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3.1 Biological Molecules > 3.1.3 Lipids > Flashcards

3.1.3 Lipids Flashcards

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Organic Chemistry 101 flashcards
1
Q

Are lipids soluble?

A
  • Insoluble in water
  • Soluble in organic solvents
    … eg) alcohols and acetone
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2
Q

two groups of lipid

A
  • Triglycerides

- Phospholipids

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3
Q

most common lipid

A

Triglycerides

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4
Q

What are triglycerides also known as

A

Fats and oils

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5
Q

3 other lipids

A

1) Waxes
2) Steroids
3) Cholesterol

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6
Q

Difference between fats and oils?

A

1) Fats are solid at room temp (10-20 degrees C), oils are liquid at room temp

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7
Q

What are lipids made up of?

A

Carbon
hydrogen
oxygen

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8
Q

Polarity of lipids

A

Non-polar

so soluble in alcohol and acetone but insoluble in water

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9
Q

Major biological role of lipids

A

Energy store

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10
Q

Why are lipids a good energy store?

A

Stores over twice the amount of energy as carbohydrates
Lower proportion of oxygen to carbon and hydrogen than carbohydrates
so don’t react as easily

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11
Q

Roles of lipids

A

1) Energy source
- When oxidised, lipids
… Release more than twice the energy as the same mass of carbohydrate
… Release water, which releases energy

2) Waterproofing
- Plants and insects have waxy cuticles
… Conserve water
- Mammals produce an oily secretion from the sebaceous glands in the skin
… Conserve water

3) Insulation
- Fats slow conductors of body heat, so stored beneath the body surface to retain body heat (reduce conduction away from body)
- Electrical insulators in the myelin sheath around nerve cells

4) Protection
- Stored around delicate organs
… ie) Kidneys

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12
Q

Where are lipids stored?

A

Adipose tissue

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13
Q

Role of lipids stored in adipose tissue

A

Heat insulation

protection

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14
Q

Why aren’t triglycerides polymers?

A

Not made of monomers/many repeating units

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15
Q

triglyceride structure

A
  • 1 glycerol molecule

- fatty acid chains are attached via ester bonds

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16
Q

Structure of triglycerides related to their properties

A

1) Good energy source
- Due to high ratio of energy-storing carbon-hydrogen bonds to carbon atoms

2) Good storage molecules
- Low mass to energy ratio
- Much energy can be stored in a small volume

3) Their storage doesn’t affect osmosis/water potential of cells
- As non-polar

4) Source of water for organisms
- Due to high ratio of hydrogen to oxygen atoms
- When oxidised, released water
… ie) Useful for organisms in dry deserts

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17
Q

Give 2 features of a fatty acid molecule

A
  • Long chain hydrocarbons

- Contain a carboxylic group (COOH) group at one end

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18
Q

General formula of a fatty acid molecule

A

RCOOH

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19
Q

formula for a fatty acid molecule

A

CH3(CH2)nCOOH

where n is usually an even number

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20
Q

Triglycerides have a hydrophobic tail. Explain how this feature of a lipid is important for its function (2)

A

Hydrophobic tails cause lipids to clump together in cytoplasm as insoluble droplets (1)
So can be stored in cells as energy source without affecting cell’s water potential (1)

21
Q

Hydrophobic

A

‘Water hating’, a substance that repels water molecules.

22
Q

Hydrophilic

A

‘Water loving’, a substance that attracts water molecules.

23
Q

Phospholipid structure

A

one glycerol,
one phosphate containing group
two fatty acids

24
Q

Fluid mosaic model

A

…

25
Q

Why do phospholipid molecules form a bilayer

A

hydrophilic heads attract water
…point outwards towards water
Hydrophobic tails repel water
…point inwards towards each other

26
Q

How does the phospholipid bilayer control the substances passing and out of the cell?

A

forms a barrier to water-soluble substances
└e.g. sugars, amino acids and ions
water can pass througg
lipid soluble substances can pass through
└e.g. oxygen and carbon dioxide

27
Q

Ester bond

A

The bond between glycerol and a fatty acid found in triglycerides and phospholipids.

28
Q

What group are fatty acids?

A

Carboxyl groups (COOH) with hydrocarbon tail (can be saturated/unsaturated)

29
Q

What can the hydrocarbon tail of a fatty acid vary in?

A

Length

30
Q

What does the R group stand for?

A

Saturated or unsaturated fatty acid

31
Q

Saturated fatty acid

A

Fatty acid with no C=C bonds, and therefore saturated with hydrogen.

32
Q

Unsaturated fatty acid

A

Fatty acid with one C=C bond. Can accept more hydrogen therefore it is unsaturated by hydrogen.

33
Q

Polyunsaturated fatty acid

A

Fatty acid containing two or more C=C (double carbon) bonds.

34
Q

What are the main differences in properties between saturated and unsaturated fatty acids?

A

Lipids containing saturated fatty acids are usually solid at room temperature (fats)
lipids containing unsaturated fatty acids are generally liquid at room temperature (oils)

35
Q

Saturated fatty acids structure to function

A
  • Only contain single bonds between carbon atoms
    … Therefore can’t add hydrogens to the carbons
    … Which makes the molecule straight
    … Which means molecules line up and bond easily
    … Which makes saturated fatty acids a good energy store
36
Q

example of a saturated fatty acid

A

Stearic acid (CH3(CH2)16COOH

37
Q

What is one fatty acid molecule substituted for in a phospholipid?

A

Phosphate containing group

38
Q

Compare and contrast phospholipids and triglycerides

A

Phospholipids have two fatty acid tails but triglycerides have three.
Both contain glycerol and fatty acids but
phospholipids have phosphate groups in them too.

39
Q

properties of phospholipids related to structure

A 
polarity
forms lipid bilayer of cell surface membrane 
  hydrophilic heads attract water
...point outwards towards water
Hydrophobic tails repel water 
...point inwards towards each other

Combine with carbohydrates at the cell surface membrane to form glycolipids
- important in cell recognition

40
Q

test for lipids

A

emulsion test

41
Q

Emulsion test

lipids

A

add ethanol
THEN add water
shake gently

positive result- cloudy white emulsion
negative result- clear

42
Q

EQ: structure of a triglyceride

A
  • contains glycerol
  • 3 fatty acids
  • forms 3 ester bonds
43
Q

EQ: Differences between triglyceride and phospholipid

A

Phospholipid has

  • phosphate
  • 2 fatty acids
44
Q

EQ: Unsaturated fatty acid

A
  • double bonds

- between carbon atoms

45
Q

EQ: Describe how phospholipids are arranged in a plasma membrane

A
  • in a bilayer
  • with hydrophobic fatty acid lipid tails on the inside
  • and hydrophilic polar phosphate group heads to the outside
46
Q

EQ: Describe how you could use the emulsion test to show the presence of oil in a sample of fish.

A
  1. (Shake with) ethanol/alcohol;
  2. Then add (to) water;
  3. White/milky/cloudy (layer indicates oil);
47
Q

EQ: Explain why the pH decreases when the lipase is added to the milk

A

Fatty acids produced

48
Q

EQ: Suggest how the scientists may have treated the milk to remove lactose.

A

Add lactase

3.1 Biological Molecules (10 decks)

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