What Is Necessary For The Body's Maintenance Growth And Repair

Chapter 15. Animal Diet and the Digestive Organisation

15.2 Nutrition and Energy Production

Learning Objectives

By the end of this section, you lot volition exist able to:

Explain why an brute'due south diet should be balanced and meet the needs of the body
Define the primary components of food
Depict the essential nutrients required for cellular function that cannot exist synthesized by the brute body
Explicate how energy is produced through diet and digestion
Describe how excess carbohydrates and free energy are stored in the body

Given the diversity of animate being life on our planet, information technology is not surprising that the animal diet would besides vary substantially. The fauna diet is the source of materials needed for building Dna and other complex molecules needed for growth, maintenance, and reproduction; collectively these processes are called biosynthesis. The nutrition is also the source of materials for ATP product in the cells. The diet must be balanced to provide the minerals and vitamins that are required for cellular role.

Food Requirements

What are the fundamental requirements of the animal diet? The animal diet should be well counterbalanced and provide nutrients required for bodily function and the minerals and vitamins required for maintaining structure and regulation necessary for good wellness and reproductive adequacy. These requirements for a man are illustrated graphically in Figure 15.14

Figure 34.14. For humans, a balanced diet includes fruits, vegetables, grains, and protein. (credit: USDA) — Figure 15.fourteen.
For humans, a balanced diet includes fruits, vegetables, grains, and poly peptide. (credit: USDA)

Concept in Action

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The first footstep in ensuring that you lot are meeting the food requirements of your body is an awareness of the nutrient groups and the nutrients they provide. To acquire more about each food group and the recommended daily amounts, explore this interactive site by the United States Section of Agriculture.

Organic Precursors

The organic molecules required for edifice cellular material and tissues must come up from food. Carbohydrates or sugars are the master source of organic carbons in the animal body. During digestion, digestible carbohydrates are ultimately cleaved down into glucose and used to provide free energy through metabolic pathways. Circuitous carbohydrates, including polysaccharides, can be broken down into glucose through biochemical modification; notwithstanding, humans do not produce the enzyme cellulase and lack the ability to derive glucose from the polysaccharide cellulose. In humans, these molecules provide the fiber required for moving waste matter through the large intestine and a healthy colon. The abdominal flora in the human being gut are able to extract some nutrition from these plant fibers. The backlog sugars in the torso are converted into glycogen and stored in the liver and muscles for later utilise. Glycogen stores are used to fuel prolonged exertions, such equally long-distance running, and to provide free energy during nutrient shortage. Excess glycogen can be converted to fats, which are stored in the lower layer of the pare of mammals for insulation and energy storage. Excess digestible carbohydrates are stored by mammals in order to survive famine and aid in mobility.

Some other of import requirement is that of nitrogen. Poly peptide catabolism provides a source of organic nitrogen. Amino acids are the building blocks of proteins and protein breakup provides amino acids that are used for cellular function. The carbon and nitrogen derived from these get the edifice block for nucleotides, nucleic acids, proteins, cells, and tissues. Excess nitrogen must be excreted every bit information technology is toxic. Fats add flavor to food and promote a sense of satiety or fullness. Fat foods are also significant sources of free energy because one gram of fat contains 9 calories. Fats are required in the diet to assist the assimilation of fat-soluble vitamins and the product of fat-soluble hormones.

Essential Nutrients

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While the animal body can synthesize many of the molecules required for function from the organic precursors, there are some nutrients that need to exist consumed from food. These nutrients are termed essential nutrients, meaning they must be eaten, and the trunk cannot produce them.

The omega-3 alpha-linolenic acid and the omega-6 linoleic acid are essential fatty acids needed to brand some membrane phospholipids. Vitamins are some other class of essential organic molecules that are required in small quantities for many enzymes to role and, for this reason, are considered to exist co-enzymes. Absence or low levels of vitamins can have a dramatic outcome on health, as outlined in Tabular array xv.ane and Table 15.2. Both fat-soluble and water-soluble vitamins must be obtained from food. Minerals, listed in Tabular array fifteen.3, are inorganic essential nutrients that must exist obtained from nutrient. Among their many functions, minerals help in structure and regulation and are considered co-factors. Sure amino acids also must be procured from food and cannot be synthesized by the body. These amino acids are the "essential" amino acids. The human torso can synthesize only xi of the 20 required amino acids; the rest must be obtained from nutrient. The essential amino acids are listed in Table 15.iv.

