
Activated by reflex centers in the CNS
11
Q
efferent
A
Motor neuron output
Activated by reflex centers in the CNS
12
Q
refex arc
A
complete circuit of nerves involved with involuntary response; from the incoming stimulus to the final effector organ
13
Q
Brain (conscious) can
A
override many reflex arcs
14
Q
what are the two types of cells in the nervous system?
A
neurons (highly Specialized) and glial cells (supportive)
15
Q
neuron types
A
sensory, motor and interneurons
16
Q
sensory neurons
A
Provide information about environment from body to brain
Sight, smell, touch, pressure, pain, temperature
17
Q
motor neurons
A
Provide movement information from brain to muscles (skeletal and smooth) and glands
Somatic
Autonomic (Sympathetic, Parasympathetic)
18
Q
interneurons
A
Receive signals from one neuron and transmit them to another
19
Q
what do Glial cells do? what kinds are there?
A
Most abundant in central nervous system (CNS)
Glia = “glue” (supportive)
the kinds are microglial, oligodendrocytes, schwann and astrocytes
20
Q
Microglial cells
A
phagocytosis of infectious material, debris
21
Q
Oligodendrocytes
A
form myelin sheath in CNS
22
Q
Schwann cells
A
form myelin sheath in PNS
23
Q
Astrocytes
A
control access of brain cells to blood( blood-brain-barrier)
24
Q
Neurons are capable of signal transduction which is
A
Receive a signal of one type, transmit a signal of another
Ex: when someone steps on your foot
Peripheral pressure-sensitive neurons in foot activated
Pain-sensing neurons activated as well
Two different signals must be transduced/ converted into an electrical signal that travels from foot spinal cord brain
Neurons in brain respond
25
Membrane Potential
difference in electrical potential between the inside and the outside of a cell this is a property of all cells
26
Electrical potential
the potential energy possessed by electric charges by virtue of their position in an electrostatic field; electricity property of all cells
27
All Living Cells at Rest
Disparity / inequality of charge inside to outside
Due to differing [ions] inside to outside
Produces Resting Membrane Potential (Vm)
= -60mV (net negative)
28
Neurons also have Electrical Excitability which is limited to
specialized cells ex. Nerve and muscle
29
Stimulation generates Action Potential (AP) which is
change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell
30
In nerve cells, positive charge can “flow” along the
axon; transmitting a signal across distance Made possible because of differential opening/closing of gated ion channels
31
gradiets excist across
cell membrane
32
contribute most to membrane potential
Na+, K+, Cl-
33
Degree of gradient
electrical potential (voltage)
34
When - / + charges put into motion
current (amp)
35
In the Steady-State:
Differing [ions] on either side of membrane determines resting membrane potential
“Leakage” occurs (ions leak down the gradient)
36
"leakage" must be managed otherwise..
K+ goes out ; cytosol = more negative(HYPERPOLARIZATION)
Na+ goes in ; cytosol less negative ; (DEPOLARIZATION)
Cl - goes in ; cytosol more negative; (HYPERPOLARIZATION)
37
If cell became suddenly highly permeable to Na+ in
purposeful depolarization
| neurons take advantage of this
38
If cell becomes suddenly highly permeable to K+ out
purposeful hyperpolarization
| neurons take advantage of this
39
Na+ and K+ flow can rapidly change through
ion channels
40
Integral membrane proteins
Form pores
Channels are “gated” -- opened/closed by changes in voltage
Some are “leaky”
Ion Channels
41
Voltage-Gated Ion Channels
Channels for Na+, K+, (Ca+2) that are Structurally similar (but not identical) it is a Rectangular “tube” with 4 walls
The potassium channel = multimeric (4 subunits)
The sodium channel = monomeric (4 domains)
One wall has voltage sensor
Channel Gating
Each wall has inactivation particle
Channel Inactivation
42
potassium channel
Multimeric; 4 subunits
Negatively charged amino acids concentrated at cytosolic entrance to the channel
Attracts positively charged ions
Repels negatively charged ions
43
vestibule
Below the selectivity filter is a widened area which accomodates hydrated ions
44
potassium channel contains
Each subunit contains 2 αhelices which tilt, forming a cone/pore (called pore helices)
Loop of amino acids jutting off of pore helices forms selectivity loop
45
The selectivity loops together form the
selectivity filter
46
Carbonyl oxygens that line the filter are what charged
negatively
