5.2.1- Photosynthesis Flashcards
what are autotrophs?
organisms that use light energy/chemical energy to synthesise organic molecules from inorganic molecules
what are the two types of autotrophs?
-chemoaytotrophs
-photoautotrophs
what are chemoautotrophs?
autotrophs which use energy derived from chemical reactions.
what are photoautotrophs?
autotrophs which use energy derived from sunlight to convert carbon dioxide and water to complex organic molecules such as glucose during the process called photosynthesis
what are the examples of autotrophs?
-plants (photo)
-cyanobacteria (photo)
-protoctists (photo)
-bacteria (chemo)
What are heterotrophs?
organisms that ingest and digest complex organic molecules releasing in the chemical potential energy stored in them
what are examples of heterotrophs?
-animals
-fungi
-some bacteria
how are photosynthesis and respiration linked?
-the equations are the opposite of each other
-photosynthesis is endothermic while respiration is exothermic
-photosynthesis supplies oxygen needed for respiration, and also supplies the complex organic molecules needed for respiration
what is an endothermic reaction?
when more energy is used to make bonds compared to breaking bonds
What is an exothermic reaction?
When energy is released because more energy is used to break bonds compared to making bonds
what is the equation of photosynthesis?
water + Co2 ——> (sunlight) glucose + O2
how do plants gain water and CO2 for photosynthesis?
-water= absorbed by the roots
-CO2= enters through the stomata of the leaf
where does photosynthesis take place in the plants?
in chloroplasts
what are the two stages of photosynthesis?
-light dependent stage
-light independent stage
where in the chloroplast does the light dependent stage take place?
in the grana
where in the chloroplast does the light independent stage take place?
in the stroma
what are the 7 adaptations of chloroplasts?
-large SA to absorb light
-thylakoids/lamellae contain photo systems for LDS
-photosynthetic pigments for LIS
-stroma contains enzymes for LIS
-stroma contain lipid droplets and starch grains to store products of photosynthesis
-loops of DNA to code for some of the proteins needed for photosynthesis
-ribosomes to make these proteins
what are photosynthetic pigments?
molecules that absorb light energy
why are photosynthetic pigments different colours?
because they are different wavelengths and so they absorb and reflect different parts of the visible spectrum as possible, allowing maximum energy
how many different photosynthetic pigments are there and what are they called?
1- chlorophyll a
2- chlorophyll b
3- carotene
4- xanothophyll
what stage are photosynthetic pigments used in?
the light dependent stage
what colour and type of pigment are chlorophyll a and b?
a= blue-green, primary
b= yellow-green, accessory
what colour and type of pigment are carotene and xanthophyll?
carotene= orange, accessory
xanthophyll= yellow, accessory
where is chlorophyll found?
the reaction centre
where are the accessory pigments found?
light harvesting system
where are the pigments arranged?
in funnel shaped structures called photo systems which are embedded in thylakoid membranes and lamellae membranes
what are the two types of photo system?
PS1 and PS11
give detail on photo system 1?
type of chlorophyll a= P700
peak absorption= 700nm
main location= intergranal lamallae
give detail on photo system 2?
type of chlorophyll a= P680
peak absorption= 680nm
main location= grana (thylakoids)
what are the two pathways of LDS?
-cyclic photo phosphorylation
-non-cyclic photo phosphorylation
what occurs during cyclic photophosphorylation?
-photon of light is absorbed by PS1
-electrons in primary pigment become excited to a higher level energy
-electrons are emitted from P 700 and then captured by an electron acceptor
-The electrons return to P 700 via a chain of electron carriers
-Energy is released as electrons are passed down the chain of electron carriers
-this energy is used to synthesise ATP from ADP and Pi
what is the only product of cyclic photophosphorylation?
ATP
what occurs in noncyclic photophosphorylation?
-photons of light are absorbed by both photosystems and electrons of both primary pigments become excited to higher energy levels
-electrons emitted from P 700 in P6 80 are captured by electron acceptors, but they do not return to either
-electrons from P 700 passed down a chain of electron carriers and I used to reduce NADP
-The electrons from P6 80 are passed from down a chain of electron carriers releasing energy to make ATP
-The electrons from P680 in PS11 combine with P700 in PS1
-photolysis
-H+ ions from photo lysis accumulate in thylakoids, ATP is used to pump these from stroma across thylakoid membrane and into thylakoid
-H+ ions generate energy by chemiosmosis, and they diffuse down conc gradient via ATP synthase
-more ATP is formed at ATP synthase
-H+ ions combine with electrons from P700 and coenzyme NADP to make reduced NADP
how are the electrons lost from P680 replaced?
replaced by electrons released by photolysis of water, which releases H+ ions and oxygen
what is the equation of photolysis of water?
H2O ——> 2H+ + 1/2 O2
what are the three products of non-cyclic photo phosphorylation?
-ATP
-Reduced NADP
-Oxygen
what is the light independent stage?
the stage of photosynthesis where light is not directly needed, but stops if light is not available as it used products of the LDS
where does the LIS occur?
in the stroma of the chloroplasts
what happens during the Calvin Cycle/LIS?
-CO2 from the air diffuses into the leaf through
open stomata into palisade mesophyll cells and into chloroplasts
-In the stroma CO2 combines with ribulose bisphosphate to form an unstable 6C compound (carboxylation) and is catalysed by enzyme rubisco
-unstable compound splits into 2 glycerate-3-phosphate
-ATP and reduced NADP from the LDS are used to convert GP into triose phosphate
what is the fate of TP during the Calvin Cycle?
-5/6 are recycled by phosphorylation, to make RuBP
-rest of TP (1/6) is used to make glucose/starch, lipids and amino acids/proteins
what does the Calvin Cycle look like?
RuBP
+ RuBisCo
+ CO2
= 2 x GP
-ATP—-> ADP + Pi
- reduced NADP—-> NADP
= 2 x TP
-glucose
-ATP—-> ADP + Pi
= RuBP (regeneration)
how many cycles of the Calvin Cycle does it take to form glucose?
6
what is the role of the enzyme rubisco during LIS?
it combines with CO2, helping form GP
what are the 3 main factors that effect the rate of photosynthesis?
-light intensity
-CO2 concentration
- temperature
what are the factors that effect photosynthesis known as ?
limiting factors
how does CO2 conc effect the rate?
-more CO2 = faster carboxylation of RuBP= more GP, more TP = faster rate of photosynthesis
what happens if CO2 conc is too high?
-RuBP conc is too low as it is used up quickly
-GP and TP conc are high and they accumulate
how does light intensity effect the rate?
more light= more excited electrons in the LDS= more photo phosphorylation = more reduced NADP and ATP= faster reduction of GP= more TP, more RuBP= faster rate
what happens at high light intensity?
-GP conc is low (used up quickly)
-TP and RuBP conc is high (accumulate)
how does temperature effect the rate?
each reaction in LIS is catalysed by enzymes
-increased temp= increased ke of enzyme and substrate molecules= more successful collisions between them = faster rate
what happens when temperature is too high?
-denatures enzymes used in LIS and needed for photolysis in LDS
-reduced levels of ATP and reduced NADP
-plant will wilt, stomata will close and so CO2 uptake is reduced
what is used to measure the rate if photosynthesis?
a photosynthometer, which is an apparatus that measures the rage of oxygen production and so measures the rate of photosynthesis
what other method can investigate the factors effecting the rate of photosynthesis?
the leaf disc method
how does the leaf disc method help explain rate of photosynthesis?
the quicker the discs float. the quicker the rate of photosynthesis
