HL Chemistry - Option B: Human Biochemistry Diet & Nutrition

The Human Body & Its Requirements Nutrients – The food components which provide growth, energy, and replacement of body tissue There are SIx Groups of Nutrients – proteins carbohydrates fats/lipids vitamins minerals water

Why a Balanced Diet? Too few nutrients results in – weakness anemia muscle wasting Too many nutrients results in – obesity hypertension cardiovascular disease A balanced diet is the key to good health!

Carbohydrates Empirical formula CH 2 O Main source of energy for the human body– we cant synthesis them (only plants can) Glucose is the most common sugar, and is what we have in our blood – it is broken down during respiration to yield energy Complex sugars are combinations of other sugars Cellulose (plant storage sugar) cant be digested Fructose (found in fruits) is a 5 membered ring Excess sugar (from potatoes, bread, corn, rice, etc). is converted to fat

Fats Empirical formula CHO Provides 2x the energy per gram as carbohydrates Common in milk, cheese, butter, nuts We need about 30% of our diet to be fats Fats are esters formed from glycerol and long chain carboxylic acids Cholesterol and prostaglandins are nonsaponifiable lipids Linoleic acids are vital since they cant be synthesized by the human body

Proteins We need 20% protein in our diet Proteins are composed of C,H,N (and S) They are natural polymers made from 20 amino acids (15% of body mass!) Essential Amino Acids cant be synthesized Complete Proteins have all 10 essential amino acids Meat and eggs contain complete proteins Incomplete Proteins lack one or more essential amino acid – usually found in plants Vegetarians must combine the right plant proteins to stay healthy Used to make hormones, enzymes, and antibodies (among other things)

Vitamins Vitamins are needed in small amounts to assist enzyme function Vitamin deficiencies lead to diseases such as scurvy (too little Vitamin C) or rickets (too little Vitamin D) Vitamins decompose under high heat or with prolonged cooking Balanced diets are vitamin complete, but some foods are enriched: milk –Vitamin D margarine – vitamin A flour – Vitamin B juices – Vitamin C

Fat vs. Water Solubility of Vitamins Vitamins A & D have only one –OH group plus long chain hydrocarbons, thus, they are soluble in non-polar solvents (such as fats) Other fat soluble vitamins include Vitamins E & K Since fat soluble vitamins are stored, we do not need to consume them every day The 8 Vitamin Bs and Vitamin C contain many –OH groups, and are water soluble Water soluble vitamins must be consumed every day since they cant be stored

Vitamin A (retinol) Conjugated double bonds make Vitamin A light sensitive Conformation changes result in vision Lack of Vitamin A results in night blindness, dry skin, lack of membrane secretion, dry eyes, and blindness in children

Vitamin D Serves to maintain bones and regulate calcium and phosphorus metabolism Vitamin D deficiency (rickets) is characterized by bone loss in the ribs & skull Excess Vitamin D leads to calcium deposits in the heart and liver

Vitamin C (Ascorbic Acid) Helps maintain collagen, aids in formation of bones & teeth, and assists in iron absorption from foods Scurvy results in bleeding gums and tooth & bone loss

Minerals Common minerals are Ca, Mg, and P There are many other ionic micronutrients such as Fe, I, Na, etc. Form bones and teeth Aid in the function of hormones, enzymes, and maintaining fluid electrolyte levels Diseases from lack of minerals include: osteoporosis – lack of Ca anemia – lack of Fe Goiter – lack of I Muscle cramps – lack of Na

More Examples of Metal Ion Function Charge density, redox properties, and complex ion formation determine how a metal ion functions in vivo Ca +2 is the most common ion: kg present Mg +2, K +1, Na +1 ions are found in fluids and around cells Zn +2 is found in over 100 enzymes Co +3 is found in vitamin B 12 Fe +2 is present in hemoglobin Mn ions are used in bone metabolism, and Cr ions are used for glucose metabolism Coordinate covalent bonds between metals and nitrogen containing ligands are the basis of many biological interactions

Hemoglobin Fe +2 exists in a hydrophobic environment (porphyrin ring), so when oxygen binds the metal does not change to Fe +3 The Fe +2 complex binds oxygen to form oxyhemoglobin, which delivers the oxygen to the cells via the circulatory system Binding of CO to Hemoglobin is reversible, but some poisons such as HCN or OsO 4 can not be reversed Carbon Dioxide is waste product carried in the blood as forms of carbonic acids to the lungs where it is eliminated from the body:

