What is Photosynthesis?

The word photosynthesis is made up of two parts. Photo means light and synthesis means to put things together. So, photosynthesis is the process by which a plant uses light energy to combine compounds and produce sugars.

Photosynthesis takes place inside plant cells, in small structures called chloroplasts.

Chloroplasts contain a green pigment called chlorophyll. As the plant undergoes photosynthesis, the chlorophyll absorbs sunlight and uses it to convert carbon dioxide and water into glucose and oxygen.

The word equation for photosynthesis is:

Carbon Dioxide + Water Glucose + Oxygen

In other words, carbon dioxide reacts with water to form glucose and oxygen.

To carry out photosynthesis, plants absorb carbon dioxide from the air through their leaves and water through their roots. Photosynthesis can only occur in the presence of light because light is the source of energy, which comes from the Sun.

The oxygen produced is released into the air through the leaves, where it is used by both plants and animals for respiration.

Photosynthesis helps to maintain carbon dioxide and oxygen levels in the atmosphere. This is because plants absorb carbon dioxide and release oxygen. Photosynthesis is also important for the Earth’s ecosystem because it provides a source of food for animals

Not all plant cells carry out photosynthesis, as it requires the presence of chloroplasts. Chloroplasts are found in the cells of the leaves, stems, and flowers of plants, but not in all plant cells.

  • For example, root hair cells, which are specialised cells found in the roots of plants, do not contain chloroplasts. This is because they are underground and do not have access to sunlight. As a result, they are not able to carry out photosynthesis.

Adaptations of Leaves for Photosynthesis

Leaves have many adaptations that help them to carry out photosynthesis efficiently. The main adaptations of the leaf are shown in the table below.

Broad leavesProvides a large surface area, which allows them to absorb more sunlight and take in more carbon dioxide.
Thin structureProvide a shorter distance for gases, such as oxygen and carbon dioxide, to diffuse in and out of the cells.

As a result, gases are able to diffuse in and out of the cells more quickly.
Xylem and phloem tubesXylem and phloem tubes transport water and nutrients from the roots to the leaves and help to support the structure of the leaf.
ChlorophyllHelps them to absorb sunlight and carry out photosynthesis.
StomataLeaves have tiny holes called stomata, which allow them to take in carbon dioxide and release oxygen.

These adaptations enable leaves to absorb sunlight and carbon dioxide efficiently, both of which are essential for photosynthesis.

Uses of Glucose

Glucose is a type of sugar that is produced by plants during photosynthesis and is an important source of energy. It can be bonded together in different ways to form different carbohydrates, such as cellulose, glycogen, and starch.

The uses of glucose include:

  • Starch is a complex carbohydrate that is made up of long chains of glucose molecules. It is found in many plant-based foods, such as grains, potatoes, and legumes, and is an important source of energy for the body. When it is needed for energy, starch can be converted back into glucose.
  • Cellulose is a complex carbohydrate that is made up of long chains of glucose molecules. It is the main structural component of plant cell walls and is indigestible by humans.
  • Amino acids are the building blocks of proteins. To make proteins, the plant requires a range of different amino acids. It also needs mineral ions from the soil, such as nitrate ions. These ions are absorbed from the soil through the roots of plants.
  • Fats and oils are used by plants as a storage form of energy. They can also be converted into glucose, which allows plants to access stored energy when needed. Some plant oils are also used for medicinal purposes.