Lipids

Lipids are ==hydrophobic== (“water-fearing”), or insoluble in water, bc they are ==non-polar molecules==
Like carbohydrates, lipids contain carbon, hydrogen, and oxygen, but in lipids, the proportion of oxygen is much smaller
They are the body’s main form of stored energy, plasma membranes, and hormones
They also include fats, phospholipids, steroids, and waxes

Shock Absorbant

Fat absorbs shocks
Organs that are prone to bumps and shocks are ==cushioned== w a relatively ==thick layer== of fat

Metabolic Water

Lipids are a source of ==metabolic water==
During respiration, stored lipids are ==metabolized for energy==, producing water, and CO2

Insulation

Fat molecules are also called ==triacylgycerols or triglycerides==
They are made up of a ==glycerol backbone + three fatty acid tails==
In the human body, triglycerides are primarily stored in ==specialized fat cells called adipocytes== (adipose tissue)

An organic compound w three carbon atoms, five hydrogen atoms, and three hydroxyl (OH-) groups

Have a ==long chain of hydrocarbons== to which an ==acidic carboxyl group is attached==

Glycerides are formed when the hydroxyl group on glycerol ==bonds== w the carboxyl group (COOH) on fatty acids (dehydration synthesis)
Bond is called ==ester linkage==, and the process is known as ==esterification== (a C-O-C bond)

Saturated fatty acids contain as much hydrogen as it possibly could, bc there is a ==single bond betwen all its carbon atom==s (therefore ==two hydrogens== can form in each)
- ==Solid at room temp==

Fatty acids w ==one or more double bonds== are unsaturated since they contain ==less hydrogen== than before
Monounsaturated fatty acids contain ==one double bond==, meaning a hydrogen was ==taken away== from it
These double bonds result in kinks in the fatty acid chain affecting the ==melting point== of the fact

Contains ==more than one double bond==, further depriving it of hydrogens
- Tends to be ==liquid at room temp== as double bonds cause kinks in the structure and prevent molecules from packing together
A type of dietary fat, and one of the healthy ones (w monounsaturated)
Found in ==plant and animal foods==, like salmon, vegetable oils, and some nuts and seeds

In cis, chains of carbon atoms are on the ==same side of the double bond==, resulting in a kink
In trans, hydrogen atoms are on the ==opposite side of the double bonds== of the carbon chain, making the fat molecule straight
Cis isomers cannot line up next to one another as the trans isomers due to the ==larger bend==

Make up the ==lipid bilayer== of cell membranes, and ==important structural feature== of cells
Made up of a glycerol + two hydrophobic fatty acids + hydrophilic phosphate group

Phospholipids Bilayer

Phosphate heads facing the water and their tails pointing towards the inside
Bilayer prevents hydrophilic tails from coming into contact w water
If a drop of phospholipids is placed in water, it may spontaneously form a sphere-shaped structure known as a ==micelle==
- Hydrophilic phosphate heads ==face the outside== and the fatty acids tails ==face the interior== of this structure
This formation is a response to the ==amphipathic nature== of fatty acids

A steroid that is essential for animal cell membranes and converts into a number of compounds, like vitamin D
High cholestrol levels contribute to ==atherosclerosis==, which can lead to heart attacks and strokes

Fatty acids linked to ==alcohols or carbon rings==
Non-polar - hydrophobic
Pliable consistency - ==forms waterproof coating==
Barrier against ==water loss and infection==
Keeps birds dry and bees busy (forms honeycombs/beeswax)
Waxes cover the feathers of some aquatic birds and the leaf surfaces of some plants
- Hydrophobic properties prevent water from ==sticking to or soaking into the surface==