K+ is relatively large; all 4 carbonyl oxygens are spaced to accommodate
Na+ is relatively small; carbonyl oxygens too far apart to interact uniformly only 2 carbonyl oxygens interact energetically unfavorable
47
Channel inactivation
Involves inactivating particle
Allows channels to close rapidly and stay closed (despite electrical stimulation) until membrane potential returns to resting state
48
what states can ion channels be in
open closed and inactivated
49
Different concentrations of various ions inside and outside of the cell
electrical potential
50
allow for flow of ions
electrical current
51
change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell
Action potential (AP)
52
types of synapses
electrical and chemical
53
electrical synapes
Presynaptic neuron + postsynaptic neuron
Connected by gap junctions
Composed of (6) connexin protein subunits (= connexon)
Connexons from pre- and post-synaptic neurons = gap junction
Allow for passage of ions, small molecules
Provides for cell-cell transmission with virtually no delay
Occurs where speed of transmission is essential
ex: cardiac cells
54
chemical synapse
Presynaptic neuron + postsynaptic neuron
Separated by 20 – 50nm space
Space = Synaptic Cleft
AP must be converted to chemical signal to cross the cleft, then converted back to AP
Chemical signal = Neurotransmitters
55
Neurotransmitters (NT)
Stored in terminal bulbs / synaptic knobs
located in pre-synaptic neuron
AP arrives stimulates vesicles containing NT to fuse with pre-synaptic membrane releasing NT into cleft
56
NT binds
postsynaptic membrane receptors
| Binding of NT alters membrane potential either stimulate or inhibit AP in next neuron
57
Excitatory post-synaptic potential =
EPSP (depolarization)
58
Inhibitory post-synaptic potential
IPSP (hyperpolarization)
59
Ligand-gated / Ionotropic =
= direct action
Act as ion channels
NT binds changes confromation ions pass through
Can stimulate or inhibit post-synaptic AP
60
Metabotropic
indirect action
Binding of NT activates intracellular messengers
Second messengers open ion channel ions pass through
Can stimulate or inhibit post-synaptic AP
Slower response than ionotropic
61
Neurotransmitters
Relay molecules - relay signals across synapses
“Signaling Molecules”
Must elicit a response when released into the cleft
Must be released at the right time / with right stimulus
62
neurotransmitter examples
Ex: acetylcholine
catecholamines – dopamine, norepinephrine, epinephrine
amino acids / derivatives – histamine, seratonin, etc.
neuropeptides - enkephalins
63
Acetylcholine (Ach)
Most common neurotransmitter in vertebrate PNS
and neuromuscular junction
Excitatory stimulates post-synaptic APs
When Ach binds increased permeability of postsynaptic membrane to Na+
Synapses that use Ach = cholinergic
64
Catecholamines
Derived from tyrosine
(dopamine, norepinephrine, epinephrine)
Synthesized in adrenal gland
Effects are complex; excitatory or inhibitory
Used in nerves, smooth muscles in the intestines;
certain nerve-nerve transmissions in brain
65
Synapses that use catecholamines
adrenergic
66
Amino Acids / Derivatives
```
Ex:
Histamine
Seratonin
Gamma-aminobutyric acid (GABA)
Glycine
Glutamate
```
Actions are complex – excitatory or inhibitory
67
Neuropeptides
Short chain amino acids
Hundreds identified
Differ from other NTs act on groups of neurons
Long-lasting
Ex: enkephalins = inhibitory - stop pain in CNS during shock, stress
substance P = excitatory
68
NTs must be inactivated quickly to prevent
overstimulation of the post-synaptic neuron
69
Degradation
Ex: acetylcholinesterase degrades acetylcholine
Consider: acetylcholinesterase inhibitors (organophosphates – pesticides, herbicides, nerve gas)
increased cholinergic effects muscle overstimulation
70
Re-uptake
Membrane pumps
| Consider: Selective seratonin reuptake inhibitors (SSRIs) (zoloft, paxil, lexapro, prozac)
71
protein trafficing
process involving all movement of proteins from one part of the cell or compartment to another
72
Protein targeting/sorting
type of trafficking whereby protein signals dictate where a protein will be located, how it will be sorted
73
peptide
<50 amino acids in primary structure
74
polypeptide
>50 amino acids in primary structure
75
protien
one or more polypeptides
76
4 stages of protein structure
```
Primary = sequence of amino acids
Secondary = alpha helices; beta sheets
Tertiary = folded
Quaternary = multiple polypeptides assembling together
```
77
how many common amino acids are there?
