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Biology > C2.1 CHEMICAL SIGNALLING > Flashcards

C2.1 CHEMICAL SIGNALLING Flashcards

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1
Q

Which type of signals are studied in this lesson?

A

Chemical

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2
Q

How do cells interact with each other?

A

By sending and receiving signals sent by signaling molecules.

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3
Q

Whats another name for signaling molecules?

A

Ligands

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4
Q

Outline how a signaling molecule sends a response:

A

1) A cell produces a ligand.
2) Ligand approaches ligand-binding site.
3) Ligand binding causes conformational changes in the receptor on the target cell.
4) Signal is passed on to the cell to perform a certain function.
5) ligand dissociates.

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5
Q

What are the 4 types of signaling molecules

A

Hormones, Neurotransmitters, Cytokines, Calcium Ions

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6
Q

Hormones outlined

A
  • produced by specialized cells in glands.
  • secreted by ductless endocrine glands, directly into blood flow
  • transported to all parts of the body, taking up to a minute
  • binds to receptors inside/outside the cell and promotes or inhibits certain activities.
  • has long-lasting effects
  • can target multiple types of cells so have widespread effects.
  • insulin, thyroxin, estrogen
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7
Q

Neurotransmitters

A
  • Transmit signals across the synapse.
  • secreted when a nerve impulse reaches the axon terminal.
  • Take 0.5-1ms to trigger a response due to a narrow gap.
  • binds to receptors on the plasma membrane.
  • short-lived effects as they are removed from synaptic gaps.
  • convey signals to specific post-synaptic membranes.
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8
Q

Cytokines outlined

A
  • small proteins
  • one cytoK can be secreted by various cells
  • some can be secreted by almost any cell type
  • do not travel as far as hormones
  • cant enter cells: only bind to receptors on T-C membrane
  • binding causes a cascade of signaling and thus changes in gene expression.
  • have multiple effects as one cytokine can bind to different RPs
  • have roles in inflammation, cell growth and proliferation, and development of embryos.
  • erythropoietin, interferon, interleukin
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9
Q

Ca2+ ions outlines

A
  • low intracellular concentrations as pumped out.
  • diffuse into cells through voltage-gated or ligand-gated channels.
  • used for signaling in neurons and muscles.
  • cause muscle fibers to contract
  • cause pre-synaptic neuron to release neurotransmitter into synapse
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10
Q

What is the advantage of unicellular organisms sending chemical signalling to each other?

A

helps adjust cell activity to population density

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11
Q

Quorum sensing

A

Changes in cell activity due to the proportion of receptors with ligands rising above a threshold.

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12
Q

How do Vibrio fischeri create bioluminescence?

A
  • VF cells secrete chemical signals which act as autoinducers.
  • Binds to LuxR in the protein.
  • LuxR-autoinducer complex binds to a position in the cell’s DNA that induce the transcription of genes coding for the production of luciferase.
  • Catalyses a oxidation rxn that releases energy in the form of blue-green light.
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13
Q

Outline the mutualistic relationship between Vibrio Fischeri and Bobtail squid:

A
  • Bacteria in the light organ are supplied with sugars and amino acid.
  • Light produced collectively by bacteria helps to camouflage the squid in moonlight.
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14
Q

What are the properties of any signalling molecule?

A
  • Distinctive in shape and properties so that it can be distinguished from other chemicals.
  • Small and soluble enough to be transported.
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15
Q

Acronym for amine hormones:

A

Amine
Melatonin
Adrenaline
Thyroxin

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16
Q

Acronym for Peptide hormone:

A

Peptide
Adh
Insulin
Glucagon

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17
Q

for steroid hormone

A

Steroid
Testosterone
Oestradiol
Progesterone

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18
Q

for Amine NTs

A

Amine
Norepinephrine
Dopamine

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19
Q

Example of gas NTs

A

Nitrous oxide

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20
Q

Amino acid NTs

A

Glycine, Glutamate

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21
Q

Ex of Ester NT

A

AcH

22
Q

Contrast the effect of NTs and Hormones;

A
  • NTs have a very localized and immediate effect; they only have to diffuse across 40-20 nm.
  • hormones target cells in any type of the body along long distances; effect takes longer to be observed.
23
Q

Contrast Transmembrane and intracellular receptors;

A
  • Transmembrane proteins with hydrophilic amino acids that attract the receptor to aq solutions and cytoplasm and hydrophobic core surface that attract it to HC tails.
  • Intracellular have hydrophilic amino acids on their whole surface.
24
Q

Outline the Transmembrane signal transduction pathway:

A
  • Ligand binds to transmembrane receptors.
  • Secondary messenger produced inside the cell and binds to effector inside the cell.
  • effector is activated and carries out responses to the signal.
25
Q
A
26
Q
A
27
Q

Outline the intracellular receptor signal transduction pathway:

A
  • Ligand diffuses through the cell membrane.
  • Binds to receptor inside.
  • Ligand-Receptor complex regulates gene transcription
27
Q

Outline the transmembrane receptor pathway for acetylcholine neurotransmitter:

A
  • acts in synapses between neurons and muscle fibres
  • binding causes a change in the acH receptor, opening a channel through which sodium ions can pass through the membrane.
  • this raises potential and triggers an action potential.
28
Q

Describe the structure of GCPRs

A

The binding site for the ligand is facing the extracellular side and the side facing the cytoplasm consists of 3 subunits (a,b,theta)

29
Q

Outline how a response is triggered through GCPRs.

