Mr G bio 1 Photosynthesis Flashcards
what is the structure of ATP?
nitrogenous base and three phosphate groups
how is ATP formed?
ADP and an inorganic phosphate and requires energy to add a phosphate group to ADP to form ATP creating a high energy bind which involves a condensation reaction involving ATP synthase
How is ATP broken down back into ADP and an inorganic phosphate?
Via hydrolysis reaction involving ATP hydrolase
what happens when ATP is hydrolysed
the bond between the second and third phosphate breaks releasing small amount of usable energy
why is the Pi released during the hydrolysis of ATP useful?
it can be used to phosphorylate other molecules, which can make them more reactive
what are the uses of ATP?
active transport, muscle contraction and protein synthesis
why is ATP useful?
-energy is released in small amount
-ATP is soluble
-involves a single reaction
what is NADP?
NADP is a molecule which acts as a hydrogen acceptor. Gains hydrogen and becomes reduces to NADPH
what does NADPH provide?
reducing power within reactions as it loses this hydrogen, becomes re-oxidised to NADP
what is photosynthesis?
a process in which plants absorb light energy and convert it into chemical potential energy. simple inorganic molecules are converted into organic moelecules
where does photosynthesis occur?
chloroplasts
how are chloroplasts adapted for their function?
contain a pigment called chlorophyll which can absorb different wavelengths of light. this helps plants to adapt to the light levels of their environment
where does the light dependent reaction take place?
across the thylakoid membrane
what are the 2 parts of the light dependent reaction?
photosystem two and photosystem one
what does each part of the light dependent reaction make?
1st (photosystem two) makes ATP and 2nd (photosystem one) makes NADPH (reduced hydrogen carrier)
what is photoionisation?
the process by which a chlorphyll molecule becomes positively charged as a result of losing 2 electrons when it absorbs light
give a summary of the process of the light dependent reaction up to phtotionisation (1)
-light energy hits chlorophyll molecules
-electrons in chlorophyll gain energy and raised to higher energy level (due to photoionisation)
during the light dependent reaction, what do the electrons do after photoionisation? (2)
-pass along a number of electron carriers in the thylakoid membrane in a series of redox reactions
what happens to the electrons during the diff stages of the ETC? (3)
they lose energy at each stage which is used to form ATP from ADP and Pi
what is the ATP formed from the energy lost from electrons used for? (4)
used in the light independent reaction and used to actively transport H+ into the thylakoid through a protein carrier
what happens as a result of the H+ being actively transported into thylakoid? (5)
now a high conc of H+ in thylakoid and the H+ ions diffuse via chemiosmosis back into the stroma via the enzyme ATP synthase, producing ATP from ADP and Pi
what occurs in photosystem 1 that results in the formation of reduced NADP? (6)
light energy excites energy level of electrons in next chlorophyll and electrons pass down the electron transfer chain as before and this time at the end of the transport chain, 2 electrons join with 3 H ions and NADP to form reduced NADP
what is photolysis?
splitting water into protons, (H+ ions), electrons and oxygen
what is photophosphorylation?
making ATP from ADP and Pi
what are coenzymes?
a molecule that aids the function of an enzyme + they do this by transferring a chemical group from one molecule to another
what 3 things is the energy resulting from photoionisation used for?
- making ATP from ADP and Pi- photophosphorylation
-making reduced NADP from NADP
-splitting water into protons (H+ ions), electrons + oxygen- photolysis
what is oxidation?
gain of oxygen, loss of hydrogen, loss of electrons
what is reduction?
loss of oxygen, gain of hydrogen, gain of electrons
what is phosphorylation?
adding phosphate to a molecule
why is ATP a good energy source?
-stores and releases small, manageable amounts of energy at a time
-small + soluble so can be transported around the cell
-easily broken down so instantaneous energy source
-quickly remade
-can make other molecules more reactive by phosphorylating them
-cant pass out of the cell so cells always have an immediate energy source
what is the structure of the chloroplasts?
small, flattened organelles, double membranes, thylakoids are stacked in the chloroplast into grand, grana linked together by thylakoid membranes called lamellae
what do chloroplasts contain so they can fulfil their function?
photosynthetic pigments e.g. chlorophyll a, chlorophyll b and carotene. they are coloured substances that can absorb knit and found in the thylakoid membrane attached to proteins.
what is a photosystem?
a pigment and a protein
Describe the Steps of the Calvin cycle
· Ribulose Biphosphate (RuBP) acts as a carbon dioxide acceptor.
· The enzyme RuBisco catalyses the reaction between CO2 and RuBP to form two molecules of Glycerate 3 Phosphate(GP). This is known as carbon fixation.
· The GP is reduced to triose phosphate (TP)
· This requires hydrogen from the NADPH and the energy from the hydrolysis of ATP.
· Some of the TP is converted into useful carbohydrates, amino acids and triglycerides.
· Some TP is used to regenerate RuBP
What are the limiting factors for photosynthesis?
Light intensity, CO2 conc and temperature
How do farmers maintain a high rate of photosynthesis?
- Artificial light may be used to increase light intensity to the optimum levels. Blinds may be used to shade plants if light intensity is very high as very high light intensity may damage the chlorophyll
- Carbon dioxide levels can be increased by burning fossil fuels ( e.g. paraffin heaters ) or pumping CO2 into the glasshouse
- Heaters can be used to raise the temperature to optimum levels ( also used at night to prevent temperatures falling to levels where plants may be damaged)
what is produced during the photolysis of water during the light dependent reaction?
protons, electrons and oxygen
what are the electrons prpduced during photolysis used for?
to recharge the chlorophyll
what 2 things is light energy used for at the start of the LIR?
photoionisation of chlorophyll and photolysis of water
what two products of the LDR are needed in LIR?
reduced NADP and ATP
where does the LIR reaction take place?
stroma
plant produce ATP in their chloroplasts during photosynthesis. they also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis
- in the dark no ATP production in photosynthesis
2.some tissues unable to photosynthesise
3.ATP cannot be moved from cell to cell
4.plant uses more ATP than produced in photosynthesis - ATP for active transport