20
Grouped into polar, nonpolar, acidic/basic (charged)
Bound together with peptide bond
Amino end = N-terminus, Carboxyl end = C-terminus
78
process of translation
mRNA exits nucleus through nuclear pore complex
Ribosome binds mRNA
composed of protein, rRNA
contains mRNA binding site (small subunit)
large subunit contains active site for peptide bond formation
Individual codons exposed
Large subunit binds
Charged tRNAs interact with:
Aminoacyl site (A site)
Peptidyl site (P site)
Exit site (E site
79
There are differences between bacterial and
eukayotic translation
80
mutation alter DNA
change mRNA might change protein
81
Point mutations –
```
base substitutions (silent, missense, nonsense)
insertions, deletions (frame shift)
```
82
Chromosomal mutations
Gene duplication, deletion
Gene inversion
Gene translocation
83
"musts" of Post-translational Processing
Proteins must be modified
Proteins must fold – structure relates to function!
Proteins must be sorted/trafficked to destination
84
Organelles involved in post-translational processing
Endoplasmic reticulum
Golgi apparatus
Transport vesicles
85
cleavage
Proteins transported across membranes have block of amino acids removed (signal sequence)
86
splicing
modification of the nascent pre- messenger RNA (pre-mRNA)
87
mRNA
introns, exons; proteins = inteins, exteins
88
Inteins get removed,
exteins bind together
89
glycosylation
Carbohydrate side-chains added to protein
90
CHemical modifications
Small molecules added onto amino acids
91
multimeric (quaternary structure)
Single polypeptides combined with other polypeptides to create complete proteins
92
Targeting proteins to specific compartments of cell using signal sequence:
Co-translational Import
and
Post-translational Import
93
Cotranslational import into ER lumen
Ribosomes become bound to ER
Protein released into ER lumen processed
Packaged into vesicles to exit ER
To Golgi further processing
Packed into vesicles vesicles, lysosomes, plasma membrane
94
Signal Hypothesis (Blobel&Sabatini, 1971)
ER signal sequence itself doesn’t contact ER
| Instead signal recognition particle (SRP) mediates
95
Cotranslational Import to the er
translated protein is released in to ER (review steps) followed by folding I to quaternary structure
96
Abnormal Folding
Unfolded protein response
Sensors in ER membrane detect misfold
Triggers a temporary stop of translation for most other proteins
Enhances translation of chaperones and degradation proteins (proteosomes)
Misfolded protein then unfolded and refolded
ER associated degradation (ERAD)
Recognizes misfolded proteins
Retranslocates them from the cell for degradation
97
Cotranslational Import to Folding to?
