The lightdependent reaction The lightindependent reaction Required practical 7 Use of chromatography to investigate the pigments isolated from leaves of different plants eg leaves from shadetolerant and shadeintolerant plants or leaves of different colours ID: 750188
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Slide1
Photosynthesis
Content:
Overview of photosynthesis
The light-dependent reaction
The light-independent reaction
Required practical 7:
Use of chromatography to investigate the pigments isolated from leaves of different plants,
eg
, leaves from shade-tolerant and shade-intolerant plants or leaves of different colours.
Required practical 8
:
Investigation
into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.Slide2
Overview of photosynthesis
Explain how the plant leaf is adapted to carry out photosynthesis.
Describe the main stages of photosynthesis.
Describe the structure of chloroplastOutline the role chloroplast plays in photosynthesis.
KEYWORDS: ATP, cuticle, chloroplast, chlorophyll, mesophyll, stoma, stroma, grana, thylakoid
Synoptic links: 2.3 Energy & ATP + 3.4 Eukaryotic cell structureSlide3
WORDS
Stoma
Pore in the leaf to allow gas exchange to occur.
Stroma
Fluid filled area within a chloroplast where the light independent stage of photosynthesis takes place.Slide4
What is photosynthesis?
All life on Earth depends on
photosynthesis
. The process is described by the following word and symbol equations:
These equations are summaries of a complex two-step process that takes place in the
chloroplasts
of green plants. The end products are not just glucose, but complex organic molecules such as carbohydrates, amino acids, lipids and nucleic acids.
carbon
dioxide
+ water
oxygen + glucose
light energy
6CO
2
+ 6H
2
O
6O
2
+ C
6
H
12
O
6
light energySlide5
Why do plants photosynthesize?
Photosynthesis is an essential biological process. This is because it produces:
energy for processes in the organism
complex organic molecules needed for growth
oxygen, which is then used for respiration.
The oxygen produced is released into the atmosphere and is available for other organisms.
If the plant is eaten, the organic molecules are used to provide energy to organisms higher up the food chain.
There are not just advantages for the plant itself:Slide6
Leaves and photosynthesisSlide7
Adaptations of the leaf
Adaptation
How they aid photosynthesis
Large surface area
Absorb
as much light energy as possible.
Arrangement of leaves
Minimise
overlapping & avoids shadowing.ThinMost light absorbed in first few micrometres. Short diffusion pathway
Transparent cuticle & epidermis Maximise light penetrating to mesophyll.Slide8
Adaptation
How they aid photosynthesis
Long narrow mesophyll cells packed with chloroplast
Absorb
as much light energy as possible.Lots of stomata
Maximise gas exchange
& short diffusion pathway.
Guard cells
Controls opening & closing of stomata depending upon light intensity.Many air spacesRapid diffusionNetwork of xylem & phloem
Supplies leaf with water & carries sugars away.Slide9
Structure of the chloroplastSlide10
Plant photosynthetic tissuesSlide11
Plant anatomySlide12
Functions of photosynthetic structuresSlide13
Photosynthetic PigmentsSlide14
Photosynthetic pigmentsSlide15
The light dependent reaction
Explain the process of oxidation and reduction.
Explain how ATP is made during the light dependent reaction.
Describe the role of photolysis.Explain how chloroplasts are adapted to carry out the light dependent reaction.
KEYWORDS: ATP, photolysis, reduction, oxidation, photoionisation
, thylakoids, electron carrier,
chemiosmotic
theory, NADP, NADPHSlide16
Oxidation & reduction – always together
Oxidation (oxidised)
Addition of oxygen
Loss of electrons,
Loss of hydrogenEnergy given outReduction (reduced)Loss of oxygenGains electrons
Gains hydrogen
Energy taken inSlide17
The light dependent stage of photosynthesis
Water is split by light to produce oxygen.
This is
PHOTOLYSIS
.
Water OxygenSlide18
Animation
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120072/bio13.swf::
Photosynthetic%20Electron%20Transport%20and%20ATP%20SynthesisSlide19
Cyclic and non-cyclic photophosphorylation
http://
highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter39/cyclic_and_noncyclic_photophosphorylation.htmlSlide20
WORDS
Photophosphorylation
Use of light energy to combining ADP and inorganic phosphate into ATP.
Non - cyclic photophosphorylation
Series of reactions involving the production of NADPH. The electron is used up in the process.
Chemiosmosis
Creation of ATP from ADP and inorganic phosphate by moving hydrogen ions through the ATP-synthase down the concentration gradient.
Cyclic photophosphorylation
The excited electron passes its energy to the proton pump causing chemiosmosis to occur. The electron is cycled.Slide21Slide22
Describe the light dependent stage of photosynthesis
Cyclic phosphorylation
Electron transport chain
Electrons
NADP Reduced NADP
ATP synthase
chemiosmosisSlide23
The light independent reaction
Explain how carbon dioxide is incorporated into organic molecules.
