Download Carbohydrates

 Carbohydrates
Sugar classification & STRUCTURE
 Sugars! = “Saccharides”: (“-OSE”)
 Monosaccharides
Ex. Glucose, Fructose, Galactose
 Note: Glucose molecules (and others) form rings in aqueous
solutions; not linear form that we may draw.
 Two forms of glucose = ᾳ & β forms (Geometric isomers)
Dehydration synthesis of sugars form covalent bonds called
Glycosidic Linkages.
 Disaccharides
Ex. Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose = galactose
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 Polysaccharides (These are carbo’s Macromolecules)
Ex. Starch = polymer of all glucose monomers
Two types:
1. Amylose = unbranched
2. Amylopectin = branched
Glycogen = polymer of all glucose monomers; more extensively
branched than amylopectin.
Chitin = branched
Cellulose = unbranched
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 FUNCTION
 Function depends on structure = determined by its number and
type of monosaccharides and by position of glycosidic linkages.
 Mono- & Disaccharide
- 1st source of energy for most organisms
- Carbon skeleton provides raw material for synthesis of
other organics; ex., amino acids and lipids.
 Polysaccharides
 Energy storage
1. Starch = Plants
2. Glycogen = In liver and muscle of humans and other
vertebrates
 Structural
1. Chitin = exoskeleton for insects and some marine
animals. (shrimp, crab)
2. Cellulose = (all β glucose – every other glucose is
upside down; forms straight chain.
- Due to structure, chains can stack on top of one another =
Strong!
- Major component cell walls in plants and some bacteria.
 Cell Identification w/Protein ….more later
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Lipids
 Fats & Oils, Phospholipids, Steroids, Waxes
 Hydrophobic based on structure; Oxygen scarce and no
nitrogen = very little electronegativity = non-polar.
 1 gram of fat stores twice as much energy than 1 gram of
polysaccharide (Carb). WHY? Covalent bonds of long
Hydrocarbon chains,…lots of energy in those long chains!
 Harder to break all those H-C bonds (vs. bonds in carbs that
have oxygen at the bond).
1. Fats – not polymers, but are large
 STRUCTURE
 Composed of glycerol and fatty acids.
Ex. Triglyceride = 3 fatty acid + 1 glycerol
H-C covalent bonds in hydrocarbon chain = non-polar
- Ester linkage = bond between hydroxyl group of glycerol
and carboxyl group of fatty acid.
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 Fatty acids vary in length and in the number and locations of
double bonds.
- No double bonds = saturated fat (solid @ room temp)
o Packs tightly
- One or more double bonds (by removal of H) = unsaturated
fat (liquid @ room temp.)
Unsaturated cont…
o In H-C chain, where a cis double bond occurs = kink in the chain
= cannot pack close together = fluidity
o In H-C chain, where a trans-double bond occurs = allow tighter
packing, but can occur in both saturated and unsaturated fats.
Contributes to heart disease.
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 FUNCTION
 Energy storage in animals cells.
- Stored in adipose cells.
 Insulation
 Cushions vital organs
2. Phospholipids
 STRUCTURE
 Two fatty acids attached to glycerol (1 or 3 in fats) =
“tails” = hydrophobic
 Functional group = phosphate = “head” = negative charge =
hydrophilic
- Charged or polar molecules can attach to phosphate
(“head”) = variety of phospholipids
 Forms bilayer when in water.
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 FUNCTION
 Formation of cell membrane
1. Boundary for inside & outside cell…
2. Regulates cell’s internal environment = semi- or
selectively permeable.
3. Steroids
 STRUCTURE
 Carbon skeleton made up of 4 fused rings.
 Differ in functional groups.
- Example: Cholesterol & sex hormones
 FUNCTION
 Estrogen & Testosterone = Chemical messengers;
coordinates cell activities of an organism.
 Cholesterol = Helps maintain the fluidity of the membrane
Protein
 Remove the water from our cells and what’s left is mostly
protein!
 Determines the structure and function of an organism.
 STRUCTURE
 20 different amino acids
- Functional groups - carboxyl group at one end (C
terminus); amino group at the other end (N terminus).
(Hence, …amino acid)
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- General Structure:
 Amino acids differ in R group = can be non-polar, polar, or
charged
- R groups will give different properties to each amino acid;
will help determine overall structure of a specific protein.
- Covalent linkages = Peptide bonds = Carboxyl group of one
amino acid (loses -OH) covalently bonds with (-H) of a
different amino acid.
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 Protein Structure in Detail
 Polypeptide is to protein as is yarn is to a sweater.
 Amino acid sequence (number of and location of a.a)
determines protein conformation. = chemical properties of Rgroups.
