HL Chemistry - Option B : Human Biochemistry

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HL Chemistry - Option B Human Biochemistry

• Diet Nutrition

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The Human Body Its Requirements

• Nutrients
• The food components which provide growth,
  energy, and replacement of body tissue
• There are 6 groups of nutrients
• proteins
• carbohydrates
• fats/lipids
• vitamins
• minerals
• water

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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!

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Carbohydrates

• Empirical formula CH2O
• 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

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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

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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)

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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

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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

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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

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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

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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

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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

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More Examples of Metal Ion Function

• Charge density, redox properties, and complex ion
  formation determine how a metal ion functions in
  vivo
• Ca2 is the most common ion 1-1.5 kg present
• Mg2, K1, Na1 ions are found in fluids and
  around cells
• Zn2 is found in over 100 enzymes
• Co3 is found in vitamin B12
• Fe2 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

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Hemoglobin

• Fe2 exists in a hydrophobic environment
  (porphyrin ring), so when oxygen binds the metal
  does not change to Fe3
• The Fe2 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

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Porphyrin ring and heme group structures of
hemoglobin.
Example of a multidentate ligand called porphyrin.
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HemoglobinTube Model showing 4 domains (top
left)Ribbon Model showing 4 domains and the
iron and haem groups (bottom right)
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The Na/K Pump

• Na1/K1 ions are responsible for the
  transmission of nerve impulses (Na1 outside the
  cell K1 inside), controlling cell volume, and
  driving active transport across the cell membrane
• Mechanism of Action
• Transmembrane ATPase binds with three Na1 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
  Na1 ions on the outside of the cell
• The ATPase then binds two K1 ions on the outside
  of the cell
• The ATPase dephosphorylates, the conformation
  again changes, and the two K1 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)

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Adenosine Triphosphate(energy is stored in the
third phosphate bond)
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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
• Na1 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 Na1 ions back out of
  the cell
• The right amount of Na1 and K1 ions inside and
  outside of the cell is thus essential for nerve
  impulse transmission

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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 H1 ions and electrons away from the
  metals to form water and energy (stored as ATP)
• This series of reactions uses many enzymes

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NADH (reduced form) NAD (oxidized form)
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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

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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

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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?

• ?H heat absorbed by water heat absorbed by
  calorimeter
• ?H (m x C x ?T)water (C x ?T)calorimeter
• ?H (200 g x 4.184 J/g-C X 45.3 C) (89.1 J/C
  x 45.3 C)
• ?H 41 943 J
• ?H 41 943 J x (1 cal/4.184 J)
• ?H 10 025 cal
• ?H 10 025 cal x ( 1 Cal/1000 cal)
• ?H 10 nutritional calories (Cal)
• ?H (10 Cal/15 g of apple) x (150 g of apple)
• ?H 100 Cal

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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?

• ?H (m x c)fat (m x c)carbohydrate (m x
  c)protein
• ?H (10 g x 9 Cal/g) (20 g x 4 Cal/g) (10 g
  x 4 Cal/g)
• ?H 210 Cal
• You will be provided with a table showing the
  various caloric values mentioned here for a
  variety of foods should this problem come up on
  the HL Chem. exam
• Thus, you do NOT need to memorize any numbers
  just be able to do the calculation if asked!

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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