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Adv Bio Unit 1 > 1.4- Communication > Flashcards

1.4- Communication Flashcards

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Biology 101 flashcards
1
Q

Multicellular organisms signal between cells using…

A

extracellular signalling molecules

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2
Q

Examples of extracellular signalling molecules

A

steroid hormones, peptide hormones, neurotransmitters

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3
Q

In animals, communication occurs through …… and …..

A

nerve transmission and hormonal secretion

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4
Q

Receptor molecules of target cells are proteins with a …

A

binding site for a specific signal molecule.

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5
Q

Binding changes the…….. of the receptor, which initiates a response within the cell.

A

conformation

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6
Q

Different cell types produce specific signals which can only be detected and responded to by cells with the

A

specific receptor.

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7
Q

Signalling molecules may have different effects on different target cell types due to differences in the…

A

intracellular signalling molecules and pathways that are involved.

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8
Q

In a multicellular organism, different cell types may show a …….. to the same signal.

A

tissue-specific response

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9
Q

Can hydrophobic signals diffuse directly through the phospholipid bilayers of membranes.

A

yes

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10
Q

hydrophobic signals bind to ……. receptors

A

intracellular

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11
Q

The receptors for hydrophobic signalling molecules are

A

transcription factors.

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12
Q

(hydrophobic) Transcription factors are

A

proteins that when bound to DNA can either stimulate or inhibit initiation of transcription.
They can enhance or block the binding of RNA polymerase to specific genes

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13
Q

Examples of hydrophobic signals

A

Thyroxine

Steroid hormones

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14
Q

Thyroxine (hydrophobic)

A
  • produced by the thyroid

- regulates the rate of metabolism

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15
Q

Examples of steroid hormones (hydrophobic)

A

testosterone and oestrogen

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16
Q

(hydrophobic) Steroid hormones bind to specific receptors in the …….. or the ……. forming a hormone-receptor complex.

A

cytosol or nucleus

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17
Q

(hydrophobic) Steroid hormones bind to specific receptors in the cytosol or the nucleus forming a

A

hormone-receptor complex.

The hormone-receptor complex moves to the nucleus where it binds to specific sites on DNA.

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18
Q

(hydrophobic) The specific DNA sequences that the hormone-receptor complex binds to are called

A

hormone response elements (HREs).

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19
Q

Binding at hormone response elements influences the rate of…

A

transcription, with each steroid hormone affecting the gene expression of many different genes.

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20
Q

Hydrophilic signalling molecules bind to ……….. and do not enter the

A

bind to transmembrane receptors and do not enter the cytosol.

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21
Q

Examples of hydrophilic molecules

A

peptide hormones and neurotransmitters

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22
Q

Who don’t hydrophilic molecules enter the cytosol?

A

they are not capable of passing across the hydrophobic plasma membrane.

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23
Q

Process of hydrophilic molecules

A
  1. Reception - Signalling molecule binds to transmembrane receptor
  2. Transduction – signal is passed through the cell
  3. Response - will vary depending on the signal
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24
Q

Transmembrane receptors change conformation when the ligand binds to the extracellular face. Does the signal molecule enter the cell?

A

the signal molecule does not enter the cell.

The signal is then transduced across the plasma membrane.

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25
Q

Transmembrane receptors act as

A

signal transducers

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26
Q

Transmembrane receptors act as signal transducers by

A

converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell.

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27
Q

Transduced hydrophilic signals often involve:

A

G-proteins

Cascades of phosphorylation by kinase enzymes.

28
Q

What do G proteins do? (hydrophilic)

A
  • G-proteins relay signals from activated receptors (receptors that have bound a signalling molecule) to target proteins such as enzymes and ion channels.
  • Enzymes will then catalyse reactions within the cell.
  • Ion channels will then either open or close to control ion movement.
29
Q

Cascades of phosphorylation

A

Phosphorylation cascades involve a series of events with one kinase activating the next in the sequence and so on

30
Q

Phosphorylation cascades can result in the

A

phosphorylation of many proteins as a result of the original signalling event.

31
Q

Phosphorylation cascades allow more than one

A

intracellular signalling pathway to be activated.

32
Q

Two hormones involved in the control of glucose in the blood

A

insulin and glucagon

33
Q

Describe the hormone insulin (4)

A
  • made when there’s an increase in blood glucose concentration
  • made by cells in the pancreas
  • hydrophilic peptide hormone
  • allows fat tissue & skeletal muscles to absorb glucose from the bloodstream
34
Q

Glucose passes into cells by travelling through a transporter protein called …….. by facilitated diffusion

A

GLUT4

35
Q

Process of insulin binding

A

Insulin binds to its receptor.
Receptor undergoes a conformational change that triggers phosphorylation of the receptor.
A phosphorylation cascade is started inside the cell.
Vesicles containing GLUT4 are transported to the cell membrane.
Glucose passes through the GLUT4 transporters.

