Transcript Ch. 5 Organic Chem

Chapter 5: The Molecules of Life
The Structure and Function of
Macromolecules
Macromolecules
• Giant molecules
• Built from monomers
– Condensation reaction
(dehydration reaction): One
monomer provides a hydroxyl
group while the other provides a
hydrogen to form a water
molecule
– Hydrolysis:
bonds between monomers are
broken by adding water
(digestion)
Four Major Classes of Organic Compounds found in Living Cells
•
•
•
•
Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbohydrates
• Serve as fuel and building materials
• Includes both sugars and the polymers of
sugars
• Types:
– Monosaccharide
– Disaccharide
– Polysaccharide
Monosaccharides
• Also know as simple sugars
• CH2O formula
• Composed of a carbonyl group (C=O)
with multiple hydroxyl group (-OH)
• Classified by:
– Location of carbonyl group
• aldehydes (aldoses, aldehyde sugar)
• ketones (ketone sugar)
– Size of the carbon skeleton
• 3 C-trioses
• 5 C-pentoses
• 6 C- hexoses
• Major nutrient for cells through
cellular respiration
• Monomer of disaccharides
Disaccharides
• Consist of two
monosaccharides joined by a
glycosidic linkage through a
condensation or dehydration
reaction
• Types:
– Sucrose =glucose + fructose
– Lactose = glucose + galactose
– Maltose = glucose + glucose
• Sometimes called “double
sugars” or “reducing sugars”
Polysaccharides
•Macromolecules
•Polymers of monosaccharides joined by glycosidic linkages
•Sugar monomers and position of glycosidic linkage
determine the function of
the polysaccharide
•Alpha and Beta glucose is determined
by the position of the hydroxyl group
on the #1 Carbon
Storage Polysaccharides
• Starch
– Made of glucose monomers
– Storage polysaccharide of plants
– Has 1-4 glycosidic linkages making it
unbranched and helical in shape
– Amylopectin is a branched for of starch
• Glycogen
– Made of glucose monomers
– Storage polysaccharide of animals
– Has 1-6 glycosidic linkages having
alternating glucose molecules
Structural Polysaccharide
• Cellulose
– Major component of plant cell walls
– Polymer of glucose with beta glycosidic
linkages therefore, the glucose alternate
position
– Parallel cellulose molecules are grouped as
microfibrils making them strong building
material
– Beta linkages cannot be hydrolyzed by
enzymes. That is why it is referred to by
humans as “insoluble fiber”
– Grazing animals have cellulose-digesting
bacteria in their rumen, the first
compartment of their stomach
Structural Polysaccharide
• Chitin
– structural polysaccharide used to build exoskeletons of
insects, spiders, and crustaceans
– Used to make dissolvable surgical thread
– Used by fungus to build cell walls instead of cellulose
• Similar in structure to cellulose
but has an added nitrogen
functional group
Lipids
• Does not consist of polymers
• Hydrophobic
• Types:
– Fats
– Phospholipids
– Steroids
• Function
– A gram of fat stores more than twice as much energy as a gram of a
polysaccharide
– Fat stored in adipose tissue cushions major organs
– Layer of fat below skin insulates the body
Fats
• Large molecules assembled together by dehydration
reactions
• Three fatty acids attach to glycerol by forming ester
linkages
– bond between a hydroxyl
group and a carboxyl group
Saturated vs. Unsaturated
• Fatty acids vary in length and in the number and locations of
double bonds
– Saturated fats
• No double bonds between carbon atoms composing the chains
• Solid at room temperature
– Unsaturated fats
• One or more double bonds formed by the removal of hydrogen
atoms from the carbon skeleton
• Liquid at room temperature due to kinks in the fatty acid tails
caused by cis double bond
– “Hydrogenated” means they have been synthetically converted
from an unsaturated fat to a saturated fat by the addition of
hydrogen atoms
– Polyunsaturated fats have more than one double bond
Phospholipids
• Contains only 2 fatty acids
attached to glycerol
• Phosphate group attached to
third hydroxyl group of glycerol
• Hydrocarbon ‘Tails’ are
