Karteikarten
Section 5 - Photosynthesis
Karten in diesem Stapel (23)
- 1Where specifically do the two stages of photosynthesis take place?LDR - Thylakoid membranes
LIR - Stroma - 2What are the two stages of photosynthesis?Light dependent
Light independent - 3Why is light necessary for the LDR to take place?Required to provide energy for photolysis, which splits water into protons, electrons and oxygen.
- 4Where does most photosynthesis take place in leaf? Why?Palisade mesophyll cells - Tightly packed with many chloroplasts to maximise light for efficient photosynthesis
- 5What is the overall equation for photosynthesis?6CO2 + 6H2O ---> C6H12O6 + 6O2
- 6What are the products of the LDR?NADP/H2, ATP, Oxygen
- 7What are the products of the LIR?Organic substances (glucose, amino acids etc)
- 8What is photolysis?The splitting of a water molecule using light to release protons, electrons and oxygen.
- 9What absorbs light energy?Photosynthetic pigments in photosystems in the thylakoid membranes.
- 10Give 3 photosynthetic pigmentsChlorophyll A
Chlorophyll B
Carotenoids
Xanthophyll - 11How can photosynthetic pigments be separated and analysed?Thin layer chromatography - CPAC
- 12Describe what happens after light strikes water in the LDR, starting at PS2, ending at the ETC.Light strikes PS2 and excites electrons to a higher energy level (photoexcitation), leaving a positive charge in the photosystem. this charge is neutralised by electrons from photolysis. The excited electrons are received in an electron acceptor, and they then go through a series of oxidation and reduction reactions called the electron transport chain.
- 13How is ATP produced from photosynthesis?Energy lost from electrons in ETC powers a proton pump in the thylakoid membrane, which pumps protons outside the membrane, creating an electrochemical gradient. Protons can then pass back through the membrane down a conc gradient through the ATP synthase channels, the enzyme is able to catalyse the reaction of ADP + Pi --> ATP.
- 14What happens to the electrons after they pass through the ETC?They enter photosystem 1. When light strikes PS1, the electrons are excited again to an even higher energy level, and are received at another electron acceptor. These electrons then combine with NADP and protons to form reduced NADP, the primary product of the LDR.
- 15How are chlorophyll adapted for the LDR process?The thylakoid membranes have a huge surface area for the attachment of chlorophyll, electron carriers and enzymes for the LDR.
Proteins hold the chlorophyll to allow the maximum absorption of light.
Chloroplasts contain DNA and ribosomes so they are able to produce some proteins for the LDR. - 16What is the process of the light independent reaction also called?The Calvin Cycle
- 17How does CO2 enter the leaf?Through the stomata
- 18What is the first step in the Calvin cycle?CO2 combines with ribulose bisphosphate (RuBP), a 5 carbon compound, in a reaction catalysed by rubisco, an enzyme, to form an unstable 6 carbon compound. This compound immediately breaks down into 2 3 carbon compounds called glycerate 3-phosphate, or GP.
- 19What happens in the LIR after GP has been formed?The two GP molecules are reduced to TP, triose phosphate. This reaction uses 2 ATP molecules and 2 reduced NADP molecules, as the ATP provides energy, and reduced NADP provides protons. Reduced NADP is recycled to NADP.
- 20What happens to the two TP molecules in the LIR?5 out of every 6 molecules of TP are used to regenerate RuBP, using a molecule of ATP. The final TP molecule is used to produce useful organic compounds.
- 21Give three compounds produced from the LIR.Hexose sugars
Triglycerides
Amino acids - 22How many turns does the Calvin cycle need to go before producing an organic substance?6 - 1 in 6 TP molecules are used for formation of a useful product.
- 23What are the limiting factors for photosynthesis?Temperature - for enzymes
Carbon dioxide concentration - for the LIR - any higher than 0.4% though the stomata begin to close
Light intensity at a certain wavelength - only certain wavelengths absorbed by different pigments.
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- A level Biology Karteikarten am Section 5 - Photosynthesis, erstellt von Adam Parkes am 12/04/2021.
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