Test 2 Review Flashcards
(278 cards)
1
Q
What is the central dogma of molecular biology
A
DNA->RNA->Protein
2
Q
Transcription is?
A
the copying of nucelotide sequence from DNA to RNA
3
Q
Translation is?
A
the use of the information in RNA to form a protein
4
Q
T/F
Not every gene will be expressed the same frequency in every cell
A
True
5
Q
How do DNA and RNA differ?
A
RNA contains the sugar ribose, which has an extra OH group where DNA has just a H there
6
Q
How many genes are in the human genome?
A
Not all cells will be producing every time
7
Q
Uracil differs from Thymine because?
A
Uracil lacks a -CH3 group that thymine possesses
8
Q
Uracil base pairs with?
A
Adenine
9
Q
RNA molecules do something DNA does not because it is energetically favorable?
A
Forms intermolecular base pairs
-basically it base pairs with itself
10
Q
When these intermolecular base pairs fold they leave unpaired loops called?
A
Hairpin loops
11
Q
“Nonconventional” base-interactions allow RNA to do what?
A
form 3D structures
12
Q
Secondary structure within RNA is what?
A
When RNA folds over on itself and forms unconventional base pairing
it’s called secondary since the RNA has already been synthesized
13
Q
The extra OH group influences _______ and also makes RNA _______.
A
secondary structure
very volitile
14
Q
The coding strand of DNA and the transcript are?
A
The same
15
Q
The transcript has a strand that is complementary to?
A
the template strand
16
Q
RNA polymerase is a?
A
VERY LARGE enzyme
17
Q
DNA replication is?
DNA transcription is?
A
DNA to DNA
DNA to RNA
18
Q
RNA polymerase can can only synthesize RNA from?
but can read from?
A
5’ to 3’
3’ to 5’
19
Q
What unwinds the DNA during translation?
A
RNA polymerase
20
Q
After synthesizing the new RNA transcript strand, what does RNA polymerase allow?
A
DNA to rewind behind it
21
Q
mRNA codes for?
A
proteins
22
Q
rRNA does?
A
forms core of ribosome structure and catylizes protein synthesis
23
Q
miRNA?
A
regulates gene expression
24
Q
tRNA?
A
serves as adapters between mRNA and AA during proein synthesis
25
What is the promoter?
sequence of nucleotides that that falls before gene sequence that contains a specific sequence of nucleotides that lie upstream of the starting point for RNA synthesis
26
When is translation stopped?
When the RNA polymerase hits the terminator sequence
27
After the terminator sequence has been hit and DNA and RNA are released, what happens to RNA polymerase?
It binds with free sigma factor and searches for another promoter to begin the process again
28
What is free sigma factor?
a subunit of RNA polymerase that is primarily responsible for recognizing the promotor sequence
29
What about the structure of the promoter is important?
The promoter has a certain polarity which ensures that RNA polymerase binds to the promoter in only one orientation
30
What is always very important in regards to the promoter?
The location
31
The first nucleotide to be transcribed is always designated as?
+1
32
the -35 and -10 sites serve what purpose?
They are the sections of the promoter that orient the RNA polymerase
33
The direction of transcription is determined by?
The orientation of the promoter
34
RNA polymerase I is in?
Most rRNA genes
35
RNA polymerase II is in?
all protein-coding genes, miRNA genes, and all non-coding RNA genes
36
RNA polymerase III is in?
tRNA genes
| 5S rRNA genes
37
Bacterial cells have what type of RNA?
Only a single type, while eukaryotic have 3 different types
38
Bacterial RNA polymerase (along with it's sigma subunit) are able to?
initiate transcription on their own
39
Eukaryotic DNA needs what to start transcription?
RNA polymerase, sigma subunit, and a large set of accessory protiens
40
General transcription factors are?
Accessory proteins that assemble at the promoter before polymerase can begin
41
What is the DNA sequence called the TATA box?
a DNA sequence within most promoters, and made with lots of Adenine and Thymine
42
How is the TATA box recognized?
By the general transcription factor known as TFIID through a subunit known as TATA binding protein
43
The binding of TFIID then enables what to occur?
Binding of TFIID enables the adjacent binding of TFIIB
44
After binding of TFIID and subsequent binding of TFIIB, what occurs?
the rest of the general transcription factors including TFIIH as well as the RNA polymerase
45
What general transcription factor pries apart the DNA at the start portion using ATP hydrolysis?
