M5 CH17 Energy for Biological Processes Flashcards
What are the two stages of photosynthesis?
The two stages of photosynthesis are:
-The light-independant reaction
-The light-dependant reaction
What is the light-dependant reaction in photosynthesis?
The light-dependant reaction in photosynthesis:
-Occur within the thykaloid membranes in chloroplasts
-Requires light as it produced ATP + NADP
What is the light-independant reaction in photosynthesis?
The light-independant reaction in photosynthesis
-Uses the products from the light-dependant reaction
-Occurs within the stroma - fast diffusion from thykaloid to stroma
-Involves the Calvin Cycle
What are autotrophs?
Autotrophs are oganisms that synthesis complex organic molecules from simple inorganic ones
Chemoautotrophs, Photoautotrophs, Heterotrophs
Chemoautotrophs - uses chemical energy (nitrifying bactera)
Photoautotrophs - uses light energy (plants, algae)
Heterotrophs = doesn’t make own food (humans)
What is the endosymbiant theory?
Endosymbiant theory = cells have developed from prokaryotes
What is photolysis?
Photolysis = enzyme-catalysed reaction -> water molecules split using light energy
What is phosphorylation?
Phosphorylation = formation of ATP
What is NADP?
NADP = co-enzyme that reduces GP molecules within the calvin cycle
What is chemiosmosis?
Chemiosmosis = flow of H ions through ATP synthase = the force of the flow produced ATP
What are co-enzymes?
Co-enzymes carries out oxidation/reduction, carrying molecules between reactions
What are the steps involved in non-cyclic phosphorylation (LIR)
Non-cyclic phosphorylation:
Light energy is absorbed by the pigments in PSII, exciting electrons. These electrons are then passed through an electron transport chain (ETC) to PSI, releasing energy that is used to generate a proton gradient across the thylakoid membrane.
Water molecules are split by PSII, releasing electrons, protons (H+), and oxygen gas. The electrons from water replace the electrons lost by PSII and are passed through the ETC to PSI.
The high-energy electrons from PSI are used to reduce NADP+ to NADPH, which is used as a reducing agent in the light-independent reactions of photosynthesis.
The proton gradient generated by the ETC is used by ATP synthase to generate ATP from ADP and inorganic phosphate.
What is non-cyclic phosphorylation
Non-cyclic phosphorylation is the process of generating ATP through the transfer of electrons from NADH and FADH2 to oxygen in the mitochondria. This process also generates a proton gradient which drives ATP production.
Why is non-cyclic phosphorylation known as non-cyclic?
It is non-cyclic because electrons that return to the chlorphyll molecules are not the same as the electrons that left the chlorophyll
What is cyclic phosphorylation?
Cyclic phosphorylation happens when NADP produced fits the needs of the plant, and so the light energy can be used elsewhere
-Only makes ATP
-Only happens using PS1
-Electrons return to original position rather than being given to NADP
Outline the process of the Calvin Cycle (light-dependant stage of photosynthesis)
CO2 (1carbon) -> Rubisco (enzyme) -> 2x GP (6carbon) -> ATP used and phosphorylised, reduced NADP oxidised -> 2xTP (6 carbons) -> 1 carbon given off to produce 1 glucose -> ATP added and RuBP used up (5 carbons) -> returns to rubisco
What is the calvin cycle?
The Calvin Cycle:
-Is the light-dependant stage of photosynthesis
-Occurs in the chloroplast stroma
-Repeats 6 times to make 1 molecule of glucose
-5 out of 6 molecules of TP used to regenerate RuBP -> the leftover carbon makes hexose sugar (glucose)
Outline the role of carbon dioxide in photosynthesis
Role of carbon dioxide in photosynthesis:
-Source of cabron
-Once fixed, used to build more complex molecules
-All molecules are organic/carbon based -> eg glucose + amino acids -> proteins
Why are there only small amounts of RuBP in the stroma of chloroplasts?
There are only small amounts of RuBP because it is being continuously regenerated in the cycle
Why does the chloroplast fluid contain enzymes?
Chloroplast fluid contain enzymes for metabolic reactions such as calvin cycle -> ie rubisco
Why does the stroma fluid surround the grana of chloroplasts?
Stroma fluid surrounding grana means products from the LIR are quickly passed onto the LDR for the calvin cycle/photosynthesis
Identifying the thykaloids in a microscopic image
Thykaloids appear as black bands under microscopes
What are found between thykaloids?
Integranal lamallae are found between thykaloids
Photosynthetic pigments
Photosynthetic pigments are found in thykaloid membranes, and absorb certain wavelengths of light, reflecting others (green)
Which ion is found within chlorophyll?
A magnesium ion is found wtihin the centre of chloroplast
What is the primary pigment of chloroplasts?
Primary pigment = chlorphyll a -> as it has mg -> two types: P680 and P700
What are the acessory pigments and their colours within chloroplasts?
Acessory pigments in chloroplasts:
-Chlorophyll b -> bluey-green
-Carotene -> orange
-Xanthophyll -> yellow
What is the light harvesting system in chloroplasts
Light harvesting system:
-Aborbs/harvests light of energy of different wavelengths and transfer this energy to the reaction centre, where chlorophyll a is located and where mg electrons become exited
What are photosystems?
Photosystems are clusters where photosynthesis pigments are found
Where is P680 of chlorophyll a located?
P680 of chlorophyll a is located in photosystems 2 - peak absorption is 680nm
Where is P700 of chlorophyll a located?
P700 of chlorophyll a is located in photosystem 1 -> peak absorption is 700nm`
Chloroplast adaptations
Chloroplast adaptations:
-Inner membrane contains transporter proteins
-Lots of grana -> more pigments
-Proteins embdedded in grana -> holds photosystems in place
-Enzymes within stroma
-Grana surrounds strama for ease of product acess between stages
-DNA and ribosomes for proteins
How to calculate rf value?
Rf value = (distance moved by solute) / (distance moved by solvent)
What is the photolysis of water in the LDR in photosynthesis?
The photolysis of water - light energy causes a water molecule to split apart and release hydrogen ions, electrons and oxygen. The electrons from water replace the electrons lost from PSII. As the electrons move along the electron transport chain, they move from high to low energy
What are the limiting factors of photosynthesis?
Limiting factors of photosynthesis:
-Temperature (enzyme-controlled LIR affected)
-Light intensity (LDR-> photolysis needs light to occur, blue and red light must be in balance, GP accumulates due to reduced ATP and NADH, leading to low TP and RuBP)
-Carbon dioxide
-Water
Why is light intensity a limiting factor of photosythesis?
Light intensity - limiting factor of photosynthesis - LDR-> photolysis needs light to occur, blue and red light must be in balance, GP accumulates due to reduced ATP and NADH, leading to low TP and RuBP
Why is measuring O2 only an approximate prediction of photosynthetic rate/why is it not entirely accurate?
O2 is a waste product of photosynthesis and so is used as an approximate prediction. However, O2 could be used in respirational processes as well as O2 only being present in the LDR due to the photolysis of water.
