Why do Plants Store Glucose as Starch?

Why do Plants Store Glucose as Starch?

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If you want to look at some incredible information about how plants function, you must read on. Now everyone knows that chlorophyll absorbs light energy in the chloroplasts. This energy is used to turn carbon dioxide from the atmosphere and water from the soil into the simple Glucose and oxygen.

The question arises here, what do plants use Glucose for? The answer is simple for respiration, making fruits, cell walls, proteins, store in seeds, and stored in the form of starch. But you know that plants store Glucose in the form of starch in their roots, stem, and leaves to use it when the photosynthesis process isn’t happening. Why is that so?

Starch in plants is the desired form of glucose storage because of the following reasons.

  1. Starch is a polysaccharide, unlike Glucose, which is too water-soluble. Storing in insoluble form prevents unexpected loss of Glucose through any discharges.
  2. If Glucose is stored inside the cells without polymerization, then the cell’s hypertonicity increases, causing the osmosis of water into the cell, sooner or later leading to the cell’s lysis as a result osmotic pressure.

Therefore, it is advantageous to keep Glucose in starch; it is vital.

The plants store Glucose in the form of starch. Starch is a polysaccharide. The leaves of a plant make Glucose, or you call it simple sugar, during photosynthesis. Photosynthesis occurs in light, such as when the sun is shining. The solar light is used to make energy for the plant. 

When plants are making sugar (for fuel, energy) on a sunny day, they save some of it as starch. When the simple sugars need to be retrieved for use, the starch is broken down into smaller components. The plants keep some energy in the form of starch for a wet day!

The rest of the article answers many vital questions about why do plants store starch? Let’s have a look at that.

Why do plants store starch and not Glucose?

Let’s find out what starch is and how the whole phenomenon works.

Plant photosynthesis is a complex process that involves carbon dioxide, water, and sunlight, facilitated by multiple enzymes to create the primary sugar known as Glucose. Much of the glucose plants produce straight away metabolized into different energy types that plants use to grow and reproduce. 

The portions of Glucose that are not converted to energy are converted to complex sugar compounds, referred to as starches. These are produced after the photosynthesis cycle. Plants then store starches for future energy needs or use them to construct new tissues.


Plants need the energy to grow, and for that matter, plants store starches in various ways. Starch molecules are huge when in contrast to other simple molecules, often containing heaps of bonded sugars. As carried out in plant cells, the photosynthesis process requires two distinct processes: light-based and light-independent reactions. 

Both most happen for Glucose to be synthesized. Thus, plants build starches solely after the metabolic procedures of photosynthesis. Enzymes bond glucose units into more complex sugars that form starches.

Storing Starches

Plants create, use, and store starches for many purposes, but the two primary ones are cellulose synthesis and energy storage. Cellulose is the main thing of plant cell walls, supplying structural help, and preventing cell damage. Many ruminant animals, like cows, goats, and sheep, have developed mechanisms for digesting cellulose. 

Humans cannot digest cellulose. We need to consume the starches stored in grains, cereals, fruit, and vegetable tissues. These starches are the ones stored by plants for cell energy and reproduction.

The plants use a metabolic pathway to create starches, and this process is regarded as a reversible process. A specific set of enzymes is used to break down starches for cellular energy than to create them from Glucose, but the operations can be considered mirror images.

If a plant no longer has adequate daylight to photosynthesize its needed energy – such as on cloudy days or at night time – it will metabolize starches to produce the Glucose it needs. So that it continues producing energy until it can synthesize Glucose using daylight again.

So, after understanding all this, we can now quickly answer the question as

Glucose is soluble. If only Glucose was stored in the plant cells, it could affect how water flows in and out of the cells by osmosis, affecting the concentration gradient of solutes. 

Starch is a polysaccharide insoluble in water, so it won’t affect how water goes in and out of the plant, meaning plants can store massive starch quantities in their cells. Starch molecules are enormous, so they can’t go out of the cell. This capability can act as energy stores. They can be transformed back to Glucose needed to be used in respiration or other processes.

Does that suggest that there is no glucose in starch?

The answer to this question is simple

Plant starch begins as Glucose, a principal product of photosynthesis; Glucose is transformed into a polymerization starch process. There are two varieties of starches: amylose and amylopectin. 

Both are similar in structure, but amylose is linear, and amylopectin is branched. Plants keep these starches in granules known as plastids inside plant cells. So that means starch is a chain of glucose molecules that are bonded together.

Does starch have more energy than Glucose?

Starches are the primary energy source and are complicated carbohydrates that take an extended duration of time to break down. Think of starch as a time-release kind of energy. When you consume starchy foods, you will have a sustained energy level for several hours. 

This is different from sugars, which are simple carbohydrates that give you a quick surge of energy; however, do nothing to keep your energy levels going. So, does that mean starch has more energy than Glucose?

Starches include 300 to 1,000 glucose units stuck together in a lengthy chain. If you hold a starch in your mouth, enzymes in saliva will begin to break it down. Because starches contain many bonds, they digest and absorb much more slowly than simple sugars. Because they digest slowly, they stabilize blood sugar levels and do not cause the unexpected rises that can occur if you consume a meal high in simple sugars.

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