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AH Biology > Unit 1 KA4 > Flashcards

Unit 1 KA4 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

(a)

How do multicellular organisms singal between cells?

Give examples too

A

They use extracellular signalling molecules
* steroid
* peptide
* neurotransmitters

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2
Q

(a)

What are receptor molecules of target cells?

A

Proteinds with a specific binding site for a specific signal molecule

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3
Q

(a)

What does binding do and what is the impact of it to a receptor

A

It changes conformation of receptor which initiates a response within the cell

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4
Q

(a)

What is the implication of different cells producing specific signals for a receptor?

A

They can only be detected and responded to by cells with the specific receptor attached

Signalling molecules may have different effects on different targets cell types due to differences in the intracellular signalling molecules and pathways involved

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5
Q

In response to the same signal what may different cell types show?

A

a tissue specific response to the same signal

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6
Q

(b)

How do hydrophobic signalling molecules bind to intracellular receptors?

A

Can diffuse directly through the phospholipid bilayers (as they are also hydrophobic)

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7
Q

(b)

Transcription factors

Definition

A

hydrophobic singalling molecules
proteins that when bound to DNA can either stimulate or inhibit initiation of transcription

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8
Q

(b)

Examples of hydrophobic signalling molecules

A

Oestrogen
Testosterone

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9
Q

(b)

Where to steroid hormones bind to specific receptors?

A

cytosol or nucleus

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10
Q

(b)

What happens to the hormone receptor complex when it moves to the nucleus?

A

It binds to specific sites on DNA (HREs) and affects gene expression
binding at these sites affects rate of transcription
steroid binding effects gene expression of many genes

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11
Q

(b)

What are HREs?

A

Hormone Response elements
(specific DNA sequences that hormone receptor complex binds to)

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12
Q

(c)

What do hydrophilic signalling molecules bind to and do not enter?

A

bind to transmembrane receptors
do not enter the cytosol

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13
Q

(c)

What are examples of hydrophobic extracellular signalling molecules?

A

Peptide hormones
Neurotransmitters

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14
Q

(c)

What happens to a transmembrane receptor when a ligand binds to extracellular face?

A

changes conformation

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15
Q

(c)

What happens after the ligand binds to extracellular face?

A
  1. signal molecule does not enter the cell
  2. signal is transduced across the plasma membrane
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16
Q

What do transmembrane receptors act as?

A

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

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17
Q

(c)

What do transduced hydrophillic signals often involve?

A

G-proteins or cascades of phosphorylation by kinase enzymes

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18
Q

(c)

What do G-proteins do?

A

relay signals from activated receptors (r are bound to a sig. mol.) to target proteins such as enzymes and ion channels

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19
Q

What do phosphorylation cascades allow?

A

allow more than one intracellular signalling pathway to be activated

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20
Q

(c)

What do phosphorylation cascades involve?

and what do they result in

A
  • one kinase activates the next in the sequence
  • can result in the phosphorylation of many proteins as a result of the original signalling event
21
Q

(c)

What does the binding of the peptide hormone insulin result in?

A
  1. causes conformational change that triggers phosphorylation of receptor
  2. Intracellular signalling cascade that triggers recruitment of GLUT4 (glucose transporter proteins)
  3. Starts a cascade that leads to GLUT4 containing vesicles being transported to cell membrane
22
Q

(c)

In relation to receptors
Type 1 Diabetes
Type 2 Diabetes

A

Type 1 - failure to produce insulin
Type 2- loss of receptor function

23
Q

(c)

Type 2 diabetes

Association and What and why improves condition

A
  • associated with obesity
  • exercise triggers recruitment of GLUT4 can improve uptake of glucose to fat and muscle cells
24
Q

(di)

What is Resting Membrane Potential?

A

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

25
Q

What does the transmission of a nerve impulse require?

A

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

26
Q

di)

What is action potential?

A

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

27
Q

di

How do neurotransmitters initiate a response?

A

binding to their receptors at a synapse

28
Q

di

What type of receptors are neurotransmitters?

A

Ligand-gated ion channels

29
Q

di

How is the opening of voltage-gated sodium channels triggered?

A

Via depolarisation of the plasma membrane as a result of the entry of +ve ions
after the opening further depolarisation occurs

30
Q

di

What is depolarisation?

A

a change in the membrane potential to a less negatie value inside

31
Q

di

What restores the resting membrane potential?

A

Inactivation of the sodium channels and opening of potassium channels

32
Q

di

What does the binding of a neurotransmitter trigger?

A
  1. the opening of ligand-gated ion channels at a synapse
  2. ion movement occurs
  3. depolarisation of plasma mem
  4. opening of sodium ions enter cell down electro chem gradient
  5. rapid and large change in membrane potenital
  6. quickly after Na channels inactivate
  7. Voltage gated K channels allow K+ to ove out
  8. restores membrane resting potential
33
Q

di

What does depolarisation of a patch od membrane cause?

A

Causes neighbouring regios of membrane to depolarise and go through same cycle as adjacent voltage-gated Na channels are opened

34
Q

di

What happens when the action potential reaches the end f the neuron?

A

causes vesicles containing neurotransmitter to fuse with the membrane
releases neurotransmitter which stimulates a response in a connecting cell

35
Q

di

What does the restoration of the resting membrane potential allow?

A

Allows the inactive voltage gated Na channels to return to a conformation that allows them to open in response to depolarisation of the membrane

36
Q

di

How are ion conc. gradients re-established?

A

By the Na-K pump which actively transports excess ions in and out of the cell

37
Q

di

Following repolarisation what happens to the Na+ and K+ conc. gradient?

A

they are reduced

38
Q

di

What restores the Na K ions back to resting potential?

A

The Na-K pump

39
Q

dii

Retina

A

Area within the eye that detects light
contains 2 types of photoreceptor cells:rods and cones

40
Q

dii

Rods

function

A

function in dim light
do not allow colour perception

41
Q

dii

Cones

function

A

Responsible for colour vision
only function in bright light

42
Q

dii

In animals what components form the photoreceptors of the eye

A
  • light-sensitive molecule retinal
  • membrane protein opsin
43
Q

dii

Rhodopsin

A

In rod cells the retinal opsin complex is called this

44
Q

dii

What does Retinal do wen it absorbs a photon of light?

A
  1. Rhodopsin changes conformation to photoexcited rhodopsin
  2. a cascade of protein amplifies the signal
  3. photoexcited rhodopsin activates a transducin (G-protein) (1r->100s G)
  4. activates PDE (1G->1PDE)
  5. PDE catalyses the hydrolysis of a molecule called cGMP (PDE —> 1000s cGMP/s)
  6. results in closure of ion channels in membrane of rod cells, triggers nerve impulses in neurons of retina
45
Q

dii

What affects the function of ion channels in the membranes of rod cells?

A

Reduction in cGMP conc. (result of hydrolysis)

46
Q

dii

What results in rod cells being able to respond to low intensities of light?

A

A very high degree of amplification

47
Q

dii

Where do different forms of opsin combine with retinal to give different photoreceptor proteind a different max. sensitivity to specific wavelengths?

A

Cone cells

48
Q

dii

what specific wavelengths do photoreceptor proteins have a max sensitivity for?

A
  • Red
  • Green
  • Blue
  • UV

AH Biology (8 decks)

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