Unit 4 - Cell Communication and Cell Cycle Flashcards
1
Q
types of cell signals
A
lipid based and protein based
2
Q
lipid based chemical signals
A
- nonpolar (not soluble in water)
- hydrophobic
3
Q
since lipid based chemical signals are hydrophobic, what does this mean about cell membrane intercation
A
means it can go through the cell membrane
4
Q
examples of lipid based chemical signals
A
steroids - estrogen, testosterone
5
Q
what is the importance of lipid based chemical signals
A
they are important because they can pass right into the nucleus and modify DNA or gene expression
6
Q
protein based chemical signals
A
- polar
- soluble in H2O
- hydrophillic
7
Q
examples of protein based chemical signals
A
- epinephrine
- human growth hormone
- insulin
8
Q
mechanisms of transmitting the signals
A
- direct cell to cell contact
- short distances
- long distances
9
Q
juxtacrine
A
- signal transmitting mechanism
- direct cell to cell contact
ex: plasmodesmata, gap junctions, WBC’s
10
Q
plasmodesmata
A
- juxtacrine
- plant cells
11
Q
paracrine
A
- over short distances with chemical signals
- local regulators
ex: WBC’s, skin cells, neurons, quorom sensing
12
Q
endocrine
A
- over long distances with chemical signals traveling within the blood
- endocrine system
- hormones
13
Q
autocrine
A
- self signaling
ex: cancer
14
Q
antigens
A
a chemical nametag for identification
15
Q
explain juxtacrine
A
- macrophage attacks pathogen
- macrophage engulfs pathogen
- macrophage presents atnigen on cell membrane
- helper T-cell attaches and takes antigen
16
Q
what happens to a cell infected with a virus
A
it presents the antigen
17
Q
what happens after the infected cell presents antigen
A
- cytoxic T-cell connects to antigen
- local regulator makes cytoxic T-cell destroy cell
18
Q
what happens after the local regulator makes cytoxic T-cell destroys cell
A
helper T-cell releases cytokines (local regulators)
19
Q
local regulators
A
- chemicals released in short distances
- “signals”
- not in the bloodstream
20
Q
how do bacteria communicate?
A
a bacteria will send out a signal
21
Q
if bacteria gets a weak response, what happens?
A
nothing happens
22
Q
if bacteria gets a strong response, what happens
A
gene transcriptions activated
23
Q
endocrine system: glands
A
release hormones in the bloodstream
- target cells will have the receptors for the hormone
24
Q
ligand
A
- the chemical messenger
- the smaller molecule that binds to a typically larger molecule
ex: insuline, hormones, local regulators
25
types of ligands
lipid based and protein based
26
signal reception
- a cell receiving a message (ligand)
- ligand binds to receptor
27
protein based ligands have which type of receptor protein
they have a transmembrane receptor protein
28
lipid based ligands have which type of receptor protein
they have a intracellular receptor protein
29
signal transduction relies on what
it relies on signal reception which link to cellular response
30
transmembrane receptor proteins are made by which type of ribosomes
bound ribosomes (make proteins for cell membrane)
31
extracellular domain of transmembrane receptor proteins
- outside
- where the ligand binds
- polar
32
transmembrane region/domain
- nonpolar
33
intracellular region/domain
- polar
34
extracellular domain
- where the ligand attaches
- polar
35
types of transmembrane proteins
1. G-Protein Receptors
2. receptor tyrosine kinases
3. ligand gated ion channels
36
g-protein linked receptor: components
- alpha, beta, gamma subunit and GDP molecule
37
g-protein linked receptor: a shape change does what
a shape change in the receptor protein activates G-Protein
GDP -> GTP
- alpha subunit breaks off from beta/gamma
38
what keeps the g-proteins in place
*******
- tails keep G-protein in place
- if it was polar, this wont happen
39
steps of G-Protein reception
1. ligand attaches to the G-Protein linked receptor
2. attachment led to a conformational change in shape
3. change in shape activates g-protein
4. alpha subunit breaks free, GDP is replaced with GTP
40
what is the function of epinephrine
- fight or flight response
- increases heart rate
- breathing rate increases
- cell respiration increases -> need more C6H12O6
- breaks down glycogen to make glucose
41
what happens after the alpha subunit breaks free, and GDP is replaced with GTP (g-protein reception)
5. when ligand is removed the receptor returns to original shape
6. active g-protein diffuses across membrane
7. activates adenylyl cyclase (changes shape)
8. adenylyl cyclase converts ATP to cyclic AMP
9. alpha subunit comes off adenylyl cyclase and returns to inactive form
10. alpha subunit hydrolyses GTP to GDP (inactive)
42
what does adenylyl cyclase do?
