Nutrition Flowering plants Flashcards
Topic 2E .1
photosynthesis is an ____ reaction
endothermic
in photosynthesis, energy from sunlight is transferred to __
the chloroplasts in green plants
in photosynthesis, energy from sunlight is absorbed by
chlorophyll
green plant use the energy from the sun to make …
the carbohydrate glucose from the raw materials carbon dioxide and water
At the same time, oxygen is made and released as a waste product
photosynthesis is
the process by which plants manufacture carbohydrates from raw materials using energy from light
word equation for photosynthesis
carbon dioxide + water—— (light, chlorophyll)—– glucose + oxygen
symbol equation for photosynthesis
6CO2 + 6H2O —– C6H12O6 + 6O2
why is photosynthesis an important process
because it converts light energy into chemical energy which is stored in glucose.
what is a limiting factor
something present in the environment that is in such short supply that it restricts life processes
main factors that limit rate of photosynthesis (3)
- light intensity
- temperature
- carbon dioxide concentration
how does temperature affect the rate of photosynthesis
the temp of the environment affects how much kinetic energy the particles have, so the lower the temperature, the less energy particles have resulting in fewer successful collisions.
Increasing the temp increases kinetic energy of particles, increasing likelihood of successful collisions between reactants and enzymes ( resulting in formation of products)
At higher temperatures, enzymes that control the processes of photosynthesis can be denatured which can reduce rate of photosynthesis
how does light intensity affect the rate of photosynthesis
chlorophyll uses light intensity to perform photosynthesis but it can only do it as quickly as the light is arriving
if the light intensity is increased, the rate of reaction also will but only up to a certain point
if it goes beyond that point it won’t make any difference because it will be either TEMP or CO2 level that is the limiting factor
if temperature is a limiting factor, is it usually too low or too high and why
too low, things need warming up a bit
how does carbon dioxide concentration affect rate of photosynthesis
co2 is pretty scarce in the air, and is one of the raw materials needed for photosynthesis.
more carbon dioxide that is present, the faster the reaction can occur
This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply, this factor becomes the limiting factor
Waxy cuticle (what does it do)
Protective layer on top of the leaf, prevents water from evaporating
upper epidermis (what does it do)
Thin and transparent to allow light to enter palisade mesophyll layer underneath it
palisade mesophyll (what does it do)
Column-shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
spongy mesophyll (what does it do)
Contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases (mainly carbon dioxide)
lower epidermis (what does it do)
Contains guard cells and stomata
guard cell (what does it do)
Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
stomata (what does it do)
Where gas exchange takes place: opens during the day, closes during the night. Evaporation of water also takes place from here. In most plants, found in much greater concentration on the underside of the leaf to reduce water loss
vascular bundle (what does it do)
Contains xylem and phloem to transport substances to and from the leaf
xylem (what does it do)
Transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
phloem (what does it do)
Transports sucrose and amino acids around the plant
why does the leaf have a lot of stomata
to allow gas exchange to happen faster
why does the leaf have air spaces int he spongy mesophyll layer
maximize surface area to volume ratio to maximize diffusion of gasses
why is the leaf thin
to allow rapid diffusion for gaseous exchange
why does the leaf have a broad shape
to increase surface area to catch more light
how is the leaf adapted for photosynthesis (6)
- large surface area
- network of veins in the leaf to transport water
- chlorophyll in leaves absorbs light energy
- epidermis is thin
- leaf is thin
- spongy mesophyll layer has air spaces to allow CO2 to diffuse
- waxy cuticle to reduce water loss by evaporation
what are two fundamental mineral ions required by plants
magnesium and nitrogen
where do plants get mineral ions from
the soil
if there isn’t enough of one of the mineral ions, what happens
the plants suffer deficiency symptoms
function of mineral ion nitrate
needed to make amino acids/proteins
needed for cell growth
deficiency symptoms of nitrate
causes stunted growth and yellowing of leaves
magnesium ion function
needed to make chlorophyll
deficiency symptom of magnesium
causes yellowing of leaves between the veins
what is the yellowing of the leaves called
chlorosis
PRACTICAL INVESTIGATING PHOTOSYNTHESIS- oxygen
Take a bundle of shoots of a type of pondweed
Submerge them in a beaker of water underneath an upturned funnel
Fill a boiling tube with water and place it over the end of the funnel
you need to place a light at a certain distance from it as well so as to trigger photosynthesis
As oxygen is produced, the bubbles of gas will collect in the boiling tube, count the number of bubbles that form in a minute
relight a glowing splint over the test tube
PRACTICAL - show that starch is produced in photosynthesis
- take a leaf from a plant
- boil it in water for 30 seconds (which kills it)
- boil it in ethanol ( BUT the bunsen burner needs to be turned off, so have the boiling water and add a test tube of ethanol along with the plant inside it)
- the chlorophyll will come out and the ethanol will become green
- After a minute, take leaf out and rinse it under some cold water and spread it out on a white tile
- add a few drops of iodine on it
- if leaf is yellow = destarched
if leaf is blue/black = contains starch
when testing for starch in al leave, why might it turn out yellow ? what does that mean
that the leaf has been kept in the dark a long time so has been destarched
how do you prove that chlorophyll is needed for photosynthesis-practical
- get variagated leaves from a plant which are partly white and partly green (meaning there is only chlorophyll in some areas)
- test that leaf for starch and only the green part will have a positive result
how can you prove that CO2 is needed for photosynthesis
you need to put a plant in a dark cupboard for 24hours
surround both plants with a sealed conical flask but one of them will also have soda lime or potassium hydroxide in it.
leave them for 24hours
do the iodine test
the leaf with the soda lime will turn out yellow as the CO2 was absorbed all by it and so no photosynthesis happened / no glucose was made
how do you investigate how light is needed for photosynthesis
you need to put a leaf in a dark cupboard for 24hours, and you also need a leaf that has been in the sun, partly( cover part of it with aluminium foil) for 24 hours.
perform starch test with iodine solution
