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1.2 Biological molecules 1 (and 1.1 water) Flashcards

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1
Q

what is the general formula for monosaccharides

A

(CH2O)n

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2
Q

name 5 monosaccharides

A

Galactose, fructose, alpha-glucose, beta-glucose

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3
Q

describe triose sugars

A

-have 3 carbon atoms
-molecular formula C3H6O3
-important in the mitochondria where glucose is broken down into triose sugars during respiration

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4
Q

describe pentose sugars

A

-have 5 carbon atoms
-molecular formula C5H10O5
-E.G. ribose and deoxyribose

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5
Q

describe hexose sugars

A

-have 6 carbon atoms
-molecular formula C6H12O6
-E.G. glucose, fructose, galactose

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6
Q

how are disaccharides formed

A

2 monosaccharides join together in a condensation reaction
a glycosidic bond (type of covalent bond) forms between the 2 monosaccharides
forming a disaccharide and 1 molecule of water is removed

there can be a 1,4-glycosidic bond or a 1,6-glycosidic bond

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7
Q

name 3 disaccharides

A

maltose
sucrose
lactose
all have the molecular formula C12H22O11

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8
Q

what 2 monosaccharides form the disaccharide maltose

A

2 alpha glucose

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9
Q

what 2 monosaccharides form the disaccharide sucrose

A

alpha glucose + fructose

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10
Q

what 2 monosaccharides form the disaccharide lactose

A

alpha glucose + beta galactose

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11
Q

how are polysaccharides formed

A

many monosaccharides join during a condensation reaction, where glycosidic bonds form and water molecules are lost

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12
Q

why are polysaccharides good storage molecules

A

-polysaccharides are very compact, so many can fit inside a cell
-glycosidic bonds are easily broken, so monosaccharide units can be easily released
-not very water soluble, so have little affect on water potential and cause no osmotic water movements

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13
Q

what happens during hydrolysis

A

-the opposite of a condensation reaction
-a water molecule is added to break the bonds

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14
Q

what are the 2 types of polysaccharides

A

oligosaccharides - have 3-10 sugar units
true polysaccharides - have 11 or more sugar units

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15
Q

properties of starch
what is starch made up off

A

-insoluble, so doesn’t affect water potential and creates no osmotic water movements
-compact
-can release glucose, so is an energy store
-large, so doesn’t diffuse out of cells

alpha glucose in the form of the 2 compounds: amylose + amylopectin

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16
Q

describe amylose

A

-made up of only alpha-glucose joined by 1,4-glycosidic bonds
-forming a coiled chain and an alpha-helical structure, making it harder for hydrolysis to occur
-the coiled shape makes it compact

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17
Q

describe amylopectin

A

-made up of only alpha-glucose joined by both 1,4-glycosidic bonds and 1,6-glycosidic bonds
-forming branching chains, but this leaves many terminal glucose molecules so hydrolysis can happen easily (a water molecule can join on)

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18
Q

describe glycogen

A

a polysaccharide and polymer
glycogen is the only carboydrate energy store found in animals (but also found in some plants)
made up of only alpha-glucose units
both 1,4-glycosidic bonds and 1,6-glycosidic bonds
(has more 1,6-glycosidic bonds than amylopectin)
many branched chains, so can release glucose rapidly
compact like starch

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19
Q

how is cellulose formed

A

-made up of only beta-glucose monomer units
-bonded together by only 1,4-glycosidic bonds, formed during condensation where a water molecule is lost
-each beta glucose molecule must be inverted 180 degrees from the previous beta glucose molecule
-hydrogen bonds form between the hydroxyl groups on adjacent chains
-as oxygen is more electronegative than hydrogen, it attracts the pair of electrons closer to itself
-causing hydrogen bonds to form between the delta negative oxygen atom and delta positive hydrogen atom
-this crosslinking between cellulose chains holds them strongly together
-cellulose chains bundle together to form microfibrils, these bundle together to form fibers

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20
Q

what are the properties of cellulose within the cell wall

A

-the hydrogen bonds hold cellulose chains together and make cellulose very strong
-strong to prevent cell lysis, maintain turdigity, and resist turgor pressure
-cellulose molecules remain as very long, straight chains
-can’t be broken down by most animals
-beta glucose monomers in cellulose are polar, so water and minerals can diffuse through the cell wall

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21
Q

why can’t cellulose be broken down by most animals

A

Because most animals don’t contain the enzymes needed to break the 1,4-glycosidic bonds between molecules of beta-glucose, so cannot digest cellulose.
Therefore cellulose is a type of fibre.

