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BIOLOGY - BIOLOGICAL MOLECULES > LIPIDS > Flashcards

LIPIDS Flashcards

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1
Q

Name 4 characteristics of lipids

A

1) Contain C,O,H
2) smaller proportion of oxygen: carbon & hydrogen than in carbohydrates
3) insoluble in water
4) soluble in organic solvents (e.g. alcohols and acetones)

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2
Q

Name 4 roles of lipids in the cell membrane

A

1) source of energy
2) waterproofing
3) insulation
4) protection

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3
Q

How much more energy do lipids provide than carbohydrates

A

more than twice

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4
Q

What do lipids release as well as energy

A

water molecule

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5
Q

When do lipids release energy and water

A

when oxidised

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6
Q

How do lipids provide waterproofing

A

they are insoluble in water

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7
Q

How do mammals provide waterproofing

A

produce oily secretion in the sebaceous glands in the skin

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8
Q

How do lipids provide insulation

A

Fats are slow conductors of heat, so when stored beneath body surface help retain body heat & act as electrical insulators in myelin sheath around nerve cells

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9
Q

Where do lipids provide protection

A

stored around delicate organs such as kidneys

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10
Q

Name 2 kinds of lpid

A

triglyceride, phospholipid

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11
Q

What molecules are triglycerides made of

A

3 fatty acids, 1 glycerol

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12
Q

What bond are the molecules of triglycerides joined by

A

ester bond

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13
Q

What process is the molecules of triglycerides made by

A

condensation reaction

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14
Q

What are fatty acid tails made of

A

hydrocarbons

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15
Q

What characteristic to fatty acid tails hold

A

they are hydrophobic

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16
Q

What do the hydrophobic tails mean for lipids

A

they are insoluble in water

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17
Q

What characteristic varies within triglycerides

A

the ‘R’ group hydrocarbon tail

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18
Q

What is the basic structure of a fatty acid

A

Carbon, linked with:
double bond to oxygen
single bond to OH
single bond to variable ‘R’ group hydrocarbon tail

19
Q

How many kinds of fatty acid are there

A

3

20
Q

What are the different kinds of fatty acids

A

1) saturated
2) mono-unsaturated (unsaturated)
3) polyunsaturated (unsaturated)

21
Q

What are the differences between the fatty acids

A

the hydrocarbon tails

22
Q

What is the characteristic of a saturated fatty acid

A

no double bonds between carbon atoms

23
Q

What is the characteristic of a mono-unsaturated fatty acid

A

single double bond between carbon atoms

24
Q

What is the characteristic of a polyunsaturated fatty acid

A

more than one double bond between carbon atoms

25
Q

What is triglycerides main function

A

energy storage molecules

26
Q

What structures of triglycerides make it useful for energy storage

A

1) long hydrocarbon tails of fatty acids contain lots of chemical energy
2) low mass to energy ratio
3) large, non-polar molecules

27
Q

Why do the hydrocarbon tails containing chemical energy make triglycerides good for energy storage

A

lots of energy released when broken down

28
Q

Why does the low mass: energy ratio make them good for storage

A

lots of energy can be stored in a small volume

29
Q

Why does the triglycerides being large, non-polar molecules mean that they are good for energy storage

A

do not effect water potential, so water does not enter by osmosis

30
Q

What are the lipids found in cell membranes

A

phospholipids

31
Q

What is the structure of phospholipids

A

3 fatty acids, 1 glycerol, 1 phosphate group

32
Q

How are phospholipids different to triglycerides

A

one fatty acid replaced by phosphate group

33
Q

Which part of the phospholipid is hydrophilic

A

head (phosphate group) - attracted to water, repels fat

34
Q

Which part of the phospholipid is hydrophobic

A

tail (fatty acid) - repels water, attracts fat

35
Q

Are phospholipids polar

A

yes

36
Q

Name 3 structures of phospholipids that relate to their function in cell membranes

A

1) polar

2) centre is hydrophobic

37
Q

Why does phospholipids being polar help their function

A

They form a bilayer within cell surface membranes, so a barrier is formed between inside and outside of cell

38
Q

Why does phospholipids having a hydrophobic centre help their function

A

It means water-soluble substances can’t easily pass through it - so it acts as a barrier

39
Q

What is the test for lipids

A

emulsion test

40
Q

How many steps are there in the emulsion test

A

5

41
Q

What are the steps in the emulsion test

A

1) Take a completely dry and grease-free test tube
2) Add 2cm3 of the food sample to the test tube
3) Add 5cm3 of ethanol to this
4) Shake the tube thoroughly to dissolve any lipid in the sample
5) Add 5cm3 of water and shake gently

42
Q

What indicates the presence of a lipid in the emulsion test

A

A cloudy-white precipitate (more cloudy = more lipid)

43
Q

What causes the cloudy precipitate to form in the emulsion test

A

The lipid in the sample being finely dispersed in the water, and light passing through being refracted as it passes between oil droplets and water droplets (makes it cloudy)

BIOLOGY - BIOLOGICAL MOLECULES (12 decks)

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