TFIIH
46
Other than prying apart the DNA at the start point, what else of TFIIH do?
phosphorolates the long peptide tail of RNA polymerase II, releasing it from the general transcription factors so it can begin the elongation phase of transcription
47
What does the binding of the TBP do to the DNA?
Bends it
48
Why does the bending distortion occur when TBP binds to DNA?
because it may help to attract other general transcription factors
49
What is the structure of the actual TBP?
eight beta sheets that look similar to a bow
50
Where does the process of transcription occur?
in the nucleus
51
Does a location change occur during the process of transcription/translation?
yes-
| transcription occurs in the nucleus and translation occurs in the cytoplasm
52
How does the mRNA exit the nucleus?
Through nuclear pores - the 'highway' for mRNA exiting nucleus
53
There are two different processes before the mRNA can leave the nucleus, what are they?
RNA capping
| Polyadenylation
54
What is RNA capping?
modifies the 5' end of the RNA transcript.
| The 5' end is capped with guanine
55
What is polyadenylation?
adds a special structure to the 3' end, RNA transcript is cut at a particular sequence and then a long adenine tail is added (poly-A tail)
56
Why are the processes of RNA capping and polyadenylation needed?
Because they stablize the RNA and mark the RNA as mRNA
57
How do bacterial genes and eukaryotic genes differ?
Bacterial genes consist of long stretches of uninterrupted nucleotide sequences that encode AA
Eukaryotic genomes have coding sequences interuppted by non coding sequences
58
What are introns?
Non-coding sequences
59
What are exons?
Coding sequences
60
What must happen to introns before translation?
They must be removed
61
The Beta-globin gene encoding one of the subunits of the oxygen carrying protein hemoglobin contains how many exons?
3
62
The Factor VIII gene contains how many exons?
26
63
What is the process of removing introns?
RNA splicing
64
The RNA molecules that carry out RNA splicing are made of?
snRNAs packaged with additional proteins to form snRNPS (snurps) and all these snRNPS form the core splicesome
65
The splicesome is?
is a large assembly of RNA and protein that mediates the cleavage of RNA at the intron-exon borders
66
Introns form what structure during splicing?
branched structure
67
What are the steps to an intron forming a branched structure?
1-Branched point adenine attacks 5' splice site and cuts sugar phosphate
2-5' end on intron becomes covalently linked to the 2' oh group of the ribose of A to form branched structure
3- Free -OH end of exon sequence reacts with start of next exon sequence to, joining two ends of exons together and releasing intron in form of lariat structure which degrades
68
Splicing is carried out by a collection of RNA protein complexes called _____
snRNPs
69
The alpha tropomyosin gene can be spliced in different ways to?
Create different types of muscle cells
70
What is the process of splicing different sections of genes to create different proteins?
alternative splicing
71
What is a sign of mature mRNA?
the cap and poly-a tail
72
The exon junction complex is deposited on the mRNA after?
sucessful RNA splicing has occured
73
mRNA has been deemed 'export ready' when?
cap, poly a tail and exon junction complex is deposited
74
When mRNA has been deemed 'export ready' a?
nuclear transport receptor associates with it an guides it out of the cell
75
AUG is?
a start codon
76
Transcription is catalyzed by _______.
RNA polymerase
77
tRNA acts as?
an adaptor molecule for protein synthesis
78
How many possible nucleotide combinations are there?
64
79
The three codons that do not specify any amino acid but instead act as stop codons are?
UAA UAG UGA
80
the anticodon loop of tRNA binds to?
the complementary codon on the mRNA
the amino acid that the tRNA is transfering is attached to the other side
81
What is the process called charging?
When each sythetase couples a particular amino acid to its corresponding tRNA
82
What are animoacyl-tRNA syntgetases
enzymes that recognize the correct amino acid to couple with tRNA
83
A tRNA coupled with its amino acid is called a?
charged tRNA
84
Ribosomes are found?
in the cytoplasm of the cell
85
a ribosome is?
a large complex of four RNAs and more than 80 proteins
86
Each ribosome has a binding site for ______ and 3 for ________/
mRNA and 3 for tRNA
87
What forms the core of the large subunit of the bacterial ribosome?
23S rRNA and 5s rRNA
88
Why are ribosomes refered to by their "S values"?
The S values refer to their rate of sedimentation in an ultracentrifuge
89
What are the tRNA binding sites called?
A-, P-, E- sites
90
Translation takes place in a?
