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AP Biology > Unit 4 Cell Communication 10-15% > Flashcards

Unit 4 Cell Communication 10-15% Flashcards

1
Q

Cells can communicate through _______ or from _______ via _______.

A

Direct contact & short/long distances via chemical signaling.

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2
Q

Juxtacrine Signaling

A

Direct contact between cells → signaling molecules on one cell bind to receptors on adjacent cell.

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3
Q

Gap Junctions & Plasmodesmata

A

Channels that connect the cytoplasm of adjacent cells → transfer of chemical signals and ions.

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4
Q

Local Signaling

A

Cells communicate over short distances using signals that affect neighboring cells.

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5
Q

Autocrine Signaling

A

Cell sends a signal to itself → releases a ligand that binds to its own receptor.

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6
Q

Paracrine Signaling

A

Cells release signaling molecules that affect nearby cells.

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7
Q

Morphogens

A

Signaling molecules that create a concentration gradient in developing tissues → cells closer to the source are exposed to higher morphogen levels, while those farther away receive less. This gradient activates different sets of genes, causing cells to differentiate.

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8
Q

Quorum Sensing

A

Bacteria release autoinducers to sense population density & coordinate gene expression once a certain threshold is reached.

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9
Q

Adaptive Immunity

A

Helper T cells recognize antigens on antigen-presenting cells (APCs) → release cytokines (paracrine) that activates the T cell. The T cell then signals itself (autocrine) to multiply and activates other immune cells to attack the antigen.

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10
Q

Endocrine Signaling

A

Long-distance communication where cells release hormones into the bloodstream → travel to target cells to initiate a response.

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11
Q

Insulin

A

Released by the pancreas → helps fat, muscle, and liver cells absorb glucose. Fat cells store it as fat, while muscle and liver cells store it as glycogen.

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12
Q

Human Growth Hormone

A

Made by the pituitary gland → promotes growth by breaking down fat & signaling the liver to release glucose for energy.

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13
Q

Signal Transduction

A

Process by which cells convert external signal into a cellular response.

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14
Q

What are the three stages of cell signaling?

A

Reception, Transduction & Response

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15
Q

Receptor-Ligand Interaction

A

Ligand binds to a specific receptor protein on a target cell → conformational change in receptor which triggers a signal transduction pathway.

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16
Q

Examples of Ligands

A

Chemicals, peptides, or proteins.
Ex. Hormones & Neurotransmitters

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17
Q

Reversible Binding

A

Non-covalent bonds allow ligands to detach easily. So cells to stop responding after the necessary response has occurred.

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18
Q

Allosteric Regulation

A

Molecule binds to an enzyme someplace other than the active site → change in shape & activity.

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19
Q

The _______ to receptor initiatives a _______.

A

Binding of a ligand & Signal transduction pathway

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20
Q

Intracellular Receptors

A

Located inside the cell → small, nonpolar ligands that can cross the membrane.
Ex. Hormones like testosterone & estrogen → regulate gene transcription.

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21
Q

Transmembrane Receptors

A

Located on the cell’s surface → large, polar ligands.
Ex. G-Protein Coupled Receptors & Ligand-Gated Ion Channels

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22
Q

Ligand-Gated Ion Channels

A

Change shape & open when a ligand binds, allowing ions to flow in or out of the cell. This changes ion concentrations & triggers a cellular response.

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23
Q

G-Protein Coupled Receptors

A

When a ligand binds to the G-protein coupled receptor, it activates the G-protein by swapping GDP for GTP. The active G-protein binds to another membrane protein & triggers a cellular response.

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24
Q

How do G-proteins show evolution?

A

They have 7 transmembrane domains & consist of alpha, beta, and gamma subunits, showing they evolved early in eukaryotes.