Table xv .one.Water-soluble Essential Vitamins
Vitamin	Function	Deficiencies Tin can Pb To	Sources
Vitamin B₁ (Thiamine)	Needed by the trunk to process lipids, proteins, and carbohydrates Coenzyme removes CO₂ from organic compounds	Muscle weakness, Beriberi: reduced centre function, CNS problems	Milk, meat, dried beans, whole grains
Vitamin B₂ (Riboflavin)	Takes an active office in metabolism, aiding in the conversion of nutrient to free energy (FAD and FMN)	Cracks or sores on the outer surface of the lips (cheliosis); inflammation and redness of the tongue; moist, scaly pare inflammation (seborrheic dermatitis)	Meat, eggs, enriched grains, vegetables
Vitamin B₃(Niacin)	Used past the body to release free energy from carbohydrates and to procedure booze; required for the synthesis of sex hormones; component of coenzyme NAD⁺ and NADP⁺	Pellagra, which can result in dermatitis, diarrhea, dementia, and death	Meat, eggs, grains, nuts, potatoes
Vitamin B₅(Pantothenic acid)	Assists in producing energy from foods (lipids, in particular); component of coenzyme A	Fatigue, poor coordination, retarded growth, numbness, tingling of hands and anxiety	Meat, whole grains, milk, fruits, vegetables
Vitamin B₆(Pyridoxine)	The chief vitamin for processing amino acids and lipids; as well helps convert nutrients into free energy	Irritability, depression, defoliation, mouth sores or ulcers, anemia, muscular twitching	Meat, dairy products, whole grains, orange juice
Vitamin B₇(Biotin)	Used in energy and amino acid metabolism, fatty synthesis, and fat breakdown; helps the body employ blood sugar	Hair loss, dermatitis, depression, numbness and tingling in the extremities; neuromuscular disorders	Meat, eggs, legumes and other vegetables
Vitamin B₉(Folic acrid)	Assists the normal development of cells, especially during fetal development; helps metabolize nucleic and amino acids	Deficiency during pregnancy is associated with birth defects, such equally neural tube defects and anemia	Leafy light-green vegetables, whole wheat, fruits, basics, legumes
Vitamin B₁₂ (Cobalamin)	Maintains healthy nervous organisation and assists with claret cell formation; coenzyme in nucleic acid metabolism	Anemia, neurological disorders, numbness, loss of balance	Meat, eggs, animate being products
Vitamin C (Ascorbic acid)	Helps maintain connective tissue: bone, cartilage, and dentin; boosts the immune system	Scurvy, which results in bleeding, hair and tooth loss; joint hurting and swelling; delayed wound healing	Citrus fruits, broccoli, tomatoes, red sweet bong peppers

Table fifteen.2. Fat-soluble Essential Vitamins
Vitamin	Function	Deficiencies Can Lead To	Sources
Vitamin A (Retinol)	Critical to the evolution of bones, teeth, and peel; helps maintain eyesight, enhances the immune system, fetal development, gene expression	Dark-blindness, peel disorders, impaired amnesty	Dark green leafy vegetables, yellow-orange vegetables fruits, milk, butter
Vitamin D	Critical for calcium absorption for bone development and strength; maintains a stable nervous arrangement; maintains a normal and strong heartbeat; helps in blood clotting	Rickets, osteomalacia, immunity	Cod liver oil, milk, egg yolk
Vitamin E (Tocopherol)	Lessens oxidative damage of cells,and prevents lung damage from pollutants; vital to the immune system	Deficiency is rare; anemia, nervous system degeneration	Wheat germ oil, unrefined vegetable oils, nuts, seeds, grains
Vitamin K (Phylloquinone)	Essential to blood clotting	Bleeding and easy bruising	Leafy green vegetables, tea

