Beta-sheet
Alpha-helix
Example of polypeptide, IgG
Biological molecules (IV),Lipids
Lipids are a class of nonpolar molecules that include the fats,
cholesterol,fatty acids,lipid-soluble vitamins,waxes,soaps,
glycerophospholipids,sphingolipids,and others,Lipids are
found in the membranes of cells,the endoplasmic reticulum,
and in specialized fat storage cells called adipocytes.
Example of Lipids:
Fat (Triacylglycerols), Fats are composed of glycerol esterified
to three fatty acids,Fats are derived from three primary
sources,(1) the diet; (2) de novo biosynthesis,particularly in
liver; and (3) storage depots in adipocytes.
Bilayer lipid membrane
Processes by which
fats are utilized in
animals are
summarized here,
Breakdown of fats
by lipases yields
fatty acids and
glycerol.
Fatty acid species
Cholesterol
Cholesterol is a member of a large group of substances
called steroids,which include vitamin D and a number of
steroid hormones,among them the sex hormones of higher
animals,In fact,cholesterol is the precursor for the
synthesis of many of these substances and is also a
precursor of the bile acids.
Lipid-Soluble Vitamins
Vitamins A,D,E,and K are lipid-soluble,Although one of
these,Vitamin D,is ultimately derived from cholesterol,
the other three are not.
Chemical structure
of Vitamin D
Glycerophospholipids (also called phospho-
glycerides) are lipids with a glycerol backbone
and a phosphate group,usually on carbon 3 of
the glycerol,Glycerophospholipids are
important compounds in the membranes of cells.
Sphingolipids are a class of lipids found in
membranes,particularly of nervous tissue,
Sphingolipids are derived ultimately from
palmitoyl-CoA and serine.
Other kinds of Lipids
Chemical properties of biomolecules
? Chirality
? Bondings
? Forces
Chirality
D- and L-chirality
Different functional groups
Covalent bond (e.g,peptide bond)
Hydrogen bonding
Dipole-dipole interaction
Van der Waals
force is weak,
and does not
have a fixed
geometry
Van der Waals force
Different forms of force in
polypeptide
Water
Water,H2O
? Water is the most abundant substance in living systems,
making up 70% or more of the weight of most organisms,
? The first living organisms arose in an aqueous environment.
? Water has a higher melting point,boiling point and heat of
vaporization than most other common solvents.
? Water participates in many biological reactions
(e.g,hydrolysis).
? The dipolar nature of water provides hydrogen bonding.
Biological functions of water
? Because of its unique chemical and physical
characteristics,water plays several key roles in
metabolic processes,It serves as a solvent for many
chemical compounds,a medium in which many
chemical reactions occur,even as a reactant or product
in many reactions.
? As water is diffusible through the semipermeable
membrane,it is critical for adjusting osmotic
differences,Therefore,water can help prevent cells
(organisms) from burst (osmotic lysis),Temperature
adjustment,waste removal,lubrication for joints,etc..
Elements necessary for
terrestrial organisms:
Classified according to
their abundance
Alpha-helix
Example of polypeptide, IgG
Biological molecules (IV),Lipids
Lipids are a class of nonpolar molecules that include the fats,
cholesterol,fatty acids,lipid-soluble vitamins,waxes,soaps,
glycerophospholipids,sphingolipids,and others,Lipids are
found in the membranes of cells,the endoplasmic reticulum,
and in specialized fat storage cells called adipocytes.
Example of Lipids:
Fat (Triacylglycerols), Fats are composed of glycerol esterified
to three fatty acids,Fats are derived from three primary
sources,(1) the diet; (2) de novo biosynthesis,particularly in
liver; and (3) storage depots in adipocytes.
Bilayer lipid membrane
Processes by which
fats are utilized in
animals are
summarized here,
Breakdown of fats
by lipases yields
fatty acids and
glycerol.
Fatty acid species
Cholesterol
Cholesterol is a member of a large group of substances
called steroids,which include vitamin D and a number of
steroid hormones,among them the sex hormones of higher
animals,In fact,cholesterol is the precursor for the
synthesis of many of these substances and is also a
precursor of the bile acids.
Lipid-Soluble Vitamins
Vitamins A,D,E,and K are lipid-soluble,Although one of
these,Vitamin D,is ultimately derived from cholesterol,
the other three are not.
Chemical structure
of Vitamin D
Glycerophospholipids (also called phospho-
glycerides) are lipids with a glycerol backbone
and a phosphate group,usually on carbon 3 of
the glycerol,Glycerophospholipids are
important compounds in the membranes of cells.
Sphingolipids are a class of lipids found in
membranes,particularly of nervous tissue,
Sphingolipids are derived ultimately from
palmitoyl-CoA and serine.
Other kinds of Lipids
Chemical properties of biomolecules
? Chirality
? Bondings
? Forces
Chirality
D- and L-chirality
Different functional groups
Covalent bond (e.g,peptide bond)
Hydrogen bonding
Dipole-dipole interaction
Van der Waals
force is weak,
and does not
have a fixed
geometry
Van der Waals force
Different forms of force in
polypeptide
Water
Water,H2O
? Water is the most abundant substance in living systems,
making up 70% or more of the weight of most organisms,
? The first living organisms arose in an aqueous environment.
? Water has a higher melting point,boiling point and heat of
vaporization than most other common solvents.
? Water participates in many biological reactions
(e.g,hydrolysis).
? The dipolar nature of water provides hydrogen bonding.
Biological functions of water
? Because of its unique chemical and physical
characteristics,water plays several key roles in
metabolic processes,It serves as a solvent for many
chemical compounds,a medium in which many
chemical reactions occur,even as a reactant or product
in many reactions.
? As water is diffusible through the semipermeable
membrane,it is critical for adjusting osmotic
differences,Therefore,water can help prevent cells
(organisms) from burst (osmotic lysis),Temperature
adjustment,waste removal,lubrication for joints,etc..
Elements necessary for
terrestrial organisms:
Classified according to
their abundance
