Triglycerides, diet and health Flashcards
Draw the cis and trans configurations of a carbon double bond.
Why are cis fats liquids at room temperature and trans fats solids at room temperature.
In nature, unsaturated fatty acids normally exist in the cis form.
- In the cis form, the unsaturated fatty acid molecules cannot pack closely together, and cis fatty acids exist as liquids at room temperature.
- The trans form of an unsaturated fatty acid is quite linear in its structure and the fatty acid chains can pack together closely. Consequently a trans-unsaturated fatty acid will always have a higher melting point than its cis isomer.
Explain how the food industry produces unhealthy fats.
The food industry used a lot of unsaturated fats and oils. However, often some of the double bonds are removed by partial hydrogenation to make the fats and oils more solid, as in margarine manufacture. A side effect of hydrogenation is that the remaining double bonds may be structurally changed, with many being convertered from the cis form to the less healthy trans form.
What are lipoproteins?
Lipoproteins are particles that carry lipids such as cholesterol and fats, through the blood.
What are high-density lipoproteins(HDLs)?
high-density lipoproteins are believed to transport cholesterol out of the blood, and eventually out of the body. HDLs are commonely referred to as ‘good’ lipoproteins.
What are low-density lipoproteins(LDLs)?
Low-density lipoproteins carry about 65% of the cholesterol in blood. LDLs can deposit lipids onto artery walls, building up fatty deposits that restrict blood flow.
Trans fatty acids are thought to behave like saturated fats in the body. They raise LDL levels and increase the risk of heart disease. They also tend to lower HDL levels, so they are potentially even more damaging.
Draw out the general reaction for producing biodiesel from triglycerides and explain the process.
Triglycerides in fats and oils are reacted with methanol or ethanol in the presence of a sodium(or potassium) hydroxide catalyst. Glycerol is also formed and is sold to the pharmaceutical or cosmetics industries, improving the atom economy of the process.
What are some of the main advantages of biodiesel?
- Claimed to be carbon neutral because when the ‘fuel crop’ grows it absorbs the same amount of carbond dioxide as is released when the fuel is burnt.
- Renewable, we are not using limited oil supplies.
What are the disadvantages of biofuels?
- Land used for producing biofuels is taking away land that can be used to make food, food prices increases and this leads to poorer counties not being able to afford food.
- Poor biodiversity in crops because only one type of crop.
- The process is not that efficient, not much energy is gained from the next process.
