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A Level Biology OCR A > 5.1.5 > Flashcards

5.1.5 Flashcards

(61 cards)

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1
Q

What are the physical defences plants have evolved to prevent herbivory?

A

Barbs, spikes, spiny leaves, and inedible tissue.

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2
Q

What are tannins?

A

A group of phenols produced by plants that are toxic to microorganisms and larger herbivores.

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3
Q

Where are tannins found in plants?

A

In the upper epidermis of leaves and in the roots.

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4
Q

What are alkaloids?

A

Bitter-tasting, nitrogenous compounds found in growing tips and flowers, acting as a feeding deterrent.

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5
Q

What are terpenoids?

A

A group of compounds that are toxic to insects and fungi.

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6
Q

What are pheromones in plants?

A

Chemicals released by one plant that can affect the physiology of another.

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7
Q

What response can trigger the release of pheromones in plants?

A

Water stress or herbivory.

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8
Q

What is phototropism?

A

A directional growth response of plants to light.

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9
Q

How do leaves and roots respond to phototropism?

A

Leaves are positively phototropic; roots are negatively phototropic.

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10
Q

What is geotropism?

A

The growth of roots toward gravity.

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11
Q

What is chemotropism?

A

The growth of pollen tubes down the style, attracted by chemicals.

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12
Q

What is thigmotropism?

A

Growth in response to touch.

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13
Q

What is nastic response?

A

Non-directional responses to external stimuli.

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14
Q

What is thigomonasty?

A

The folding of leaves in response to touch.

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15
Q

How can phototropism be tested?

A

By germinating seeds under unilateral light and comparing growth.

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16
Q

What device can be used to measure geotropism?

A

A clinostat.

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17
Q

What initiates abscission in plants?

A

Falling light levels and auxin concentrations.

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18
Q

What is the role of ethene in abscission?

A

It initiates gene switching to produce enzymes that digest cell walls.

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19
Q

What causes stomatal closure?

A

Low light concentrations or water stress.

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20
Q

What hormone controls stomatal closure?

A

ABA (abscisic acid).

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21
Q

What is the role of gibberellins in seed germination?

A

They promote seed germination by enabling the production of amylases and proteases.

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22
Q

What is the antagonistic hormone to gibberellins?

A

ABA (abscisic acid).

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23
Q

What is the effect of gibberellins on dwarf plants?

A

They cause dwarf plants to grow taller.

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24
Q

How can ripening of fruit be controlled?

A

By using gibberellins to delay ripening and exposing to ethene gas to promote ripening.

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25
What is the role of rooting powders in plant propagation?
They increase the success of micropropagation by containing auxins.
26
How do hormonal weedkillers work?
They use synthetic dicot auxins that are absorbed by broad-leaved plants, causing unsustainable growth.
27
What makes up the central nervous system (CNS)?
The brain and spinal cord.
28
What is the role of the peripheral nervous system?
To ensure rapid communication between sensory receptors, the CNS, and effectors.
29
What are the two subdivisions of the peripheral nervous system?
The somatic nervous system and the autonomic nervous system.
30
What does the somatic nervous system control?
Action potentials under voluntary control, such as skeletal muscles.
31
What does the autonomic nervous system control?
Action potentials not under voluntary control, including glands and cardiac and smooth muscle.
32
What are the two branches of the autonomic nervous system?
The sympathetic nervous system and the parasympathetic nervous system.
33
What is the role of the cerebrum?
It organizes most of the higher thought processes, such as conscious thought and memory.
34
What is the function of the cerebellum?
It coordinates movement and balance.
35
What does the hypothalamus control?
Homeostatic responses and various physiological processes.
36
What is the medulla oblongata responsible for?
Coordinating many autonomic responses.
37
What is the primary role of reflex actions?
To provide rapid responses to environmental changes without involving the brain.
38
What is the blinking reflex?
A response that closes the eyelid in reaction to stimuli such as bright light or foreign objects.
39
What is the knee jerk reflex?
A spinal reflex that causes the leg to kick in response to stretching the patella tendon.
40
What initiates the 'fight or flight' response?
Recognition of a threat by the cerebrum, which stimulates the hypothalamus.
41
What hormone is released by the adrenal medulla during 'fight or flight'?
Adrenaline.
42
What is the role of adrenaline in cell signaling?
It binds to receptors on target cells and activates a secondary messenger, cAMP.
43
What are the three types of muscle tissue?
* Involuntary (smooth) muscle * Cardiac muscle * Skeletal (voluntary, striated) muscle.
44
What characterizes smooth muscle?
Non-striated, spindle-shaped, and controlled by the autonomic nervous system.
45
What is unique about cardiac muscle?
Striated muscle that contracts simultaneously across heart chambers.
46
What type of muscle is non-striated and controlled by the autonomic nervous system?
Smooth muscle ## Footnote Smooth muscle contracts slowly and regularly in different directions and does not tire quickly.
47
What is the primary function of cardiac muscle?
To produce simultaneous contractions of the heart chambers ## Footnote Cardiac muscle is specialized striated muscle that spreads electrical stimulation evenly over the heart walls.
48
What distinguishes skeletal muscle from other muscle types?
It is voluntary and controlled by the somatic nervous system ## Footnote Skeletal muscle is found at the joints in the skeleton and has rapid, short contractions.
49
What are the two types of filaments found in myofibrils?
Actin and myosin ## Footnote These filaments are responsible for muscle contraction.
50
What is the functional unit of muscle called?
Sarcomere ## Footnote The sarcomere is the structure between Z-lines and is surrounded by the sarcoplasmic reticulum.
51
What happens at the neuromuscular junction?
Action potentials propagate from the somatic nervous system to the motor unit ## Footnote This is similar to a synapse where acetylcholine is released.
52
Fill in the blank: The sliding filament hypothesis explains how the _______ and the H-zone get shorter during contraction.
light band ## Footnote This results in the Z lines moving closer together, shortening the sarcomere.
53
What role do calcium ions play during muscle contraction?
They bind to troponin, causing a conformational change that allows myosin heads to bind to actin ## Footnote This initiates the power stroke in muscle contraction.
54
What is the power stroke in muscle contraction?
The tilting of myosin heads that pulls actin filaments past the myosin filaments ## Footnote ATP hydrolysis occurs during this process, releasing ADP and Pi.
55
How is ATP regenerated during muscle contraction?
Through aerobic respiration and anaerobic respiration ## Footnote Aerobic respiration occurs in mitochondria, while anaerobic respiration occurs in the sarcoplasm.
56
What is the consequence of anaerobic respiration in muscle tissue?
Production of toxic lactate ## Footnote This occurs when oxygen supply is insufficient for aerobic respiration.
57
What is the function of creatine phosphate in muscle contraction?
It acts as a reserve of phosphate groups to rapidly phosphorylate ADP ## Footnote This occurs through substrate-level phosphorylation during contraction.
58
True or False: Skeletal muscle fibers are multinucleate.
True ## Footnote This characteristic is important for the function and regeneration of skeletal muscle.
59
What are transverse tubules?
Folds of the sarcoplasmic reticulum that spread electrical impulses throughout the muscle fiber ## Footnote They play a crucial role in muscle contraction.
60
What is the role of acetylcholine at the neuromuscular junction?
It binds to specific receptors in the sarcolemma, causing depolarization ## Footnote This initiates a wave of depolarization that leads to muscle contraction.
61
What does the term 'Bohr shift' refer to in muscle physiology?
The phenomenon where oxygen quickly dissociates from hemoglobin in response to increased carbon dioxide ## Footnote This enhances oxygen delivery during muscle activity.

A Level Biology OCR A (4 decks)

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