it converts ATP to cyclic AMP
43
cyclic AMP
- second messenger
- relaying the original message into the cell
- amplify the message
44
does the adenylyl cyclase move?
this doesn't move
45
now that the original signal/message (epinephrine) has been relayed/converted into an intracellular signal (cAMP as the second messenger), what next?
46
kinases
- proteins
- function is to phosphorylate other proteins (kinases, enzymes)
47
phosphotase
removes phosphate from proteins
48
g-protein reception: what happens after alpha subunit hydrolyses GTP to GDP (inactive)
11. cyclic AMP activates protein kinase A
12. protein kinase A removes a phosphate from ATP
13. uses that P to phosphorylate the next protein kinase
49
phosphorylation cascade
- a chain reaction
- one kinase phosphorylates the next and so on
- this cascade amplifies the signal within the cell
50
g-protein reception: what happens following phosphorylation cascade
14. protein kinase A is deactivated, cyclic AMP is turned into just AMP
15. protein kinase 1 picks up a phosphate and phosphorylates protein kinase 2
16. protein kinase 2 activates an enzyme that will hydrolyze glycogen
51
do protein kinases stay active or inactive
inactive
52
what does adding a phosphate do
it changes the shape therefore also the function
53
dimer
54
receptor tyrosine kinase: insulin
1. insulin attaches to the ligand bonding site
2. forms a dimer
3. causes auto phosphorylating which activates the dimer
4. the dimer will phosphorylate relay proteins to pass the message on
5. this will relay the message and bring about a cell response
55
what does insulin do
it reduces blood sugar
*******HOW*********
56
ligand gated ion channel
1. neurotransmitter or local regulator binds
2. gate opens
3. ions can rush inside
4. when regulator is removed gate closes
57
why do multicellular cells rely on proper communication
they need their cells to work together to carry out functions
58
what is a receptor
a molecule (ex: protein) where a signal molecule can bind
59
gap junctions
- animal cells
- connections between two close together cells that can allow ions or other small molecules to pass so they don't have to pass across a cell membrane
60
synaptic signaling
- involves neurotransmitters and synapse
- example of paracrine signaling
61
autocrine signaling works how
- a cell secretes a certain molecule then binds to its own receptors and causes a response
62
simply explain ligand gated ion channels
- a ligand binds to a receptor (channel protein)
- in response, the channel protein opens
- ions are now able to go through, increasing the concentration of ions in the cell
- after reaching a certain concentration, the ligand leaves binding site and channel closes
63
are all ion channels LIGAND gated ion channels
no, they can be gated by other things
ex: voltage gated ion channel (dependent on electrical membrane potential)
64
key idea: body processes essential to life rely on cell signaling
65
cancer cells: disability
- produces too much of its own growth factor causing excessive cell division
66
examples of pathogens
bacteria or viruses
67
virus HIV: pathogens
- targets helper T-cells' CD4 receptor
- virus can attach and infect the cell
68
helper T-cells
- important immune cells
- contain CD4 receptors on their surface (to communicate with other immune cells)
69
phosphorylation
- the modification of proteins via addition of a chemical phosphate group
70
to function properly, cells must regulate processes to occur at the right time and place. they do this primarily by...
