Revised BIO 102 Nutrition Note.docx

**Nutrition** Food: - is any nutritious substance that people or animals eat or drink to maintain life and growth while nutrition can be defined as the process of obtaining necessary nutrients from food for health and growth. **Types of Nutrients** Nutrients are essential chemical substances in f...

**Nutrition** Food: - is any nutritious substance that people or animals eat or drink to maintain life and growth while nutrition can be defined as the process of obtaining necessary nutrients from food for health and growth. **Types of Nutrients** Nutrients are essential chemical substances in foods needed for healthy living that the body cannot make or make in smaller quantities. Six basic nutrients are essential for growth and development -- i. Carbohydrates ii. Proteins iii. Lipids (Fats and oil) iv. Vitamins and minerals v. Water vi. Fiber Nutrients are divided into two broad classes: macronutrients and micronutrients. **Macronutrients** Macronutrients are nutrients needed in large quantities to provide the energy required for body growth, repair and development of new body tissues, conduct nerve impulses, and regulate life processes. The major types of nutrients that make up the macronutrient group are **carbohydrates**, **proteins**, **fat and oil**, **fiber,** and **water**. **Carbohydrates** Carbohydrates are energy-building foods. Carbohydrates provide three-quarters of the energy required in the body. Carbohydrates exist in three forms: sugar, starch, and fiber. Sources of carbohydrates are table sugar, rice, yam, sweet potatoes, and breadfruit. **Composition of carbohydrates** A carbohydrate is a chemical substance that consists of carbon (C), hydrogen (H), and oxygen (O) atoms usually in the proportion 1:2:1, and must contain both aldehyde and ketone groups. The basic unit of a carbohydrate is a monosaccharide with the formula C~6~H~12~O~6~ i.e., glucose which is used to store and release energy. The brain functions with the use of glucose. [When glucose is in excess in the body, it is stored as glycogen in the liver and muscles (in animals) and as starch (in plants)]. Carbohydrates are classified into three groups namely **monosaccharides**, **disaccharides,** and **polysaccharides** sugar based on sugar units. **Monosaccharides** C~6~H~12~O~6~ are simple sugars such as glucose, fructose, galactose, arabinose, and ribose. Glucose is a form of sugar used by the body\'s system. Fructose is the sugar derived from fruits and honey. The simple sugars are absorbed in the small intestine. **Disaccharides** (C~12~H~22~O~11~) are formed by the combination of two molecules of monosaccharides. Examples are sucrose, a table sugar (composed of glucose and fructose), maltose (composed of two glucose units), and lactose (composed of glucose and galactose). Good sources of sucrose are sugar cane and beet. Lactose is milk sugar found in milk and milk products. Maltose is malt sugar and is found in all sprouted and malted products, beer, and malt drinks. **Polysaccharides** are complex sugars that consist of chains of monosaccharide or disaccharide units. They have high molecular weights and are formed by a combination of more than two molecules of monosaccharides (C~6~H~12~O~6~) n where n is more than two. In terms of sweetness, monosaccharides are the sweetest, followed by disaccharides and then polysaccharides. Examples of polysaccharides are starch, glycogen, dextrin, and cellulose. Glycogen easily degrades back to glucose and so only a small amount is found in its sources. [Dextrin is the product of the first chemical digestion of starch.] [Cellulose is the chemical name for dietary fiber.] Good sources of polysaccharides are cereal grains, seeds, roots, and tubers such as cassava and potatoes; fresh oysters, liver, and dietary fiber. Carbohydrates (complex sugars) are broken down in the body into simple sugars such as glucose and fructose. Complex sugars from fruits are broken down into fructose; sucrose is broken down into glucose, sugars from malt are metabolized as maltose. These simple sugars enter into the bloodstream or cells for hydrolysis. Knowledge of the class of carbohydrates is important for patients with special needs such as diabetic patients (i.e., people who have challenges controlling their blood sugar levels). Monosaccharides and disaccharides are called simple sugars or simple carbohydrates. These are types of sugars that can be easily utilized by the body without further action. Diabetic patients are advised to avoid these types of carbohydrates. Polysaccharides are known as complex carbohydrates usually broken down into simple sugars before the body can use them and are preferred nutrients