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Biology > Topic 1—A: Biological molecules- 4. lipids > Flashcards

Topic 1—A: Biological molecules- 4. lipids Flashcards

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1
Q

what are lipids commonly known as?

A

fats or oils

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2
Q

how are lipids different from carbohydrates and proteins?

A

they aren’t polymers formed from long chains of monomers

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3
Q

what are lipids made from?

A

they are made from a variety of different components
- they all contain hydrocarbons

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4
Q

what are hydrocarbons?

A

molecules that contain only hydrogen and carbon atoms

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5
Q

what are the two types of lipids?

A

triglycerides
phospholipids

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6
Q

triglycerides structure

A
  • they have 1 molecule of glycerol
  • 3 fatty acids attached to it
  • fatty acid molecules have long ‘tails’ of hydrocarbons
  • tails are hydrophobic so they repel water molecules which make lipids insoluble in water.
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7
Q

fatty acids (structure)

A
  • consist of the same basic structure
  • hydrocarbon tail varies
  • they have a carbon atom that links fatty acid to glycerol
  • Variable ‘R’ group hydrocarbon tail
  • Carboxyl group (COOH)
    O

    C-R
    /
    HO
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8
Q

what are the three kinds of fatty acids and the main difference?

A

saturated, unsaturated and polyunsaturated
Difference is in their hydrocarbon tails (R groups)

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9
Q

Saturated fatty acids

A
  • Don’t have any double bonds between their carbon atoms (no c=c bond)
  • The fatty acid is saturated with hydrogen
  • Form straight chains and have high melting points
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10
Q

Unsaturated fatty acids

A
  • Do have double bonds between carbon atoms (c=c bond)
  • Cause the chain to kink
  • Form bent chains and have low melting points
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11
Q

Polyunsaturated fatty acids

A
  • More than 1 double bond between carbon atoms (more than 1 c=c bond)
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12
Q

Triglycerides (glycerol)

A

H
I
H-C-OH- Fatty acid
I
H-C-OH- Fatty acid
I
H-C-OH- Fatty acid
I
H
3 carbon groups
3 hydroxl groups

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13
Q

How are triglycerides formed?

A
  • Formed by condensation reactions
  • Fatty acids join to a glycerol molecule (at the OH) (Hydroxl part)
  • As 3 fatty acids joins to 3 different OH groups, 3 condensation reactions are happening so 3 molecules of water are produced.
  • An ester bond forms between the 2 molecules (the OH of the glycerol and HO of the fatty acid) which releases a molecule of water.
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14
Q

Phospholipid (structure)

A
  • They have one molecule of glycerol
  • 2 fatty acids attached to it (Hydrocarbon tail)
  • 1 phosphate group
  • Glycerol and fatty acids are connected by an ester bond
  • Phosphate group is hydrophilic (attracts water) (heads face outwards towards the water on either side)
  • Fatty acid tails are hydrophobic (repels water)
  • Centre of bilayer is hydrophobic so water-soluble substances can’t pass through it. (acts as a barrier)
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15
Q

Emulsion test (lipids)

A
  • Add ethanol to a test substance
  • Shake test substance with ethanol for about 1 minute
  • Add distilled water and shake
  • Any lipid will show up as a white milky emulsion (more lipid there is the more noticeable the milky colour will be)
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16
Q

Properties of lipids (triglycerides)

A
  • Mainly used as energy storage molecules (good for this because the long hydrocarbon tails of the fatty acids contain lots of chemical energy) which means a lot of energy is released when they are broken down. (respiration)
  • They are insoluble in water so they don’t affect water potential of the cell and cause water to enter the cells by osmosis (which would make them swell)
  • High carbon and hydrogen concentration means they contain more energy per gram than carbohydrates.
17
Q

Triglycerides- biological function (animals)

A
  • Stored in adipose tissue just under the skin
  • 1 triglyceride droplet fills the cell
  • Adipose is a good insulator
  • Adipose has a low density so it’s very buoyant for fat swimming animals.
18
Q

Triglycerides biological function (plants)

A
  • Stored as oil in seeds
  • Light-weight high energy stores for seed germination
  • Cooking oils are usually extracts from plant seeds
19
Q

Give two reasons why triglycerides are used as energy storage molecules?

A
  • They contain lots of chemical energy
  • They’re insoluble in water

Biology (54 decks)

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