Unit 6 energy, respiration and photosynthesis A Level

Unit 6: Energy, respiration and
photosynthesis
B M Subramanya Swamy M.Sc. B.Ed.
CIE Co - ordinator & Examination Officer
Kanaan Global School
Jakarta
Indonesia
swamy@kanaanglobal.sch.id

Introduction
• 2 main types of nutrition
• Autotrophic nutrition
chemoautotroph
photoautotroph
Heterotrophs

4
Discovery of Photosynthesis
C. B. van Niel, 1930’s
-proposed a general formula:
CO2+H2O + light energy CH2O + H2O + 2O
where H2A is the electron donor
-van Niel identified water as the source of the O2
released from photosynthesis
-Robin Hill (in the 1950s) confirmed van Niel’s proposal
that energy from the light reactions fuels carbon
fixation (making glucose from CO2)

Photosynthesis
The process by which organisms use carbon di
oxide and water to manufacture food.
The energy needed for synthesis is supplied by
light which is absorbed by the organisms and
subsequently converted by them into
chemical energy in the presence of chloroplast

Structure of dicotyledonous leaf and chloroplast

Structure of chloroplast
• Biconvex shape
• 3 – 10 micro meter in diameter
• Double membrane
• Internal membrane – flattened fluid filled sacs called thylakoid
• Pigments – chlorophyll – held – thylakoid membrane
• Cluster – pigment with primary pigment – surrounded by accessory
pigment
• Enzymes – ATP synthase – found – membrane of grana
• Fluid substance surrounding grana – called stroma
• Stroma – lipids and starch grains
• Stroma – contains enzymes – involved – calvin cycle
• Carbon di oxide – fixed and starch – made- stroma
• Stroma – 70S ribosome & double stranded circular DNA
• Shape of chloroplast – varies b/w different species

Adaptation of palisade mesophyll cells
for Photosynthesis
• Closely packed – absorbs – more incident light
• Cells – found – near- surface – leaf to maximize light interception
• Cells – arranged – right angles – leaf surface to reduce the number
of light absorbing walls
• Cylinder – shape – produce air spaces b/w cells
• Intercellular air spaces act as reservoir – carbon di oxide
• Provide large surface area for gas exchange
• Cell walls – relatively thin for short diffusion pathway
• Large vacuole pushes – chlorophyll in chloroplast – absorb more
light efficiently
• Large number of chloroplast – maximum light is absorbed
• Chloroplast – also move – within cell – towards light
• Higher light intensity , chloroplast – move away from light – avoid
any damage

Photosynthetic pigments
chlorophyll a – primary pigment in plants and
cyanobacteria (Porphyrin-Mg)
-absorbs violet-blue and red light
chlorophyll b – secondary pigment absorbing light
wavelengths that chlorophyll a does not absorb
accessory pigments: secondary pigments absorbing light
wavelengths other than those absorbed by chlorophyll a
-increase the range of light wavelengths that can be used in
photosynthesis
-include: chlorophyll b, carotenoids, phycobiloproteins
-carotenoids also act as antioxidants

Photo system
• Pigment molecules in chloroplast are
organized into photosystem
A photosystem consists of
1. an antenna complex (light harvesting
complex) of hundreds of accessory
pigment molecules that gather
photons and feeds energy to reaction
center
2. a reaction center of one or more
chlorophyll a molecules pass electrons
out of photosystem (photochemical
reactions)
• There are 2 types of photosystem
• Photosystem I absorption peak 700nm
• Photosystem II absorption peak
680nm

Absorption & Action spectrum
• Absorption spectrum of a pigment is a record of amount of light
absorbed at each wavelength
• Chl a & Chl b absorbs red & blue/violet parts of the spectrum
• Xanthophylls & carotene absorb light from other parts
• This effectively increases the range of wavelength from which plants
can obtain energy

Absorption & Action spectrum
• Action spectrum is a record of amount of photosynthesis
occurring at each wavelength of light
• There is a close similarity b/w the absorption spectra of the
major photosynthetic pigments and the action spectrum
for photosynthesis

Chemistry of photosynthesis
• Photosynthesis consists of 2 stages
• Light reaction/light dependent reaction
• Dark reaction/light independent reaction
• Light reaction- grana
• Dark reaction- stroma