for diabetic patients. Polysaccharides can also be sub-grouped into digestible (starch, glycogen) and indigestible (cellulose) sugars. **Proteins** The main organic material in the tissue of both plants and animals is protein. In nature, there are above 500 amino acids but the most important are the 22 α-amino acids, however, 20 are found in the genetic code of life. Plants can synthesize their amino acids, which are required for protein production, provided they have a source of nitrate or other simple nitrogenous compounds and sulfur, needed for the synthesis of cysteine and methionine. Animals can also synthesize some amino acids from ammonium ions and carbohydrate metabolites; however, others cannot be synthesized and are therefore dietary essentials. Two amino acids, cysteine and tyrosine, can be synthesized only by metabolism of the essential amino acids - methionine and phenylalanine, respectively. Bacteria living in the rumen of ruminant animals can synthesize all the amino acids commonly present in protein, and the true stomach of the ruminant will continue to receive microbial protein of reasonably good quality for digestion. Proteins consist of amino acids and are the major components of cell structure. Proteins build, repair, and maintain tissues and cells. It functions as parts of various **enzymes** (as coenzymes), **hormones**, and **antibodies**. Proteins are responsible for gene regulation, the formation of cellular structures, and oxygen-blood transportation in the body i.e., hemoglobin. In a situation of energy deficiency in the body, of all the macronutrients, proteins are the last to be used. In extreme cases of starvation, proteins present in the muscles are converted to energy thus resulting in what is called "**muscle wasting**". Food sources of proteins are meat, fish, poultry and its products, milk and milk products, insects, legumes, seeds, and nuts. **Composition of proteins** Proteins are made up of amino acids. Each amino acid has a carbon molecule called the α carbon and attached to it are four groups -- **a hydrogen, an α- carboxyl group** (COOH)**, an α-amine group** (NH~2~)**, and an R-group**, many amino groups are formed by varying the grouping which is attached to the carbon-containing amino group. For example, glycine (CH~2~(NH~2~).COOH; alanine (CH~2~.CH(NH~2~).COOH) and lysine (CH~2~.CH~2~.CH~2~.CH(NH~2~).COOH. Proteins in foods are digested and broken down into amino acids. What is the number of amino acids? Structure of an amino acid **Classification of proteins** Proteins are classified into two groups: essential and non-essential amino acids. Essential amino acids are amino acids that cannot be synthesized by the body and have to be acquired through food. On the other hand, nonessential amino acids are those that can be synthesized by the body. There are nine (09) essential amino acids and 11 non-essential amino acids. **Lipids (Fats and Oils)** Fats and oils are also known as lipids. Fats are a more concentrated form of energy storage than carbohydrates. They are stored in the adipose (fatty) tissues of animals. When fats are consumed, they undergo the following processes: emulsification (breaking down of fat into smaller molecules), digestion, and absorption. Food sources of fats and oils are all types of cooking oil (e.g., palm oil, coconut oil, vegetable oil, and groundnut oil); animal fat, tropical nuts, melon seeds, fish oil, butter, and margarine. [When carbohydrate is consumed in excess quantity, it is stored as glycogen and the rest are converted to fat in the adipose tissue]. The use of fat as an energy source is slow and it is done when the availability of carbohydrates is inadequate. **Composition of Lipids (Fats and Oils)** Fats and oils are organic compounds that, like carbohydrates, are composed of the elements carbon (C), hydrogen (H), and oxygen (O), but in a higher proportion than carbohydrates. Fat is a complex molecule made up of a mixture of fatty acids and glycerol. Lipids are a broader group of biomolecules found in the body of organisms. Fats are the type of lipids necessary for a healthy body. Lipids are soluble in organic solvents but are insoluble in water. Fats are oily substances insoluble in water and sparingly soluble in substances like alcohol. **Classification of fats** There are three classes of lipids - **simple lipids, compound lipids, and derived lipids**. Simple fats = neutral fats. They are chemically made up of triglycerides. Triglycerides contain glycerol and three fatty acids. Neutral fats make up about 99 percent of food fats and body fats. They are neutral because they do not change and do not contain acidic or basic groups. Compound lipids are chemically