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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.
3
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…
4
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.
2
• 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!
3
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.