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biology module 2 > biological molecules - water, carbohydrates and lipids > Flashcards

biological molecules - water, carbohydrates and lipids Flashcards

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1
Q

polar definition (in regard to molecules)

A

molecules with regions of negativity and positivity

usually due to asymmetry, the distribution of electrons in a covalent bond or charge of particles

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2
Q

why can water form hydrogen bonds

A

water is a polar molecule
the positive and negative regions of the molecule attract each other and H atoms can interact with the lone pairs on O atoms to form hydrogen bonds

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3
Q

why is water a good solvent + reaction medium

A

due to water’s polarity, it can attract positive/negative regions of other molecules
these forces of attraction hold the molecules close together until the solute dissolves
it is also liquid at room temperature
this makes it a good reaction medium for ions or dissolved substances

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4
Q

why is water cohesive

A

due to water’s polarity, it can form hydrogen bonds meaning there are strong intermolecular forces of attraction between molecules that allow them to stick together

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5
Q

why is water adhesive

A

due to the polarity of water, the molecules are also attracted to other surfaces

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6
Q

why does water have high surface tension

A

water is more cohesive to itself than it is adhesive to air

this allows organisms to live on the surface of water e.g. pond skaters

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7
Q

why is water able to travel up plants

A

water is more cohesive to itself than it is adhesive to other surfaces e.g. the xylem

as water evaporates out of stomata, water molecules are pulled up through the xylem as they stick together - this is called capillary action, as it moves in opposition to gravity

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8
Q

why does water have an unusually high specific heat capacity/specific latent heat

A

hydrogen bonds between water molecules can absorb a lot of energy, therefore more energy needed to change temperature or state

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9
Q

why is water’s high specific heat capacity important for life

A

since a very large amount of energy is needed to change the temperature of water by 1 degree, it is a very stable habitat for living organisms as there will be less temperature fluctuations

this is good for living organisms who cannot thermoregulate, such as fish

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10
Q

why is water less dense as a solid/ice

A

hydrogen bonds between water molecules hold the molecules apart in open lattice structure when solid, so ice is less dense than water

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11
Q

why is it important for living organisms that ice is less dense than water - 2 reasons

A
  • due to the open lattice structure of ice, it can act as a habitat for organisms in winter
  • due to low density of ice, it is able to float in water, therefore it can act as insulation in ponds and other bodies of water in winter, protecting them against the extreme cold
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12
Q

what is a carbohydrate

A

a molecule made of just C, H and O, usually in the ratio CH2O

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13
Q

what is a single unit of sugar

A

a monosaccharide

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14
Q

2 monosaccharides form …

A

a disaccharide

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15
Q

glucose is composed of 6 carbons, making it a…

A

hexose sugar

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16
Q

what are the 2 types of glucose molecule and the differences between them

A

alpha glucose
- on carbon 1 H is above OH
(the OH groups on alpha do not alternate)

beta glucose
- on carbon 1 OH is above H
(so the OH groups on beta glucose alternate up-down-up-down)

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17
Q

what bonds do carbohydrates form

A

glycosidic bonds
C-O-C
formed in condensation reactions
broken in hydrolysis reactions

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18
Q

a-glucose + a-glucose =

A

maltose

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19
Q

a-glucose + fructose =

A

sucrose

used to transport sugars in plants

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20
Q

a-glucose + galactose =

A

lactose

found in mammal milk

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21
Q

deoxyribose/ribose are composed of 5 carbons, making them…

A

pentose sugars

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22
Q

what is a polysaccharide

A

a complex carbohydrate molecule, made of more than 2 monosaccharide sugars bonded together

23
Q

4 examples of polysaccharides

A
  • starch
  • glycogen
  • cellulose
  • callose
24
Q

what is the structure of starch

A

made of amylose and amylopectin - both made of a-glucose

amylose is unbranched and formed of 1-4 glycosidic bonds, it twists into a helix shape held together by hydrogen bonds

amylopectin is branched and formed of both 1-4 and 1-6 (1 in 25) glycosidic bonds

25
Q

what is the function of starch

A

storage of carbohydrates in plants

26
Q

what are the properties of starch + how do these help its function

A
  • insoluble - doesn’t dissolve in cytoplasm or affect cell water potential
  • compact - good storage molecule
  • branching - allows for quick conversion into monomers
27
Q

what is the structure of glycogen

A

made up of short branched a-glucose chains held together by 1-4 and 1-6 glycosidic bonds

