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Fat has a food energy content of 38 kilojoules per gram (9 kilocalories per gram) proteins and carbohydrates 17 kJ/g (4 kcal/g). [ 2 ] Water makes up a large proportion of the total mass ingested as part of a normal diet but it does not provide any nutritional value.
For example, the values for glucose, sucrose, and starch are 15.57, 16.48 and 17.48 kilojoules per gram (3.72, 3.94 and 4.18 kcal/g) respectively. The differing energy density of foods (fat, alcohols, carbohydrates and proteins) lies mainly in their varying proportions of carbon, hydrogen, and oxygen atoms.
The energy yield from a gram of fatty acids is approximately 9 kcal (37 kJ), much higher than the 4 kcal (17 kJ) for carbohydrates. Since the hydrocarbon portion of fatty acids is hydrophobic , these molecules can be stored in a relatively anhydrous (water-free) environment.
[56] [2]: 329–331 In plants and algae, the galactosyldiacylglycerols, [57] and sulfoquinovosyldiacylglycerol, [32] which lack a phosphate group, are important components of membranes of chloroplasts and related organelles and are among the most abundant lipids in photosynthetic tissues, including those of higher plants, algae and certain ...
The physiological caloric value of glucose, depending on the source, is 16.2 kilojoules per gram [107] or 15.7 kJ/g (3.74 kcal/g). [108] The high availability of carbohydrates from plant biomass has led to a variety of methods during evolution, especially in microorganisms, to utilize glucose for energy and carbon storage.
The unit is most commonly used to express food energy, namely the specific energy (energy per mass) of metabolizing different types of food. For example, fat (triglyceride lipids) contains 9 kilocalories per gram (kcal/g), while carbohydrates (sugar and starch) and protein contain approximately 4 kcal/g. [29] Alcohol in food contains 7 kcal/g. [30]
Amylopectin / ˌ æ m ɪ l oʊ ˈ p ɛ k t ɪ n / is a water-insoluble [1] [2] polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Relation of amylopectin to starch granule. Plants store starch within specialized organelles called amyloplasts. To ...
Other types of lipids found in the body are fatty acids and membrane lipids. Lipid metabolism is often considered the digestion and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. [ 5 ]