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22
Q

why is water a polar molecule

A

-in a water molecule there is a covalent bond between the oxygen and hydrogen atoms.
-oxygen is more electronegative so pulls the shared pair of electrons in the covalent bond more towards itself.
(oxygen is more electronegative because it has a larger nucleus, so the pair of electrons are attracted to the larger number of positively charged protons)
-the oxygen atom becomes slightly δ−
(delta negative) and the hydrogen becomes slightly δ+ (delta positive)
-water has a permanent dipole

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23
Q

how do water molecules take part in hydrogen bonding

A

-the slightly negative oxygen atom on one water molecule will attract the slightly positive hydrogen molecule on another water molecule, forming a hydrogen bond between them (a weak electrostatic intermolecular force)
-although each hydrogen bond is weak, there are many of them, giving water a relatively high melting and boiling point compared to other molecules the same size, because it takes a lot of energy to break all the hydrogen bonds.

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24
Q

what are the 7 important properties of water

A

-is a polar solvent
-it’s maximum density is at 4 degrees celcius
-high specific heat capacity
-incompressible
-high surface tension
-cohesive
-adhesive

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25
Q

what is the meaning of dipole

A

the separation of charge when the pair of electrons in a covalent bond are not evenly shared
a polar molecule contains a dipole

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26
Q

describe how water is a polar solvent and why this is important

A

-water is a polar molecule allowing it to easily dissolve ionic and polar molecules
-water molecules are attracted to the ions in contact with the water
-water molecules cluster around each ion, separating them from the ionic lattice
-the delta positve hydrogen atoms are attracted to the negative ions
-and delta negative oxygen atoms are attracted to the positive ions

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27
Q

describe why water’s maximum density is 4 degrees celcius and why this is important

A

-as water condenses from a gas to a liquid it becomes more dense because more hydrogen bonds form between water molecules pulling them closer
-at 4 degrees celcius water is at it’s maximum density
-as water cools down further, water molecules form the maximum 4 hydrogen bonds each, to do this the water molecules must move apart into a regular structure
-ice is less dense than water
-ice forms an insulating layer above water, preventing water underneath from freezing
-protecting aquatic organisms
-as ice floats ontop off water it’s exposed to sunlight so melts quickly

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28
Q

describe how water has a high specific heat capacity and why this is important

A

-water has high specific heat capacity
-so releases and absorbs heat very slowly
-because the hydrogen bonds between molecules need a lot of energy to be broken
-the temperature of lakes and seas is stable throughout the year, making the habitats of aquatic organisms a stable environment
-water has a high melting point becuase the hydrogen bonds between molecules need a lot of energy to break
-they type of intermolecular force water has is hydrogen bonds, these are the strongest intermolecular force

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29
Q

why is water incompressible

A

it is a liquid

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30
Q

what is meant by “water molecules are cohesive” and why is this important

A

-cohesion is the attraction between molecules of the same type
-water molecules are attracted to eachother due to hydrogen bonds formed between molecules
-allowing for the movement of water from the roots to the leaves

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31
Q

what is meant by cohesion and adhesion

A

cohesion - the attraction between molecules of the same type
adhesion - the attraction of molecules of different types

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32
Q

what is meant by “water molecules are adhesive” and why is this important

A

-water molecules are attracted to molecules of different types
-only when the molecules are polar or charged
-allowing surface tension and capillary action

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33
Q

describe why water has high surface tension and why this is important

A

-water molecules at the surface of water are more attracted to eachother than to molecules in the air
-this uneven attraction pulls the water molecules towards the rest of the water molecules below
-so theres lots of tension at the surface of water
-important for plant transport systems and animals which can walk on the surface of water

