Chapter 10: Photosynthesis
Describe how and where photosynthesis takes place in the plant
(light-dependent reactions capture the energy from the sunlight) 1. Energy from sun is absorbed & oxygen is released (in the chloroplasts) 2. energy transfers to molecules that carry energy like ATP (across the thylakoid membrane) (light-independent reactions use the energy to make sugars) 3. Carbon dioxide molecules area used to build sugars (Energy from light-dependent reactions is used) 4. simple sugar molecules are formed.
List different photosynthetic pigments and describe their role
1. Carotene - color = yellow, orange, red - all present in plants, algae, cyanobacteria - Two main functions in plants: a = accessory pigments in photosynthesis. b = coloring in reproductive parts of flowers and fruits to enhance pollination and fruit dispersal. 2. Xanthophyll - color = yellow - harvests light that chlorophyll can't - transfers light energy to chlorophyll - absorbs excess light that would kill chlorophyll 3. Chlorophyll a - color = blue green - a key light-capturing pigment that participates directly in the light reaction pigment - main photosynthetic pigment in algae and cyanobacteria. occurs in all photosynthetic eukaryotes and cyanobacteria. 4. Chlorophyll b - color = olive green - accessory pigment - capture additional light energy which is then transferred to chlorophyll a - occurs in most but not all plants
Describe alternative mechanism of carbon fixation with examples
1. Stomata Small pores in the surface of a leaf that can be opened and closed to control the exchange of gases between the atmosphere and the leaf interior. 2. Photorespiration The catalyst of O2 instead of CO2 by rubisco into RuBP, which slows the Calvin cycle, consumes ATP, and results in a release of carbon. 3. C4 cycle An alternative form of carbon fixation that some plants use, particularly in hot weather, to increase the concentration of CO2 available for the Calvin cycle reactions. 4. Crassulacean Acid Metabolism (CAM) A metabolic pathway, used mostly by succulent plants, in which the Calvin cycle and the C4 cycle are separated in time for better efficiency of CO2 fixation
Explain photorespiration
A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco.
Describe photosynthesis
A series of reactions that create carbon dioxide and water to create glucose and oxygen is a bi-product the energy to produce glucose comes from ATP
Explain the significance of photosynthesis to other living organisms
Food like plants for animals that we eat (our food) survive off autotrophs (plants) to grow
Explain how plants absorb energy from sunlight
Plants capture the light energy from the sun using the green chemical chlorophyll contained in organelles called chloroplasts in the leaves and other green parts of the plant
Define carbon fixation
Refers to the conversion process of inorganic carbon (carbon dioxide) to organic compounds by living organisms
Describe the Calvin Cycle
Step 1 : Carbon dioxide fixation Process by which carbon dioxide gas is attached to the organic compound. A molecule of carbon dioxide is attached to RUBP a 5 carbon molecule. The result is one 6 carbon molecule( splits to 3) Step 2: Reduction of Carbon Dioxide Each of two 3PG molecules undergoes reduction to G3P. As 3PG becomes G3P, ATP becomes ADP+P and NADPH becomes NADP Step 3 : Regeneration of RUBP As the five molecules of G3P become three molecules of RUBP, three molecules of ATP become three molecules of ADP+ Put
Identify the substrates and products of photosynthesis
Substrates: CO₂, 6H₂0, sunlight Products: C₆H₁₂O₆, 6O₂
Describe the main structures involved in photosynthesis
The chloroplast is where photosynthesis takes place. The thylakoid, grana, stroma and chlorophyll are inside the chloroplast and the molecules are carbon dioxide and water
Describe different types of electron flow during light dependent reaction
oxygen is generated from splitting of water, electron transport results in the reduction of NADP+ and NADPH, light energy is captured by pigment molecules and passed to chlorophyll a, electron transport generates a proton gradient concentration difference which drives ATP production