4 step cycle
91
During protein synthesis, only ___ sites are occupied of the 3 tRNA sites
2
92
What are the 4 steps of translation?
1) a tRNA carrying amino acids binds to the vacant A-site on ribosome forming base pairs with codon there
2) the carboxyl end of the polypeptide chain is uncouples from tRNA at the P-site and joined by a peptide bond to the amino group of the amino acid linked to the tRNA at the A site
3) a shift of the large subunit relative to the small subunit moves the two tRNAs to the E- and P- sites of the large subunit
4) the small subunit moves exactly 3 nucelotides along the mRNA molecules bringing it back to its original position relative to the large subunit. This resets the ribosome with an empty A site so that the process can occur again.
93
What stops translation?
The binding of release factor to an A-site bearing a stop codon terminates translation
94
The stop codons aren't recognized by? but signal to what to stop?
they aren't recognized by tRNA but signal to the ribosome to stop translation
95
When a stop codon reaches the A-site, what occurs?
the release factors bind to it, and this alters the activity of the peptidyl transferase in ribosome causing it to catalyze the addition of a water instead amino acid to peptidyl tRNA
96
The catylization of water instead of a AA to peptidyl tRNA does what?
frees the carboxyl end of polypeptide chain from tRNA and completed protein chain is released
97
Translation initiation factors are?
the initial tRNA, coupled to methionine, along with additional proteins
98
the initiator tRNA is distinct from the tRNA that?
normally carries methionine
99
The ___________ is the only tRNA that is capable of tightly binding to the P-site of small ribosomal subunit?
charged tRNA
100
The loaded ribosomal subunit (with bound charged tRNA) then?
binds to the 5' end of mRNA
101
Operons are?
clusters of genes describing different steps in a process
102
What do operons allow?
prokaryotes to synthesize several seperate proteins from single mRNA molecules
103
A series of ribosomes can simultaniously?
translate the same mRNA mol
104
What does the final concentration of each protein depend on?
the efficiency of each step of translation
105
How are concentration of proteins regulated?
by degradation, and its activity is regulated by binding of smaller proteins and other post translational mechanisms
106
For a protein to be useful in a cell, what must occur post translation?
the polypeptide must fold correctly, bind any cofactors, and assemble with protein parteners
-noncovalent bonding drives these changes
107
Covalent bonding helps polypeptides in what way?
Most proteins need covalent bonding to become active
108
What mediates protein degradation in Eukaryotes?
the Ubiquitin-Proteasome Pathway
109
What is achieved by gene expression?
Cell differentiation
110
What are the housekeeping proteins?
the structural proteins of chromosomes, RNA polymerases, DNA repair enzymes, ribosomal proteins, enzymes involved in glycolosis and other basic metabolic processes and many of the proteins that form the cytoskeleton
111
How can cells control the proteins it makes?
1) controlling when and how often a given gene is transcribed
2) controlling how an RNA transcript is spliced or otherwise processed
3) selecting which mRNAs are exported from the nucleus to the cytosol
4) selectively degrading certain mRNA molecules
5) Selecting which mRNAs are translated by ribosomes
6) Selectively activating or inactivating proteins after they have been made
112
In most genes the main site of control is?
transcription control, because it saves energy to have tight control at the begining
113
It is the binding of __________ to a regulatory DNA sequence that acts as the switch to control transcription
transcription regulator
114
The ______ region of a gene attracts the enzyme RNA polymerase and correctly orients the enzyme for transcription
promotor
115
What is included in the promtor region?
an initation citre
116
Regulatory sequences are used to switch a gene?
on and off
117
The more interactions between the protein and the bases including hydrogen bonds, ionic bonds and hydrophobic interactions contribute to the?
overall strength of the DNA-protein interaction
118
motifs are?
common structural patterns
119
A homeodomain is?