Glycosylation
98
Some proteins translated on free ribosomes (cytosol)
| After translation these proteins:
```
May remain in cytosol
May be taken into certain organelles (post-translational import)
nucleus
mitochondria
chloroplasts
peroxisomes
```
99
Co-translational import
```
Folded
Glycosylated
Trafficked to:
Plasma membrane
**Outer organelle membranes
```
100
Integral Membrane Proteins: (IMPs)
```
Most common type= transmembrane
Spans entire membrane
Less common = integral monotopic protein
Emerges from the membrane on 1 side only
Essentially held in membrane with αhelical segments
```
101
Proteins destined to become IMPs have
specific signal tags that identify their final membrane destination
Carbohydrates attached to amino acid side chains
102
Remember: several membranes are targets
Plasma membrane
| Outer organelle membranes
103
Anchoring IMPs in ER membrane
Similar to regular translocation into ER (cotranslational)
104
Anchoring IMPs to ER Membrane:
The N-terminus is in ER lumen
| The C-terminus (and most of the protein) is in cytosol
105
Also possible to anchor to ER membrane using internal start-transfer sequence
No ER signal sequence
SRP interacts with internal sequence on protein
Hydrophobic region
Binds translocon
106
For multipass proteins:
Contain alternating stop-transfer and start-transfer signals
107
Note that ER membrane is where ALL
membrane proteins are first assembled (all-co-translational import)
108
4 essential needs of the cell
Genetic information to guide protein production (central dogma)
Molecular building blocks (nucleotides, amino acids, simple sugars, fatty acids, etc.) to build macromolecules
Chemical catalysts (enzymes)
Energy
109
traditional definition of energy
capacity to do work
110
another deffintion of energy
capacity to cause physical or chemical change
111
energy is required for
Synthetic Work
biosynthesis = formation of new chemical bonds
Mechanical Work
physical change in position or orientation of cell or some part of cell
Gradient Work
Maintaining concentration gradients (ex: pumps)
Electrical Work
Electrical signaling
Production of heat – homeotherms
112
1st Law of Thermodynamics
The law of conservation of energy
| Energy can neither be created nor destroyed; only altered in it’s form
113
2nd Law of Thermodynamics
Law of Thermodynamic Spontaneity
| The universe always tends toward greater disorder or randomness (entropy) –
114
free energy
measure of spontaneity = G
| ΔG = free energy change in a reaction
115
When ΔG is negative
spontaneous reaction, exergonic
116
When ΔG is positive =
= nonspontaneous reaction, endergonic
117
energy is released when
chemical bonds are broken
118
ATP
```
adenosine triphosphate
(3) components
Ribose
Adenine
(3) Phosphate groups
Energy “currency”
Releases 7.3kcal/mol
```
Has high potential energy (PE)
Three phosphate groups
119
there is no life without
ATP
120
ATP production
| Site:
mitochondria and chloroplast
121
ATP production process
Substrate-level phosphorylation
Oxidative phosphorylation
Photophosphorylation
Requires: a “food source” and oxidation-reduction rxns
122
Sources of "food" in ATP production
```
Autotrophs = self-feeders
and Heterotrophs (organotrophs) = “other-feeders”
```
123
type of autotrophs
Phototrophs capture light energy from sun convert light energy into chemical energy (carbohydrate) perform cellular respiration – oxidation
124
types of heterotrophs
Chemotrophs break chemical bonds in macromolecules recovered from other organisms; primarily through oxidation (of carbohydrate, glucose)
Lithotrophs feed on inorganic material
125
LEO” goes “GER”
Lose-electron-oxidation
| Gain-electron-reduction
126
RedOx Reactions:
usually accompanied by a proton (H+)
Molecule that contains the reduced atom gains a hydrogen (H) atom
has higher potential energy (PE)
Molecules that are oxidized often lose a proton along with an electron
have lower potential energy (PE)
“Follow the proton”
127
Electron Transport Chain
Fed by oxidation of NADH and FADH2
Electrons stepped down in energy along ETC
Proteins, cytochromes, quinones, Fe-S complexes, etc
Energy released used to produce proton gradient
Protons flow down the concentration gradient through ATP Synthase
Drives formation of ATP = oxidative phosphorylation
26 ATP / mol glucose
128
All eukaryotic cells use cellular respiration
Animals use Cellular Respiration
| Plants use Photosynthesis and Cellular Respiration
129
how do Bacteria, Archaea make ATP
use ETC, ATP Synthase to make ATP
130
