Biological Molecules

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Chapter 3

• Biological Molecules

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Life is built from select elements

• Most abundant
• Carbon
• Hydrogen
• Oxygen
• Nitrogen
• Calcium
• Phosphorus

• Less prominent, but still critical
• Sodium
• Potassium
• Iron
• Chlorine
• Magnesium

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Biological Molecules

• Relatively large combinations of atoms of these
  elements
• Many are necessary for life because the breaking
  and forming of new bonds provides energy
• Molecular building blocks

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Carbon

• Biological molecules are built around carbon (C)
• Important because it has four valence electrons
• Can form up to four single bonds with other
  elements/molecules

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Terms associated with Carbon

• Hydrocarbon
• A molecule whereby carbon is bonded ONLY with
  hydrogen atoms
• Examples include
• Methane
• Butane
• Octane

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Methane Molecule
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Carbon bonds

• Carbon-Carbon bonds release a lot of energy when
  broken
• Molecules made of carbon and hydrogen burn easily
  at room temperature

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Functional Groups

• Required to know
• Hydroxyl
• Carboxyls
• Phosphates
• Amino groups

• All of these groups are POLAR, although the
  degree of polarity varies
• Any of these may be prominent features of organic
  compounds

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Hydroxyl

• Comprised only of oxygen and hydrogen
• Polar, so it is likely to attach to a polar
  region on molecules
• Cause molecules to form hydrogen bonds, and may
  dissolve completely in water

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Carboxyl

• Composed of carbon, oxygen, and hydrogen
• Polar, quickly gives up the hydrogen (becomes an
  ion) and makes the solution acidic
• Molecules with this group also called carboxylic
  acids

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Phosphate

• The only functional group with phosphorus
• ANY of the four oxygens can bond with carbon
• Important in ATP (adenosine triphosphate)

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Adenosine triphosphate (ATP)
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Amino groups

• Composed of nitrogen and hydrogen
• NH3 is an intense gas and an effective cleaner
  for removing bacteria
• Amino groups do NOT make a molecule toxic after
  forming bonds

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REVIEW Functional Groups

• Hydroxyls
• Carboxyls
• Phosphates
• Amino groups

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Four Kinds of Biological Molecules

• Lipids
• Carbohydrates
• Nucleic Acids
• Proteins

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Lipids

• Important in the structure and formation of cell
  membranes
• Not water-soluble
• Commonly known as fats in dietary terms and in
  food labels
• Some of the most important lipids are
  phospholipids and triglycerides

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Lipids

• Carbon, oxygen, hydrogen
• Fats, oils, waxes, steroids, cholesterol
• Used for energy cell membrane structure
• Some hormones the myelin sheath around nerves
• Monomers for fats and oils fatty acids
  glycerol

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Fats and oils are triglycerides or
triacylglycerols.
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To understand lipids

• we need to know a few more molecular structures
• These structures combine with hydrocarbon chains
  in various ways, such that one end is polar.
• Despite this polarity, remember that lipids are
  not soluble in water

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Glycerol
OH OH OH
H C C C H
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Carboxyl Group
- COOH
Hydrocarbon Chain
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Triglycerides

• Formed by THREE fatty acid molecules and a
  glycerol molecule
• Triglycerides are the main storage molecules for
  lipids in the fat cells of animals

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Dehydration Synthesis
3 fatty acids glycerol
fat/oil 3 H2O
triglyceride
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Types of Fats

• Fats are important sources of energy for
  organisms
• Too many fats can create problems
• Two main types
• Saturated
• Unsaturated

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A saturated fatty acid
H H H H H H H H H
H C C C C C C C C C
H H H H H H H H H
Carboxyl group
Hydrocarbon chain
A monounsaturated fatty acid
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Carbohydrates

• Contain only carbon, hydrogen, and oxygen
• Examples sugars, starch, cellulose, glycogen,
  chitin

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Uses of carbohydrates in living things

• Supply energy
• Building materials in plant cell walls
  invertebrate exoskeletons.

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Terms with Carbohydrates

• saccharide- means sugar
• Monosaccharide
• ONE carbohydrate unit (subunit)
• Disaccharide
• TWO monosaccharides
• Polysaccharide
• TWO or more monosaccharides

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Fig. 3.5a
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Simple sugars are called monosaccharides.

• Glucose, fructose, and galactose are
  monosaccharides.

isomers
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Common Names

• Glucose blood sugar
• Fructose fruit sugar
• Sucrose table sugar
• Maltose malt sugar
• Lactose milk sugar

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Figure 3.5b
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Condensation or Dehydration Synthesis

• Unites 2 monomers
• By the removal of water
• Monosaccharide monosaccharide disaccharide
  water

Glycosidic bond in disaccharide
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Dehydration Synthesis

• Glucose Fructose ? Sucrose Water

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Beta glucose
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Dehydration Synthesis of glucose
glucose maltose water
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Dehydration Synthesis of glucose
glucose maltose water
H2O removed dehydration
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H
H
C
H
HO
C
H
HO
C
O
C
O
OH
H
H
H
H

H
C
C
C
C
H
OH
H
OH
H
HO
C
C
O
C
C
H
OH
H
OH
Glycosidic bond
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Glucose
Glucose
H

O
Maltose
Water
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Hydrolysis

Glucose
Glucose
H

O
Maltose
Water
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Hydrolysis

• Digestion is an example of hydrolysis.
• Hydrolysis water breaking apart
• Hydrolysis requires 1 molecule of water for every
  2 monomers broken apart.

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Long chains of monosaccharides form
polysaccharides.

• Common glucose polymers are starch, glycogen,
  cellulose, chitin, and pectin.

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Four Kinds of Biological Molecules

• Lipids
• Carbohydrates
• Proteins
• Amino groups/amino acids

For next week Also, read Chapter 4