The 1st motif which is almost a domain, and this regulator recognizes DNA via 3 alpha helieces which allow protein to to fit in the major groove and form tight associations with base pairs
120
In a homeodomain, the asparagine residue from helices 3 forms two hydrogen bonds with?
the adenine from a A-T pair
121
What is a zinc finger motif built from?
an alpha helix and a beta sheet held together by a zinc molecule
122
Zinc fingers are often found?
clutered together covalently to allow a helix of each finger to contact the DNA bases in the major groove
123
Leucine Zipper Motifs are formed?
by two alpha helices
124
Leucine is?
very hydrophobic
125
Leucine zipper proteins tend to bind to DNA as?
dimers, like a clothespin clipping a clothesline
126
A cluster of bacterial genes can be transcribed from?
a single promoter
127
Transcription switches allow cells to respond to?
changes in the enviroment
128
the operator falls between?
two sites on the promoter
129
Genes can be switched on and off via?
receptor proteins
130
If the concentration of tryptophan inside of a cell is low, what does RNA polymerase do?
binds to the operator and transcribes the five genes of the tryptophan operon
131
If the concentration of tryptophan inside of a cell is high, what occurs?
a repressor protein becomes active and binds to operator, inhibiting the binding of RNA polymerase
132
If the concentration of tryptophan inside of a cell had been high, but then levels began to fall, what occurs to the repressor protein?
It dissaociates, allowing RNA polymerase to bind once again
133
Gene expressino can also be controlled by?
activator proteins
134
What does an activator protein do?
binds to a regulatory sequence on DNA and interacts with the RNA polymerase to help initate translation
135
Without an activator protein assisting RNA polymerase, the ?
promotor fails to initiate transcription efficiently
136
In bacteria, the binding of the activator to DNA is controlled by?
a small metabolite with the activator protein
137
cyclic AMP requires a?
CAP activator protein to become active
138
Genes activated by CAP are switched on in response to an increase in intracellular cyclic AMP concentration, which rises when what occurs?
When glucose is no longer available and drives production of enzymes that allow bacteria to digest other sugars
********
139
The Lac operon is controlled by?
the Lac repressor and the CAP activator
140
What does the Lac operon do?
encodes proteins required to import and digest lactose
141
The Lac repressor becomes active when?
glucose is absent and lactose is present
142
Lac operon-
+glucose
+lactose
operon off
143
Lac operon-
+glucose
- lactose
Operon off
144
Lac operon-
-glucose
+ lactose
opeorn on
145
Lac operon-
- glucose
- lactose
operon off
146
In Eukaryotes, gene activation can occur?
at a distance
147
How does gene activation occur at a distance in Eukaryotes?
by looping of the intervening DNA allowing contact between the activator and the transcription initiation complex bound to the promoter
148
In the figure 8-10, the large protein that serves as the go between for the distance between the activator and the general transcription factors in looping DNA is called the?
mediator
149
Eukaryotic transcription activators can recruit _______________ proteins t help initiate gene transcription.
chromatin modifying proteins
150
The chromatin modifying proteins allow?
The DNA and TATA boxes in condensed histones to become accessable to other proteins, including those required for transcription initation
151
acetyl groups are recognized proteins that promote?
trancription
152
Many repressors will recruit histone deacetylases why?
because these are enzymes that remove acetyl groups from histone tails. removing the positive effects that acetylation has on transcription initiation
153
Most transcription regulators usually bind to DNA using one of the DNA binding motifs that are?
homeodomain, zinc finger and leucine zipper
154
What is the most important control point of gene expression?
transcription initiation
155
_____________ in the DNA binding motif determines the particular DNA sequence that is recognized.
precise amino acid sequences
156
In eukaryotes, the regulatory DNA sequences are often far away from the promoter by?
thousands of nucelotides
157
Eukaryotic transcription regulators act in two major ways-?
1) Directly affecting the assembly processes of RNA polymerase and general transcription factos
2) locally modify the chromatin structure of promoter regions
158
The simplest changes in gene expression are often?
transient, such as responses to signals in their enviroments
159
Cell memory is?
the patterns of gene expression responsible for that identity
160
What is the most prevalent way that daughter cells remember what kind of cells they are is?
positive feedback loops
161
A positive feedback loop is?
a transcription regulator activates transcription of its own gene in addition to that of other cell-type-specific genes
162
Transcription regulators work together to?
form a 'comittee' to control expression of a eukaryotic gene
163
combinatorial control refers to?
the way tat groups of regulatory proteins work together to determine the expression of a single gene
164
A small number of trancription regulators can convert one differentiated cell type directly into another
Give an example of this
When in an experiment, liver cells grown in culture were converted to nerve cells after introduction of nerve-specific transcription regulators
165
In addition to positive feedback looping, what are the two other ways that cells maintain cell types
2) faithful propagation of a consensed chromatin structure from parent to daughter cell
3) DNA meythlation
166
Maintence methyltransferase guarantees that?
once a pattern of DNA methylation is established, it is inherited by newly made DNA
167
A daughter DNA sequence that is maintained by methylation will contain?
one methylated sequence and one unmethylated sequence, and the maintence methyltransferase methylates only the CG sequences basepaired with methylates CG sequence
168
During replication, about half the parents modified histones will be replicated in the daughter strand, and how does the cell succeed in modifying the other histones?
