CH.7 Photosynthesis Flashcards
Describe the importance of photosynthesis for life on the planet.
oxygen production, energy source, carbon fixation,ecosystem support,food production
Define photosynthesis.
the process by which green plants, algae, and some bacteria use light energy to convert carbon dioxide and water into glucose (a carbohydrate) and oxygen, with the help of chlorophyll and other pigments.
Describe the anatomy of a chloroplast.
Outer and inner membranes: Enclose the chloroplast.
Stroma: A semi-fluid matrix where the Calvin cycle (dark reactions) occurs.
Thylakoid membranes: Flattened, membrane-bound sacs where the light reactions take place.
Grana (singular: granum): Stacks of thylakoid membranes.
Explain the difference between the absorption spectrum of chlorophyll and the action spectrum of photosynthesis.
The absorption spectrum of chlorophyll shows which wavelengths of light are absorbed by chlorophyll pigments. It reveals that chlorophyll mainly absorbs light in the blue and red regions of the spectrum.
The action spectrum of photosynthesis illustrates the efficiency of photosynthesis at different wavelengths of light. It shows that photosynthesis is most active in the blue and red regions of the spectrum, consistent with the absorption spectrum of chlorophyll.
List and describe the pigments of photosynthesis.
Chlorophyll a: Absorbs mainly red and blue-violet light.
Chlorophyll b: Absorbs mainly blue and red-orange light and complements chlorophyll a.
Carotenoids: Absorb blue and green light and broaden the range of light absorption.
Phycobilins: Found in some photosynthetic bacteria and red algae, and absorb light in the blue and red regions.
Describe the major events in light reaction and the Calvin cycle, including the reactants and products of each stage.
Light Reaction:
Reactants: Light, water, ADP, NADP+, and chlorophyll.
Products: Oxygen, ATP, NADPH.
Calvin Cycle:
Reactants: Carbon dioxide, ATP, NADPH.
Products: Glucose and other carbohydrates, ADP, NADP+.
Describe how a photosystem captures light energy.
Photosystems are protein-pigment complexes located in the thylakoid membranes. Each photosystem consists of chlorophyll and other pigments organized in a light-harvesting complex. When light energy is absorbed by these pigments, it excites electrons, which are then transferred through an electron transport chain.
Explain how the light reactions and the Calvin cycle depend on each other.
Light reactions produce ATP and NADPH, which are used in the Calvin cycle to convert carbon dioxide into glucose.
The Calvin cycle generates ADP and NADP+ (which return to the light reactions) and produces organic molecules that store energy.
Trace the pathway of an electron through the light reactions. Where does each electron begin, and where does it end?
Each electron begins in a water molecule, where it is excited by light in photosystem II (PSII). It then moves through the electron transport chain, contributing to the generation of a proton gradient and the production of ATP. The electron eventually reaches photosystem I (PSI), where it is re-energized by light. NADP+ is reduced to NADPH, and the electron is used in the Calvin cycle.
Explain how ATP is synthesized during the light reactions.
ATP synthesis in the light reactions occurs through chemiosmosis. Protons (H+) are pumped into the thylakoid space, creating a proton gradient. As protons flow back into the stroma through ATP synthase, ATP is synthesized.
List where the carbons and potential energy are at the beginning and end of each of the two major stages of photosynthesis.
in the light reactions, carbon is not involved, and the main product is high-energy molecules like ATP and NADPH.
In the Calvin cycle, carbon dioxide is fixed and reduced, leading to the formation of glucose and other carbohydrates, which store potential energy.
Explain the interactions between photosynthesis and cellular respiration.
Photosynthesis provides the organic molecules and oxygen needed for cellular respiration, while cellular respiration supplies the carbon dioxide and water required for photosynthesis. These processes are interdependent and balance the flow of energy and matter in ecosystems.
Explain how rubisco is involved in photorespiration.
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is an enzyme involved in both photosynthesis and photorespiration. In photorespiration, rubisco binds with oxygen instead of carbon dioxide, leading to the loss of carbon compounds and energy.
Explain how the C4 pathway and CAM reduce the effects of photorespiration, but each has a metabolic cost.
Both the C4 and CAM pathways are adaptations to reduce photorespiration in arid environments. They minimize the loss of carbon compounds by concentrating CO2, although they require more energy to operate.
Compare and contrast C3 photosynthesis, C4 pathway, and CAM including the optimal environment for each.
C3 Photosynthesis: Common in most plants; works well in moderate climates.
C4 Pathway: Used by some plants in hot and arid conditions; spatial separation of carbon fixation.
CAM (Crassulacean Acid Metabolism): Used by succulent plants in arid environments; temporal separation of carbon fixation.
