photosynthesis and energy Flashcards
Function of chloroplast
Photosynthesis takes place
Absorbs light energy
Light is absorbed by complexes of pigments, such as chlorophyll
Fluid enclosed in chloroplast is called stroma + is the site of many chemical reactions resulting in the formation of complex molecules
Structure of chloroplast
Network of membranes = large SA = Large SA:V
membranes form flattened sacs called thylakoids, which stack to form grana
Grana are joined by lamellae- create large SA which allows for the maxium absorbtion of light to excite electrons
Fluid enclosed is called Stroma which contains enzymes which catalyses the reactions of the light dependant stage
Contain lots of ribosomes for the translation of protiens that are used in photosynthesis
Why leaves change colour in autumn
Chlorophyll breaks down, meaning green light stops reflecting
Other pigments of different colours ( that are present all year) then reflect their light
Need for energy
Active transport - uptake of nitrates, phloem loading, selective reabsorption
Anabolic reactions - building of polymers: proteins, polysaccharides, and nucleic acids essential for growth
Movement - brought about by cilia, flagella, or muscle contraction
Respiration- organic molecules, glucose, are broken down into smaller inorganic ions
What colours have: the highest light energy and longest wave length
ROYGBIV
violet - highest light energy
Violet to red wavelength increase
What do pigment molecules Absorb
Specific wavelength (colours) of light and reflect others
Function of pigemnts
Pigments arranged in light harvesting clusters to abosrb different wavelengths of light, clusters are known as photosystems
In a photosystem pigment molecues are arranged in a funnel like structre in the thylakoid membrane allowing energy to be passed down untill it reaches the primary pigment reaction centre
By having a range of pigments the range of wavelngths that can be absorbed expands
Ps1 vs ps2
Ps1 known as P700 as peak absorption are wavelengths 700nm
Ps2 known as p680 as peak absorption are wavelengths 680nm
What occurs in reaction centre
Photo excitation
Where electrons get boosted to higher energy levels
As they drop down chemical energy is released
Non cyclic Light dependant reaction
- photolysis of water ( producing h+ and e-) 4 photos of light breaks down 1 water
- photosystem 2 absorbs the light
- excited electrons pass from primary acceptor,ps2, towards ps1 via electron transport chain
- as electrons fall to a lower energy level, whilst being transported energy is harnessed and converted from ADP to ATP
- PS1 also absorbs light. Electrons from primary pigment (p700) are excited
- carrier molecules NADP combines with these electrons ( and h+) to produce reduced NADP
Cyclic Light dependant reactions
Only uses ps1
Excited electrons from ps1 chlorophyll molecule (p700) are captured by electron acceptors
It’s then passed back to ps1 via electron transport chain
During this the energy is released makes ATP from ADP and inorganic phosphate
No reduced NADP is made
Light independent reaction detailed
3co2 is added 3 ribulose biphosphate to form a 3, 6 carbon molecules
This molecule is very unstable so it breaks down into 6 glycerate 3 phosphate molecules
Energy from ATP and hydrogen ( sourced from reduced NADP) are used to convert 6GP into 6TP
1 triose phosphate is removed to make glucose
5 triose phosphate is used in a regenerative reaction converting 5TP - 3RuBP to restart the cycle
Summary of Calvin cycle
Fixation- co2 is fixed ( incorporated into an organic molecule, RuBP) in the first step
Reduction- gp is reduced to TP by the addition of hydrogen from reduced NADP using energy supplied by ATP
Regeneration- RuBP is regenerated from the recycled TP
TP moleucle that is removes is used as a starting material or the synthesis of carbohydrates, lipids and amino acids
function of light dependent reaction
energy from sunlight is absorbed and used to form ATP
hydrogen from water is used to reduce co enzyme NADP to reduced NADP
where light in/dependant reactions take place
light dependant take place in the thylakoids
light independent reactions take place in the stroma
stack of thylakoids
granum
Products of light dependant stage of photosynthesis
Reduced NADP
ATP
oxygen
Describe how thylakoids are adapted to function
Contains electron transporter chains
Membrane has large SA for light absorption
