Unit 1.4 - Detecting and Amplifying Flashcards

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1
Q

What do organisms use light energy for?

A

Generating ATP

Detect changes in their enviroment

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2
Q

What prosthetic group is present in rhodopsin?

A

Retinal

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3
Q

Where does retinal absorb energy from?

A

Photons

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4
Q

Where do the hydrogen ions diffuse back through?

A

ATP Synthase

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5
Q

What is retinal?

A

Prosthetic group covalently bonded to polypeptide called opsin

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6
Q

What are the two classes of photoreceptor cells found in the retina of vertebrates?

A

Cone and Rod cells

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7
Q

What do cone cells contain?

A

Photopsins

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8
Q

Which class of photoreceptor cells is responsible for colour vision?

A

Cone cells

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9
Q

Why are cone cells less sensitive than rod cells?

A

They have about 1000x less photoreceptor molecules

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10
Q

How many types of photopsins are found in human cells?

A

3

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11
Q

What are the colours each type of photopsin have maximal sensitivity to?

A

Red, blue and green

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12
Q

How are different photopsins formed?

A

Combining retinal with different forms of opsins

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13
Q

What do Rod cells produce when no light has been absorbed?

A

Cylic GMP

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14
Q

Where does cGMP bind to?

A

Ligand gated Na+ channels

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15
Q

What happens when a photon of light is absorbed by a retinal molecule?

A

Conformational change in rhodopsin

Activates hundreds of G proteins which activates hundred of enzymes

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16
Q

What do the enzymes do when activated by G proteins?

A

Catalyse breakdown of cGMP

17
Q

What does the breakdown of cGMP cause?

A

Na channels close
Membrane will become hyperpolarized
Nerve impulse is generated

18
Q

What provides a high degree of amplification?

A

Protein cascade

19
Q

What are the steps in the protein cascade?

A

Rhodopsin
G proteins
Enzymes
Channels

20
Q

What is a photoreceptor?

A

Name given to proteins which are capable of sensing and responding to light