made up of simple lipids containing phosphorus, carbohydrate, or protein. They are referred to as **phospholipids, glycolipids, and lipoproteins**. Lipoproteins are the most important because they are carriers of fats in the blood. Phospholipids relate to the nervous system. Derived lipids are fat-like substances produced from fats and fatty compounds such as glycerol and fatty acids. Glycerol is the water-soluble part of triglycerides or neutral fat and it makes up about 10 percent of the lipid. During the digestion process, glycerol is removed and reserved for the production of glucose when it is needed. Fatty acids are the forms of fat that the cells burn to produce energy. They may be **saturated** or **unsaturated**. Examples are palmitic acid, myristic acid, oleic acid, stearic acid, linoleic acid, linolenic acid, and arachidonic acid. Saturated fatty acids do not contain double bonds between their carbon atoms while unsaturated fatty acid does. Consequently, unsaturated fatty acids can undergo the process of hydrogenation, unlike saturated fatty acids due to the presence of double bonds. Saturated fatty acids are solid at room temperature while unsaturated fatty acids are in liquid form. Animal fats are examples of saturated fats while vegetable fats are mainly unsaturated. **Unsaturated fatty acids are nutritionally better than saturated fatty acids because the latter increases the cholesterol level in the blood**. Nutritionally, **fatty acids are classified into two: essential and non-essential fatty acids**. Essential fatty acids are those that cannot be produced in the body and need to be supplied through the food we eat. Examples are Linoleic acid, Linolenic acid, and arachidonic acid. However, non-essential fatty acids can be synthesized by the body. Examples are palmitic acid, oleic acid, and butyric acid. **Vitamins And Minerals** **Vitamins** are **a group of organic compounds needed in minute quantities** for normal function, growth, and maintenance of body tissues. Majority of the vitamins are not synthesized in the body and have to be provided through dietary intake. Examples include vitamins A, B, C, D, E, and K. Only folic acid and vitamin D are partially synthesized in the body. **Classification of Vitamins** Vitamins are classified into two: i. Fat-soluble vitamins are those that dissolve in organic solvents e.g., vitamins A, D, E, and K. ii. Water soluble vitamins are those that dissolve in water e.g., vitamins B-complex and C. Vitamins B-complex include vitamins B1 (Thiamine), B2(Riboflavin), B3 (Pantothenic acid), B6 (Pyridoxine) and B12 (Cyanocobalamin). **Minerals** are **inorganic elements that occur in the form of their salts.** They make up about 4% of the body weight. Examples are phosphorus, calcium, potassium, sodium, iodine, iron, copper, sulfur, chlorine, manganese, magnesium, and molybdenum. Like vitamins, minerals are also needed in minute quantities. They are excreted from the body through the kidney, skin, and the bowel so they need to be supplied daily through the diet. **Classification of Minerals** Minerals are classified into three: i. Macro-minerals are required in large amounts in the body. Examples are phosphorus, calcium, chlorine, sodium, and potassium. ii. Micro-minerals are required in small amounts in the body. Examples are iron, magnesium, and sulfur. iii. Trace elements are needed in a few micrograms. Examples are iodine, zinc, fluorine, and molybdenum **Chemical characteristics of vitamins** a. Fat-soluble vitamins b. Water-soluble vitamins **Functions of** **Minerals** i. Minerals regulate cellular oxidation. ii. Minerals act as enzyme activators. iii. Minerals are part of hormone and enzyme molecules. iv. Minerals help to maintain the acid-base balance of body fluids. v. Minerals control the water balance in the body through osmotic pressure and by regulation of the permeability of cell membranes **Water** Water is a chemical compound made of hydrogen and oxygen with the chemical formula H~2~O. Water is fundamental to human health as the human body is composed of approximately **75 percent of water**. Water is part of the body tissue, assists in transporting nutrients to the cells, and removal of waste products from the cells. It helps in regulating body temperature and facilitates digestion. Because water is continually being lost from the body through sweat, urine, feces - stool, and breathing, it must be continually replenished. Water is obtained from drinking water, foods, and beverages. For good health, it is recommended that you - individuals drink about 8-10 glasses of clean potable water daily. **Fiber** Fruits and vegetables are good sources of fiber. Fiber helps to empty the bowel