Exercise 3: Chemical Composition of Cells

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Exercise 3Chemical Composition of Cells
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The 4 Macromolecules of Life

• Carbohydrates
• Lipids (Fats)
• Proteins
• Nucleic Acids
• All of the above macromolecules are Organic
  Compounds

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Organic Compounds

• The term Organic means containing the element
  Carbon and at least 1 Hydrogen atom.
• The simplest organic compounds are the
  Hydrocarbons which only contain hydrogen and
  carbon atoms.
• Other organic compounds contain one or more
  Functional Groups covalently bonded to carbon.

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Carbons Bonding Behavior

• Each carbon atom can form covalent bonds with as
  many as 4 other atoms.
• For example in the simplest organic compound,
  Methane, one carbon atom is covalently bonded to
  4 hydrogen atoms (CH4).

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Functional Groups

• Functional groups are atoms or clusters of atoms
  that function a certain way in chemical
  interactions.
• Functional groups are more reactive than the
  hydrocarbon regions of a compound.
• The common functional groups found in biological
  molecules are hydroxyl, methyl, carbonyl,
  carboxyl, amino, phosphate, and sulfhydryl.

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CARBOXYL
HYDROXYL
(nonionized COOH)
(ionized COO)
METHYL
AMINO
(nonionized NH2)
(ionized NH3)
CARBONYL
PHOSPHATE
(icon for phosphate group)
(aldehyde CHO)
(ketone CO)
SULFHYDRYL
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Example of Functional Group Importance
An Estrogen
Testosterone
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Building Macromolecules

• The major building blocks of the 4 major
  macromolecules are simple sugars, amino acids,
  nucleotides, fatty acids, and glycerol.
• Cells take these monomers and link them together
  to form polymers.
• The polymers can like wise be broken down into
  monomers which can be used for energy or returned
  to the cellular pools.

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Condensation


enzyme action at functional groups
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Cleavage (Hydrolysis)
enzyme action at functional groups


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Carbohydrates

• Carbohydrates are the most abundant biological
  macromolecule.
• Most carbohydrates consist of Carbon, Hydrogen,
  and Oxygen in a 121 ratio (CH2O)n
• Carbohydrates are used as
• Structural materials
• Transportable and storage forms of energy
• Cell recognition

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Carbohydrates

• All carbohydrates are composed of polymers of
  Saccharides.
• There are 3 main classes of carbohydrates
• Monosaccharide one sugar monomer
• Oligosaccharides 2 to 20 sugar monomers
• Polysaccharides 20 sugar monomers
• In oligosaccharides and polysaccharides the
  carbonhydrogenoxygen ratio may not be 121
  because water is lost during polymer formation.

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Monosaccharide
Structure of glucose
Structure of fructose
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Oligosaccharides

glucose
fructose
H2O
sucrose
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Polysaccharides
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Polysaccharides
Cellulose (Fiber)
glycogen
amylose (a starch)
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Carbohydrate Energy Yield

• Oligosaccharides and polysaccharides are broken
  down to monosaccharide units that are then used
  as energy.
• 1 gram of carbohydrate releases 4 calories of
  energy.
• Excess carbohydrates are stored as glycogen
  and/or converted into Lipid and stored as fat.

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Test for Carbohydrates

• Starch test Iodine test
• Positive Blue-black
• Negative Yellow-brown
• Sugar test Benedicts test
• Positive Green to red-orange
• Negative - Blue

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Lipids (FAT)

• Lipids are non-polar hydrocarbons.
• In general, Lipids are composed of 1, 2, or 3
  Fatty Acids attached to Glycerol (Cholesterol is
  the exception).
• Lipids are used as
• Energy stores
• Structural materials
• Signaling molecules
• Insulation

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Glycerol
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Fatty Acids
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glycerol
3H20

Three fatty-acid tails
Triglyceride
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Phospholipid
hydrophilic head
two hydrophobic tails
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Sterols
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Lipid Energy Yield

• Lipids are broken down into glycerol and fatty
  acids and when used as energy.
• 1 gram of Lipid (FAT) releases 9 calories of
  energy.
• Excess lipids are stored in adipose tissue (fat
  cells).

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Lipid Test

• Paper evaporation test
• Emulsification test

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Protein

• Proteins are the most diverse biological
  macromolecules.
• Proteins are composed of polymers of amino acids.
• Proteins are used as
• Enzymes
• Structural material
• Transporters
• Energy stores
• Hormones
• Antibodies
• Neurotransmitters

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Amino Acid
Amino group (basic)
Carboxyl group (acidic)
R group (20 kinds with distinct properties)
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The Peptide Bond

H2O
http//chemistry2.csudh.edu/rpendarvis/aminoacids.
htmlpeptide
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Protein Structure

• Proper protein structure at all levels is
  required for proper function.
• The disruption of a proteins normal structure is
  called Denaturation.
• Denaturation can be caused by heat, extreme pH
  and UV radiation.
• Sometimes denaturation can be reversed.
  Sometimes it cannot. (cooked egg)

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Protein Energy Yield

• Proteins are broken down into amino acids when
  used as energy.
• 1 gram of protein releases 4 calories of energy.

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Protein Test

• Biuret test
• Positive Pinkish-Purple to Purple
• Negative - Blue