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The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose.
Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and potentially aiding in defecation.
All polymers are made of repetitive units called monomers. Biopolymers often have a well-defined structure, though this is not a defining characteristic (example: lignocellulose): The exact chemical composition and the sequence in which these units are arranged is called the primary structure, in the case of proteins.
Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm. About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium ...
[2] [3] The majority of lipids found in the human body from ingesting food are triglycerides and cholesterol. [4] 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 ...
Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. [1] Poor nutrition is a chronic problem often linked to poverty, food security , or a poor understanding of nutritional requirements. [ 2 ]
Due to their hydrophobic nature, lipids and lipid digestive derivatives must be transported in the globular form within the cell, blood, and tissue spaces. The formation of a fat globule starts within the membrane bilayer of the endoplasmic reticulum. It starts as a bud and detaches from the ER membrane to join other droplets.
Other brush border enzymes are maltase, sucrase and lactase. Lactase is absent in some adult humans and, for them, lactose (a disaccharide), as well as most polysaccharides, is not digested in the small intestine. Some carbohydrates, such as cellulose, are not digested at all, despite being made of multiple glucose units. This is because the ...