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biological molecules 2.1.2 Flashcards

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1
Q

what is the structure of water molecule ?

A

one oxygen is bonded to two hydrogen by covalent bonds.

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2
Q

what type of molecule is water ?

A

a polar molecule (dipole) because of the separation of charge

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3
Q

why is water a polar molecule ?

A

hydrogens shared electrons are pulled closer to the oxygen atom leaving the hydrogen with a partially positive charge and the oxygen with a partially negative charge

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4
Q

describe a diagram showing how water bonds

A

the dotted line between the oxygen and hydrogen shows the hydrogen bond

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5
Q

how do you show partial charges of a atom

A

the delta sign + or -

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6
Q

why does water have a high specific heat capacity ?

A

a large amount of energy is required to increase the temperature of water because the hydrogen bonds can absorb lots of energy

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7
Q

what is the importance of water having a high specific heat capacity ?

A

it provides a stable environment for aquatic organisms as large temperature fluctuations do not occur

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8
Q

why does water have high latent heat of vaporisation ?

A

lots of energy is required to break hydrogen bonds between water molecules so that it becomes gaseous

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9
Q

what is the importance of water having a high latent heat of vaporisation ?

A

it is an excellent coolant:
- mammals sweat carrying away heat
- plants transpire carrying away heat
- temperature buffer for chemical reactions
- proper function of enzymes

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10
Q

how is water cohesive ?

A

cohesion is the attraction between water molecules, allowing them to flow and move as one mass

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11
Q

what is the importance/role of water being cohesive ?

A

allows transport through the xylem and phloem or the blood.
surface tension which provides a habitat for animals

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12
Q

how is water adhesive ?

A

its the attraction between water molecules and other polar substances due to hydrogen bonding

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13
Q

what is he importance/role of water being adhesive and cohesive ?

A

allows for a transpiration stream as all the water can be drawn up by capillary action along the xylem.

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14
Q

why does water have low density when it is solid ?

A

when water changes from liquid to solid each molecule forms 4 bonds creating a lattice. this makes the ice less dense as there is more space between the moclecules

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15
Q

what is the role/importance of water being a low density solid ?

A

ice floats which forms a insulating layer making a stable environment for aquatic organism because the rate at which heat is lost is reduced.
it also severs as habitat

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16
Q

why is water a good solvent ?

A

water is polar therefore the slightly positive part will attract negative ions, and the slightly negative part will attract positive ions. the water molecules surround each ion in a hydration shield bonded with ionic bonds.

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17
Q

what is the importance of water being a good solvent ?

A

it allows water to transport molecules and ions as they dissolve in it. eg. glucose in the blood
and most chemical reactions take place in a solution eg. cytoplasm

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18
Q

how can you tell if a substance will dissolve in water ?

A

it will have the -OH group or -SH group wich makes them polar so they will attract the water

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18
Q

explain how sodium chloride dissolves in water ?

A

the ions split up and the -Cl ion will bond by ionic bonds to the hydrogen as it is partially +, the hydrogen surround the chloride in a shell ( dissolved ). the +Na ion will bond to the partially negative oxygen the same way

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18
Q

why is it useful to organisms that water is a liquid at room temperature ?

A

effective transport medium
habitat
medium for chemical reactions

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19
Q

what are the role of carbohydrates ?

A

energy source eg. glucose
energy storage eg. starch
structural eg. cellulose

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20
Q

what elements does carbohydrate contain and the ratio of it ?

A

carbon, hydrogen, oxygen in the ratio 1:2:1

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21
Q

what is a monosaccharide, disaccharide and polysaccharide ?

A

a simple sugar unit, two monosaccharides linked and many monosaccharides link together

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22
Q

what is a monomer ?

A

small, basic molecular units eg. monosaccharides

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23
Q

what are polymers ?

A

large, complex molecules composed of long chains of monomers joined together eg. cellulose, starch and proteins

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24
Q

what is a hexose monosaccharide ?

A

6 carbon atoms

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25
Q

what is the chemical formula of glucose ?

A

C6H12O6

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26
Q

what are the two forms of glucose ?

A

alpha (a) and beta (b)

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27
Q

how do you label the carbon atoms in a ring of glucose ?

A

numbered clockwise with the beginning the carbon to the right of the oxygen atom

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28
Q

describe the qualities of two other sugars (not glucose)

A

fructose = very sweet (sweetest) , soluble (most soluble) found in fruits and nectar
galactose = not as soluble, important for production of glycolipids and glycoproteins

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29
Q

what are two pentose monosaccharides ?