Light reaction
• It consists of light harvesting & electron
transport
• ATP synthesized from ADP + Pi
• NADP is reduced NADPH
• Oxygen is formed from water
• ATP is synthesized by using light energy -
photophosphorylation

Light reaction
• There are 2 different ways in which ATP can be
synthesized by photophosphorylation
• Non cyclic photophosphorylation
• Cyclic Photophosphorylation

Non-cyclic Photophosphorylation
• Non-cyclic photophosphorylation involves both photosystem I and photosystem II
• Light is absorbed by photosystem II and passed on to chlorophyll a
• The irradiated chlorophyll a molecule emits two electrons.
These energized electrons are raised to a higher energy level and are picked by an
electron acceptor.
• The electron acceptor passes the electrons along the chain of electron carriers to
photosystem I.
The energy released from the electrons is used to make ATP from ADP and Pi.
• Light is Absorbed by Photosystem I and Passed on to chlorophyll a.
It emits two electrons.
The energized electrons rise to a high energy level and are picked up by a second
electron acceptor.
Since both chlorophylls have now lost electrons they will both be positive and
unstable.

• The Two electrons released from the chlorophyll a of photosystem II go to
replace the two that have been lost by chlorophyll a of photosystem I.
• Chlorophyll a of photosystem II receives its replacement electrons from the
splitting of water (Photolysis)
• During photolysis the water molecule dissociates into electrons, hydrogen
ions and oxygen.
• Electrons go to photosystem II. The oxygen is released as a waste gas.
• The Hydrogen ions combine with electrons held by the second electron
acceptor to give NADPH.
• This passes to the reaction of the light independent stage.
• So the product of the light-dependent stage are NADPH, ATP and waste
oxygen gas.

Cyclic Photophosphorylation.
• Cyclic Photophosphorylation involves photosystem I only.
• Light is absorbed by photosystem I and passed on to chlorophyll a.
• This causes the chlorophyll a molecule to emit an electron.
• The ‘energised electron is raised to a higher energy level and is picked up
by an electron acceptor
• The electron is passed passed along a chain of electron carriers before it is
returned to the chlorophyll a molecule.
• As the electron passes along the electron carrier chain, enough energy is
released to make ATP from ADP and Pi. This ATP is needed for the light-
independent stage.
• No NADPH is made during the cyclic photophosphorylation.

• The electron transport chains are arranged with
the photosystems in the thylakoid membranes
and pump H+ through that membrane
– The flow of H+ back through the membrane is
harnessed by ATP synthase to make ATP
– In the stroma, the H+ ions combine with NADP+ to
form NADPH
Chemiosmosis powers ATP synthesis in the
light reactions

• The production of ATP by chemiosmosis in
photosynthesis
Thylakoid
compartment
(high H+)
Thylakoid
membrane
Stroma
(low H+)
Light
Antenna
molecules
Light
ELECTRON TRANSPORT
CHAIN
PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

Distinguish between non-cyclic and cyclic
Features Non-cyclic
Cyclic photophosphorylation.
Conditions under which process
occurs.
When plants require ATP and
NADPH
When plants require only ATP.
Pathway of electrons. Non-cyclic Cyclic
For electron donor (source of
electrons)
Water Photosystem I
Last electron acceptor (destination
of electrons)
NADP+ Photosystem I
Establishing proton gradient for the
synthesis of ATP
High hydrogen ion concentration in
the thylakoid space is due to
photolysis of water and active
transport of hydrogen ions from the
stroma, across the thylakoid
membrane, into the thylakoid
space.
High hydrogen ion concentration in
the thylakoid space is due to active
transport of hydrogen ions from the
stroma, across the thylakoid
membrane, into the thylakoid space.
Products ATP,NADPH and oxygen Only ATP.

The light independent stage
This cyclic pathway is sometimes called the calvin cycle.
• Carbon dioxide combines with a five carbon compound,
ribulose biphosphate (RuBP)
• The reaction is catalysed by the enzyme RuBP carboxylase, the
most common enzyme in the world.
• The product is an unstable six carbon compound that breaks
down to form two molecules of three carbon
phospho glycerate (3C )
• ATP is used to phosphorylate the two molecules of Phospho
glycerate to form two molecules of Glycerate biphosphate
of three-carbon

• The next stage involves the use of NADPH to reduce each
molecule of glycerate biphosphate to
Glyceraldehyde 3-phosphate (GALP)
• For every six molecules of GALP formed, five are used in a
series of reactions to regenerate ribulose biphosphate, which
can then combine with more carbon dioxide.
• One of the six GALP molecules is converted to glucose and
other carbohydrates, amino acids and lipids.

