B6

Question 1

Photosynthesis word and symbol equation

Answer 1

Carbon dioxide(6CO2)+water(6H2O0>(chloropyll/light) glucose(C6H12O6)+oxygen(6O2)
Endothermic reaction(taken in)

Question 2

What is biomass?

Answer 2

The dry mass of an organism where energy from photosynthesis is stored-these organisms main producers for nearly all life on earth.

Question 3

Factors affecting photosynthesis

Answer 3

Light intensity-rate of ps directly proportional to light intensity until another factor becomes the limiting factor.(co2 or temp to be increased).
Temperature-rate of ps increases until the enzymes become dentaured at roughly 45 degrees c.
Carbon dioxide concentration-increased concentration=increased rate of ps until another factor becomes the limiting one so graph flattens out.(light or temp to be increased).

Question 4

Inverse square law

Answer 4

light intensity is directly proportional to 1/distance^2

Question 5

Photosynthesis core practical

Answer 5

1)Set up conical flask with pondweed and water and sodium hydrogencarbonate to make sure enough CO2 with gas syringe attached in bung.
2)Source of white light placed at specific distance.
3)Pondweed left to ps for set time.
4) As ps occurs, syringe collects oxygen and measures volume produced.
5)Repeat with light at different distances.
6)Can calculate rate of oxygen produced(volume produced/time)
7)Control any variables(temp, CO2 conc, water, sodium hydrogencarbonate)
8)Can compare results and see effects of light intensity on rate of ps.

Question 6

Root hair cells structure and adaptations in order to absorb mineral ions and vitamins

Answer 6

Large surface area-more area to absorb water and mineral ions.
Conc of mineral ions(nitrates) higher in roots hair cells than in soil- mineral ions absorbed by active transport.
Water absorbed by osmosis.
Long and thin cells- go between soil particles.
Thin walls-not restrict movement of water and absorption.

Question 7

Structure and function of phloem

Answer 7

Tubes of elongated living cells with small pores in ends to allow things through.
Transport food(sucrose) made in leaves to the rest of the plant for use (ps)or storage.
Called translocation and requires energy from respiration and goes in both directions.
-Sieve tubes and companion cells.

Question 8

Structure and function of xylem

Answer 8

Tubes made of dead cells joined end to end with no walls between them and a hole down the middle.
Strengthened with lignin(tough walls).
Carry water and mineral ions from roots to stem and leaves.
Movement of these through xylem and out of leaves is called transpiration stream.
Are impermeable to water and have no cytoplasm.

Question 9

Transpiration

Answer 9

-Loss of water from the plant.
-Caused by evaporation and diffusion of water from plant’s surface(mostly leaves).
-Loss of water creates shortage in leaf so more water drawn up through xylem.
-Means more water drawn up from roots so constant transpiration stream through plant.
Carries mineral ions.

Question 10

Structure and function of Stomata

Answer 10

Control gas exchange in the leaf. Each stoma can be opened or closed to control water loss by transpiration and allow gas exchange. Carbon dioxide diffuses in for ps oxygen and water vapour diffuse out(greatest when stomata open during day).
Mainly found on lower surface of leaf to reduce water loss by transpiration.
Tiny pores on surface of plant.
Transpiration mostly a side-effect of adaption of leaves because more water inside plant than air outside so water escapes through stomata by diffusion.
Surrounded by guard cells which change shape to control size of pore.
Turgid guard cell=stomata open and vice versa.

Question 11

Factors affecting transpiration rate

Answer 11

Light intensity- brighter light means greater transpiration rate(stomata close as gets darker because ps does not happen in dark).
Temperature- the warmer it is the faster transpiration happens(particles have more energy to evaporate and diffuse).
Air flow- the better the air flow the greater the transpiration rate(water vapour swept away from leaf so diffusion occurs more readily/high to low conc).

Question 12

Translocation

Answer 12

Sucrose converted from glucose being transported around the plant in phloem vessels. The movement of sucrose and other substances around a plant. Mainly between where a substance is made(source) and where it is stored(sinks). Eg. source in roots to sinks in leaves in early spring and source in leaves to sinks in roots in summer.

Question 13

Structure of leaf and adaptations in relation to gas exchange and photosynthesis

Answer 13

Large surface area-absorbs more light for ps.
Palisade full of chloroplasts-near top of leaf so can get most light.
Upper epidermis-transparent so light can pass through to palisade layer.
Xylem and Phloem-provide leaf with waterfor ps and take away glucose produced and support structure.
Epidermal tissues-covered in waxy cuticle which reduces water loss by evaporation.
Lots of stomata in lower epidermis=CO2 diffuse directly into leaf(guard cells control opening and closing when necessary).
Spongy mesophyll-air spaces which increase rate of diffusion of gases in and out of leaf’s cells.

Question 14

Plant adaptations for extreme environments

Answer 14

Small leaves or spines instead of leaves-reduces surface area for water loss and spines stop animals eating it.
Curled leaves or hairs-reduces air flow and then traps water near surface and reduces diffusion(as well as spines).
Thick,waxy cuticle-reduces water loss by evaporation.
Thick, fleshy stem-stores water.
Fewer stomata or only open at night-reduces evap.
stomata sunken in pits-reduces air flow close to stomata therefore reduces water loss.
Wider leaf=greater rate of transpiration.

Question 15

Auxins in shoots of plants

Answer 15

Promote growth in the shoot.(positive phototropism)
When shoot tip exposed to light accumulates more auxins on shaded side=cells on shaded side elongate(grow) faster so bends towards light.
If shoot is sideways more auxins will be produced on the lower side because of uneven gravitational distribution.
Lower side grows faster=shoot bends upwards(negative gravitropism).

Question 16

Auxins in roots of plants

Answer 16

Inhibit growth in the roots.
A root growing sideways has more auxins on lower side. Means top of cell elongate faster causing root to bend downwards(positive gravitropism).
If root exposed to light, auxins accumulate on more shaded side so inhibits growth meaning root bends downwards away from light/into ground(negative phototropism).,

Question 17

Auxins uses

Answer 17

Weedkillers-selective weedkiller, developed from auxins, only affect broad leafed weeds not narrow-leafed crops.
Disrupt growth patterns/grow uncontrollably meaning they die and crops untouched.
Rooting powders-contains auxins which produces roots rapidly and will start growing new plants. Growers can then produce lots of clones really quickly.

Question 18

Gibberilins uses

Answer 18

Germination-used to make plants flower earlier than usual or under different conditions.
Reduce flower formation-improves fruit quality(some plants produce too many flowers meaning that too many fruits form and cannot all be supported then grow small. Fewer flowers= fewer fruits (big fruits and good quality).
Seeds can germinate at any time of year.
To produce seedless fruit-fruit(with seeds in middle) normally only grows on plants pollinated by insects. If gibberlilins applied to unpollinated flowers of some plants, the fruit will grow but the seeds wont.

Question 19

Ethene uses

Answer 19

Controlling the ripening of fruits-can be picked when unripe(firmer and less easily damaged).
Ethene can be added and the fruit will ripen on way to shop and be perfect as reaches shelves.