Unit 4 Flashcards
1
Q
What is critical for the function and survival of cells?
A
cell to cell communication
2
Q
What is cell to cell communication responsible for?
A
growth and development of multicellular organisms
3
Q
What are the three general ways cells communicate?
A
1) direct contact
2) local signaling
3) long distance signaling
4
Q
What is direct contact?
A
communication through cell junctions
5
Q
How do animal cells use direct contact?
A
gap junctions
6
Q
How do plant cells use direct contact?
A
plasmodesmata
7
Q
What can pass freely between adjacent cells?
A
signaling substances and other material dissolved in the cytoplasm
8
Q
What are local regulators?
A
chemical messengers (local regulator/ligands) that travel short distance through the exocellular fluid
9
Q
What do chemical messages cause?
A
a response in a target cell
10
Q
What are examples of local regulators?
A
paracrine signaling & synaptic signaling
11
Q
What is paracrine signaling?
A
secretory cells release local regulator via exocytosis to an adjacent cell
12
Q
What is synaptic signaling?
A
occurs in animal nervous systems; neurons secrete neurotransmitters (these diffuse across the synaptic cleft)
13
Q
What is synaptic cleft?
A
space between the nerve cell & target cell
14
Q
What do animals and plants use for long distance signaling?
A
hormones
15
Q
How do plants use long distance signaling?
A
release hormones that travel in the plant vascular tissue (xylem & phloem) or through the air to reach target tissues
16
Q
How do animals use long distance signaling?
A
use endocrine signaling ; specialized cells release hormones into the circulatory system where they reach target cells
17
Q
What type of communication involves a cell secreting a substance to an adjacent target cell?
A
paracrine signaling
18
Q
What structures do plant cells use in direct contact to diffuse substances?
A
plasmodesmata
19
Q
What three stages can cell to cell messages be divided into?
A
Reception, Transduction, Response
20
Q
What is reception (stage 1)?
A
the detection and receiving of a ligand by a receptor in the target cell
21
Q
What is a receptor?
A
macromolecule that binds to a signal molecule (ligand)
22
Q
How specific is the binding between ligand and receptors?
A
highly specific
23
Q
What happens to the receptor when a ligand binds to it?
A
receptor activates
24
Q
What causes the receptor to activate?
A
conformational change
25
What does activation allow the receptor to do?
allows the receptor to interact with other cellular molecules
26
What does interaction with other cellular molecules initiate?
transduction signal
27
Where can receptors be found?
in the plasma membrane or intracellular
28
What is the most common type of receptor involved in signal pathways?
plasma membrane receptors
29
What kind of ligands do plasma membrane receptors bind to?
polar, water soluble, large
30
What are examples of plasma membrane receptors?
- G protein coupled receptors (GPCRs)
- ligand gated ion channels
31
Where are intracellular receptors found?
in the cytoplasm or nucleus of target cells
32
What kind of ligands do intracellular receptors bind to?
ligands that can pass through the plasma membrane
33
What is an example of intracellular receptors?
- hydrophobic molecules
( steriod + thyroid hormones, gases like nitric oxide)
34
What is transduction?
the conversion of an extracellular signal to an intracellular signal that will bring about a cellular response
35
What does transduction require?
a sequence of changes in a series of molecules known as a signal transduction pathway
36
What is a signal transduction pathway?
a sequence of changes in a series of molecules
37
What does the signal transduction pathway regulate?
protein activity
38
How does the signal transduction pathway regulate protein activity?
- phosphorylation by the enzyme protein kinase (relays signal inside cell)
- dephosphorylation by the enzyme protein phosphatase (shuts off pathways)
39
What happens to signals during transduction?
it is amplified
40
What are second messengers?
small, non protein molecules and ions help relay the message and amplify the response
41
What is an example of a second messenger?
cyclic AMP (cAMP)
42
What does it mean if there is a change in shape?
a change in function
43
What happens during response (stage 3)?
the final molecule in the signaling pathway converts the signal to a response that will alter a cellular response
44
What are three examples of response?
- protein that can alter membrane permeability
- enzyme that will change a metabolic process
- protein that turns genes on or off
45
What are the three stages of cell signaling?
reception, transduction, response
46
What is the actual signal being transduced in a signal transduction pathway?
a ligand
47
How is a signal passed from outside to inside the cell?
through transduction; during transduction the signal is relayed by protein kinases and amplified by second messengers
48
What can signal transduction pathways influence?
how a cell responds to its environment
49
What can signal transduction pathways result in?
gene expression + cell function
( can alter phenotype or result in cell death)
50
What causes a change to the transduction of the signal?
mutations to receptor proteins or to any component of the signaling pathway
51
What are the three main ways that cells communicate?
direct contact, local signaling, long distance signaling
52
What does it mean when ligand receptor binding is highly specific?
