BIO - photosynthesis

outline the stages of photosynthesis

oxidation vs reduction

oxidation - gains O2 loses H+

reduction - gains O2 loses H+

what is a co enzyme

co enzymes will assist specific enzymes by catalysing, or transferring chemical groups.

which coenzyme is used in photosynthesis

NADP - transfers H+ form one molecule to another so oxidises.

what is the grana

stack of thykaloids

site of light dependent reactions =

FINISH FC BEFORE

the eq for photosynthesis

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

what is NADPH

reduced NADP

what are the two photosystems

PSI - light at wavelength 700 nm

PSII - light at wavelength 680 nm

what is a photosystem

A photosystem is a complex of proteins and pigments within the thylakoid membrane of chloroplasts that captures light energy and converts it into chemical energy during photosynthesis.

what are the products of the light dependant reaction

02

NADPH

ATP

What is photoionisation

The process by which light energy is absorbed by chlorophyll, causing electrons to become excited and be released, initiating the light-dependent reactions of photosynthesis.

what is photoionisation used for

1. to make ATP from ADP - photophosphorylation

2. form reduced NADP from NADP

3. splitting water into protons (H+), electrons and oxygen - photolysis

process 1 of LDR

photoionisation

light energy is absorbed by 2 (PSII) in the thylakoid membrane. this excites the electrons.

(electrons are lost from the chlorophyll meaning chlorophyll is ionised)

step two of LDR

electrons are transferred along a electron transport chain to PSI. - at each stage e is lost.

some of the e lost is used to fuel the pump moving H+ ions into the thylakoid

what are the steps in the process of photolysis of water

2H₂ O → 4H+ + 4e- + O2

4H - reduces NADP + increases the conc. grad between thykaloid and stroma

4e- - replaces those lost by the chlorophyll

02 - by product, diffuses out of leaf or used in respiration

step three of LDR

as H+ is moved into the thykaloid from the stroma the H conc. in the thylakoid increases

so the protons move back into the stroma down the conc. grad via the enzyme ATP Synthase - found in thylakoid

e from this process allows ADP and inorganic phosphate to combine and form ATP. - into the stroma

this ATP feeds into the LIR

Step 4 of LDR

light energy absorbed by PSI excites the electrons to a higher level

they are passed down the electron transfer chain

eventually, electrons are transfered to NADP as well as H+ from the stroma to form NADP

what is the first stage of the LIR

CARBON FIXATION

ribulose bisphosphate (RuBP) is a five-carbon sugar

this undergoes carbon fixation by the enzyme RuBisCo

to form 3-phosphoglycerate (3-PGA).

what is the second stage of the LIR

REDUCTION

where 3-phosphoglycerate (3-PGA) is converted into

triose phosphate (TP)

using ATP and NADPH produced in the LDR.

what is the three stage of the LIR

REGENERATION
where TP is used to regenerate RuBP, allowing the cycle to continue.

what is the Calvin cycle

calvin cycle steps over view

1. CO2 diffuses into the leaf through the stomata and dissolves in the water around the mesophyll cells

   then diffuses through the plasma membrane, chloroplast membrane, and into the stroma

2. carbon fixation; reduction - CO2 binds to the 5 carbon compound glycerate-3-phosphate - reaction is catalysed by rubisco to form 2 GP

3. GP is reduced and activated to form TP - ATP and reduced NADP from the LDR provide the e for this step

   the ADP and Pi and NADP return to the thylakoid membrane for recycling

4. most of the TP continues to regenerate the RuBP and complete the cycle. requires ATP. NADP is reformed and goes back into t6he LDR.

clavin cycle

what are the limiting factors of photosynthesis

• light intensity

• temperature

• CO2 conc.

what is the limiting factor

the factor in shortest supply

what is the compensation point

the light intensity at which the rate of photosynthesis equals the rate of respiration in a plant.

in what conditions will plants reach the compensation point

Plants will reach the compensation point in low light conditions where light intensity is insufficient for photosynthesis to exceed respiration rates.

how to calculate the compensation point

measure the O2 production and consumption (photosynthesis and respiration) and where they are equal is the CP

how would you represent the compensation point on a graph

why is temperature a limiting factor to photosynthesis

rubisco and ATP synthase will denature above 45 and be inactive below 10

and stomata will close to conserve water - high temp

why is water a limiting factor to photosynthesis

too little - supply stops

too much - soil becomes waterlogged ( has less O2 so less ATP and less minerals)

who investigated photosynthesis in the lollipop experiment

Melvin Calvin

outline the procedure of the lollipop experiment

placing aquatic plants, such as chlorella, in a lollipop-shaped glass apparatus filled with a solution containing radioactive carbon dioxide.

The plant was illuminated, allowing it to photosynthesize, and then samples were taken at various time intervals to track the incorporation of carbon into organic compounds.

outline the findings of the lollipop experiment

The experiment demonstrated that carbon dioxide is incorporated into carbohydrate molecules during photosynthesis.