Photosynthesis Flashcards
Describe why autotrophs are important to life
- autotrophs undergo photosynthesis
- this produces biomass
- provides direct food source for consumers
- provides food source for the food source of consumers
Why does photosynthesis require energy from the sun whilst respiration does not?
The energy required to break bonds in small organic molecules is greater than the energy released from the formation of organic molecules.
Why does respiration not require sunlight whilst photosynthesis does?
Total energy required to break all bonds in complex organic molecules is less than the total energy released in the formation of all bonds in the smaller organic products. Excess energy released by the formation of the bonds used to synthesise ATP.
What is the overall equation for photosynthesis?
6H2O + 6CO2 —> C6H12O6 + 6O2
What is a stack of thylakoid membranes called?
Granum
What connects the granum in a chloroplast?
Lamellae
What are the two stages of photosynthesis?
The light dependent and light independent stages
Where do the light dependent stages of photosynthesis occur?
On thylakoid membranes in chloroplasts
Where do the light independent reactions of photosynthesis occur?
In the stroma of chloroplasts
What is another name for the light independent reactions?
The Calvin cycle
Define photosynthetic pigment
Substances which absorb light energy and convert it into chemical energy. Different photosynthetic pigments absorb different wavelengths of light energy
In which part of photosynthesis are photosynthetic pigments used?
Light dependent reactions
Define light harvesting system
A group of protein and chlorophyll molecules found in the thylakoid membranes of the chloroplasts in a plant cell
Define reaction centre
A complex of proteins and chlorophyll a which undergoes the primary energy conversion of photosynthesis
Define photosystem
Protein complexes involved in the absorption of light and electron transfers in photosynthesis
Which pigment is found the the reaction centres of photosystems?
Chlorophyll a
What is the primary pigment in photosynthesis?
Chlorophyll a
What are antennae pigments?
Photosynthetic pigments other than chlorophyll a
What is the function of antennae pigments?
They absorb different wavelengths of light to chlorophyll a, and channel this light energy to the reaction centres.
Give 3 examples of antennae pigments
Chlorophyll b
Xanthophylls
Carotenes
What is the purpose of having different photosynthetic pigments in chloroplasts absorbing different wavelengths?
- allows a wider range of wavelengths of light to be absorbed
- more light energy therefore can be absorbed makes photosynthesis more efficient
- ensures pigments don’t compete for same wavelength
Explain how a large number of thylakoids/grana in a chloroplast adapt chloroplasts for photosynthesis
- provides large surface area for the light dependent stage to occur on
- ensures plenty of ATP and reduced NADP is provided for the light independent stage
Explain how the presence of stroma surrounding thylakoid membranes adapts chloroplasts for photosynthesis
- allows products of light dependent reaction to pass efficiently from the thylakoid membranes to the stroma
- stroma is the site of light independent reaction, which requires the products of the light dependent reaction
Explain how the presence of a double membrane separated by intermembrane space adapts chloroplasts for photosynthesis
It allows a proton gradient to be formed between the stroma and intermembrane space
What are the useful products of the light dependent reaction?
Reduced NADP
ATP
What is the waste product of the light dependent reaction?
O2