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B2 > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

State properties of water

A
  • metabolite
  • solvent
  • H bonds
  • High specific heat capacity
  • High latent heat of vaporisation
  • liquid water denser than ice
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2
Q

How is water a metabolite

A

Used in hydrolysis, made in condensation

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3
Q

How is water a solvent

A

Polar molecule, dissolves solutes for transport/ reactions

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4
Q

what does hydrogen bonding in water allow

A

Allows cohesion for transpiration and pond-skater habitat

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5
Q

Role of high specific heat capacity in water

A

Acts as a buffer to temperature change

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6
Q

Role of high latent heat of vaporisation of water

A

Reduction of body temperature via sweating

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7
Q

Role of liquid water denser being than ice

A

Aquatic habitats protected under floating ice as the ice insulates water below

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8
Q

Define monomer

A

Individual molecules that can make up a polymer

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9
Q

Define polymer

A

Long chain of many individual monomers that have been bonded together in a repeating pattern via condensation reactions

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10
Q

What are condensation reactions

A

Occur when two molecules combine to form a more complex molecule with the removal of water

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11
Q

What are hydrolysis reactions

A

Occur when larger molecules are broken down into smaller molecules with the addition of water

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12
Q

What type of bonds join monomers together

A

Covalent

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13
Q

What type of molecules are joined by H bonds

A
  • polar molecules
  • stabilises larger structures
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14
Q

What are monosaccharides

A

Are the simplest carbohydrates, being sweet tasting, soluble and contain many C-H bonds for energy storage

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15
Q

What are isomers

A
  • Molecules with the same formula but different atom arrangement in space
  • example: alpha and beta glucose
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16
Q

What are disaccharides

A

Formed when two monomers react in a condensation reaction, forming a glycosidic bond

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17
Q

What monomers make maltose

A

a Glucose + a Glucose

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18
Q

What monomers make lactose

A

a Glucose + B Galactose

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19
Q

What monomers make sucrose

A

a Glucose + Fructose

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20
Q

What makes cellobiose

A

B Glucose + B Glucose

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21
Q

What is the 1 non-reducing sugar

A

Sucrose

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22
Q

What are the 2 reducing sugars

A
  • Maltose and lactose
  • all monosaccharides are reducing sugars
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23
Q

What test is used to qualitatively test the presence of reducing and non- reducing sugars

A

Benedict’s solution

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24
Q

What will Benedict’s test look like for reducing sugars

A
  • heating with Benedict’s solution changes colour from blue to green, yellow, or orange-red
  • reducing sugars reduce Cu^2+ to Cu forming copper (I) oxide precipitate
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25
Q

Why can’t you use Benedict’s to directly test for non- reducing sugars

A
  • non-reducing sugars can’t reduce Benedict’s until the glycosidic bond is hydrolysed
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26
Q

How do you carry out Benedict’s test on non- reducing sugars

A
  1. Boil with HCl to break into monosaccharides (reducing sugars)
  2. Cool and add sodium hydrogen carbonate to neutralise
  3. Test with Benedict’s and look for the same colour change as before
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27
Q

How can the concentration of reducing sugars be quantitatively measured

A

Colorimetry

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28
Q

How do you carry out colorimetry

A
  1. Centrifuge separates ppt and unreacted Benedict’s
  2. Supernatant placed in a cuvette and into colorimeter with red filter
  3. Transmission of light measured, using zero reading with water
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29
Q

what does high transmission/low absorbance mean

A

high amount of reducing sugars

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30
Q

what does low transmission/ high absorbance mean

A

low amount of reducing sugars

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31
Q

what’s a calibration curve

A

uses a series of known concentrations and transmissions used to estimate the concentration of sample sugars

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32
Q

what can reducing sugar concentration also be measured with

A

reagent test strips

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33
Q

how are reagent strips used

A
  • strip dipped into the sample solution and the colour is compared to a calibration card, showing how colour relates to sugar concentration
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34
Q

give an example of what reagent test strips can be used for

A

urine testing for sugar in diabetics

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35
Q

what’s starch

A

a plant-based energy storage molecule made of two types of alpha glucose polymers: amylose and amylopectin