regulating the activity of proteins
- one way in which this is done, phosphorylation
71
what allows a phosphate group to be added to a protein by transferring the phosphate from ATP to the target
the enzyme kinase
72
what removes the phosphate group
the phosphatase enzyme
73
whether or not a protein is phosphorylated depends on what
if there are more kinases or phosphatases near it
74
how does phosphorylation really affect proteins
- adding a negatively charged phosphate group can affect how the amino acids bind together, changing the 3D structure
75
cell communication in animals depends largely on what
hormones
75
quorum sensing
the use of chemical messengers between bacteria to develop a community response
- bacteria infect a host with toxin and produce a ligand; once concentration of the ligand reaches a certain point, it becomes an indicator that bacteria population is sufficient and allows bacteria to act accordingly
76
two major classifications of hormones are
1. peptide based hormones
2. steroid based hormones
77
steroid hormones: characteristics
- nonpolar
- can freely cross cell membrane
- bind to intracellular receptor, enter nucleus, and initiate transcription
- ex: sex hormones
78
peptide hormones: characteristics
- large and polar
- cannot cross cell membrane, so they bind to an extracellular receptor
- initiate transcription
- trigger signal transduction
79
in steroid hormones, what enters the nucleus
the hormone receptor complex enters the nucleus to cause DNA transcription resulting in cellular response
80
does the protein ligand ever enter the cell?
NO.
- when the protein ligand binds its extracellular receptor, changes occur on the intracellular domain that cause the signal to get transmitted without the protein ever entering the cell or the nucleus
81
what are the 3 basic steps of cell signaling (peptide hormones)
1. reception
2. transduction
3. response
82
cholera
- disruption of signal transduction
- increased cAMP
- increased activity of ion pumps
- increased movement of ions from cells into intestinal tracts
- increased flow of water
- dehydration
83
what is signal transduction
Transduction is the conversion of a signal into a cellular response.
- the multiple steps that translate ligand into a response
84
what are some general examples of responses
- gene is turned on
- protein is manufactured
- enzyme is activated
- cell divides or dies
85
signal transduction pathway is when
a small collection of signal molecules produce a large response across the cell (amplify)
86
transduction
signal is transmitted through the cell and amplified
87
adenylyl cyclase
membrane-bound enzyme that converts ATP to cyclic AMP (cAMP), serving as a key component in cell signaling pathways and second messenger systems.
88
changes to any structure in the cell cycle can affect the
signal transduction pathway
89
mutation in the signal transduction paths effect
can prevent the cell from regulating its cell cycle
- when cell cycle is unregulated, it can result in unrestricted cell division that could lead to harmful conditions (ex. cancer)
90
what does an inhibitor do
inhibitor can block the sites of the receptor proteins so the ligand can't bind
91
how do gap junctions allows for communication
they allow for direct communication in between adjacent animal cells by forming channels that permit the exchange of small molecules and ions
92
what is plasmodesmata
- a narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication between them
93
target cell
the cell receiving the signal
94
signal transduction pathways link
signal reception and cellular response
95
define transduction
convert signal to a form that can bring about a cellular response
96
explain the role of protein modification in signal transduction pathways
- the role of protein modification in signal transduction pathways is to cause a conformational shape change due to the ligand binding. this change evokes an intracellular response which causes a second messenger to be activated
97
a phosphorylation cascade is
a signaling pathway where one enzyme phosphorylates another, causing an amplification of the reaction, leading to the phosphorylation of thousands of proteins
98
because the environment is not static, what must be true
organisms need to regulate signal transduction pathways to respond to changes in the environment
99
fight or flight response in a nutshell
- cell needs more energy so more glucose
- epinephrine binds to receptor and activates g-protein which ultimately leads to the breakdown of glycogen to release glucose
100
how does a mutation in any domain or component of the signaling pathway affect the rest
- mutation in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal
101
ethylene
- produced when you have bruising on fruit
