Animal + Plant Transport

What is abiotic stress?Give an example

Non-living environmental factor that could harm a plant, e.g mineral deficiency,drought,depleted oxygen supply,pollution

How do plants respond to abiotic stress and herbivory? [4]

• Produce anti-freeze enzymes

• May contain bitter-tasting tannins

• May contain bitter-tasting nitrogen compounds called alkaloids

• Release cell-signalling pheromones to trigger defensive responses in other organisms

How does Mimosa pudica respond to being touched?

The leaves fold due to seismonasty

What is a plant tropism?

Directional growth response of plants

What is phototropism?

Response to light

What is geotropism?

Response to gravity

What is hydrotropism?

Response to water

What is thermotropism

Response to temperature

What is thigmotropism?

Response to touching a surface or object

How is leaf loss in deciduous plants controlled? [3]

1. As leaf ages, cytokinin and auxin levels lower,ethene level increases

2. Triggers production of cellulase enzymes which weaken leaves by breaking down cell walls in abscission layers

3. Leaves break from branch, and Suberin layer forms to prevent entry of pathogens

List the functions of gibberellins [4]

• Stimulates germination

• Elongation at cell internodes

• Fruit growth

• Rapid growth/flowering

How is germination stimulated? [4]

1. Seed absorbs water, activating embryo to secrete gibberellins

2. Gibberellins diffuse to aleurone layer,which produces amylase

3. Amylase diffuses to endosperm layer to hydrolyse starch.

4. Hexose sugars act as respiratory substrate to produce ATP as ‘energy currency’

List the functions of auxins [4]

• Involved in trophies responses

• Control cell elongation

• Suppress lateral buds to maintain apical dominance

• Promote root growth e.g in rooting powder

Outline the positive phototropic response shown by shoots [5]

1. IAA diffuses to shaded side of shoot tip

2. This causes active transport of H⁺ Into cell wall

3. Disruption to H-bonds between cellulose molecules plus the action of expansins makes the cell more permeable to water

4. Cells on shaded side elongate faster due to higher turgor pressure

5. Shoot bends towards light

Outline the gravitropic response of roots [3]

1. Gravity causes IAA to accumulate on lower side of the root

2. IAA inhibits elongation of root cells

3. Cells on the upper side of the root elongate faster, so the root tip bends downwards

How do hormones stimulate stomata to close? [4]

1. Abscisic acid binds to complementary receptors on guard cell membrane, causing Ca²⁺ Ion channels on tonoplast to open. Ca²⁺ Ions diffuse from vacuole into cytosol

2. Positive feedback triggers other ion channels to open, causing them to diffuse out of the guard cell

3. Water potential of guard cell becomes more positive. Water diffuses out via osmosis.

4. Guard cells become flaccid so stomata close

What hormones maintain apical dominance?

Maintained by the action of auxin, abscisic acid and cytokinins

Explain the experimental evidence that auxins maintain apical dominance

When the site of auxin production, the apex, was removed, these two things happened:

• Auxin levels drop,causing abscisic acid levels to drop

• Cytokinins diffuse evenly to promote bud growth in other parts of plant, causing lateral buds

Explain the experimental evidence that gibberellins control stem elongation and germination. [2]

Stem elongation-Tall plants have higher gibberellins concentration than dwarf plants

Germination-Mutant seeds with non-functional gibberellins gene do not germinate unless gibberellin is applied externally

How are auxins used commercially? [3]

• Rooting powder

• Growth of seedless fruit

• Herbicides

How are cytokinins used commercially? [2]

• Prevents yellowing of lettuces leaves

• Promotes shoot growth

How are gibberellins used commercially?

• Delate senescence in citrus

• Elongation of stalks

• Speeding up seed formation

How is ethene used commercially?

• Speeds up ripening

• Promotes lateral growth

• Promotes fruit drop

Outline the gross structure of the mammalian nervous system using a flow diagram

Name the two main divisions of the nervous system

Central nervous system and nervous system

Name the two main divisions of the peripheral nervous system

• Somatic

• Autonomic

Name the two main divisions of the autonomic nervous system

Sympathetic and Parasympathetic

Describe the gross structure of the human brain, including the lobes and their function [4]

• 2 Hemispheres joined by band of nerve fibres divided into lobes

  • Parietal lobe-top of the brain-movement,orientation,memory and recognition

  • Occipital lobe-back of the brain-visual cortex processes signals from the eye

  • Temporal lobe-beneath the temples-processes auditory signals

What is the function of the cerebllum?

Controls execution of movement, and potential role in cognition

Identify the function of the medulla oblongata

Controls a rage of autonomous functions, including breathing rate and heart rate

Identify the function of the cerebrum

Controls voluntary functions

Identify the functions of the hypothalamus

Includes anterior pituitary gland and is involved in thermo and osmoregulation

Outline what happens in a simple reflex arc

Receptor detects stimulus → sensory neuron → relay neuron in CNS coordinates response → response by effector

What is the survival benefit of a reflex arc?

