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biology > organisms respond to changes in their internal and external environments > Flashcards

organisms respond to changes in their internal and external environments Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are tropisms?

A

the response of a plant to a stimulus coming from a certain direction

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2
Q

What are the two types of tropisms?

A

positive- plants growing towards stimulus
negative- plants growing away from stimulus

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3
Q

What is phototropism?

A

shoots of plants growing towards light to photosynthesise - positive phototropism
shoots of roots growing away from light - negative phototropism

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4
Q

What is gravitropism?

A

shoots of plants growing against gravity - negative phototropism
shoots of roots growing downwards with gravity - positive phototropism

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5
Q

What is hydrotropism?

A

shoots of plants growing away from water - negative phototropism
shoots of roots growing towards water - positive phototropism

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6
Q

What is thigmotropism?

A

shoots of plants growing towards objects they have touched - positive thigmotropism
explains why plants climb and attach to things

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7
Q

What are plant growth factors?

A

hormone-like substances produced by cells throughout the plant that affect the growth of tissues in the plant (an example being auxins)

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8
Q

What is IAA?

A

an example of an auxin which controls the elongation of plant cells
produced in the tips of shoots and tips of roots

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9
Q

What happens to the shoots when light intensity changes?

A

the change in light intensity causes the movement of IAA from the light sides of the shoots to the shaded side
the shoot will then bend towards the light due to a greater concentration of IAA on the shaded side which elongates the one side
this is an example of positive phototropism

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10
Q

What happens to the roots when light intensity changes?

A

IAA controls bending of the roots away fromt he light
IAA moves towards shaded side of the roots causing the elongation of cells on the shaded side and the bending of roots away from the light
this is negative phototropism

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11
Q

How do shoots and roots move towards /against gravity?

A

IAA moves to the undersides of shoots/ roots causing elongation of ells, bending them and growing upwards/downwards
roots show positive gravitropism
shoots show negative gravitropism

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12
Q

What would happen if the tip of a shoot was:
-removed
-covered with opaque material
-removed, put on agar and placed back
-agar put on half of shoot

A
  • no bending due to no IAA
  • no bending due to no IAA
  • plant will bend and grow as normal - IAA will diffuse through agar
    -plant would bend only towards that side, as IAA will only be able to diffuse on that side
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13
Q

What are the different type of receptors?

A

Photoreceptors (light)
Thermoreceptors (temp)
Chemoreceptors (chemicals)
Mechanoreceptors (pressure)
Proprioceptors (movement)

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14
Q

What is the role of sensory receptors?

A

they detect a specific stimulus and convert the change in energy into the nerve impulse/generator potentials

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15
Q

What is taxis and kinesis?

A
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16
Q

What is resting potential?

A

when there is no stimulus detected - ions move in and out of cell through ion channels and pumps

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17
Q

What is generator potential?

A

When a stimulus is detected, causing membrane of receptors to become more excited and more permeable. There is a potential difference across the membrane as more ions can enter the cell

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18
Q

What is the action potential?

A

When generator potential passes the ‘threshold level’ passing a detected stimulus onto the sensory neurone

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19
Q

What are pacinian corupscules ?

A

mechanoreceptors that detect changes in pressure

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20
Q

What is the structure of pacinian corupscules ?

A

sensory nerve ending surrounded by layers of connective tissue called lamellae

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21
Q

How to pacinian corupscules respond to change in pressure?

A

-when stimulus is detetcted, lamelle become deformed and presson the sensory nerve ending which deforms the stretch-mediated sodium ion channels
-channels open and sodium ions diffuse in
-influx of ions changes potential difference across membrane creating a generator potential
-if potetnial reaches threshold level, it will trigger action potetnial which is passed onto CNS

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22
Q

What are photoreceptors and where are they located?

A

receptors in the eye that detect changes in light
located in the fovea (in the retina)

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23
Q

How do photoreceptors in the eye respond the change in light?

A

-light enters eye through pupil and is focused onto retina
-amount of light entering eye is controlled by muscles of iris
-Photoreceptors carry electrical impulses to the brain via the optic nerve (in the place called the blind spot)

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24
Q

What are 2 types of photoreceptors?

