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*biology > lipids (biological molecules) > Flashcards

lipids (biological molecules) Flashcards

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1
Q

elements lipids contain

A
  • carbon
  • hydrogen
  • oxygen
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2
Q

the proportion of oxygen, to carbon and hydrogen in lipids is smaller

A

than in carbohydrates

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3
Q

lipids are insoluble in

A

water

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4
Q

lipids are soluble in

A

organic solvents such as alcohols and acetone

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5
Q

the main groups of lipids are (2)

A
  • triglycerides (fats and oils)
  • phospholipids
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6
Q

structure of triglyceride diagram

A
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7
Q

structure of fatty acid diagram

A
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8
Q

roles of lipids

A
  • phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them
  • source of energy, when oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water
  • waterproofing, lipids are insoluble in water and therefore useful as a waterproofing, both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin
  • insulation, fats are slow conductors of heat and when stored beneath the body surface help to retain body heat, they also act as electrical insulators in the myelin sheath around nerve cells
  • protection, fat is often stored around delicate organs, such as the kidney
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9
Q

what do lipids do in cell membranes

A

phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them

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10
Q

how are lipids a souce of energy

A

when oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water

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11
Q

how are lipids good at waterproofing

A

lipids are insoluble in water and therefore useful as a waterproofing, both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin

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12
Q

how are lipids good at insulation

A

fats are slow conductors of heat and when stored beneath the body surface help to retain body heat, they also act as electrical insulators in the myelin sheath around nerve cells

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13
Q

how are lipids good for protection

A

fat is often stored around delicate organs, such as the kidney

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14
Q

why are triglycerides so called

A

they have three (tri) fatty acids combined with glycerol (glyceride)

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15
Q

each fatty acid in a triglyceride forms an

A

ester bond with glycerol in a condensation reaction

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16
Q

hydrolysis of a triglyceride produces

A

glycerol and three fatty acids

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17
Q

formation of a triglyceride diagram

A
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18
Q

which molecule in all triglycerides is the same

A

glycerol

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19
Q

the differences in the properties of different fats and oils come from variations in the

A

fatty acids

20
Q

there are over 70 different fatty acids, and all have a

A

carboxyl (-COOH) group with a hydrocarbon chain attached

21
Q

what type of hydrocarbon chain has no carbon-carbon double bonds

A

saturated (all the carbon atoms are linked to the maximum possible number of hydrogen atoms, they are saturated with hydrogen atoms)

22
Q

saturated hydrocarbon chains have no

A

carbon-carbon double bonds

23
Q

if there is a single double bond in a hydrocarbon chain it is

A

mono-unsaturated

24
Q

a hydrocarbon chain is mono-unsaturated if

A

there is a single double bond

25
Q

if more than one double bond is present in a hydrocarbon chain it is

A

polyunsaturated

26
Q

a hydrocarbon chain is polyunsaturated if

A

more than one double bond is present

27
Q

how is the structure of triglycerides related to their properties

A
  • have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy
  • have low mass to energy ratio, making them good storage molecules because much energy can be stored in a small volume, this is especially beneficial to animals as it reduces the mass they have to carry as they move around
  • being large, non-polar molecules, triglycerides are insoluble in water, their storage does not affect osmosis in cells or the water potential of them
  • as they have a high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised and therefore provide an important source of water, especially for organisms living in dry deserts
28
Q

triglycerides have a high ratio of

A

energy-storing carbon-hydrogen bonds to carbon atoms and are therefore an excellent source of energy

29
Q

tryglicerides have a low

A

mass to energy ratio, making them good storage molecules because much energy can be stored in a small volume, this is especially beneficial to animals as it reduces the mass they have to carry as they move around

30
Q

what type of molecule is a triglyceride

A

large non polar molecule

31
Q

why is a trygliceride being a large non polar molecule effective

A

insoluble in water, their storage does not affect osmosis in cells or the water potential of them

32
Q

why is triglycerides having a high ratio of hydrogen to oxygen atoms effective

A

triglycerides release water when oxidised and therefore provide an important source of water, especially for organisms living in dry deserts

33
Q

difference between phospholipids and lipids

A
  • one of the fatty acid molecules is replaced by a phosphate molecule
  • fatty acid molecules repel water (hydrophobic)
  • phosphate molecules attract water (hydrophilic)
  • phospholipid is a polar lipid and triglyceride is a non polar lipid
34
Q

fatty acid molecules repel

A

water (hydrophobic)

35
Q

phosphate molecules attract

A

water (hydrophilic)

36
Q

a phospholipid is made up of two parts:

A
  • hydrophilic ‘head’, which interacts with water (is attracted to it) but not with fat
  • hydrophobic ‘tail’, which orients itself away from water but mixes readily with fat
37
Q

what type of molecule is a phospholipid

A

polar

38
Q

molecules that have two ends (poles) that behave differently in this way are said to be

A

polar

39
Q

molecules that are said to be polar means

A

that when these polar phospholipid molecules are placed in water they position themselves so that the hydrophilic heads are as close to the water as possible and the hydrophobic tails are as far away from the water as possible

40
Q

how is the structure of phospholipids related to their properties

A
  • are polar molecules, having a hydrophilic phosphate head and a hydrophobic tail of two fatty acids, this means that in an aqueous environment, phospholipid molecules form a bilayer within cell-surface membranes, as a result, a hydrophobic barrier is formed between the inside and outside of a cell
  • the hydrophilic phosphate ‘heads’ of phospholipid molecules help to hold at the surface of the cell-surface membrane
  • the phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane, these glycolipids are important in cell recognition
41
Q

how is phospholipids being polar molecules effective in aqueous environments

A
  • form a bilayer within cell-surface membranes
  • as a result, a hydrophobic barrier is formed between the inside and outside of a cell
42
Q

the phospholipid structure allows them to form

A
  • glycolipids by combining with carbohydrates within the cell-surface membrane
  • these glycolipids are important in cell recognition
43
Q

glycolipids are important in

A

cell recognition

44
Q

structure of a phospholipid diagram

A
45
Q

emulsion test for lipids method

A
  • take a completely dry and grease-free test tube
  • to 2 cm3 of the sample being tested, add 5 cm3 of ethanol
  • shake the tube thoroughly to dissolve any lipid in the sample
  • add 5 cm3 of water and shake gently
  • a milky-white emulsion indicates the presence of a lipid
  • as a control, repeat the procedures using water instead of the sample; the final solution should remain clear
46
Q

in lipids the proportion of oxygen to carbon and hydrogen is smaller than in

A

carbohydrates

*biology (6 decks)

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