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25
Why do signal transduction pathways take place in multiple steps?
1. To amplify the signal & produce a large cellular response. 2. More opportunities for coordination & regulation.
26
What does phosphorylation & dephosphorylation do?
Regulate protein activity
27
The addition of a phosphate group _______ of a protein from _______ to _______.
Changes the shape & inactive to active.
28
Phosphorylation Cascades
Protein kinases phosphorylates other protein kinases → chain reaction that amplifies a signal.
29
Protein Kinases
Transfer phosphate groups from ATP to proteins (phosphorylation).
30
Protein Phosphatases
Remove phosphate groups from proteins (dephosphorylation).
31
Function of Protein Phosphatases
Turn off the signal transduction pathway by removing a phosphate group → deactivates protein kinase (reusable).
32
Secondary Messengers
Small, non-protein molecules that relay signals to target proteins in the cell, amplifying the signal. Ex. Cyclic AMP (cAMP) & Calcium ions (Ca2+)
33
Cyclic AMP
G-protein activates adenylyl cyclase which converts ATP to cAMP → cAMP activates protein kinase A which initiates a phosphorylation cascade.
34
Calcium Ions
When a signaling molecule binds to a receptor, it triggers the release of calcium ions from intracellular stores (E.R.) → released ions bind to proteins, triggering muscle contractions.
35
Signal Amplication
A signal is amplified as it travels through a signal transduction pathway → stronger cellular response. Happens through phosphorylation cascades & secondary messengers.
36
Signal Specifcity
Cells respond differently to the same signal because they have different sets of receptors, relay proteins, & response proteins. Ex. Epinephrine triggers the breakdown of glycogen in in liver cells & cause muscle contraction in heart cells.
37
3 Common Cellular Responses
1. Changes in gene expression: signal transductions activate/repress transcription factors. 2. Changes in cell function: metabolism, protein secretion, cell structure & movement. 3. Apoptosis: signal transductions can trigger an apoptosis cascade.
38
Importance of Signal Transduction Pathways
1. Different response to same external signals. 2. Signal amplification & stronger cellular response. 3. Opportunities for regulatory control. 4. Increase organism's fitness.
39
Signal Disruption
Include mutations in signaling molecules, receptors, proteins & temperature/pH → alter pathway function leading to overstimulation, understimulation, or blockage of signal. Ex. uncontrolled cell division (cancer), improper immune response, developmental errors.
40
Anthrax
Anthrax toxins target the breakdown of protein kinases, increasing cAMP levels.
41
Diabetes
Normal: binding of insulin to insulin receptors on target cells initiates a signal transduction pathway → Glut4 transports insulin into the cell. Diabetes: insufficient insulin/insulin resistance → decreased Glut4 activity.
42
Homeostasis
Organism's ability to maintain stable, internal conditions, despite external changes → isn't static; it's constantly adjusted using feedback loops & regulatory mechanisms.
43
Negative Feedback Mechanisms
Response reduces the effect of the stimulus, bringing the system back to balance.
44
Body Temperature Regulation (-)
High body temperature → hypothalamus triggers responses like sweating & vasodilation → heat dissipates, lowering body temperature.
45
Transpiration Regulation (-)
Plants absorb water through their roots & release it into the atmosphere through tiny pores (stomata) on their leaves. Excessive water loss → abscisic acid triggers guard cells to close the stomata → reduces water evaporation.
46
Blood Glucose Regulation (-)
Pancreas secretes insulin to lower blood glucose when levels are high, & glucagon to raise glucose when levels are low.
47
Positive Feedback Mechanisms
Response increases the effect of the stimulus, pushing the system further.
48
Childbirth (+)
Baby's pressure on cervix triggers the release of oxytocin → stimulates uterine contractions, increasing pressure on the cervix → more oxytocin release.
49
Fruit Ripening (+)
Ripe fruit secrete ethylene → accelerates ripening in nearby fruits → release more ethylene.
50
Blood Clotting (+)
Platelets adhere to injury site of a damaged blood vessel → releases chemicals that attract more platelets, forming a clot.
51
Cell Cycle
Series of regulated events leading to proper cell growth, DNA replication, & division into two daughter cells.
52
Interphase
Cell grows, replicates DNA, & prepares for mitosis → 90% of cell's life. Divided into G1, S phase, & G2.
53
Mitotic Phase (M Phase)
Cell divides into two, identical daughter cells.
54
G0 Phase
Cells exit the cell cycle & is not actively preparing to divide → still perform their function (nerves cells).
55
G1 Phase (First Gap)
Cell grows, synthesizing proteins & organelles.
56
S Phase (Synthesis)