Proteins recognize a particular modification can bind to chromatin and cataylze the formation of the same modfiications on the new histones
169
Post-transcriptional controls regulate gene expression after?
transcription initiation
170
What are riboswitches?
short sequences in number mRNA's that change their conformation when bound to small molecules to regulate their own transcription and translation
171
What is the guanine synthesis controlled by?
riboswitches
172
When guanine is abundant, what occurs??
the guanine binds to the riboswitch causing it to undergo a conformational change which forces polymerase to terminate transcription
173
What is special about the Listeria monocytogenes bacteria?
it has an RNA 'Thermosensor'
The warmer temp. that the bacteria experiences while in the host degrades the thermosensor and allows virulence proteins to be made
174
What is 'antisense' RNA?
RNA that base pairs to a specifc mRNA sequence and blocks translation
175
An miRNA targets?
a complementary mRNA trancript for destruction
176
precursor microRNA is?
endogenous "noncoding RNA'
177
After being processed to form mature miRNA, the miRNA binds with?
a set of proteins into a complex called RNA-induced silencing complex (RISC)
178
After the mature mRNA binds with RISC, it then?
guides the RISC to mRNAs with a complementary nucleotide sequence
179
RNA interference is?
the destruction of foreign RNA molecules
-in particular double stranded RNA's produced by many viruses
180
In the first step of RNAi what occurs?
Foreign double stranded RNAS are cleaved by a nuclease called a dicer
181
A dicer is?
A nuclease that cleaves foreign double stranded RNAs
182
The second step of RNAi is?
the small interfering RNAS (siRNAs) -the short cleaved fragments of foreign double stranded RNA are incorporated into the RISCs which discard one strand and use the other to destroy complementary RNAs
183
What makes up a phospholipid?
phosphate containing, hydrophilic head and a pair of hydrophobic tails
184
amphipathic molecules are used to describe?
molecules with both hydrophilic and hydrophobic parts
185
The plasma membrane is involved in?
cell communication, import and export, and cell growth and motility
186
Receptor proteins in the plasma membrane are?
sensors that enable cell to receive information about changes in its enviroment and respond to them
187
What allows specific substances to be imported and exported through the plasma membrane?
highly selective channels
188
What are the 5 purposes of the plasma membrane?
bring nutrients in
pump waste out
protect internal organelles from harmful agents in extracellular enviroment
sense activities/changes in the extracellular enviroment
move around to change the shape of the cell
189
Both nucleus and mitochondria are each enclosed by?
two membranes
190
What is the most common phospholipid in the cell membrance?
phosphatidylcholine
191
What are the 5 parst of the Phosphatidylcholine molecules
choline (hydrophobic head)
Phosphate which links choline to glycerol
Glycerol which links phosphate to two hydrocarbon chains
Two hydrocarbon chains which originate as fatty acids
192
All membrane lipids are?
amphipathic
193
If a membrane can't move it can't _________ and what does it do to ensure movement?
function, and this is why it has a bilayer
194
Phospholipid bilayers spontaneously?
close in on themselves to form sealed compartments
195
Pure phospholipds can form?
closed, spherical liposomes
196
What increases the fluidity of the bilayer?
```
temp
heat->increase fluidity
types of hydrocarbon tails
length of tails (short tails increase fluidity)
unsaturated fatty acids incread fluidity
```
197
Scramblases do what?
remove randomly selected phospholipids from one half of the membrane and insert them into the other to ensure all newly formed phospholipids are redistributed equally
198
Flippases are?
they remove specific phospholipids from the membrane facing the exterior and flip them to the monolayer facing the cytosol
199
What effect does cholesterol have on the membrane?
it stiffens the membranes bilayer
200
Phospholipids and _____ are distributed asymmetrically in the plasma membrance lipid bilayer
glycolipids
201
What are the two faces of the bilayer?
cytosolic side- faces cytosol
| noncytosolic side- faces exterior of celll or interior of internal organelle
202
Membranes retain their orientation even after?
transfer between cell compartments
203
Glycolipids are?
located mainly in the plasma membranse and found ONLY in the nonctyosolic half of the bilayer with sugar groups facing exterior of the cell
204
What is an Na+ pump?
actively pumps Na+ out of cells and K+ in
205
What is a K+ leak channel?
allows K+ ions to leave cells
206
What are the 4 ways that membrane proteins can be attached?