A

rod and cone cells

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25
Q

What are the features of cone and rod cells?

A

rods- monochromatic vision, multiple rod cells connect to a singular sensory neurone, low visual ascuity, high sensitivty to light
cones - trichromatic vision (blue/green/red), each cone cell has its own sensory neurone, high visual ascuity, low sensitivty to light

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26
Q

What is spacial summation?

A

when a stimulus is detected from different areas

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27
Q

What is visual ascuity?

A

The ability to distinguish between 2 points close together

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28
Q

What are neurones?

A

Nerve cells that are responsibel for the conduction of electircal impulses (action potentials) in the body

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29
Q

What is the role of sensory neurones?

A

transmit nerve impulses from receptor to relay neurone which travels directly to motor neurone

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30
Q

What is a neurone cell body?

A

contains the cell organelles such as nucelus and large amounts of the Rough ER

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31
Q

What are dendrons ?

A

extensions of the cell body that divide into smaller branches called dendrites.

32
Q

What is an axon?

A

a single long fibre that carries electrical impulses away from the cell body

33
Q

What are dendrites?

A

dendrites can conduct electrical impulses towards cell body

34
Q

What is a myelin sheath?

A

made up of Schwann cells that are rich in lipds called myelin - protects the axon and provides electrical insulation

35
Q

What are nodes of Ranvier?

A

exposed parts of the axon between Schwann cells and where there is no myelin sheath

36
Q

What takes place when a neurone is in resting potential?

A

Sodium potassium pump pumps 3 sodium ions in and 2 potassium ions out of cell.
The potential difference is at -70mV.
The outside of the cell membrane is more positive than the inside.

37
Q

What happens during depolarisation?

A

Stimulus is detected, so voltage gated sodium ion channels open allowing sodium ions to diffuse back in, depolarising the membrane.
The inside of the membrane is now more positive so an action potential is generated, reaching at around 40mV.

38
Q

What happens during repolarisation?

A

Voltage gated sodium ion channels close and potassium ion channels open.
Cell is less permeable to sodium ions but more to potassium ions.
This causes repolarisation as outside is more positive than inside.

39
Q

What happens during the refractory period /hyperpolarisation?

A

Voltage gated potassium ion channels are slow to close so there is an overshoot in number of potassium ions that diffuse out of cell.
Outside becomes more positive than inside
Sodium potassium pump re-establishes resting potential as it pumps 3 sodium ions out and 2 potassium ions into the cell

40
Q

What is a synapse?

A

junction between 2 or more neurones or between neurones and effector cells

41
Q

What is the gap between two neurones called?

A

Synaptic cleft

42
Q

What are the 2 types of neurones (before and after a synaptic cleft?)

A

presynaptic neurone
postsynaptic neurone

43
Q

What is the end of a synaptic neurone called?

A

synaptic knob- the swollen portion of a neurone

44
Q

How can you differentiate from presynaptic and postsynaptic neurones?

A

presynaptic have vesicles that contain neurotransmitters
postsynaptic have receptor sites complementary to specific neurotransmitters

45
Q

What is the junction between 2 neurones called?

A

cholinergic synapse

46
Q

What is the junction between a presynaptic neurone and a muscle called?

A

neuromuscular junction

47
Q

What happens when an action potential reaches the end of the presynaptic neurone?

A

-voltage gated calcium ion channels open
-calcium ions diffuse across the cell surface membrane into presynaptic knob by facilitated diffusion
-influx of Ca2+ causes vesicles which contain neurotransmitters to fuse with membrane of the presynaptic knob
-neurotransmitters fuse with membrane of presynaptic knob
-neurotransmitters are released into synaptic cleft by exocytosis and bind onto complementary receptors on postsynaptic neurone
-sodium ion channels open and sodium ions diffuse down concentration gradient into postsynaptic neurone
-depolarisation of membrane
-influx of sodium ions into postsynaptic neurone causes a new action potential
-enzyme acetylcholinesterase hydrolyses ACh into acetyl and choline to stop continuous action potentials
-they will then diffuse back into knob of presynaptic neurone
-ATP produced by mitochondria is used to combine acetyl and choline to reform ACh, stored in vesicles for future use

48
Q

What is ACh an example of and why?

