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 –proteinscarbohydratesfats/lipidsvitaminsmineralswater

Why a Balanced Diet?• Too few nutrients results in –

weaknessanemiamuscle wasting

• Too many nutrients results in – obesityhypertensioncardiovascular disease

A balanced diet is the key to good health!

Carbohydrates• Empirical formula CH2O• Main source of energy for the human body– we

can’t 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) can’t 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 can’t 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” can’t 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 Dmargarine – vitamin A

flour – Vitamin Bjuices – 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 B’s and Vitamin C contain many –OH groups, and are water soluble

• Water soluble vitamins must be consumed every day since they can’t 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

C C

C C

C C C C

C C

C C

C C

C C C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

C C

O O

H H

H H

H H H H

H H

H H

H H H H

H H

H H

H H

H H H H

H H

H H

H H

H H

H H

H H

H H

H H

H H H H

H H

H H

H H

H H

H H

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

O O

H H

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

C C C C

C C

O O

O O

C C

C C

C C

O O

O O

O O

O O

H H

H H H H

H H

H H

H H

H H

H H

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 Caanemia – lack of FeGoiter – lack of IMuscle 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: 1-1.5 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 B12

• 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 OsO4 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:

CO H O H + HCO2 g 2 (l)+1

aq) 3-1

(aq)( ) (

Porphyrin Ring and Heme Group Structures of Hemoglobin

Example of a multidentate ligand called porphyrin

HemoglobinTube 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

Fe Fe + e+2 +3 - Cu Cu + e+1 +2 -

4e + 4H + O 2H O + energy- +1(aq) 2 g 2 (l)( )

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 CO2 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 #1A 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 4.184 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 4.184 J/g-°C X 45.3 °C) + (89.1 J/°C x 45.3 C)

ΔH =41 943 J

ΔH = 41 943 J x (1 cal/4.184 J)

ΔH = 10 025 cal

ΔH = 10 025 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 #2A 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 GMO’s could take over the wild types if they escape into the environment

• “Superweeds” that harm birds and insects are also concerns