plant responses&photosynthesis

Question 1

plants need to respond to stimuli to… (5)

Answer 1

increase their chances of survival (grow towards light to absorb more for photosynthesis)

produce chemicals against herbivores

produce pheromones to produce

fold up in response to being touched

respond to abiotic stress

Question 2

what type of chemicals do plants produce to use against herbivores? (3)

Answer 2

alkaloids

tannins

terpenoids

Question 3

alkaloids

Answer 3

bitter taste, poisonous

caffeine, nicotine, cocaine, morphine

Question 4

tannins

Answer 4

bitter tasting

toxic to insects (inactivate their digestive enzymes)

Question 5

terpenoids

Answer 5

toxic to insects and fungi

Question 6

Volatile Organic Compounds

Answer 6

VOCs diffuse through the air and around the plant in a way to defend themselves

some signal pests and parasites to kill the herbivores

some are picked up by other plants who then produce VOC’s before they are attacked

Question 7

auxins (5)

Answer 7

cell elongation

preventing leaf fall

maintain apical dominance

stimulate the release of ethene

they are released from the tips of the roots and shoots

Question 8

high conc of auxins (3)

Answer 8

suppress the growth of lateral buds

maintaining apical dominance

inhibit leaf loss

Question 9

low conc of auxins

Answer 9

promote root growth

Question 10

giberellins (2)

Answer 10

stem elongation

stimulate germination of seeds by triggering the breakdown of starch to glucose (for respiration)

Question 11

ethene (2)

Answer 11

causes fruit ripening

promotes abscission

Question 12

ABA (3)

Answer 12

maintains dormancy of seeds and buds,

stimulates stomatal closing

stimulates antifreeze

Question 13

synergistic

Answer 13

plant hormones working together

auxins and giberellins work together to promote growth

Question 14

antagonistic

Answer 14

the plant hormones having an opposite effect

gibberellins stimulate the growth of lateral shoots and auxins inhibit the growth of lateral shoots

Question 15

how is ABA involved in stomatal closure? (4)

Answer 15

ABA binds to specific receptors on guard cell membranes

this causes specific ion channels to open allowing calcium ions to enter the cytosol

this increase in calcium ions causes other ion channels to open to allow other ions to leave (such as K+ ions) raising the water potential so water can leave

guard cells become flaccid

Question 16

how is ethene used to control fruit ripening?

Answer 16

ethene stimulates enzymes that break down cell walls and chlorophyll and convert starch into sugars

making fruit soft and ripe

Question 17

how are auxins used commercially? (2 ways)

Answer 17

they are used in selective weedkillers (they make weeds produce long stems and grow too fast so they cant get enough water)

they are used as rooting hormones (treated on cuttings to make them grow roots)

Question 18

equation for photosynthesis

Answer 18

co2 + h2o + energy = c6h12o6(glucose) + o2

Question 19

coenzymes used in photosynthesis

Answer 19

NADP (hydrogen acceptor)

Question 20

what is a stack of thylakoids called?

Answer 20

granum

Question 21

name 3 pigments found in chloroplasts

Answer 21

chlorophyll a

chlorophyll b

xanthophyll

Question 22

what is the purpose of the different pigments found in chloroplasts?

Answer 22

to absorb different wavelengths of light

Question 23

what occurs during PSII?

Answer 23

light hits the light harvesting cluster and is absorbed by the different pigments

the light energy is passed down the photosystem through the excited electrons

Question 24

what happens after the light reaches the reaction centre in the light dependent stage? (non cyclic)

Answer 24

photolysis to produce H+ ions, electrons and oxygen

an electron moves along the electron transport chain to PSII whilst pumping in H+ ions (creating an electrochemical gradient)

the protons diffuse down the electrochemical gradient through the ATP synthase (to create ATP) where its accepted by NADP

Question 25

what is cyclic phosphorylation?

Answer 25

where the electrons from PSI go to the top of the thylakoid membrane and revisit PSI constantly creating an electrochemical gradient producing little ATP

Question 26

where does the calvin cycle take place?

Answer 26

in the stroma

Question 27

the calvin cycle (X2 everything) (3)

Answer 27

co2 is combined with RuBP (catalysed by Rubisco) to form 2 molecules of GP

ATP becomes ADP and NADPH becomes NADP
to form TP

one carbon from TP goes to form glucose the other carbons loose a phosphate (ATP becomes ADP) and regenerate to RuBP

Question 28

where else can the carbon go to become from the TP molecule? (4)

Answer 28

carbohydrates

amino acids

glucose

lipids

Question 29

limiting factors in photosynthesis?

Answer 29

light intensity

carbon dioxide

temperature

Question 30

levels of GP and TP and RuBP at low light intensities?

Answer 30

NADPH and ATP are in short supply, therefore

rise in levels of GP and low levels of TP and RuBP

Question 31

levels of GP and TP and RuBP at low temperatures?

Answer 31

enzymes work slower

a fall in RuBP, GP and TP

Question 32

levels of GP and TP and RuBP at low co2 concentrations?

Answer 32

rise in RuBP as it is still being made but not enough to combine with co2 so a fall in GP and TP

Question 33

why do plants need a transport system

Answer 33

small SA:V so diffusion would be too slow

Question 34

xylem- structure and function

Answer 34

water and mineral ions

no end walls (uninterrupted)

dead cells with no cytoplasm

lined with lignin(stops collapsing)

bordered pits

Question 35

phloem

Answer 35

transports sugars

sieve tube elements

companion cells