- Biology notes that will help international a level students prepare for their unit 4 exam.
- Consist of Chapter 5B: Ecology.
- 100% typed notes
- Useful tools to help learn and memorise them like emojis, diagrams, and shortcuts.
,1) Introduction - photosyntesis
= series of chemical reactions that occurs in autotrophs by which plants produce
oxygen and glucose by using solar energy to combine CO2 and H2O
• It converts light energy into chemical energy which is used to split bonds in water
molecules, releasing hydrogen and oxygen
Combines with CO2 Released as a
and is stored in waste product
glucose (fuels
respiration)
2) The role of ATP in photosynthesis
• The molecule adenosine triphosphate (ATP) is used to transfer and supply energy
within cells; universal energy currency. It diffuses within cells where it is needed
Structure of ATP
It is a nucleic acid
A phosphorylated nucleotide which
consists of
• a nitrogenous base (adenine), a ribose
sugar, and three phosphate groups
ATP is produced by adding an inorganic
phosphate to ADP:
• The hydrolysis of ATP is know as dephosphorylation which is catasyled by
ATPase
• ATP can be produced during the electron transport chain which releases
energy for the phosphorylation of ADP. This occurs in the mitochondria during
respiration and in chloroplasts during photosynthesis (= photophosphorylation
bc energy from sun)
, 3) Chloroplasts
= plant cell organelles surrounded by a double membrane where photosynthesis occurs
LUMEN Conditions differ form
stroma like the proton
gradient (very small volume
so protons dvp fast)
Cytoplasm like fluid which countains
enzymes, sugars, ribosomes, chloroplast
DNA, starch grains and lipid droplets
Surrounded by a thylakoid
membrane which contain
ATP synthase, photosystems
Creates large surface area for max light
absorption (as more photosystems) and
production of ATP (more membrane area for
proteins)
Photosystems
There are two types of photosystems:
Photosystem I (PSI) which absorbs wave lengths of 700nm
Photosystem II (PSII) which absorbs wave lengths of 680nm
• Each system contains different
combinations of chlorophyll,
carotenoids and many more pigments.
They are arranged in a way that as
much light is absorbed and reaches the
primary pigment reaction centre
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