7th Grade Unit 2 Test

What is the primary function of photosynthesis in plants?

• To produce oxygen

• To convert sunlight into chemical energy

• To absorb water

• To release carbon dioxide

Answer explanation

The primary function of photosynthesis is to convert sunlight into chemical energy, which plants use to grow and thrive. While oxygen is produced as a byproduct, the main goal is energy conversion.

Which of the following is a product of photosynthesis?

• Carbon dioxide

• Water

• Glucose

• Nitrogen

Answer explanation

Glucose is the main product of photosynthesis, where plants convert carbon dioxide and water into glucose using sunlight. Carbon dioxide and water are reactants, not products, while nitrogen is unrelated to this process.

Describe the role of chlorophyll in photosynthesis.

• It absorbs sunlight

• It releases oxygen

• It stores glucose

• It transports water

Answer explanation

Chlorophyll plays a crucial role in photosynthesis by absorbing sunlight, which provides the energy needed for plants to convert carbon dioxide and water into glucose and oxygen.

Which molecule is primarily responsible for capturing light energy in photosynthesis?

• Glucose

• Chlorophyll

• Oxygen

• Carbon dioxide

Answer explanation

Chlorophyll is the primary pigment in plants that captures light energy during photosynthesis, enabling the conversion of light into chemical energy. Glucose, oxygen, and carbon dioxide play other roles in the process.

Explain how photosynthesis contributes to the flow of energy in an ecosystem.

• It releases energy stored in glucose

• It converts solar energy into chemical energy

• It absorbs energy from the soil

• It stores energy in the form of ATP

Answer explanation

Photosynthesis converts solar energy into chemical energy stored in glucose, which is essential for the flow of energy in an ecosystem. This process supports life by providing energy for plants and, subsequently, for herbivores and carnivores.

What is the chemical equation for photosynthesis?

• 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2

• C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O

• 6O_2 + C_6H_{12}O_6 \rightarrow 6CO_2 + 6H_2O

• 6H_2O + 6O_2 \rightarrow C_6H_{12}O_6 + 6CO_2

Answer explanation

The correct equation for photosynthesis shows that carbon dioxide (6CO2) and water (6H2O) are converted into glucose (C6H12O6) and oxygen (6O2) using sunlight, which is represented as 6CO2 + 6H2O → C6H12O6 + 6O2.

How does photosynthesis affect the levels of carbon dioxide in the atmosphere?

• It increases carbon dioxide levels

• It decreases carbon dioxide levels

• It has no effect on carbon dioxide levels

• It converts carbon dioxide into nitrogen

Answer explanation

Photosynthesis decreases carbon dioxide levels in the atmosphere by converting CO2 into glucose and oxygen. Plants absorb CO2 during this process, thus reducing its concentration in the air.

What is the main purpose of cellular respiration in organisms?

• To produce glucose

• To release energy from food

• To absorb sunlight

• To produce oxygen

Answer explanation

The main purpose of cellular respiration is to release energy from food. Organisms break down glucose and other nutrients to produce ATP, which is essential for various cellular processes.

Which of the following best describes a chemical reaction in cellular respiration?

• Glucose is broken down to release energy

• Water is converted into oxygen

• Sunlight is absorbed to produce glucose

• Carbon dioxide is converted into glucose

Answer explanation

The correct choice, 'Glucose is broken down to release energy', accurately describes cellular respiration, where glucose is metabolized to produce ATP, the energy currency of the cell.

Identify the main products of cellular respiration.

• Oxygen and glucose

• Carbon dioxide and water

• Glucose and water

• Oxygen and carbon dioxide

Answer explanation

The main products of cellular respiration are carbon dioxide and water, which are produced when glucose is broken down for energy. Oxygen is consumed in the process, but it is not a product.