Role of NADP in photosynthesis
• NADP – Co Enzymes
• Serves – electron acceptor in the electron transport system during
photo phosphorylation
• Electrons – released – excited chlorophyll in PSI combines with
electron acceptor
• From electron acceptor – pass down – a chain ETC and ends with
NADP
• During photolysis, photons from splitting – water molecules –
reduces NADP – NADPH
• Reduced NADP – passes along – electrons on to the calvin cycle
• During cycle –GP is reduced – 3C sugar called triose phosphate by
reduced NADP
• NADP then reused to light depended stage to pick up another
hydrogen ion

Regulating Stomatal Opening:-the potassium ion pump
hypothesis
Guard cells flaccid
Stoma closed
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
ATP Powered Proton pump actively
transport H+ out of the guard cells
Low H+ concentration and negative
charge inside the cell causes K+
channels to open
K+ diffuses into guard cell down an
electro chemical gradient

Regulating Stomatal Opening:-the potassium ion pump
hypothesis
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
Increased concentration of K+
in guard cells
Lowers the  in the guard
cells
Water moves in by osmosis,
down  gradient
H2O
H2O
H2O
H2O
H2O

Stoma open
Guard cells turgid
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
Increased concentration of K+
in guard cells
Lowers the  in the guard
cells
Water moves in by osmosis,
down  gradient
Entry of water increases the
volume of guard cells
Thin outer wall of guard cell
expands most, so the cells
curve apart.
H2O
H2O
H2O
H2O
H2O
H2O

FACTORS NECESSARY FOR
PHOTOSYNTHESIS
• A number of factors affect the process of
photosynthesis, as a result of which
productivity is affected. These are
• Carbon dioxide
• Water
• Chlorophyll
• Light
• Temperature

Principle of limiting factors
• The Principle of limiting factors also states
that when a biochemical process is affected by
several factors, its rate is limited by that factor
which is nearest its minimum value. That
factor (known as limiting factor) directly
affects the biochemical process if its quantity
is changed.

CARBON DIOXIDE (CO2)
• Air contains 0.03% of CO2. It is released by
respiration, combustion of fossil fuels and
microbial decomposition.
• During early morning hours and evening
hours, CO2 released in respiration is sufficient
for photosynthesis. At this stage, there is no
exchange of gases between the plant and the
environment. This is called compensation
point.

• An increase in the concentration of CO2 upto
0.1% increases the rate of photosynthesis.
• Higher concentration of CO2 decreases the
rate of photosynthesis.

CARBON DIOXIDE
• The rate of photosynthesis increases
with an increase in carbon dioxide
concentration upto a certain level.
• Beyond that, CO2 concentration has
no effect on the rate of
photosynthesis. On the contrary it
decreases the rate.

WATER
• Plants absorb water and mineral salts through root
hair and pass it to the leaves through xylem.
• If there is less availability of H2O, then stomata
closes ( to reduce the water loss by transpiration)
and there is decreased CO2 absorption and sunlight
absorption.
• Therefore the rate of photosynthesis decreases.

CHLOROPHYLL
• Only cells having chlorophyll are
photosynthetic. There is no proportionality
between the rate of photosynthesis and
amount of chlorophyll.

LIGHT
• White light consists of all the seven colours.
Highest rate of photosynthesis is seen in red
light and minimum in green light. Chlorophyll
can absorb violet, blue and red light rays.
• The rate of photosynthesis increases at the
lower intensity of light and decreases in the
stronger intensity of light.

TEMPERATURE
• Photosynthesis is an enzymatic process. The
enzymes function within an optimum range of
temperature.
• Lower temperature has an inhibitory effect on the
rate of photosynthesis because the enzymes are
inactivated.
• Increase in temperature increases the rate of
photosynthesis but it ultimately inhibits
photosynthesis.

