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biology > Biological Molecules - Lipids > Flashcards

Biological Molecules - Lipids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are lipids and what do they contain

A

lipids are macromolecules. they contain large amounts of carbon and hydrogen atoms with fewer oxygen atoms.

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2
Q

what are lipids soluble and insoluble in

A

lipids are soluble in organic solvent (e.g alcohol)
and insoluble in water

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3
Q

what are the three important groups of lipids

A

triglycerides (fats and oils)
phospholipids
cholesterol

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4
Q

give an example of lipids functioning as energy storage

A

adipose tissue of vertebrates, oil in fruits and seeds

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5
Q

give an example of the structural function of lipids

A

phospholipid bilayer of cell membrane

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6
Q

give an example of the thermal insulation function of lipids

A

to reduce heat loss e.g penguins

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7
Q

give an example of the electrical insulation function of lipids

A

myelin sheath of neurone axons

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8
Q

give an example of the cushioning/protection function of lipids

A

to protect vital organs e.g heart and kidneys

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9
Q

give an example of the waterproofing function of lipids

A

birds feathers and plant leaves

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10
Q

give an example of the buoyancy function of lipids

A

aquatic animals like whales

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11
Q

give an example of lipids functioning in hormone production

A

testosterone, oestrogen, cortisol

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12
Q

describe the structure of triglycerides

A

one molecule of glycerol attached to three fatty acids by ester bonds

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13
Q

describe the structure of glycerol

A

alcohol with three carbons and 3 OH groups

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14
Q

describe the structure of fatty acids

A

carboxyl group: COOH
hydrocarbon tail: carbon and hydrogen, varies in length and structure (2-20 carbons long)

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15
Q

give a property of fatty acids

A

hydrophobic - making them insoluble in water

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16
Q

describe saturated fatty acids

A

all of the carbon atoms form the maximum number of bonds with hydrogen atoms. there are NO double bonds between carbon atoms

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17
Q

describe unsaturated fatty acids

A

there is at least one double bond between carbon atoms. this causes the chain to kink

18
Q

describe monosaturated fatty acids

A

there is just one double bond

19
Q

describe polysaturated fatty acids

A

there are two or more double bonds

20
Q

why are polyunsaturated fats liquid at room temperature

A

the kinks caused by double bonds mean that the molecules cannot pack as closely together

21
Q

how are triglycerides formed

A

a condensation reaction occurs between the COOH group of the fatty acid and the OH group of the glycerol.
the bond formed is an ester bond

22
Q

what is the name for the reaction forming triglycerides

A

esterification

23
Q

how can triglycerides be broken down

A

the ester bonds can be broken down by hydrolysis reactions

24
Q

what is the main function of triglycerides

A

compact energy store

25
Q

why are triglycerides a good compact energy store

A

they contain a high proportion of C-H bonds and therefore release about twice as much energy per gram as carbohydrates

26
Q

why are triglycerides insoluble in water and why is this useful

A

they are non-polar. therefore, they do not affect osmosis in cells

27
Q

why are lipids useful for desert animals

A

respiration of lipids releases water

28
Q

what other functions do triglycerides have (5)

A

thermal insulation, buoyancy (less dense than water), electrical insulation, protection, storage of fat-soluble vitamins e.g A and D

29
Q

describe the structure of phospholipids

A

similar to triglycerides but a phosphate group replaces one of the fatty acids ie one molecule of glycerol attached to a phosphate group and two fatty acids

30
Q

describe the phosphate group in phospholipids

A

negatively charged polar head. hydrophilic

31
Q

describe the fatty acid chains in phospholipids

A

uncharged, non-polar tails. hydrophobic

32
Q

what are the three behaviours of phospholipids in water

A
  • form a single layer on water with their heads in the water and their tails sticking up
  • form micelles in water: tiny balls with the tails pointing in and the heads on the outside
  • bilayer can form with two rows of phospholipids: tails pointing inwards and heads outwards
33
Q

describe the main function of phospholipids

A

form a key role in cell membranes

34
Q

why are phospholipids useful in cell membranes

A

flexibility and stability: the phospholipids can move within a layer but not out of the layer
selective permeability: the non-polar tails makes the membrane a barrier to the movement of large polar molecules, but small and non-polar molecules can diffuse through

35
Q

why do organisms living in colder climates often have an increased number of unsaturated fatty acids in their phospholipid membranes

A

more kinked molecule; less uniformly packed together, ensures fluidity of membranes at lower temperatures

36
Q

describe the structure of cholesterol

A

a sterol; a lipid not made from fatty acids and glycerol
cholesterol is a small hydrophobic molecule

37
Q

what are the functions of cholesterol

A

found in cell membranes where it regulates fluidity
Vitamin D, steroid hormones e.g testosterone, and bile are manufactured from cholesterol

38
Q

how can the substances manufactured from cholesterol pass through the cell surface membranes

A

simple diffusion

39
Q

describe the method for the emulsion test for lipids

A

crush material and mix well with ethanol
decant or filter the suspension to remove any solid particles
carefully pour the ethanol solution onto some water in a clear test tube - don’t mix

40
Q

what are the positive and negative results for the emulsion test

A

positive: a milky white emulsion forms on top of the water
negative: solution remains clear

41
Q

why will the emulsion test not work for milk

A

milk will cause the solution to appear milky white regardless of whether or not there are lipids present

42
Q

how does the emulsion test for lipids work

A

lipid is dissolved in ethanol and water is mixed with lipid and ethanol solution
water is more soluble than lipids in ethanol, so water displaces lipid from ethanol, forming the suspension as lipids are insoluble in water

biology (24 decks)

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