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LIPIDMetabolism.ppt© 2010 Pearson Education, Inc.
LIPIDS
© 2010 Pearson Education, Inc.
Lipids
- Large and diverse group of naturally occurring organic compounds
- Contain carbon, oxygen, and hydrogen
- Hydrophobic
- Category of compounds that includes
Triglycerides
Sterols
Phospholipids
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
Lipids
- Basic functions in the body
Store and provide energy
Fats provide 9 kcal per gram
Provide insulation
Help produce steroids and bile salts
Play a role in transporting fat-soluble nutrients in the blood
Used to manufacture major reproductive hormones
Key to the structure of cell membranes
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Fatty Acids
- Building blocks for triglycerides and phospholipids
- A chain of carbon and hydrogen atoms with a carboxyl group at the alpha end and a methyl group at the omega end
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Fatty Acids Vary in Length
Short-chain fatty acids
Two to four carbons
Weak attraction
Liquid at room temperature
Medium-chain fatty acids
six to ten carbons
Long-chain fatty acids
12 or more carbons
Most common type of fatty acid in foods
Strong attraction
Solid at room temperature
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Fatty Acids Vary in Saturation
- Saturated
All the carbons on the fatty acid are bound to hydrogen
Solid at room temperature
Higher melting point
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Fatty Acids Vary in Saturation
- Unsaturated
Some carbons on fatty acid form a double bond with each other instead of binding to hydrogen
Monounsaturated fatty acids (MUFA)
Has one double bond
Polyunsaturated fatty acid (PUFA)
Has two or more double bonds
Liquid at room temperature
Lower melting point
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Saturated and Unsaturated Fatty Acids Help Shape Foods
Figure 5.3
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Figure 5.5
Fatty Acids Vary in Shape
- Unsaturated fatty acids form two different shapes
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Portion of Figure 5.7
Triglycerides
- Three fatty acids connected to a glycerol backbone
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Caution:
High levels in the blood are a risk factor for heart disease
Triglycerides
- Most common lipid in both foods and the body
- Make up about 95% of lipids found in foods
- Functions
Add texture
Makes meats tender
Preserves freshness
Stores as adipose tissue
for energy
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Trans Fats
- Trans fat may actually be worse for heart health than saturated fats
Raise LDL cholesterol
Lower HDL cholesterol
- FDA requires trans fat to be listed on food labels
- The food industry is working to find replacements for trans fats in foods
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Foods Containing Trans Fat
- Hydrogenated fats are used by many commercial food producers to
Provide rich texture
Increase shelf life
Decrease incidence of rancidity
- During the hydrogenation process trans fats form
- Some trans fats are naturally occurring
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Food Sources of Cholesterol and Plant Sterols
- Cholesterol comes mainly from animal products
- The cholesterol produced in plant cell walls and oils is so minimal they are considered cholesterol free
Functions of cholesterol
- Structural component of cell membrane
- Precursor for the synthesis of all other steroids in the body
- Essential ingredient in the structure of lipoprotein
- Fatty acids are transported to liver as cholesteryl esters for oxidation
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From
VLDL IDL LDL HDL
- Density increases
- Particles become smaller
- Decrease in TAG content – increase in protein content
- For VLDL IDL LDL, particles are also becoming enriched in cholesterol
Lipoproteins
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
Lipoproteins Transport Fat Through the Lymph and Blood
- Very low-density lipoproteins (VLDLs)
- LDLs: “bad” cholesterol
- HDLs: “good” cholesterol
- HDL and LDL levels can be used to determine the health of arteries
© 2010 Pearson Education, Inc.
© 2010 Pearson Education, Inc.
DESIRABLE BORDERLINE RISK
(mg/dl) (mg/dl) (mg/dl)
Total Cholesterol <200 200-239 240
LDL Cholesterol <130 130-159 > 160
HDL Cholesterol > 60 40-60 < 40
Lipid Profile
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Triglyceride GPO method
- For the in-vitro quantitative determination of Triglycerides in serum or plasma.
- Triglycerides determinations are of interest in the diagnosis and treatment of atherosclerosis, and to see the risk of CVD.
- Based on the enzymatic determination of glycerol using the enzyme glycerol phosphate oxidase (GPO) after hydrolysis by lipoprotein lipase.
- In the presence of peroxidase (POD) produces a red colored quinoneimine dye which absorbs at, or near 500nm. The intensity of the colored complex formed is directly proportional to the triglycerides concentration of the sample.
© 2010 Pearson Education, Inc.
Lipase
Triglycerides ------------------------------> Glycerol + Fatty Acids
GK (glycerol kinase)
Glycerol + ATP ------------------------> Glycerol-1-phosphate + ADP
GPO
Glycerol - 1 - phosphate + O2------------------------> DAP + H2O2
POD
H2O2 + 4-AA +4 -Chlorophenol ------------> Quinoneimine Dye (Red)
+ HCL+ 2H2O
Principle
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Spectrophotometry
- A method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution
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Spectrophotometer
- I0: incident light; I: Transmitted light
- T(Transmittance): I/ I0
- A(Absorbance): -log T
*
© 2010 Pearson Education, Inc.
Assignment
- Please finish the quiz within the class hour. This quiz will be counted as your attendance.
- Please write the lab report based on the video and results. Please calculate the concentration of Triglyceride unknown sample and Cholesterol unknown sample based on the results.
- In the discussion part, please discuss the function, health effects of triglyceride and cholesterol(HDL, LDL). In order to control lipid level, which kind of diets should we have?
