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CHAPTER 3: THE CHEMISTRY OF LIFE
The Structure and Function of Large Biomolecules
Intro Recap
Essential Elements - CHONPS Carbon Hydrogen Oxygen Nitrogen Phosphorus Sulfur
Make up the 4 major molecules in your body Carbs Proteins Lipids Nucleic acids
Macromolecules
Huge molecules made of many smaller molecules and atoms Carbohydrates Proteins Nucleic Acids
Lipids don’t count!
Polymers and Monomers
mono = one Subunits of
polymer
poly = many One polymer is
made up of many monomers bonded together
Monomer Polymer
Sugar
Sugar
Sugar
Sugar
Dehydration Synthesis = Condensation The way that polymers are
assembled Dehydration – water is
removed Synthesis – to make Remove water to make a bond
Fig. 5-2a
Dehydration removes a watermolecule, forming a new bond
Short polymer Unlinked monomer
Longer polymer
Dehydration reaction in the synthesis of a polymer
HO
HO
HO
H2O
H
HH
4321
1 2 3
(a)
Hydrolysis
The way that polymers are broken down (metabolized) Hydro – water Lysis – to cut/break Add water to break a bond
Where does a lot of hydrolysis happen?
Fig. 5-2b
Hydrolysis adds a watermolecule, breaking a bond
Hydrolysis of a polymer
HO
HO HO
H2O
H
H
H321
1 2 3 4
(b)
Carbohydrates
Sugars and their polymers Monosaccharides – one sugar
(building block) Disaccharides – two sugars Polysaccharides – many sugars
Multiple of the unit CH2O Glucose C6H12O6
Sugars
Can be chains or rings (3-7 carbons long) Have a carbonyl group (>C=O) Many hydroxyl groups (–OH)
Ald
oses
Glyceraldehyde
Ribose
Glucose Galactose
Hexoses (C6H12O6)Pentoses (C5H10O5)Trioses (C3H6O3)
Fig. 5-4a
(a) Linear and ring forms
Fig. 5-4b
(b) Abbreviated ring structure
Starch – a polymer of glucose Plants store sugars for later use
(inside plastids)
Functions of carbs in animals
Glucose: chemical fuel for respiration (mono)
Lactose: makes up some solutes in milk (di)
Glycogen: glucose storage in liver and muscles (poly)
Functions of carbs in plants
Fructose: found in fruits; make them sweet (mono)
Sucrose: transported through phloem (di)
Cellulose: components of cell walls (poly)
Fig. 5-8
b Glucosemonomer
Cellulosemolecules
Microfibril
Cellulosemicrofibrilsin a plantcell wall
0.5 µm
10 µm
Cell walls
Starch and Cellulose Digestion
Enzymes that digest starch by hydrolyzing linkages can’t hydrolyze linkages in cellulose
Cellulose in human food passes through the digestive tract as insoluble fiber
Chitin – a structural polysaccharide Found in the exoskeleton of arthropods Structural support for the cell walls of
many fungi
Lipids
Hydrophobic – they mix poorly with water
Mostly hydrocarbon regions – nonpolar
Fats - CHO
1 glycerol (alcohol with 3 carbons) + 3 fatty acids (long chain of CH connected to carboxyl)
Fatty acid(palmitic acid)
(a)Dehydration reaction in the synthesis of a fat
Glycerol
Fig. 5-11b
(b)Fat molecule (triacylglycerol)
Ester linkage Esterification
Saturated vs. Unsaturated
have the maximum number of hydrogen atoms possible and no double bonds
have one or more double bonds
Saturated fatty acids Unsaturated fatty acids
Animal vs. Plant
Most animal fats No double bonds
makes the tail flexible They can pack
together tightly Solid at room
temp
Most plant fats (oils) Double bonds
makes them bent Can’t pack together Liquid at room temp
Hydrogenated = added Hs to make them saturated
Saturated Fats Unsaturated Fat
What do fats do?
Too much saturated fat is bad for you Atherosclerosis –
plaques of fat in blood vessels
Hydrogenation forms trans fats – even worse!
Store lots of energy 2x as much as
carbs! Cushions vital
organs Insulates the
body
Bad things Good things
Phospholipids – make up cell membranes
(b)Space-filling model (c)Structural formula Phospholipid symbol
Fatty acids
Hydrophilichead
Hydrophobictails
Choline
Phosphate
Glycerol
Hyd
rop
hob
ic t
ails
Hyd
rop
hilic
head
One fatty acid is replaced by a phosphate
Phospholipid Bilayer – Cell Membrane
Polar Phosphate Heads
Non-Polar Fatty Acid Tails
Steroids
4 fused carbons rings
Hormones – cell to cell signaling (long distance)
Cholesterol – stabilizes cell membranes Made in liver Too much is bad
Other functions of lipids
Protection of vital organs
To insulate the body
They form the myelin sheath around some neurons
Proteins – CHON(S)
Needed for almost everything that happens in your cells/body
Function Example
Enzymes Amylase
Transport Hemoglobin
Movement Actin, myosin
Cell Recognition
Antigens
Channels Membrane Proteins
Structure Collagen, keratin
Hormones Insulin
Protection Antibodies
Polypeptides
Polymers of animo acids Not a protein
– doesn’t have full structure
R groups – ~20 in humans
The R group’s structure determines the property of the amino acid Example: Alanine = CH3
CH3 is nonpolar and so is Alanine
Alanine (Ala or A)
Fig. 5-17a
Nonpolar
Glycine (Gly or G)
Alanine (Ala or A)
Valine (Val or V)
Leucine (Leu or L)
Isoleucine (Ile or I)
Methionine (Met or M)
Phenylalanine (Phe or F)
Tryptophan (Trp or W)
Proline (Pro or P)
Fig. 5-17b
Polar
Asparagine (Asn or N)
Glutamine (Gln or Q)
Serine (Ser or S)
Threonine (Thr or T)
Cysteine (Cys or C)
Tyrosine (Tyr or Y)
Fig. 5-17c
Acidic
Arginine (Arg or R)
Histidine (His or H)
Aspartic acid (Asp or D)
Glutamic acid (Glu or E)
Lysine (Lys or K)
Basic
Electricallycharged
Peptide Bond (“polypeptide”) Made by
dehydration synthesis (condensation)
Nucleic Acids - CHONP
Polymer – nucleic acid Monomer -
nucleotide Hold the
information to make polypeptides (on genes)
Nucleic Acids
Each nucleotide has 3 parts: Nitrogenous
base Sugar Phosphate
group
Sugars
Always 5 carbons: Ribose – RNA
Deoxyribose – DNA
Nitrogenous Bases
Nitrogen containing rings
(c) Nucleoside components: nitrogenous bases
Purines
Guanine (G)Adenine (A)
Cytosine (C) Thymine (T, in DNA)Uracil (U, in RNA)
Nitrogenous basesPyrimidines
Double Helix
DNA strands are complementary A—T C—G
Double Helix
Spiral shape of DNA coil
Held together by H-bonds between bases And van der
Waals attractions
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