Table 15.iii. Minerals and Their Function in the Human being Torso
Mineral	Role	Deficiencies Can Lead To	Sources
*Calcium	Needed for musculus and neuron function; center health; builds bone and supports synthesis and function of blood cells; nerve function	Osteoporosis, rickets, muscle spasms, impaired growth	Milk, yogurt, fish, green leafy vegetables, legumes
*Chlorine	Needed for production of hydrochloric acid (HCl) in the stomach and nerve role; osmotic balance	Muscle cramps, mood disturbances, reduced ambition	Table salt
Copper (trace amounts)	Required component of many redox enzymes, including cytochrome c oxidase; cofactor for hemoglobin synthesis	Copper deficiency is rare	Liver, oysters, cocoa, chocolate, sesame, nuts
Iodine	Required for the synthesis of thyroid hormones	Goiter	Seafood, iodized salt, dairy products
Iron	Required for many proteins and enzymes, notably hemoglobin, to prevent anemia	Anemia, which causes poor concentration, fatigue, and poor immune role	Red meat, leafy greenish vegetables, fish (tuna, salmon), eggs, dried fruits, beans, whole grains
*Magnesium	Required co-factor for ATP formation; os formation; normal membrane functions; muscle function	Mood disturbances, musculus spasms	Whole grains, leafy greenish vegetables
Manganese (trace amounts)	A cofactor in enzyme functions; trace amounts are required	Manganese deficiency is rare	Common in most foods
Molybdenum (trace amounts)	Acts as a cofactor for iii essential enzymes in humans: sulfite oxidase, xanthine oxidase, and aldehyde oxidase	Molybdenum deficiency is rare
*Phosphorus	A component of bones and teeth; helps regulate acid-base residue; nucleotide synthesis	Weakness, os abnormalities, calcium loss	Milk, hard cheese, whole grains, meats
*Potassium	Vital for muscles, heart, and nervus function	Cardiac rhythm disturbance, muscle weakness	Legumes, potato skin, tomatoes, bananas
Selenium (trace amounts)	A cofactor essential to activity of antioxidant enzymes like glutathione peroxidase; trace amounts are required	Selenium deficiency is rare	Common in most foods
*Sodium	Systemic electrolyte required for many functions; acrid-base rest; water residual; nerve function	Muscle cramps, fatigue, reduced appetite	Table common salt
Zinc (trace amounts)	Required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase	Anemia, poor wound healing, can lead to brusk stature	Mutual in most foods
*Greater than 200mg/day required

Tabular array xv.four. Essential Amino Acids
Amino acids that must be consumed	Amino acids anabolized by the body
isoleucine	alanine
leucine	selenocysteine
lysine	aspartate
methionine	cysteine
phenylalanine	glutamate
tryptophan	glycine
valine	proline
histidine*	serine
threonine	tyrosine
arginine*	asparagine
*The human body tin synthesize histidine and arginine, but non in the quantities required, specially for growing children.

Nutrient Energy and ATP

Animals need nutrient to obtain energy and maintain homeostasis. Homeostasis is the ability of a system to maintain a stable internal environment even in the face of external changes to the environment. For example, the normal body temperature of humans is 37°C (98.6°F). Humans maintain this temperature even when the external temperature is hot or common cold. Information technology takes energy to maintain this body temperature, and animals obtain this energy from nutrient.

The chief source of energy for animals is carbohydrates, mainly glucose. Glucose is called the torso'due south fuel. The digestible carbohydrates in an beast'due south diet are converted to glucose molecules through a series of catabolic chemical reactions.

Adenosine triphosphate, or ATP, is the primary energy currency in cells; ATP stores energy in phosphate ester bonds. ATP releases free energy when the phosphodiester bonds are broken and ATP is converted to ADP and a phosphate group. ATP is produced past the oxidative reactions in the cytoplasm and mitochondrion of the jail cell, where carbohydrates, proteins, and fats undergo a serial of metabolic reactions collectively called cellular respiration. For instance, glycolysis is a series of reactions in which glucose is converted to pyruvic acid and some of its chemical potential energy is transferred to NADH and ATP.

ATP is required for all cellular functions. It is used to build the organic molecules that are required for cells and tissues; information technology provides energy for muscle wrinkle and for the manual of electrical signals in the nervous system. When the amount of ATP is bachelor in excess of the body'due south requirements, the liver uses the excess ATP and excess glucose to produce molecules called glycogen. Glycogen is a polymeric grade of glucose and is stored in the liver and skeletal muscle cells. When blood sugar drops, the liver releases glucose from stores of glycogen. Skeletal musculus converts glycogen to glucose during intense do. The process of converting glucose and excess ATP to glycogen and the storage of excess free energy is an evolutionarily important step in helping animals deal with mobility, food shortages, and famine.

Obesity

Obesity is a major health business organization in the United States, and there is a growing focus on reducing obesity and the diseases it may atomic number 82 to, such equally type-two diabetes, cancers of the colon and chest, and cardiovascular disease. How does the food consumed contribute to obesity?