A

they contain 5 carbon atoms
ribose - has oxygen on the second carbon
deoxyribose - no oxygen in the second carbon

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30
Q

how do two alpha glucose molecules react ?

A

the two hydroxyl ( OH) groups react in a condensation reaction to form maltose and water.

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31
Q

what type of bond do two alpha glucose molecules form ?

A

a1-4 glycosidic bond as the 1st carbon and the 4th carbon bond with the shared oxygen, this is called a disaccharide .

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32
Q

what is the reverse of a condensation reaction involving alpha glucose molecules ?

A

hydrolysis = splitting the molecule

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33
Q

what molecules bond to form alpha lactose and what is the type of bond ?

A

alpha glucose and galactose form a beta 1-4 glycosidic bond. it is recognisable because the bond is directed upwards

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34
Q

what molecules bond to form beta lactose and what is the type of bond ?

A

beta glucose and galactose form a beta 1-4 glycosidic bond

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35
Q

what molecules bond to form sucrose and what is the type of bond ?

A

alpha glucose and fructose bond to for alpha1-beta2 glycosidic bond

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36
Q

what are the properties of a energy storage molecule ?

A

compact- energy dense
insoluble - water potential not effected
easy to add glucose too - condensation reaction
easy to remove glucose from = hydrolysis
metabolically inactive - wont react with surroundings

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37
Q

where is starch found and what is its function ?

A

plants produce starch, it is an energy storage molecule

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38
Q

what is starch made from ?

A

repeating units of alpha glucose

39
Q

describe the structure of amylose ?

A

long unbranched chain
a1-4 glycosidic bonds
30% of starch
coils into compact helix held in place by hydrogen bonds

40
Q

why is amylose insoluble ?

A

the OH groups are folded inside the coils so that they cant interact with other water molecules

41
Q

what is the structure of amylopectin ?

A

a1-4 glycosidic bonds in a helix shape
70 % of starch
every 25 glucose units there is a a1-6 glycosidic bond forms by condensation creating a branch

42
Q

describe the structure of glycogen ?

A

made of glycose
branch points due to a1-6 glycosidic bonds every 10th glycogen

43
Q

why is glycogen more branched than amylopectin (starch) - refer to energy needs of animals and plants?

A

animals use glycogen because they need more energy provided as they are mobile. the glycogen is able to provide more energy as more branches means more free ends where hydrolysis can occur meaning stored glycose can be releases quicker.
glycogen is also tightly packed so easier
this is in comparison to plants witch are immobile so need less energy, therefore they use amylopectin

44
Q

why is it important that glucose is stored instead of being free in the blood or phloem ?

A

glucose is too soluble meaning it can dissolve in blood. too much will lower the water potential of the blood causing water to move out of cells by osmosis. hence why its stored in a insoluble form

45
Q

why is branching and compaction important ?

A

there are many ends for hydrolysis and condensation reactions this is essential so that many glucose units as possible ae stored

46
Q

what is the structure of cellulose ?

A

long unbranched chains of beta glucose
hydrogen bonds stop them from spiralling
the long chains bind together to make microfibrils, which bundle to form macrofibrils imbedded in pectin to form cell walls
they criss cross in all directions for extra tensile strength and insoluble

47
Q

how do the beta glucose molecules bond in cellulose ?

A

the hydroxyl groups on the c1 and c4are two far apart so the alternate b glucose is inverted180 degrees so that they can be close enough to form a1-4 glycosidic bond

48
Q

what is the function of cellulose ?

A

form cell walls - high tensile strength
prevents cell bursting when turgid
cell wall is fully permeable due to space between microfibrils
insoluble and inert
helps to make the bulk of food (fibre) so humans can digest it

49
Q

what are the functions of lipids ?

A

energy source - used in respiration (twice energy per gram then carbs)
water source - respired to release water
energy store - insoluble in water so can be stored without effecting the water potential
thermal insulation - eg .whale blubber, hibernating animals
stores fat soluble vitamins- adipose tissue store ADEK
buoyancy - fat is less dense than water
cushioning - visceral fat protects organs
membrane function - creation of hydroponic barriers
hormone production - lipids used so they can enter cell membrane
electrical insulation - for impulse transmission
waterproofing - eg. bird feathers and cuticle on leaves

50
Q

what elements make up lipids and in what ratio ?

A

carbon, hydrogen and oxygen in ratio 1:2:<1

51
Q

what are macromolecules ?

