Chemistry 115

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Chemistry 115 Lecture 27 Outline Chapter
12 Carbohydrates and lipids Proteins Recitation
QUIZ Chapter 12 and 15,
functional groups, IMFs
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Chemistry and Biochemistry

• Where weve been
• ionic and covalent bonding
• molecular shape
• intermolecular forces
• organic functional groups
• Where were going
• Types of biochemical molecules
• How bonding and IMFs determine shape
• How shape determines biological function
• amino acids / proteins / nucleic acids

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Calories
Fats, 9 Calories per gram Carbohydrates, 4
Calories per gram. 1 Calorie (the nutritional
calorie) 1000 calories (thermochemical
calories) 4184 J Why are fats so energy
intensive relative to carbs?
Before we can answer that we need to know What
are fats? What are carbohydrates?
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Lipids fats
Fats are esters of carboxylic acids glycerine
CH2(OH)CH2(OH)CH2(OH)
Flipped structure
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Cis trans fatty acids
Metabolic studies have shown that trans fats have
adverse effects on blood lipid levels--increasing
LDL ("bad") cholesterol while decreasing HDL
("good") cholesterol. This combined effect on the
ratio of LDL to HDL cholesterol is double that of
saturated fatty acids.
Stearic acid (saturated)
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Zero calorie fat Olestra
Glycerine Stearic acid
Sucrose
Fat Olestra
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Carbohydrates
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Carbohydrates
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Small carbohydrate molecules Sugars
Preferred structural form may be that of a cyclic
molecule -- five and six-membered rings are
favored and may be joined into chains. Sugars
5 6 atom cyclic units are most common
Glucose
Sucrose
Lactose
Fructose
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Small carbohydrate molecules Sugars
Preferred structural form may be that of a cyclic
molecule -- five and six-membered rings are
favored and may be joined into chains. The
rings in sugars are not planar (flat)
Glucose
Because there are several ways to arrange the OH
groups, there are several sugars with 6-membered
rings.
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Cellulose starch
Starch and cellulose are two biopolymers that are
made from sugar rings.
Cellulose Insoluble Indigestible
Starch Slightly soluble Digestible
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Heats of combustion Fat vs carb
CH3(CH2)14CO2H 24 O2 ? 16 CO2 16 H2O
?H -10,071 kJ / mol (9.4 Kcal /
g) C6H12O6 O2 ? 6 CO2 6 H2O
?H -2830 kJ / Mol
(3.8 kCal / g)
Although our bodies do not burn fat or sugar,
the overall series of steps that converts fat
plus O2 into CO2 and H2O produces the same amount
of energy as burning the fat or sugar.
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Other Lipids Cellular Membranes

• Cellular membranes are made of phospholipid
  molecules.
• Like soaps, these molecules have an ionic/polar
  end and a long non-polar region.

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Cellular Membrane

• Cellular membranes are composed of a phospholipid
  bilayer
• with the polar side facing the aqueous
  environments inside and outside the cell, and the
  nonpolar ends comprising the inside of the
  bilayer.

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Cellular Membrane
Movement through a cell membrane will depend on
the polar/non-polar characteristics of proteins
and other molecules. For example, glucose and
fructose serve as basic fuel molecules for
eukaryotic cells. These molecules are unable to
diffuse across cellular membranes. How do
molecules like glucose, which are polar, pass
through the cell membrane, which is hydrocarbon
like?
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Cellular Membrane
Molecules that are unable to diffuse across
cellular membranes, require transporter proteins
for entry into and exit from cells.
H-bonding
H-bonding
Non-polar
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Cellular Membrane
Cell membranes can be altered by drugs, viruses
to stop or propagate cell activity and even
disease.
Antibiotic Gramicidin A (Neosporin) is nonpolar
on the outside, and polar on the inside.
Disrupts ion balance to kill the bacteria.
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Proteins The Big Picture

• 3-D structure determines FUNCTION (properties,
  behavior)
• Even complex shapes and functions depend on the
  fundamental intermolecular forces
• Proteins are polymers of amino acids
• Amino acids have an amine end, a carboxylic acid
  end, and another functional group that varies.

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Proteins

• Proteins are essential parts of all living
  organisms and participate in every process within
  cells. Activities include
• catalysis of biochemical reactions by enzimes
• structural or mechanical functions, proteins in
  the cytoskeleton, form a system of scaffolding
  that maintains cell shape.
• transport of other bio-molecules
• cell signaling
• immune responses
• cell adhesion and cell division
• Proteins are a necessary component in our diet,
  since animals can not synthesize all the amino
  acids and must obtain essential amino acids from
  food.

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Amino Acids
Proteins are made up of amino acids

• The basic structure of an amino acid

R commonly one of 20 different side groups
carboxylic acid
amine
Proteins consist of chains of amino acids.
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Physiological Form of Amino Acids

• At physiological pH inside the cell, the amino
  acids exist in their ionized form.

This is referred to as a zwitterion, having two
opposite charges on the same molecule.
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The common amino acids
Figure 15.28
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Peptide Bonds

• Amino acids link together through a peptide
  bond
• Two amino acids ? dipeptide
• Many amino acids ? polypeptide

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Structure of Proteins
Proteins can also be thought of as a type of
biopolymer

• Primary sequence of amino acids

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Structure of Proteins

• Primary sequence of amino acids
• Secondary spatial arrangement of the polypeptide
  into shapes such as sheets or helices

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Structure of Proteins

• Primary sequence of amino acids
• Secondary spatial arrangement of the polypeptide
  into shapes such as sheets or helices
• Tertiary overall 3-D
• shape of a polypeptide
• chain

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Tertiary Structure

• Intermolecular forces help to determine
  tertiary structure
• Placement of polar groups outside and nonpolar
  groups inside (for an aqueous environment)

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Structure of Proteins

• Primary sequence of amino acids
• Secondary spatial arrangement of the polypeptide
  into shapes such as sheets or helices
• Tertiary overall 3-D
• shape of a polypeptide
• chain
• Quaternary arrangement of two or more
  polypeptide chains in the protein

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Quaternary Structure

• Hemoglobin 4 stranded protein

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Two types of proteinsGlobular and Fiberous
Ribbon diagram of the enzyme TIM, surrounded by
the transparent space-filling model of the
protein. TIM is an extremely efficient enzyme
involved in the process that converts sugars to
energy in the body.
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Globular Proteins
Ribbon model of the enzyme papain showing the two
domains and the cleft between them. The cleft
acts as the active site of the enzyme which
breaks the peptide bonds in other proteins.
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Sugar and Enzyme
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Fiberous proteinsKeratin and Collagenstructural
proteins for hair and skin
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Curly Hair and Di-sulfide Bonds

• Keratin has cysteine components