and prevent constipation and fat deposition. Fiber is also known as \"roughage." It is an indigestible plant matter such as cellulose. Fibers can be soluble or insoluble in water. **Insoluble** fiber plays an important role in digestion, helping food move smoothly through the colon (large intestine). Good sources of insoluble are the skin and pulp of many fruits and vegetables, whole grains, popcorn, and seeds. Soluble fiber helps stabilize blood sugar and may reduce Low-Density Lipoprotein (LDL) cholesterol levels. Sources of **soluble** fiber include oatmeal and oat bran, legumes, nuts, and fruits such as apples, oranges, pears, and grapes. Most animals cannot digest the cellulosic part of plant foods, and in the diets of humans, this part of vegetable intake functions as dietary fiber. Dietary fibers are otherwise called non-starch polysaccharides because the bonds between their monosaccharides cannot be broken down by digestive enzymes in the human body. **Nutrition in plants** Plants produce their food by trapping solar energy in photosynthetic systems. Through photosynthesis, plants can synthesize nutrients from carbon dioxide (CO~2~) and water. However, plants do require inorganic salts, which they absorb from the soil surrounding their roots; these include the elements phosphorus (in the form of phosphate), chlorine (as the chloride ion), potassium, sulfur, calcium, magnesium, iron, manganese, boron, copper, and zinc. Plants also require nitrogen, in the form of nitrate (NO~3~^−^) or ammonium (NH~4~^+^) ions. Photosynthesis is written as 6CO~2~ + 6H~2~O → C~6~H~12~O~6~ + 6O~2~ in the presence of radiant light and chlorophyll. **Nutrition in lower organisms such as bacteria** These small organisms, popularly thought of only as sources of infection, are of vital importance in the overall life cycles of plants and animals. A bacterium needs an energy source, a source of carbon, and other required nutrients such as a permissive range of physical conditions such as O~2~ concentration, temperature, and pH. All living organisms require a source of energy. In general, the carbon requirements of organisms must be met by organic carbon (a chemical compound with a carbon-hydrogen bond) or by CO~2~. Overall, [autotrophs are organisms that use inorganic carbon (CO~2~) as a sole source of carbon whereas organisms that use an organic form of carbon (glucose, etc.) as a carbon source are called heterotrophs. Phototrophs are organisms that use light (radiant energy) as an energy source; organisms that use inorganic compounds as energy sources are called chemolithotrophs while organisms that use organic compounds as energy sources are called chemoorganotrophs.] **Major nutritional types of procaryotes** Nutritional Type Energy Source Carbon Source Examples Photoautotrophs Light CO~2~ Cyanobacteria, Green Bacteria Photoheterotrophs Light Organic Compounds Some Purple and Green Bacteria Chemolithoautotrophs Inorganics- H~2~, NH~3~ CO~2~ Few bacteria & many Archaea Chemoorganoheterotrophs Organic compounds Organic compounds Most Bacteria, some Archaea Almost all eucaryotes are either photoautotrophic (e.g., plants and algae) or heterotrophic (e.g., animals, protozoa, fungi). Lithotrophy is unique to procaryotes and photoheterotrophy, common in the Purple and Green Bacteria, occurs only in a very few eucaryotic algae. Phototrophy has not been found in the Archaea, except for non-photosynthetic light-driven ATP synthesis in the extreme halophiles. **Syntrophism** The concept of syntrophy describes mutualistic microbial associations characterized by the exchange of metabolic intermediates between the partnering microorganisms as a means to jointly facilitate an otherwise energetically unfavorable metabolic process. Well-studied are syntrophic interactions between fermentative bacteria and methanogenic archaea with the latter consuming hydrogen or formate produced by the former. Another example occurs in thiamin-requiring yeasts and fungi, where (group A) synthesized the thiazole component of the thiamin molecule but required the pyrimidine portion preformed; for a second group (group B), the relationship is reversed. When group A and group B are grown together in a thiamin-free medium, both types of organisms survive, since each organism synthesizes the growth factor required by its partner; neither organism grows alone under these same conditions. Thus, two or more types of microorganisms often grow in situations in which one species only would not. Such nutritional interrelationships may explain the fact that the nutritionally demanding lactic acid bacteria can coexist with the nutritionally nondemanding coliform bacteria in the intestinal tracts of animals.