A
  • Ligand binds to the binding site.
  • Conformational changes in G-protein cause GTP to replace GDP on a subunit.
  • G-protein is activated, separating it into its subunit and dissociating it from the complex.
  • Subunits cause further changes oin the cell.
30
Q

What is an example of GCP coupling:

A

Epinephrine receptors

31
Q

Where are epinephrine receptors located:

A

The plasma membrane of the target cells of epinephrine

32
Q

Outline how epinephrine causes cell activity/ creates a response:

A
  • Epinephrine binds to receptors.
  • G-protein is activated, activates adenylyl cyclase.
  • Adenylyl cyclase converts ATP into cyclic AMP.
  • Cyclic AMP initiates a series of rxns that amplify signals.
  • Responses to epi happen very rapidly inside the cell.
  • Liver cells convert glycogen to glucose within seconds of the epi signal.
33
Q

What are kinases and what do they do

A
  • Enzymes that transfer a phosphate group from ATP to a molecule (phosphorylate).
34
Q

Tyrosine kinase function

A

Transfer phosphate from adenosine triphosphate to tyrosine.

35
Q

Outline the uptake of glucose through insulin receptors:

A
  • Insulin binds.
  • 2 intracellular tyrosine kinases connect to form a dimer.
  • Each tail phosphorylates the other.
  • The insulin receptor is activated, resulting in a signal transduction pathway that causes a vesicle with glucose channels to fuse with the membrane.
  • G-channels uptake glucose into cell by facilitated diffusion.
  • Can then be used for cell respiration.
36
Q

What property of signalling molecules allows them to diffuse through cell membranes and cause a response inside of the cell?

A

Hyrophobic, insoluble

37
Q

Why do steroid hormones enter the cell?

A

They are hydrophobic and they are insoluble.

38
Q

Outline how steroid hormones effect cell activity:

A
  • steroid passes through the plasma membrane of the target cell.
  • binds to receptor protein in the cytoplasm.
  • hormone-receptor complex attaches to a position in the DNA.
  • instructions for synthesis of a polypeptide are activated.
  • polypeptide is synthesized by ribosomes and mRNA.
39
Q

What type of hormones are oestradiol and progesterone?

A

Steroid

40
Q

Which type of cells secrete Oestradiol and Progesterone in the normal cycle and during pregnancy?

A
  • Normally: cells in ovaries
  • Pregnancy: Corpus luteum and placenta.
41
Q

How does Oestradiol trigger the release of LH and FSH by the anterior pituitary gland?

A
  • Released by the ovaries.
  • Binds to receptors in the cytoplasm of cells in the hypothalamus.
  • The oestradiol-receptor complex binds to a position in the DNA that enhances the transcription of GnRH mRNA.
  • GnRH triggers the secretion of LH and FSH.
42
Q

What does progesterone do?

A

It promotes the development and maintenance of the endometrium so that it can support a fetus.

43
Q

How does progesterone thicken the endometrium?

A
  • Released by the ovary.
  • Binds to receptor proteins in the cytoplasm of cells in the uterus.
  • Progesterone-receptor complex causes the transcription of specific genes, causes cells in the endometrium to divide rapidly&raquo_space;> thickens.
44
Q

Negative feedback loop

A

End-product inhibits its production, more product leads to less production, less product leads to more.

45
Q

What is an example of a negative feedback loop?

A

Thyroxin secretion

46
Q

Outline how the secretion of thyroxin is regulated:

A
  • Cells in the hypothalamus secrete TRH.
  • TRH stimulates cells in the pituitary gland to release TSH.
  • Stimulates the thyroid gland to release thyroxin.
  • High levels of thyroxin inhibit TRH secretion in hypo and vice versa.
47
Q

Positive feedback loop

A

more product leads to more production, less to less

48
Q

Example of positive feedback loops:

A

The LH surge during the ovulatory phase of the menstrual cycle.

49
Q

Outline the positive feedback loop of Oestradiol and LH:

A

1) Follicles in the ovary release OSD.
2) Release of GnRH by the hypothalamus
3) Anterior PG releases LH.
4) Stimulates release OSD by developing follicles.
5) Rapid rise in conc of LH, follicles become mature and release eggs on day 14.

50
Q
A

Biology (20 decks)

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