Adaptation of leaf to photosynthesis
Upper epidermis
and cuticle is
transparent
Allows most light to
pass to
photosynthetic
mesophyll tissues

Palisade mesophyll
cells are closely
packed and contain
many chloroplasts
To carry out
photosynthesis
more efficiently

Numerous stomata
on lower epidermis
To allow rapid
gaseous exchange
with the
atmosphere

Extensive vein system
• Allow sufficient
water to reach the
cells in the leaf
• To carry food away
from them to other
parts of the plant

Respiration
• Aerobic respiration
• Anaerobic respiration
• Respiratory quotient
• A respirometer

Introduction
• Respiration-Energy releasing process
• Respiration-Oxygen-aerobic respiration
• Respiration-absence of oxygen-anaerobic
respiration
• Glucose-broken down-carbon dioxide, water
and energy
• Energy-ATP
• 1 glucose-38 ATP molecules

• ATP-Adenosine triphosphate
• ADP-Adenosine diphosphate
• AMP-Adenosine mono phosphate
• ATP-formed from –AMP-Adding 2 phosphate
groups
• Removal of terminal phosphate-ATP yields
30.6 kj/mol of free energy
• Hydrolysis of ADP to AMP yields same amount
of energy but the removal of last phosphate
group produce only 13.8 kj/mol

Free energy of hydrolysis of phosphate
compounds
Compounds Free energy change (kj/mol)
1,3-diphosphoglycerate -49.5
ATP(to ADP and Pi) -30.6
ADP(to AMP and Pi) -30.6
AMP(to Adenosine and Pi) -13.8
Glucose 6 phosphate -13.6

- Cylindrical in shape or rod shape
- Width range from 0.5 micro meter to 1.5
micro meter & length from 3 micro meter
to 10 micro meter
- Bounded – double membrane
- Outer & inner membrane - separated by
inter membrane space
- Inner membrane – extensively folded –
from partitions called cristae
- Cristae – projected – into – semi fluid
matrix
- Circular DNA molecule & 70S ribosome –
present
- Endosymbiont theory
Functions of Mitochondria
- Involved – cellular respiration
- Series of bio chemical reaction – result in
formation of ATP
- often known – power station – cell
- More than 1000 mitochondria –found –
metabolically active cell

Cell Respiration can be divided into 4 Parts:
1) Glycolysis
2) Oxidation of Pyruvate
/ Transition Reaction
3) The Krebs Cycle
4) The Electron
Transport Chain and
Chemiosmotic
Phosphorylation

Where do the 4 parts of Cellular Respiration take place?
• Glycolysis:
– Cytosol
• Oxidation of Pyruvate:
– Matrix
• The Krebs Cycled:
– Matrix
• Electron Transport Chain and
Cheimiosmotic
Phosphorylation:
– Cristae

Glycolysis
• Glyco-glucose,lysis-
breakdown
• Involves member of enzyme-
Controlled reaction
• It takes place –cytoplasm of
cell
• It does not require oxygen
• Common for both aerobic
and anaerobic reaction

Glycolysis
• Glucose-phosphorylated by ATP to glucose 6 phosphate
• Phosphorylated glucose – no longer recognized – glucose
transport system , therefore – trapped inside the cell
• Enzyme involved is kinase
• Glucose 6 phosphate-isomerised-fructose 6 phosphate
• Enzyme involved is isomerize
• Fructose 6 phosphate-phosphorylated by ATP to fructose
1,6phosphate
• Enzyme involved is kinase
• Fructose 1,6 phosphate splits to glycerate 3 phosphate
• Glycerate 3 phosphate converts to pyruvate
• Glycerate 3 phosphate when converted to pyruvate it forms 2
NADH2 and ATP

End product of Glycolysis
• 2 molecules of ATP( 4 molecules are produced
but 2ATP are used up)
• 2 molecules of NADH2
• 2 molecule of pyruvate

Oxidation of Pyruvate /Transition Reaction
• Pyruvate- Matrix of
mitochondria from cytoplasm
• Piruvate- Decarboxylated
(Removal of carbon in form of
carbon dioxide)
• Piruvate- Dehydrogenated
(Removal of hydrogen)
• Hydrogen is transferred to
hydrogen acceptor NAD+ to
NADH H
• Pyruvate- Acetate
• Acetate combines with
coenzyme A to form acetyl
coenzyme

• Discovered by sir Hans Kerbs-
1937
• Citric acid cycle /
Tricarboxylic acid cycle (TCA)
• Occurs-Matrix of
mitochondria
• Occurs only in aerobic
reaction