Rapid response to potentially dangerous stimuli since only 3 neurons are involved

Describe the knee jerk reflex

1. Tapping patellar tendon stimulates stretch mediated receptors

2. Impulse travels sensory → motor neuron

3. Quadriceps contract,inhibiting antagonistic hamstring contraction

Describe the blinking reflex and the reflex arc

• Consensual response since both eyelids close when just 1 cornea is stimulated

• Sensor neuron of trigeminal nerve → spinal nucleus of trigeminal nerve → interneurons→ facial motor nerve → effector muscled orbicularis oculi

What is the fight or flight response?

A stress response to a perceived threat triggering a series of physiological response to prepare the body

Use the secondary messenger model to explain how adrenaline works [5]

1. Adrenaline is the 1st messenger, forming a hormone-receptor complex

2. Conformational change to receptor activates G-protein

3. Activates adenylatye cyclase, which converts ATP → cAMP

4. cAMP works as 2nd messenger activating the protein kinase A pathway

5. Results in glycogenolysis

What are the three types of muscle tissue

Skeletal, smooth and cardiac

Describe skeletal muscle function

• Antagonistic muscle pairs enable movements

Describe the function of smooth muscle

Enables contraction of walls of blood vessels and intestines

Describe the structure and function of cardiac muscle

• Consists of branched uninucleated cells

• Myogenic contractions cause a heartbeat

Describe the gross structure of skeletal muscle

• Muscle cells are fused together to form bundles of parallel muscle fibres called myofibrils

• Each bundle is surrounded by endomycium:loose connective tissue with many capillaries

Describe the microscopic structure of skeletal muscle

• Myofibrils: site of contraction

• Sarcoplasm: shared nuclei and cytoplasm with lots of mitochondria and ER

• Sarcolemma: folds inwards towards sarcoplasm to form transverse T tubules

Label this diagram with the zones and bands of a myofibril

What is the Z line?

Boundary between sarcomeres

What is the I band

• The ‘light’ band containing only actin

What is the A band

The ‘dark’ band which overlaps actin and myosin

What is the H-zone

A zone that only contains myosin

How is muscle contraction stimulated? [5]

1. Action potential arrives at neuromuscular junction, opening voltage-gated Ca²⁺ channels open

2. Vesicles move towards & fuse with presynaptic membrane

3. Exocytosis of acetylcholine, which diffuses across the synaptic cleft

4. Ach binds to receptors on Na⁺ channel proteins on skeletal muscle cell membrane

5. Influx of Na⁺ Causes depolarisation

Explain the role of Ca²⁺ in muscle contraction [3]

1. AP moves through T-tubules in sarcoplasm, opening Ca²⁺ Channels in sarcoplasm in reticulum

2. Ca²⁺ binds to troponin, triggering conformational change in tropomyosin

3. Exposes binding sites on actin filaments so action myosin bridges can form

Outline the ‘sliding filament theory’ [5]

1. Myosin head with ADP attached forms cross bridge with actin

2. Power stroke: myosin head changes shape & loses ADP, pulling actin over myosin

3. ATP attaches to myosin head, causing it to detach from actin

4. ATPase hydrolyses ATP→ADP + Pi, returning mysoin head to original position

5. Myosin head re-attaches further along filament

How does sliding filament action cause a myofibril to shorten? [3]

• Mysoin heads flex in opposite directions = actin filaments are pulled towards each other

• Distance between adjacent sarcomere Z lines shortens

• Sliding filament action occurs up to 100 times per second in multiple sarcomeres

Explain the role of creating phosphate in muscle contraction

Phosphorylase’s ADP directly to ATP when oxygen for aerobic respiration is limited

State the name and location of the 2 nodes involved in heart contraction

Sinoatrial node (SAN) : within the wall of the right atrium

Atrioventricular node (AVN): near the lower end of the right atrium in the wall that separates the 2 atria

Name the receptors involved in changing HR and state their location?

Baroreceptors: carotid body

Chemoreceptors: carotid body and aortic body

How does the body respond to an increase in BP? [3]

1. Baroreceptors send more impulses to the cardioinhibitory centre in the medulla oblongata

2. More impulses to SAN down vagus nerve via parasympathetic nervous system

3. Stimulates release of Ach, which decreases HR

How does the body respond to a decrease in blood pressure? [3]

1. Baroreceptors send more impulses to cardioacceleratory centre in the medulla oblongata

2. More impulses to SAN via sympathetic nervous system Stimulates release

3. Stimulates release of noradrenaline, which increases heart rate and strength of contraction

How does the body respond to an increase in CO₂ Concentration? [3]

1. Chemoreceptors detect pH decrease and send more impulses to cardioacceleratory centre of medulla oblongata

2. More impulses to SAN via sympathetic nervous system

3. HR increases, so rate of blood flow to lungs increase, increasing rate of gas exchange and ventilation

Describe the structure of a neuromuscular junction and its function

• Synaptic cleft between a presynaptic motor neuron and a skeletal muscle cell

• Acts as the end of neural pathway and always stimulates an excitatory response