A

complex molecules with a relatively large molecular mass, so they don’t form polymers as they are not monomers eg . lipids

52
Q

what are properties of lipids ?

A

macromolecules
not polar
insoluble in water
dissolvable in alcohol
fats are solid at room temp , oils are liquid

53
Q

what is a triglyceride made from ?

A

one glycerol (acts as the backbone) and 3 fatty acids ( have a carboxylic acid group with a hydrogen chain )

54
Q

how do triglycerides form ?

A

the glycerol and the fatty acids both have OH groups
they interact to form 3 ester bonds and release 3 water molecules

55
Q

what are saturated and unsaturated fats ?

A

saturated fats produce straight chains because there are no carbon double bond
unsaturated fats produce chains that have a bend or kink because they have a carbon double bond

56
Q

what are the properties of saturated and unsaturated fats ?

A

saturated fats have straight chains so they make denser fats as the chains can pack together eg. solids like butter
unsaturated fats have bends in there chains so they can pack closely this makes less dense fats eg. liquids like oils

57
Q

why are triglycerides good energy storage molecules ?

A

insoluble
release twice as much energy as carbohydrates per gram
form micelles which are insoluble droplets

58
Q

what are phospholipids ?

A

modified triglycerides
they contain phosphorus , carbon, hydrogen, oxygen
2 fatty acids , 1 glycerol , 1 phosphorus group

59
Q

define amphipathic

A

a molecule that has both hydrophobic and hydrophilic portions

60
Q

describe the formation a phospholipid bilayer

A

the hydrophilic heads arrange to aim the hydrophobic tails together creating a double layer, the centre in between is hydrophobic which means soluble substances cant pass through easy. this creates a cell membrane

61
Q

what are the properties of a phospholipid bilayer ?

A

the phospholipids are free to move around in their layer , making the membrane fluids and flexible. its selectively permeable- small molecules (water) and non polar molecules (oxygen,co2) can pass through

62
Q

what are sterols ?

A

a type of lipid found in cells
complex ring structure with a hydroxyl group
amphipathic molecules (due to the OH group being hydrophilic and the rest hydrophobic )

63
Q

what does cholesterol do to cell membranes ?

A

cholesterol is flattered in shape and because its a sterol it is amphipathic , the soluble part interacts with the phospholipid tails in the membrane, and the insoluble part interacts with the heads. they fit in-between the phospholipids which makes them pack tighter making the membrane rigid and less fluid. cholesterol can also be removed to make the membrane more fluid

64
Q

what is the test for lipids ?

A

add ethanol to test tube with the sample in and dissolve it. then add water and if a cloudy layer forms then the sample is lipid

65
Q

what is the basic structure of an amino acid ?

A

amino group ( NH2)
central carbon and a hydrogen off that, and a R group
carboxyl group ( COOH)

66
Q

what elements are proteins made from ?

A

C ,H, O, Nitrogen, sulfur

67
Q

what is the function of proteins ?

A

basic growth and repair
structural (tissues)
catalytic ( enzymes )
signaling ( hormones )
immunological ( antibodies )

68
Q

what is the R group in amino acids ?

A

it is the only thing that differs between amino acids
glycine is the smallest amino acid and its R group is just a hydrogen
can be complex ring structures, polar , non polar, hydrophilic ect.
in cystine a disulfide bond forms between the R groups forming the strongest covalent bond

69
Q

how many amino acids are there and why are they needed ?

A

20 different
5 are non essential
9 are essential and must be obtained by the food we eat
6 are conditionally essential and are only required when growing up

70
Q

how can amino acids be used as pH buffers ?

A

when placed in an acidic environment the amino group can gain H+ ions to become NH3+
when placed in an alkaline environment the carboxyl group can lose H+ ions to become COO-

this means it is a substance that resists change in pH
it is also an amphoteric molecule as it has both acidic and alkaline properties

71
Q

what are polypeptides ?

A

a chain of amino acids which fold highly into a protein specific shape

72
Q

what are the 4 levels of proteins structure ?

A

primary - sequence of amino acids
secondary - alpha helices and beta sheets
tertiary - r groups interacting with different bonds
quaternary - subunits join together

73
Q

describe the structure of alpha helices and beta sheets ?

A

hydrogen bond form between the -NH groups and -CO groups of the amino acids (not the R groups) these bonds cause the pulling of chains into a coil shape or the zig zag sheets. the bond are weak but there are many of them holding the structures together

74
Q

describe the structure of tertiary proteins ?

