Biology module 5 - Animal and Plant responses

Question	Answer
Structure of MYOFIBRIL in particular sarcomeres. Image: Sarcomere (binary/octet-stream)	A sarcomere is a small unit of a myofibril. Thick myofilament = MYOSIN (dark A bands) Thin myofilament = ACTIN (light I bands)
Muscle contraction by the Sliding Filament Theory	Myosin and actin filament slide over each other to cause the sarcomere to contract Simultanous contaction of sarcomeres means myofibrils and muscle fibres contract. I band gets shorter A bands stay the same length H zone gets shorter
Myosin structure and how this helps it to move?	Myosin filament has a globular head that are hinged allowing it to move back and forth. Each head has a binding site for actin and a binding site for ATP.
What is found between Actin filaments?	Tropomyosin and troponin are proteins found between actin filaments. They help myofilament move past each other
In a resting unstimulated muscle....	The actin myosin binding site is blocked by tropomyosin which is held in place by troponin So myofilamnets cant move past each other because cross bridges cant be formed from actin binding site and myosin head.
The power stroke	1. Myosin head attaches to surrounding Actin filament forming a cross-bridge 2. The head bends causing the actin thin filament to be pulled along and overlap with more of the myosin thick filament ADP and Pi are released
What is muscle contraction triggered by?	When action potential from motor neurone stimulates a muscle cell it depolarizes the Sarcolemma. This depolarisation spreads down the t- tubules to Sarcoplasmic reticulum. This cause SR to release stored calcium ions into sarcoplasm. An influx of Ca2+ ions bind to troponin causing a change in its shape - this pulls out the tropomyosin from the actin-myosin binding site allowing myosin head to bind instead = forms an actin-myosin cross bridge
what provides the energy for the myosin head to move	Calcium ions also activate ATPase which breaks down ATP into ADP + pi to provide energy for muscle contraction. This energy released moves the myosin head which pulls the actin filament along
how the cross bridge breaks?	ATP provides energy to break the actin-myosin cross bridge so that the myosin head detaches from the actin filament after it has moved. It continues to form these cross bridges down the length of the actin filament. Many cross bridges are made and broken very rapidly - shortening the sarcomere & causing muscle to contact
When the muscles are relaxed...	When the muscle stops being stimulated calcium ions leave the binding sites on the troponin molecules and are moved by active transport back into the SR (+ATP) Tropinin molecules return to the original shape pulling the attached tropomyson molecules with them. This means that the tropomyosin molecules block the cross bridge binding site = muscle is relaxed as the binding site has no myosin head attached. Actin filament slides back to relaxed position lengthening the sarcomere.
Sources of ATP	1. Aerobic respiration- mostly from oxidative phosphorylation in mitochondria (only with sufficient oxygen) 2. Anaerobic respiration- ATP produced rapidly via glycolysis end product= pyruvate which is converted into lactate by lactate fermentation this can build up in muscles causing muscle fatigue - good for short period of hard exercise 3. ATP- Creatine Phosphate - ATP is made by phosphorylation of ADP adding a pi from creatine phosphate (CP) found in sarcoplasm. This generates ATP very quickly 2-4 sec worth of contractions. this is also anaerobic but doesn't form lactate. Uses enzyme creatine phosphotransferase
what is a neuromuscular junction and what does it do?	Neuromuscular junction is a synapse between a motor neurone and a muscle cell uses the neurotransmitter ACETYLCHOLINE (ACh) which binds to receptors These junctions work the same as synapses between neurones- releasing neurotransmitter causes depolarization in post synaptic cell. Depolarisation causes the muscle cell to contract.
Three types of muscle?	1. Involuntary smooth muscle 2. Voluntary skeletal muscle 3. Cardiac muscle
Skeletal muscle	Contraction is conscious Made up of many muscle fibres that have many nuclei Cross striation throughout (striped pattern) Found in joints
Smooth muscle	Unconsciously controlled No striped appearance each muscle fibre has 1 nucleus - they are spindle-shaped with pointed ends found lining gut and internal gut - used in peristalsis contact slowly and don't fatigue.
Cardiac muscle	Contracts on its own - MYOGENIC found in walls of the heart muscle fibres are connected by intercalated discs which have low electrical resistance so nerve impulses pass easily between cells muscle cells are branched to all quick spread of impulses 1 nucleus in each cell Contact rhythmically and don't fatigue.
Types of plant responses? & What is a tropism?	Tropism is a response of a plant to a directonal stimulus. Can be positive and negative. 1. Phototropism- plant growth in respose to light 2. Geotropism- plant growth in reponse to gravity 3. Hydrotropism- plant growth in response to water 4. Thigmotropism - plant growth/ winding around a structure in response to a touch stimulus 5. Chemotropism - plant growth in response to chemical stimulus
