Photosynthesis Basics
Chlorophyll
In which organelle of a plant cell does photosynthesis occur?
The chloroplast
Name the 3 main inputs needed for photosynthesis.
Light energy, carbon dioxide, and water.
Which stage of photosynthesis requires light energy?
The light-dependent reactions.
What h=gas from the atmosphere is a major reactant in photosynthesis?
Carbon Dioxide (CO2)
Why is photosynthesis important to organisms that cannot make their own food?
Photosynthesis produces glucose that can serve as an energy-rich source, providing chemical energy to organisms through food chains.
What tiny openings in the plant leaves allow carbon dioxide to enter and oxygen to leave?
Stomata
What are the 2 main products of photosynthesis?
Glucose and oxygen.
Where do the light-dependent reactions occur?
In the thylakoid membranes of the chloroplast.
What gas is released into the atmosphere as a product of photosythesis?
Oxygen (O2)
What is the main purpose of photosynthesis? (What does the process actually do?)
Convert light energy into chemical energy stored in glucose.
What are thylakoids, and where are they found?
Thylakoids are flattened membrane sacs found inside the chloroplast. They contain chlorophyll and are the site of the light-dependent reactions.
Where does a plant get the carbon dioxide needed for photosynthesis?
From the atmosphere. Carbon dioxide enters the leaf trough the stomata.
Where doe the Calvin cycle occur?
In the stroma of the chloroplast.
Why do plants need sunlight for photosynthesis?
A student says, "Plants get the carbon they need to make gluscose from the soil." Is the student correct? Explain why or why not.
No. The carbon in glucose comes from carbon dioxide in the atmosphere. Carbon dioxide enters through the stomata and provide the carbon used to build glucose.
What is the difference between the granum and the stroma of a chloroplast?
A granum is a stack of thylakoids, while the stroma is a fluid-filled region surrounding the thylakoids.
Where does the oxygen released during photosynthesis come from?
The oxygen comes from water molecules that are split during the light-dependent reactions.
What is the main job of the Calvin cycle?
It uses carbon dioxide and energy from the light-dependent reactions to build molecules that can ultimately form Glucose.
A plant's stomata close during extreme drought. How could this affect photosynthesis?
Less CO2 would be able to enter the leaf, limiting the Calvin cycle and reducing the plant's ability to produce glucose.
A plant is placed in complete darkness for several days. Which part of the photosynthesis process would be most directly affected, and why?
The light-dependent reactions would be directly affected because they require light energy to excite chlorophyll's electrons and drive the reactions.
A scientist removes the thylakoid membrane from a chloroplast but leaves the stroma intact. Which major part of photosynthesis would be directly disrupted?
The light-dependent reactions would be disrupted because they occur in the thylakoids membrane, where chlorophyll captures light energy and water is split.
Consider the simplified photosynthesis equation:
6 CO2 + 6 H2O -> C6H1206 = 6 O2
A student claims that the oxygen gas released by the plant comes directly from the CO2 molecules. Is this correct?
No. The oxygen gas released during the light-dependent reactions comes from the splitting of water molecules.
A plant has plenty of carbon dioxide and water, but its chlorophyll cannot absorb light energy. Predict what would happen to the 2 major stages of photosynthesis.
The light-dependent reactions would be unable to function normally because they require captured light energy. As a result, the Calvin cycle would be greatly reduced because it depends on the energy produced by the light-dependent reactions.
Imagine 2 identical plants. Plant A receives plenty of light, CO2, and water. Plant B receives plenty of light and water but very little CO2. Which plant would likely photosynthesize as a higher rate? Explain why.
Plant A. Photosynthesis depends on several necessary inputs, including CO2. Because Plant B has limited CO2, carbon fixation and glucose production would be limited even though it has enough light and water.