Transmembrane
Monolayer-Associated alpha helix
Lipid linked
Protein attached
207
The backbone of a polypeptide chain is?
hydrophilic
208
Most transmembrane proteins are?
alpha helices
209
A transmembrane hydrophilic pore can be formed by?
amphipathic alpha helices
210
Porin proteins from what?
water filled channels and are made of 16 stranded beta sheets
211
If you want to break a membrane, what do you do?
use a detergent such as SDS and Triton X
212
__________ acts as a proton pump during the light-activated pumping cycle.
Bacteriorhodopsin
213
How does Bacteriorhodopsin work?
When retinal absorbes a photon of light, it changes shape and causes the protein to undergo a series of small conformational changes, these changes result in the transfer of one H+ moving across bilayer along the pump channel
In the presence of sunlight, thousands of bacteriorhodpson pump H+ out of the cell creating a concentration gradient which can be converted into ATP
214
Human red blood cells have?
a distinctive flattened shape
215
a ________ network forms the cell cortex in human red blood cells
spectrin
216
How are spectrin dimers along with small actin molecules attached to the plasma membrane?
by the binding of at least two types of attachment proteins to two kinds of transmembrane proteins
217
How can lateral mobility of plasma membrane be restricted?
tethering proteins to cell cortex
to extracellular matrix mol outside of cells
to proteins on surface of cells
dffusion barriers can restric proteins to a particular membrane
218
What is an example of diffusion barriers preventing movements of proteins?
A membrane protein is restricted to a particular domain of plasma membrane in gut epithelial cells
-a tight junction is the reason the protein cannot leave domain
219
The sugar coating on the outside of the membrane is called the?
hint* two names
carbohydrate layer or glycocalx
220
What is the purpose of the glycocalx?
to make cells slippery to protect from mechanical damage
221
the cell surface carbohydrates aid leukocytes how?
prompt sugar receptors that lightly binding with the leukocyte and allow the leukocyte to continue rolling along until they slip through epithelial cell to the site of intefection
222
What is the motility of protein diffusion?
The more spread out, the more movement
the more crumples the less movement (almost to the point of immotility)
223
FRAP is?
Fluorescence recovery after photobleaching that involves uniformily labeling the components of the cell membrane with a fluorescent marker
224
What are three of the solutes that the lipid bilayer is not impermeable to?
CO2,O2, H2O
225
What is the most plentiful charges cation outside of the cell?
Na+
226
The rate at which a molecule diffuses across the membrane depends of?
size and solubility
227
What are the inorganic ions that are most plentiful in all the solutes in a cells enviroment?
Na+, K+, Ca2+,, Mg2+, Cl- and H
228
The high Na+ outside the cell is balanced by?
Cl-
229
The high K+ in a cell is balanced by a varity of?
negatively charges intracellular ions
230
The maller the molecule and the more soluble, the ________________ it will diffuse across.
the more rapidly
231
Small hydrophobic molecules like _________ and small uncharged polar molecules ________ rapidly diffuse through the bilayer.
Small hydrophobic mol- O2, CO2, and N2
| small uncharged polar molecules- H2O, glycerol and ethanol
232
What creates a barrier in the membrane to the passage on ions and large uncharged polar molecules?
the hydrophobic interior
233
Small molecules and ions can enter the cell through ?
a transporter or channel
234
What are the two main classes of membrane transport proteins?
transporters and channels
235
What is a transporter?
A membrane protein that undergoes a series of conformational changes to transer small water-soluble molecules across the lipid bilayer
236
What is a channel?
a hydrophilic pore across the lipid bilayer will walls of protein through which specific ions or small molecules can diffuse
237
______ transfer molecules at a much greater rate then _______.
Channels transfer molecules at a much great rate then transporters
238
Ion channels can exist in either a?
open or closed conformation
239
Passive transport requires?
no energy and instead uses the power of concentration gradients
240
Active transport requires?
an input of energy and is only carried out by transporters
241
If a molecule moves from an area of high concentration to an area of low concentration then the molecule is moving?
down its concentration gradient
242
Simple diffusion requires?
no transport proteins
243
Facilitated diffusion requires?
transport proteins
244
The special type of transports that carry out active transport are called?
pumps
245
If a molecule moves from an area of low concentration to an area of high concentration, then the molecule is moving _______ its concentration gradient
up
246
Each membrane has it's own type of transporters, what are some examples?
