Lipids Flashcards
Are lipids polar or non-polar and what effect does this have on its solubility.
Lipids are non-polar compounds and so are insoluble in water,
But dissolve in organic solvents, such as propanone and alcohols.
Describe the formation of triglycerides (drawing if possible too)
they are formed by the combination of one glycerol molecule and three molecules of fatty acids.
The glycerol molecule is always the same but the fatty acid component varies.
The fatty acids join to glycerol by condensation reactions, whereby three molecules of water are removed and ester bonds are formed between the glycerol and fatty acids.
State the three elements contained in both lipids and carbohydrates and the difference between these.
Like carbohydrates, lipids contain carbon, hydrogen and oxygen but, in proportion to the carbon and hydrogen, they contain much less oxygen.
Give an example of a lipid, it’s properties and its role in animals and plants.
waxes are lipids and melt above 45°c.
They have a waterproofing role in both animals and plants.
E.g. Insect exoskeleton and leaf’s cuticle.
What determines the difference between fats and oils?
The variations in the fatty acids.
Describe the structure of a saturated fatty acid (and draw it if possible).
If the hydrocarbon chain has only single carbon-carbon bonds, then the fatty acid is saturated
Because all of the carbon atoms are linked to the maximum possible number of hydrogen atoms.
That is, they are saturated with hydrogen atoms.
The fatty acid chain is a straight zig zag.
Why are saturated fatty acids solids at normal temperatures and why is this useful?
The fatty acid chain is a straight zigzag and the molecules can align readily so fats are solid.
Therefore, they are useful for storage in mammals. Animal lipids often Fontaine saturated fatty acids.
Describe the structure of an unsaturated fatty acid (and draw a diagram if possible).
Also state why they are oils at normal temperature.
If any carbon-carbon bond is not a single bond, the molecule is unsaturated and the chain gets a kink.
This is why unsaturated lipids are oils.
What does the term mono-unsaturated mean?
If only one carbon-carbon double bond is present.
What does the term polyunsaturated mean?
If there are many carbon-carbon double bonds.
What type of lipids do plants usually have and give two examples.
Plant lipids are often unsaturated and occur as oils, such as olive oil and sunflower oil.
State and describe (where possible) the two roles of phospholipids.
- In biological membranes
- Electrical insulation: the myelin sheath that surrounds the axons of nerve cells.
State and describe the four roles of triglycerides
- Energy reserves in both plants and animals- because lipids contain more carbon-hydrogen bonds than carbohydrates.
- Thermal insulation- when stored under the skin, lipids insulate against heat loss in the cold or heat gain when it’s very hot.
- Protection- fat is often stores around delicate internal organs such as kidneys, protesting against physical damage
- Metabolic water-this is water released during chemical reactions in the body. Triglycerides produce a lot of metabolic water when oxidized.
What is the role of waxes with examples
Water proofing- in terrestrial organisms, waxes reduce water loss, such as in the insect exoskeleton and in the cuticle of plants.
What are the main causes of heart disease? Also give the scientific name for these two factors.
Fatty acids in the coronary arteries (atherosclerosis) and high blood pressure (hypertension.).
