Photosynthesis TOPIC 4 Flashcards
What are the specialised features of a leaf
- waxy cuticle
- transparent upper epidermis
- packed palisade mesophyll
- lots of chloroplasts
- airy spongy mesophyll
- xylem
- phloem
- lower epidermis
- air spaces
- stomata
- gurad cells
What is photosynthesis
a series of endothermic chemical reactions which occur in plant cells which contain chloroplasts to generate energy
When is repiration carried out
all the time - day and night
What is the word equation for photosynthesis
carbon dioxide + water -> glucose + oxygen
what is the chemical equation for photosynthesis
6 CO2 + 6 H2O -> C6H12O6 + 6 O2
What are the factors which are required for photosynthesis to occur
- light
- warmth
- chlorophyll
what is the waste product of photosynthesis
oxygen
How do plants get carbon dioxide
CO2 diffuses down the concertration gradient from the air in the environment through the stomata into the air spaces in the leaf
How do plants get water
Water moves by osmosis down the water potential gradient from the sapces between soil particles into the root hair cell
Describe the method to test leaves for startch
- set up water bath using a beaker, tripod, gauze and bunsen burner
- use forceps to put leaf in boiling water
- turn off bunsen
- fill boiling tube 1/3rd with ethanol
- place in beaker for 10min
- remove leaf from ethanol with forceps
- dip leaf in hot water
- smooth out leaf onto white tile
- add iodine solution
- observe colour change
Why do we use ethanol when testing leaves for startch
the ethanol removes the chlorophyll from the leaf so it changes colour with the iodine easier
why do we boil the leaf when testing it for startch
to remove the waxy cuticle
What are the limiting factors
- light intensity
- carbon dioxide concertration
- temperature
- chlorophyll levels in leaf
How is light intensity a limiting factor
plenty of light = lots of phtotsynthesis
it is a limiting factor until it plateaus
How is CO2 concertration a limiting factor
more CO2 = more photosynthesis
- CO2 levels rise at night and get used up in the morning
it is a limiting factor until it plateaus
Why is the more CO2 at night
because the plants respire but don’t photosynthesise
How much of the atmosphere is CO2
0.04%
How can CO2 levels be overcome
Science labs or greenhouses can aartificially increase the levels of CO2
How is temperature a limiting factor
hgiher temperature = faster/more photosynthesis
temperture increase generates more kinetic energy
What can happen to the plant if temperature gets too high
- enzymes denature around 40-50 celcius
- photosynthesis is controlled by enzymes
How is chlorophyll a limiting factor
Chlorophyll absorbs the light which develops photosynthesis
If a plant doen’t mave enough minerals (magnesium) it will die because it cannot grow
What do plants use the glucose from photosynthesis for
- respiration
- converted into insoluable startch
- produce lipids or oils
- produce cellulose
- produce amino acids
why do plants convert glucose to cellulose
to stengthen the cell wall
why do plants convert glucose to startch
- it is insoluable ~ doen’t affect osmosis
- provides an energy store when it is too dark
- produce tubers and bulbs to help survive through the winter
why and how do plants use glucose in amino acids
they combine sugars with nitrate ions
the amino acids built up into proteins to be used as enzymes
why do carnivourous plants convert glucose into amino acids
so they can make enzymes to digest the insects they trap
why do plants convert glucose into lipids
to be used as an energy store, make the cell wall stronger or as an energy store in seeds
How do commercial greenhouses control photosynthesis
- control temperature
- control light levels
- control CO2 levels
What is the system which big commercial greenhouses use called
hydrophonics
what are the benefits of hydrophonics
- bigger yield = more profit
- clean crops
- no need to plough or prepare land
- less staff
- shorter harvest
what are the disavantages of hydrophonics
- higher gas bills
- higher electricity bill
- expensive monitoring equipment
How do you test for startch
- add a few drops of test solution to spotting tile
- add iodine solution
- observe
what is the colour change for successful startch
orange-brown to blue-black
how do you test for glucose
- add test solution to test tube
- add benedict’s solution
- place in water bath at 80 for 10min
- observe
What is the colour change for successul glucose
blue to green/orange/brick red
how do you test for protein
- add test solution to test tube
- add biuret solution
- observe
What is the colour change for successful protein
blue to purple
how do you test for lipids
- add test solution to test tube
- add 2cm^3 water
- add 3 drops of sudan III and shake gently
- observe
what is the colour chage for successful lipids
a red layer forms at the top of the solution
What is the solution for testing startch
iodine solution
What is the solution for testing glucose
benedict’s solution - copper sulfate
What is the solution for testing protein
biuret solution - copper sulfate and sodium hydroxide
What is the solution for testing lipids
Sudan III
explain what a variegated leaf is
A leaf which is not just green, it is white as well so contains no chlorophyll in those regions and can’t photosynthesis in white regions
describe the method for testing light intensity
- cut pondweek at 45 angle
- place cut end in funnel
- put funnel in beaker and fill with water
- add a spatula of sodium hydrogen carbonate
- change distance of lamp and how it affects bubble number
hwo do you calculate ligth intensity
1 / distance^2
light intensity decreases as the distance between the light source and the plant increases, what is this called
inverse proportionality
what do plants abosrb from the soil to make protein
nitrate ions
if it is a sunny day what is most likely to be limiting the rate of photosynthesis
carbon dioxide concerntration
as a lamp is moved closer to a plant what else increases other than light intensity
temperature
what other sunstance is used for food storage in plants other than starch
fat, oils, lipids
why is glucose unsuitable for storage in plants
it is soluable