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34
Q

describe the basic structure of an amino acid

A

-1 central carbon atom bonded to
-an amine group (NH2)
-a carboxyl group (COOH)
-a hydrogen atom
-a R group

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35
Q

how is a dipeptide made

A

-2 amino acid monomers join to make 1 dipeptide.
-1 of the amino acids is inverted, so the amine group and carboxyl group are next to eachother and can react together
-in a condensation reaction, where 1 molecule of water is lost.
-a peptide bond forms between the 2 amino acids, forming a dipeptide

36
Q

how is a polypeptide chain made

A

2 amino acid monomers react to form a dipeptide.
More amino acids react with the dipeptide forming a polypeptide.
When the polypeptide folds, coils, or associates with other polypeptide chain, a protein is formed.

37
Q

what is the primary structure of a protein

A

the sequence of amino acids that make up the polypeptide held together by peptide bonds

38
Q

what is the secondary structure of a protein

A

-the polypeptide chain curl and fold into a regular repeating structure held together by hydrogen bonds
-either in an alpha helix or beta pleated sheet

39
Q

how does a protein form the secondary structure alpha helix

A

-the polypeptide chain coils
-the hydrogen in the amine group (NH2) is slightly positive
-the oxygen in the carboxyl group (COOH) is slightly negative
-a hydrogen bond forms between the hydrogen on one amino acid and the oxygen on another amino acid
-the hydrogen bonds keeps the coil stable

40
Q

how does a protein form the secondary structure beta pleated sheet

A

-the polypeptide chains form a zig-zag and fold over themselves
-the hydrogen in the amino group (NH2) is slightly positive
-the oxygen in the carboxyl group (COOH) is slightly negative
-a hydrogen bond forms between the hydrogen on one amino acid and the oxygen on another amino acid
-the hydrogen bonds keeps the folded zig-zag shape stable

41
Q

what is the tertiary structure of a protein

A

the overall specific 3-D shape of a protein, determined by interactions between the R-groups and properties of R-groups

42
Q

how does the tertiary structure of a protein form

A

-the alpha-helices and beta pleated sheets twist to form a protein with a specific structure
-the structure is held in place by bonds formed between the R-groups of the amino acids
-these can be hydrogen, disulfide or ionic bonds or van der walls forces
-the structure is also determined by whether the R-groups are hydrophilic or hydrophobic

43
Q

describe the hydrogen bonds formed in the tertiary structure of a protein

A

-hydrogen bonds form between polar R-groups
-between any delta positive and delta negative atom

44
Q

describe the ionic bonds formed in the tertiary structure of a protein

A

-ionic bonds form between any positively and negatively charged R-groups

45
Q

describe the disulphide bonds formed in the tertiary structure of a protein

A

-disulphide bonds form between 2 sulfur atoms in cysteine groups
-the 2 cysteine groups are oxidised, forming a disulphide bond

46
Q

describe how R-groups being either hydrophilic or hydrophobic influences the structure of a protein

A

-amino acids with hydrophobic R-groups are found in the middle of the protein
-amino acids with hydrophilic R-groups are found on the outside of proteins

47
Q

what is the quaternary structure of a protein

A

the specific 3-D shape of a protein, determined by multiple polypeptide chains, and/or prosthetic groups bonded together

48
Q

how are proteins with quaternary structures formed

A

-multiple polypeptide chains with tertiary structures are bonded together by the same type of bonds in their tertiary structure
-prosthetic groups (non-protein groups) can be associated with the polypeptide chains, forming conjugated proteins

49
Q

what are 3 properties of all fibrous proteins

A

-contain long polypeptide chains with repeating sequences of amino acids
-the amino acids have non-polar R groups, so fibrous proteins are insoluble in water (the amino acids can’t interact with water)
-main uses are for structure
-fairly unreactive

50
Q

describe the structure of collagen

A

-the primary structure is a repeating sequence of 3 amino acids
-every 3rd amino acid is glycine
-glycine is the smallest R group (just H) of any amino acid
-allowing the polypeptides to wrap tightly
-made up of 3 alpha polypeptide chains
-this first forms a procollagen (triple helix with lose ends)
-procollagen peptidases remove the loose ends, creating a collagen molecule
-multiple collagen molecules come together to make a collagen fibril
-in the fibril the collagen molecules are staggered so there are no weak spots
-many fibrils form collagen fibers

