Light Reactions
What is the main purpose of the light reactions in photosynthesis?
To trap sunlight energy and convert it into chemical energy
What is another name for the Calvin Cycle often used in class notes?
The Calvin Cycle is also called the Dark Reactions (or Light-Independent Reactions).
What do we call the outermost part of the chloroplast?
The outer membrane
Write the basic reactants (two main inputs) required for photosynthesis using chemical formulas only.
CO2 and H2O
What term describes organisms that use light energy to make organic compounds?
Autotroph
Name the molecule split during the light reactions that releases electrons and produces oxygen as a byproduct.
Water; H2OH2O is split (photolysis) releasing electrons and producing O2O2.
What gas enters the Calvin Cycle and is fixed into organic molecules?
CO2
What structure is described as "Stacks of thylakoids" in the notes (include the common name)?
Grana.
Write the basic products (two main outputs) of photosynthesis using chemical formulas only.
C6H12O6 (sugar) and O2
Name one environmental factor listed that affects the rate of photosynthesis.
Temperature, Light intensity, or CO2 concentration
Where (which chloroplast structure) do the light reactions take place?
What is the thylakoid?
What is the main sugar (molecular formula) produced by the Calvin Cycle according to the provided notes?
Glucose
What is the fluid-filled space surrounding the grana called?
Stroma
The notes say photosynthesis is most efficient within a certain range of what environmental condition?
Temperature
During the light reactions, energy from sunlight is used to make two energy-carrying molecules used in the Calvin Cycle.
ATP and NADPH.
Which products of the light reactions are used by the Calvin Cycle?
ATP and NADPH
Where is the pigment chlorophyll stored in a chloroplast?
Thylakoid
Write the balanced chemical equation for photosynthesis using chemical formulas.
6CO2+6H2O+light→C6H12O6+6O2
Describe how increasing CO₂ concentration typically affects the rate of photosynthesis
increases the rate of photosynthesis
Explain, in one sentence, how light intensity affects the rate of the light reactions until pigments are saturated.
As light intensity increases, the rate of the light reactions increases until all pigment molecules and reaction centers are saturated and cannot use additional light.
Describe the overall role of the Calvin Cycle in converting inorganic carbon into organic molecules, in two to three sentences.
The Calvin Cycle uses ATP and NADPH (from the light reactions) and CO2CO2 to build sugar molecules. Carbon atoms from CO2CO2 are fixed into organic compounds through a series of enzyme-catalyzed steps in the stroma
List the six chloroplast parts mentioned in the notes
Outer membrane, inner membrane, intermembrane space, grana (stacks of thylakoids), thylakoid, stroma
Explain the roles of water and carbon dioxide in the chemical equation: which provides electrons and protons, and which provides carbon atoms for sugar formation?
Water provides electrons (hydrogen) during photolysis in the light reactions; carbon dioxide provides the carbon atoms that are fixed into organic molecules (sugars) during the Calvin Cycle.
why photosynthesis rates level off at very high light intensities even when more light is available
. At high light intensities, pigments and reaction centers become saturated — there are no additional reaction centers or available electron carriers to use extra light — so the rate levels off.