Biology
Photosynthesis: a short lesson and practice questions
Study the inputs, structures, and stages of photosynthesis with six practice questions, explained answers, and common mistakes.
By StudyNova AI · Updated
Original teaching example prepared for this guide and checked against the references below. Cover the answer, try each question, then use the explanation to check your reasoning.
What you will practise
- Identify the inputs and products in a simplified description of photosynthesis.
- Distinguish a chloroplast from chlorophyll and locate the two major stages.
- Explain why the oxygen released during photosynthesis comes from water.
Source lesson
Photosynthesis converts light energy into chemical energy stored in organic molecules. In a simplified overall model, carbon dioxide and water are used to make carbohydrate, and oxygen is released. Plants, algae, and some bacteria carry out photosynthesis. This lesson focuses on the process in plant cells.
In plants, photosynthesis occurs in chloroplasts. Chlorophyll is a light-absorbing pigment; it is not the name of the organelle. The light-dependent reactions take place in the thylakoid membranes. They use light energy to help produce ATP and NADPH, and the splitting of water releases oxygen.
The Calvin cycle takes place in the stroma, the fluid around the thylakoids. It uses carbon dioxide along with ATP and NADPH from the light-dependent reactions to build a small carbohydrate called G3P. G3P can be used to form sugars. Calling this stage light-independent means that its reactions do not directly capture light; it does not mean that the plant performs it only at night.
Practice questions
1. Which pair supplies matter for the simplified overall photosynthesis model?
- Carbon dioxide and water
- Oxygen and light
- Chlorophyll and oxygen
- ATP and sunlight
Check the answer and explanation
Carbon dioxide and water.
Light supplies energy. Carbon dioxide and water supply matter in the overall model; light is not a material ingredient.
2. What is the difference between a chloroplast and chlorophyll?
Check the answer and explanation
A chloroplast is an organelle; chlorophyll is a pigment that absorbs light.
Keeping the structure and the pigment separate avoids confusing where photosynthesis happens with what captures light.
3. Where do the light-dependent reactions occur in a plant chloroplast?
Check the answer and explanation
In the thylakoid membranes.
The lesson separates the thylakoid membranes from the surrounding stroma, where the Calvin cycle occurs.
4. True or false: the oxygen released in the light-dependent reactions comes from splitting carbon dioxide.
Check the answer and explanation
False. It comes from splitting water.
Carbon dioxide contributes carbon during carbohydrate building. The released oxygen is associated with water splitting.
5. Which products link the light-dependent reactions to the Calvin cycle?
Check the answer and explanation
ATP and NADPH.
These carry energy and reducing power to the carbohydrate-building reactions. The two stages work together.
6. Why is 'the Calvin cycle happens only at night' an inaccurate statement?
Check the answer and explanation
It does not directly capture light, but it depends on ATP and NADPH supplied by the light-dependent reactions.
Light-independent describes the reaction mechanism. It is not a rule about the time of day.
Common mistakes to check
Sunlight is a type of matter that becomes plant mass.
Separate the energy source from material inputs. Light supplies energy; carbon dioxide supplies carbon for carbohydrate building.
Plants photosynthesize instead of carrying out cellular respiration.
Plants also carry out cellular respiration. This short lesson describes photosynthesis, not every process occurring in a plant.
References and further reading
The lesson and questions use original wording. Follow these references for a fuller explanation and check any wording your course uses differently.