BTEC Level 3 National Extended Diploma in Applied
Science
Unit 10:
photosynthesis
Learning Aim C:
Explore the effect of activity on respiration in humans and
factors that can affect respiratory pathways
Assignment Title:
Photosynthesis in plants
,Pathways in photosynthesis:........................................................................................................................3
Photosynthesis:............................................................................................................................................3
Chlorophyll...................................................................................................................................................4
Light dependent reaction for photosynthesis..............................................................................................4
Cyclic phosphorylation.................................................................................................................................5
Non-cyclic phosphorylation..........................................................................................................................5
Calvin cycle light independent- Calvin Cycle................................................................................................7
Carbon fixation........................................................................................................................................7
Reduction of glycerate.............................................................................................................................8
Factors that affect the rate of photosynthesis:............................................................................................8
Investigating the effect of temperature on the rate of photosynthesis:.......................................................9
Risk assessment.........................................................................................................................................10
Equipment list............................................................................................................................................10
Method......................................................................................................................................................11
Results table of the practical I did.............................................................................................................15
Secondary results: light intensity, temperature, carbon dioxide concentration.........................................16
Conclusion..................................................................................................................................................19
Evaluation..................................................................................................................................................21
,Pathways in photosynthesis:
The process through which sunlight's light energy is converted into chemical energy and used to
create big organic molecules from inorganic materials is known as photosynthesis. Additionally,
oxygen may be released into the atmosphere. To survive, we are all dependent on
photosynthesis. We consume both plants and their products. We breathe in oxygen because
plants produce it when they are consumed by animals, which is then used by us to breathe.
Photosynthesis:
The process of photosynthesis converts light energy into chemical energy. Glucose and
oxygen are produced as a result of plant reactions with water and carbon dioxide. Because it
produces the oxygen and glucose needed for all living things to grow and breathe, it is
significant.
Photosynthesis is an endothermic reaction since energy has been expended during the
process. In chloroplasts, photosynthesis occurs. Chloroplasts come in a variety of sizes and
shapes; for instance, they can range in length from 2 to 10 micrometer's, are encircled by a
bilayer membrane, and include stacks of sacs called thylakoids that contain the chlorophyll
pigment.
Chlorophyll, a plant pigment that absorbs light energy and gives leaves their green color, is
found in the thylakoids. This is done using photosystems. In photosynthesis, there are two
primary phases. A light-dependent reaction occurs in the first step, but a light-independent
reaction occurs in the second. The production of molecules occurs during photosynthesis,
which is an anabolic reaction. The balanced equation is 6CO2 + 6H2O -> C6H12O6 + 6O2, while
the word equation for photosynthesis is Carbon Dioxide + Water -> Glucose + Oxygen.
,Chlorophyll:
Chlorophyll is a green pigment found in plants, but it is made up of a variety of pigments. All of
the pigments have long phytol (hydrocarbon) chains and a porphyrin group that contains
magnesium. Chlorophyll works in combination with the metal magnesium. Chlorophyll A and
chlorophyll B are similar molecules that absorb light in the red and blue regions of the
spectrum. They are made up of a head that absorbs light and a tail that anchors it to the
thylakoid membrane. The head is a complex chemical ring structure with a magnesium ion in
the center. Chlorophyll a is made up of two primary pigments: P680 and P700, which appear
yellow/green but absorb red light at slightly different wavelengths. They are found in the
primary pigment reaction center, which is the photosystem's nerve center. Photosystems are
the functional components of photosynthesis. They are distinguished by a distinct pigment
arrangement and oversee absorbing and transferring light energy, which includes electron
transfer. In other words, they are unique combinations of photosynthetic pigments
(substances that absorb certain wavelengths of light while reflecting others). P680 is found in
photosystem II and absorbs red light at a wavelength of 680nm. P700 is found in a different
type of photosystem known as photosystem I and absorbs red light. At a wavelength of
700nm.
Light dependent reaction for photosynthesis:
Even though photosynthesis is light-dependent, the next stage requires two molecules: the
reduced electron transporter NADPH and the energy storage molecule ATP (Adenosine
triphosphate). It happens in chloroplast thylakoid membranes. Photolysis and
,photophosphorylation are the two main processes involved in the light dependent reaction of
photosynthesis.
When there is light, water splits, which is known as photolysis. During this process:
• The light energy breaks down water in the thylakoid lumen to produce hydrogen
ions, electrons, and oxygen.
• An enzyme in photosystem II can break down water into protons (H+) ions,
electrons, and oxygen when exposed to light.
• A proton gradient is formed as a result of water photolysis, which results in a
high concentration of hydrogen ions in the thylakoid lumen.
Photophosphorylation is a process that produces ATP (adenosine triphosphate). It occurs by
using the proton gradient formed by photolysis between the thylakoid lumen and stroma to
drive the enzyme ATP synthase. ADP (adenosine diphosphate) + Pi -> ATP is the symbol
equation for photophosphorylation. Photophosphorylation is classified into two types: cyclic and
non- cyclic. Only photosystem II is involved in cyclic photophosphorylation. Non-cyclic
photophosphorylation, on the other hand, involves both photosystems I and II. A primary
pigment is a collection of photosynthetic pigments found in each photosystem that absorbs light
energy and transfers it to electrons. Photosystem II is located at the beginning of the electron
transport chain and is responsible for water photolysis. During the light independent reaction of
photosynthesis, the energy of ATP is carried.
Cyclic phosphorylation:
It only affects photosystem I. (PSI).
• Photosystem I absorb light and transmit it to the system's primary pigment (P700).
• Photoactivation occurs when an electron in the chlorophyll molecule, the primary
pigment molecule, is stimulated to a higher energy level and then released from
the chlorophyll molecule.