 Folding is reinforced by various types of bonds = 3-D
conformation.
 Final conformation determines protein’s function.
 Almost always, the function of a protein depends on its
ability to recognize and bond to another molecule.
 4 levels of Protein Structure
1. Primary (1) = Unique sequence of a.a. (order & # of a.a.) = code
in DNA
- Shape = straight chain (polypeptide)
- Covalent bond = peptide bond between a.a.
2. Secondary (2)
- Shape
o coils = alpha () helix
o folds = beta () pleated sheet
- H-bonds = between the a.a. backbones (of different
polypeptides ~ 1).
o N and O = electronegative. H of amino group in one
polypeptide H-bonds with O of carboxyl group in a
second polypeptide.
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- Specifics of H-bonds
a. ᾳ - helix = coil
- H-bonding between
every 4th a.a.
- 3 non-polar a.a., then 1
charged a.a.,…and so on
b. β pleated sheet
- H-bonds on all a.a.
between polypeptide backbones
3. Tertiary (3) – superimposed secondary structures;.
- Shape = globular protein
- Bonds = H-bonds, Van der Waals forces, ionic bonds,
hydrophobic interactions, and disulfide bridges (covalent)
bonds stabilize protein conformation. Interactions
between R-Groups
o H-bonds between polar R groups.
o Hydrophobic interactions (due to presence of water) between
non-polar R groups = cluster together; once in cluster held
together by Van der Walls forces
o Ionic bonds between charged R groups.
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o Covalent bonds = disulfide bridges (S-S) = S of Sulfhydryl
groups of different a.a. are brought close together in the
folding of the protein for extra reinforcement of shape.
Small part of hypothetical protein
4. Quaternary (4) – Aggregation of different 2° & 3° levels
o One functional macromolecule
o Bonds = various
o Each subunit has a non-protein component
- Ex. Hemoglobin = carries O2/CO2 in blood; contains iron
-
Ex. Collagen = helical subunits (2°) intertwined –
connective tissue in skin, bone, tendon, ligaments
Accounts for 40% of protein in humans
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 FUNCTION
 Speed up chemical reactions = ENZYMES! [S/F = Lock-N-Key
Model]
- Active site of enzyme has specific shape
- Only fits specific substrate
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Support
Storage
Transport
Chemical messengers; coordinate organism’s activities on a
macro and micro level. (hormones = Ex. Insulin)
 Response to chemical stimuli.
 Movement
 Defense against disease
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Nucleic Acids
 Two types : DNA & RNA
 The linear sequences of nucleotide in DNA are passes from
parents to offspring
- The sequences of bases determine a.a. sequence for a
protein.
 1 gene codes for 1 protein
 Organisms that share a greater proportion of DNA sequences
are more closely related, evolutionarily; therefore, their
protein structures are also similar. (E/R!)
 STRUCTURE
 Consists of polymers called polynucleotides.
 Monomers = Nucleotides
- Nucleotide
1. Sugar (pentose);
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- Deoxyribose = DNA (lack Oxygen on 2nd C in ring;
hence = “Deoxy-“
- Ribose = RNA
2.
Nitrogen Base: Two groups; differ in functional
groups
- N removes H+ from solution; hence = “BASE”
- Note: Nucleoside = sugar & base
3.
Phosphate – attaches to the 5´ carbon of the sugar.
Note: Because the atoms in the sugars and the bases are both
numbered, the sugars have a prime (´) after the number
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Nulceotides are grouped based on size:
- Purine = larger – 6 member ring fused to a 5 member
ring of C & N.
 Adenine and Guanine
- Pyrimidine = smaller – 6 member ring of C & N.
 Cytosine and Thymine (& Uracil)
 Building a polynucleotide:
 Adjacent nucleotides are covalently bonded =
phosphodiester linkages; between the 3´ carbon of one
nucleotide and the phosphate on the 5´ carbon on the next.
= repeating pattern of sugars and phosphates down
backbone.
 One end of the polynucleotide = phosphate attached to 5´
C = 5´ end
 Other end = hydroxyl on 3´ C = 3´ end
 Both strands in DNA are anti-parallel (2 one way streets
running in the opposite directions)
 DNA is built from the 5´ to 3´ end!
 Sequence of bases attached to the sugars is unique to
each gene.
 H-bonds hold the two anti-parallel strands together at the
paired bases.
5´ ATCCGTA 3´
3´ TAGGCAT 5´
 Van der Waals forces hold together the stacked bases.
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Van der Waals
(between all base
Pairs; only shown
Once)
Covalent bond;
Phosphodiester linkage
(Double)H-bond
between A & T
(triple)H-bond
Between G & C
 FUNCTION
 Store genetic, hereditary information.
 Code to build proteins.
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