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AH Biology > Unit 1: KA4 - Communication and Signalling > Flashcards

Unit 1: KA4 - Communication and Signalling Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does communication in multicellular organisms involve?

A

Producing extracellular signalling molecules.

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2
Q

What effect does binding with a receptor have?

A

A conformational change in the receptor, which initiates a response within the cell.

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3
Q

What must cells possess to detect a signal?

A

A specific receptor.

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4
Q

Describe the term ‘tissue-specific response’

A

In a multicellular organism, different cell types may respond differently to the same signal molecule.

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5
Q

How do Hydrophobic signals bind to receptors?

A

Hydrophobic signal molecules diffuse through the phospholipid bilayer and bind with specific receptors in the cytosol or the nucleus to form the hormone-receptor complex.

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6
Q

Name the receptors for a hydrophobic signalling molecule.

A

Transcription factors.

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7
Q

What are transcription factors?

A

Proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.

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8
Q

Name examples of hydrophobic signalling molecules.

A

Steroid hormones: Estrogen and Testosterone

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9
Q

What happens after the formation of the hormone-receptor complex?

A

It moves to the nucleus, where it binds to specific sites on DNA, influencing transcription.

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10
Q

What parts of DNA does the hormone-receptor complex bind to?

A

Hormone Response Elements (HREs)

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11
Q

How do hydrophilic signalling molecules bind to receptors?

A

Hydrophilic signalling molecules bind to transmembrane receptors and do not enter the cytosol.

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12
Q

Name examples of hydrophilic signalling molecules.

A

Peptide hormones

Neurotransmitters.

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13
Q

What happens to receptors after binding with hydrophilic signalling molecules?

A

A conformational change in the transmembrane protein.

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14
Q

How do transmembrane receptors act as signal transducers?

A

Transmembrane receptors act as signal transducers by converting the extracellular ligandbinding event into intracellular signals, which alters the behaviour of the cell.

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15
Q

What do transduced hydrophilic signals often involve?

A

G proteins

Cascades of phosphorylation by kinase enzymes

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16
Q

What is the function of G-proteins?

A

To relay signals from activated receptors to target proteins.

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17
Q

What is the function of a phosphorylation cascade?

A

To allow more than one intracellular signalling pathway to be activated (amplified signal).

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18
Q

What is the function of the peptide hormone insulin?

A

To create an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter to the membrane of fat and muscle cells.

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19
Q

Describe the differences in diabetes types.

A

Type one is caused by the failure to produce insulin.

type two is caused by the loss of receptor function.

20
Q

Which diabetes type is generally associated with obesity?

A

Type two

21
Q

What does exercise do for those with type 2 diabetes?

A

Can trigger the recruitment of GLUT4, therefore improving glucose uptake in fat and muscle cells.

22
Q

What is resting membrane potential?

A

Resting membrane potential is a state where there is no net flow of ions across the membrane.

23
Q

What is required for the transmission of a nerve impulse?

A

Changes in the membrane potential of the neuron’s membrane.

24
Q

Define the term action potential.

A

An action potential is a wave of electrical excitation along a neuron’s plasma membrane.

25
Q

What happens between neurons transmitting a signal?

A

When the action potential reaches the end of the neuron it causes vesicles containing neurotransmitters to fuse with the membrane — this releases neurotransmitters which stimulate a response in a connecting cell.

26
Q

What is depolarisation?

A

The change in the membrane potential to a less negative value inside.

27
Q

What is the result of depolarisation from the neurotransmitter?

A

Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the opening of voltage-gated sodium channels, and further depolarisation occurs.

28
Q

What does a neurotransmitter do?

A

It binds to a ligand gated channel causing it to open and allowing ions to enter, depolarising the membrane.

29
Q

How does the signal travel along a neuron?

A

Depolarisation of a patch of membrane causes neighbouring regions of membrane to depolarise and go through the same cycle, as adjacent voltage-gated sodium channels are opened.

30
Q

How is the resting membrane potential restored?

A

The sodium channels are deactivated after a short time, and voltage gated potassium channels are opened and potassium ions move out of the neuron.

31
Q

What does restoring the resting membrane potential allow?

A

This allows the inactivated sodium channels to return to a confirmation which allows them to be activated again.

32
Q

How are ions gradients re-established after repolarisation?

A

Sodium potassium pump.

33
Q

Which area of the eye detects light?

A

Retina

34
Q

What type of cells does the retina contain?

A

Two types of photoreceptor cells:

  • Rod Cells
  • Cone Cells
35
Q

What do Rod cells do?

A
  • Sensitive to changes in light intensity

- Function in low light

36
Q

What do Cone cells do?

A
  • Only function in bright light

- Particularly sensitive to specific colours/wavelengths

37
Q

What is retinal?

A

The light sensitive prosthetic group.

38
Q

What are the photoreceptors of the eye made of?

A

Retinal is the prosthetic group covalently bonded to a membrane protein called opsin.

39
Q

What is the photoreceptor in rod cells called?

A

rhodopsin

40
Q

What happens once Retinal absorbs a photon of light?

A

Rhodopsin changes conformation to become ‘photoexcited rhodopsin’ and a cascade of G proteins amplify the signal.

41
Q

What G proteins are activated by photoexcited rhodopsin?

A

Transducins

42
Q

What enzyme does a single transducin activate?

A

Phosphodiesterase

43
Q

What is Phosphodiesterase’s function?

A

PDE catalyses the hydrolysis of cyclic GMP molecules, resulting in the closure of ion channels, causing a nerve impulse.

44
Q

What gives rod cells high sensitivity at low levels of light?

A

high degrees of amplification

45
Q

In what way are cone cells different?

A

Retinal combines with different forms of opsin to give photoreceptor proteins for specific wavelengths of light

AH Biology (13 decks)

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