Human Nutrition: Analyzing the Role of Nutrients and Digestion Process

This report details the structure and nutritional importance of carbohydrates, lipids, and proteins, the major macromolecules in the human diet, using a meal of fish and chips as an example. It explains that carbohydrates are a chief source of energy, composed of monosaccharides, disaccharides, and polysaccharides. Lipids, sourced from fats and oils, also provide energy and contribute to feelings of satiety. Proteins, made of amino acids, serve as building blocks for tissues and aid in infection resistance. The report further emphasizes the necessity of vitamins, minerals, fiber, and water for maintaining overall health, citing their roles in bone health, antioxidant activity, wound healing, energy metabolism, and digestive health. The analysis extends to the processes within the digestive tract, detailing how carbohydrates, proteins, and lipids are broken down and absorbed, highlighting the enzymatic actions in the mouth, stomach, and small intestine, as well as the absorption mechanisms in the intestinal villi.

Task 2
Structure and nutritional importance of Carbohydrates in human
The meal will have carbohydrate which is made of the basic units of simple sugars as shown in
Fig. 1. They are monosaccharides, disaccharides and polysaccharides. In human body,
carbohydrates are the chief source of energy. This will provide the energy to the man to perform
the activities of daily life. Monosaccharides are the simple sugars. For example, glucose and
fructose. These monosaccharides have exact molecular formula, C6H12O6, but their structure
varies.
Fig. 1 Structure of Simple Carbohydrate – Glucose (Source-Byjus)
Disaccharides have two units of monosaccharides such as sucrose. It is composed of two
monosaccharides, glucose and fructose which are connected together. Polysaccharides are made
of multiple units mono or disaccharides. Glycogen is a polysaccharide found in human body
which has many glucose molecules.

Structure and nutritional importance of Lipids in human
Lipids are the fats and oils which the man is getting from the fish and chips. Fatty acids and
glycerol are the basic units which made the large molecules, called lipid. Like in Fig. 2, three
sequence of carbon atoms are linked to one glycerol molecule, with its three carbon atoms to
compose a single lipid molecule. Lipids are also a source of energy and also provide the sense of
satisfaction after eating. So, lipids help in growth and energy of the body. The body stores the
excess fat in the abdomen and under the skin so that it can be used when required for more
energy (Nordqvist, 2017)
Fig. 2 Structure of Lipids (Source- Khan Academy)
Structure and nutritional importance of Proteins in human
Proteins are the large molecules which are made up of many chains of amino acids as shown in
20 different naturally-occurring amino acids are found but all the protein molecules have several

amino acid chains connected together in a different series and turned into an exact shape. Due to
unique sequences of amino acids and different shapes, all the proteins have their own set of
properties. Proteins will be used by the man as his body’s building blocks as they will build and
repair tissues. In addition, it will help in fighting infection.
Fig. 3 Structure of proteins (Science Daily)
Why a person also needs vitamins, minerals, fibre and water in the diet?
There are two types of Vitamins found in the human body, water-soluble (8 B vitamins and
vitamin C) and fat-soluble (A, D, E, and K) (NHS, 2017). Vitamin D assists in regulation of level
of calcium and phosphate in the body responsible for bone and teeth health. Vitamin E acts as a
strong antioxidant which will assist in repairing the damaged cells and strengthening the immune
system. Vitamin K helps in the process of keeping the bones healthy and blood clotting.
Vitamin C safeguard the cells, maintain healthy connective tissue and helps in healing of
wounds. Vitamin B1 is involved in supporting other vitamins in breaking down and releasing

energy and maintaining a healthy nervous system. Vitamin B2 and B3 keeps the skin, eyes and
nervous system healthy and release energy from the food eaten by the man. Vitamin B6 assists
the body in using and depositing the energy from protein and carbohydrates in fish and chips.
Vitamin B7 assist in the metabolisation of the fat. Vitamin B12 assists in developing RBCs.
Fibres in the diet will prevent stomach or intestinal issues in the man’s body. It will also provide
a full filling for long period and aid in digestion (Anne, 2018). Minerals are also important in
diet as they help in developing strong bones and teeth, control intra and extra cellular body fluids
and convert the food into energy (Solan, 2019). Water is an essential element required for every
body functions and processes such as digestion and elimination.
Analysis of the processes that occur within the digestive tract that enable the
person to digest and absorb the main nutrients from the meal
The process of digestion begins in the mouth soon after digestion. Digestion of carbohydrates
initiate in the mouth by the enzyme salivary amylase. Little to no digestion of carbohydrate
occurs in the stomach. In the small intestine, the pancreatic amylase breaks down the starch into
smaller fragments. After that enzyme α-dextrinase works on α-dextrin and breaks one glucose
unit at a time. During digestion, proteins are broken down into its constituent’s amino acids by
breaking the peptide bonds. It begins in the stomach, where the hydrochloric acid produced by
stomach lining and pepsin break the proteins into smaller polypeptides. In the small intestine, the
pancreatic enzymes chymotrypsin and trypsin break specific bonds in amino acid chains. Lipids
are broken down by three lipases lingual lipase, gastric lipase, and pancreatic lipase. Almost all
of the digestion of lipid takes place in the small intestine. Pancreatic lipase splits each
triglyceride into two free fatty acids and a monoglyceride. The small digested molecules are
absorbed by the epithelial cells of the intestinal villi. As the plasma membrane of cell is made up
of hydrophobic phospholipids, water-soluble nutrients use transport molecules embedded in the
membrane to enter cells. They enter the capillary blood in the villi and move to the liver via the
hepatic portal vein. Lipid-soluble nutrients are, on the other hand, diffusible. Upon entering the
cell, they get transported to the lacteals of the villi and subsequently enter by lymphatic vessels
into the circulation. The absorption of most nutrients through the mucosa of the intestinal villi
needs active transport aided by ATP.

References
Anne, M., 2018. Nutrients That Provide No Energy. [Online]
Available at: https://healthyeating.sfgate.com/nutrients-provide-energy-4037.html
[Accessed 15 March 2019].
NHS, 2017. Vitamins and minerals. [Online]
Available at: https://www.nhsinform.scot/healthy-living/food-and-nutrition/eating-well/vitamins-
and-minerals
[Accessed 14 March 2019].
Nordqvist, C., 2017. Nutrition: What is it and why is it important?. [Online]
Available at: https://www.medicalnewstoday.com/articles/160774.php
[Accessed 15 March 2019].
Solan, M., 2019. The best foods for vitamins and minerals. [Online]
Available at: https://www.health.harvard.edu/staying-healthy/the-best-foods-for-vitamins-and-
minerals
[Accessed 15 March 2019].