Essential Nutrients And Their Metabolism

Essential Nutrients and their Metabolism

Nutrition

• A process by which food is taken into and used by the body. • Includes digestion, absorption, transport, and metabolism. • Study of food and drink requirements for normal body function

Nutrients • Chemicals taken into the body that provide energy and building blocks for new molecules.

• 3 Major Functions: • Providing energy for body processes and movement • Providing structural material for body tissues. • Regulating body processes.

6 Major Classes of Nutrients: *Macronutrients (broken down by enzymes) a. Carbohydrates b. Protein c. Lipids *Micronutrients (not being broken down) a. Vitamins b. Minerals c. Water

Essential nutrients Body cannot manufacture them or is unable to manufacture adequate amounts of them.

Calorie

Amount of energy (heat) necessary to raise the temperature of 1gram of water 1˚C

CARBOHYDRATES (60% of daily kilocaloric intake)

FUNCTIONS: - ENERGY (4 calories/gram) - Cell Maintenance - Heat Generation - Regulation of Fat &Protein Metabolism

Simple Carbohydrates (Simple Sugars): Monosaccharides and Disaccharides Complex Carbohydrates: Polysacchrides

FIBER FUNCTIONS: - Binds with water to allow food residue to pass more quickly through the intestinal tract - Binds with carcinogens - Binds to cholesterol

FUNCTIONS: - Binds with water to allow food residue to pass more quickly through the intestinal tract - Binds with carcinogens - Binds to cholesterol

• Starch- energy-storage in plants • Glycogen- energy-storage

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Lactose- from animals Glucose – from plants Fructose – from fruits and berries Sucrose – from sugarcane and sugar beets • Maltose- from germinating cereals

Glucose

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It is absorbed directly from the digestive tract or synthesized by the liver

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Primary energy source for most cell, which use the energy derived from broken down of glucose to produce ATP

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Forms deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and ATP molecules.

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Combines with proteins to form glycoproteins which function as receptor molecules on surface of plasma membrane.

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Its excess in the blood following a meal can be used to form glycogen or it can be partially broken down, and the components to form fat.

Glycogen

• A short-term energy storage molecule, which can only be stored by the body in limited amounts . • Can be rapidly converted back to glucose when energy is needed. • Most of it was stored in skeletal muscle and liver.

LIPIDS

FUNCTIONS: • ENERGY (9 calories/gram) • A long-term energy storage molecule, which can only be stored in the body in large amounts. • Supply Essential Fatty Acids and Carry Fat Soluble Vitamins (A,D,E, & K) • Shock Absorption • Surrounds, pads and protects organs • Act as an insulator, which helps to reduce heat loss.

Triglycerides or Triacylglycerols

• The most common type of lipid in the diet. • Accounts 95% of the total lipid intake • Can be used to produce ATP • Delivers over twice as many calories as does a gram of carbohydrate or protein.

Saturated Fats • Fatty acids have only single covalent bonds between carbons • Solid at room temperature • Animal origin • Raise blood cholesterol level

Unsaturated Fats

• Have one (monounsaturated) or more (polyunsaturated) doubles bonds. • Liquid at room temperature • Plant origin • Lower blood cholesterol level

Lipoproteins

• transport fats in the blood (HDL - "good", LDL - "bad")

Steroids and Phospholipids • (part of the cell membrane and are used to construct myelin sheaths around the axons of nerve cells) • accounts 5% of the total lipid intake

Cholesterol

• Derived fats • A steroid found in high concentrations in the brain, liver, and egg yolks • Present in whole milk, cheese, butter and meats. • Component of cell membrane • Can be modified to form other useful molecules such as Bile salts (emulsify fats) and Steroid hormones (includes sex hormones). • Contributes to Cardiovascular disease.

Lecithin • A phospholipid which accounts as a major component of cell membranes • A good source is egg yolks. • Found in bile and helps emulsify fats

Linoleic acid and Alpha linoleic acid

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Essential fatty acids as they cannot be synthesized by the body.

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Found in plant oils, such as canola or soybean oils.

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Can be converted to Arachidonic acid (used to produce prostaglandins that increase blood clotting.)

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Can be converted to Eicosapenaenoic acid or EPA (used to produce prostaglandins that decrease blood clotting.) that are found in herring, tuna, and sardines.

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Individuals who eat this from certain foods for two times or more times a week have a lower risk or heart attack because of reduced blood clotting.

PROTEINS (10% of daily kilocaloric intake)

• Chains of amino acids • Our body can manufacture 12 of the 20 amino acids but the other 8 must be obtained in the food we eat.

