Carbohydrates and Lipids

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Chapter 5: Macromolecules

Macromolecules

• Smaller organic molecules join together to form larger molecules

o macromolecules

• 4 major classes of macromolecules:

o Carbohydrates

o Lipids

o Proteins

o Nucleic acids

Polymers

• Long molecules built by linking chain of

repeating smaller units

o monomers = repeated small units

o Covalent bonds

How to Build a Polymer

• Condensation Reaction

o Dehydration synthesis

o Joins monomers by “taking” H2O out

� 1 monomer provides OH

� the other monomer provides H

� together these form H2O

o Requires energy & enzymes

How to Break Down a Polymer

• Hydrolysis

o Use H2O to break apart monomers

� Reverse of condensation

reaction

� H2O is split into H and OH

� H & OH group attach where

the covalent bond used to be.

o ex: Digestion is hydrolysis.

Carbohydrates

• Carbohydrates are composed of C, H, O

carbo - hydr - ate

CH2O

(CH2O)x ���� C6H12O6

• Function:

o energy energy storage

o raw materials structural materials

• Monomer: sugars

o ex: sugars & starches

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Sugars

• Most names for sugars end in -ose

• Classified by number of carbons

o 6C = hexose (glucose)

o 5C = pentose (fructose, ribose)

o 3C = triose (glyceraldehyde)

• What functional groups are used?

o Carbonyl- Ketones and Aldehydes

o Hydroxyl

Sugar Structure

• 5C & 6C sugars form rings in aqueous solutions

• Carbons are numbered.

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Simple & Complex Sugars

• Monosaccharides

o Simple 1 monomer sugars

o Glucose

• Disaccharides

o 2 monomers

o Sucrose

• Polysaccharides

o Large polymers

o Starch

Building Sugars

• Dehydration Synthesis

Polysaccharides

• Polymers of Sugars

o Costs little energy to build

o Easily reversible = release energy

• Function:

o Energy Storage

� starch (plants)

� glycogen (animals)

o Building Materials = structure

� cellulose (plants)

� chitin (arthropods & fungi)

Polysaccharide Diversity

• Molecular structure determines function

o Isomers of glucose

o How does structure influence function…

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Digesting Starch vs. Cellulose

Cellulose

• Most abundant organic compound on Earth.

Glycemic Index

• Ranking of carbohydrates based on their immediate effect on blood glucose (blood sugar) levels

• Carbohydrate foods that breakdown quickly during digestion have the highest glycemic indices.

Their blood sugar response is fast & high.

• Which food will get into your blood more quickly?

o apple 36

o rice cakes 82

o corn flakes 84

o bagel 72

o peanut M&M 33

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Chapter 5 Macromolecules: Lipids

Lipids

• Lipids are composed of C, H, O

o Long hydrocarbon chain

• Diverse Group

� Fats

� Phospholipids

� Steroids

• Do not form polymers

o Big molecules made of subunit smaller

molecules.

o Not a continuing chain.

Fats

• Structure:

o Glycerol (3C alcohol) + fatty acid

� Fatty acid = long HC “tail” with COOH

group at “head”.

• Triacylglycerol

o 3 fatty acids linked to glycerol.

o Ester linkage = between OH & COOH.

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• Long HC Chain

o Polar or non-polar?

o Hydrophilic or hydrophobic?

• Function:

o Energy storage

� very rich

� 2x carbohydrates

o Cushion organs

o Insulates body

� Think whale

blubber!

Saturated Fats

• All C bonded to H

• No C=C double bonds

o long, straight chain

o most animal fats

o solid at room temp.

� contributes to cardiovascular disease

(atherosclerosis) = plaque deposits

Unsaturated Fats

• C=C double bonds in the fatty acids

o Plant & fish fats

o Vvegetable oils

o Liquid at room temperature

� The kinks made by double bonded C prevent the

molecules from packing tightly together.

Phospholipids

• Structure:

• Glycerol + 2 fatty acids + PO4

o PO4 negatively charged

o other small molecules may

also be attached

� Adenine (ATP)

• Hydrophobic or hydrophilic?

o Fatty acid tails =

hydrophobic

o PO4 = hydrophilic head

o Dual “personality”

o interaction with H2O is

complex & very important!

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Phospholipids in Water

• Hydrophilic heads attracted to H2O

• Hydrophobic tails “hide” from H2O

o self-assemble into aggregates

� micelle

� liposome

� Early evolutionary stage of cell?

• Why is this important?

o Phospholipids define outside vs. inside

o Where do we find phospholipids in cells?

� Cell membranes

Phospholipids & Cells

• Phospholipids of Cell Membrane

o Double layer = bilayer

o Hydrophilic heads on outside

� In contact with aqueous

solution

o Hydrophobic tails on inside

� Form core

o Forms barrier between cell & external

environment.

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Steroids

• ex: cholesterol, sex hormones

• 4 fused C rings

o different steroids created by attaching different functional groups to rings.

• Diversity in Steroids

Cholesterol

• Important cell component

o Animal cell membranes

� Helps keep cell

membranes fluid

& flexible

o Precursor of all other

steroids

� Including

vertebrate sex

hormones.

o High levels in blood

may contribute to

cardiovascular disease.