- all receptors have an area that interacts with a ligand and only ligands specific to the receptors can bind to these areas, meaning not every ligand can bind to a receptor
53
What is the difference between direct contact communication in animal cells and plant cell?
- animal cells use gab junctions
- plant cells use plasmodesmata
54
What happens in the first stage of cell signaling?
a ligand binds to a receptor which can either be in the plasma membrane or intracellular
55
What happens in the second stage of cell signaling?
the signal is converted and it will bring about a cellular response
56
What is protein kinase?
an enzyme that relays signals inside of the cell ; it does this by phosphorylating various molecules
57
What is protein Phosphatase?
an enzyme that can shut off signaling pathways by dephorylating molecules
58
What happens in the third stage of cell signaling?
the final molecule in the signaling pathway will convert the signal to a response that will alter a cellular process
59
What are the two main categories of cell membrane receptors in eukaryotic organisms?
- G protein coupled receptors (GPCRs)
- Ion Channels
60
What is the largest category in cell surface receptors?
G protein coupled receptors (GPCRs)
61
What type of system are G protein coupled receptors (GCPRs) important in?
animal sensory systems
62
What do G protein coupled receptors (GCPRs) bind to?
binds to a G protein that can bind to GTP, which is an energy molecule similar to ATP
63
When do the GPCR, enzyme, and G protein become active?
when ligand binding to GPCR on the extracellular side takes place
64
What does ligand binding cause in GPCRs?
the cytomasmic (inside) side to change shape
65
What happens when the G protein binds to the GPCR?
activates the GCPR and the G protein, which causes GDP to become GTP
66
What does a shape change to the cytomasmic (inside) side allow?
the G protein to bind to GPCR
67
What happens when part of the activated G protein binds to the enzyme?
- activates enzyme
- amplifies signal and leads to a cellular response
68
Where are ligand gated ion channels located?
in the plasma membrane
69
What system are ligand gated ion channels important in?
nervous system
70
What happens in ligand gated ion channels?
- receptors act as a gate for ions
- when a ligand binds to the receptor, the gate opens or closes allowing the diffusion of specific ions
71
What can ligand gated ion channels initiate?
a series of events that lead to a cellular response
72
What must the body be able to monitor at all times?
internal conditions
73
What are set points?
values for various physiological conditions that the body tries to maintain
(ex. the set point for your body temp is 98.6 degrees F)
74
What is homeostasis?
the state of relatively stable internal conditions
( think : balance)
75
How does the body maintain homeostasis?
through feedback loops
76
What are the two types of feedback loops?
negative & positive
77
What is a stimulus?
a variable that will cause a response
78
What is a receptor/sensor?
sensory organs that detect a stimulus; this information is sent to the control center (brain)
79
What is an effector?
muscle or gland that will respond
80
What is a response?
changes (decreases or increases) the effect of the stimulus
81
What is the most common feedback mechanism?
negative feedback
82
What does negative feedback do?
reduces the effect of the stimulus
83
What does positive feedback do?
increases the effect of a stimulus
84
What is a disease?
when the body is unable to maintain homeostasis
85
What must happen in order to maintain homeostasis?
the cells in a multicellular organism must be able to communicate
86
How do cells communicate?
through signal transduction pathways
87
What process is an integral part of life?
cell division process
88
What does cell division allow?
the reproduction of cells, growth of cells, and tissue repair
89
What is the cell cycle?
the life of a cell from its formation until it divides
90
What must cells do before division?
organize and package their DNA
91
How are nucleosomes formed?
