Lipids

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What are lipids?
Fats and oils
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How are lipids different from proteins and carbohydrate?
Not polymers as they don't have a repeating monomer
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What gives a lipid its function?
What it is made from
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What are the two types of lipids?
Triglycerides and phospholipids
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What is a triglyceride made from?
Glycerol and 3 different types of fatty acids
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What makes each fatty acid different?
Its hydrocarbon tail, which is the 'R' group
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What region of triglyceride is hydrophobic?
Fatty acids
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What is the unbonded molecular formula of a triglyceride?
Glycerol (CH2OHCHOHCH2OH) Fatty acid (H-O-C=O and R group also bonded to C)
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What bond holds glycerol and fatty acids together?
Ester bond
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What type of reaction forms an ester bond, and what else is formed?
Condensation and a molecule of water
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Where does the ester bond form?
H of glycerol and OH of fatty acid
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How many ester bonds are present in a triglyceride?
3 - one for each fatty acid
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What reaction breaks triglyceride and how?
Hydrolysis, adds molecule of water
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How many molecules of water are released when a triglyceride is hydrolysed?
3 - one for every ester bond
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What types of hydrocarbon tails are they?
Saturated (no double bonds) mono unsaturated (1 double bond) and poly unsaturated (2+double bonds)
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What type of hydrocarbon tails form fats (solids)?
Unsaturated, the tails are straight as no double bonds present, therefore london forces between tails are stronger, so more energy required to break the bonds
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What type of hydrocarbon makes oil (liquids)?
Monounsaturated and polyunsaturated, the double bond causes the tail to be bent so london forces between tails is weaker so less energy required to break bond
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What is the function of triglycerides?
Energy strore
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Where are triglycerides stored?
Adipose tissue
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What is the structural difference between triglycerides and phospholipids?
Phospholipid has one of the fatty acid groups replaced by a phosphate group
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Where on the phospholipid is the phosphate located?
The opposite side of the glycerol to the hydrocarbon tails
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What region of the phospholipid is hydrophobic and why?
Fatty acid tails - non polar
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What region of the phospholipid is hydrophilic and why?
phosphate group and glycerol - phosphate group is negatively charged
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What do phospholipids look like when in a water droplet?
Hydrophilic head inside droplet, hydrophobic tails sticking out
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What structure are phospholipids a main component of?
Cell membrane
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What kind of layer do phospholipids form in the cell membrane and what does this mean?
Bilayer and layer of 2
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How are phospholipids arrange in the bilayer?
Bottom layer of phospholipids' hydrophilic head is inside the cell, the hydrophobic tails are sticking out, the hydrophobic tails of the top layer are slotted into the bottoms' tails and the hydrophilic head is out, creating a hydrophobic region
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What molecules find it difficult to pass through the cell membrane and why?
Water soluble because they are charged and the hydrophobic region of the cell membrane doesn't like charged molecules
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What do lipids have to be to be 'easily absorbed and fit into cells'?
Digested
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What kind of reaction digests lipids?
Hydrolysis
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What enzyme digests lipids and where is it made and secreted into?
Lipase, made in the pancreas, secreted into the small intestine
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How does lipase digest lipids?
Cleaves (cuts) the ester bond between glycerol and fatty acids
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What is the products of lipid digestion?
3 fatty acids and a glycerol molecule
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Where are bile salts produced?
Liver
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What do bile salt do to lipids?
Surround them and stabilises them (makes them turn into smaller droplets of lipids)
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How do smaller droplets of lipids help speed up digestion?
Smaller droplets of lipids have bigger surface are so lipase can work quicker on hydrolysing the ester bonds on the lipids
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When the smaller droplets are formed they sill have bile slats surrounding them. What are these structures called?
Micelles
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What is the function of micelles?
Help transport products of lipid digestion to epithelium of small intestine
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Because micelles are constantly breaking up and reforming, what does this release and what for?
Glycerols and fatty acids for absorption
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Because micelles are lipid soluble, what does it mean they can pass through?
The phospholipid bilayer in the cell membrane of the epithelium cells
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Why does the pH of milk lower once lipase has been added?
Triglycerides in milk being digested by lipase, therefore releasing fatty ACIDS which lower the pH of the milk
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Why does the pH eventually plateau?
All of the lipase could have been used
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Lipids can transfer lipid soluble substances but not ..?.. soluble substances
Water
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Why do lipids release more energy than carbohydrates?
More C-H bonds, phosphate group can be released quickly in phospholipids, releases more water when hydrolysedq
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Name 3 uses of lipids since they are not water soluble.
Waterproofing and forming waxy cuticle on plants and insects (to help them conserve water) and being secreted from mammals (form waterproof layer)
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Because lipids are slow conductors of heat they can be used as ..?..
Insulators underneath the surface of the body
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Where in the body does lipids form protection?
Around delicate organs e.g the kidneys
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What test is the test for lipids?
Ethanol emulsion test
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Describe steps for ethanol emulsion test
1. Mash food sample with 2cm^3 of ethanol in pestle and mortar, 2.filter into dry test tube, 3. Add 2cm^3 of distilled water and shake, 4. Allow to settle
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What is the observation of a positive result in the ethanol emulsion test?
Off white coloured layer at the top of the test tube
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Other cards in this set

Card 2

Front

How are lipids different from proteins and carbohydrate?

Back

Not polymers as they don't have a repeating monomer

Card 3

Front

What gives a lipid its function?

Back

Preview of the front of card 3

Card 4

Front

What are the two types of lipids?

Back

Preview of the front of card 4

Card 5

Front

What is a triglyceride made from?

Back

Preview of the front of card 5
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