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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 bonds

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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

They 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 e.g alcohol.

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9
Q

Where are triglycerides found?

A

They are components of our diet (in fats and oils) which are stored in fat cells in the body.

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10
Q

What are triglycerides made from?

A
  • 1 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 polymers?

A

They are made from different subunits, not similar repeating units

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13
Q

What is the test for lipids? (Describe it)

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 of the lipid 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 carbon bonds, so form a linear carbon 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 form a bent chain

17
Q

What causes unsaturated fatty acid chains to bend?

A

Carbon to carbon double bonds

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 acid?

A

It means they are a solid at room temperature e.g. 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,
E.g vegetable oils.

22
Q

Where are phospholipids found?

A

In cell membranes

23
Q

Compare phospholipids structure to triglycerides structure

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?

A

The phosphate group has 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 slightly positive of hydrogen in water.

26
Q

Why do phospholipids have a hydrophobic tail?

A

The fatty acids are neutral (non polar) so not 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 than water so can help some organisms float e.g a 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 the nerves to increase the speed of electrical impulses

A Level Biology (13 decks)

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