DNA associates with and wraps around proteins known as histones
92
What are histones?
the proteins that DNA associates with and wraps around
93
What do strings of nucleosomes form?
chromatin
94
When is a chromatin in a non condensed form?
when a cell is not actively dividing
95
When does a chromatin condense to form a chromosome?
after DNA replication
96
What forms a chromosome?
when a chromatin condenses
97
Why are chromosomes densely packed?
to allow for easier division
98
What does it mean for chromosomes when DNA is replicated?
each chromosome has a duplicated copy
99
How is a sister chromatid formed?
the duplicated copy of a chromosomes joint together
100
What is a centromere?
the region on each sister chromatid where they are most closely attached
101
What are kinetochore?
proteins attached to the centromere that link each sister chromatid to the mitotic spindle
102
What is genome?
all of a cell's genetic information (DNA)
103
What are prokaryotes?
singular, circular DNA
104
What are eukaryotes?
one or more linear chromosomes
105
What does every eukaryote have?
a specific number of chromosomes
106
What are homologous chromosomes?
two chromosomes ( one form mom and one from dad) that are the same length, have the same centromere position, and carry genes controlling the same characteristics
107
What are Somatic Cells?
- Body Cells
- Diploid (2n): two sets of chromosomes, one set from each parent
108
How do somatic cells divide?
mitosis
109
How many somatic cells do humans have?
46
110
What are gametes?
- reproductive cells (eggs/sperm)
- haploid (n): one set of chromosomes
111
How do gametes divide?
meiosis
112
How many gametes do humans have?
23
113
What does the cell cycle consists of?
altering phases of interphase and mitosis
114
What are the three stages of interphase?
- G1 "first gap" phase
- S "synthesis" phase
- G2 "second gap" phase
115
What is the longest portion of the cell cycle?
interphase (90%)
116
What happens in G1 "first gap" phase of interphase?
the cell grows and carries out normal functions
117
What happens in S "synthesis" phase of interphase?
DNA replication and chromosome duplication occurs
118
What happens in G2 "second gap" phase of interphase?
Final growth and preparation for mitosis
119
What happens in mitosis of M phase?
nucleus divide
120
What happens in cytokinesis of M phase?
cytoplasm divide
121
What does mitosis result in?
2 identical diploid daughter cells
122
What are the 5 stages of mitosis?
1) Prophase
2) Prometaphase
3) Metaphase
4) Anaphase
5) Telophase + Cytokinesis
123
What are the key events of prophase?
- chromatin condenses
- nucleoli disappear
- duplicated chromosomes appear as sister chromatids
- mitotic spindle begins to form
- centrosomes move away from each other
124
What are the key events of prometaphase?
- nuclear envelope fragments
- mircrotubules enter nuclear area + some attach to kinetochores
125
What are the key events of metaphase?
- centrosomes are at opposite poles
- chromosomes line up at the metaphase plate
- microtubules are attached to each kinetochore
126
What are the key events of anaphase?
- sister chromatids separate and move to opposite ends of the cell due to the microtubules shortening
- cell elongated
127
What are the key events of telophase and cytokinesis?
- two daughter nuclei form
- nucleoli reappear
- chromosomes become less condensed
128
In animals what happens when cytokinesis occurs?
a cleavage furrow appears due to contractile ring of actin filaments
129
In plants what happens when cytokinesis occurs?
vesicles produced by the golgi travel to the middle of the cell and form a cell plate
130
What is eukaryotic chromatin composed of?
DNA and Proteins
131
What proteins are responsible for holding the sister chromatids together?
cohesins
132
DNA is copied in which phase of the cell cycle?
S phase
133
Why does DNA being copied form sister chromatids?
each duplicated copy is joined together by cohesins
134
Which cell type undergoes mitosis?
somatic cells
135
Define Haploid (n)
a cell containing one set of chromosomes
136
Define Diploid (2n)
a cell containing two sets of chromosomes, one from mom and one from dad
137
What is the haploid number for humans?
n = 23
138
What is the diploid number for humans?
2n = 46
139
What are cell checkpoints?
control points that regulate the cell cycle
140
Where are checkpoints located?
all throughout the cell
141
What type of signals do checkpoints release?
stop + go
142
What is the most important checkpoint?
G1 checkpoint
143
What does the G1 checkpoint do?
checks for cell size, growth factors, and DNA damage
144
What happens after a "go" signal in the G1 checkpoint?
cell completes the wholes cell cycle
145
What happens after a "stop" signal in the G1 checkpoint?
cell enters a nondividing (quiescent) state known as G(0) phase
146
What happens to cells in the G(0) phase?
some cells stay in G(0) forever (muscle/nerve cells), while some cells can be called back into the cell cycle
147
What does the G2 checkpoint do?
checks for completion of DNA replication and DNA damage
148
What happens after a "go" signal at the G2 checkpoint?
cell proceeds to mitosis
149
What happens after a "stop" signal at the G2 checkpoint?
cell stops and the cell will attempt to repair damage
150
What happens if damage cannot be repaired inside a cell?
the cell will undergo apoptosis (programmed cell death)
151
What does the M (spindle) checkpoint do?
checks for microtubules attachment to chromosomes at the kinetochores at metaphase
152
What happens after a "go" signal at the M checkpoint?
cell proceeds to anaphase and completes mitosis
153
What happens after a "stop" signal at the M checkpoint?
cell will pause mitosis to allow for spindles to finish attaching to chromosomes
154
What does regulation of the cell cycle involve?
an internal control system
155
What does the internal control system consists of?
