Lipids: Not Just Fat

BIOL 103, Chapter 6-1

Today’s Topics

• What are Lipids?• Fatty Acids are Key Building Blocks• Triglycerides• Phospholipids• Sterols

Lipids

• Essential nutrients• Provide energy• Help transport fat-soluble nutrients• Contribute to flavor and texture of food

What are Lipids?

• Lipids include…– Triglycerides (__________________________)

• In body: stored in adipose tissue• In food: “fats and oils”

– Phospholipids (_________________________)• Plant and animal origin• Body can make them• Soluble in fat and water

– Sterols (_______________________________)• Most well known: Cholesterol

Fatty Acids are Key Building Blocks

• Fatty Acids – Determine whether a fat is ________________ at

room temperature– Basic structure:

• Chain length– ____________ Carbon length

Fatty Acids are Key Building Blocks

• Saturation– Saturated fatty acids

• _________________________ between carbons

– Unsaturated fatty acids• _______________________________1. Monounsaturated fatty acid (MUFA):

– _______________________

2. Polyunsaturated fatty acid (PUFA):– ________________________

– Fats with more bonds are generally more _____________

Fatty Acids are Key Building Blocks

Cis fatty acids• Occurs ________________• Chain is _______________

Trans fatty acids• Produced by ____________

(adds hydrogen to an unsaturated fatty acids)

• A small portion of trans fat can occur naturally

• Chain is ________________

Trans Fat

• In health, trans fatty acids are known to raise LDL (“bad”) cholesterol, and lower HDL (“good cholesterol”), promote systemic inflammation, and increase triglycerides in your blood.

• History and how it is made:– In Europe (1910): needed a cheaper butter substitute

for soldiers– In US (1960s): People wanted to eat a “healthier and

cheaper butter” food scientists decided to hydrogenate vegetable oil to solidify them

Fatty Acids are Key Building Blocks

• Nonessential and essential fatty acids1. Nonessential fatty acids

• Can be made in the body• Not “essential” to have in your diet

Fatty Acids are Key Building Blocks

• Nonessential and essential fatty acids (cont.)2. Essential fatty acids

• Can’t be made in the body

• Must come from food• _________________________________________________________________• Used to make

eicosanoids

Triglycerides• Structure

– ________________________• Functions

1.Energy source: 9 kcal/g2.Energy reserve: form of stored energy in _________

___________________________________________3. Insulation and protection:

1. Visceral fat ____________________________2. Subcutaneous fat _________________________________

4.Carrier of ____________________________5.Sensory qualities in food

Apple vs. Pear

Triglycerides in Food

• Found in a variety of fats and oils• Classified by their most prevalent type

– Saturated fatty acids: _________________ and tropical oils

– Polyunsaturated fatty acids: _________________• Omega-3: soybean, flaxseed oils; salmon, tuna• Omega-6: seeds, nuts, corn oil, meat, poultry, eggs

What are the positive and negative consequences of hydrogenating a fat?

(Problem Set 6, #3)

Pros

1. _____________________ _____________________

2. _____________________ _____________________

Cons

1. ______________________2. ______________________

______________________

• Oxidation causes food to spoil and damage body tissues

Phospholipids

• Structure– _______________________________

• Functions:1.____________________

• Keep fat suspended in water• Keep oil and water mixed

2._____________________ for cell membranes

Phospholipids

• Cell membrane– Double layer of

phospholipids– Store fatty acids

temporarily and release them as needed

– Important role in nerve cells

• e.g. Ach

Phospholipids

• Lipid transport– Stomach

• Breaks fat into tiny particles for digestion

– Intestine• Continues emulsifying fat

– Blood• _____________________________________ that

carry lipid particles to their destinations in the body

Phospholipids

• Emulsifiers (Lecithin)– In body

• Phospholipid with choline ___________________

– In food• Blend of phospholipids

with different nitrogen-containing components

• Used as emulsifiers (e.g. salad dressing, chili, sloppy-joe mixes, and chewing gum).

Phospholipids

• Phospholipids in food– Occur naturally in plants and animals– Examples: Egg yolks, liver, soybeans, peanuts– _________________________ because the body

can make it

Sterols

• A category of lipids that include cholesterol

• Structural characteristics:– ____________________– ____________________

Sterols

• Cholesterol functions:1. ________________________of cell membranes2. Precursor to other substances

• Examples: __________________________________, Manufacture bile salts

• Cholesterol synthesis in _________________• Sterols in food

– Found only in _____________________