Introduction to Photosynthesis

Introduction to Photosynthesis

Middle School

​

Learning Objectives

• Define photosynthesis and identify its reactants and products.

• Explain how photosynthesis converts radiant energy into chemical energy.

• Trace how photosynthesis cycles matter from CO₂ and H₂O into sugar.

• Write and interpret the chemical equation for photosynthesis.

Key Vocabulary

​

Photosynthesis

The process plants use to convert light energy from the sun into chemical energy.

​

Radiant Energy

Radiant energy is energy that comes from the sun and travels in electromagnetic waves.

​

Chemical Energy

This is a form of potential energy that is stored in the bonds of molecules.

​

Glucose

Glucose (C₆H₁₂O₆) is a simple sugar molecule that stores chemical energy for cells.

​

Organic Molecules

These are complex molecules primarily based on carbon atoms, such as glucose and proteins.

​

Reactants

Reactants are the essential starting ingredients that are consumed during a chemical reaction to form products.

Key Vocabulary

​

Products

The new substances that are formed as the result of a chemical reaction.

​

Energy Flow

The one-way movement of energy through the different feeding levels within an ecosystem.

​

Cycling of Matter

The continuous movement and reuse of essential atoms and molecules within Earth's systems.

​

Cellular Respiration

The process in cells that releases energy from food by reacting it with oxygen.

​

​

What is Photosynthesis?

• Plants, algae, and some microorganisms make their own food through photosynthesis.

• This process changes the sun's radiant energy into stored chemical energy.

• The chemical energy is stored in a sugar called glucose.

• Energy flows to other organisms when they eat the plant.

​

Multiple Choice

What is the primary purpose of photosynthesis?

• To help plants make their own food.

• To release water into the atmosphere.

• To provide shade for small animals.

• To break down dead organisms in the soil.

Multiple Choice

During photosynthesis, how is the sun's energy transformed and stored?

• It is converted into chemical energy stored in glucose.

• It is changed into heat energy to keep the plant warm.

• It becomes light energy that the plant reflects.

• It is stored as kinetic energy in the plant's leaves.

Multiple Choice

What would be the most likely consequence for other organisms if photosynthesis suddenly stopped?

• The flow of energy to organisms that eat plants would be disrupted.

• Animals would learn to make their own food.

• The sun would stop providing radiant energy.

• Plants would start storing energy as heat instead of glucose.

The Recipe for Photosynthesis

• Plants use carbon dioxide (CO₂) and water (H₂O) as ingredients.

• Atoms rearrange to create glucose (C₆H₁₂O₆) and oxygen (O₂).

• This reaction shows how matter is conserved and cycled in an ecosystem.

Multiple Choice

What are the necessary ingredients for photosynthesis to occur?

• Carbon dioxide and water

• Glucose and oxygen

• Sunlight and soil

• Water and sugar

Multiple Choice

What happens to the atoms of carbon dioxide and water during photosynthesis?

• They are rearranged to form new substances like glucose and oxygen.

• They are destroyed and converted into energy for the plant.

• They are combined with sunlight to create a new type of atom.

• They are released by the plant as waste without changing.

Multiple Choice

Which statement best explains how photosynthesis demonstrates the conservation of matter?

• The total number of atoms in the ingredients (CO₂ and H₂O) equals the total number of atoms in the products (glucose and O₂).

• The amount of glucose produced is always greater than the amount of water used.

• The plant creates new atoms of carbon and oxygen to make food.

• Energy is conserved, but matter is lost during the reaction.

​

​

Photosynthesis and Life on Earth

• Photosynthesis captures matter and energy, forming the base of most food webs.

• Animals get energy by eating plants or other animals that eat plants.

• It releases oxygen, which most organisms need for cellular respiration.

Multiple Choice

What is the primary role of photosynthesis in supporting life on Earth?

• It provides the essential matter and energy that forms the base of most food webs.

• It helps animals find shelter in different environments.

• It causes the water cycle to move water around the planet.

• It absorbs oxygen from the atmosphere for plants to use.

Multiple Choice

What is the relationship between photosynthesis and how animals get matter for growth?

• Animals get energy and matter by eating the organisms that perform photosynthesis.

• Animals absorb energy directly from the sun in the same way plants do.

• Photosynthesis creates water, which animals drink to get energy.

• Photosynthesis removes harmful gases from the air that animals breathe.

Multiple Choice

If a global event caused all photosynthesis to stop, what would be the most likely outcome for life on Earth?

• Food webs would collapse, and the air would contain less oxygen.

• Animals would quickly adapt to perform photosynthesis themselves.

• The amount of energy available to animals would increase.

• Animals would find a new way to produce oxygen for respiration.

​

​

How Organisms Use Food

• Glucose from photosynthesis is used for energy and growth.

• This energy is released through a process called cellular respiration.

• In cellular respiration, glucose and oxygen react to release energy.

• Food atoms are rearranged to support the organism's growth and repair.

Multiple Choice

What is the primary purpose of cellular respiration in an organism?

• To release stored chemical energy for the organism's activities

• To create new atoms for the organism to use

• To remove all waste products from the organism's cells

• To convert energy into matter for storage

Multiple Choice

Besides being used for energy, what is another essential function of the atoms from food?

• They are destroyed to release energy.

• They are converted directly into pure energy.

• They are used to build and repair body structures.

• They are stored as oxygen for later use.

Multiple Choice

Which statement best explains what happens to the atoms from a glucose molecule after an organism consumes it?

• The atoms are rearranged to provide energy and build the body, but the total amount of matter is conserved.

• Some of the atoms are converted into energy and disappear completely.

• All atoms from the food are used to build new body parts, with none used for energy.

• The organism creates new atoms to grow larger after consuming the food.

​

​

Biofuels from Photosynthesis

• Scientists study cyanobacteria to produce compounds for biofuels to power vehicles.

• Biofuels are already produced today from plants like corn and sugarcane.

• However, this process is very expensive and requires large quantities of water.

• Each cell produces a small amount, so the goal is reducing costs.

​

Multiple Choice

What is the main purpose of using organisms like cyanobacteria, corn, and sugarcane in the process described?

• To create fuel to power vehicles

• To find new sources of water

• To produce more food for a growing population

• To reduce the amount of photosynthesis in plants

Multiple Choice

What is a major challenge associated with the current method of producing biofuels from plants like corn and sugarcane?

• The process is costly and requires a large amount of water.

• The fuels produced do not work in most vehicles.

• The plants grow too quickly to be harvested effectively.

• The process creates more pollution than it saves.

Multiple Choice

Scientists want to make the production of biofuels more affordable. Based on the information, which approach would best help them achieve this goal?

• To find a way to increase the amount of biofuel each cell can produce.

• To focus only on using sugarcane, since it is the most common.

• To decrease the amount of water given to the cyanobacteria.

• To build more expensive processing plants to reduce water.

​

Common Misconceptions

Misconception	Correction
Plants get their food from the soil.	Plants create their own food (glucose) via photosynthesis. Soil provides water and nutrients.
Photosynthesis and respiration are the same.	Photosynthesis stores energy in food. Cellular respiration releases energy from food.
Food is 'burned up' and disappears when used for energy.	The atoms in food are conserved and rearranged into new molecules.
The only purpose of photosynthesis is to make oxygen.	The primary purpose is to create food (glucose) for the plant. Oxygen is a byproduct.

​

Summary

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4