36
Q

Describe Type 1 Diabetes (3)

A
  • caused by a failure to produce insulin in the pancreas
  • treated with injections of insulin throughout the day
  • sometimes called insulin dependent diabetes mullitus (IDDM)
37
Q

Describe Type 2 Diabetes (4)

A
  • caused by loss of insulin receptor function (associated with obesity)
  • can be treated with medication to lower blood glucose levels along with lifestyle changes
  • exercise triggers the recruitment of GLUT4 so can improve uptake of glucose to fat and muscle
  • sometimes called non-insulin dependent diabetes mellitus (NIDDM)
38
Q

All cells have an ……………………. across their plasma membrane.

A

electrical potential difference (voltage)

39
Q

Membrane potential

A

when there is a difference in electrical charge on the two sides of the membrane
The minus sign means that the inside of the cell is negative relative to the outside.

40
Q

Two parts of a neuron

A

dendrite and axon

41
Q

Resting membrane potential

A

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

42
Q

The transmission of a nerve impulse requires changes in the ……………… of the neuron’s plasma membrane

A

membrane potential

43
Q

An action potential

A

a wave of electrical excitation along a neuron’s plasma membrane

44
Q

Neurotransmitters initiate a response by binding to their……… at a ………

A

binding to their receptors at a synapse

45
Q

Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the
opening of

A

voltage-gated sodium channels, and further depolarisation occurs

46
Q

What restores the resting membrane potential?

A

Inactivation of the sodium channels and the opening of potassium channels

47
Q

What causes a wave of depolarisation when a nerve cell is transmitting a signal?

A

the opening of voltage-gated Na+ channels and influx of Na+

48
Q

What re-establishes the resting potential of a nerve cell after depolarisation?

A

closing of voltage-gated Na+ channels and the opening of K+ channels, K+ moving out of the cell.

49
Q

Two types of photoreceptor cells in the retina

A

rods and cones

50
Q

Describe Rod Cells (retina)

A

sensitive to changes in light intensity.

They are useful for vision in areas of low light intensity, e.g. a dim room.

51
Q

Describe Cone Cells (retina)

A

not as sensitive to light as rod cells.
They are particularly sensitive to specific colours (wavelengths) of light: green, red, blue and (in some animals) UV.
Cone cells allow animals to have colour vision.

52
Q

Retina

A

the area within the eye that detects light

53
Q

In rod cells the retinal-opsin complex is called

A

rhodopsin

54
Q

Retinal absorbs a………..

rhodopsin changes conformation to…….

A

Retinal absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin

55
Q

Photoexcited rhodopsin activates a G-Protein called……

A

transducin

56
Q

Photoexcited rhodopsin activates a G-protein, called transducin, which activates the enzyme…

A

phosphodiesterase (PDE)

57
Q

PDE catalyses the hydrolysis of a molecule called

A

cyclic GMP (cGMP)

58
Q

PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP). What does this result in?

A

the closure of ion channels in the membrane of the rod cells, which triggers nerve impulses in neurons in the retina

59
Q

A very high degree of amplification results in rod cells being able to respond to

A

low intensities of light

60
Q

In cone cells, different forms of ……… combine with retinal to give different photoreceptor proteins, each with a maximal sensitivity to specific …….

A

In cone cells, different forms of opsin combine with retinal to give different photoreceptor
proteins, each with a maximal sensitivity to specific wavelengths: red, green, blue or UV

61
Q

Can hydrophobic signalling molecules diffuse directly through the phospholipid bilayers?

A

yes

62
Q

Why do hydrophilic signal molecules need their receptor in the plasma membrane?

A

they cannot cross the hydrophobic plasma membrane

63
Q

Name one example of signal transduction pathways that can occur when a hydrophilic molecule binds to a receptor.

A

activation of G-protein or phosphorylation

64
Q

Name the channel protein that is recruited to the cell membrane of muscle cells by the binding of insulin.

A

GLUT4

65
Q

Give one difference between type 1 and type 2 diabetes.

A

1 = no insulin, injections. 2 = receptor insensitivity, obesity, diet and exercise

66
Q

Process of Nerve Transmission

A
  1. Neurotransmitters initiate a response by binding to their receptors at a synapse
  2. 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
  3. Inactivation of the sodium channels & the opening of potassium channels restores the membrane resting potential
  4. 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 open
  5. When the action potential reaches the end of the neuron it causes vesicles containing neurotransmitter to fuse with the membrane- releasing neurotransmitter, stimulating a response in a connecting cell.
  6. Restoration of the resting membrane potential allows the inactive voltage-gated sodium channels to form a conformation, allowing them to open again.
  7. Ion concentration gradients are re-established by the sodium-potassium pump, which actively transports excess ions in and out of the cell

Adv Bio Unit 1 (6 decks)

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