- ripening of fruit
102
inhibition pathway
- CTR1 is active when ligand is not bound
- CTR1 inhibits EIN2 (stops transduction pathway)
103
ethylene on inhibition pathway
- when ethylene binds, the intracellular domain inhibits CTR1
- CTR1 inhibition activates EIN2
- EIN3 will activate RNA polymerase to make protein ethylene (positive feedback)
104
epidermal growth factor / cell division (could be damaged skin from a cell)
think of tyrosine kinase receptors
105
steroid hormones
- ligand can go through cell membrane and nuclear membrane
- intracellular receptor is in the nucleus
106
**CHANGES IN SIGNAL TRANSDUCTION PATHWAYS ALTER CELLULAR RESPONSES**
107
what are the consequences of a mutated receptor in the extracellular region
- ligand cannot bind (bc polarity usually changes)
- no cellular response
108
mutated relay protein (RAS)
- cellular response with no ligand
- uncontrolled cell response
109
absence of a ligand: what happens
- mutated intracellular domain
- activated
- unregulated cellular response
- type of cancer
110
homeostasis
- maintaining a balanced internal environment
111
hormones
ligand secreted throughout the bloodstream
112
negative feedback
- brings the body back to normal
- works opposite the direction of the stimulus
ex: high temperature -> sweat -> temp decreases
113
what happens when blood sugar is too high
- beta cells in the pancreas release insulin
- liver will store sugar as glycogen
114
what happens when blood sugar is too low
- alpha cells in the pancreas release glucagon
- glycogen is hydrolyzed and glucose is released
115
diabetes
an imbalance of blood sugar
116
type I diabetes
- no insulin
- immune system attacks beta cells so you can't make insulin
117
type II diabetes
- insulin resistance
- receptor is nonfunctional
118
thyroxine regulation
- regulates metabolism
119
what happens when there's too little thyroxine
- hypothalamus releases TSH releasing hormone (TRH); only affects pituitary
- pituitary releases TSH (affects thyroid)
- thyroid releases thyroxine
120
male/female sex hormones: too little
- hypothalamus: releases GnRH, affects pituitary
- pituitary: releases FSH and LH (follicle stimulating hormone); affects testes (or ovaries)
- testes release testosterone
121
what is osmoregulation
process of regulating water balance in the body
122
ADH
antidiuretic hormone
- ***function***: allows water to be reabsorbed by kidneys
- increases aquaporins
123
what is the cell cycle
- the lifecycle of a cell broken into 2 stages
- interphase (90%)
- m-Phase
124
why do cells need to divide
- to make more (reproduce)
- to repair
125
what are the three phases of interphase
G1 - gap/growth 1
S - synthesis
G2 - gap/growth 2
126
G1 Phase - Gap 1 Phase
- growing
- make duplicate organelles
ex: beta cells in pancreas -> makes insulin
127
G0 (G-Not)
stop dividing indefinitely
ex: neurons
128
G1 checkpoint
- ligand
- enough nutrients
- check for errors in the DNA
129
what happens if cell doesn't pass G1 checkpoint
if this fails, you don't get to S-phase
130
s-phase
- DNA gets duplicated
131
chromatid
one chromosome
132
sister chromatids
- a chromosome
- identical copies
133
centromere
- connects the sister chromatids
134
kinetachore
- what the spindle fibers (proteins) attach to
- rips the chromosome in half
135
what is chromatin
uncondensed DNA
136
what is chromatin made up of?
- DNA and histone proteins
137
chromosomes are made up of what?
dna AND proteins
138
G2 Phase
- more growth
- make more organelles
- make proteins/enzymes
139
G2 Checkpoint
- "Did the DNA duplicate correctly"
- if no, cell gotta die (apoptosis)
140
M-Phase
- mitosis
- cytokinesis
141
mitosis: prophase
1. nuclear envelope breaks down
2. chromatin condense
3. centrioles move to the poles of the cells
142
centrosome
pair of centrioles
143
mitosis: metaphase
- centrioles make spindle fibers that move the chromosomes into the center of the cell
- "line up"
*remember m=middle*
144
M-Phase checkpoint
- check for spindle fibers attached to each chromosome
145
in the m-phase checkpoint, what happens if spindle fibers aren't attached to each chromosome?
- nondisjunction: unequal distribution of chromosomes
146
mitosis: anaphase
- duplicated chromosomes are pulled to opposite poles of the cell; "pulled apart"
- enzyme activity does this
147
mitosis: telophase
- nuclear envelope reformed
- chromosomes uncondensed
**formed 2 genetically identical daughter cells
148
what is formed in telophase
2 genetically identical daughter cells
- diploid: body cells (2n)
149
mitosis: cytokinesis
FULLY seperated 2 daughter cells
150
cleavage furrow
- animal cells: where the cell divides
151
cell plate
- plant cells: where plant cell divides
152
how does a cell know when to leave G1 or move on to the next phase?
