[[Macromolecules]]

# General Overview
fats and water insoluable, mostly composed of carbon and hydrogen with tidbits of oxygen

# Structure
mostly made up of carbon and hydrogen (create hydrocarbon chains), which are non polars, causing them to be hydrophobic.

| Oxygens Present           | Polar    | Hydrophilic |
| ------------------------- | -------- | ----------- |
| No/Little Oxygens Present | Nonpolar | Hydrophobic |
tons of types of lipids, so no single monomer/polymer name. important monomers in ap biology are glycerol and fatty acids, and important polymers are triglycerides and phospholipids.
fatty acid monomer, long hydrocarbon chain which defines it a lipid:
![[Pasted image 20260813173740.png]]

unlike other macromolecules, lipid polymers arent repeated monomers. they use ester bonds/linkages to bind monomers to hold them together.

![[Pasted image 20260813174224.png]]
![[Pasted image 20260813174228.png]]
"Unlike starch, the phospholipid bilayer (aka the cell membrane) is not made up of linked monomers. Instead, it is made of multiple monomers that are packed tightly against each other."

"_**Key Takeaway:** Lipids are nonpolar, hydrophobic macromolecules. Lipid polymers are special in that they are not a repeating series of monomers, unlike the polymers from the other macromolecule groups._"
# Function
ap bio important lipids:
* Steroids - hormones
* Fats - insulation and energy storage
* Phospholipids - forms cell membranes
* Cholesterol - structural stability to animal cell membranes
hormones are molecules that travel through the body and incite certain chemical reactions in certain cells. 
![[Pasted image 20260813174454.png]]
lipid because lots of carbons and hydrogens

second function of lipids is to form cell membranes, primarily done by phospholipid which have a hydrophobic tail and a hydrophilic head. polar/nonpolar natures makes them great for cell membranes.
![[Pasted image 20260813174636.png]]
"As you can see, the head of the phospholipid contains lots of different atoms that contribute to it being hydrophilic. However, the tail only consists of a hydrocarbon chain. This is what gives phospholipids their dual nature. In a cell membrane, the heads of the phospholipids face the outside and inside of the cell, which are water-filled environments, whereas the tails face each other, creating a bilayer. (Q3) Below is a visual representation:"
![[Pasted image 20260813174945.png]]

cholesterol provides stability to cell membranes
unique property is that phospholipids can be saturated or unsaturated, term refers to kinks and bends in hydrophobic tails. 
![[Pasted image 20260813175101.png]]
when unsaturated fatty acids are present, they are liquid, when saturated fats are there, theyre solid because saturated fatty acids pack together well

we dont freeze in cold environments because our cell membranes contain unsaturated fats in bilayers, preventing them from freezing, while saturated fats contain only single bonds between carbon atoms.

unsaturated fatty acids contain atleast one double bond between carbon, which causes carbon chain to kink, somehow preventing lipids from freezing together. more kinks = more resistant to freezing = more liquid at room temp

fats are lipids, and help with energy storage and insulation, and we need em despite the people saying fats are ugly and suck

"_**Key Takeaway:** Hormones are lipids that are used in long-distance cell-to-cell communication. Phospholipids form bilayers to make up cell membranes; their hydrophilic heads face the outside and inside of the cell, and their tails face inwards. Phospholipids can be saturated or unsaturated. Unsaturated phospholipids are less prone to freezing, which is why they are present in cell membranes._"
# Summary

Structure: Varies. Phospholipids have hydrophilic heads and hydrophobic tails.

Monomer / Polymer Name: N/A

Function: Long-term energy storage, hormones used in long-distance cellular signaling, phospholipids make up the bilayer in the cell membrane