Types of Nutrients

Types of Nutrients: Sources and Functions

Below we will cover the different nutrients you will find in most meals you eat and their functions.

Proteins

Proteins consist of long chains of amino acids and are essential for the repair and maintenance of body cells. Amino acids are consumed from foods such as meats, fish, dairy, eggs, nuts, and beans, and are then converted into proteins in protein synthesis conducted by RNA and ribosome molecules. Here are some of the uses of proteins in plants and animals:

• Enzymes: all enzymes are proteins. These molecules speed up biochemical reactions by offering a different pathway for the reaction and lowering the activation energy. Energy release, muscle contraction, and digestion all rely on enzymes.
• Blood transport: haemoglobin is the protein that transports blood around the body.
• Hormones: many hormones are made up of proteins. Hormones will also bind to protein receptors on cells and organs and carry instructions.
• Structure: fibrous proteins like collagen and keratin provide structural integrity to bones, skin, and hair.
• Immune system: the antibodies which attack foreign pathogens are made up of protein.
• Phototropism in plants: proteins are essential in plants in responding to changes in light and controlling phototropism.

Carbohydrates

Carbohydrates are organic molecules found in bread, pasta, starchy vegetables, oats, and grains. They are often split into two groups: simple carbohydrates (sugars) and complex carbohydrates (starch, glycogen, fibre). Carbohydrates are broken down to glucose, which is then broken down further during glycolysis into pyruvate and lactate. Further reactions including the Krebs' Cycle produce adenosine triphosphate (the energy molecule) and carbon dioxide. Take a look at our aerobic respiration article for more information.

- StudySmarter Content (Aerobic Respiration)

Here are the uses of carbohydrates in plants and animals:

• Energy: carbohydrates are a vital source of energy and are broken down to glucose in aerobic respiration. Simple carbohydrates are broken down quickly for a short energy release whereas complex carbohydrates take longer to break down and release energy slower.
• Storage: when an organism has enough glucose to carry out biochemical processes, it will convert glucose to a storage molecule. This molecule is glycogen in animals and is stored in the liver and the muscles, whereas plants store glucose as starch.
• Digestion: fibre is not digested and instead aids with digestion by moving food smoothly throughout the digestive system.
• Muscle preservation: when glucose is not available, the body will break down muscles into amino acids and use these for energy instead. Therefore a consistent supply of carbohydrates is essential in avoiding these drastic measures.

Lipids

Types of lipids include triglycerides (three fatty acids and glycerol), sterols (such as cholesterol), and phospholipids. These molecules are found in oils, fats (such as lard and butter), processed foods, meats, and nuts. Each gram of fat contains 9 calories, compared to only 4 calories in each gram of carbohydrate, so the breakdown of fats releases lots of energy. Let's have a look at some of the uses of fats in the body:

• Energy: the breakdown of fats releases lots of energy, so these molecules can be useful when energy is required to regulate body temperatures or contract muscles.
• Vitamins ADEK: these vitamins are termed 'fat-soluble'. This means that lipids must be present in the small intestine when these vitamins pass through the digestive system for them to work.
• Protection of organs: when fat is not used for energy, it will often be stored around delicate organs to protect them. This process is essential for survival, so in the absence of lipids, carbohydrates will be converted to fats.
• Essential fatty acids: the three essential fatty acids (linolenic, arachidonic, and linoleic) can only be found in lipids, and are pivotal for heart health and brain function.
• Transport between cells: phospholipid bilayers surround body cells and control which molecules enter and leave the cell. The phosphate head is hydrophilic (water-loving) so is on the outside of the membrane, while the fatty tail is hydrophobic and so is on the inside of the bilayer.

Figure 1: diagram of a phospholipid bilayer, via Wikimedia commons.

Vitamins

Vitamins are organic nutrients that are distinguished by their solubility. B and C vitamins are soluble in water, whereas A, D, E, and K vitamins are soluble in fat. Here are the roles of each vitamin:

• B1, B2, B3, B4, and B6 all aid the biochemical reactions involved in metabolism

• B7 assists specifically with amino acids and fatty acids.

• B9 is essential for the growth, repair, and maintenance of cells.

• B12 aids red blood cell synthesis.

• Vitamin C is an antioxidant.

• Vitamin A maintains healthy immune systems.

• Vitamin D is for healthy bones and teeth.

• Vitamin E is also an antioxidant.

• Vitamin K helps with blood clotting.

Minerals

Minerals on the other hand are inorganic substances which are required in tiny amounts. However, they are still necessary for assisting in a variety of biochemical processes:

• Calcium ensures strong teeth and bones and helps with muscle contraction and nerve coordination.
• Iron works in coalition with haemoglobin to carry blood around the body.
• Chloride maintains stomach acidity and balances fluids.
• Sodium and potassium balance fluids and help with muscle contraction and nerve coordination.
• Magnesium aids protein synthesis and has small roles in muscle contraction and the nervous system.

Water

Our body is made up of roughly 60% water, so it makes sense that we need a lot of it. Water provides the aqueous medium for all chemical reactions to occur. Without it, our organ systems would stop working! We require about 2 litres of water a day.

Elemental Nutrients

Let's have a look at some elements which are large components of the majority of nutrients.

Nitrogen

Nitrogen cycles through ecosystems through nitrogen-fixing bacteria and absorption by consumers. Nitrogen is essential in plants and animals for the following reasons:

• Chlorophyll - nitrogen is a major component of chlorophyll, so lots of nitrogen is needed to produce the maximum amount of chlorophyll pigment so plants can photosynthesise as much as possible.

• DNA - nitrogen is present in the nucleotides, which are the building blocks of DNA. DNA is the genetic material that provides the instructions for all biochemical processes and hereditary information.

• ATP - the monomers which make up the energy transfer molecule adenosine triphosphate contain nitrogen. ATP is pivotal in controlling energy transfer in metabolic processes.

• Amino acids - nitrogen makes up a substantial proportion of amino acid residues, which are the building blocks when manufacturing proteins. These proteins are essential in manufacturing protective structures and useful enzymes.

Phosphorus

Phosphorus is an extremely rare element that circulates between rocks, soils, oceans, and ecosystems very slowly. Phosphorus is important in the body for the following reasons:

• Phosphorus is an important molecule when building up bones and teeth.

• Phosphorus is required when building up DNA and RNA molecules, which are necessary molecules for storing genetic material and synthesising proteins.

• Energy release requires phosphorus, as it is a component of ATP.

• When building up cell membranes, phosphorus is essential for the synthesis of phospholipids.

• Phosphorus is vital in muscle contraction, heartbeat rhythm, and nerve connections.

Figure 2: Here is the equation showing the break down of the energy molecule ATP to ADP (adenosine diphosphate) and inorganic phosphate (and energy release).

Carbon

Carbon forms the structural backbone for all organic molecules. Carbon's ability to form strong covalent bonds in nature makes it a very unique and useful molecule. Here are how carbon is used in the body:

• Carbon is the backbone of glucose molecules so is essential in aerobic respiration and energy release in the body.

• Carbon is a key component in proteins, lipids, and fats.

• Single and double carbon-carbon bonds determine whether fatty acids are saturated or unsaturated.