C2.1 Chemical Signalling (HL) (to check) 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
  • Indirect interactions
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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 is the process called when ligands cause a cascade of biochemical reactions?

A

Ligand binding.

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5
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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6
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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7
Q

What is the first stage of chemical signalling?

A

Synthesis and release of a ligand from a signalling cell.

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8
Q

Fill in the blank: Ligands travel through the bloodstream or by diffusion through the extracellular fluid to reach the _______.

A

[target cells]

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9
Q

What happens during receptor binding in chemical signalling?

A

Signalling molecules bind to specific receptors on the target cell.

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10
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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11
Q

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

A
  • Changes in gene expression
  • Activation or inhibition of enzymes
  • Alteration of ion channel activity
  • Modulation of cellular metabolism
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12
Q

What is the final stage of chemical signalling?

A

Signal termination.

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13
Q

True or False: The signalling molecule is always retained in the extracellular space until the signal transduction process ends.

A

False.

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14
Q

What is quorum sensing in bacteria?

A

A process where bacteria communicate to coordinate group behaviour in response to cell density.

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15
Q

What are autoinducers?

A

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

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16
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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17
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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18
Q

What is the function of the lux operon in Vibrio fischeri?

A

Regulates luminescence by encoding regulatory and luminescent proteins.

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19
Q

What chemical reaction produces light in bioluminescence?

A

The oxidation of luciferin by luciferase.

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20
Q

Fill in the blank: Quorum quenching methods can be used in the treatment of bacterial infections without the use of _______.

A

[antibiotics]

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21
Q

What potential applications does targeting quorum sensing have in the food industry?

A

Addressing food spoilage and biofilm formation.

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22
Q

What is the significance of careful examination of names and labels in knowledge acquisition?

A

To avoid oversimplification and misconceptions.

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23
Q

How can labels hinder knowledge acquisition?

A

By introducing biases and prejudices, limiting comprehensive understanding.

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24
Q

What is the effect of touching the nettle plant?

A

A stinging pain is felt due to a nerve signal traveling from the hand to the brain

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25
Q

What are chemical substances used for in the animal kingdom?

A

They act as signalling molecules to trigger different signalling pathways by activating different receptors

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26
Q

What is the role of signalling chemicals in organisms?

A

They help organisms to react to changing environments and allow fine-tuning of responses

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27
Q

What hormone is produced by the pancreas in response to high blood glucose levels?

A

Insulin

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28
Q

What hormone is produced by the pancreas in response to low blood glucose levels?

A

Glucagon

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29
Q

What are hormones?

A

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

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30
Q

What is the function of hormones?

A

They regulate the metabolic function of other cells and have prolonged effects

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31
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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32
Q

How are neurotransmitters released?

A

They are released into the synaptic cleft as a result of an action potential

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33
Q

What are cytokines?

A

Small proteins important in cell signalling related to immune response

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34
Q

Which cells primarily secrete cytokines?

A

White blood cells such as macrophages and lymphocytes

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35
Q

What role do calcium ions play in cellular signalling?

A

They can act as ligands and move in and out of the cell, activating proteins

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36
Q

What are the three main types of hormones?

A

Amines, peptide hormones, and steroids

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37
Q

What are amine hormones derived from?

A

Amino acids, specifically tyrosine and tryptophan

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38
Q

Give an example of an amine hormone.

A

Epinephrine (adrenaline)

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39
Q

What are peptide hormones?

A

Hormones in the form of polypeptide chains or small proteins

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40
Q

What is an example of a peptide hormone?

A

Insulin

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41
Q

What are steroid hormones derived from?

A

Cholesterol

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42
Q

What is the dual function of epinephrine?

A

It acts as both a hormone and a neurotransmitter

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43
Q

How do hormones induce cellular changes?

A

By binding to receptors and inducing changes in plasma membrane permeability, activating protein synthesis, and altering gene expression

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44
Q

What are the two ways hormones can act?

A

Activate second messengers or activate genes

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45
Q

What types of substances can serve as neurotransmitters?

A

Amino acids, peptides, amines, and nitrous oxide

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46
Q

Give an example of an amino acid neurotransmitter.

A

GABA (Gamma-aminobutyric acid)

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47
Q

What is the mechanism of action of neurotransmitters?

A

They are released into the synaptic cleft and bind to receptors on target cells

48
Q

How do cytokines affect target cells?

A

They bind to specific receptors and trigger signal transduction pathways that alter gene expression

49
Q

What can calcium ions trigger in cellular processes?

