AP Bio Chapter 3 : Lipids (20-30)

Are Lipids small or large molecules? Why?

Large due to long hydracarbon tails

Are lipids polymers?

No

• They’re not built from identical or similar small units (monomers)

• Not linked together in chains

Unifying characteristic of all lipids

• Little to no affinity for water

• Hydrophobic

Why are lipids hydrophobic?

Hydrocarbon tails, which form no polar covalent bonds

What are the most biologically important lipids?

Fats, phospholipids, steroids

What molecules are fats composed of?

Glycerol and fatty acids

What is Glycerol made of?

A 3-carbon alcohol with a hydroxyl group attached to each carbon, rest filled with hydrogens (saturated) or other atoms (unsaturated)

What is a fatty acid made of?

carboxyl group + long hydrocarbon tail.

What is the structure of a fatty acid, and how do you tell if it’s saturated or unsaturated?

A fatty acid has a carboxyl group (–COOH) attached to a long hydrocarbon tail made of carbon and hydrogen atoms.

• If all the carbon-carbon bonds are single, it is saturated (fully filled with hydrogen).

• If there are one or more double bonds, it is unsaturated.

What happens when 3 fatty acids react with 1 glycerol?

They undergo dehydration synthesis to form 1 fat molecule (triglyceride) and 3 water molecules.

when 3 fatty acids react with 1 glycerol,

the –OH from the glycerol and the –H from the fatty acid's –COOH combine to form water (H₂O).

• happens for each fatty acid

.

What is an ester bond, and how is it formed in fats?

An ester bond is a chemical link formed between a hydroxyl group (–OH) (from glycerol) and a carboxyl group (–COOH) (from fatty acid).

ester bonds always form via a ____________ reaction, because water is removed when a carboxyl group reacts with a hydroxyl group.

ester bonds always form via a dehydration reaction, because water is removed when a carboxyl group reacts with a hydroxyl group.

Fats are also called _____________

triglycerides

Unsaturated Fat molecule characteristics

• plant / fish oil (olive, corn, cod)

• liquid at room temp

• double binds cause bending

• missing “H”s

In a saturated fat:

• All carbon (C) atoms in the hydrocarbon chain are connected by __________ bonds.

• Each carbon is "saturated" with the _____________ number of hydrogen (H) atoms.

In a saturated fat:

• All carbon (C) atoms in the hydrocarbon chain are connected by single bonds.

• Each carbon is "saturated" with the maximum number of hydrogen (H) atoms.

• If the double bond is in the cis configuration (which is common in natural fats), it forces a kink or bend in the chain.

• This bend happens because the two hydrogen atoms on the carbons involved in the double bond are on the same side, which pushes the chain sideways.

In an unsaturated fat:

• One or more _______ bonds (C=C) appear between ________ atoms.

• Because of the _________ bond, those carbons can't bond to as many H atoms — so there are _______ hydrogens.

• That’s what we mean by "missing H’s."

In an unsaturated fat:

• One or more double bonds (C=C) appear between carbon atoms.

• Because of the double bond, those carbons can't bond to as many H atoms — so there are fewer hydrogens.

• That’s what we mean by "missing H’s."

Unsaturated Fat molecule characteristics…

• ______/______ Fats (Olive, corn, cod)

• ________ at room  temperature

• __________ bonds cause __________

• “________” H’s

• Plant/Fish Fats (Olive, corn, cod)

• Liquid at room  temperature

• Double bonds cause bending

• “Missing” H’s

Saturated Fat molecule characteristics…

• ___________ fats (butter, lard)

• _________ at room temperature

• Yes/ No double bonds

• _________ line chain

• “________” with H’s

• Animal fats (butter, lard)

• Solid at room temperature

• No double bonds

• Straight line chain

• “Full” with H’s

Trans fats contribute _____ than saturated fats to cardiovascular disease

more

What are phospholipids made of?

2 fatty acids, a phosphate group, glycerol, and R group

What are the 3 major function of fats?

1) Energy storage

2) Insulation

3) Cushion (vital) organs

Are fatty acid tails polar or nonpolar

Nonpolar

A phospholipid is a molecule that makes up the _______________________

cell membrane

• Hydrophobic tails ___________ water and face __________

• Hydrophilic heads face __________ ________ water.

• Hydrophobic tails hide from water and face inward (toward each other).

• Hydrophilic heads face outward toward the water.

Phospholipid head

• This part contains a _________ group, often attached to other small polar molecules.

• It is _________ and can form __________________ with water.

Phosphate Group Head 💧

• This part contains a phosphate group, often attached to other small polar molecules.

• It is polar and can form hydrogen bonds with water.

The structure of phospholipids results in a _______ arrangement found in __________________ (major component).

Bilayer, cell membranes

What are steroids made of?

Steroids are lipids made of four fused carbon rings (three 6-carbon rings and one 5-carbon ring).

Steroids have _______ 6-carbon ring(s) and _________ 5-carbon ring(s).

three 6-carbon rings and one 5-carbon ring).

Are steroids considered lipids?

Yes, because they are hydrophobic and insoluble in water.

Name three examples of steroids.

Cholesterol, testosterone, estrogen.