• Acetyl co enzyme A (2C) + oxaloacetate(4C) –citrate
• Reaction is called condensation
• Enzyme involved citrate synthetase
• Citrate isomerizes to isocitrate(6C)
• Isocitrate undergo Oxidative decarboxylation to give α-ketogluterate(5C)
• Carbon dioxide is produced
• NAD+, hydrogen acceptors and NADH is formed
• Enzyme involved is isocitrate dehydrogenase
• X –ketogluterate(5C) undergo oxidative decarboxylation & dehydrogenation gives succinyl
CoA(4C)
• CO2 is produced & NADH is formed.
• Enzyme used is α- ketogluterate dehydrogenase.
• Succinyl CoA(4C) gives succinate
• ATP is formed from ADP+pi
• Enzyme used is succinyl CoA Synthetase
• Succinate undergoes dehydrogenation and gives Fumerate(4C)
• FAD (Flavine adenine dinucleotide) gives hydrogen acceptor and form FADH2
• Enzyme used is succinate dehydrogenase
• Fumerate undergoes hydrogenation and gives maltate(4C)
• Enzyme used is fumerate
• Maltate undergo dehydrogenation and gives oxaloacete (4C)
• (NAD+)+(H+) gives NADH
• Enzyme used is malate dehydrogenase.

The Electron Transport Chain
• Oxygen is required during the
final stage of anaerobic reaction.
• Oxydative phosphorylation is a
process by which ATP is formed
as electron are transferred from
NADH & FADH2 to oxygen via
series of electron carrier.
• Location- inner membrane of the
mitochondria.
• E.T.C involves Chain of electron
carrier molecules.
• Electron from NADH & FADH2
are transferred to Oxygen

• Series of reaction---- Redox reaction
• Hydrogen atom splits to hydrogen ions(H+)
and electrons.
• Transfer of electrons along the chain releases
sufficient energy to make ATP
• Electron and hydrogen ion form hydrogen
atom
• Hydrogen is passed on to oxygen to form
water.

Chemiosmotic Theory
• Energy from Electron transport chain is linked to
pumping hydrogen ion from matrix to space two
membrane
• Result in higher Concentration of hydrogen ions in
inner membrane space and Electro chemical gradient
is setup
• Hydrogen ion pass into matrix through Stalk
granules.
• Electrical potential energy is used to make ATP from
ADP+Pi
• ATP synthetase catalyses the reaction.

• NADH & FADH2 – formed during – glycolysis & Krebs cycle are
passed to ETC
• ETC – present – inner membrane space and consists of cytochromes
• NADH & FADH2 – oxidized – hydrogen are released
• Hydrogen now splits into electrons & protons
• Electrons – pass along – electron carrier and transferred to oxygen
• Protons H+ are actively pumped from – matrix to the outer
compartment i.e. intermembrane space
• A proton gradient – created b/w the outer compartment and the
inner matrix
• Protons cannot diffuse through cristae membrane
• Protons flow only down the gradient – matrix through ATP synthase
channels this is known as chemiosmosis
• Protons flow – ATP synthase channel (F1 channels) they generate
energy to phosphorylate ADP into ATP in the presence of enzyme
ATP Synthase
• Later proton combines with oxygen
• 2E + 2H + ½ O2 – H2O

Summary
• Glycolys- 2 ATP
• Krebs Cycle- 2 ATP (one per turn)
• Glycolysis- 2NADH
• Link reaction- 2NADH
• Krebs cycle- 6NADH (3 per turn)
• Krebs cycle- 2FADH2 (one per turn)
• 1 NADP-3 ATP
• 1FAD-2 ATP

ANAEROBIC RESPIRATION
• In absence of O2 – glycolysis still occurs
• Conversion – pyruvate to acetyl Co A, kerbs cycle
& oxidative phosphorylation – blocked
• Oxidative phosphorylation – blocked becoz O2 –
final electron acceptor – ETC – not available
• Absence – oxidative phosphorylation – no
regeneration of NAD+ & FAD+
• To regenerate NAD+ cells undergo – fermentation
• Two types of fermentation which is most
common
- Lactate fermentation
- Alcoholic fermentation

• Alcoholic fermentation – plants & yeast
• Lactate fermentation – muscles of animal
during strenuous exercise & & in some
bacteria such as Lactobacillus acidophilus
• Both alcoholic & Lactate fermentation don’t
produce ATP Molecules but they regenerate
NAD+ from NADH in order to keep glycolysis
going