hydrophobic
• Phosphate ‘head’ is hydrophilic
• Form cell membrane
– Hydrophobic tails point toward
interior
– Hydrophilic head on exterior
forming a boundary between
the cell and its environment
Steroids
• Lipids with a C skeleton consisting of 4 fused carbon rings
• Functional group attached cause variation in steroid
• Ex: Cholesterol:found in cell membranes ;precursor for other
steroids (sex hormones);
causes atherosclerosis
Proteins
• Importance:
– Instrumental in nearly everything organisms do
•
•
•
•
•
•
•
Speed up chemical reactions (Enzymes acting as catalysts)
Structural support
Storage
Transport
Cellular communications
Movement
Defense against foreign substances
– Make up 50% dry weight of cells
– The most structurally sophisticated molecules known
Polypeptide of Amino Acids
• Polymer of Amino Acids
– Organic molecule possessing both carboxyl and amino
groups
– Asymmetric carbon atom at center of the amino acid is
called the alpha carbon
– R group or side chain differs with each of the 20 different
amino acids
Protein Structure
•Primary
•Secondary
•Tertiary
•Quaternary
Primary Structure
• Unique sequence of Amino Acids
• Can spontaneously arrange itself into a
three-dimensional shape determined and
maintained by the interactions responsible
for secondary and tertiary structure
• Conformation dependent on:
– Linear structure
– Physical and chemical environment of protein
• Each type of protein has a
unique primary structure of amino
acid
Secondary Structure
• Coils & folds as a result of hydrogen
bonds between repeating
constituents of the primary structure
• Alpha Helix
– coiling caused by bonding between
every fourth amino acid
– keratin in hair;
• Beta Pleated Sheet
– Bonds between two parallel sections
– Make up the core of many globular
proteins
– Spider silk
Tertiary Structure
• Overall shape due to
interactions of the primary
structure and the side chain
amino acids R groups
–
–
–
–
Hydrophobic
Disulfide bridges
Hydrogen bonds
Ionic bonds
• All types of interactions can
occur in one protein
Quaternary Structure
• Two or more polypeptide
chains aggregated into one
macromolecule
– collagen (connective tissue)
– hemoglobin
Denaturation/Renaturation
• Protein unravels and loses its native conformation
• Causes protein to loose its ability to function
• Caused by:
– pH
– Salt concentration
– Temperature
• Some proteins can renature when environmental
conditions restore to normal
Chaperonins
• Protein molecules that act as
a shelter for other proteins
that are in the process of
folding
• Keep folding protein
separated from “bad
influences” in the
cytoplasmic environment
Nucleic Acids
• Types
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
• Both are important for protein synthesis
– DNA->RNA->protein
• Polymers of nucleotides called
polynucleotide
• Each nucleotide is comprised of:
– nitrogenous base
– pentose sugar
– phosphate group
• The portion of the nucleotide without the
phosphate group is called the nucleoside
Nucleotide Monomers
• Pyrimidines
– Six-carbon ring and nitrogen atoms
• Cystosine
• Thymine-only found in DNA
• Uracil-only found in RNA
• Purines
– Six-carbon ring attached to a fivecarbon ring
• Adenine
• Guanine
• Pentose in RNA is Ribose while
Pentose in DNA is Deoxyribose
Nucleotide Polymers
• Adjacent nucleotides are
linked together by covalent
bonds called phosphodiester
linkages between the –OH
group on the 3’ carbon on one
nucleotide and the phosphate
on the 5’ carbon on the next
nucleotide
DNA Double Helix
• Inheritance based on DNA
replication
• Double helix (Watson &
Crick - 1953)
– H bonds~ between paired bases
– Van der Waals~ between stacked
bases
• Complementary base pairing
– A to T
– C to G
Genetic Transmission
• The unique sequence of the bases on a DNA polymer is in
the 5’ to 3’ end
• sequence determines amino acid sequence of genes passed
to next generation and evolutionary links
• DNA Strands are antiparallel
• Each strand used as a
template in DNA replication
process