A

Muscle contraction, nerve impulses, and fertilisation

50
Q

What are the four types of signalling based on distance?

A
  • Autocrine signalling
  • Paracrine signalling
  • Endocrine signalling
  • Juxtacrine signalling
51
Q

What is autocrine signalling?

A

Signalling where cells secrete molecules that act on themselves

52
Q

What is paracrine signalling?

A

Signalling where molecules travel a short distance to nearby target cells

53
Q

What is endocrine signalling?

A

Signalling where hormones travel long distances via the bloodstream to target cells

54
Q

What is juxtacrine signalling?

A

Signalling that occurs when two cells are in physical contact

55
Q

What are cell-surface receptors?

A

Receptors present on the cell membrane that transmit signals from outside to inside the cell

56
Q

What are intracellular receptors?

A

Receptors located inside the cell that bind to lipid-derived signalling molecules

57
Q

What are the three domains of a typical cell-surface receptor?

A
  • Extracellular ligand-binding domain
  • Transmembrane hydrophobic domain
  • Intracellular domain
58
Q

What do intracellular receptors do upon ligand binding?

A

They form a hormone-receptor complex that can move to the nucleus to affect gene expression

59
Q

What are Type I intracellular receptors?

A

Cytoplasmic receptors that translocate to the nucleus upon ligand binding

60
Q

What are Type II intracellular receptors?

A

Nuclear receptors directly involved in gene transcription

61
Q

What happens when a ligand binds to a cell-surface receptor?

A

An intracellular signal is generated which may get amplified

62
Q

Name the three categories of cell-surface receptors.

A
  • Enzyme-linked receptors
  • G-protein-linked receptors
  • Ion channel-linked receptors
63
Q

What amino acids are typically found in transmembrane receptors?

A

Hydrophobic amino acids like phenylalanine, leucine, isoleucine, and others

64
Q

What is the main difference between hydrophobic and hydrophilic signalling molecules?

A

Hydrophobic signalling molecules can diffuse across the cell membrane, while hydrophilic ones cannot

65
Q

What is the first step in the signal transduction process?

A

Receptor activation

Receptors get activated when specific ligands bind to them.

66
Q

What does signal amplification refer to in the context of signal transduction?

A

A process where a small signal triggers a larger response through activation of downstream messengers/effectors

Hormones or neurotransmitters can activate protein kinases, amplifying the signal.

67
Q

What is a common second messenger in signal transduction?

A

Cyclic AMP (cAMP)

cAMP plays a crucial role in relaying signals inside cells.

68
Q

What is the function of protein kinases in signal transduction?

A

To phosphorylate proteins by adding a phosphate group

Protein kinases remain inactive until activated by second messengers like cAMP.

69
Q

What are the potential outcomes of changes in gene expression or cellular function during signal transduction?

A

Altering gene expression, opening/closing ion channels, activating enzymes

These changes ultimately lead to a modification in cellular behavior.

70
Q

How is the signal terminated in signal transduction?

A

By degradation, diffusion, reuptake, inactivation of receptors, or feedback inhibition

For example, acetylcholinesterase degrades acetylcholine to terminate its action.

71
Q

What are the three types of neurotransmitters based on their effects?

A
  • Excitatory neurotransmitters
  • Inhibitory neurotransmitters
  • Modulatory neurotransmitters

Examples of excitatory neurotransmitters include glutamate; inhibitory neurotransmitters include GABA.

72
Q

What is the role of acetylcholine at the neuromuscular junction?

A

Regulates muscle contractions and other functions like heartbeat and blood pressure

Acetylcholine is the primary neurotransmitter associated with motor neurons.

73
Q

What happens when an action potential reaches the axon terminal?

A

It depolarizes the membrane and opens voltage-gated Na+ channels

This depolarization is crucial for neurotransmitter release.

74
Q

What are G proteins and their function in signal transduction?

A

Molecular switches that undergo conformational changes when GPCRs bind to ligands

They facilitate GDP/GTP exchange within the cell.

75
Q

How many subunits do G proteins consist of?

A

Three subunits: ɑ, β, and γ

Inactive G proteins have the ɑ subunit bound to GDP.

76
Q

What is the structure of a typical G protein-coupled receptor (GPCR)?

A

Has seven transmembrane ɑ helices

GPCRs are the largest class of membrane receptors found in eukaryotes.

77
Q

Fill in the blank: The binding of a ligand to a receptor induces a _______ change.

