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IB Bio HL > C2.1 Chemical Signalling (HL) > Flashcards

C2.1 Chemical Signalling (HL) Flashcards

1
Q

What is chemical signalling?

A

A process by which cells, tissues, and organisms communicate using signalling molecules.

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2
Q

What are the two types of cell-to-cell interactions in chemical signalling?

A
  • Direct interactions (steroid; intracellular)
  • Indirect interactions (protein; transmembrane)
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3
Q

What are ligands?

A

Signalling molecules that include hormones, neurotransmitters, cytokines, and growth factors.

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4
Q

What role do receptors play in chemical signalling?

A

Receptors exhibit specificity to ligands due to the structure of their binding sites.

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5
Q

What are the main functions of chemical signalling in humans?

A
  • Maintaining homeostasis
  • Development
  • Immune response
  • Neural function
  • Metabolic regulation
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6
Q

What initiates the cascade of biochemical reactions in signal transduction?

A

Conformational change in the receptor caused by ligand binding.

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7
Q

What are some specific cellular responses that can result from activated signalling pathways?

A
  • Changes in gene expression => by steroid/protein
  • Activation or inhibition of enzymes => insulin with protein kinases
  • Alteration of ion channel activity => calcium
  • Modulation of cellular metabolism => insulin/ephinephrin
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8
Q

What is quorum sensing in bacteria?

A

A process where bacteria communicate to coordinate group behaviour in response to cell density.
1. autoinducer as signal
2. signal increases as colonie increase sin size
2. bacteria detect increase in signal conc.
3. treshold is reached -> cascade transduction pathway
ex: bioluminescence

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9
Q

What are autoinducers?

A

Small signalling molecules released by bacteria that diffuse and accumulate in their environment.

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10
Q

What types of autoinducers do Gram-positive and Gram-negative bacteria use?

A
  • Gram-positive: processed oligopeptides
  • Gram-negative: acylated homoserine lactones (acyl-HSLs)
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11
Q

How does Vibrio fischeri utilize quorum sensing?

A

Releases N-acyl homoserine lactone to bind to regulators and induce the lux operon.

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12
Q

What chemical reaction produces light in bioluminescence?

A

The oxidation of luciferin by luciferase. (by lux operon)

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13
Q

What are hormones?

A

Chemicals secreted by endocrine glands into the extracellular fluid that act on target organs/tissues

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14
Q

What are neurotransmitters?

A

Chemical substances that carry signals from one neuron to another or from a neuron to a target cell

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15
Q

What are cytokines?

A

Small proteins important in cell signalling related to immune response

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16
Q

Which cells primarily secrete cytokines?

A

White blood cells such as macrophages and lymphocytes

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17
Q

What are the three main types of hormones?

A

Amines, peptide hormones, and steroids

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18
Q

Types of signalling molecules?

A
  • neurotransmitters = chemical & synaptic cleft
  • cytokines = proteins
  • calcium ions = 2nd messenger & muslce contraction
  • hormones = endocrine & long-lasting
  • cAMP = 2nd messenger
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19
Q

Give an example of an amine hormone.

A

Epinephrine (adrenaline)

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20
Q

What are peptide hormones?

A

Hormones in the form of polypeptide chains or small proteins

ex: insulin

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21
Q

What are steroid hormones derived from?

A

Cholesterol

usualy 4 ring & hydroxyl

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22
Q

What are the two ways hormones can act?

A

Activate second messengers or activate genes

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23
Q

Give an example of an amino acid neurotransmitter.

A

GABA (Gamma-aminobutyric acid)

24
Q

What can calcium ions trigger in cellular processes?

