Photosynthesis Flashcards
What is the equation for photosynthesis
6Co2 + 6H2O = C6H12O6 + 6O2 (carbon dioxide + water = glucose +oxygen)
How is the leaf adapted to carry out photosynthesis
Large SA, thin for short diffusion distance, transparent cuticle and epidermis to let light into mesophyll cells, mesophyll cells packed with chloroplasts, numerous stomata so no cell is far and stomata respond to light intensity, many air spaces for gas to diffuse and has xylem to bring water to leaves and phloem to transport sugars
Describe the structure and function of chloroplasts (draw it out!)
Have a double membrane/ envelope, stroma is a fluid filled matrix that holds lipids, ribosomes, circular dna and starch it is the sight of light independent reaction. Grana are stacks of thylakoids which contain chlorophyll in thylakoid membranes it’s the site of light dependent reaction
What are the main stages of photosynthesis
- Capturing of light energy by chloroplast pigments 2. Light DEPENDENT reaction in the thylakoid membranes 3. Light INDEPENDENT reaction in the stroma
What is the difference between the absorption and action spectrum
Absorption spectrum shows the wavelengths absorbed and action spectrum shows the rate of photosynthesis at each wavelength
Why are accessory pigments useful
They expand the wavelength range so more light is absorbed for photosynthesis
What colours does chlorophyll absorb and reflect
Absorb blue, violet and red ends but reflect green
What happens during the light dependent (full process)
- Chlorophyll absorbs light energy 2. Electrons in chlorophyll are excited at move from chlorophyll to electron transfer chain 3. Electrons release energy as they move along the ETC 4. The released energy is used to create a H+ conc gradient across the thylakoid membrane 5. Energy stored in this H+ gradient is used to join ADP with Pi to form ATP 6. Photolysis of water occurs releasing electrons, protons (H+) and oxygen, electrons replace those lost by excitation of chlorophyll 7. Electrons from electron transfer chain are transferred (with H+) to NADP, forming reduced NADPH
Explain the process of oxidation and reduction
OILRIG, oxidation is loss of electrons/hydrogen but gain of oxygen and reduction is gain of electrons/hydrogen but loss of oxygen
How are chloroplasts adapted to carry out the light dependent reaction
- Thylakoid membranes provide large SA for attachment of chlorophyll , electron carriers and enzymes in the LDR 2. Proteins in the grana hold chlorophyll in a way that allows maximum absorption of light 3.Granada membranes have ATP synthase channels which catalyse the production of ATP, also selectively permeable which allows H+ gradient 4. Chloroplasts have DNA and ribosomes to manufacture proteins in LDR
Describe the light independent reaction
- In the stroma, CO2 reacts with a 5 carbon acceptor RUBP, catalysed by the enzyme rubisco. 2. The reaction between CO2 and RuBP produces 2 molecules of the 3 carbon acid GP 3. 2GP is reduced to 2x3 carbon sugars triosphosphate/TP 4. Reduced NADP provides electrons to reduce GP to TP, conversion also requires energy from hydrolysis of ATP 5. 1/6 of the TP mols are used to make glucose/hexose/organic mols but 5/6 are used to regenerate RuBP using ATP to transfer a phosphate group
Name the compounds in the LIR and how many carbons they each have
- Co2= 1carbon 2. RuBP= 5 carbons 3. GP = 3 carbons each (6) , TP= 3c 4. Glucose/hexose= 6 carbons
Explain why the increase in dry mass of a plant over 12 month period is less than the mass of the hexose produced over the same period
Some hexose is used in respiration, carbon dioxide is produced and lost to the air and some parts of the plant may be eaten or lost to decomposes
Why does the concentrations of carbon dioxide in the air at diff heights above ground in forest Change over 24 hours
Increased conc of co2 linked with darkness as light needed for LDR in photosynthesis so no photosynthesis in the dark. In the dark, plants do respire but in light, the rate of photosynthesis is greater than the rate of respiration (use more co2 than produce) so conc of co2 falls with height as at ground level there’s less light and less leaves/photosynthesising tissue
