Chapter 11 - Photosynthesis Flashcards
What does organic mean in biochemistry?
Contains carbon
What does inorganic mean in biochemistry?
Does not contain carbon
Define coenzyme
Molecule that helps enzyme to work by transferring other molecules. (NAD, NADP and FAD in respiration and photosynthesis)
Define phosphorylation
Adding a phosphate
Define photophosphorylation
Using light energy to add a phosphate
Define photolysis
Using light energy to split a molecule
Define ETC
When electrons flow through proteins in a series of redox reactions to transfer energy in a cell membrane
What occurs in photosynthesis and where?
Light dependant = Thylakoid membrane
Light independant = Stroma
Summarise structure of chloroplast
Double membrane with grana (discs of thylakoid) joined by lamellae surrounded by stroma
What adaptations do thylakoids have for photosynthesis?
- High SA for photosynthesis
- Contain chlorophyll for light absorbance
Summarise the light dependant reaction
- Light strikes PSII and excites e- to a higher energy level
- e- released down ETC, PSII becomes ionised, and e- releases energy to proton pumps and then reaches PSI
- H+ builds up in thylakoid and diffuses down gradient through ATP synthase causing photophosphorylation
- Light strikes PSI causing e- to leave membrane into stroma and bond with H+ and NADP to produce NADPH to maintain gradient
- Light strikes water and splits water into 2H+, 2e- and 0.5O2
Summarise the light independent reaction
- Uses products of light dependant to form organic compounds
- RuBP carboxylated by rubisco to form 2 GP
- GP reduced into TP by one NADPH and one ATP
- TP the converted into useful organic substances such as glucose or reformed into RuBP by ATP
What occurs if no light is present in photosynthesis?
- RuBP decreases as converted into GP but not reformed from TP as no ATP
- GP increases
What occurs if no CO2 is present in photosynthesis?
- RuBP increases as reformed from TP but not converted into GP as no CO2
- GP decreases
Summarise the effect of light intensity on photosynthesis and suggest how to combat it as a limiting factor
- Higher light provides higher rate of LDR as more energy
- Light must be right wavelength for chlorophyll pigments
- Use lighting at night and greenhouse to allow light to pass
Summarise the effect of CO2 concentration on photosynthesis and suggest how to combat it as a limiting factor
- CO2 limiting during the day
- Optimum at 0.4%
- Greater than optimum has negative effect as
- Burn fossil fuel in greenhouse to increase CO2
Summarise the effect of temperature on photosynthesis and suggest how to combat it as a limiting factor
- Photosynthesis controlled by enzymes
- Increase temp increase reaction until after optimum
- Higher temperature causes more transpiration so less water and closed stomata so less CO2
- Burn fuel to increase temperature
- Greenhouse traps warm air
- Thermostat to control temperature
What are the two purposes of the light-dependant reaction?
- To add inorganic phosphate to ADP creating ATP
- TO split water into H+ ions (protons) and OH- ions
How are chloroplasts adapted for the light-dependant reaction?
- Membranes provide large SA for attachment of chlorphyll, electron carriers and enzymes
- Proteins hold grana to maximise light absorption
- Grana membranes have ATP synthase and are selectively permeable to maintain proton gradient
- Chloroplasts contain DNA and ribosomes to manufacture own products
How is the chloroplast adapted for the light-independent reaction?
- Fluid of stroma contains enzymes and membrane bound so high concentration of required substances
- Stroma surrounds grana so products of light dependant reaction diffuse readily
- Contains DNA and ribosomes to manufacture proteins
How are leaves adapted for photosynthesis
- Large SA for sunlight
- Leaves that minimise overlapping
- Thin so diffusion distance short
- Transparent cuticle and epidermis to let light through to mesophyll
- Long mesophyll with chloroplasts to collect sunlight
- Stomatas for gas exchange near mesophyll for short diffusion pathway
- Stomata open and close according to LI
- Air spaces for diffusion
- Xylem for water and phloem for sugars
