C1.3 Photosynthesis SL Flashcards
give the chemical equation for photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
give the word equation for photosynthesis
carbon dioxide + water -> glucose + oxygen
what does photosynthesis do?
photosynthesis generates a chemical store of energy in the form of carbohydrates
it converts light energy to chemical energy
give an example of an autotroph
photosynthetic organisms
give a brief summary of light dependent reaction?
use light energy to produce ATP and to split water (photolysis), making H+ ions
give a brief summary of light independent reaction?
use ATP and H+ ions to “fix” CO2, making glucose
what is photolysis?
light splits 6H2O into O2 and H+ ions
what happens to the products of photosynthesis?
- some oxygen is a waste product
- glucose is either used for respiration or stored as starch
Why will desert plants die if they carry out light independent reactions? and what are these plants called?
- stomata is open b/c needed for gas exchange
- but cause too much transpiration and die from dehydration, so do light independent reaction at night
some plants close their stomata during the day and take up CO2 at night, when the air temperature is lower. what are these plants called?
CAM plants
what are the 2 polysaccharide molecules found in plants? and what are they used for?
- starch is a chemical store of energy
- cellulose builds up the plant cell wall
What is the process through which monosaccharides are combined to make carbohydrates?
glucose + glucose → (C6H10O5)n
- condensation
- bond in product called glycosidic bond → covalent bond
what is the bond between monosaccharides when they are combined?
glycosidic bond (a covalent bond)
what helps absorb different wavelength of color in plants?
pigments
= chlorophyll (in the organelle chloroplast)
why does a leaf look green?
- chlorophyll is the main photosynthetic pigment
- white light = all colors (wavelengths)
- in plants, blue and red wavelengths are absorbed, green light is reflected
why do leaves die in autumn?
- not a lot of sunlight
- less area of plant that needs to be kept alive through respiration
why should a plant make different pigments to absorb different wavelengths of light?
- to maximise light that it can absorb
the pigments in photosynthetic organisms (chlorophyll), absorb useful wavelengths of light
can low frequency radiation be used in most organisms?
low frequency radiation is low in energy - too low to be used in most organisms
what is the y axis of the absorption spectrum?
- y axis: absorption of light
- how much light was absorbed
what can be observed on the absorption spectrum?
- how much light was absorbed
- blue + red high, green low
what is the y axis of the action spectrum?
y axis: rate of photosynthesis
- how much of that light was used in photosynthesis
what does the action spectrum show?
- how much of that light was used in photosynthesis
- blue higher than red?
is CO2 a limiting factor for light independent reaction?
yes
oxygen is a ______ of photosynthesis
by-product
usually a waste product
where does oxygen in photosynthesis comes from? (in simple terms)
from photolysis (splitting of H2O)
what is the effect of photolysis on the concentration of oxygen inside chloroplasts and explain
- photolysis increases concentration of oxygen inside chloroplasts
- causes oxygen to diffuse out of chloroplasts then out of leaf cells to air spaces inside the leaf
- oxygen diffuses thru stomata to the air outside the leaf
what is cyanobacteria and explain
- cyanobacteria
- when there was no oxygen
- able to carry out photosynthesis
- only possible if oxygen conc (around 30%) was really high
- cyanobacteria was really good at releasing oxygen
- eukaryotes ingested cyanobacteria and inherited its abilities
- endosymbiosis occurred