Chemical defences of plants to herbivore examples	1. ALKALIODS - chemicals with a bitter taste that deter herbivores eating them 2. TANNIS - bitter-tasting plants which binds to proteins in the gut, making digestion of the plant hard also detering herbivoes from eating them. 3. pheremones
Pheromones released?	Alarm pheremones which repond to herbivores grazing - this causes nearby plant to detect chemicals and begin to produce chemical defences
Touch responses / Nastic response it is non-directional	MIMOSA PUDICA when it is touched the signal is spread through the entire plant causing it to fold up quickly. Thigmonastic = from any direction of a touch response (not like thigmotropism) This protects the plant against herbivores by knocking off insects feeding on the plant and scaring of animals which may be trying to eat it.
Abiotic stress causing a response in the plant	Some plants respond to the cold by producing its own antifreeze. e.g. carrots produce antifreeze proteins at low temperatures - proteins bind to ice crystals at lower temps that water freezes at, stopping more ice crystals from growing.
main 2 plant hormones?	Gibberellins -stimulate seed germination -stem elongation -flowering Auxins -stimulates the growth of shoots by cell elongation, this is where cell wall becomes stretchy and so can get longer -inhibits the growth of side shoots/ lateral buds
all the plant hormones	1. Cytokinins -promote cell division -delay leaf sentencing/ ageing -overcomes Apical Dominance -promote cell expansion 2. Abscisic acid -inhibit seed germination, growth and stomatal closure in times of stress 3. Auxins 4. Gibberellins
Where are auxins produced?	Auxins are produced in the apex/ tips of shoots
Example of an Auxin and what it does? also how does this auxin move around the plant	Indoleacetic Acid (IAA) stimulates cell elongation IAA moves basipetally (from apex to base) IAA is moved around the plant to control the tropisms. It moves by diffusion and active transport over a short distance and via the phloem, if it's a long distance
Effect of auxins on phototropism and geotropism	IAA moves to the shaded parts of the shoots to the zone of elongation so the cells elongate here causing the shoot to bend towards the light (positive phototropism) As well as causing the roots to grow downwards as they distrobute on the underside of the roots therefore roots grow downwards (positive geotropism)
Investigating geotropism equipment?	Using a CLINOSTAT Image: Image 04 (image/jpeg)
Why is it important for plants to respond to stimuli?	1. Grow towards light to maximise light absorbtion for photosynthesis 2. Grow down into the soil for extraction of water and mineral ions 3. Climbing plants have a sense of touch cauising them to wrap around objects and grow toward light.
What are auxins involved in?	Apical Dominance
What is Apical Dominance	The shoot tip of a flowing bud is known as an apical bud. Auxins stimulate the growth of this bud and inhibit the growth of side shoots from lateral buds. This is apical dominace - apical bud is dominat over the lateral buds. This prevents the side shoots from growing saving energy - allowing the plant to grow quickly.
Where are Gibberellins produced and what do they do?	Gibberellins produced in young leaves and in seeds Stimulate stems of plants to grow by stem elongation- helping plants grow very tall. Gibberellins stimulate seed germination by triggerig the breakdown of starch into glucose in the seed
auxins and gibberellins...	Auxins and gibberellins are often synergistic - this means they work together to have a big effect. They are also antagonistic - they oppose each others actions
A plants losing leaves in winter is a...	Deciduous plant which conserves water by losing leaves as in winter it is difficult for the plant to gain water as water under the ground might be frozen.
Enter text here... Image: Brain (binary/octet-stream)	Brain
Hormones involved in stomatal closure	Plants need to be able to close stomata in order to reduce water loss through transpiration Guard cells are found on either side of stomata pores. When the guard cell is full of water the pore is open. When the guard cell is flaccid the pore is closed. Hormone ABSCISIC ACID (ABA) triggers stomatal closure. ABA binds to receptors on the guard cell membranes this causes ion channels to open allowing calcium ions to enter the cytosol from the vacuole. This increased concentration of calcium ions causes other ion channels to open. Allowing ions like potassium to leave the guard cells, raising the water potential of the cell. Water then leaves the guard cell via osmosis causing them to go flaccid and stomata closes.
Commercial uses of plant hormones	1. Ethene stimulates enzymes that break down cell walls, break down chlorohyll and convert starch into sugars. This makes FRUIT ripe and ready to eat 2. Auxins are used as SELECTIVE WEEDKILLERS (herbicides)- which make weeds produce long stems instead of leaves, this makes the weeds grow too fast so they cant get enough water or nutrients so they die. 3. Auxins used as ROOTING POWDERS - auxins make a cutting of a plant grow roots. The cutting can be planted and grown. So many plants can be grown quickly and cheaply fom 1 plant.

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Biology module 5 - Animal and Plant responses

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	Created by Anna Zavolnyi over 6 years ago