Porphyrin Ring and Heme Group Structures of Hemoglobin Example of a multidentate ligand called porphyrin

Hemoglobin Tube Model showing 4 domains (top left) Ribbon Model showing 4 domains and the iron and haem groups (bottom right)

The Na + /K + Pump Na +1 /K +1 ions are responsible for the transmission of nerve impulses (Na +1 outside the cell & K +1 inside), controlling cell volume, and driving active transport across the cell membrane Mechanism of Action: Transmembrane ATPase binds with three Na +1 ions plus one ATP on the inside of the cell ATP becomes ADP and the ATPase is phosphorylated An ATPase conformation change releases the three Na +1 ions on the outside of the cell The ATPase then binds two K +1 ions on the outside of the cell The ATPase dephosphorylates, the conformation again changes, and the two K +1 ions are released on the inside of the cell (The uneven distribution of cation charges across the cell membrane is responsible for nerve impulse transmission)

Adenosine Triphosphate (energy is stored in the third phosphate bond)

Nerve Impulse Transmission The transmission of nerve impulses by the Na + /K + Pump is an electrochemical process A section of cell membrane is depolarized in response to a physical-chemical stimulus The depolarization moves down the nerve fiber (axon) of a nerve cell and is transmitted to other nerve cells Na +1 ion channels open during the propagation to allow sodium ions to rush into the cell A fraction of a second later the membrane repolarizes by pumping the Na +1 ions back out of the cell The right amount of Na +1 and K +1 ions inside and outside of the cell is thus essential for nerve impulse transmission

Cytochromes Cytochromes are iron & copper containing transmembrane proteins that transport electrons and result in the formation of ATP Iron & copper atoms undergo aerobic single electron RedOx reactions: NADH carries H +1 ions and electrons away from the metals to form water and energy (stored as ATP): This series of reactions uses many enzymes

NAD + (oxidized form) & NADH (reduced form)

Water Comprises 70% of body mass Dissolves most of the chemicals in our body Water is taken in as fluids and as part of foods Humans need about 1 – 1.5 liters of water per day The intake and output of water must be regulated to maintain electrolyte balance

Energy from Food The caloric value of food can be calculated from the enthalpy of combustion obtained from calorimeters Oxidation of fats, carbohydrates, and proteins produces CO 2 and water Metabolism is the sum of all chemical reactions our bodies perform to produce the materials we need The government requires recommended daily allowances (RDA) be published on all food packages

Sample Calculation #1 A large apple weighs 150 g. If a 15 g sample of the apple is completely combusted, the temperature of 200 g of calorimeter water raises by 45.3° C. The heat capacity of the calorimeter is 89.1 J/°C and the specific heat of water is J/g-° C. What is the caloric value of the apple? ΔH = heat absorbed by water + heat absorbed by calorimeter ΔH = (m x C x ΔT) water + (C x ΔT) calorimeter ΔH = (200 g x J/g-°C X 45.3 °C) + (89.1 J/°C x 45.3 C) ΔH = J ΔH = J x (1 cal/4.184 J) ΔH = cal ΔH = cal x ( 1 Cal/1000 cal) ΔH = 10 nutritional calories (Cal) ΔH = (10 Cal/15 g of apple) x (150 g of apple) ΔH = 100 Cal

Sample Calculation #2 A person eats a meal consisting of 10 g of fat, 20 g of carbohydrate, and 10 g of protein. Given that fat = 9 Cal/g, carbohydrate = 4 Cal/g, and proteins = 4 Cal/g. How many nutritional calories (Cal) did this person consume? ΔH = (m x c) fat + (m x c) carbohydrate + (m x c) protein ΔH = (10 g x 9 Cal/g) + (20 g x 4 Cal/g) + (10 g x 4 Cal/g) ΔH = 210 Cal You do NOT need to memorize any numbers – just be able to do the calculation if asked!

Genetically Modified Foods A Genetically Modified Organism (GMO) is a living creature with a gene inserted into its DNA from another organism Both animals and plants can be modified to produce more food, be more resistant to disease, and supply nutrients or chemicals not normally found in the host Some people are concerned that the GMOs could take over the wild types if they escape into the environment Superweeds that harm birds and insects are also concerns