Human Biochemistry
Amino Acids and Proteins
• there are about 20 amino acids that occur
naturally
• they are the basic “building blocks” of
life/proteins
NH2CHRCOOH
• condensation reactions will link amino acids
together to form polypeptides that eventually
fold up into proteins
• enzymes are necessary!
• water is formed and they link together with a
peptide bond
• peptide bonds YouTube (1:14)
What is a protein video 3:38
Proteins have a complex structure which
can be explained by defining four levels of
structure
Primary Structure
• determined by the number, kind, and
order of a.a. in the polypeptide
• held together by simple peptide bonds
Secondary Structure
• the polypeptide then spontaneously folds into
regular, repeating structure because of hydrogen
bonding
Tertiary Structure
• highly specific looping and folding of the
polypeptide because of the following interactions
between their R-groups:
–
–
–
–
covalent bonding
hydrogen bonding
ionic bonding
London dispersion forces
• this tertiary level is the final level of organization
for proteins containing only a single polypeptide
chain
Quaternary Structure
• linkage of two or more polypeptides to
form a single protein in precise ratios and
with a precise 3-D configuration.
• Protein folding
Quaternary Structure example
Carbohydrates
• most abundant class of biological
molecules
• range from simple sugars (glucose) to
complex carbohydrates (starch)
Monosaccharides
•
simplest sugars (single sugars)
–
•
•
all contain the empirical formula (CH2O)
can be straight chains or cyclic form
two common isomers of monosaccharides
(C6H12O6)
•
•
glucose
fructose
Disaccharides
•
two monosacharides bonded together by a
condensation reaction that creates a
glycosidic linkage
•
water is formed
• three common disaccharides (don’t need to
know this)
1. sucrose - common table sugar
glucose + fructose
2. lactose - major sugar in milk
glucose + galactose
3. maltose - product of starch digestion
glucose + glucose
Polysaccharides
• starch- condensation of many glucose molecules
• condensation of many glucose molecules to
form long chains
• serve principally as food storage and
structural molecules in plants
• three types of polysaccharides
1. Starches (plants)
– serve as storage depots of glucose
2. Cellulose (plants)
– most abundant polysaccharide on Earth
– the major structural material of which plants are
made (wood and plant fibers)
– plant cell walls are among the strongest of biological
structures
3. Glycogen
– multi-branched that serves as a form of energy
storage in animals and fungi
Lipids
3 Main Types of Lipids
• ‘lipid’ comes from lipos, the Greek word for
fat
• all are hydrophobic (water-fearing/insoluble
in water)
• greasy, oily
1. Triglycerides (fats and oils)
• found in adipocyte cells that are in fatty tissue
• a condensation reaction called ester linkage
• types
- saturated fat
- do NOT contain C=C bonds
- therefore straight chained and have high melting
points
- lard and butter
- unsaturated fat
- have double bonds between one (monounsaturated
fats) or more (polyunsaturated fats) of the carbons in
the chain
- causes a kink in the carbon chain which prevents
them from packing close together and therefore
have low melting points (London dispersion forces
are weaker)
- vegetable oils
Saturated vs. Unsaturated fatty acids (2:51)
2. Phospholipids
• major structural components of cell
membranes
• polar “heads” love water (hydrophilic)
• uncharged “tails” avoid water (hydrophobic)
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+
+
_
3. Steroids
• cholesterol is the most abundant
and important steroid
• lipoproteins
– molecules made of proteins and fat
– transport cholesterol around the body
– low density lipoproteins (LDL) “bad
cholesterol”
• transport cholesterol to cells to be used
• however, can build up and cause cardiovascular
disease
– high density lipoproteins (HDL) “good
cholesterol”
• doesn’t have much cholesterol, therefore, can
absorb more cholesterol from the arteries and
transports it back to the liver