fats
lipids
a family of organic compounds that are not soluble in water
what do lipids include
triglycerides
make up ~95% of all lipids in foods and the human body
triglycerides (fats)
lipids that are solid at room temp
triglycerides (oils)
lipids that are liquid at room temp
functions of fat
fat cells (adipose cells)
specialized for fat storage
- they expand and multiply (we store more)
adipose (fat) tissue
is an metabolically active tissue
- secretes hormones and produces enzymes that influence food intake and affect the body’s use of nutrients
why can more fat be stored than glycogen?
fats pack tightly together without water allowing far more fat to be stored compared to glycogen
- far more efficient storage form
other functions of fat
shock absorber
pads of fat surround vital internal organs
thermoregulation
fat pads under the skin insulate the body from temperature extremes
cell membranes
lipids are a component of cell membrane
needed nutrients
fat-soluble vitamins (A, D, E, and K) are found mainly in foods that contain fat
essential fatty acids
serve as raw materials for other compounds (eicosanoids)
fats and pleasure
value of fats
the energy density of fats makes foods rich in fat valuable in some situations
- a hunter or hiker = long distances or very cold weather
- potentially unneeded calories if sedentary
satiety
feeling of fullness or satisfaction that people experience AFTER meals
satiation
feeling of fullness WHILE eating
fat and satiety
fat contributes to satiety
- fat in foods triggers a series of physiological events that slow the emptying of stomach and promote satiety
- fat in the SI signals release of CCK
3 classes of lipids
triglyceride
3 fatty acids + glycerol
fatty acids
organic acids composed of carbon chains of various lengths
- each has an acid end and hydrogens attached to all the carbon atoms of the chain
- differ on the basis of length and degree of saturation (even with the same triglyceride)