2.9 Photosynthesis Flashcards
Photosynthesis
Process through which solar light energy is captured by chlorophyll and converted into chemical bond energy stored in organic molecules using water and carbon dioxide
Which is the shortest and longest wavelength in visible light spectrum?
Shortest= violet Longest = red
What are the wavelengths our eyes can detect?
Between 400-700nm
Chloroplast
An organelle that contains chlorophyll (green pigment) and traps light energy
Where is chloroplast located?
Mesophyll cells and guard cells
Which is the primary pigment?
Chlorophyll A
Which light does chlorophyll A absorbs most and least effectively?
Absorbs red and blue most effectively. Doesn’t absorb green light at all
What light does chlorophyll A reflect?
Green
Difference between absorption and action spectrum
Absorption: Shows which wavelength is absorbed by a particular photosynthetic pigment
Action: Shows efficiency of rate of photosynthesis at each wavelength in visible spectrum
Which peak is higher in absorption spectrum: blue or red?
Blue as it’s absorbed more
Accessory pigments
Allows some plants to take advantage of green wavelength. Beneficial for underwater plants
Why do leaves turn brown in the fall?
Active chlorophyll has accessory pigments that cannot be seen but when temperatures cool, those pigments are broken down and hence shown
Photolysis
Stage of photosynthesis where water is split by light
What does 2H2O+energy in photons give?
4e-, 4H+ and O2
Where do the electrons, H ions and O2 go after photolysis?
Electrons and hydrogen ions are used later in photosynthesis, oxygen is a waste product that diffuses out
Is photosynthesis anabolic or catabolic?
It is anabolic (small to large molecules)
What is light-dependent reaction? Where does it occur?
Requires the use of light to split water and create ATP, making H+ ions. Occurs in the thylakoids
What is light independent reactions and where do they occur?
Occurs without light and uses ATP and H+ ions to ‘fix’ carbon dioxide making glucose. Takes place in the stroma of chloroplasts
What is carbon fixation also known as?
Calvin cycle
Steps of light-independent reaction
- H ions + NADP= NADPH
- e- + ADP = ATP
- ATP and NADPH move to Calvin cycle
- CO2 is used to form complex sugars
- Calvin cycle gives ADP and NADP back to light reactions
Limiting factor
Factor that restricts rate of reaction when present in low amounts
Why will photosynthesis plateau at a certain light intensity?
Photosynthesis operates with a certain number of photosystems that capture photons. If they are all occupied, rate cannot increase
Why will photosynthesis plateau at a certain carbon dioxide conc.?
Once all active sites of the enzymes are occupied with a substrate, any increase in CO2 will not increase the rate
Relationship between temperature and photosynthesis and reason
Rate will increase as temperature increases however past optimum temperature, enzymes start to denature and rate decreases. Graph will show a peak
Chromatography
Technique used to separate mixture of substances based on movement of different constituents on piece of paper by capillary action
What phase is paper and solvent?
Paper is stationary phase while solvent is mobile phase
Retention factor
Ratio of distance moved by pigment to distance moved by solvent
What can Rf be used to identify in photosynthesis
The different chlorophyll pigments
Thin layer chromatography + advantages
Uses silica gel or cellulose instead of paper. Gives better result as it’s well defined.