Fermentation
Without oxygen or another electron acceptor available, electrons carried by NADH have nowhere to go
ETC stops Any NAD+ in cell quickly goes to NADH
Fermentation is a metabolic pathway that:
Regenerates NAD+ from stockpiles of NADH
Allows glycolysis to continue producing ATP
131
Photosynthesis
Light-dependent Reactions
Generate ATP
(Photophosphorylation)
Generate NADPH
132
exocytosis
expulsion or secretion of material from a cell by fusion of a vesicle with the plasma membrane
133
endocytosis
uptake of extracellular materials into a cell by infolding of the plasma membrane to form a vesicle
134
Phagocytosis
= form of endocytosis; large particles or whole organisms (>0.5um) taken into the cell for digestion
135
Vesicle
general term for small organelle compartment brought into cell through endocytosis
136
early endosome
small organelle compartment emerging from TGN; mildly acidic in chemistry; fuses with vesicles; can continue to mature into lysosome, or travel to other parts of cell and fuse with plasma membrane
137
late endosome
maturing early endosome; changing in contents and chemistry (more acidic)
138
lysosome
mature form; containing digestive hydrolases
139
exocytosis
Final step in the secretory pathway for proteins
Involves microtubule “tracks” that lead vesicles to plasma membrane
Fusion of secretory vesicle with plasma membrane triggered by second messengers
140
Colchicine
microtubule inhibitor inhibition of exocytosis
141
Exocytosis:Special case = polarized secretion
Allows for secretion from only one side/surface of cell
Intestinal epithelium
Nerve cells
Involves proteins gathered in subdomains of plasma membrane
142
endocytosis
Plasma membrane progressively folds inward
Pinches off and encloses material from outside of cell
removes plasma membrane from around cell
143
Vesicle that folds inward from plasma membrane fuses with
early endosome from trans golgi network (TGN)
144
Early endosome matures to late endosome
Late endosome to lysosome
145
Phagocytosis
“eating,” taking in large molecules
146
Pinocytosis
“drinking,” taking in liquid/dissolved material
147
Phagocytosis Mechanism
Material binds to plasma membrane
Pseudopods reach up, around material
Material gets pulled into cell in phagocytic vacuole
Binds with early endosome late endosome matures into lysosome degrades, breaks apart material
148
Receptor-Mediated Endocytosis
Certain soluble, suspended materials coming into cell tansport by vesicle
Vesicle pinches off = coated vesicle
149
Different “Fates” of RME materials
Endosome matures to lysosome ligand broken apart
Receptor recycled to membrane, ligand in endosome taken to destination in cell
Endosome carried to TGN for retrograde transport through endomembrane system
Endosome travels to another portion of membrane; releases ligand in exocytosis; called transcytosis
150
Coat Proteins:
Must be able to rapidly assemble and round out the invaginating vesicle
Must be able to rapidly disassemble so uncoated vesicle can then bind early endosome, etc.
151
signal transduction
any process by which a biological cell converts one kind of signal or stimulus into another
152
A system of messages (first, second, etc.) that produces
a cascade of events within and between cells tissues organs
153
First message must be received by cell – by a receptor
| Three types of receptors:
Plasma membrane receptor; with intrinsic enzyme capability (ex: tyrosine kinase linked receptors)
Plasma membrane receptor; coupled to GTP binding and hydrolyzing proteins (ex: G-protein coupled receptors, GPCRs)
Intracellular receptor; migrates to nucleus when bound to it’s ligand alters gene transcription (ex: glucocorticoid receptor)
154
in signal transduction he first message can
can bind receptor inside and outside the cell
155
fist message in signal transduction is
ligand
156
Ligand + receptor
ligand-receptor complex
157
PTKs can be classified as
receptor or non-receptor associated
158
PTKs:
Phosphorylate tyrosine residues on proteins (often enzymes)
Role in many regulatory processes
Differentiation
Growth
Cell migration
Proliferation
Abnormal signaling disease (cancer, inflammation, diabetes, etc.)
159
G-protein coupled receptor pathways
A membrane-associated receptor complex
| 7-pass transmembrane protein
160
Glucocorticoids
class of steroid hormones released from adrenal gland / adrenal cortex
Named for role in regulating glucose metabolism
Involved in immune response to inflammation
Inhibitory - quiet the immune response