A

conformational

This change activates the receptor’s intracellular domain.

78
Q

True or False: The ultimate response of the cell to a signal is independent of the type of receptor involved.

A

False

The response depends on the type of receptor, nature of the signal, and downstream effectors.

80
Q

What is epinephrine also known as?

A

Adrenaline

81
Q

What hormone is secreted by the adrenal glands in response to stress or danger?

A

Epinephrine

82
Q

What are the two major outcomes of protein kinase A activation by epinephrine?

A
  • Inhibition of glycogen synthesis
  • Initiation of glycogen breakdown
83
Q

What does cAMP stand for?

A

Cyclic AMP

84
Q

What role does cAMP play in the cell?

A

Acts as a second messenger

85
Q

What is the function of adenylate cyclase in the presence of epinephrine?

A

Converts ATP to cAMP

86
Q

What type of receptors are involved in the mechanism of action of epinephrine?

A

G protein-coupled receptors (GPCRs)

87
Q

What happens to GDP when epinephrine binds to its receptor?

A

GDP is replaced by GTP

88
Q

What is the effect of protein kinase A activation in the liver?

A

Activates phosphorylase, breaking down glycogen to glucose

89
Q

What are tyrosine kinase receptors involved in?

A

Cell growth, differentiation, and proliferation

90
Q

What is the role of insulin in glucose homeostasis?

A

Increases glucose uptake and reduces glucose synthesis in the liver

91
Q

What is the structure of the insulin receptor?

A

A dimer consisting of alpha(ɑ) and beta(β) subunits

92
Q

What process does tyrosine kinase undergo upon insulin binding?

A

Autophosphorylation

93
Q

What does the activation of IRS proteins lead to?

A

Activation of downstream signalling pathways

94
Q

What is GLUT-4?

A

A glucose receptor embedded in the cell membrane

95
Q

What type of receptors do steroid hormones bind to?

A

Intracellular (nuclear) receptors

96
Q

What happens when oestradiol binds to its receptor?

A

Dimerisation of the receptor-hormone complex

97
Q

What does oestradiol enhance in the hypothalamus?

A

Secretion of gonadotropin-releasing hormone (GnRH)

98
Q

What are the two hormones released by the anterior pituitary gland due to GnRH?

A
  • Follicle-stimulating hormone (FSH)
  • Luteinising hormone (LH)
99
Q

What is the main role of progesterone in the reproductive system?

A

Maintaining the menstrual cycle

100
Q

What effect does progesterone have on endometrial cells?

A

Causes differentiation and prepares for possible implantation

101
Q

What happens to progesterone levels if pregnancy does not occur?

A

Progesterone levels decline, leading to shedding of the endometrial lining

102
Q

What is the tendency of all systems in nature?

A

To attain balance

This concept is often referred to as homeostasis in biological systems.

103
Q

How does a thermoregulated waterbath maintain equilibrium?

A

The thermostat cuts off heating when the set temperature is reached and switches on when the temperature drops below the set point

104
Q

What role do feedback loops play in living organisms?

A

They connect output signals back to their inputs to maintain a balanced internal environment

105
Q

What are the two critical components of feedback mechanisms in regulating signalling pathways?

A
  • Positive feedback
  • Negative feedback
106
Q

What is homeostasis?

A

The maintenance of a stable internal environment in living organisms

107
Q

What is the significance of chemical signalling in microorganisms?

A

It regulates growth and mediates communication with the environment

108
Q

What does ‘drug resistance’ mean in the context of pathogenic microorganisms?

A

Some microorganisms undergo random mutations that allow survival in the presence of drugs

109
Q

Why is drug resistance considered a serious threat?

A

It poses risks to both immunosuppressed and immunocompetent individuals

110
Q

What is the effect of positive feedback mechanisms in cell signalling?

A

They result in amplification of cell signals

111
Q

Give an example of a process governed by positive feedback mechanisms.

A

Blood clotting, where activated platelets release chemicals to activate nearby platelets

112
Q

What is the role of negative feedback in cell signalling pathways?

A

It inhibits upstream activation, dampening the amplification of signals

113
Q

How does insulin function in regulating blood glucose levels?

A

Insulin is secreted when blood glucose rises, promoting glucose uptake, and its release is inhibited when glucose levels fall

114
Q

What do positive and negative feedback loops form the foundation of?

A

The cellular signalling pathway

115
Q

What happens to reactions in the signalling process based on the type of signal they receive?

A

They are constantly turned on or off