51
Q

what is the main function of collagen

A

for strength - collagen has high tensile strength

52
Q

where is collagen found in the body, and what is it’s function

A

-collagen is found in artery walls to prevent vessels from bursting from high pressure
-collagen is used to make tendons
-tendons connect muscle to bone, allowing movement
-collagen is found in muscle, bone and skin

53
Q

what are the properties of all globular proteins

A

-spherical shape, with hydrophobic R-groups on the inside and hydrophilic R-groups on the outside
-soluble in water, hydrophilic R-groups react with water
-have very specific shapes to carry out specific functions e.g. enzymes
-reactive
-irregular amino acid sequences
-main uses are functional

54
Q

describe the structure of haemoglobin

A

-4 polypeptide chains (2 alpha globin and 2 beta globin)
-haemoglobin is a conjugated protein, it has 4 prosthetic haem groups (1 haem group for each polypeptide chain)
-a heam group contains an iron ion (Fe2+)

55
Q

what is the function of haemoglobin

A

-one haem group binds to one oxygen molecule, allowing haemoglobin to bind to 4 oxygen molecules at a time, maximising the amount of oxygen being carried through the blood
-oxygen is delivered to cells to be used for respiration

56
Q

name 3 globular proteins

A

haemoglobin
insulin
lysozyme

57
Q

name 3 fibrous proteins

A

collagen
keratin
elastin

58
Q

how does cellulose arrange itself around plant cells

A

cellulose fibres wrap around plant cells in many layers and at different angles

59
Q

describe Van der Walls forces in the tertiary structure of a protein

A

-weak forces of attraction between non-polar groups
-only occurs when atoms/molecules are very close to eachother
-caused by changing charges due to movements of electrons

60
Q

explain how the structure of glycogen is related to its function

3 marks

A

-branched chains leave many terminal glucose molecules so can easily undergo hydrolysis
-compact for its function as an energy storage molecule
-insoluble so doesn’t affect osmosis/water potential + large molecules so don’t leave cells

61
Q

what are glycoproteins

A

-conjugated proteins
-a protein with a carbohydrate prosthetic group

62
Q

explain how and why glycoproteins are useful in the body

A

-the carbohydrate prosthetic group on the molecule holds onto lots of water and makes it harder for protease to digest it
-so the water-holding properties of glycoproteins make them slippery, reducing friction
-useful in mucus which lines the stomach, protecting the protein walls from being digested

63
Q

what are lipoprotiens

A

-conjugated proteins
-proteins with a lipid prosthetic group

64
Q

explain how and why lipoproteins are useful in the body

A

-the lipid prosthetic groups binds to cholesterol (also a lipid)
-so lipoproteins transport cholesterol in the blood
-there are 2 main forms of lipoproteins in the blood: low density lipoporoteins and high density lipoproteins
-HDLs contain more protein than LDLs, making HDLs denser because proteins are more compact than lipids

65
Q

describe the test for proteins

A

-add biuret reagent (sodium hydroxide solution and copper sulfate solution) to the sample in a test tube
-a positive test will turn from blue to purple
-this indicates the presence of peptide bonds, therefore the sample is a protein

66
Q

describe the test for lipids

A

-emulsion test for lipids
-add ethanol to the test tube with the sample
-mix till the lipid has dissolved
-add distilled water and mix the mixture
-for a positive test, the mixture will turn from colourless to a cloudy white precipitate
-the cloudy white precipitate if formed because lipids are insoluble in water so they come out of the solution to form an emulsion

67
Q

what 2 organic chemicals are fats and oils made up off

A

glycerol (propane-1,2,3-triol) and fatty acids

68
Q

what 2 ways do fatty acids differ

A

-the length of the carbon chain (depending on the size of the R group)
-fatty acids can be saturated or unsaturated

69
Q

what are saturated fatty acids, what sate are they at room temperature and where are they found

A

-carbon atoms are joined together by single covalent bonds
-mostly solid at room temperature
-mostly meat and dairy sources

