MCB 2000 Exam 2 Laux UPDATED ACTUAL Questions and
CORRECT Answers
What defines a lipid? Defined by solubility and interaction with water
What defines a protein? Defined by amino acid sequence
What defines carbohydrates? Defined by carbonyl chemistry and stereochemistry
, What defines nucleic acids? Defined by sequence of nucleotides
Key structural features of a fatty acid - Carboxyl acid end (hydrophilic)
- Methyl group end
- Hydrocarbon chain (hydrophobic)
- Usually even number of carbons
Saturated Fatty Acids - All single bonds between carbons
- All carbons maximally hydrogenated
- Straight geometry
Unsaturated Fatty Acids - One or more double bonds
- Typically cis configuration
- Cis double bonds create "kinks" or bends in chain
"Essential" Fatty Acids Humans cannot introduce double bonds beyond carbon 9
Humans cannot synthesize: - Omega-3 fatty acids
- Omega-6 fatty acids
Fatty Acids: Biological Relevance - Incorporated into membrane phospholipids
- Precursors to lipid signaling molecules (eicosanoids)
- Associated with cardiovascular and neurological health
Triacylglycerols Nature's Energy Reservoir
Triacylglycerols Structural Features - Glycerol backbone
- Three fatty acids
- Linked by ester bonds
- Chemically neural and fully hydrophobic
Triacylglycerols Functional Consequences - Do not form membranes
- Stored in lipid droplets
- Designed for long-term energy storage
Why Store Energy as Fat? Energy density and storage efficiency
Energy Density of Fatty Acids - Fatty acids contain highly reduced carbon
- Rich in C-H bonds
- Oxidation yields more ATP per carbon
- 9 kcal/gram (fat) versus 4 kcal/gram (carbohydrate)
Storage Efficiency of Fatty Acids - Glycogen bonds significant amounts of water
- Triacylglycerol are hydrophobic and hence, stored in nearly anhydrous form
- Mass-efficient
Membrane Lipids Built for boundaries
CORRECT Answers
What defines a lipid? Defined by solubility and interaction with water
What defines a protein? Defined by amino acid sequence
What defines carbohydrates? Defined by carbonyl chemistry and stereochemistry
, What defines nucleic acids? Defined by sequence of nucleotides
Key structural features of a fatty acid - Carboxyl acid end (hydrophilic)
- Methyl group end
- Hydrocarbon chain (hydrophobic)
- Usually even number of carbons
Saturated Fatty Acids - All single bonds between carbons
- All carbons maximally hydrogenated
- Straight geometry
Unsaturated Fatty Acids - One or more double bonds
- Typically cis configuration
- Cis double bonds create "kinks" or bends in chain
"Essential" Fatty Acids Humans cannot introduce double bonds beyond carbon 9
Humans cannot synthesize: - Omega-3 fatty acids
- Omega-6 fatty acids
Fatty Acids: Biological Relevance - Incorporated into membrane phospholipids
- Precursors to lipid signaling molecules (eicosanoids)
- Associated with cardiovascular and neurological health
Triacylglycerols Nature's Energy Reservoir
Triacylglycerols Structural Features - Glycerol backbone
- Three fatty acids
- Linked by ester bonds
- Chemically neural and fully hydrophobic
Triacylglycerols Functional Consequences - Do not form membranes
- Stored in lipid droplets
- Designed for long-term energy storage
Why Store Energy as Fat? Energy density and storage efficiency
Energy Density of Fatty Acids - Fatty acids contain highly reduced carbon
- Rich in C-H bonds
- Oxidation yields more ATP per carbon
- 9 kcal/gram (fat) versus 4 kcal/gram (carbohydrate)
Storage Efficiency of Fatty Acids - Glycogen bonds significant amounts of water
- Triacylglycerol are hydrophobic and hence, stored in nearly anhydrous form
- Mass-efficient
Membrane Lipids Built for boundaries
