Biology Nutrition and Digestion

This document provides an overview of lipids, carbohydrates, and proteins in biology nutrition and digestion. It discusses the structure and functions of phospholipids, cholesterol, fatty acids, monosaccharides, disaccharides, and polysaccharides. It also explains the formation of glycosidic and peptide bonds, as well as the four levels of protein structures. Additionally, it covers biochemical tests for lipids, starch, reducing sugars, and proteins.

Running Head: Biology Nutrition and Digestion 1
Understand lipids, carbohydrates, and proteins
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Biology Nutrition and Digestion 2
2.0 Understand lipids, carbohydrates, and proteins
2.1 Structure and functions of phospholipids and cholesterol and structural differences between
saturated, mono-unsaturated and polyunsaturated fatty acids
Phospholipids are mainly found in the cell membrane. They are made up of a glycerol molecule,
a phosphate group, and two fatty acids. Structurally, a phospholipid is made up of two
hydrophilic fatty acids tails and a hydrophobic phosphate group head (Tanaka, Fujimura-
Kamada, and Yamamoto, 2010). On the other hand, cholesterol which consists of four
hydrocarbons attached to form a large steroid structure helps in membrane fluidity in animals.
Saturated fatty acids are straight hydrocarbon chains saturated with hydrogen. They contain 12-
22 carbon atoms. Unsaturated fatty acids are made up of 16-22 carbon chains and have a double
bond found in different positions. Polyunsaturated fatty acids are long hydrocarbon chains with a
double bond between the third and fourth carbon and a methylene group between the double
bonds (Mozaffarian, Micha and Wallace, 2010).
2.2 Glycosidic bond formation and the structure and functions of monosaccharide, disaccharides
and polysaccharides
Glycoside bond is a covalent bond formed between a molecule from a saccharide and a hydroxyl
group from a compound like alcohol through condensation reaction (Leemhuis, Pijning,
Dobruchowska, Dijkstra, & Dijkhuizen, 2012). Depending on monosaccharaides present there
are three forms which include, Monosaccharide which has one polyhydroxy aldehyde unit,
whereas Disaccharides has two monosaccharide units joined together through a covalent bond
like sucrose and Oligosaccharide has 3 and ten monosaccharide units like farinose. A

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monosaccharide is mainly used as the source of energy among living things; disaccharides play
an essential role in the human diet as they are digested and broken down into two distinct sugar
molecules that are absorbed through the small intestines. Polysaccharides perform two main
characters which include offering structural support and energy storage (Van Bueren, Mulder,
Van Leeuwen, and Dijkhuizen, 2017).
2.3 Peptide bond formation and the four levels of protein structures
The peptide bond is a CO-NH bond made from a carboxyl group of one amino acid with an
amino group from the other amino acid whereby a water molecule is released. Four protein
structures are the primary structure which is the simplest level that consists of a sequence of
amino acids which is regulated by genes. Secondary structure is made up of consistent, repeated
coiling and folding of polypeptide support held together by hydrogen bonds. Tertiary structure-
consists of uneven contortions of proteins. And Quaternary structure results from interactions
between many polysaccharides in one protein (Galvao, Nunes, Lopes, H.S. and Moscato, 2012).
2.4 Biochemical tests for lipids, starch, reducing sugars sand proteins
Lipid tests include ethanol test and Sudan stain test which colors lipids red though it's a less
common bench reagent as compared to ethanol. Protein is tested using test 3-biuret test which
shows the presence of peptide bond within proteins. Iodine test checks the presence of starch
through adding solution checking for color change wherein search iodine turns black or

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blue.Reducing sugars are affirmed if aldehydes oxidases to acids forming a cuprous oxide which
forms a red precipitate.

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References
Galvao, L.C., Nunes, L.F., Lopes, H.S. and Moscato, P., 2012, October. A new greedy heuristic
for 3DHP protein struture prediction with side chain. In 2012 IEEE International Conference on
Bioinformatics and Biomedicine Workshops. IEEE. (pp. 77-81)
Leemhuis, H., Pijning, T., Dobruchowska, J.M., Dijkstra, B.W. and Dijkhuizen, L., 2012.
Glycosidic bond specificity of glucansucrases: on the role of acceptor substrate binding
residues. Biocatalysis and Biotransformation, 30(3), 366-376.
Mozaffarian, D., Micha, R. and Wallace, S., 2010. Effects on coronary heart disease of
increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of
randomized controlled trials. PLoS medicine, 7(3),. doi: 10.1371/journal.pmed.1000252
Tanaka, K., Fujimura-Kamada, K. and Yamamoto, T., 2010. Functions of phospholipid
flippases. The Journal of Biochemistry, 149(2),131-143
Van Bueren, A.L., Mulder, M., Van Leeuwen, S. and Dijkhuizen, L., 2017. Prebiotic human gut
symbiont Bacteroides thetaiotaomicron. Scientific reports, 7, Article number: 40478.