(D) In plants, glucose is derived from sucrose, which is the end product of photosynthesis or from storage carbohydrates. Sucrose is converted into glucose and fructose by the enzyme invertase.

leaf chloroplasts

Glucose molecules are also made into sugars found in fruits such as grapes and apples. As plants assemble glucose molecules into cellulose, starches, and sugars, plants create the material out of which they themselves are made. Glucose produced by plants becomes the fuel that powers all kinds of living things.

Sucrose is the end product of photosynthesis and the primary sugar transported in the phloem of most plants.

All green plants produce sugars through photosynthesis, a natural process that turns sunlight into energy. These include glucose and fructose, which are converted by the plant into sucrose.

Glucose

Glucose in Photosynthesis Photosynthesis in plants occurs when a plant gets its energy from light, typically sunlight. Using water and carbon dioxide taken in from the surrounding air, a plant is able to convert these molecules into glucose and oxygen. Glucose, which is actually a sugar, feeds the plant.

Plants use the energy of the sun to change water and carbon dioxide into a sugar called glucose. Glucose is used by plants for energy and to make other substances like cellulose and starch. Starch is stored in seeds and other plant parts as a food source.

The sugar produced by photosynthesis can be converted into the sugar glucose. Thousands of glucose molecules can be linked together to form the complex carbohydrate cellulose. Cellulose is a very tough molecule that is used to build the cell wall of plant cells.

In glycolysis, glucose is converted into pyruvate; in gluconeogenesis, pyruvate is converted into glucose.

Fatty acids and ketogenic amino acids cannot be used to synthesize glucose. The transition reaction is a one-way reaction, meaning that acetyl-CoA cannot be converted back to pyruvate. As a result, fatty acids can’t be used to synthesize glucose, because beta-oxidation produces acetyl-CoA.

Insulin deficiency results in an increase in glycogenolysis and thus an increase in hepatic glycolytic intermediates, including F2,6P2, which leads to increased glycolysis and hepatic lactate output as well as an inhibition of gluconeogenic flux to G6P (7,8).

pyruvate

A ketogenic diet prevents the need for excess gluconeogenesis, since this would require a lot of extra energy. Remember, producing a single glucose molecule from pyruvate requires six ATP molecules. In addition, ketones generate more energy (ATP) per gram than glucose.

However, with insulin deficiency, gluconeogenesis proceeds rapidly and contributes to an elevated blood glucose level. With adequate insulin, the blood glucose response in persons with diabetes would be expected to be similar to the blood glucose response in persons without diabetes.

Gluconeogenesis: Brain needs glucose as its main energy fuel. When carbohydrate sources and intermediary metabolites are depleted amino acids are used for the synthesis of glucose (gluconeogenesis). Skeletal muscle is the major source due to its large mass, but proteins from all other tissues are also utilized.

Excess glucose is polymerized to form glycogen, which is stored in the liver and muscles as a reserve.