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A Level Biology > Lipids > Flashcards

Lipids Flashcards

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1
Q

What are the two types of lipids?

A

Triglycerides
Phospholipids

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2
Q

What are the bonds which form between lipids?

A

Ester bond

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3
Q

How many water molecules are formed when a triglyceride is formed?

A

The condensation reaction produces 3 ester bonds and 3 water molecules

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4
Q

When a hydrolysis reaction occurs what happens to the triglyceride?

A

It is split by the addition of 3 water molecules (which breaks the 3 ester bonds)

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5
Q

What do all lipids contain?

A

-Carbon
-Hydrogen
-Oxygen

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6
Q

What property of lipids means they cannot dissolve in water?

A

Lipids are insoluble because they are non-polar molecules so aren’t attracted to water

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7
Q

Why are lipids non-polar molecules?

A

The have a large number of carbon and hydrogen molecules

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8
Q

What type of substances are lipids soluble in?

A

They are soluble in other organic solvents like alcohol (eg. ethanol)

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9
Q

Where are triglycerides found?

A

They are component of our diet (in fats and oils) which are stored in fat cells in the body (adipose tissue)

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10
Q

What are triglycerides made from?

A
  • One Glycerol
  • 3 Fatty Acids
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11
Q

What forms a fatty acid?

A
  • Long hydrocarbon chain
  • Carboxyl Group (COOH)
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12
Q

Why aren’t lipids (triglycerides) polymers?

A

They are made from different sub units not similar repeating units (monomers)

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13
Q

What is the test for lipids?

A
  • Mix the sample being tested with alcohol (ethanol) in a test tube
  • Shake tube thoroughly and add cold water
  • if a milky white emulsion is formed then this indicates the presence of a lipid
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14
Q

What is the positive result for the emulsion (lipids) test?

A

Milky white emulsion forms

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15
Q

What is a saturated fatty acid?

A

They only have single carbon to carb if bonds so form a linear hydrocarbon chain

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16
Q

What is an unsaturated fatty acid?

A

They have one or more carbon to carbon double bond which forms bent chains

17
Q

What causes unsaturated fatty acid chains to bend?

A

Double carbon to carbon bond

18
Q

Why do saturated fatty acids have a high melting point?

A

The intermolecular forces between the chains are strong and require a lot of energy to overcome

19
Q

What property does a high melting point give saturated fatty acids?

A

It means they are solid at room temperature
Eg. Butter

20
Q

Why do unsaturated fatty acids have a low melting point?

A

As the fatty acid chains are bent they form an irregular pattern and cannot fit tightly together.
This means the intermolecular attractions are weaker so are more easily broken

21
Q

What property does a low melting point give unsaturated fatty acids?

A

It means they are liquid at room temperature
Eg. Vegetable Oils

22
Q

Where are phospholipids found?

A

In cell membranes as a bilayer

23
Q

Compare phospholipids structure to triglycerides?

A

Triglycerides are formed from one glycerol and 3 fatty acids
Phospholipids are formed from a phosphate group, glycerol and 2 fatty acids

24
Q

Why are phospholipids polar molecules?

A

The phosphate group had a negative charge which means it’s slightly attracted to hydrogen molecules in water.

25
Q

Why do phospholipids have hydrophilic ‘heads’?

A

The phosphate group is negative and so attracted to the slight positive of hydrogen in water

26
Q

Why do phospholipids have a hydrophobic ‘tail’?

A

The fatty acids are neutral (non-polar) so aren’t attracted to water

27
Q

What are the 6 roles of lipids?

A
  • Source of energy
  • Waterproofing
  • Insulation
  • Protection
  • Buoyancy
  • Electrical insulator
28
Q

How do lipids provide waterproofing?

A

Waxy, lipid cuticles found in plants conserve water (reduce loss)

29
Q

How do lipids provide insulation?

A

Fats are slow conductors of heat and a layer of fat stored under the skin can retain heat

30
Q

How do lipids provide buoyancy?

A

Fats are less dense that water so can help some organisms float (eg. Seal)

31
Q

How do lipids provide protection?

A

They are often found around delicate organs like kidneys

32
Q

How do lipids provide electrical insulation?

A

They surround nerves to increase the speed of electrical impulses

A Level Biology (19 decks)

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