f214 photosynthesis

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Module 3: Photosynthesis
(a) Define the terms autotroph and heterotroph
Autotroph ­ an organism that uses light or chemical energy and inorganic molecules to synthesise
complex organic molecules.
Heterotroph ­ These are organisms that ingest and digest complex organic molecules releasing the
chemical potential energy stored in them.
(b) State that light energy is used during photosynthesis to produce complex organic
Light energy or photons are used in photosynthesis, more notably the light dependent reaction, to
produce complex organic molecules like sugar.
(c) Explain how respiration in plants and animals depends upon the products of
Products of photosynthesis are needed to produce ATP, an energy carrying molecule, necessary for
metabolic processes. Plants are capable of producing their own complex organic molecules through
photosynthesis but animals need to consume plants or plant products to gain the complex organic
(d) State that in plants photosynthesis is a twostage process taking place in chloroplasts
Photosynthesis is a two stage process occurring in the chloroplast. The first stage is the light
dependent reaction where its product, ATP and NADPH, are used for the second stage. The second
stage is called the light independent reaction or Calvin cycle where hexose sugars are made using
the product of the light dependent reaction and CO2
(e) Explain, with the aid of diagrams and electron micrographs, how the structure of
chloroplasts enables them to carry out their functions
Outer membrane Can allow certain ions through
Inner membrane Is composed of transport proteins and is folded thin plates called lamellae
Granum Stacked up lamella
Intergranal lamella Links grana together
Thylakoid Flattened membrane that contains photosystems. They make up the granum
Stroma The fluid filled matrix that contains starch grains, oil droplets, DNA and
prokaryote ribosome
Define the term photosynthetic pigment
Photosynthetic pigments ­ molecules that absorb light energy or photons

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Explain the importance of photosynthetic pigments in photosynthesis
They gather photons in order to allow light dependent reactions to occur. Secondary pigments work
to make sure that primary pigments get the maximum possible photons that they can have.
(h) State that the lightdependent stage takes place in thylakoid membranes and that the
lightindependent stage takes place in the stroma,
Light dependent reaction takes place in the thylakoid membrane and uses H2O producing O2,
ATP and NADPH.…read more

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NADPH is used to hydrogenise GP molecules into TP molecules
ATP is used to phosphorylate GP molecules into TP molecules and for the regeneration of
(l) Explain the role of carbon dioxide in the light-independent stage (Calvin cycle)
It serves as a source of:
Carbon ­ important for structures, energy stores
Oxygen ­oxygen acceptor, energy stores
(m) State that TP can be used to make carbohydrates, lipids and amino acids
Other than regenerating RuBP TP has many other applications:
It can become glycerol and…read more

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