Photosynthesis Flashcards
What is chlorophyll?
- a green pigment found in chloroplasts that absorbs light energy used in photosynthesis
What is the stroma?
- contains enzymes, 70S ribosomes, circular DNA
- site of light independent stage
What are lamellae?
- membranes in the chloroplast
What are thylakoid membranes?
- enclose fluid-filled sacs (thylakoid spaces)
- site of light dependent stage
What are grana?
- stacks of thylakoid membranes
- large SA, so faster light dependent reactions
- lots of light absorbed
What are the photosynthetic pigments?
Chlorophylls:
- chlorophyll a: yellow-green
- chlorophyll b: blue-green
Carotenoids:
- carotene: orange
- xanthophyll: yellow
Explain the absorption spectrum for pigments:
- chlorophyll absorbs red and reflects green light
- carotene absorbs blue light
Explain the absorption spectrum for pigments:
- chlorophyll absorbs red and reflects green light
- carotene absorbs blue light
What is a photosystem?
- cluster of light harvesting pigments surrounding a reaction centre
What is a reaction centre?
- part of photosystem where energy from light is funneled
- contains a pair of chlorophyll a molecules; absorbs energy and emits electrons
What wavelength of light do each photosystem absorb?
- photosystem 1: 700nm
- photosystem 2: 680nm
What is an action spectrum?
- a graph showing the effect of different wavelengths of light on a process, e.g; the rate of photosynthesis
What is an absorption spectrum?
- graph showing the absorbance of different wavelengths of light by a photosynthetic pigment
- more absorption = more photosynthesis
What is photophosphorylation?
- production of ATP from light energy
What is photolysis?
- splitting of water from light producing H+ ions
What is photo activation?
- emission of an electron as a result of absorption of light energy by a photosystem
What is cyclic photophosphorylation?
- production of ATP using energy from light involving only photosystem 1
What is non-cyclic photophosphorylation?
- production of ATP from light energy involving both photosystems
- also produces reduced NADP
What is oxygen-evolving complex?
- enzyme found in photosystem 2
- catalyses breakdown of water using energy from light
- H20 —-> 2H+ + 2e- + 1/2O2
- also know as water splitting complex
Outline the process of the Calvin Cycle:
- Ribulose bisphosphate/RuBP (5C) combines with CO2 by the enzyme rubisco
- an unstable (6C) intermediate forms
- then converted to 2x glycerate 3-phosphate/GP (3C)
- 2x GP broken into 2x triose phosphate/TP (3C)
- 1x reduced NADP is oxidized and 2x ATP molecules used
- 5/6 TP used to generate RuBP
- 1/6 TP used to regenerate energy sources, e.g; hexose, fatty acids, acetyl CoA
What is a limiting factor?
- when a process is affected by more than one factor
- the factor prevents any further increase in the rate of the process
What are the limiting factors of photosynthesis?
- Light
- Temperature
- Carbon dioxide
other factors
- water
- photosynthetic pigments
What are the functions and structure of a chloroplast?
thylakoid/grana
- site of light dependent reactions
thylakoid membrane
- large SA to absorb more light
- has pigments, photosystems, electron carriers, ATP synthase
stroma
- contains enzymes (rubisco)
- colourless so light can enter
- water as a reaction medium
DNA/ribosomes
- make chloroplast proteins
starch grains
- store glucose produced from photosynthesis
envelope
- compartmentalization
