Difference Between Grana and Stroma

Key Difference – Grana vs Stroma

Since Grana and Stroma are two unique structures ofChloroplasts, it is important to understand what is a chloroplast, before looking at the differences between grana and stroma. Chloroplasts are categorized underplastids, which occur as spherical or disc-like bodies in thecytoplasm的eukaryoticplant cells. The other two types of plastids are leucoplasts and chromoplasts. Chloroplasts are the most common plastids distributed homogenously in the cytoplasm ofplant cells. They are responsible for carrying outphotosynthesis, during which chloroplasts synthesize carbohydrates by converting the energy of the sunlight into chemical energy. Chloroplasts are double-membrane organelles and discoid in shape. They are made up of chloroplast membrane, grana, stroma, plastid DNA, thylakoids, and sub-organelles. Thekey differencebetween grana and stroma is,granarefers to the stacks of thylakoids embedded in the stroma of a chloroplastwhilestromarefers to thecolorless fluid surrounding the grana within the chloroplast.This article focuses on discussing the difference between grana and stroma in detail.

What are Grana?

Grana are embedded in the stroma of the chloroplast. Each granum consists of 5-25 disc-shaped thylakoids stacked one on the other resembling a stack of coins. Thylakoids are also called granum lamellae, which encloses a space known as a locus. Some of the thylakoids of a granum are connected with thylakoids of another granum via a thin membrane called stroma lamellae or fret membrane. Grana provide a large surface for the attachment ofChlorophylls, other photosynthetic pigments, electron carriers and enzymes to perform light dependent reaction of the photosynthesis. The photosynthetic pigments are attached to a network of proteins in a very precise manner forming photosystems, which enable the maximum light absorption. The ATP synthase enzymes attach to granal membranes help to synthesize ATP molecules bychemiosmosis.

What is Stroma?

The stroma is a fluid-filled matrix within the inner membrane of the chloroplast. The fluid is a colorlesshydrophilicmatrix housing DNA,ribosomes,enzymes,oil droplets and starch grains. The light-independent stage of photosynthesis (reduction of carbon dioxide) takes place in the stroma. The grana are surrounded by the stromal fluid so that products of the light dependent reaction can rapidly pass into the stroma via granal membranes.

What is the difference between Grana and Stroma?

Definition ofGrana and Stroma:

Grana:The grana refers to the stacks of thylakoids embedded in the stroma of a chloroplast.

Stroma:The stroma refers to the fluid-filled matrix inside the inner membrane of the chloroplast.

Grana vs Stroma:

Structure:

Grana:Each granum consists of 5-25 disc-shaped thylakoids stacked one on the other resembling a stack of coins. Each has a diameter of 0.25 – 0.8 μ

Stroma:Fluid-filled matrix containing DNA, ribosomes, enzymes, oil droplets and starch grains.

Location:

Grana:It is found in the stroma.

Stroma:It is found within the within the inner membrane of the chloroplast.

Enzymes:

Grana:Grana contains enzymes needed for the dependent reaction of the photosynthesis and also ATP synthase enzymes needed for synthesizing ATP molecules bychemiosmosis.

Stroma:Stroma contains enzymes needed for the light-independent reaction of photosynthesis.

Functions:

Grana:They provide a large surface for the attachment of Chlorophylls, other photosynthetic pigments, electron carriers and enzymes, thus helping for photosynthesis.

Stroma:Stroma houses the sub-organelles of chloroplast and products of photosynthesis and also provides space for the light-independent reaction of photosynthesis.

Image Courtesy:

“Chloroplast II” by Kelvinsong – Own work.(CC BY 3.0)viaWikimedia Commons

“Granum”(CC BY-SA 3.0)viaWikimedia Commons

“Thylakoid”. (Public Domain) viaWikipedia