Water, pH, and Biological Molecules

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Chapter 3

• Water, pH, and Biological Molecules

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Targets

• Predict how a molecule will interact with water
• Define an acid and a base
• Identify substances as acids or bases based on pH
• Describe how acid rain forms and its effects

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Targets cont

• List the 4 types of organic molecules of living
  things identify the following characteristics
• Elements basic structure of each
• Building blocks (monomers) of each
• Food sources examples of each
• Function of each type in living organisms
• Reagent tests for each including vitamin C salt

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Targets cont

• Discuss the different types of fats their place
  in our diets
• Describe the role of dehydration synthesis
  hydrolysis in building up tearing down organic
  molecules

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Water

• 71 of Earth 66 of human body
• Can dissolve many substances
• Unique properties
• Ice is less dense than water
• Molecules are farther apart when a solid
• Great capacity to absorb store heat
• Great cohesive properties
• Like attracts like

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Water cont

• Polar substances dissolve best in polar
  solutions/ nonpolar substances dissolve best in
  nonpolar solutions
• Water cannot break down hydrocarbons (fats/oils)
  because they are nonpolar molecules
• Hydrophilic water loving
• Hydrophobic water fearing

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Acids Bases

• Acid contains more hydrogen than hydroxide ions
• Base (alkaline) contains more hydroxide than
  hydrogen ions
• pH scale ranges from 0-14

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pH biology

• Enzymes body catalysts that only function
  within a certain pH range
• Cell membranes will break down if there is a
  change in pH
• Buffers pH regulators help keep the pH
  constant regardless of the amount of acid or base
  added

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Carbon

• Essential for survival
• Easily forms bonds because it has 4 valence
  electrons covalent bonds (strong)
• Can form rings, branches, straight lines
• Organic chemistry study of chemistry
  encompassing carbon

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Isomers

• Def molecules that have the same molecular
  formula but different structural formula
• Glucose fructose

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Functional groups

• Def group of atoms that has a special function
  based on a carbon molecule
• Hydroxyl group OH (alcohols)
• Carboxyl group COOH
• Amino group NH2
• Phosphate group PO4
• Perform special functions define the element
• R-group denoted on structural formula can be a
  variety of different elements or molecules

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Monomers Polymers

• Monomer one small identical molecule that can
  repeat when linked together
• One glucose molecule
• Polymer many small identical molecules linked
  together to form a large molecule
• Many glucose molecules linked together

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Carbohydrates

• Organic molecules that contain C, H, O in the
  ratio of 121
• C6H12O6
• Basic building blocks (repeating units)
  monosaccharides (saccharide sugar)
• Glucose, fructose
• Disaccharide (two sugars) in order for 2 sugars
  to combine a dehydration reaction has to occur
  (water is lost)
• Glucose glucose ? maltose water
• Polysaccharide many sugars combining by
  dehydration synthesis
• Starch, glycogen, cellulose, chitin

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Carbs cont

• Hydrolysis reversal of dehydration synthesis in
  which the water is replaced and the large
  molecule splits into smaller ones
• Maltose water ? glucose glucose

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Lipids

• Insoluble in water
• Fat, oil, cholesterol, testosterone, estrogen
• Composed of C, H, O (more H than O)
• Not composed of monomers and polymers
• Glycerides, fatty acids, steroids, phospholipids
• Glycerides
• Head composed of alcohol
• Tail hydrocarbons (H C)
• Triglyceride 3 fatty acids bonded to a glycerol
  
• Glycerol 3 fatty acids triglyceride water
  (dehydration synthesis)
• Fatty acid hydrocarbon tail with a carboxyl
  head

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Saturated Unsaturated Lipids

• Saturated fatty acid fatty acid with no double
  bonds between the carbon atoms in the hydrocarbon
  chain
• Monounsaturated fatty acid fatty acid with only
  one double bond
• Polyunsaturated fatty acid fatty acid with two
  or more double bonds
• Moving from saturated to unsaturated fats
  change into oils

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Lipids cont

• Steroids
• Class of lipids with 4 carbon rings
• Cholesterol, estrogen, testosterone
• Unique by their side chains

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Lipids cont

• Phospholipids
• Class of lipids with glycerol head, 2 fatty acid
  tails phosphate group
• Phosphate group links the head to the tail
• Divides phospholipids into hydrophilic heads
  hydrophobic tails
• Plasma membranes (heads point outward tails
  point inward)

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Proteins

• Building blocks amino acids(20 different)
• Amino acids central carbon bonded to H,
  carboxyl group, amino group, R-group (side
  chain)
• 2 amino acids dipeptide
• 3 or more amino acids polypeptide
• Protein when polypeptide begins folding
• Examples on page 56
• To join carboxyl joins amino group through
  condensation reaction

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Protein Shape

• Protein conformation is crucial to function
• Enzymes speed up chemical reactions catalysts
  found in human body
• Work like puzzle pieces
• Reactant substrate
• Primary structure sequence of amino acids

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Protein Shape cont

• Secondary structure beta pleated sheet
  (accordion) alpha helix (corkscrew) random coil
• Tertiary structure folded polypeptide chain
• Quaternary structure 2 or more polypeptide
  chains
• Proteins can lose shape due to pH change

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Proteins

• Lipoproteins combination of lipids and proteins
• LDLs low-density lipoproteins (lipid less dense
  than proteins)
• Bad cause plaque in arteries around heart
• HDLs high-density lipoproteins (lipids more
  dense than proteins)
• Healthy

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Proteins

• Glycoproteins combination of proteins
  carbohydrates
• Help combine receptors and substrates

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Nucleotides Nucleic Acids

• Nucleic Acids
• DNA (deoxyribonucleic acid)
• RNA (ribonucleic acid)
• ATP (adenosine triphosphate) cellular energy
• Nucleotides building blocks

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Nucleic Acids

• DNA contains hereditary information in cells
  double helix
• Composed of nucleotides
• Phosphate group sugar (deoxyribose) nitrogenous
  base
• RNA actively involved in the making of
  proteins single stranded
• Composed of nucleotides
• Phosphate group sugar (ribose) nitrogenous base

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