Biology - Lipids - Flashcards in A Level and IB Biology

State the elements present in lipids (and the additional element in phospholipids)

Carbon, hydrogen, oxygen (and phosphorus)

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Define the term 'macromolcule'

A large molecule essential for life

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State the 3 categories of lipids (or lipid-derived molecules)

Triglycerides, phospholipids, sterol

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State the components of a triglyceride

Glycerol, 3 fatty acids

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Describe the difference between saturated, monounsaturated and polysaturated fatty acids/triglycerides

Saturated = no double bonds between carbon atoms, monounsaturated = one double bond between carbon atoms, polyunsaturated = more than one double bond between carbons

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Explain why saturated triglycerides tend to be solid (fats) at room temperature, whereas unsaturated triglyerides tend to be liquids (oils)

The presence of double nonds causes the molecules to kink or bend, so they can't pack so closely together, meaning unsaturated lipids are liquid at room temperure, as the molcules are less dense than saturated lipids

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Describe and explain how the melting point would correlate with the length of the fatty acids it contains

The melting point would decrease as the chain got longer because, the longer the chain, the less easy it is for triglycerides to pack together so closely

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State the property that each end of the phospholipid has

Head = hydrophilic, tail = hydrophobic

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Describe the difference between a triglyeride and a phospholipid

Phospholipids contain a phosphate group and 2 fatty acids, whereas a triglyceride contains a glycerol molecule and 3 fatty acids

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Name the bond that holds the building blocks of a triglyceride together

Ester bond

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State the reaction that forms triglycerides

Condenstation reaction

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State the reaction that breaks triglycerides apart

Hydrolysis reaction

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Explain how an ester bond is formed

The H group of glycerol and the OH group of the fatty acids bond to form water, and this is expelled - bonds then form between the O and the C where the H2O has been lost

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State the number of water molecules produced in the production of one triglyeride

3

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State the products of digestion of a triglyceride and state what would happen to the pH of the solution, and why

The products would be glycerol and fatty acids, which would lower the pH, because fatty acids are acidic

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Describe the structure of sterols/cholesterol

They are complex alcohol molecules, based on a 4 carbon ring structure, with a hydroxyl group at one end

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List 5 functions of triglycerides

Provide thermal insulation, cushioning to protect vital organs, buoyancy for aquatic animals, electrical insulation for impulse transmission and waterproofing

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List 2 functions of phospholipids

Membrane formation (hydrophilic and hydrophobic regions), and can form a layer on the surface of water

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List 2 functions of cholesterol

Formation of cell membranes (adding stability and regulating fluidity), and manufactues vitamin D, steroid hormones and bile

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Explain why triglycerides store more energy per gram than carbohydrates

Carbohydrates have more oxygen in them per gram than lipids do, which doesn't contribute to energy storage

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Explain how phospholipids form a membrane

The hydrophilic heads will be attratcted to water, but the hydrophobic tails will be repelled by it, so there are 2 layes of phospholipids, with their tails facing away from the watery environment and their heads facing towards it

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Describe how the presence of cholesterol affects the properties of cell membranes

It adds stability and regulates fluidity

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Biology - Lipids

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