A

Muscle contraction, nerve impulses, and fertilisation

25
What are the four types of signalling based on distance?
* Autocrine signalling (on itself) * Paracrine signalling (nearby cell) * Endocrine signalling (long travel distance through blood) * Juxtacrine signalling (adjacent/direct contact cell)
26
What are cell-surface receptors?
Transmembrane Receptors present on the cell membrane that transmit signals from outside to inside the cell (for hydrophilic molecules)
27
What are intracellular receptors?
Receptors located inside the cell that bind to lipid-derived signalling molecules (for hydrophobic molecules)
28
What are Type I intracellular receptors?
Cytoplasmic receptors that translocate to the nucleus upon ligand binding | indirect signal
29
What are Type II intracellular receptors?
Nuclear receptors directly involved in gene transcription | direct
30
Name the three categories of cell-surface receptors.
* Enzyme-linked receptors * G-protein-linked receptors * Ion channel-linked receptors
31
What does signal amplification refer to in the context of signal transduction?
A process where a small signal triggers a larger response through activation of downstream messengers/effectors ## Footnote Hormones or neurotransmitters can activate protein kinases, amplifying the signal.
32
What is a common second messenger in signal transduction?
Cyclic AMP (cAMP) ## Footnote cAMP plays a crucial role in relaying signals inside cells.
33
What is the function of protein kinases in signal transduction?
AFter cAMP => To phosphorylate proteins by adding a phosphate group ## Footnote Protein kinases remain inactive until activated by second messengers like cAMP.
34
How is the signal terminated in signal transduction?
By degradation, diffusion, reuptake, inactivation of receptors, or feedback inhibition ## Footnote For example, acetylcholinesterase degrades acetylcholine to terminate its action.
35
What are the three types of neurotransmitters based on their effects?
* Excitatory neurotransmitters * Inhibitory neurotransmitters * Modulatory neurotransmitters ## Footnote Examples of excitatory neurotransmitters include glutamate; inhibitory neurotransmitters include GABA.
36
What is the role of acetylcholine at the neuromuscular junction?
Regulates muscle contractions and other functions like heartbeat and blood pressure ## Footnote Acetylcholine is the primary neurotransmitter associated with motor neurons.
37
What are G proteins and their function in signal transduction?
Molecular switches that undergo conformational changes when GPCRs bind to ligands ## Footnote They facilitate GDP/GTP exchange within the cell.
38
How many subunits do G proteins consist of?
Three subunits: ɑ, β, and γ & ***7 alpha helices*** ## Footnote Inactive G proteins have the ɑ subunit bound to GDP.
39
epinephrine mechanism?
* bind extracellular to G protein (needs GTP) * activates adenyl cyclase to convert ATp to cAMP (2nd messenger) * tranduction pathway to inactive protein kinase (phosporylates) => Inhibition of glycogen synthesis => produces more glucose
40
What is the function of adenylate cyclase in the presence of epinephrine?
Converts ATP to cAMP
41
What happens to GDP when epinephrine binds to its receptor?
GDP is replaced by GTP
42
What are tyrosine kinase receptors involved in?
Cell growth, differentiation, and proliferation
43
What process does tyrosine kinase undergo upon insulin binding?
Autophosphorylation
44
What are the two critical components of feedback mechanisms in regulating signalling pathways?
* Positive feedback * Negative feedback
45
What is homeostasis?
The maintenance of a stable internal environment in living organisms
46
What is the effect of positive feedback mechanisms in cell signalling?
They result in amplification of cell signals | ex: blood clotting
47
What is the role of negative feedback in cell signalling pathways?
It inhibits upstream activation, dampening the amplification of signals | ex: insulin & glucagon
48
Signal tranduction cascade (ligand)
1. receotor activation = ligand binds 2. signal amplification = stimuli triggers response 3. second messenger production = relay signal in cell 4. activation of protein kinases = phosphorylate proteins 5. change in gene expression 6. temrination of signal (degradation, diffusion, response, inactivation, feedback inhibition)
49
Mechanism of Insulin
* consist of dimer (compund of 2 molecules) = alpha & beta with disulfide bridges 1. Insulin binds extracellular 2. tyrosine kinase activated by insulin -> phosphorylates itself 3. activates signalling pathway 4. cascade reactions excretion of GLUT-4 vesicles 5. vesicle endocytosis = embeds GLUT-4 = cell can now accept glucose
50
Role of oestradiol
* secretes gonadotropin releasing hormone (GnRH) from neurons in hypothalamus * when increases = enhances GnRH => releases follicle stimulating hormone (LH & FSH) * creates menstrual cycle & ovulation
51
Role of progresterone
* maintains menstrual cycle & leads to secretal endometrium = periods 1. binds with progresterone receptor => GnRH relases LH 2. goes to testes & releases testosterone (negative feedback) * causes differnentiation of endometrial cells * secretes mucus in cervix too
52
Mechanism of trasmmebrane signalling
! endocrine gland secrete hormone directly into bloodstream ! Steroid * passes directly through plasma membrane * bind to receptor protein in cytoplasm (receptor.hormone complex) * enters nucleus as transcription factor * promotes transcription of specifc genes
53
Steroid vs Peptide hormones
Steroid * enters through plasma membrane * bind to receptor in cytoplasm * act directly on DNA * long term * directly affect transcription Peptide * do not pass through membrane * bind to extracellular receptor * transmits signal across membrane * short term effect * act through 2nd messenger/cAMP * influnece protein kinase
54
Effect/Mechnanism of intracellular signalling
! endocrine gland secrete hormone directly into bloodstream ! Peptide hormome * bind to receptor in plamsa membrane of target cell * activates cascade of reactions * mediated by second messanger * activation of enzyme
55
Dopamine mechanism
* depolarisation of presynaptic knob * opening of Ca2+ channel => diffuse into cleft * ca2+ stimulates dopamine relase * exocytosis

IB Bio HL (23 decks)

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