- external and/or internal signals
153
examples of external signals
- epidermal growth factor - local regulator
- platelet derived growth factor - local reg.
- growth hormones - long distance
154
examples of internal signals
- in cell
- cyclins
- cyclin dependent kinases (CDK's)
155
external signals -> cyclins
1. ligand binds (tyrosine kinase receptor) - epidermal growth factor, growth hormone, etc.
2. activates signal pathway or phosphorylation cascade
3. activates proteins within cell or relay message down to the nucleus
cell response:
activate gene expression - turn on genes to produce proteins that control the cell cycle, cyclins
156
cyclins
- proteins that push the cell through the cycle
- will regulate the cycle
- they are broken down
157
what happens if cyclins aren't broken down / why is it important that they do?
- cancer????????
158
what does it mean to "activate gene expression"
- a cell response that "activates gene expression" means that it turns on RNA polymerase and makes mRNA protein
159
DNA Polymerase
- replicates DNA
160
what do we need to move through the cell cycles
- we need cyclins and cyclin dependent kinases (CDK's)
161
S-Phase Cyclin
- duplicates DNA
- ligand binds to receptor
- s-cyclin is made
- s-cyclin binds to CDK
- CDK + cyclin picks up phosphate
- CDK + cyclin phosphorylates DNA polymerase
- DNA polymerase copies DNA
- cyclin is degraded
162
m-cyclin
*****
- M-Cyclin binds with CDK
- CDK phosphorylates enzyme
- enzyme breaks down nuclear envelope
163
what is tumor?
mass of cells
164
what is the function of a gene?
- it contains the instructions to make a protein
165
proto-oncogene
- genes that code for any protein involved in cell division
ex: receptor, ligand (HGH), RAS, kinase
166
mutagen
- anything that causes a mutated form of a gene
167
oncogene
- any gene coding for a protein involved in cell division that has been mutated
168
are there genes that inhibit or prevent cell division?
P53 - tumor suppressor gene
169
why are RAS proteins active without a ligand
- RAS Protein *******
170
P53
- check the DNA for errors
- if there are errors, it will phosphorylate a transcription factor to make a protein that blocks the cyclin from going to s-phase
171
what happens if P53 gene is an oncogene?
- if P53 gene is an oncogene, it will not check/stop the DNA from duplicating
172
what is a signal transduction pathway?
- is the binding of signaling molecules to receptors located on the cell surface or inside the cell that trigger events inside the cell to invoke a response
173
why do cells use signal transduction pathways?
cells use this to link signal reception with cellular responses
174
how does a signal transduction pathway begin?
after the ligand binds, the intracellular domain of a receptor protein changes shape, initiating transduction of the signal
175
reception
detection of a signal molecule coming from outside the cell
175
transduction
convert signal to a form that can bring about a cellular response
175
what is the role of protein modification in signal transduction pathways?
is to cause a conformational shape change due to the ligand binding. this change elicits an intracellular response, which causes a second messenger to be activated
175
what is the role of phosphorylation cascades in signal transduction pathways?
- a phosphorylation cascade causes an amplification of the reaction, leading to the phosphorylation of thousands of proteins
176
how do you know that the G-Protein is inactive
- when the GDP is present
177
how are signal transduction pathways used to influence cellular responses when there are changes in the environment?
these transduction pathways can regulate gene expression in response to changes in the environment or lead to apoptosis
178
how can mutations in the receptor protein or any component of the signaling pathway affect the transduction of a signal?
a mutation that alters the ligand/receptor specificity can lead to incompatibility, which can alter the signal transduction pathway. the receptor will not undergo proper conformational shape change, resulting in an inactive internal pathway
179
what are feedback mechanisms?
feedback mechanisms are processes used to maintain homeostasis either by increasing or decreasing a cellular response to an event
180
how does positive feedback affect homeostasis?