Cell replicates its DNA → each chromosome has two identical copies called sister chromatids which are joined at the centromere.
57
G2 (Second Gap)
Further growth & preparation for mitosis + making sure DNA replication happened correctly.
58
Mitotic Phase (M Phase)
Division of cell's nucleus (mitosis) and cytoplasm (cytokinesis) to produce two, identical daughter cells.
59
1st Stage of Mitosis: Prophase
1. Uncoiled chromatins condense into chromosomes. 2. The nuclear envelope breaks down. 3. Duplicated centrosomes move to opposite sides of the cell → form the mitotic spindle (separates chromosomes).
60
Extension of Prophase: Prometaphase
1. The nucleus completely breaks down. 2. Microtubules from the mitotic spindle attach to the kinetochores of the chromosomes.
61
2nd Stage of Mitosis: Metaphase
Chromosomes line up at the metaphase plate.
62
3rd Stage of Mitosis: Anaphase
Microtubules shorten, pulling the sister chromatids apart & moving them to opposite sides of the cell.
63
4th Stage of Mitosis: Telophase
1. Nuclear envelopes form around each new set of chromosomes → two separate nuclei. 2. Chromosomes decondense into chromatin. 3. Mitotic spindles break down.
64
Cytokinesis
Cytoplasm of parent cell divides into two daughter cells. Animals form a cleavage furrow & plants form a cell plate.
65
Diploid vs. Haploid
Diploid: two sets of chromosomes, one from each parent (somatic cells). Haploid: single set of chromosomes (sex cells).
66
At the end of mitosis, there are _________.
2 daughter diploid cells that are identical to the parent cell.
67
Before DNA replication, a cell has ______ chromosomes, consisting of ______ chromatid.
46 & 1 → / shape.
68
After DNA replication, a cell has ______ chromosomes and ______ chromatids.
46 & 92 Each chromosome has 2 chromatids → X-shape.
69
Binary Fission in Prokaryotes
Single parent cell divides into identical daughter cells → genetically identical to parent.
70
Importance of the Cell Cycle
Allows organisms to grow, repair, and reproduce.
71
How is the cell cycle regulated?
Internal & external signals that act at specific checkpoints.
72
Criteria for the G1 Checkpoint
1. Cell has grown sufficiently. 2. Cell has enough energy & nutrients. 3. Scans for DNA damage. 4. Growth factors which promote the expression of proteins necessary for DNA replication.
73
What happens if a cell doesn't meet the criteria at the G1 checkpoint?
Cells enter G0 where the remain inactive → most specialized cells in the body.
74
Criteria for the G2 Checkpoint
Complete DNA replication & no DNA damage in order for cell to proceed to mitosis.
75
What happens if a cell doesn't meet the criteria at the G2 checkpoint?
1. Cell cycle is arrested, giving the cell time to repair the DNA. 2. If damage is too severe, the cell can initiate apoptosis.
76
Criteria for the M Checkpoint
1. Sister chromatids are attached to the microtubules. 2. Chromosomes are correctly lined up at the metaphase plate. *before anaphase
77
What happens if a cell doesn't meet the criteria at the M checkpoint?
Cell will stop mitosis until sister chromatids are correctly attached, preventing errors in chromosome segregation.
78
Nondisjunction
Failure to separate sister chromatids leads to daughter cells with an incorrect number of chromosomes. Causes genetic disorders like Down Syndrome.
79
Cyclin & Cyclin-Dependent Kinases
CDKs are activated by binding to cyclins → phosphorylate other proteins to drive the cell cycle. Work together to transduce signals that promote/halt the cell cycle. For different complexes at various phases.
80
The levels of cyclin ______ throughout the cell cycle.
Fluctuate
81
Growth factors ______ the presence of G1 cyclin, allowing it pass the G1 checkpoint.
Increase
82
Density-dependent Inhibitation
As cells become too crowded, the availability of essential resources decreases, preventing cells from dividing (inhibits CDK-cyclin complex at the G1 checkpoint).
83
During G2, mitotic cyclins bind the CDKs, form the ______ which triggers ______ & degrades the cyclin.
Mitosis-promoting factor & Mitosis
84
When there is DNA damage at the G2 checkpoint, ______ inhibits the ______, stopping the cell cycle.
p53 & CDK-cyclin complex
85
P53 can also initiate ______.
Apoptosis
86
3 Options for Cells
1. Undergo mitosis & divide. 2. Stop dividing in order to specialize (differentiation). 3. Undergo apoptosis.
87
Proto-oncogenes vs. Tumor Suppressor Genes
Proto-oncogenes: promote cell growth. Tumor suppressor genes: inhibit cell growth & promote apoptosis.
88
Mutations in proto-oncogenes or tumor suppressor genes led to _______ and _______.
Uncontrolled cell division & Cancer
89
Mutations in Proto-Oncogenes
Become oncogenes which promote uncontrolled cell growth & division, leading to cancer development.
90
Mutations in Tumor Suppressor Genes
No longer inhibits the cell cycle, leading to uncontrolled cell growth & cancer development.

AP Biology (8 decks)

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