Describe the role of ATP & NADPH in the light independent reactions.
Describe the events in the Calvin cycle.
KEYWORDS: ATP, NADP, NADPH, Calvin cycle, stroma, stoma, RuBP, rubisco, GP, TP, organic compoundSlide24
ChloroplastSlide25
Animation
http://
highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.htmlSlide26
GP
T
P
T
PSlide27
Making complex molecules
Pairs of TP molecules combine to form hexose sugars, such as
glucose
, some of which may isomerize to form
fructose
.
Triose phosphate
is a three-carbon sugar that can be used to make a variety of complex biological molecules.
TP can be converted to
glycerol and this may be combined with fatty acids to make
lipids.These monosaccharides can combine to form disaccharides such as sucrose, and polysaccharides such as cellulose and starch.Slide28
Describe the light
independent
stage of photosynthesis
Reduced NADP
ATPRibulose
bisphosphate
carboxylase/
oxygenase
(Rubisco)Glycerate-3-phosphate (GP)Triose phosphate (TP)Ribulose bisphosphate
(RuBP)Hexose sugars (glucose)GlycerolFatty acidsAmino acidsLipidsSlide29
Summary of photosynthesis
light- dependent reactions
light- independent reactions
light
carbohydrates, other complex moleculesSlide30
Calvin cycle song
https://
www.youtube.com/watch?v=OYSD1jOD1dQSlide31
Investigating rate of photosynthesis
Outline how you can investigate photosynthesis qualitatively.
Outline how you can investigate photosynthesis
quantitatively.Complete both safely.
KEYWORDS: limiting factor, rate of reaction, light intensity, Slide32
What are limiting factors?
The
law of limiting factors
states that:
Factors that can limit the rate of photosynthesis include:
At any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value.
This factor is called a
limiting factor
because it limits the rate at which the process can take place. Changing the levels of other factors will not alter the rate of the process.
CO
2
concentration.
temperature
light intensitySlide33
What will affect the rate of reaction?
What reactants are needed?
Where do reactants come from?
What affects enzyme efficiency?Where do the products go?Slide34
Are we really measuring photosynthesis?
Oxygen is produced in the light-dependent stage of photosynthesis. However, at all light intensities, plants
respire
. Respiration uses oxygen.
In other words, the amount of oxygen produced by the plant is excess to that which the plant uses for respiration.
When the rate of photosynthesis is determined by measuring the amount of oxygen formed, what is actually being measured is the
net release of oxygen
, which represents how much the rate of photosynthesis exceeds the rate of respiration.
Respiration
: C
6H12O6 + 6O2 ® 6H2
O + 6CO
2Slide35
Qualitative
Counting the bubbles on Elodea/
Cabomba
. Slide36
Quantitative
Colour change of hydrogen carbonate due to pH change.Slide37
Effect of light intensitySlide38
Plotting light intensity
Volume of oxygen can be plotted against
light intensity
instead of distance. This can be measured with a lightmeter as the lamp is moved closer. A graph like this one is obtained:
What relationship does this graph show between light intensity and oxygen and why could this be? What does this mean in terms of limiting factors?
volume of oxygen produced in 5 mins (mm
3
)
light intensity (lux)Slide39
Comparing different types of plant
The graph shows the growth of two types of crop at varying light intensities.
light intensity
(arbitrary units)
rate of photosynthesis
(arbitrary units)
crop B
crop A
How is the growth of the two crops similar?
From this data, suggest which crop would be better suited to grow in a sunny climate, which in a cloudy climate and why.
What other issues might these climates create?Slide40
Why is temperature important?
The
light-independent reaction
of photosynthesis is controlled by
enzymes
. Temperature affects enzyme reactions.
As temperature increases, collision frequency between reactant particles and between reactant and enzyme increases. This increases the rate of reaction up to the optimum temperature.
Beyond the optimum temperature however, enzymes begin to be
denatured
. Their tertiary structure breaks down, changing the shape of the active site so that reactant molecules no longer fit.
up to optimum temperature
enzyme denatured at high temperatureSlide41
Effect of temperatureSlide42
Atmospheric carbon dioxide
Carbon dioxide
is essential for the photosynthesis process. It is used during the
light-independent
stage to carboxylate
ribulose bisphosphate
.
The normal concentration for atmospheric carbon dioxide varies between 0.03
% and 0.04 %.Plants are adapted to survive in varying concentrations of CO2, but the higher the value, the higher the rate of photosynthesis.
Plants may therefore be able to remove some of the CO2 released by human activity from the air.Slide43
Effect of carbon dioxide concentration