70
Q

what are unsaturated fatty acids

A

-the carbon chain has one or more double covalent bond
-mostly liquid at room temperature
-mostly plant sources
-a monounsaturated fatty acid has 1 double covalent bond
-a polyunsaturated fatty acid has 2 or more double covalent bonds

71
Q

how is a triglyceride formed

A

-through esterification (type of condensation reaction)

72
Q

what is esterification

A

-a type of condensation reaction where ester bonds are formed
-between the carboxyl group (-COOH) of a fatty acid and 1 of the hydroxyl groups (-OH) on the glycerol
-a water molecule is lost for every ester bond formed

73
Q

how is a triglyceride formed

A

-1 glycerol molecule + 3 fatty acids
- esterification happens between the carboxyl group on 1 of the fatty acids and 1 of the hydroxyl groups on the glycerol
-3 ester bonds are formed
-3 water molecules are lost

74
Q

how much more energy do lipids store compared to carbohydrates

A

lipids store 3 times as much energy as the same mass of carbohydrates

75
Q

what are the functions of lipids

A

energy stores
waterproofing
good insulators
all lipids dissolve in organic solvents
low density

76
Q

how is the structure of lipids adapted to its function of waterproofing

A

lipids are hydrophobic

77
Q

2 examples of how lipids are good insulators

A

-a fatty sheath insulates nerves so electrical impulses can travel faster
-they prevent heat loss in animals, like the thick layer of blubber in whales

78
Q

an example of why the low density property of lipids is useful

A

-the body fat in water mammals is made from lipids which are low density, helping them float on water easily

79
Q

an example of why lipids’ unique dissolving properties are useful

A

-lipids dissolve in organic solvents
-but are insoluble in water
-so lipids don’t affect water-based chemical reactions in the cytoplasm or affect water potential of cells

80
Q

how are phospholipids formed

A

-esterificstion
-inorganic phosphate ions (-PO4^3-) are present in the cytoplasm
-one of the hydroxyl groups on glycerol undergoes esterification with a phosphate group instead of a 3rd fatty acid
-phospholipids are made up of: 1 phosphate group, 1 glycerol, 2 fatty acids

81
Q

describe insulin as a globular protein

structure and function

A

-2 polypeptide chains: 1 alpha-helix 1 beta pleated sheet
-these 2 chains are held together by disulfide bonds
-the globular shape of insulin allows it to be specifically binded to receptors on cell membranes
-insulin travels in the blood, so it has hydrophilic R groups on the outside, so it is soluble
-insulin is a hormone used to lower blood glucose levels

82
Q

describe the structure of the globular protein lysozyme

A

-made of 1 polypeptide chain (can be either alpha helix or beta pleated sheet)
-it is a bacterial enzyme so the specific shape of the active site means it has a complementary fit with the substrate molecule in the bacterial cell wall

83
Q

describe the function of lysozyme

A

-an enzyme which catalyses the breakdown of a molecule found in the bacterial cell wall
-helping defend the body from bacteria

84
Q

why are globular proteins soluble

A

globular proteins have amino acids with hydrophilic r groups on their surface and amino acids with hydrophobic amino acids in the center
so the hydrophilic amino acids can interact with water molecules

85
Q

what is the function and structure of keratin

A

-found in skin, hair and nails
-strong
-insoluble
-contains a large proportion of cysteine
-cysteine is a sulfur containing amino acid which forms disulfide bonds
-so keratin has a large proportion of disulfide bonds, making it very strong
-the amound

86
Q

what is the function and structure of elastin

A

-found in skin, making it elastic
-found in artery walls, as blood flows through the artery wall stretches and then recoils back to its original shape
-the hydrophobic regions on elastin molecules associate causing elastin molecules to group together
-when stretched the molecules move apart but remain attached at the crosslink
-after stretching the elsatin molecules reassociate making elastin elastic

87
Q

how does the ration of C:H:O compare in carbohydrates and lipids

A

in carbohydrates: 1:2:1
in lipids: 1:2: less than 1
so in lipids there are very few oxygen atoms and many hydrogen atoms

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