Summary of Textbook Section 5.3

Assignment:

Write a summary of 5.3

Section 5.3: Lipids include fats and steroids

defining key terms:

• lipid: "one if a class of water-avoiding compounds" (Campbell, 826)
• hydrophobic: "avoids water molecules" (Campbell, 825)
• fat: "organic compound consisting of three-carbon backbone (glycerol) attached to three fatty acids" (Campbell, 823)
• saturated fat: "fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms" (Campbell, 830)
• unsaturated fat: "fat with less than the maximum number of hydrogens in one or more of its fatty acid chains" (Campbell, 832)
• steroid: "lipid molecule with four fused carbon rings" (Campbell, 830)
• cholesterol: "steroid molecule present in the plasma membranes of animal cells" (Campbell, 821)

Lipids

• hydrophobic
• act as boundary surrounding aqueous material in cell (traps water)
  
• or circulate body as chemical signals
• or store energy -> fatimage from: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/hydropho.htm
  

Fats

• structure with backbone of glycerol, has 3 chains, each with fatty acids protruding
• functions: energy, insulation, cushion organs
• if uses max number of H, CH single bonds and extra H, saturated
• if uses CH double bond, unsaturated
• unsaturated: fruits, vegetables, fish (e.g. olive and corn oil)
• saturated fat unhealthy, builds plaque in blood vessels -> reduce blood flow and increase heart disease

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.3.html

Steroids

• structured as 4 carbon skeleton rings and 2 functional groups on each end
• differing locations and types of functional groups
• are lipids and hydrophobic, but different from fat
• functions: chemical signals, surround water in cells

Types of steroids

• estrogen: female sex hormone
  
• testosterone: male sex hormone
  
• cholesterol: raw material for other steroids, can increase risk for cardiovascular disease
  

image from: http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter5/concept5.3.html

Concept check:

1. Property of lipids? All lipids are hydrophobic.
   
2. Parts of a fat molecule? Fat molecules "[consist] of three-carbon backbone (glycerol) attached to three fatty acids" (Campbell, 823).
3. Differences of steroids and fats? Steroids consist of 4 fused carbon rings, while fat consists of 3-carbon backbones attached to 3 fatty acids. Steroids are used as chemical signals and surround water in cells, while fat stores energy.
   
4. Meaning of unsaturated fat on food labels? Unsaturated fat has "less than the maximum number of hydrogens in one or more of its fatty acid chains" (Campbell, 832). Unsaturated fat is often healthier than saturated fat, and would be used to indicate vegetable oils on food labels.