Energy transfers in and between organisms Flashcards
Chloroplasts
Cellular organelles where photosynthesis takes place
Structure of chloroplast
Double membrane, stroma, thylakoids, lamellae, chloroplast DNA, ribosomes, starch grains, grana
Function of stroma
A fluid-filled matrix where the light-independent stage of photosynthesis takes place. Within the stroma are a number of other structures such as search grains.
Function of grana
Stacks of thylakoids. Membranes of grana create large surface area increasing number of light dependant reactions to take place.
Function of thylakoids
Series of flattened fluid filled sacs part of a membrane system that contains pigments, enzymes and electron carriers
Site of photosynthesis
The leaf
- Chloroplasts
Photosynthesis equation
6CO2 + 6H2O –> C6H12O6 + 6O2
carbon dioxide + water –> glucose + oxygen
Oxidation
Loses electrons
Gains oxygen / loses hydrogen
Reduction
Gains electrons
Loses oxygen / gains hydrogen
Photoionisation
Light energy is absorbed by the plant cells. This excites the electrons in the chlorophyll, causing them to leave the molecule and be taken up by an electron carrier. As a result the chlorophyll becomes ionised, oxidised
Chemiosmotic theory
As protons flow down their concentration gradient through ATP synthase the energy from the movement of protons is used to phosphorylate ADP to ATP (photophosphorylation) in a process called chemiosmosis
Photolysis of water
The splitting of water molecule bonds in the presence of light
Products of light dependant reactions
Reduced NADP
ATP
Importance of photolysis
As light hits the chlorophyll, it loses an electron and for the molecule to continue absorbing light the electrons must be replaced. The splitting of the water provides an electron to replace lost one
Photolysis equation
2H2O –> 4H+ + 4e- + O2
Water –> hydrogen + electron + oxygen
Use of oxygen in the photolysis of water
It is a waste product of the reaction and so is either used in respiration or diffuses out of the leaf
Fate of electron from PS II
Loses energy to channels in transport chain and replaces electron from PS I
What is a photosytem?
Embedded in thylakoid membrane
Funnel- like structures
Absorbs light energy and transfers to primary reaction centre
Accessory pigments
Pigments that help with photosynthesis by capturing light energy from different wavelengths
- Chlorophyll b, carotenoids, xanthophyll
Reaction centre
Primary pigment centre conating principal light absorbing pigment
Photosystem II (P680)
Absorbs red light
Wavelength of 680 nm (absorption peak)
Photosystem I (P700)
Absorbs orange light
Wavelength of 700 nm (absorption peak)
Abbreviation of RuBP
Ribulose biphosphate
How many carbons in compound RuBP
5-carbon compound
Abbreviation of ribusco
Ribulose biphosphate carboxylase
Abbrevation of GP
Glycerate 3-phosphate
How many carbons in GP
3-carbons
Abbrevation of TP
Triose phosphate