What Is the Function of Chloroplasts?

Dr. phil.nat Thomas Geier, Fachgebiet Botanik der Forschungsanstalt Geisenheim/CC-BY-SA 3.0

Chloroplasts are organelles that help plants convert water, energy and sunlight into food. Chloroplasts support photosynthesis by storing energy and synthesizing metabolic materials.

Chloroplasts exist in all green parts of plants, but they are most highly concentrated in the leaves. Chloroplasts belong to a group of cells called plastids, which store energy and help plants convert light energy into food. Chloroplasts contain pigmentation in the forms of chlorophyll a and chlorophyll b, which help absorb light that photosynthesis needs in order to occur. Chlorophyll is also responsible for making plants green.

Chloroplast Structure

Chloroplasts are structured in an ellipsoid shape. They contain a double membrane, which has two layers that serve different functions. The outer layer of the membrane helps protect the chloroplast from harm and it is more permeable than the inner layer. The inner layer contains a large concentration of transport proteins. The two membrane layers are separated by an intermembrane space. The membrane surrounds the stroma, which is a thick, fluid-like substance that dissolves enzymes. The stroma is the most voluminous component of a chloroplast. The stroma contains deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). In higher plant species, chloroplasts also have a structure called lamellae. Lamellae are internal membranes that have granums, or stacks, of hollow disks called thylakoids. Thylakoids are found throughout the stroma and connected to each other through lumens, which are their internal spaces.

Chloroplasts and Mitochondria

Chloroplasts work in conjunction with mitochondria, which is the other organelle required for photosynthesis. While chloroplasts create energy, mitochondria aid in plant respiration. Chloroplasts and mitochondria are both unique from other cell structures because they contain their own DNA and can function independently of their parent cell.


Photosynthesis is one of the most important processes that plants undertake. To carry out photosynthesis, plants need water, carbon dioxide and sunlight. The process of photosynthesis begins when the plant draws water and minerals up from the ground through its roots. Next, the leaves absorb carbon dioxide from the air, which enters into their system by tiny pores in their leaves, stems, branches, flowers and roots. This process produces oxygen, which plants release into the air. Lastly, they draw energy from the sun into chloroplasts, which gives chloroplasts energy. During the process of photosynthesis, plants produce sugar and oxygen.

Plants often have adaptations to their specific environments to make sure that they can carry out photosynthesis. Root systems are one type of adaptation. Desert plants, for instance, have a different type of root system than trees and plants that grow in a tropical environment. While most plants absorb water through their roots for photosynthesis, others have unique structures that help them collect water.

Through photosynthesis, plants produce the fuel that they need to grow and develop. Photosynthesis plays an important role of many plant functions, including proper growth. In addition to plants, some algae and bacteria also use photosynthesis. Photosynthesis helps organisms mature, and it plays a role in the greater cycle of life on Earth. Other organisms that consume plants for food ultimately rely on photosynthesis for survival. Photosynthesis also played a role in the development of the world’s fossil fuels, which derive from ancient plants.