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36
Q

what are the properties of starch and why

A
  • insoluble - no effect on water potential
  • compact granules - take up little space
  • branching - multiple sites for rapid hydrolysis
  • large molecule - many glucose for respiration
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37
Q

what are the two types of starch

A
  • amylose
  • amylopectin
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38
Q

explain structure of amylose

A
  • long chain of a-glucose molecules
  • has 1-4 glycosidic bonds
  • amylose coils into spiral shape
  • OH groups holding the spiral in place
  • OH group on C 2 situated are on inside of coil, making the molecule less soluble and allowing H bonds to form to maintain the coil’s structure
  • no branches
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39
Q

describe the structure of amylopectin

A
  • a-glucose chain joined by 1,4 glycosidic bonds but in addition have branches formed by 1-6 glycosidic bonds
  • coils into spiral shape but also has branches
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40
Q

what’s glycogen

A

animal- based energy storage polysaccharide made of a-glucose

41
Q

state the properties of glycogen and why

A
  • insoluble - no effect on water potential
  • compact granules - takes up little space
  • branching - multiple sites for rapid hydrolysis
  • large molecule - many glucose molecules for respiration
42
Q

describe the structure of glycogen

A
  • a-glucose chain joined by 1-4 glycosidic bonds, branches formed by 1-6 glycosidic bonds
43
Q

how does the structure of glycogen differ from that of amylopectin

A
  • glycogen chains smaller so has less tendency to coil
  • glycogen has more branches, makes it more compact and easier to remove monomers ( for quicker enrgy release as animals are more active)
44
Q

what’s cellulose made of

A
  • long chains of B-glucose joined by 1-4 glycosidic bonds
  • found in plant cell walls
45
Q

describe and explain the structure of cellulose

A
  • straight, unbranched chains run parallel to one another due to B-glucose inverting 180 degrees alternatively. This allows H bonds to form between B glucose molecules
  • hydrogen bonds provide strength as they produce microfibrils of 60-70 chains
  • hydroxyl group on C2 sticks out so H bonds form between chains
46
Q

why is cellulose insoluble

A
  • doesn’t affect water potential but permeable to solutes
47
Q

why do macrofibrils in cellulose run in different directions

A

for extra strength

48
Q

what’s the test for starch

A
  • iodine
  • yellow to blue-black for +ve test
49
Q

what are lipids are made from

A
  • glycerol and fatty acids
50
Q

how many -OH groups does glycerol have

A

3

51
Q

what do fatty acids contain

A
  • COOH group and hydrocarbon chain
52
Q

what are saturated fatty acids

A

fatty acids with only single bonds in hydrocarbon chain

53
Q

what are unsaturated fatty acids

A

fatty acids with double bonds

54
Q

what’s the difference in structure of triglycerides and phospholipids

A
  • triglyceride: glycerol + 3 fatty acids
  • phospholipid: glycerol + 2 fatty acids + 1 phosphate
55
Q

where are ester bonds formed

A
  • form between fatty acids and glycerol
  • covalent bonds formed in condensation and broken in hydrolysis
56
Q

are fatty acids in triglycerides all the same

A

no, they can be different

57
Q

what type of molecules are lipids

A

macromolecules ( very large organic molecules)

58
Q

explain the role of phospholipids in in the phospholipid bilayer/ miscelle

A
  • phospholipids are polar with hydrophilic phosphate heads oriented towards water and hydrophobic fatty acids tail facing away from water
59
Q

what is meant by membranes being selectively permeable

A

allow only small non-polar particles to pass

60
Q

what’s cholesterol (steroid alcohol) and what’s its role

A
  • lipid with 4 carbon rings
  • regulates bilayer fluidity by preventing it from being too fluid at high temp or too rigid at low temp
61
Q

give an example of a steroid hormone formed form cholesterol

A

oestrogen

62
Q

what’s the test for lipids

A
  • emulsion test
    1. sample mixed with ethanol
    2. filter the solution and add to clean test tube of water
    3. a cloudy- white emulsion indicates a +ve test as lipids form from droplets
63
Q

what are proteins made of

A

amino acids

64
Q

what functional groups do amino acids have

A
  • NH2 (amino group)
  • COOH (carboxyl group)
    H2N(HCR)COOH
65
Q

can animals synthesise essential amino acids

A

no

66
Q

how many essential amino acids are there

A

9

67
Q

can plants synthesise all their amino acids

A

yes provided that they have enough nitrogen

68
Q

R groups can vary in…

A

size, charge and polarity

69
Q

what are the bonds between amino acids and how are they formed

A
  • peptide bonds
  • formed from condensation reactions between carboxyl and amino groups of adjacent amino acids
70
Q

the peptide bond is a covalent bond and amino acids join to make a…..

