𝐩𝐡𝐨𝐭𝐨𝐬𝐲𝐧𝐭𝐡𝐞𝐬𝐢𝐬 Flashcards
Describe what happens during the Light Dependent Reaction? (5)
Chlorophyll absorbs light energy in photosystem II and the photolysis of water produces oxygen, H+ and e-. The energy results in electrons becoming excited. They move down the electron transfer chain releasing energy. Energy is used for ADP + Pi –> ATP. NADP is reduced by e- and H+.
Describe chemiosmosis.
The electrons that gained energy and left the chlorophyll move along proteins embedded within the thylakoid membrane. As they move along, they release energy and some of the energy is used to pump the protons from photolysis across chloroplast membranes. The protons pass through the enzyme ATP synthase, which results in the production of ATP. The protons move from a high to low concentration gradient so the process is known as chemiosmosis.
Describe and explain why burning forests affect the CO2 concentration in the atmosphere. (4)
The CO2 concentration will increase as trees are burnt, so there will be less plants leading to less photosynthesis. Therefore, less CO2 is being removed from the atmosphere.
Explain how a problem with the electron transfer chain decreases the uptake of oxygen. (3)
Less NADPH is being formed therefore less TP is converted to RuBP, so less RuBP is available to combine with CO2.
Describe how CO2 is converted into organic substances in the Calvin Cycle. (6)
-CO2 combines with RuBP to produce two molecules of GP.
- GP is then reduced to TP with the help of ATP and NADPH
[ATP hydrolyses back into ADP + Pi, NADPH is oxidised to NADP].
-TP is then converted to useful organic substances e.g. glucose.
-Some TP is used to regenerate RuBP in the Calvin cycle.
Describe how carbon in CO2 becomes carbon in TP. (5)
CO2 combines with RuBP, to produce two molecules of GP. GP is then reduced to TP. NADPH acts as a reducing power and ATP is also used in this reaction.
Describe the changes in CO2 concentration in air at different heights above a forest over different times. (5)
- No photosynthesis during the night time due to no light
- Therefore, a high concentration of CO2
- Concentration of CO2 increased as plants respire
- In the day, concentration of CO2 falls as plants photosynthesis
- CO2 concentration is higher at lower levels due to less photosynthesising tissues.
Describe the Light-Independent reaction.
-CO2 reacts with RuBP to form 2 molecules of GP (3C compound).
- This reaction if catalysed by enzyme rubisco.
-To reduce GP to TP, ATP and NADPH from the LDR are used.
-Some of the carbon from TP leaves the cycle to be converted into useful organic substances.
-The rest of TP is used to regenerate RuBP with the energy from ATP.
Where does the light-dependent reaction occur?
thylakoid membrane of chloroplasts
Where does the light-independent reaction take place?
In the stroma of the chloroplast
Explain how temperature affects the rate of photosynthesis.
𝗔𝘀 𝘁𝗲𝗺𝗽 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀, 𝗿𝗮𝘁𝗲 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀:
-Enzymes e.g. Rubisco gain kinetic energy
-so more enzyme-substrate (E-S) complexes
𝗔𝗯𝗼𝘃𝗲 𝗮𝗻 𝗼𝗽𝘁𝗶𝗺𝘂𝗺 𝘁𝗲𝗺𝗽, 𝗿𝗮𝘁𝗲 𝗱𝗲𝗰𝗿𝗲𝗮𝘀𝗲𝘀:
-enzymes denature as H bonds in tertiary structure break
-so fewer enzyme-substrate (E-S) complexes form.
Explain how light intensity affects the rate of photosynthesis.
𝗔𝘀 𝗹𝗶𝗴𝗵𝘁 𝗶𝗻𝘁𝗲𝗻𝘀𝗶𝘁𝘆 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀, 𝗿𝗮𝘁𝗲 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀:
-Light-dependent reaction increases (e.g., more photoionisation of chlorophyll), producing more ATP and reduced NADP.
-So light-independent reaction increases as more GP is reduced to TP and more TP regenerates RuBP.
𝗔𝗯𝗼𝘃𝗲 𝗮 𝗰𝗲𝗿𝘁𝗮𝗶𝗻 𝗹𝗶𝗴𝗵𝘁 𝗶𝗻𝘁𝗲𝗻𝘀𝗶𝘁𝘆, 𝗿𝗮𝘁𝗲 𝘀𝘁𝗼𝗽𝘀 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗶𝗻𝗴:
-another factor is limiting e.g. temp.
Explain how CO2 concentration affects the rate of photosynthesis.
𝗔𝘀 𝗖𝗢𝟮 𝗰𝗼𝗻𝗰. 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀, 𝗿𝗮𝘁𝗲 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝘀:
- Light-Independent reaction increases
-As more CO2 combines with RuBP to form GP
-So more GP is then reduced to TP
-So;p more TP is converted to organic substances and more RuBP is regenerated.
𝗔𝗯𝗼𝘃𝗲 𝗮 𝗰𝗲𝗿𝘁𝗮𝗶𝗻 𝗖𝗢𝟮 𝗰𝗼𝗻𝗰., 𝗿𝗮𝘁𝗲 𝘀𝘁𝗼𝗽𝘀 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗶𝗻𝗴:
-Another factor is limiting e.g. temp
Explain the key consideration when evaluating data relating to agricultural practices used to overcome the effect of limiting factors.
𝗔𝗴𝗿𝗶𝗰𝘂𝗹𝘁𝘂𝗿𝗮𝗹 𝗽𝗿𝗮𝗰𝘁𝗶𝗰𝗲𝘀 𝘀𝗵𝗼𝘂𝗹𝗱 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲 𝘁𝗵𝗲 𝗿𝗮𝘁𝗲 𝗼𝗳 𝗽𝗵𝗼𝘁𝗼𝘀𝘆𝗻𝘁𝗵𝗲𝘀𝗶𝘀, 𝗹𝗲𝗮𝗱𝗶𝗻𝗴 𝘁𝗼 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝗱 𝘆𝗶𝗲𝗹𝗱:
-as more glucose produced for faster respiration
-so more ATP to release energy for growth e.g. cell division
𝗣𝗿𝗼𝗳𝗶𝘁 𝗳𝗿𝗼𝗺 𝗲𝘅𝘁𝗿𝗮 𝘆𝗶𝗲𝗹𝗱 𝘀𝗵𝗼𝘂𝗹𝗱 𝗯𝗲 𝗴𝗿𝗲𝗮𝘁𝗲𝗿 𝘁𝗵𝗮𝗻 𝗰𝗼𝘀𝘁𝘀.
Give 3 ways the chloroplast is adapted for the light-independent reaction to occur-> [non-spec q]
- The fluid of the stroma contains all enzymes needed to carry out the L.I.R
- The stroma fluid surrounds the grana and so the products of the light-dependent reaction in the grana can readily diffuse into the stroma.
- The stroma fluid contains both DNA and ribosomes so it can quickly and easily manufacture some of the proteins involved in L.I.R.