28
Q

what is the function of glycogen

A

storage of glucose in animals

29
Q

what are the properties of glycogen + how do these help its function

A
  • lots of branching - this means there are lots of free ends, allowing for the quick conversion into glucose monomers - very important in animals due to high levels of activity, compared to plants
  • insoluble - doesn’t dissolve in aqueous cytoplasm or affect water potential of cell
30
Q

what is the structure of cellulose

A

linear straight chains made of b-glucose, held together by 1-4 glycosidic bonds (every other monomer flips upside down)

31
Q

what is the function of cellulose

A

forms plant cell wall

32
Q

what are the properties of cellulose + how do these help its function

A
  • polysaccharide chains are able to join together via hydrogen bonds - forms microfibrils - these join to form fibres - these are very tough to break down and make it very strong - this is important as it its plants only support
  • insoluble - ensures it doesn’t dissolve in aqueous plant cell cytoplasm
33
Q

what is the structure of callose

A

made of b-glucose held together by 1-3 and 1-6 glycosidic bons which form a helical structure

34
Q

5 common functions of carbohydrates

A
  • energy stores e.g. starch and glycogen
  • intermediates/substrates in reactions
  • structure e.g. cellolse cell walls
  • transport in plants e.g. sucrose
  • receptors and cell markers on cell membrane e.g. glycoproteins/glycolipids
35
Q

what are lipids

A

complex non polar macromolecules

36
Q

what is the difference between saturated and unsaturated lipids

A

saturated - no C=C bonds, unbranched so solid at room temperature, commonly referred to as fats

unsaturated - has C=C bonds, making them branched/with kinks, so liquid at room temperature as cannot pack closely together, commonly referred to as oils

37
Q

what are 3 types of lipid

A

triglycerides
phospholipids
sterols

38
Q

what are triglycerides made of

A

1 glycerol molecule and 3 fatty acids

39
Q

what bonds do lipids form

A

ester bonds
C-O-C=O
formed in condensation reactions
broken in hydrolysis reactions

40
Q

what are 5 functions of triglycerides

A
  • energy source
  • metabolic water source e.g. in desert animals like camels
  • adipose tissue
  • organ protection
  • insulation e.g. blubber in killer whales
41
Q

how do triglycerides compare to carbohydrates in terms of energy

A

triglycerides release more energy

42
Q

what is the structure of a phospholipid

A

composed of 1 glycerol molecule, 2 fatty acids and a phosphate PO4 2- group

fatty acid tails are hydrophobic, phosphate head is hydrophilic

the phosphate group is on the opposite side of the glycerol molecule to the fatty acids, as it is polar due to negative charge, so it spins to the other side to get away from non-polar fatty acids

43
Q

what is the main function of phospholipids

A
  • formation of biological membranes - due to dual hydrophobic and hydrophilic properties which allow the formation of bilayers
44
Q

what is a sterol

A

a steroid alcohol - complex alcohol molecules

these have dual hydrophobic/hydrophilic properties

45
Q

1 example of a sterol

A

cholesterol

46
Q

what are 4 functions of sterols

A
  • used as steroid hormones e.g. oestrogen, testosterone
  • in biological membranes in increase fluidity
  • used to manufacture bile
  • used to manufacture vitamin d
47
Q

how is cholesterol transported and why

A

as a lipoprotein

this allows lipids to dissolve in blood

48
Q

where is cholesterol produced

A

liver and intestines

49
Q

what are HDLs

A

high density lipids

50
Q

what are LDLs

A

low density lipids

51
Q

what is the difference between HDLs and LDLs

A

HDLs are good
- they regulate fluidity of the membrane
- they are soluble in water therefore can be transported in blood

LDLs are bad
- they lead to arterial blocks as they build up in walls

52
Q

how does cholesterol sit in a membrane

A

the hydroxyl group is in contact with the phosphate heads

53
Q

how does the presence of cholesterol affect membrane fluidity at different temperatures

A

increases fluidity as it stops phospholipids from packing too closely together and crystallising - cold temps

decreases fluidity as it restricts the motion of membrane molecules - warm temps

54
Q

what 2 molecules can combine with cholesterol to form LDLs

A
  • saturated fatty acids
  • triglycerides

biology module 2 (10 decks)

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