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Adv Bio Unit 1 > 1.4- Communication > Flashcards

1.4- Communication 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
Transmembrane receptors act as
signal transducers
26
Transmembrane receptors act as signal transducers by
converting the extracellular ligand-binding event into intracellular signals, which alters the behaviour of the cell.
27
Transduced hydrophilic signals often involve:
G-proteins | Cascades of phosphorylation by kinase enzymes.
28
What do G proteins do? (hydrophilic)
- 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
Cascades of phosphorylation
Phosphorylation cascades involve a series of events with one kinase activating the next in the sequence and so on
30
Phosphorylation cascades can result in the
phosphorylation of many proteins as a result of the original signalling event.
31
Phosphorylation cascades allow more than one
intracellular signalling pathway to be activated.
32
Two hormones involved in the control of glucose in the blood
insulin and glucagon
33
Describe the hormone insulin (4)
- 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
Glucose passes into cells by travelling through a transporter protein called ........ by facilitated diffusion
GLUT4
35
Process of insulin binding
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
Describe Type 1 Diabetes (3)
- 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
Describe Type 2 Diabetes (4)
- 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
All cells have an ......................... across their plasma membrane.
electrical potential difference (voltage)
39
Membrane potential
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
Two parts of a neuron
dendrite and axon
41
Resting membrane potential
a state where there is no net flow of ions across the membrane
42
The transmission of a nerve impulse requires changes in the .................. of the neuron's plasma membrane
membrane potential
43
An action potential
a wave of electrical excitation along a neuron’s plasma membrane
44
Neurotransmitters initiate a response by binding to their......... at a .........
binding to their receptors at a synapse
45
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
46
What restores the resting membrane potential?
Inactivation of the sodium channels and the opening of potassium channels
47
What causes a wave of depolarisation when a nerve cell is transmitting a signal?
the opening of voltage-gated Na+ channels and influx of Na+
48
What re-establishes the resting potential of a nerve cell after depolarisation?
closing of voltage-gated Na+ channels and the opening of K+ channels, K+ moving out of the cell.
49
Two types of photoreceptor cells in the retina
rods and cones
50
Describe Rod Cells (retina)
sensitive to changes in light intensity. | They are useful for vision in areas of low light intensity, e.g. a dim room.
51
Describe Cone Cells (retina)
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
Retina
the area within the eye that detects light
53
In rod cells the retinal-opsin complex is called
rhodopsin
54
Retinal absorbs a........... | rhodopsin changes conformation to.......
Retinal absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin
55
Photoexcited rhodopsin activates a G-Protein called......
transducin
56
Photoexcited rhodopsin activates a G-protein, called transducin, which activates the enzyme...
phosphodiesterase (PDE)
57
PDE catalyses the hydrolysis of a molecule called
cyclic GMP (cGMP)
58
PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP). What does this result in?
the closure of ion channels in the membrane of the rod cells, which triggers nerve impulses in neurons in the retina
59
A very high degree of amplification results in rod cells being able to respond to
low intensities of light
60
In cone cells, different forms of ......... combine with retinal to give different photoreceptor proteins, each with a maximal sensitivity to specific .......
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
Can hydrophobic signalling molecules diffuse directly through the phospholipid bilayers?
yes
62
Why do hydrophilic signal molecules need their receptor in the plasma membrane?
they cannot cross the hydrophobic plasma membrane
63
Name one example of signal transduction pathways that can occur when a hydrophilic molecule binds to a receptor.
activation of G-protein or phosphorylation
64
Name the channel protein that is recruited to the cell membrane of muscle cells by the binding of insulin.
GLUT4
65
Give one difference between type 1 and type 2 diabetes.
1 = no insulin, injections. 2 = receptor insensitivity, obesity, diet and exercise
66
Process of Nerve Transmission
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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