Flashcards
Photosynthesis
Cards in this deck (19)
- 1Describe what happens in the light dependent reaction and what is madeThe light dependent reaction occurs in the thylakoid membranes.
1) Light energy excites the electrons in chlorophyll (photo excitation) to a higher energy level
2) They then pass down the electron transfer chain located in the thylakoids down an energy gradient
3) The passage involves redox reactions
4) The energy from the excited electrons is what generates ATP and NADP
5) ATP is generated from phosphorylating ADP
6) The excited electrons are replaced by photolysis of water (which has protons, electrons and oxygen as products)
7) The hydrogen ions produced are taken up by NADP - it becomes reduced to NADPH
8) Oxygen is a by-product - 2Describe how triose phosphate is produced in the Calvin Cycle- CO2 fixes onto Ribulose (5C) Bisphosphate and this forms an unstable 6C molecule
-Which breaks down into two molecules of 3C glycerate-3-phosphate
-Rubisco catalyses the carbon fixation reaction between CO2 and RuBP
-The ATP from the LDR provides energy to turn GP into 2 molecules of TP
-this reaction also needs the H+ ions from the NADPH formed in the LDR reaction. H+ from NADPH reduce GP to TP
- 3How are chloroplasts adapted for the light-dependent reaction?-Thylakoid membrane - increases SA for attachment of enzymes, chlorophyll and electron carriers
- Granal membranes - enzymes attached which help manufacture ATP
-Chloroplasts contain DNA ribosomes to make proteins needed in PS
- 4How are chloroplasts adapted for the Light-independent reaction?-Stroma contain necessary enzymes for PS
-Stroma surrounded by grana - products of LDR can diffuse into stroma
DNA and ribosomes - protein synthesis for PS
- 5What are the roles of ATP and NADPH in the light-independent reaction?Calvin cycle - occurs in the stroma of the chloroplasts
CO2 diffuses in through the stomata and enters stroma of chloroplast
It combines with the 5C compound RuBP using Rubisco
This produced 2 molecues of 3-C Glycerate Phospate (GP)
ATP and reduced NADP from LDR are used to reduce the GP into triose phospate (TP)
The NADP is re-formed and goes back into the LDR to be reduced again
Some TP is converted into useful subs (e.g. glucose)
Most of TP (5/6) is used to regenerate RuBP using ATP from the LDR
- 6If you are measuring photosynthesis using photosynthometer - which units/measurements must you take?- distance and time
- mass of x
- radius of tubing
- 7What is the Calvin cycle?A biochemical pathway (part of the light-independent reaction) where CO2 is reduced to form carbohydrate
CO2 + RuBP ---> GP ---> TP ---> Glucose or RuBP
- 8What is photolysis of water?Light energy splits water molecules, yielding electrons, hydrogen ions and oxygen (light-dependent reaction)
- 9What is the light-dependent reaction?Stage of photosynthesis in which light energy is required to produce ATP and reduced NADP
- 10What is the light-independent reaction?Stage of photosynthesis which does not require light energy directly, but does need the products of the light dependent reaction to reduce CO2 and form carbohydrate
- 11What is a limiting factor?A variable that limits the rate of a chemical reaction
- 12Explain variations of CO2 in air over 24hours at different heights in forest- High conc of CO2 in darkness
- No photosynthesis in dark
- In dark plants respire
- in light plants use more CO2 than they produce
- Decrease in CO2 conc with height
- at ground level less light - 13Describe the chemiosmotic theory/photophosphorylation-H+ from photolysis remain in thylakoid space
-ETC releases energy
-Energy used to pump H+ from stroma into thylakoid space
-By active transport
- this forms an electrochemical gradient
as H+ conc in thylakoid space > stroma
-H+ ions pass back from space between two mitochondrial membranes
-Through pores which are associated with the enzyme ATP synthase
-Energy from the ETC will be used to produce ATP
-Diffuse down conc gradient across thylakoid membrane
Produces ATP by photophosphorylation
- 14Describe the ultrastructures within the chloroplast and their functions-Thylakoid membrane: light-dependent → large surface area
-Associated with chlorophyll, accessory pigments, ETC, enzymes
-Grana: stacks of thylakoid membranes
which enclose hydrogen reservoir used in chemiosmosis
Lamella: tubular extensions forming a network between grana
-Stroma: RuBP carboxylase catalyses light independent reaction
-Starch granule → insoluble storage carbohydrate product of photosynthesis - 15What is the law of limiting factors?At any given moment, the rate of photosynthesis is limited by the factor that is at its least favourable value.
- 16Describe the effect of light intensity on photosynthesisThe rate of photosynthesis can be measured by the volume of O2 given off or CO2 used up in a given time.
When light is a limiting factor, the rate of photosynthesis is proportional to light intensity. The compensation point is the point at which O2 used up in respiration is equal to the O2 given off in photosynthesis. There is therefore no net gas exchange.
- 17Describe the effect of carbon dioxide on the rate of photosynthesisThe optimum CO2 concentration for photosynthesis is 0.1% whereas the CO2 concentration in the atmosphere is 0.04%.
High CO2 concentrations can effect the enzyme catalysed reactions that combine ribulose biphosphate with CO2. - 18Describe the effect of temperature on the rate of photosynthesisBetween 0 - 25 degrees the rate of photosynthesis approximately doubles for each 10 degrees rise in temperature.
Higher temperatures often cause the rate of photosynthesis to decrease since enzymes become denatured. - 19What do the limiting factor graphs look like?
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- A-Level Biology (Unit 4) Flashcards on Photosynthesis, created by kiruthicka on 18/12/2014.
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