- these amplify responses and processes
- the stimulus is driven further away from initial set point, disrupting homeostasis
181
how does negative feedback affect homeostasis?
- if a system is disrupted, the negative feedback mechanisms return the system back to homeostasis
182
what is the role of interphase?
- is to allow newly divided cells opportunity to grow, maintain normal cell function, and prepare for division
- cell is going through processes of growth and preparation in order for cell division
183
what occurs during interphase?
during interphase cells grow, replicate DNA, and prepare for division
184
what is the role of mitosis?
mitosis plays a role in growth, tissue repair, and asexual reproduction and it ensures the transfer of a complete genome from parent to daughter cells
185
what occurs during mitosis?
during mitosis genetic information is transferred
186
what is the role of cytokinesis?
- ensures equal distribution of cytoplasm to both daughter cells
187
I PASSED MY ANATOMY TEST CALMLY
i - interphase
p - prophase
m - metaphase
a - anaphase
t - telophase
c - cytokinesis
188
what occurs during prophase?
- nuclear envelope disappears
- DNA coils into visible chromosomes
189
what occurs during metaphase?
- fibers align double chromosomes across the center of the cell
190
what occurs during anaphase?
- fibers separate double chromosomes into single chromosomes (chromatids)
- chromosomes separate at the centromere
- single chromatids migrate to opposite sides of the cell
191
what occurs during telophase?
- nuclear envelope reappears and establishes two separate nuclei
- each nucleus contains a complete genome
- chromosomes will begin to uncoil
192
when does cytokinesis occur?
- begins at the end of mitosis and separates the cell into two daughter cells
193
what are cell cycle checkpoints?
checkpoints are regulatory events in the cell cycle
194
what is the role of checkpoints in regulating the cell cycle?
checkpoints help determine whether the cell is ready to progress through the cell cycle
195
how are proteins involved in checkpoints?
proteins (cyclins) are used to activate or inhibit cell cycle activities
196
what happens if the cell cycle is disrupted?
apoptosis and/or cancer can occur when the cell cycle is disrupted
197
G1 Checkpoint
- end of G1 phase
- cell size check
- nutrient check
- growth factor check
- DNA damage check
198
m-spindle checkpoint
- fiber attachment to chromosome check
199
cyclins
- group of related proteins associated with specific phases of the cell cycle
- different cyclin are involved in different stages of the cycle
- concentrations can fluctuate depending on cell activity
- used to activate CDKs
200
why would concentration of cyclins increase in a cell cycle?
- cyclins are produced to promote cell cycle progression
201
why would concentration of cyclins decrease in a cell cycle?
- cyclins are degraded to inhibit cell cycle progression
202
cyclin dependent kinases (CDKs)
- group of enzymes involved in cell cycle regulation
- requires cyclin binding for activation
- phosphorylate substrates, promotes certain cell cycle activities
203
why is it important that cyclins degrade?
cyclins degrade to ensure proper regulation of the cell cycle because their degradation allows the cell to progress to the next stage of the cycle. **HOW**
*when a cyclin is degraded, it's like turning off the switch, allowing the cell to move to the next stage. its all about timing, if the switches don't turn off when they're supposed tp, things can go crazy and lead to problems like cancer.
204
what is a genome
- the complete set of an organism's genetic material, containing all the DNA needed to build and maintain that organism
205
concentrations of specific cyclins are stage specific, therefore
concentration peaks at stage transition
206
examples of positive feedback
- sucking milk of mammals stimulates more milk production
- fruits ripening
207
what is G0?
- a nondividing cell phase
"resting phase"
- what most cells are in
208
nondisjunction
209
levels of the cyclins change during cell cycle which results in...
different kinases being activated which activate different parts of the cell cycle
210
where does P53 block mitosis
- at the G1 checkpoint if there is damaged DNA by inhibiting CDK's
211
how does mutated P53 lead to cancer/tumor
mutated P53 does not arrest the cell cycle and therefore the damaged cell continues to divide which may result in cancer
212
oncogenic RAS protein
- mutated form that is always on, whether or not ligand is present
- continually tells cancer cells that it is okay to multiply
- leads to tumors/cancer