Chemistry of Alcoholic Fermentation
• Pyruvate – first decarboxylate to ethanal
• Enzyme – pyruvate decarboxylase
• NADH – reduces Ethanal (2C) to Ethanol (2C) and NAD+
- Regenerated
• Enzyme involved – alcohol dehydrogenase
• Alcoholic fermentation – occurs – plants & Animals
• Plants – respire – anaerobically only for short period of
time during waterlogged condition
• Ethanol – toxic and plant – unable make use of ethanol
• Yeast – ethanol produced – accumulate – medium –
around – cells – concentration rises – level that
prevents further fermentation & kills – yeasts

Respiratory Quotient
• R.Q – ratio of volume of carbon di oxide formed to the volume
of oxygen consumed over a given period of time
• R.Q = CO2 Formed / O2 Consumed
• R.Q – used – provide information abt wht type – substrate – is
being oxidized in respiration
• R.Q – value – more than 1.0 indicates – anaerobic respiration
• R.Q – value for resting animals – b/w 0.8 – 0.9
• R.Q – value for fats – abt 0.7, proteins is 0.9 & carbohydrates is
1.0
• Bcoz – ratio of O2 to carbon – carbohydrates – greater
compared to fats and proteins
• Fats and proteins – need more O2 – complete their oxidation
compared with carbohydrates

Different energy values of carbohydrates,
lipids & proteins as respiratory substrate
• Respiratory substrate are lipids, proteins & Carbohydrates
• Lipids has more energy value that either protein&
carbohydrate
• Lipids have 39.8 Kj/g/unit mass where as protein and
carbohydrates have 17.0 and 15.8 Kj/g/unit mass
• Lipids have more hydrogen atoms in molecule so it has
more energy (hydrocarbon chain)
• The most of energy comes from oxidation of hydrogen to
water using reduced NAD during ETC
• Lipids give more number of reduced NAD which will be
oxidized to give hydrogen
• Hydrogen – splits to proton & electron
• By the process of chemiosmosis the ATP are produced
• Reduced NAD will give 3 molecule of ATP

Difference between photosynthesis and aerobic respiration
Features Photosynthesis Aerobic respiration
Anabolic/catabolic process An anabolic process which results in the
synthesis of carbohydrate molecules from
simple organic substances.
A catabolic process which results in
the breakdown of carbohydrate
molecules to simple inorganic
molecules
Storage of energy Energy is accumulated and stored in
carbohydrate
Energy is incorporated into ATP for
energy requiring process.
Oxygen Oxygen is released Oxygen is used.
Carbon dioxide and water Carbon dioxide and water are used Carbon dioxide and water are
produced.
Change in dry mass Process results in an increase in dry mass. Process results in a decrease in dry
mass.
Organelle involved Process occurs in the chloroplast. Majority of the reactions in the
process occurs in the mitochondrion.
Occurance Process occurs only in cells processing
chlorophyll and only in the presence of light.
Process occurs in all cells and
continuously throughout the lifetime of
cells.

Difference between photophosphorylation and oxidative
phosphorylation.
Features Photophosphorylation Oxidative phosphorylation
Location Thylakoid membrane of chloroplast. Inner membrane of mitochondrion.
Involvement of light enery. Light energy is required for splitting
water.
Light energy is not required.
Source of energy for synthesis of
ATP.
Energy for synthesis of ATP comes
directly from light.
Energy for synthesis of ATP comes
from the oxidation of glucose.
Electron donors. Water is the electron donor in the
non-cyclic pathway while
photosystem I is the electron
acceptor in the cyclic pathway.
NADH and FADH2.
Electron acceptors. NADP+ is the final electron acceptor
in the non-cyclic pathway while
photosystem I is the electron
acceptor in the cyclic pathway.
Oxygen is the final electron
acceptor and is reduced to water.
Establishing proton gradient for the
synthesis of ATP.
Protons are pumped inwards, from
stroma across the Thylakoid
membrane into the Thylakoid space.
Protons are pumped outwards, from
matrix, across the inner membrane,
into the intermembrane space.

Unit 6 energy, respiration and photosynthesis A Level

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Unit 6 energy, respiration and photosynthesis A Level