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The Amazing Molecule: Water
All living things are made of chemicals.
Understanding life requires an understanding of chemistry.
Biochemistry- the chemistry of life helps us understand todays biological questions!
Covers 75% of the earths surface
Single most abundant compound in all living things
Average male = 60% water
Average female = 50% water
Average infant = 73% water
H2O
Neutral Molecule
10 protons
10 electrons
With 8 protons in its nucleus, an oxygen atom has a much stronger attraction for electrons than does a hydrogen atom with its single proton.
The oxygen end of the molecule has a slight negative charge and the hydrogen end of the molecule has a slight positive charge
The attraction between a hydrogen atom on one water molecule and the oxygen atom
Because of their partial positive and negative charges, polar molecules such as water can attract each other.
Cohesion
Adhesion
Surface tension
High Heat of Vaporization
Universal Solvent
Facilitate Chemical Reactions
water molecules are drawn together, which is why drops of water form beads on a smooth surface.
Cohesion also produces surface tension, explaining why some insects and spiders can walk on a pond’s surface.
attraction between molecules of different substances.
a meniscus: because the adhesion between water molecules and glass molecules is stronger than the cohesion between water molecules.
A result of Cohesion
explaining why some insects and spiders can walk on a pond’s surface
large amount of heat energy is needed to cause those molecules to move faster and raise the temperature of the water until becomes vapor
Large bodies of water (oceans and lakes) can absorb large amounts of heat with only small changes in temperature. This protects organisms living within from drastic changes in temperature
Honor’s Biology
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Although a cell is mostly water, the rest of the cell consists mostly of carbon-based molecules
Organic chemistry is the study of carbon compounds that are necessary for life
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It has four electrons in an outer shell that holds eight
Carbon can share its electrons with other atoms to form up to four covalent bonds
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Attach to other carbons
Form an endless diversity of carbon skeletons
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Large molecules are called polymers
Polymers are built from smaller molecules called monomers
Biologists call them macromolecules
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Proteins
Lipids
Carbohydrates
Nucleic Acids
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Polymers are made by stringing together many smaller molecules called monomers
Nucleic Acid Monomer
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Cells link monomers by a process called dehydration synthesis (removing a
molecule of water)
This process joins two sugar monomers to make a double sugar
Remove
H
Remove OH
H2O Forms
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Also called “condensation reaction”
Forms polymers by combining monomers by “removing water”.
HO H
HO HO H H
H2O
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Cells break down macromolecules by a process called hydrolysis (adding a molecule of water)
Water added to split a double sugar
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Separates monomers by “adding water”
HO HO H H
HO H
H2O
Carbohydrates: Made up of monosaccharides
Lipids: Made up of glycerol and fatty acid molecules
Proteins: Made up of Amino acids
Nucleic acids: Made up of nucleotides
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Carbohydrates are made up of
simple sugars (monosaccharides):
Small sugar molecules in soft drinks
Long starch molecules in pasta and potatoes
Copyright Cmassengale
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CHO Examples: A. monosaccharide B. disaccharide C. polysaccharide
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Monosaccharide: one sugar unit
Examples: Glucose (C6H12O6)
Fructose
Galactose glucose
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Glucose is found in sports drinks
Fructose is found in fruits
Galactose is called “milk sugar”
-OSE ending means SUGAR
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Glucose & fructose are isomers because their structures are different, but their chemical formulas are the same
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Disaccharide: two sugar unit
Examples: Sucrose (glucose+fructose)
Lactose (glucose+galactose)
Maltose (glucose+glucose)
glucose glucose
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A disaccharide is a double sugar
They’re made by joining two monosaccharides
Involves removing a water molecule (dehydration synthesis)
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Polysaccharide: many sugar units
Examples: starch (bread, potatoes)
glycogen (stored in liver)
cellulose (lettuce, corn)
glucose glucose
glucose glucose
glucose glucose
glucose glucose
cellulose
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Complex carbohydrates
Composed of many sugar monomers linked together
Polymers of monosaccharide chains
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Starch
Glycogen
Cellulose
Glucose Monomer
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Starch is an example of a polysaccharide in plants
Plant cells store starch for energy
Potatoes and grains are major sources of starch in the human diet
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Glycogen is an example of a polysaccharide in animals
Animals store excess sugar in the form of glycogen
Glycogen is similar in structure to starch because BOTH are made of glucose monomers
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Cellulose is the most abundant organic compound on Earth It forms cable-like fibrils in the tough walls that enclose plants
It is a major component of wood
It is also known as dietary fiber
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SUGARS
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Most animals cannot derive nutrition from fiber
They have bacteria in their digestive tracts that can break down cellulose
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Simple sugars and double sugars dissolve readily in water
They are hydrophilic, or “water-loving”
WATER MOLECULE
SUGAR MOLECULE
-OH groups make them water soluble
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Lipids are hydrophobic –”water fearing”
CHO
Do NOT mix with water
FAT MOLECULE
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General term for compounds which are not soluble in water.
Lipids are soluble in hydrophobic solvents. “stores the most energy”
Examples: 1. Fats 2. Phospholipids 3. Oils 4. Waxes 5. Steroid hormones 6. Triglycerides
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Five functions of lipids:
1. Long term energy storage
2. Protection against heat loss (insulation)
3. Protection against physical shock
4. Chemical messengers (hormones)
5. Major component of membranes (phospholipids)
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Triglycerides: composed of 1 glycerol and 3 fatty acids.
