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AH Biology > 1.4dii - Initiation of a Nerve Impulse in Response to an Environmental Stimulus: The Vertebrate Eye > Flashcards

1.4dii - Initiation of a Nerve Impulse in Response to an Environmental Stimulus: The Vertebrate Eye Flashcards

1
Q

The retina is…

A

the area within the eye that detects light

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2
Q

The retina contains…

A

2 types of photoreceptor cells: rods and cones

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3
Q

Rods function in…

A

dim light, but do not allow colour perception

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4
Q

Cones only function in…

A

bright light

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5
Q

Cones are responsible for…

A

colour vision

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6
Q

What forms the photoreceptors of the eye in animals?

A

the light-sensitive molecule retinal which is combined with a membrane protein opsin

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7
Q

What is rhodopsin?

A

the retinal-opsin complex in rod cells

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8
Q

Retinal absorbs…

A

a photon of light

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9
Q

Rhodopsin changes…

A

conformation to photoexcited rhodopsin

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10
Q

A cascade of proteins amplifies…

A

the signal

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11
Q

Photoexcited rhodopsin activates a G-protein called…

A

transducin

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12
Q

Transducin activates…

A

the enzyme phosphodiesterase (PDE)

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13
Q

A single photoexcited rhodopsin activates…

A

hundred of molecules of G-proteins

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14
Q

Each activated G-protein activates…

A

one molecule of PDE

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15
Q

Each activated G-protein activates…

A

one molecule of PDE

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16
Q

PDE catalyses the…

A

hydrolysis of a molecule called cyclic GMP (cGMP)

17
Q

Each active PDE molecule…

A

breaks down thousands of cGMP molecules per second

18
Q

The reduction in cGMP concentration as a result of its hydrolysis…

A

affects the function of ion channels in the membrane of rod cells, resulting in the closure of ion channels in the membrane of rod cells

19
Q

The closure of ion channels in the membrane of rod cells triggers…

A

nerve impulses in the neurons in the retina

20
Q

The reduction in cGMP concentration as a result of its hydrolysis…

A

affects the function of ion channels in the membrane of rod cells, resulting in the closure of ion channels in the membrane of rod cells

21
Q

A very high degree of amplification results in…

A

rod cells being able to respond to low intensities of light

22
Q

In cone cells, different forms of…

A

opsin combine with retinal to give different photo-receptor proteins

23
Q

Each photo-receptor protein has…

A

a maximal sensitivity to specific wavelengths, red, blue, green and UV

AH Biology (34 decks)

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