Difference Between Grana and Thylakoid

Main Difference – Grana vs Thylakoid

Grana and thylakoid are two structures in chloroplasts of plants. Chloroplasts are the organelles involved in the photosynthesis of plants. During photosynthesis, carbon dioxide and water are used to produce the simple sugar, glucose. The energy for the process is given by sunlight. This energy from sunlight is captured by special pigments called chlorophylls. Chlorophylls are found in the thylakoid membrane. Thylakoid is formed by enclosing of the thylakoid lumen from thylakoid membrane. Grana are found in the stroma of the chloroplast, which is connected by stroma thylakoids. The main difference between grana and thylakoid is that grana are the stacks of thylakoids whereas thylakoid is a membrane-bound compartment which is found in chloroplast.

This article looks at,

1. What are Grana
– Definition, Characteristics, Function
2. What is Thylakoid
– Definition, Characteristics, Function
3. What is the difference between Grana and Thylakoid

What are Grana

Grana are the stacks, which are formed by combining 2 to 100 thylakoids together. These grana are connected with each other by stromal thylakoids. Connecting each granum by stromal thylakoids allow the functioning of all grana as a unit during photosynthesis. The membranes of thylakoid and stromal thylakoid are responsible for the occurrence of light reaction of photosynthesis. The space between grana and inner membrane of the chloroplast is called stroma. Dark reaction of the photosynthesis occurs in the stroma of chloroplast. A single chloroplast contains 10 to 100 grana. Granum inside the chloroplast is shown in figure 1.

Figure 1: Granum in Chloroplast

What is Thylakoid

Thylakoid is the little, round, flat, pillow-shaped things inside the chloroplast. Thylakoid is a membrane-bound structure. The space between thylakoid membrane is called thylakoid lumen. The functional parts of the chloroplast are its membrane and the lumen. The light-trapping green pigment, chlorophyll is found in the thylakoid membrane, held by the membrane proteins. Chlorophylls are organized into photosystem 1 and photosystem 2 on the thylakoid membrane. The light energy of the sunlight is converted into electrical energy by chlorophyll. The electrical energy in the form of high energy electrons is passed through membrane proteins from one to another, providing the power to pump protons from stroma into thylakoid lumen. When these pumped proteins are rushed back into the stroma, energy is released, which is readily used by the enzyme, ATP synthase by synthesizing ATP. NADP+ reductase is the enzyme which uses electrons released from photosystem 2 for the production of NADPH. The produced ATP and NADPH can be used for the fixation of carbon dioxide into glucose. Membrane proteins in the thylakoid are shown in figure 2.

Figure 2: Thylakoid

Relationship

Grana: Grana are the stacks of thylakoids inside the chloroplast.

Thylakoid: Thylakoid is the pillow-shaped compartments in the chloroplast.

Function

Grana: Grana organize thylakoids together and connect them together by stromal thylakoids in order to allow the functioning of thylakoids as a unit.

Thylakoid: Thylakoid is involved in the light reaction of photosynthesis by producing ATP and NADPH.

Conclusion

Grana and thylakoid are two structures found inside the chloroplast, involved in the photosynthesis. Grana are the stacks of thylakoids. Around two to hundred thylakoids are organized into form a granum. Around ten to hundred grana are found inside a chloroplast. The light reaction of photosynthesis occurs on the thylakoid membrane with the aid of different membrane proteins on the membrane of thylakoid. Photosystem 1 and 2, ATP synthase and NADP+ reductase are some of the membrane proteins found in the thylakoid membrane, involved in the light reaction of photosynthesis. Grana organize thylakoid together in order to function as a unit, increasing the efficiency of photosynthesis. Grana connected are together by stromal thylakoids as well. However, the main difference between grana and thylakoid is their structures inside the chloroplast.

Reference:
1. “Biology Chloroplast Membranes – Shmoop Biology.” Shmoop. Shmoop University, 11 Nov. 2008. Web. 20 Apr. 2017.
2. Exploring photosynthesis in a leaf – Chloroplasts, Grana, Stroma, Thylakoids, and other parts of a leaf. N.p., n.d. Web. 20 Apr. 2017.

Image Courtesy:
1.”Thylakoid2″ (Public Domain) via Commons Wikimeida
2. “Thylakoid disc diagram”by BlueRidgeKitties (CC BY 2.0) via Flickr