Download Lipids - OoCities

Lipids
•long-term energy storage
•do not consist of polymers
•insoluble in polar substances
•structural components of cells –
ex. phospholipids are the major building block in cell membranes
•"messengers" (hormones)
Lipid Construction
•Lipids are composed of three fatty acids covalently bonded to a 3carbon glycerol
•The fatty acids are composed of CH2 units, and are hydrophobic/not
water soluble
Fats
–Are constructed from two types of smaller molecules, a single
glycerol and usually three fatty acids
Saturated fatty acids
–Have the maximum number of hydrogen atoms possible
–Have no double bonds
Saturated Fats
Unsaturated fatty acids
–Have one or more double bonds
Unsaturated Fat
•Saturated refers to the "saturation" of the molecule by hydrogen
atoms
•The presence of a double C=C covalent bond reduces the number of
hydrogens that can bond to the carbon chain, hence the application
of the term "unsaturated“.
•Fatty acids can be saturated (meaning they have as many
hydrogens bonded to their carbons as possible) or unsaturated (with
one or more double bonds connecting their carbons, hence fewer
hydrogens).
•Fat - solid at room temperature (saturated)
•Oil - liquid (unsaturated)
Phospholipids
 Have only two fatty acids
 Have a phosphate group instead of a third fatty acid
Phospholipid structure
–Consists of a hydrophilic “head” and hydrophobic “tails”
–Results in a bilayer arrangement found in cell membranes
Cholesterol and steroids
•Steroids - lipids characterized by a carbon skeleton consisting of
four fused rings
•One steroid, cholesterol
–Is found in cell membranes
–Is a precursor for some hormones
Cholesterol
•Excess cholesterol in the blood has been linked to atherosclerosis,
hardening of the arteries.
Functions of Fats and Oils
•Long term energy storage
•Animals convert excess sugars (beyond their glycogen storage
capacities) into fats
•Plants store excess sugars as starch, although some seeds and
fruits have energy stored as oils - corn oil, peanut oil, palm oil, canola
oil, and sunflower oil
•Fats store six times as much energy as glycogen.
•Insulation - heat retention
•Cushion – protection (body organs, fetus)
•Structural components of cells - Phospholipids and glycolipids –
cell membranes
•Phospholipids are modified so that a phosphate group (PO4-) is
added to one of the fatty acids.
• The addition of this group makes a polar "head" and two nonpolar
"tails".
•Waxes – cuticle -waxy layer covering the leaves and stems of many
land plants; and protective coverings on skin and fur of animals
•Hormones – body regulation