1.5 Lipids Flashcards

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1
Q

What are the main groups of lipids?

A

Triglycerides and phospholipids

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2
Q

What are the roles of lipids?

A

Source of energy - when oxidised they provide lots of energy.
Waterproofing - as they are insoluble in water
Insulation - slow conductors of heat and help retain body heat
Protection - stored around delicate organs

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3
Q

What is a triglyceride made of?

A

glycerol and three fatty acids.

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4
Q

What type of bond does each fatty acid form with glycerol?

A

Ester bond

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5
Q

Why are triglycerides a good source of energy?

A

They have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms.

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6
Q

Why are lipids good storage molecules?

A

They have a low mass to energy ratio so lots of energy can be stored in a small volume

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7
Q

Why are triglycerides insoluble in water?

A

They are large and non-polar molecules

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8
Q

What is the advantage of lipids being insoluble?

A

Their storage does not affect osmosis in cells or the water potential of them.

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9
Q

What is a phospholipid made up of?

A

A hydrophilic head that attracts which interacts with water.
A hydrophobic tail which mixes readily with fat

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10
Q

What can phospholipids form in an aqueous environment?

A

A phospholipid bilayer

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11
Q

How does the phospholipid structure allow them to form glycolipids?

A

By combining with carbohydrates within the cell surface membrane.

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12
Q

Describe the difference between the structure of a triglyceride molecule and a phospholipid molecule.

A

In phospholipid, one fatty acid is replaced by phosphate.

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13
Q

Describe how you would test for the presence of a lipid in a food sample.

A

Add ethanol then add water.
White emulsion appears if lipid is present.

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14
Q

Describe how a saturated fatty acid is different from an unsaturated fatty acid.

A

Saturated - single bonds between carbons
Unsaturated - at least one double bond between carbon

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15
Q

Suggested why a fat substitute may not be digested in the gut by lipase?

A

The fat substitute is not complementary so no enzyme-substrate complex is formed

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16
Q

Suggest why a lipid might not be able to cross the cell-surface membrane?

A

It is hydrophilic/polar