H
H-C----O
H-C----O
H-C----O
H
glycerol
O
C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
fatty acids
O
C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3
O
C-CH2-CH2-CH2-CH
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Glycerol Fatty Acid Chains
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Unsaturated fatty acids have less than the maximum number of hydrogens bonded to the carbons (a double bond between carbons)
Saturated fatty acids have the maximum number of hydrogens bonded to the carbons (all single bonds between carbons)
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Single
Bonds in
Carbon
chain
Double bond in carbon
chain
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Most animal fats have a high proportion of saturated fatty acids & exist as solids at room temperature (butter, margarine, shortening)
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Most plant oils tend to be low in saturated fatty acids & exist as liquids at room temperature (oils)
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Dietary fat consists largely of the molecule triglyceride composed of glycerol and three fatty acid chains
Glycerol
Fatty Acid Chain
Condensation links the fatty acids to Glycerol
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• Cell membranes are made of lipids called phospholipids
• Phospholipids have a head that is polar & attract water (hydrophilic)
• Phospholipids also have 2 tails that are nonpolar and do not attract water (hydrophobic)
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The carbon skeleton of steroids is bent to form 4 fused rings
Cholesterol is the “base steroid” from which your body produces other steroids
Estrogen & testosterone are also steroids
Cholesterol
Testosterone
Estrogen
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Proteins are polymers made of monomers called amino acids
CHONS
All proteins are made of 20 different amino
acids linked in different orders
Proteins are used to build cells, act as
hormones & enzymes, and do much of the
work in a cell
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Amino acids have a central carbon with 4 things boded to it:
Amino group –NH2
Carboxyl group -COOH
Hydrogen -H
Variable group -R
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Cells link amino acids together to make proteins
The process is called
dehydration synthesis
Peptide bonds form
to hold the amino
acids together
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Four levels of protein structure:
A. Primary Structure
B. Secondary Structure
C. Tertiary Structure
D. Quaternary Structure
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Hydrogen bond
Hydrogen bond
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Amino acids bonded together by peptide bonds (straight chains)
aa1 aa2 aa3 aa4 aa5 aa6
Peptide Bonds
Amino Acids (aa)
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The primary
structure is the
specific sequence
of amino acids in
a protein
Called
polypeptide
Amino Acid
Secondary protein structures occur when protein chains coil or fold
Coil – alpha helix
Fold – beta sheet
Results from hydrogen bonds
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Secondary structures bent and folded into a more complex 3-D arrangement of linked polypeptides
Bonds: H-bonds, ionic, disulfide bridges (S-S)
Call a “subunit”.
Alpha Helix
Beta Pleated Sheet
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Composed of 2 or more “subunits” Globular in shape Form in Aqueous environments Example: enzymes (hemoglobin)
subunits
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Substitution of one amino acid for another in
hemoglobin causes sickle-cell disease
(a) Normal red blood cell Normal hemoglobin
1 2 3
4 5
6 7. . . 146
(b) Sickled red blood cell Sickle-cell hemoglobin
2 3 1
4 5
6 7. . . 146
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Blood sugar level is controlled by a protein called insulin
Insulin causes the liver to uptake and store excess sugar as Glycogen
The cell membrane also contains proteins Receptor proteins help cells recognize
other cells
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INSULIN
Cell membrane with proteins &
phospholipids
Enzymes are an important class of catalysts in living organisms Mostly protein
Thousands of different kinds
Each specific for a different chemical reaction
Often end in ase (lactase breaks down lactose)
Enzymes work on substances called substrates
Substrates must fit into a place on an enzyme called the active site
Enzymes are reusable!
The lactase enzyme breaks the bond between glucose and galactose so you can digest lactose (milk).
Lactose free milk contains the same sugars but they are already broken down = easier to digest for those lactose intolerant.
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Nucleic acids are composed of long chains of nucleotides linked by dehydration synthesis.
CHONP
Function: Dictate amino acid sequences/how proteins are made
Source of all genetic information
Two types:
a. Deoxyribonucleic acid (DNA)
b. Ribonucleic acid (RNA)
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O
O=P-O
O
Phosphate
Group
N
Nitrogenous
base
(A, G, C, or T)
CH2
O
C1 C4
C3 C2
5
Sugar
(deoxyribose)
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Nitrogenous base (A,G,C, or T)
Phosphate group
Thymine (T)
Sugar (deoxyribose)
Phosphate
Base
Sugar
Nucleic acids
are polymers of
nucleotides
Nucleotide
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Nucleotides include: phosphate group pentose sugar (5-carbon) nitrogen bases: adenine (A) thymine (T) DNA only uracil (U) RNA only cytosine (C) guanine (G)
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Each DNA nucleotide has one of the following bases:
Thymine (T) Cytosine (C)
Adenine (A) Guanine (G)
–Adenine (A)
–Guanine (G)
–Thymine (T)
–Cytosine (C)
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Two strands of DNA join together to form a double helix
Base pair
Double helix
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P
P
P
O
O
O
1
2 3
4
5
5
3
3
5
P
P
P O
O
O
1
2 3
4
5
5
3
5
3
G C
T A
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Ribose sugar has an extra –OH or hydroxyl group
base uracil (U) instead
of thymine (T)
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ATP is used by cells for energy
Adenosine triphosphate
Made of a nucleotide with 3 phosphate groups
Organic Compounds Lab
A substance used to show the presence of another substance
Color change = positive test
(the substance is present)
Use it as a control – to make sure the indicators are working.
No color change with water = indicators are working
Sudan III stain – red is a positive test
Brown paper bag – Lipids leave translucent spots (grease spots)
Starch – Iodine- blue/black is a positive test
Sugar – Benedict’s solution – **MUST BE HEATED!!!!*
blue/green changes to orange/yellow = positive test
Biuret reagent - varying shades of purple = positive test
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