A

the R groups are pulled close together so they can interact and cause folding. they bond with:
ionic bonds - attractions between - R groups and + R groups
disulphide bonds - two cystine amino acids that bond between two sulphur atoms
hydrophobic/hydrophilic interactions - the proteins are assembled within the aqueous environment of the cell and this cause the hydrophobic R groups to orient inside of the protein so they are shielded form the water, the hydrophilic go to the outside and interact with water
hydrogen bonds - weak bonds between the partially + or - R groups

75
Q

describe the quaternary structure of proteins ?

A

several subunits come together and form bonds

76
Q

what is haemoglobin ?

A

haemoglobin is a globular protein that carries oxygen in red blood cell
each of its 4 subunit contains a haem prosthetic group holds an iron ion
the iron ion binds reversibly with oxygen and transports oxygen around the body. when the oxygen combines with the iron the shape of the pigment changes and the protein is called oxyhaemoglobin

77
Q

what is a conjugated protein ?

A

a protein that has a non protein group attached , the non protein part is called a prosthetic group
eg. haemoglobin

78
Q

how are peptides broken down ?

A

hydrolysis reaction , a molecule of water and enzyme protease is required. the groups reformed are amino and carboxyl group

79
Q

what is a fibrous protein ?

A

long insoluble molecules ( don’t fold )
strong structural role
high proportion of amino acids with small hydrophobic R groups
long polypeptide chains run parallel and hydrogen bonds form crosslinks between them
eg. keratin, elastin, collagen

80
Q

what is keratin ( properties and examples ) ?

A

fibrous protein :flexible or tough and hard
large proportion of the sulphur containing amino acid cysteine= strong disulphide bonds to form strong inflexible and insoluble
waterproof
less disulphide bonds = more flexible

eg. hair, skin , nails , horns

81
Q

what is elastin ( properties and examples ) ?

A

fibrous protein : made from stretchy molecules called tropolastin found in the elastin fibres
cross-linking and coiling make it strong and extendable
found in the blood vessels , alveoli, bladder, stomach and skin

82
Q

what is collagen ( properties and examples )?

A

fibrous protein ; connective tissue found in skin, tendons ,ligaments and the nervous system
provides mechanical strength and flexibility ( does not stretch )
every third amino acid in the polypeptide is glycine which means it can pack into a helix with many hydrogen bonds between

83
Q

what are globular proteins ?

A

spherical shape (tightly folded polypeptide chain)
hydrophobic groups are on the inside and hydrophilic groups are on the outside
hydrophilic groups associate with water to make them soluble
eg. haemoglobin, insulin , pepsin

84
Q

what is insulin ?

A

it is a hormone that regulates the blood glucose concentration
it is soluble in the bloodstream
it fits precise fit into specific membrane receptors
it has two polypeptide chains that fold into tertiary structure and are then joined by disulphide bonds

85
Q

what type of molecule is pepsin ?

A

enzyme - single polypeptide chain of amino acid

86
Q

how do pepsins amino acids allow it to function in the acidic environment of the stomach ?

A

pepsins amino acids have acidic R groups = stable in acidic environment
the tertiary structure is also held together by H bonds and disulphide bridges

87
Q

what is catalase ?

A

an enzyme which interacts with hydrogen peroxide to speed up its breakdown into water and oxygen

88
Q

describe the structure of catalase ?

A

a quaternary protein with 4 haem prosthetic groups
iron 2 ions allow for the interaction with hydrogen peroxide

89
Q

what is protein denaturation ?

A

bonds break and they cant perform their function

90
Q

what conditions cause denaturation of proteins?

A

changes in temperature, pH, salt concentration

91
Q

how are fibrous proteins affected by denaturation?

A

lose structural strength

92
Q

how are globular proteins affected by denaturation?

A

become insoluble and inactive ( shape changes )

93
Q

describe the iodine test ?

A

iodine is added to test for starch
a negative result is orange
a positive result is blue black

94
Q

describe the biuret test ?

A

biurets solution is added to test for proteins
+ result = purple lilac ( because of the peptide bonds between the amino acids )
- result = stay blue

95
Q

what is the purpose of chromatography ?

A

separation of the components of a mixture and identification of them

96
Q

describe the two stages of chromatography ?

A

stationary phase - where molecules cannot move
mobile phase - solutes can move - liquid solvent

97
Q

how do you calculate Rf value ?

A

distance travelled by pigment divided by the distance travelled by solvent

biology (3 decks)

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