A

An excitatory neurotransmitter - as it depolarises the postsynaptic membrane causing action potentials to be generated

49
Q

What is AChE?

A

Acetylcholinesterase - an enzyme that hydrolyses ACh into acetyl and choline

50
Q

What is an inhibitory neurotransmitter?

A

one that prevents an electrical impulse from being passed along further

51
Q

Describe the different parts of skeletal muscle

A

-bone
-tendon
-muscle fibres
-sarcolemma
-transvers tubules
-sarcoplasmic reticulum
-myofibhril
-myofilaments

52
Q

What are the different parts of a sarcomere?

A

H zone- only myosin filaments (middle)
A band- myosin and actin
I band- only actin
M line- middle line
Z line- mark the ends of the sarcomere

53
Q

What are the 3 types of muscles?

A

Smooth, cardiac and skeletal

54
Q

What are involuntary muscles?

A

ones that contract without our concious control

55
Q

Describe smooth muscles

A

involuntary muscles
found in walls of internal organs like stomach and intestine

56
Q

Describe cardiac muscles

A

found only in the heart
myogenic muscles

57
Q

What are myogenic muscles?

A

ones that contract and relax on their own without recieving electrical impulses

58
Q

Describe skeletal muscles

A

voluntary muscles
antagonsitic muscles
made up of muscle fibres

59
Q

What are antagonistic muscles?

A

when one contracts the other relaxes

60
Q

What is the muscle that is contracting called?

A

agonist

61
Q

What is the muscle that is relaxing called?

A

antagonist

62
Q

What is the sarcolemma?

A

the cell membrane of the muscle fibre cells - it fold inwards across muscle fibres forming transverse tubules

63
Q

What is the role of transvers tubules?

A

help spread electrical impulses throughout whole of sarcoplasm

64
Q

Where are calcium ions stored and released in skeletal muscles?

A

sarcoplasmic reticulum

65
Q

What is ATP used for in skeletal muscles?

A

its provided by muscle fibres to provide energy for contractions

66
Q

Describe the structure of myofibrils

A

contain thick (myosin) and thin (actin) myofilaments
each myofibril is made up of sarcomeres

67
Q

What is the sliding filament theory?

A

when actin and myosin filaments slide over each other causing sarcomere to contract
When lots of sarcomeres contract it leads to muscle contractions

68
Q

What happens when sarcomeres contract?

A

A band stays the same
I band shortens
H zone shortens
Z lines get closer

69
Q

What is the structure of a myosin head/filament ?

A

It has a hinged globular head allowing it to move back and forth
each myosin head has a binding site for actin and ATP

70
Q

Describe the structure of actin filaments

A

contain binding sites for actin-myosin binding site
contain tropomyosin

71
Q

What is the role of tropomyosin?

A

helps filaments move past each other by blocking actin-myosin binding site when muscles are resting - leading to the inability of the filaments to slide over each other

72
Q

What happens when an action potential is generated in skeletal muscles?

A

-depolarisation of sarcolemma
-release of Ca2+ ions triggering muscle reaction
-Ca2+ binds to tropomyosin, exposing the binding site
-Myosin head binds to binding site - called the actin-myosin cross bridge
- Ca2+ ions activate enzyme ATP hydrolase which hydrolyses ATP into ADP + Pi to provide energy
- this allows myosin head to move (power stroke) pulling actin filament with it
-ATP provides energy to break cross bridge so that myosin can dettach and attach to different position

73
Q

What is the PCr system?

A

-involves ATP and phosphocreatine
-procides immmediate production of ATP by phosphorylating ADP by adding phosphate from PCr stored in cells

74
Q

What are properties of PCr?

A

-used for short bursts of vigorous excercise
- it is anaerobic byt doesnt form lactate

75
Q

What are slow twitch muscles and their properties?

A

contract slowly and work for long time before they get tired
- energy released through aerobic respiration
- lots of blood vessels to provide O2
- mitochondria near edge of muscle fibres for a short diffusion pathway
-rich in myoglobin - stores O2

biology (6 decks)

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