Contain photosystems/pigments
How will structure of leaf change if in shady environment
- larger SA needed
- more chloroplasts
- more thylakoids
How are heterotrophic organisms reliant on plants
- Plants produce organic molecules such as amino acids or glucose during the Calvin cycle
- heterotrophic animals must eat plants in order to attain organic molecules
- organic molecules are used by animals for respiration
Primary pigments and accessory pigment
Primary - Chlorophyll a (yellow / green)
Accessory - Chlorophyll b (blue green) , carotenoids (orange), xanthophyll ( yellow)
Advantage of having a range of accessory pigments
Absorb different wavelengths of light to maximising photolysis and photophosphorylation
2 different polysaccharides that can be synthesised from end products of the light independent stage of photosynthesis
Amylose amylopectin starch
AND
Cellulose
What are fat droplets in stroma used for
Reserve of raw material for membrane formation and phospholipids
Why measuring co2 uptake is better or worse than measuring o2 production for measuring rate of photosynthesis
O2 is a waste product of photosynthesis that could be used in respiration causing us to underestimate
Co2 produced by respiration could be used in photosynthesis lowering co2 intake
How light is harvested in chloroplast membranes
Pigments are found in the antenna complex
Photon ( light energy) is absorbed by pigment molecules
Electrons, from photolysis of water (ps2) or electron transport chain (ps1) are excited and move to higher energy levels and bounce between pigments
Energy is harnessed and passed to reaction centre PS2
Range of accessory pigments are needed to allow as much light to be absorbed
How are electrons of PS1 and PS2 replace
PS2- photolysis of water
PS1 - replaced by electrons from the electron transport chain
Purpose of photosynthesis vs respiration
Photosynthesis- trap energy
Respiration release energy
How does wavelength effect penetration of light
Shorter wavelength and therefore higher frequency can penetrate more ( deep in the ocean)
What is produced during the Calvin cycle
Organic molecules- lipids, amino acids, glucose
From molecule TP that is removed
What process is prevented due to a fault at ps2
Non cyclic phosphorylation
Photosynthesis and respiration equations
Photosynthesis: 6co2 + 6h2o ( with light energy) = 6o2 + c6h12o6
Respiration: glucose + oxygen = water + carbon dioxide + ATP
Cyclic photophosphorylation vs non cyclic photophosphorylation
Photosystems involved - PS1 , PS2
photolysis of water - no, yes
Electron doner - P700 in PS1, water
Final electron acceptor- P700 in ps1, NADP
products - ATP, ATP oxygen and reduced NADP
Factors effecting rate of photosynthesis
Light intensity - the greater the light intensity the faster the light dependant stage can occur producing more ATP and reduced NADP for the caliv cycle
Carbon dioxide concentration - required for the light independant stage of photosynthesis where CO2 is combined with RuBP during carbon fixation
Temperature - calvin cycle is effected by temprature as the light independant reactions are enzyme controlled. As temp increases KE of particles increases meaning there is more succeful collisions and reactions happen faster
Water availability
Presence of photosynthetic pigments
Effects of light intensity and carbon dioxide concentration on levels of GP,TP and RuBP
- A decrease in light intensity causes a decrease in TP and RuBP concentration but a slight increase in GP concentration as it is not converted to TP due to lack of reduced nadp so it bulids up. RuBP conc decrease as lack of TP means RuBP will not form
- low concentration of co2 mean that RuBP is not fixed to form the unstable 6 carbon molecule, therefore TP and GP concentration decrease
Structures in chloroplasts
Outer membrane Inner membrane Stroma Lamellae Thylakoid Granum
Source of co2
Hydrogen carbonate or burning fuel
Measuring oxygen production from plant submerged in water
Factors that could effect the results
Co2 availability in water
Wether product is soluble in water
Air spaces in the spaces
How water stress can reduce the rate of photosynthesis
Water stress stimulates stomatal closure, which decreases carbon dioxide available for photosynthesis
This means less carbon dioxide is fixed in the Calvin cycle and triose phosphate production decreases which forms starch and other organic substances