A

polypeptide

71
Q

what’s primary structure

A
  • the sequence of amino acids, determines the higher structure levels
72
Q

what’s secondary structure

A
  • due to H bonds and forms a- helices and B-pleated
73
Q

what’s tertiary structure

A
  • overall 3D shape formed by ionic, disulfide and H bonds, plus hydrophobic/hydrophilic interaction
74
Q

what’s quaternary structure

A
  • formed when multiple polypetides bind, often with prosthetic groups
75
Q

features of fibrous proteins

A
  • contain repeating sequences of amino acids and are insoluble, forming structural fibres, such as collagen or keratin
  • metabolically inactive
76
Q

what’s a prosthetic group

A

non-protein component that forms a permanent part of a protein molecule

77
Q

what’s the function of collagen

A

provides mechanical support

78
Q

where’s collagen found

A
  • in artery walls, prevents artery bursting when withstanding high bp
  • tendon which connect muscle to bone allowing them to move
  • cartilage
79
Q

structure and function of keratin

A
  • rich in cysteine so lots of disulfide bridges in addition to H bonds make it very strong
  • provides mechanical protection but also provides an impermeable barrier to infection
80
Q

where’s keratin found

A

nails, hair, claws

81
Q

structure and function of elastin

A
  • cross-linking and coiling make elastin strong and extensible
  • allows stretching
82
Q

where’s elastin found

A
  • skin
  • lungs, allowing them to inflate and deflate
  • in blood vessels to help them stretch and recoil to help maintain pressure
83
Q

feature of globular proteins

A
  • spherical shape with core of hydrophobic interactions
  • hydrophilic R groups on the outside
  • metabolically active
84
Q

structure of Hb

A
  • 4* structure of Hb consists of for polypeptides: 2 a and 2 B (each has its own 3* structure)
  • each polypeptide has a haem group with an iron ion (prosthetic group)
  • conjugated protein = globular protein with a prosthetic group
85
Q

function of Hb

A
  • carries O2 from lungs to tissues
  • one oxygen molecule binds to each iron ion
86
Q

function of pepsin

A

enzyme that digests protein in the stomach

87
Q

structure of pepsin

A
  • very few amino acids with basic R groups, helps maintain stability as there are few basic groups to accept H+ so little effect on structure
  • 3* structure held together by 2 disulfide bridges and H bonds
88
Q

test for proteins

A
  • biuret test
    1. a sample is added to clean test tube
    2. biuret A contains NaOH, added to sample
    3. Biuret B contains Copper (II) Sulphate, added to sample
    4. +ve state causes a colour change from blue to lilac as Cu2+ react with nitrogen atoms in the polypeptide chain
89
Q

what do biosensors do

A

measure a chemical variable by turning it into an electrical signal

90
Q

important application of biosensors

A
  • detecting contaminants in food
  • detecting air-borne bacteria
91
Q

how do biosensors work

A
  1. molecule to be measured binds to receptors in biological layer
  2. chemical variable converted into electrical signal
92
Q

what’s chromatography used for

A

separates a mixture into components based on the speed of movement through phases

93
Q

what’s the stationary phase in TLC

A

chromatography paper made of cellulose, or TLC plate with free OH- groups. Sample molecules adhere to this

94
Q

what’s the mobile phase in TLC

A

solvent carrying sample of biological molecules, often water or ethanol

95
Q

how do you calculate Rf

A

Rf = distance moved by spot/ distance moved by solvent

96
Q

colourless solutions in TLC can be observed using:

A
  • UV light
  • ninhydrin
  • iodine
97
Q

why do polar molecules move slower than non-polar ones

A

polar molecules adhere to the -OH groups on the stationary phase (TLC plate) strongly (more attracted)

98
Q

properties and function of insulin

A
  • made up of 2 polypeptide chains
  • A chain begins with a- helix and B chain ends with section of B pleat
  • both chains fold into 3* stricture bonded by disulfide links
    hydrophilic R groups on outside making it soluble
  • insulin binds to receptors in muscle and liver cells causing them to increase their uptake of glucose

B2 (6 decks)

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