lipids ib biology topic 3. starter! what are lipids? lipids are complex molecules composed of...
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Lipids
IB BiologyTopic 3
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Starter!
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What are lipids?
• Lipids are complex molecules composed of carbon, hydrogen, and oxygen.
• Most lipids are non-polar and are hydrophobic because they contain hydrocarbon chains.
• If there are double or triple bonds in the hydrocarbon chain the lipids are said to be “unsaturated”
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Lipid Functions
• Energy storage: Fats and oils.• Waterproofing: Waxes and oils• Insulation: Fat layers (blubber)• Cushioning: Fat layers (soles of
your feet)• Regulating metabolic processes:
Steroids• Building component of cell
membranes: Phospholipids
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Lipid structure (Triglyceride)
• A triglyceride is composed of an alcohol called glycerol covalently bonded to three fatty acid molecules by condensation reactions.
• This process forms three ester groups between the alcohol and one with each fatty acid chain.
Is this a saturated or unsaturatedFat? Why or Why not?
It is saturated because there are no double bonds between carbon atoms in the fatty acid hydrocarbon chains.
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Saturated vs. Unsaturated Fats• When double bonds form in hydrocarbon chains it causes them to bend.
• In unsaturated fats this prevents the molecules from being able to “stack” or “pack” themselves tightly, thus they remain in a liquid state at room temperature such as oils.
• If the hydrocarbon chains are saturated, the chains are straight and pack themselves close together forming a solid at room temperature (animal fat, butter, tallow, lard).
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Steroids• Steroids are cyclic hydrocarbons
usually composed of four rings.
• They are involved with regulating metabolic processes in the body because many forms of them are hormones.
• Testosterone, oestrogen, and progesterone are all examples of steroid hormones.
• Cholesterol is the most common steroid!
• It is the building block for other steroid hormones and also functions in cell membrane structure.
Cholesterol
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Phospholipids• Phospholipids are a special class of lipids composed of a
phosphate group, glycerol molecule, and two fatty acid chains.
• The phosphate region of the molecule is polar because it is negatively charged.
• This makes it attracted to water or hydrophilic because of waters bipolar nature.
• The fatty acid chain region is composed of hydrocarbon chains which are very non-polar, therefore this end is hydrophobic or repels water.
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Phospholipid Structure