Fatty foods are calorie-dense, pregnant that they have more calories per unit mass than carbohydrates or proteins. I gram of carbohydrates has 4 calories, one gram of protein has four calories, and i gram of fat has nine calories. Animals tend to seek lipid-rich nutrient for their higher energy content.

The signals of hunger ("time to eat") and satiety ("time to finish eating") are controlled in the hypothalamus region of the brain. Foods that are rich in fatty acids tend to promote satiety more than than foods that are rich only in carbohydrates.

Backlog saccharide and ATP are used by the liver to synthesize glycogen. The pyruvate produced during glycolysis is used to synthesize fatty acids. When there is more glucose in the body than required, the resulting excess pyruvate is converted into molecules that somewhen effect in the synthesis of fat acids within the trunk. These fatty acids are stored in adipose cells—the fat cells in the mammalian body whose primary role is to shop fat for later use.

Information technology is important to note that some animals benefit from obesity. Polar bears and seals demand trunk fat for insulation and to keep them from losing trunk rut during Arctic winters. When food is deficient, stored body fat provides energy for maintaining homeostasis. Fats prevent dearth in mammals, assuasive them to access free energy when nutrient is non available on a daily basis; fats are stored when a large kill is made or lots of food is available.

Summary

Animal diet should be balanced and encounter the needs of the body. Carbohydrates, proteins, and fats are the primary components of food. Some essential nutrients are required for cellular part but cannot exist produced past the fauna trunk. These include vitamins, minerals, some fat acids, and some amino acids. Food intake in more than than necessary amounts is stored as glycogen in the liver and musculus cells, and in fat cells. Excess adipose storage tin can pb to obesity and serious health problems. ATP is the energy currency of the cell and is obtained from the metabolic pathways. Excess carbohydrates and free energy are stored as glycogen in the body.

Exercises

Which of the following statements is not true?
1. Essential nutrients can be synthesized by the body.
2. Vitamins are required in pocket-size quantities for bodily part.
3. Some amino acids can be synthesized by the body, while others need to exist obtained from nutrition.
4. Vitamins come in 2 categories: fat-soluble and water-soluble.
Which of the post-obit is a water-soluble vitamin?
1. vitamin A
2. vitamin E
3. vitamin K
4. vitamin C
What is the master fuel for the trunk?
1. carbohydrates
2. lipids
3. protein
4. glycogen
Excess glucose is stored as ________.
1. fat
2. glucagon
3. glycogen
4. it is not stored in the body
What are essential nutrients?
What is the role of minerals in maintaining good health?
Talk over why obesity is a growing epidemic.
At that place are several nations where malnourishment is a mutual occurrence. What may be some of the health challenges posed by malnutrition?

Answers

A
D
A
C
Essential nutrients are those nutrients that must be obtained from the nutrition because they cannot exist produced by the body. Vitamins and minerals are examples of essential nutrients.
Minerals—such every bit potassium, sodium, and calcium—are required for the performance of many cellular processes, including muscle contraction and nerve conduction. While minerals are required in trace amounts, not having minerals in the diet can exist potentially harmful.
In the United States, obesity, especially childhood obesity, is a growing business. Some of the contributors to this state of affairs include sedentary lifestyles and consuming more than processed foods and less fruits and vegetables. Every bit a upshot, even immature children who are obese tin face health concerns.
Malnutrition, often in the form of non getting plenty calories or non enough of the essential nutrients, can take severe consequences. Many malnourished children have vision and dental problems, and over the years may develop many serious health problems.

Glossary

bile: digestive juice produced by the liver; important for digestion of lipids

carboxypeptidase: protease that breaks downwards peptides to single amino acids; secreted by the castor border of the modest intestine

chyme: mixture of partially digested nutrient and stomach juices

digestion: mechanical and chemic break down of food into pocket-sized organic fragments

essential nutrient: nutrient that cannot exist synthesized by the body; it must exist obtained from food

large intestine: digestive system organ that reabsorbs water from undigested material and processes waste material matter

liver: organ that produces bile for digestion and processes vitamins and lipids

mineral: inorganic, elemental molecule that carries out important roles in the trunk

pocket-sized intestine: organ where digestion of protein, fats, and carbohydrates is completed

stomach: sac-like organ containing acidic digestive juices

vitamin: organic substance necessary in minor amounts to sustain life