• This excited electron is captured by an electron acceptor and transported by an
electron transport chain before being returned to the chlorophyll molecule in
photosystem I.
• Proton pumps use the energy provided by electrons as they move through the
electron transport chain to move protons (H+) from the stroma of the thylakoid
lumen.
• The chemiosmosis process drives the synthesis of ATP from ADP and an
inorganic phosphate group (Pi).
, • The transport of protons or chemicals along a concentration gradient is known as
chemiosmosis. The energy released by this process can be used by ATP synthase
to produce ATP.
• ATP is then transferred to the light independent reaction.
Non-cyclic phosphorylation:
Involves both photosystems
Photosystem I:
• In a photosystem, electrons Photoactivation occurs concurrently with electrons in
photosystem II.
• Electrons in the charged photosystem in addition, an electron transport chain is
passed along.
• These electrons react with the carrier molecule NADP, hydrogen ions (produced by
water photolysis), and these electrons form reduced NADPH.
• 2H+ + 2e- + NADP -> reduced NADPH
• The reduced NADPH was then passed to the light-independent reaction, where it was used
in the carbohydrate synthesis.
• The oxygen-evolving complex, a component of photosystem II, is an enzyme that aids
in the photolysis (or splitting) of water.
• As the excited electrons leave the primary pigment of photosystem II and move on
to photosystem I, electrons from water photolysis replace them.
Photosystem II
• Electrons in the photosystem Photoactivation occurs simultaneously with electrons in
photosystem II.
• The electrons in the charged photosystem A chain of electron transport is also
passed along.
, • These electrons combine with the carrier molecule NADP, hydrogen ions (produced
by water photolysis), and these electrons to form reduced NADPH.
• The symbol equation is 2H+ + 2e- + NADP -> reduced NADPH.
• The reduced NADPH is then passed to the light-independent reaction to be used
in carbohydrate synthesis.
Calvin cycle light independent- Calvin Cycle:
Energy is transferred from the light-dependent stage to the light-independent stage via ATP and
hydrogen from reduced NADAP. The Calvin Cycle describes the light-independent reactions of
photosynthesis. It occurs in the chloroplast stroma. The products of the light dependent stage
are used to produce complex organic molecules such as starch (for storage), sucrose (for
translocation around the plant), and cellulose (for making cell walls).
Carbon fixation:
• Ribulose bisphosphate, a five-carbon (5C) sugar, reacts with carbon dioxide (RUBP).
• The rubisco enzyme oversees catalyzing this reaction (ribulose
bisphosphate carboxylase).
• The resulting six-carbon compound (6C) is unstable and splits in two.
, • This results in two molecules of glycerate 3-phosphate, a three-carbon (3C)
compound (GP).
• The carbon dioxide issue has been "solved" (it has been removed from the
external environment and has become part of the plant cell).
• Glycerate 3-phosphate (GP) is not a carbohydrate, but it is converted to one in the
next step of the Calvin cycle.
Reduction of glycerate:
• The energy from ATP and hydrogen from reduced NADP are used to convert glycerate
3- phosphate (GP) to triose phosphate, a phosphorylated three-carbon (3C) sugar (TP).
• One-sixth of the triose phosphate (TP) molecules are converted into useful
organic molecules required by the plant.
• Condensing triose phosphate yields hexose phosphate (6C), which can be used
to produce starch, sucrose, or cellulose.
• Triose phosphate can be converted to glycerol, and glycerate 3-phosphates can be
converted to fatty acids, which can then be combined to form lipids for cell
membranes.
• Triose phosphates can be used to produce the amino acids required for
protein synthesis.
,Factors that affect the rate of photosynthesis:
Any factors in an environment capable of slowing down the rate of a chemical reaction are
referred to as limiting factors. Photosynthesis is limited by five major factors: light intensity,
carbon dioxide concentration, water levels, light wavelength, and temperature (universal
limiting factor for all chemical reactions). Because photosynthesis rate is inversely proportional
to light intensity, light intensity can influence photosynthesis rate. The rate of photosynthesis
varies with the amount of light available during the day. When exposed to light, the stomata
open, allowing carbon dioxide to enter through the leaves. Because carbon dioxide is required
in the light-independent reaction (LIR), increasing CO2 concentration affects the rate of
photosynthesis. Water is required for photosynthesis to occur; however, a plant will wilt
before a lack of water affects photosynthesis rate. Water also keeps humidity high, allowing
the grower to optimize mineral ions. Because pigments can only absorb certain wavelengths of
light, the wavelength of the light will influence the rate of photosynthesis. When these
wavelengths become available, for example, the rate of photosynthesis will either increase or
decrease.
Temperature has little impact on light-dependent reactions.
A limiting factor is something that can cause a chemical reaction or process to take longer.
, Investigating the effect of temperature on the rate of
photosynthesis:
The time it takes for a product to be formed or a molecule to be broken down can be used to
calculate the rate of reaction. I calculated the rate of temperature by measuring the time it
takes to produce oxygen.
Aim: the effect of temperature on the rate of photosynthesis.
Hypothesis: as temperature increases the rate of photosynthesis will decrease. This is because
the Calvin cycle enzymes work best at temperatures ranging from 0 to 25 degrees Celsius, the
rate of photosynthesis doubles every 10 degrees Celsius. When the temperature rises above 25
degrees Celsius, the rate of photosynthesis begins to slow because the enzymes become
denatured and stop working as efficiently.
Independent variable: temperature
Dependent variable: rate of
photosynthesis
Control variable: time, CO2 concentration, type of plant, the length of the plant, water level.
Risk assessment:
Hazards Risks precautions
