AP Biology : Understanding Photosynthesis, Light Reactions, and Calvin Cycle
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Example Questions
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Which of the following is not a reactant used in the process of photosynthesis?
H2O
Light energy
O2
CO2
O2
The process of photosynthesis can be summarized by the following equation.
H2O, CO2, and light energy are thus reactants of photosynthesis, while O2 is only a product.
Example Question #2 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
What are the products of photosynthesis?
Light and glucose
Carbon dioxide and light
Oxygen and carbon dioxide
Glucose and oxygen
Water and carbon dioxide
Glucose and oxygen
The photosynthesis equation can be written as:
From this equation, we can see that plants take in carbon dioxide, water, and light energy as reactants and produce glucose and oxygen as products.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Some organisms, such as green plants, are capable of obtaining energy directly from photosynthesis. These organisms are termed __________.
autotrophs
primary consumers
herbivores
heterotrophs
homotrophs
autotrophs
Autotrophs are organisms that produce complex organic compounds from substances present in the surroundings. These organisms may do this through the use of energy from light or from inorganic chemical reactions.
In contrast, heterotrophs require organic input in order to generate biological compounds and are unable to use light or inorganic materials for energy.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Which of the following is true of photosynthesis?
The process requires no energy
Carbon dioxide is oxidized
Carbon dioxide is reduced
Electrons decrease in potential energy as they move from water to sugar
Water is reduced
Carbon dioxide is reduced
Photosynthesis occurs in the chloroplasts of plant cells, where carbon dioxide is reduced and water is oxidized to create sugar. During this process electrons demonstrate increased potential energy as they move from water to sugar. The process requires an initial energy input, derived from photons.
Example Question #2 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
What is the first step in photosynthesis?
Light causes oxygen to pair with hydrogen, forming water for the plant
Photons present in light strike and excite electrons in chlorophyll
Light reduces sugars present in the plant cells to energized derivatives
Nutrients from the soil are turned into carbohydrates when combined with water
Water is split by chlorophyll
Photons present in light strike and excite electrons in chlorophyll
Photosynthesis begins with energy from light being converted to chemical energy. The only answer explanation accurately explaining this process describes the conversion of light energy (photons) to chemical energy (excited electrons).
Photons present in light strike and excite electrons in chlorophyll.
The photons are highly energized light particles, which strike chlorophyll and excite and free electrons in the chlorophyll molecule. These excited electrons pass through the electron transport chain and their energy is collected to make ATP.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Where does the Calvin Cycle take place?
Cytoplasm
Chloroplast outer membrane
Thylakoid membrane
Mitochondrial lumen
Stroma
Stroma
The Calvin Cycle (dark reactions) take place in the stroma of the chloroplasts, which is the aqueous space inside the organelle.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Organisms that make their organic molecules from inorganic raw materials obtained from the surrounding environment are called __________.
autotrophs
plants
auxotrophs
heterotrophs
autotrophs
Autotrophs create organic material from inorganic materials. Autotrophs are self-feeders in that they do not consume other organic materials but rather create their own organic materials. Plants and other photosynthetic organisms are examples of autotrophs.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Which of the following is a by-product of the light reactions in photosynthesis?
Sugar
Water
Carbon dioxide
Oxygen
Oxygen
During the light reactions water is split and the by-product is oxygen. Oxygen is then released back into the atmosphere. Sugars are produced during the Calvin cycle and are not a direct product of the light reactions.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Plants are an example of which of the following categories of organisms?
Heterotrophs
Biosphere consumers
Chemoautotrophs
Autotrophs
Autotrophs
Plants are an example of autotrophs. Autotrophs sustain themselves without consuming other organic material. Instead they create organic material from inorganic materials.
Example Question #1 : Understanding Photosynthesis, Light Reactions, And Calvin Cycle
Which of the following are referred to as the major sites of photosynthesis in most plants?
Roots
Stems
Leaves
Flowers
Leaves
The leaves are the major sites of photosynthesis in most plants. The chloroplasts are located in the mesophyll—interior tissues of the leaves—and are the primary sites of photosynthesis.
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