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AH Biology - Unit 1 > KA 4 > Flashcards

KA 4 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Coordination Multicellular organisms signal between cells using?

A

Extracellular signalling molecules

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2
Q

What are examples of extracellular signalling molecules?

A

Steroid hormones, peptide hormones, and neurotransmitters

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3
Q

Receptor molecules of target cells are?

A

Proteins with a binding site for a specific signal molecule

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4
Q

Binding changes what of the receptor? What does this do within the cell?

A

Conformation of the receptor, which initiates a response within the cell

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5
Q

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

A

The specific receptor

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6
Q

Signalling molecules may have?

A

Different effects on different target cell types due to differences in the intracellular signalling molecules and pathways that are involved.

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7
Q

In a multicellular organism, different cell types may show a…

A

Tissue-specific response to the same signal

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8
Q

Hydrophobic signalling molecules can diffuse? And bind to?

A

Directly through the phospholipid bilayers of membranes, and so bind to intracellular receptors

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9
Q

The receptors for hydrophobic signalling molecules are?

A

Transcription factors

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10
Q

Transcription factors are?

A

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

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11
Q

The steroid hormones oestrogen and testosterone are examples of?

A

Hydrophobic signalling molecules

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12
Q

Steroid hormones bind to? In?

A

Specific receptors in the cytosol or the nucleus

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13
Q

The hormone-receptor complex moves to… Where it binds…

A

The nucleus where it binds to specific sites on DNA and affects gene expression

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14
Q

The hormone-receptor complex binds to? Called… Binding here influences?

A

Specific DNA sequences called hormone response elements (HREs).
Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes

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15
Q

Hydrophilic signalling molecules bind to… What don’t they enter?

A

Transmembrane receptors and do not enter the cytosol

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16
Q

Peptide hormones and neurotransmitters are examples of?

A

Hydrophilic extracellular signalling molecules.

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17
Q

Transmembrane receptors change? When? What happens to the signal and signal molecule?

A

Conformation when the ligand binds to the extracellular face; the signal molecule does not enter the cell, but the signal is transduced across the plasma membrane

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18
Q

Transmembrane receptors act as? What does this alter?

A

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

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19
Q

Transduced hydrophilic signals often involve?

A

G-proteins or cascades of phosphorylation by kinase enzymes

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20
Q

G-proteins relay signals from?

A

Activated receptors (receptors that have bound a signalling molecule) to target proteins such as enzymes and ion channels.

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21
Q

Phosphorylation cascades allow?

A

More than one intracellular signalling pathway to be activated

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22
Q

Phosphorylation cascades involve?

A

A series of events with one kinase activating the next in the sequence and so on.

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23
Q

Phosphorylation cascades can result in?

A

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

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24
Q

Binding of the peptide hormone insulin to its receptor results in?

A

An intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells

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25
Q

Binding of insulin to its receptor causes?

A

A conformational change that triggers phosphorylation of the receptor.

26
Q

After binding insulin to the receptor what starts?

A

A phosphorylation cascade inside the cell, which eventually leads to GLUT4-containing vesicles being transported to the cell membrane.

27
Q

Diabetes mellitus can be caused by?

A

Failure to produce insulin (type 1) or loss of receptor function (type 2)

28
Q

Type 2 is generally associated with?

A

Obesity

29
Q

Exercise also triggers recruitment of GLUT4, so can improve?

A

Uptake of glucose to fat and muscle cells in subjects with type 2

30
Q

Resting membrane potential is a?

A

State where there is no net flow of ions across the membrane

31
Q

The transmission of a nerve impulse requires?

A

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

32
Q

An action potential is?

A

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

33
Q

Neurotransmitters initiate a response by?

A

Binding to their receptors at a synapse

34
Q

Neurotransmitter receptors are?

A

Ligand-gated ion channels.

35
Q

Depolarisation of the plasma membrane as a result of? What then results?

A

The entry of positive ions triggers the opening of voltage-gated sodium channels, and further depolarisation occurs

36
Q

Depolarisation is?

A

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

37
Q

Inactivation of the sodium channels and the opening of potassium channels restores?

A

The resting membrane potential

38
Q

Binding of a neurotransmitter triggers?

A

The opening of ligand-gated ion channels at a synapse.
Ion movement occurs and there is depolarisation of the plasma membrane.
If sufficient ion movement occurs, and the membrane is depolarised beyond a threshold value, the opening of voltage-gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient.

39
Q

What does binding of a neurotransmitter cause?

A

A rapid and large change in the membrane potential. A short time after opening, the sodium channels become inactivated.

40
Q

Voltage-gated potassium channels… After binding of a neurotransmitter?

A

Open to allow potassium ions to move out of the cell to restore the resting membrane potential.

41
Q

Depolarisation of a patch of membrane causes?

A

Neighbouring regions of membrane to depolarise and go through the same cycle, as adjacent voltage-gated sodium channels are opened

42
Q

When the action potential reaches the end of the neuron it causes vesicles containing neurotransmitter to?

A

Fuse with the membrane — this releases neurotransmitter, which stimulates a response in a connecting cell

43
Q

Restoration of the resting membrane potential allows?

A

The inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane

44
Q

Ion concentration gradients are reestablished by the?

A

Sodium-potassium pump, which actively transports excess ions in and out of the cell

45
Q

Following repolarisation the sodium and potassium ion concentration gradients are?

A

Reduced

46
Q

The sodium-potassium pump restores the…

A

Sodium and potassium ions back to resting potential levels.

47
Q

The retina is the area within the eye that detects? What does it contain?

A

Light and contains two types of photoreceptor cells: rods and cones

48
Q

Rods function in?

A

Dim light but do not allow colour perception.

49
Q

Cones are responsible for?

A

Colour vision and only function in bright light.

50
Q

In animals the light-sensitive molecule retinal is combined with a? To form?

A

Membrane protein, opsin, to form the photoreceptors of the eye

51
Q

In rod cells the retinal-opsin complex is called?

A

Rhodopsin

52
Q

Retinal absorbs a?

A

Photon of light

53
Q

Rhodopsin changes conformation to?

A

Photoexcited rhodopsin

54
Q

A cascade of proteins amplifies the?

A

Signal

55
Q

Photoexcited rhodopsin activates a? What does this do?

A

Gprotein, called transducin, which activates the enzyme phosphodiesterase (PDE)

56
Q

A single photoexcited rhodopsin activates?

A

Hundreds of molecules of G-protein.

57
Q

Each activated G-protein activates one?

A

Molecule of PDE.

58
Q

PDE catalyses the hydrolysis of a molecule called?

A

Cyclic GMP (cGMP)

59
Q

Each active PDE molecule breaks down?

A

Thousands of cGMP molecules per second.

60
Q

The reduction in cGMP concentration as a result of its hydrolysis affects the? What does this result in?

A

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

61
Q

A very high degree of amplification results in?

A

Rod cells being able to respond to low intensities of light

62
Q

In cone cells, different forms of opsin combine with…

A

Retinal to give different photoreceptor proteins, each with a maximal sensitivity to specific wavelengths: red, green, blue or UV 5

AH Biology - Unit 1 (5 decks)

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