FUNCTIONS: - ENERGY (4 calories/gram) - Part of Hormones, Antibodies & Enzymes - Fluid Balance - Build and Repair Tissues - Ion channels, carrier molecules, and receptor molecules in the cell membrane

• Collagen- provides structural strength in connective tissue, as does keratin in the skin. • Actin and Myosin- makes muscle contraction possible. • Enzymes- are responsible for regulating the rate of chemical reactions in the body. • Protein hormones- regulate many physiological processes. • Proteins in blood- act as clotting factors, transport molecules, and buffers. • Antibodies and Lymphokines- function in the immune system

Complete protein foods • Contains all eight essential amino acids in the needed proportions. • Can be obtained in animal proteins whereas tend to be incomplete in plant proteins

VITAMINS

• Organic molecules that exist in minute quantities in food. • Not broken down by catabolism but are used by the body in their original or slightly modified forms. • After its chemical structure destroyed, its function is lost.

FUNCTIONS: • Normal Metabolism • Normal Growth • Normal Development

Coenzymes • Combine with enzymes to make the enzymes functional Examples: • Vitamins B2 and B3 biotin, and Pantothenic acid (critical for some of the chemical reactions involved in the production of ATP) • Folate and Vitamin B12 (for nucleic acid synthesis) • Vitamins a, B1, B6, B12, C, and D (for growth) • Vitamin K (for blood clotting)

Fat-soluble vitamins • Are absorbed from the intestine along with lipids. • It is possible to accumulate in the body to the point of toxicity.

Water-soluble vitamins • Are absorbed with water from the intestinal tract and typically remain in the body only a short time before being excreted in the urine.

Provitamin • A part of a vitamin that can be assembled or modified by the body into a functional vitamin. • Example: • Beta carotene is an example that can be modified by the body to form vitamin A. • 7-dehydrocholesterol can be converted to vitamin D. • Tryptophan can be converted to niacin.

Free Radicals • are molecules, produced as a part of normal metabolism, that are missing an electron. • can replace the missing electron by taking an electron from cell molecules, such as fats, proteins, or DNA, resulting in damage to the cell.

Antioxidants • are substances that prevent oxidation of cell components by donating an electron to free radicals. Examples are beta carotene (provitamin A), vitamin C, and Vitamin E.

MINERALS

• inorganic nutrients that are essential for normal metabolic functions. • taken into the body by themselves or in combination with organic molecules. • 4-5% of the total body weight Example: • Women who suffer from excessive menstrual bleeding may need an iron supplement.

FUNCTIONS: • Water Balance • Acid-Base Balance • Resting membrane potentials and generating action potentials • Adding mechanical strength to bones and teeth • Acting as coenzyme, buffers, or regulators of osmotic pressure • Regulate Tissue Excitability • Blood Clotting • Heart Rhythm Regulation

• Macrominerals • -those that people that require daily in amounts over 100mg • Examples are Calcium, Phosphorus, Sodium, Potassium, Magnesium, Chloride, and Sulfur.

• Microminerals • -those that people that require daily in amounts less than 100mg • Examples are Iron, Zinc, Manganese, Iodine, Fluoride, Copper, Cobalt, Chromium , and Selenium.

WATER (Body weight is 70%)

FUNCTIONS: • Most basic nutrient need • Involved in almost every vital part of the body's processes “Eight glasses of fluids daily”

METABOLISM • The total of all the chemical reactions that occur in the body.

Anabolism • Energy–requiring process by which small molecules are joined to form larger ones. • It occurs in all cells of the body as they divide to form new cells, maintain their own intracellular structure, and produce molecules such as hormones, neurotransmitter, or extra cellular matrix molecules for export.

Catabolism • Energy-releasing process by which large molecules are broken down in smaller ones. • It begins during the process of digestion and is concluded within individuals cells.

• Cellular Metabolismchemical reactions that occur within cells. • ATP– energy currency of the cell. • Biochemical Pathway – series of chemical reaction which controls the energy release from molecules.

Regulation of Enzymes in several ways: Enzymes Synthesis • Their synthesis depends on DNA. Thus, it is under genetic control. Receptor–mediated enzyme activity • The combination of a chemical signal can activate or inhibit enzyme activity. Production Control of enzyme activity • The end product of a biochemical pathway can inhibit the enzyme responsible for the first reaction in the pathway (a negative – feedback regulation that prevents accumulation of the intermediate products and the end product of the pathway.)

CARBOHYDRATE METABOLISM

Glycolysis • Breakdown of glucose to two pyruvic acid molecules. • Two ATP molecules are used and four ATP molecules are produced, for a net gain of two ATP molecules.

Carrier molecule • Functions to move the H and electrons to other parts of the cell. • Example is nicotinamide adenine dinucleotide (NADH) which can be used in other chemical reactions or in the production of ATP molecules in the electron-transport chain.

