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Summary AQA A-level Biology Notes - Energy Transfers $11.95
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Summary AQA A-level Biology Notes - Energy Transfers
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  • Unit 5 - Energy transfers in and between organisms
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Biology notes that will help you get an A* Notes have been made to cater to the AQA Biology Mark Scheme Contains everything on the spec for Energy Transfers: - Photosynthesis - Respiration - Ecosystems - Farming - Nutrient Cycles - Eutrophication

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Document information

  • December 21, 2024
  • 15
  • 2023/2024
  • Summary

Subjects

  • a levels
  • biology
  • revision
  • notes

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  • A/AS Level
  • AQA
  • A Level Biology
  • Unit 5 - Energy transfers in and between organisms
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Photosynthesis
Plants convert sunlight energy into chemical energy in the form of organic molecules
GCOzHeO CHOs"60 .




It has 2 stages: Key words:
-
Light dependent stage in the thylakoid Metabolic pathway - series of small reactions
membrane uses light energy to produce controlled by enzymes (photosynthesis & respiration)
reduced NADP + ATP Photophosphorylation - adding phosphate to a
-




Light independent reaction occurs in molecule of light
the stroma of chloroplasts and Photolysis - splitting of a molecule using light energy
-




produces organic products using Photoionisation - when light energy ‘excites’
·




Calvin cycle electrons in an atom or molecule, giving them
more energy and causing them to be released.
Coenzymes: This makes the atom a positively-changed ion.
-
A coenzyme is a molecule that aids the function of an enzyme
-
They transfer a chemical group from one molecule to another
-
Coenzyme used in photosynthesis is NADP which transfers hydrogen so it reduces or oxidises a molecule

Chloroplast:
Thylakoids are stacked up into structures called grana




.
-
Grana are linked by bits of thylakoid membrane called lamellae
-
Chloroplasts contain photosynthetic pigments Thylakoid membrane
which are coloured substances that absorb DNA Ribosomes - produce proteins for
photosynthesis quickly
light. Pigments are found in the thylakoid Chloroplast envelope




·
membranes - they're attached to proteins.
Starch
Protein and pigment is called a photosystem. Grana

-
2 photosystems are used by plants to capture light
energy. Photosystem I absorbs light best at a
Stroma
wavelength of 700nm and photosystem II absorbs Lamellae

light best at 680nm.
-
Stroma is gel-like substance which contains enzymes, sugars and organic acids
i
Carbohydrates produced that are not used straight away are stored as starch grains in the stroma

, Light Dependent Reaction
·
Energy from photoionisation of chlorophyll is used for:
Photophosphorylation: making ATP from ADP + Pi
Making reduced NADP from NADP
Photolysis: splitting water into protons, electrons and oxygen

Non-cyclic photophosphorylation:
-
Photosystems are linked by electron carriers
·
Electron carriers are proteins that transfer electrons
·
Photosystems and electron carriers form an electron transport chain
↑
Electron transport chain is a chain of proteins through which excited electrons flow

Photoionisation: .Photolysis of water:
2
· Light energy is absorbed by PSII which excites electron Light energy splits water into protons,
-




in chlorophyll electrons and oxygen
-
Electrons move to a higher energy level HeO 2H" + @
· These electrons leave chlorophyll and move down electron The electrons formed replace those that
↑




transport chain to PSI leave PSII
= Oxygen is waste product that diffuses from
stomata - water is oxidised into oxygen gas
3 Excited electrons lose energy as they move down ETC
This energy is used to transport hydrogen ions from
stroma into the thylakoid
=
H ,0

↑
This forms a proton gradient across thylakoid 202
2H" +




membrane L
Light energy is absorbed by PSI which
-
Protons diffuse back into the stroma, down their excites electrons again to an even higher
concentration gradient, through the enzyme ATP energy level
synthase that is embedded in the membrane -
Electrons and a proton are transferred
The energy from this movement combines ADP and Pi to NADP to form reduced NADP


·
to form ATP
" =>

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