AP Biology

Lipids: Fats & Oils & Wax & Steroid

AP Biology

Lipids Lipids are composed of C, H, O 4 groups:

fats oils waxes steroids

Do not form polymers big molecules made of smaller subunits not a continuing chain

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Lipids Six functions of lipids:1. Long term energy storage2. Protection against heat loss (insulation)3. Protection against physical shock4. Protection against water loss5. Chemical messengers (hormones)6. Major component of membranes (phospholipids)

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Fats store energy Function:

energy storage 2x energy of

carbohydrates cushion organs insulates body

think whale blubber!

Why do humanslike fatty foods?

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Fat subunits Structure:

glycerol (3C alcohol) + fatty acid

dehydration synthesis

fatty acid = long “tail” with COOH group at “head”

Fatty Acid Structure

• Carboxyl group (COOH) forms the acid.• “R” group is a hydrocarbon chain (chain of hydrogens and carbons).

A Representative Fatty Acid

Hydrocarbon Group

CarboxylGroup

Synthesis of a Fat

A Phospholipid

Hydrophilic vs hydrophobicHydrophilic – Water loving – soluble in waterHydrophobic – water hating – is NOT soluble in water

Triglyceride =1 glycerol, 3 fatty acids Hydrophilic

Phospholipids = 1 glycerol, 2 fatty acids 1 phosphate group tails are hydrophobic the heads are hydrophilic. make up cell membranes

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Saturated fats All C bonded to H No C=C double bonds

long, straight chain most animal fats solid at room temp.

contributes to cardiovascular disease (atherosclerosis) = plaque deposits

SaturatedFatty Acid

UnsaturatedFatty Acid

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Unsaturated fats C=C double bonds in

the fatty acids plant & fish fats vegetable oils liquid at room temperature

the kinks made by doublebonded C prevent the molecules from packing tightly together

mono-unsaturated?poly-unsaturated?

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Saturated vs. unsaturatedsaturated unsaturated

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If fatty acids are unsaturated, their shape is altered from a saturated molecule so the molecules in the Lipid push apart, thus making it more fluid and oily.

Animals tend to have more saturated, and consequently solid at room temperature lipids

whereas plants tend to have more unsaturated and so fluid at room temperature lipids

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Waxes

• Ear wax – protection from foreign materials/ invaders (such as insects)

• Wax coating on leaves – forms a barrier to keep water in leaves

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Steroids

Cholesterol Found in cell membranes – keeps them

flexible Hormones (chemical messengers)

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Quiz1. What are the four types of lipids ?

2. Name as many functions of lipids as possible (6).

3. What is the difference in saturated & unsaturated ?

4. How could you tell the difference in saturated & unsaturated by looking at an item ?

5. What is healthier, saturated or unsaturated fats ?

6. Lipids contain more energy than carbs, so why are carbs are primary energy source ?

7. What is the monomer & polymer of lipids ?

8. Structurally, how do you tell the difference in carbs & lipids ?

AP Biology

Answers1. Fats, oils, waxes, & steroids

2. Energy storage, insulation, protection from water loss, protection against physical shocks, chemical messengers, component of cell membranes

3. C=C double bonds are in unsaturated

4. Saturated are solid at room temp., unsaturated are liquid at room temp.

5. unsaturated

6. Lipids are harder to break down, because they are insoluble in water

7. Technically, there are not monomers & polymers

8. Both contain C,H, & O, but in carbs they are in a 1:2:1 ratio