Plant and animal responses Flashcards

Question

What is actin?

Answer 1

Makes up thin filaments. 2 strands of actin subunits twisted together.

Answer 2

Attached to tropomyosin = globular molecules of troponin - 3 polypeptides; 1 bound to actin, 1 to tropomyosin, 1 to Ca2+ when available. At rest, block binding sites on thin filament where thick binds during contraction.

Answer 3

I band becomes narrower, Z lines move closer, H zones become narrower. Sarcomeres contract due to myosin head movement - interact with actin -> cross bridges.

Answer 4

1. AP arrives at NMJ - travels into muscle fibre via T-tubules, in contact with sarcoplasmic reticulum of fibre 2. AP reaches SR, triggers SR stores to release Ca2+ into sarcoplasm 3. Ca2+ binds to troponin associated with actin filaments. Ca2+ binding -> troponin changes shape and pulls away tropomyosin - expose binding site on actin filament 4. Myosin can attach to actin + form cross bridge. Myosin head attached to ADP + Pi 5. Myosin heads change angle and pull actin filaments past myosin, shortening sarcomere = power stroke (ADP + Pi released) 6. New ATP attaches to myosin head, breaking cross bridge. Heads return to OG positions and detach from actin. ATP hydrolyses + ADP+Pi bind. 7. Myosin heads attach to another binding site further down.

Answer 5

After contraction, Ca2+ pumped back into SR so actin filament blocked by tropomyosin - contraction stops.

Answer 6

Myosin head contains ATPase. Energy needed to move myosin heads, reabsorption of Ca2+ by active transport. - many mitochondria in muscles - anaerobic respiration occurs in muscle cell sarcoplasm - creatine phosphate stores phosphate groups + donates to ADP.

Answer 7

In right atrium is the SAN - starts wave of electrical stimulation. - wave to atrial walls and contract simultaneously. Depolarisation SAN to AVN - signal to atrial septum - thin collagen layer stops reaching ventricles so to AVN - AVN signal to ventricles then to bundle of His with slight delay - bundle of His to Purkinje fibres + branch into each ventricles (contract from base up)

Answer 8

Accelerator nerve - SNS, high frequency of impulses to SAN to increase heart rate Vagus nerve - PNS, lowers heart rate by low frequency of impulses

Answer 9

Due to internal stimuli - chemoreceptors and baroreceptors. If high blood pressure, baroreceptors to medulla to parasympathetic neurones. Ach released in cardiac muscle - bind to receptors on SAN. Noradrenaline and sympathetic neurones if low blood pressure. Which one is active depends on how many depolarisations these nerves make.

Answer 10

Differences: animal from endocrine, transported in blood, fast acting, act on target cells only. Plant from cells, in phloem/xylem, slow acting, act on most cells. Similarities: chemical messengers made in cells, can be moved from production site, ST or LT, affect gene expression.

Answer 11

Tannins - toxic to microorganisms and herbivores. In upper epidermis. Alkaloids - derived from aa and taste bitter. Pheromones - affect behaviour/physiology of other organisms.

Answer 12

Directional growth response - direction determined by direction of external stimulus. Phototropism, geotropism, chemotropism, thigmotropism.

Answer 13

Non directional response to external stimuli. Eg. Mimosa pudica plant responds to touch and leaves fold up.

Answer 14

Apical - tips of roots and shoots Lateral bud - forms side shoots Lateral - widening of roots and shoots Intercalary - between nodes, shoot getting longer

Answer 15

Control plant photo and geotropic responses by regulating cell elongation. Auxin leads to an increase in the plasticity of cell walls, so stretch easier when cell elongates. Moved by diffusion to cell to zone of elongation. Causes H+ AT into spaces in cell wall, activate proteins = expansins and loosen cellulose, decrease rigidity. Break bonds in cellulose, so walls expand as cell takes in water via osmosis.

Answer 16

Cells in shoot tip produce auxin and transported evenly down shoot. Light causes auxin to move from light to shaded side. Leads to elongation of shoot cells - bends to light. In roots, has opposite effect - high auxin concentration inhibits cell elongation so faster on light side and bends away

Answer 17

Auxin produces in root tip and evenly distributed. Gravity causes auxin to move from upper to lower side. Auxin inhibits root cell elongation so it bends down to gravity.

Answer 18

Cause redistribution of auxin in response to light. Phototropin 1 and 2. - activity enhanced by blue light, increasing activity on light side - gradient leads to auxin redistribution via effects on PIN proteins (found in all sides of plant membranes) - control outflow of auxin from cells - PIN proteins controlled by PINOID but only works with short bursts of light

Answer 19

Shoot tip is responsible for phototropic responses - water and solutes need to move backwards form tip for phototropism to occur When gelatine block placed on shoot tip, positive phototropism seen. But when mica block used, no response. So messenger = diffusable. When tip placed on agar block and block on top of cut plant, shoot grew as messenger diffused into agar then to plant. Plain agar block showed no growth.

Answer 20

Cytokinins - delay leaf senescence + help maintain nutrient supply in leaves. Cell division and expansion increased. Auxins - promote cell elongation and inhibition of side shoot growth. Inhibit leaf abscission, present in leaves. Abscisic acid - low water availability - stomata closes and decreases loss via transpiration. Inhibits seed germination and growth. Gibberellins - promote seed germination and stem growth. Ethene - fruit ripening.

Answer 21

If shoot tip removed, side branches start growing. To determine exact effect: ends of shoot cut and auxin layer applied. No lateral bud growth. Normal auxin levels inhibit growth., low levels promote.

Answer 22

Abscisic acid - high when high auxin, so growth inhibited. So tip cut, acid decreases so buds can grow. Cytokinins - apply directly to buds can override apical dominance. High auxin makes shoot tip a cytokinin sink. Auxin gone, cytokinin spreads evenly.

Answer 23

Control stem elongation and seed germination. Breaks starch to glucose which plant embryo uses for respiration. GA levels in tall pea plants and dwarf were compared. Tall plants had higher levels. Leaf loss in winter - some plants lose leaves. Older leaf, more ethene it makes. So leaf falls. Ethene - layer of cells at leaf base = abscission layer to expand - breaks cell wallls. Stomatal closure - Abscisic acid binds to guard cells and opens Ca2+ channels. Some enters guard and opens K+ channels. Lots K+ leaves so less negative water potential. Water leaves by osmosis.

Answer 24

Prevent leaf and fruit abscission - treat unpollinated flowers to form seedless fruits - weedkillers - excessive apical dominance so grows too fast and dies - root powder - roots grow fast (fast and cheap)

Answer 25

Prevent yellowing of plant leaves after being picked - mass production because increases bud and shoot growth - side branches split and grow separately

Answer 26

Fruit production - elongates stems so more space to grow bigger. Increases sugar production in sugar canes.

Answer 27

Controls ripening and rotting. - increase fruit drop and speed up ripening - prevent ethene synthesis (low temp stores) with low O2 and high CO2 - increases shelf life