**hint 4
nucleotide, sugar, amino acid, and Na+ pumps are some plasma membrane pumps
Fig. 12-8
247
What mediates the passive transport of glucose in the glucose transporter?
A conformational change when the glucose binds to the binding site
->remember, the same binding sites are exposed on each side of the membrane. But due to concentration gradient there will be a net transport of glucose down its concentration gradient
248
What are the two components of an electrochemical gradient?
- concentration gradient of an ion
| - distribution of positive and negative charges on either side of the membrane known as membrane potiential
249
What mediates the transport of water in and out of the membrane?
aquaporins
250
What are the three main types of Active transport?
- coupled pump
- ATP driven pump
- Light driven pump
251
Coupled transport is?
The movement of one molecule down its concentration gradient is coupled to the movement of another molecule up its concentration gradient
-think "hitching a ride"
252
ATP-driven pump is?
The movement of one molecule up its concentration gradient is coupled to the hydrolysis of ATP to ADP
253
Light driven pumos are?
The movement of one molecule up its concentration gradient is coupled to light energy
254
Why does the Na+ K+ pump play a key role in membrane transport in animal cells?
It is important for a cell to maintain a high concentration of Na+ on the extracellular side of the membrane as the movement of Na+ into the cell is coupled to the movement of other molecules across the membrane
Maintaining a high concentration of K+ on the cytoplasmic side of the membrane is important for proper functioning of the nervous system
255
The Na+ K+ pump requires?
ATP
256
How does the Na+ K+ pump transport ions?
in a cylic manner
Na+ out and K+ in
257
What is ATPase?
converts ATP to ADP
258
What are the steps in the Na+ K+ pump?
Step 1) Na binds
2) Pump phosphoroylates itself
- --Phosphate in high energy linkage
3) Phosphorylation triggers conformational change Na+ ejected
4) K+ binds
5) Pump dephosphorolated
6) Pump returns to original conformation, K+ ejected
259
What is the purpose of the Ca2+ pump
Intracellular signaling often involves an increase in intracellular Ca2+ therefor intracellular concentration of Ca2+ must be kept low
260
What is required of the Ca2+ pump?
requires ATP
261
Where does the Ca2+ pump pump from and to?
Pumps from cytosol into lumen of sarcoplasmic reticulum
262
What is the difference between uniport and coupled transport?
Uniport-1 mol transfered
| Coupled transport-2 mol transferred
263
What are the two subcategories of coupled transport and what do they do?
Symport-2 mol in same direction
| Antiport-2 mol in different directions
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What is an example of a symport protein?
The glucose-Na+
265
How does the glucose/Na+ protein work?
It uses the Na+ gradient to drive import of glucose
266
When the Na+ is done with it's couple transport with glucose, how does it exit the cell?
Through the Na+ K+ pump
267
H+ gradient pumps serve what function in bacteria and plants?
The same purpose as Na+ gradient serves in animals
268
The diffusion of water is?
known as osmosis
269
Cell lysis=
rupture of cell
270
cell crenation=
water rushing out of cell
271
Ion channels that are 'gated' refer to?
channels that can switch between an open and closed conformation
272
Voltage gated channels are?
controlled by membrane potential
Major player in transmission of electrical signals between nerve cells
controlled by extremely sensitive voltage sensors
charges in membrane potiental above a certain threshold value exert sufficent electrical forve on volatge sensors to encourage channel to open or close
273
Ligand gated channels are?
controlled by the binding of a ligand to the channel protein (receptor)
274
Stress activated channels are?
controlled by mechanical force
275
What type of channel allows us to hear?
stress activated channels
276
How do the stress gated channels in our ear work?
1) when noise is hear, it causes the basillar membrane to vibrate, which causes the stereocilia to tilt
2) This tilt stretches the filaments that connect eact sterocilia to each other
3) The tilt stretches the filament, which pull open the stress gates channel allowing postive ions to enter from surrounding fluid
4) the influx of positively charged ions activates hair cells which stimulates underlying endings of auditory nerve fibers that convery auditory signals to the brain
277
What is membrane potential?
voltage difference across a membrane due to a slight excess of positive ions on one side and of negative ions on the other
278
What is the typical membrane potential?
~60mV
