Human Biology: Chemistry of Life

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Human Biology Chemistry of Life

• Chapter 2

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Basic Chemistry

• Matter something that has mass and occupies
  space
• All matter composed of elements
• An element is the smallest substance that
  possesses uniqueness
• Important elements (to humans) C, H, O, N Mg,
  P, S, Na, Ca, K, I, Fe, Cl

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Atomic structure

• Elements are composed of atoms
• Three particles
• Protons have a positive charge
• Neutrons have no charge
• Electrons have a negative charge

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• Protons and neutrons located in the nucleus
• By far, possess the most mass of the atom
• Electrons located outside the nucleus
• The more particles an atom/element has, the
  heavier (more mass, bigger) it is

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Periodic table
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• Typically, protons electrons
• However, protons ? neutrons
• For any element, all forms will have the came
  number of protons
• Most elements have forms that have different
  numbers of neutrons (with some being radioactive)
  isotopes

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Groups of atoms

• Two or more atoms molecule
• When atoms are different, compound
• Atoms join together by forming chemical bonds.

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Bonds, chemical Bonds 001

• The electrons in the outermost layer (shell,
  orbital, cloud) interact to form bonds
• Some atoms are more stable if they lose or gain
  an electron
• The loss of an electron gives the atom a positive
  charge
• The addition of an electron gives the atom a
  negative charge

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Ionic bonds

• When an atom/molecule possesses a charge, ion
• Particles of opposite charges are attracted to
  each other ionic bond
• e.g. sodium chloride

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Bonds, chemical Bonds, 002

• Some atoms, like carbon, hang on to their
  electrons
• These types of atoms gain stability by sharing
  electrons with other atoms covalent bond
• Carbon is unique because it can form long chains
  of itself

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Bonds, chemical Bonds, 003

• Some molecules, due to their shape, possess
  partial charges.
• The ends of the molecule are charged, but the
  overall charge is neutral
• The (partially) charged ends are attracted to the
  oppositely charges ends of other molecules,
  polar bond
• e.g. water (polar bond hydrogen bond)

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Water, water, my classroom for some water!

• Because of its hydrogen (polar) bonding, water
  acts in special ways
• Water will react with charged molecules, but not
  with nonpolar (noncharged) ones
• Hydrophilic and hydrophobic (pg. 20)

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Acids and bases

• If a substance gives off H in water acid
• If a substance gives off OH- or takes up H
  base
• (Near) complete disassociations are strong acids
  and bases (HCl and NaOH)
• Neutralization reactions when strong acids and
  bases meet (or, it aint gonna be pretty!)

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pH scale

• Measures relative strengths of acids and bases
• The lower the number, the stronger the acid
• The higher the number, the stronger the base
• Neutral 7

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Buffers

• Buffers can take up H or OH- ions.
• As a result, buffers prevent large changes in pH.
• e.g. the carbonic acid (H2CO3)/bicarbonate
  (HCO3-) system, which is found in our blood.
• Carbonic acid is a weak acid
• H2CO3 ?? H HCO3-

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More

• Weak acids dont disassociate completely
• In the blood, there is both carbonic acid and
  bicarbonate ions present
• If the blood becomes too acidic (the amount of H
  ions ?), the bicarbonate ions can soak them up
  
• H HCO3- ? H2CO3

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Yet more

• If the blood becomes too basic (OH- ions ?), the
  carbonic acid can soak them up
• OH- H2CO3 ? HCO3- H2O
• Buffer systems have their limits

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Molecules of life

• Four (macro)molecules very important to life
• Proteins (amino acids) structural
• Lipids (glycerol and fatty acids) storage
• Carbohydrates (monosaccharides) NRG
• Nucleic acids (DNA, RNA) information

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Proteins

• Functions are many
• Structural connective tissue
• Hormones allow intra body communication
• Enzymes control our metabolism
• Transport especially in the blood
• Immunity antibodies

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Amino acids

• Proteins are composed of subunits called amino
  acids (aa)
• All amino acids (in the human body) share a
  similar structure
• Humans require 20 different aa, 8 of which need
  to come from our food

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Structure

• Amino acids link together (by covalent bonding)
  to form (polypeptide) chains
• The different combinations of aa form different
  proteins
• Hydrogen bonds help stabilize a proteins shape
• High heat can cause bonds to break, thus
  denaturing (unraveling) the protein

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Carbs (not evil!!!)

• Long chains of carbon
• Also some oxygen and hydrogens
• Quick energy and short term energy storage
• Composed of simple sugars called monosaccharides

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• Monosaccharides are ring-shaped
• Monosaccharides include glucose, fructose, and
  galactose
• Two monosaccharides bond together to form
  disaccharides

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• Disaccharides include maltose (2 glucose
  molecules), lactose (1 glucose and 1 galactose),
  and sucrose (1 glucose and 1 fructose)
• Many monosaccharides forming long chains are
  called polysaccharides starch, cellulose, and
  glycogen are good examples

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• Starch and glycogen have similar structures
• Some molecules can be 4000 glucose molecules
  long.
• These molecules are (relatively) short term
  energy storage

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Lipids (fats)

• There are several different classes of lipids
• All lipids are at least partially hydrophobic,
  and some are complete hydrophobes
• Lipids are long term energy storage. They also
  function in insulation, protection, and some
  hormones are made of lipids.

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Fats and oils

• Fats and oils are 3-carbon backbone molecules
  with 3 long carbon tails (fatty acids)

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Fatty acids

• The structure of the fatty acid tails determines
  the physical characteristics of the lipid
• If all the bonds b/t the carbon molecules are
  single, then the lipid tends to be solid at room
  temperature fats
• Also called saturated

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• If one or more carbons have double bonds, the
  tails dont pack down as much and the lipid
  tends to be liquid at room temp.
• Called mono and polyunsaturated

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Other lipids

• Phospholipids contain phosphorous and have a
  slightly different structure than triglycerides

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• Because the phosphate group contains charge,
  phospholipids will partially interact with
  charged/polar molecules such as water
• Soaps and detergents are examples of
  phospholipids
• The membranes of our cells are also phospholipids

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Steroids

• Steroids are lipids with a very different
  structure than triglycerides and phospholipids
• Steroids are 4-ringed structures
• The sex hormones (testosterone and estrogen)
  are steroid based
• Cholesterol also is important to our cellular
  membranes

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Nucleic acids

• All nucleotides have a similar structure

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• Nucleic acids are important in storing the
  genetic code
• NAs form long chains of DNA and RNA
• A modified nucleic acid, adenosine triphosphate
  (ATP), is a high energy compound used by cells

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