photosynthesis and energy Flashcards
(39 cards)
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
