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Biology Topic 1A > Lipids > Flashcards

Lipids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are lipids commonly known as?

A

Fats or oils.

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2
Q

Why are lipids different from proteins and carbohydrates?

A

Because they are not polymers formed from long chains of monomers.

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3
Q

What are lipids made from?

A

A variety of different components.

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4
Q

What do all lipids contain?

A

Hydrocarbons.

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5
Q

What do the components lipids are made from relate to?

A

Their functions.

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6
Q

What two types of lipid do you need to know about?

A
  • Triglycerides

* Phospholipids

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7
Q

What is the structure of a triglyceride molecule?

A

One molecule of glycerol with three fatty acid molecules attached to it.

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8
Q

What is the structure of fatty acid molecules?

A

They have long ‘tails’ made of hydrocarbons.

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9
Q

What do fatty acids do in water?

A

They repel water molecules (they are hydrophobic).

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10
Q

What do the hydrophobic fatty acid tails make lipids?

A

Insoluble in water.

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11
Q

What do triglyceride molecules look like?

A

image

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12
Q

What do all fatty acids consist of?

A

The same basic structure.

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13
Q

What varies within all fatty acids?

A

The hydrocarbon tail (R group).

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14
Q

What are the two types of fatty acids?

A
  • Saturated

* Unsaturated

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15
Q

What is the structure of a fatty acid?

A

image

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16
Q

Where is the difference between saturated and unsaturated fatty acids?

A

In their hydrocarbon tails (R group).

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17
Q

What is the difference between saturated and unsaturated fatty acid hydrocarbon tails?

A

Saturated fatty acids don’t have any double bonds between their carbon atoms whereas unsaturated fatty acids do.

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18
Q

What are saturated fatty acids saturated with?

A

Hydrogen.

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19
Q

What do the double bonds in unsaturated fatty acids do?

A

Cause the chain to link.

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20
Q

What do saturated fatty acids look like?

A

Image

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21
Q

What do unsaturated fatty acids look like?

A

Image

22
Q

How are triglycerides formed?

A

By condensation reactions.

23
Q

What bond forms when triglycerides are formed by condensation reactions?

A

An ester bond.

24
Q

What happens when an ester bond is formed during triglyceride formation?

A

A molecule of water is released (this is a condensation reaction).

25
Q

How many times does a condensation reaction occur to form a triglyceride?

A

Three times.

26
Q

What does the condensation reaction forming a triglyceride molecule look like?

A

Image

27
Q

Which type of lipids are found in cell membranes?

A

Phospholipids.

28
Q

What are phospholipids, compared to triglycerides?

A

Very similar except one of the fatty acid molecules is replaced by a phosphate group.

29
Q

What does the phosphate group in phospholipids do in water?

A

They attract water (they we are hydrophilic).

30
Q

Where is the hydrophilic phosphate group and the hydrophobic fatty acid tail in a phospholipid important?

A

In the cell membrane.

31
Q

What does a phospholipid look like?

A

Image

32
Q

What do we need to know about triglyceride and phospholipid structures?

A

How they relate to their properties:

33
Q

What are some uses of lipids?

A
  • As certain hormones (e.g. testosterone)

* As respiratory substrates (molecules used in respiration to release energy).

34
Q

What are triglycerides mainly used as?

A

Energy storage molecules.

35
Q

Why are triglycerides good as energy storage molecules?

A

Because the long hydrocarbon tails of the fatty acids contain lots of chemical energy and loads of energy is released when they’re broken down.

36
Q

What do lipids contain compared to carbohydrates due to the fatty acid tails?

A

About twice as much energy per gram as carbohydrates.

37
Q

What happens when you mix triglycerides in water?

A

They don’t affect water potential of the cell as they’re insoluble in water.

38
Q

Why is it good that triglycerides don’t affect water potential of the cell?

A

Because they don’t cause water to enter the cells by osmosis (which would make them swell).

39
Q

How do triglycerides avoid making water enter the cell by osmosis?

A

Many triglycerides bundle together as insoluble droplets in cells.

40
Q

How do triglycerides make insoluble droplets with other triglycerides?

A

When they bundle together the fatty acid tails face inwards, shielding themselves from water with their glycerol heads.

41
Q

Why do storage molecules need to be insoluble?

A

Because if they weren’t they would just dissolve and release what they were storing whenever they came into contact with water.

42
Q

What do insoluble triglyceride droplets look like?

A

Image

43
Q

What do phospholipids do?

A

They make up the bilayer of cell membranes.

44
Q

What do cell membranes do?

A

They control what enters and leaves a cell.

45
Q

How are phospholipid bilayers structured?

A

They form a double layer with their hydrophilic heads facing out towards the water on either side and their hydrophobic tails facing inwards.

46
Q

What do phospholipid bilayers act as?

A

A barrier to water-soluble substances.

47
Q

Why are phospholipids good at making up the bilayer of cell membranes?

A

Because water-soluble substances can’t easily pass through it as the centre of the bilayer is hydrophobic due to the fatty acid tail.

48
Q

What does a phospholipid bilayer look like?

A

Image

50
Q

How do you test for the presence of lipids in a sample?

A

By doing the emulsion test.

51
Q

What is the method of the emulsion test for lipids?

A
  • Shake the test substance with ethanol for about a minute.

* Pour the solution into water.

52
Q

What is the result of the emulsion test for lipids if lipids are present?

A

The lipid will show up as a milky emulsion (the more lipid there is, the more noticeable the milky colour will be).

53
Q

What does the emulsion test for lipids look like?

A

Image

Biology Topic 1A (8 decks)

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