1) proteins known as cyclins (concentration of cyclins vary, and are synthesized and degraded at specific stages of the cell cycle)
2) enzymes known as cyclin dependent kinases (CDKs) (concentration remains constant through each phase of the cell cycle and are active only when its specific cyclin is present)
156
What does each cyclin CDK complex have?
a specific regulatory effect
157
What do active CDK complexes phosphorylate?
target proteins
158
What does the phosphorylation of target proteins by CDK complexes help regulate?
key events in the cell cycle
159
What are growth factors and what does it initiate?
hormones released by cells that stimulate cell growth
- can cause signal transduction pathway to be initiated because of CDKs being activated which leads to progression
160
What is Contact (or density) inhibition and what does it initiate?
cell surface receptors recognize contact with other cells
- initiates signal transduction pathway that stops the cell cycle G2 phase
161
What is anchorage dependence?
cells rely on attachment to other cells or the extracellular matrix to divide
162
How do normal cells become cancerous?
through DNA mutation ; changes in DNA
163
What cell follows checkpoints?
normal cells
164
How many times do normal cells divide?
average: 20-50 times
165
What cell goes through apoptosis when there are errors?
normal cells
166
What cell does not follow checkpoints?
cancer cells
167
How many times do cancer cells divide?
infinitely (considered immortal)
168
What cell evades apoptosis?
cancer cells evade apoptosis and continue to divide even if there are errors
169
What happens if there is uncontrollable growth of cancer cells?
tumors will grow
170
What is a tumor?
a mass of tissue formed by abnormal cells
171
What is a benign tumor?
- cells are abnormal, but not yet considered to be cancerous
- the cells remain at only the tumor site and are unable to spread elsewhere in the body
172
What is a malignant tumor?
mass of cancerous cells that lose their anchorage dependency and can leave the tumor site
173
What is metastasis?
when cells separate from the tumor and spread elsewhere in the body
174
Why does smoking cause cancer?
nicotine causes mutations in cells at high rates
175
How can eating healthy and drinking water prevent cancer?
fatty foods and dehydration can affect the function of cells
176
How can not using sun protection cause cancer?
sun is damaging to skin cells and can cause mutations to occur after exposure
177
identify the appropriate phase of the cell cycle or checkpoint: second gap phase
G2
178
identify the appropriate phase of the cell cycle or checkpoint: if the cell does not pass this checkpoint it is sent to G0
G1
179
identify the appropriate phase of the cell cycle or checkpoint: this checkpoint looks for correct DNA replication
G2
180
identify the appropriate phase of the cell cycle or checkpoint: first gap phase
G1
181
identify the appropriate phase of the cell cycle or checkpoint: DNA replication
S
182
identify the appropriate phase of the cell cycle or checkpoint: initial growth of the cells
G1
183
identify the appropriate phase of the cell cycle or checkpoint: the dividing phase
M
184
identify the appropriate phase of the cell cycle or checkpoint: this checkpoint looks for spindle fiber formation
M
185
identify the appropriate phase of the cell cycle or checkpoint: the final growth phase
G2
186
identify the appropriate phase of the cell cycle or checkpoint: if the cell does not pass this checkpoint it may go through apoptosis
G2
187
In which phase would the nuclear envelope fragment?
prometaphase
188
In which phase would the chromosomes line up at the metaphase plate?
metaphase
189
In which phase would two daughter nuclei form?
telophase
190
In which phase would chromatin condense and the mitotic spindle begin to form?
prophase
191
What is the difference between cytokinesis in animal cells and plant cells?
animals: a cleavage furrow appears due to contractile ring
plants: vesicles form a cell plate in middle of the cells
192
What checkpoint looks for cell size and growth factors?
G1
193
What happens to a cell that gets stopped at the G1 checkpoint?
it will enter a non dividing phase known as GO
