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2.1.2 Biological Molecules > Lipids > Flashcards

Lipids Flashcards

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Organic Chemistry 101 flashcards
1
Q

What elements are lipids made of?

A

Carbon, hydrogen and a little oxygen

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2
Q

Why are lipids hydrophobic?

A

Because they have little oxygen, meaning they have less polar bonds, therefore making them hydrophobic

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3
Q

Do lipids have more or less hydrogen in them than carbohydrates?

A

More

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4
Q

Are lipids soluble or insoluble in water?

A

Insoluble

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5
Q

What are lipids soluble in?

A
  • Ethanol
  • Organic solvents
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6
Q

What are the two types of lipid?

A
  • Fats -> solid at RT (animals produce mostly fats)
  • Oils -> liquid at RT (plants produce mostly oils)
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7
Q

What are 7 functions of lipids?

A
  • Dense energy source
  • Insulation
  • Protection
  • Waterproofing
  • Metabolic water
  • Buoyancy
  • Cell membranes
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8
Q

Why are lipids good for storage?

A
  • Insoluble -> they do not disperse
  • They don’t affect water potential
  • Energy rich (produce 2x as much energy as carbohydrates)
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9
Q

How are lipids used for insulation?

A
  • Fats are slow conductors of heat so are stored underneath the skin of endothermic to maintain a constant body temperature
  • Very important for acquatic organisms
  • Also provides electrical insulation around nerves
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10
Q

How are lipids used for protection?

A

Fat is stored around delicate organs like the kidneys

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11
Q

How are lipids used for waterproofing?

A
  • Water conservation is important to all terrestrial organisms
  • Plants and insects have a
    waxy cuticle
  • Mammals secrete an oily substance from sebaceous glands. They repel water so prevent water loss.
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12
Q

How are lipids used as a water source?

A

Breakdown of triglycerides can provide metabolic water which desert
animals can use

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13
Q

How are lipids used for buoyancy?

A

Lipids are less dense than water so insulated aquatic animals are buoyant (float) -> aids breathing

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14
Q

How are lipids used in cell membranes?

A

Phospholipids are a component of cell surface membranes. They add flexibility and act as a barrier in the cell.

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15
Q

What are the types of lipid?

A
  • Simple -> triglycerides (fats, oils), waxes, steroids (hormones that derive from cholesterol)
  • Complex -> phospholipids (similar to triglycerides and a component of cell surface membranes), glycolipids
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16
Q

What are triglycerides?

A
  • Made of 3 fatty acids and a glycerol molecule
  • Fatty acids contain a carboxyl group (COOH), hence acid
  • Uncharged molecule, so insoluble jn water and hydrophobic
17
Q

How are triglycerides formed?

A
  • In a condensation reaction, the COOH group of the fatty acids react with the OH group of the glycerol molecule, which forms an ester bond
  • Water is also formed
  • Covalent linkage, so very strong
18
Q

What is the formula of glycerol?

A

C₃H₅(OH)₃

19
Q

What do the properties of triglycerides depend on?

A
  • The fatty acids
  • Because glycerol only has one form
20
Q

What is the difference between saturated and unsaturated fats?

A
  • Saturated -> they don’t have a C=C double bond
  • Unsaturated -> that have one or more C=C double bonds
21
Q

What do mono and polyunsaturated fats mean?

A
  • monounsaturated -> one C=C double bond
  • polyunsaturated -> multiple C=C double bonds
22
Q

What do the C=C double bonds do to the fatty acids?

A
  • Makes the fatty acids bend
  • So they can’t pack as closely and the triglyceride is more liquid (oil)
  • Double bonds reduce the melting point
23
Q

What are waxes?

A
  • Lipid molecules where the hydrocarbon chain is linked to an alcohol and not glycerol
  • (not digested by animals)
24
Q

What is the main use of waxes?

A
  • Waterproof covering in living organisms -> e.g outer cuticle on leaves
25
Q

Why are steroids a type of lipid?

A
  • So that they can pass directly through phospholipid bilateral (including nuclear envelope)
  • So can bind to target receptor in nucleus and can act directly on DNA
26
Q

What is the structure of cholesterol and what does this structure allow them to do?

A
  • Made of 4 carbon rings joined together
  • Small narrow structure allow them to sit between phospholipids in membranes
27
Q

Where is most cholesterol made?

A

Most is made in the liver (also comes from diet)

28
Q

What two steroid hormones are made from cholesterol?

A
  • Oestrogen
  • Testosterone
29
Q

What vitamin is made from cholesterol?

A

Vitamin D (important in calcium absorption, deficiency= rickets)

30
Q

What does cholesterol do in plasma membranes?

A
  • Regulates membrane fluidity
31
Q

How do you test for lipids?

A
  • Add ethanol and shake well
  • Cloudy white -> positive result
32
Q

Why does the ethanol test work?

A
  • Lipids are insoluble in water and soluble in ethanol (an alcohol)
  • After lipids have been dissolved in ethanol and then added toH2O,they will form tiny dispersed droplets in the water (emulsion)
  • Droplets scatter light as it passes through the water so it appears white and cloudy
33
Q

Give three differences between saturated and unsaturated fats?

A
  • Unsaturated fats have at least one C=C double bond whereas saturated fats have on single bonds.
  • Unsaturated fats have a lower melting point than saturated
  • Unsaturated -> usually from plants whereas saturated -> usually from animals

2.1.2 Biological Molecules (5 decks)

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