Anaerobic Respiration

• The breakdown of glucose in the absence of oxygen that yields two ATP • Takes place when the amount of oxygen are limited • Functions to quickly produce few ATP molecules for a short time.

2 Phases of Anaerobic Respiration: 1. Glycolysis 2. Lactic acid formation - Conversion of pyruvic acid to lactic acid. - Requires input of energy from the NADH produced in Phase1.

Lactic Acid • Transported by the blood to the liver • As oxygen becomes available in the liver, it can be converted through a series of chemical reactions into glucose.

Aerobic Respiration

• The breakdown of glucose in the presence of oxygen that yields carbon dioxide, water, and 38 molecules of ATP.

4 Phases of Aerobic Respiration: •

Glycolysis (Anaerobic)

2. Acetyl-coenzyme A formation a. Each pyruvic acid move from the cytoplasm into a mitochondrion to form carbon dioxide and two-carbon acetyl group b. Hydrogen ions were released to produce NADH. 3. Citric acid cycle (Kreb’s cycle) a. Acetyl-CoA combines with four carbon molecule to form a sixcarbon citric acid molecule, which enters the citric acid cycle. b. The six-carbon citric acid molecule is converted, in a number of steps, into four-carbon molecules c. It can then combine with another acetyl-CoA molecule to form another citric acid molecule, and reinitiate the cycle. d. Two carbon atoms are used to form carbon dioxide; and energy, H, and electrins are released. They are used to produce ATP, NADH and another carrier molecule flavin adenine dinucleotide (FADH2).

4. Electron-transport chain a. A series of electron transport molecules attached to the inner mitochondrial membrane. b. Electrons are transferred from NADH and FADH2 to the electron transport carriers, and H released into the inner mitochondrial compartment. Some are also H pumps, which use some of the energy from the transported electrons to pump H from inner to outer mitochondrial compartment. c. The H passes through special channels in the inner mitochondrial membrane that couple the movement of the H to ATP production. d. Two H and two electrons combine with an O2 atom to form H2O.

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2 are produced in glycolysis, 2 in citric acid cycle, and 34 are formed through the electron-transport chain.

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It is the total number of ATP formed in liver, kidneys, and heart, where 3 ATP are produced for each NADH molecule.

38 ATP

36 ATP

• Two NADH produced by glycolysis (that cannot cross the inner mitochondrial membrane) donates a shuttle molecule that carries the electrons to the electron-transport chain. • It is the total number of ATP formed in skeletal muscle and in the brain, where 2 ATP are produced for each NADH.

LIPID METABOLISM

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Two carbon atoms are removed from the end of a fatty acid chain to form acetyl-CoA.

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Carbon atoms are removed two at a time until the entire fatty acid chain is converted into acetyl-CoA.

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Acetyl-CoA can enter the citric acid cycle and be used to generate ATP. In liver, two acetylCoA molecules can also combine to form ketones.

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Ketones are released into the blood and travel to other tissues, especially skeletal muscle.

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In this tissues, the ketones are converted back to acetyl-CoA (can now enter the citric acid cycle to produce ATP.

PROTEIN METABOLISM

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Amino acids are used primarily to synthesize needed proteins and oonly secondarily as a source of energy.

Two ways to use amino acids as source of energy: •

It can be converted into the molecules of carbohydrate metabolism, such as pyruvic acid and acetyl-CoA.

b. The amine group can be removed from the amino acid, leaving ammonia and an α-keto acid where NADH (can enter the electron-transport chain to produce ATP) is produced. – Ammonia is toxic to cells, so it is converted by liver to urea. – Keto acid can enter the citric acid cycle or can be converted into pyruvic acid, acetyl-CoA, or glucose.

METABOLIC STATES

2 Major Metabolic States: 1. Absorptive state- the period immediately after meal when nutrients are being absorbed through the intestinal wall into the circulatory and lymphatic systems. - Usually lasts about 4hours after each meal. * Glucose enters the circulation to be used by cells to provide the energy they require * The remainder of glucose is converted into glycogen or fats. * Most of the absorbed fats are deposited in adipose tissue. * Absorbed amino acids are used in protein synthesis, used for energy, or enter the liver and are converted to fats or carbohydrates.

2. Post-absorptive state- occurs late in the morning, late in the afternoon, or during the night after each absorptive state is concluded. * Glycogen stored in the liver is the first source of blood glucose which can provide glucose for about 4hours. * Blood glucose levels are maintained by the conversion of other molecules to glucose. * The glycerol from triglycerides can be converted to glucose * The fatty acids from fat can be converted to acetylCoA, moved into citric acid cycle, and used as a source of energy. This can partly eliminate the need to use glucose for energy, resulting in reduced glucose removal from the blood and maintaining blood glucose levels at homeostatic levels.