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A-Level Biology > 2.1.2 Biological molecules > Flashcards

2.1.2 Biological molecules Flashcards

(93 cards)

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1
Q

how polarity in water is formed (biology)

A

O pulls pair of electrons in covalent bond closer to it and further from H as has more protons
O has partially negative charge
H has partially positive charge

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2
Q

properties of water

A 
polar
liquid at room temperature 
high specific heat capacity (SHC)
high latent heat of vaporisation (LHV)
high cohesion/adhesion 
high surface tension 
water is denser than ice
not compressible (liquid)
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3
Q

roles of water for living organisms

A

site of chemical reactions (solvent)
stable enzyme-controlled reactions (high SHC)
allows molecules and ions to be transported easier in living things (solvent)
stable environment of aquatic organisms (high SHC and LHV)
columns of water pulled up by xylem vessels (adhesion due to hydrogen bonding)
important metabolite (photosynthesis, hydrolysis)

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4
Q

monosaccharide definition

A

sugar monomer

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5
Q

carbohydrate uses

A

source of energy (glucose)
store of energy (starch, glycogen)
structural unit (cellulose cell wall, chitin cell wall of fungi)

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6
Q

monosaccharide properties

A

sugars (sweet)
soluble in water
insoluble in non-polar solvents

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7
Q

reducing sugars examples

A

maltose
lactose
all monosaccharides

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8
Q

non-reducing sugars

A

most disaccharides (e.g. sucrose)

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9
Q

how disaccharides are formed

A

condensation reaction to form glycosidic bond between two monosaccharides

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10
Q

monosaccharides of maltose

A

alpha-glucose + alpha-glucose

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11
Q

monosaccharides of sucrose

A

alpha-glucose + fructose

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12
Q

monosaccharides of lactose

A

beta-galactose + beta-glucose

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13
Q

monosaccharides of cellobiose

A

beta-glucose + beta-glucose

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14
Q

how polymers are formed and broken down

A 
condensation reaction (release water molecule)
hydrolysis reaction (requires water molecule)
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15
Q

starch structure

A

only alpha-glucose

amylose + amylopectin

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16
Q

amylose structure

A

long
coiled (hydroxyl bonds create hydrogen bonds to maintain structure)
unbranched (1-4 glycosidic bonds only)
good for storage (compact)

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17
Q

amylopectin structure

A

long
also coil due to hydrogen bonds
branched due to 1,6-glycosidic bonds
more accessible ends for enzymes for faster hydrolysis into alpha-glucose

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18
Q

properties and function of starch

A

major carbohydrate storage molecule in plants
stored as intracellular starch grains (plastids)
produced from glucose made in photosynthesis
broken down during respiration for energy
insoluble so doesn’t affect water potential

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19
Q

glycogen structure

A

long
highly-branched (many 1,6 glycosidic bonds)
more accessible ends to enzymes (more than amylopectin) so faster hydrolysis into alpha-glucose

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20
Q

glycogen function and properties

A

main energy storage in animals
more glucose residue branches so energy is released quickly (animals have higher metabolism than plants)
stored in liver and muscles
less soluble, more compact than starch (animals have higher metabolism than plants)

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21
Q

cellulose structure

A

beta-glucose orientated 180° to form straight chains (prevent coiling)
1-4 glycosidic bonds
hydrogen bonding between adjacent chains to form microfibrils (more tensile strength)
bundles to form macrofibrils that criss-cross (more tensile strength)

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22
Q

cellulose cell wall features and role

A

tough, insoluble
hard to digest (strong glycosidic bonds, most animals lack necessary enzymes)
high tensile strength (glycosidic bonds, hydrogen bonds between chains) so doesn’t burst when turgid, support whole plant
permeable (gaps between macrofibrils)
can be reinforced (e.g. lignin, cutin)

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23
Q

other structural polysaccharides

A

peptidoglycan (bacterial cell wall, arranged similarly to cellulose)
chitin (exoskeleton of insects and crustaceans, fungi cell wall, arranged similarly to cellulose)

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24
Q

lipid general features

A

non-polar
insoluble in water, dissolve in alcohol
less dense than water
soluble in non-polar solvents

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25
glycerol structure
``` 3 carbon molecules 3 hydroxyl (-OH groups) attached to carbons ```
26
fatty acid structure
carboxyl group (-COOH) attached to hydrocarbon tail (2-20 carbons long) acid as can dissociate H+ ions can have saturated or unsaturated hydrocarbon tail
27
effect of double bond on hydrocarbon tail
creates “kink” at double bond pushes molecule slightly apart reduces intermolecular interactions between molecules so more fluid, lower MP
28
triglyceride structure
1 glycerol bonded to 3 fatty acids | by ester bonds formed in condensation reactions
29
ester bond
bond formed between fatty acids (or phosphate group) and triglyceride formed between carboxyl group (-COOH) of fatty acid and hydroxyl group between hydroxyl groups for phosphate released water molecule per bond esterification reaction
30
functions of triglycerides
energy source (broken down in respiration to provide ATP, releases around double energy than carbohydrates) energy store (insoluble so doesn’t affect water potential of adipose tissue) insulation (heat insulator e.g. blubber, electrical insulator on nerve cells) buoyancy (less dense than water) protection (can absorb shock when surrounds organs)
31
phospholipid structure
1 glycerol bound to 2 fatty acids, 1 phosphate group by ester bonds hydrophilic phosphate head (as negative charge) hydrophobic fatty acid tails amphiphatic
32
behaviour of phospholipids in watee
hydrophilic phosphate heads face towards regions of water hydrophobic fatty acid tails turn away from regions of water forms bilayer or micelles
33
micelle definition
hydrophobic tails inside structure | hydrophilic heads facing outwards towards regions of water
34
sterols definition
complex alcohol molecules based on 4 carbon ring structure with hydroxyl group at one end (-OH) e.g. cholesterol
35
cholesterol structure
steroid nucleus (4 carbon rings) hydroxyl group at one end hydrocarbon side chain at other end
36
cholesterol functions
manufacture in liver and intestine formation + stability of plasma membrane synthesis of steroid hormone can pass through plasma membrane because small + hydrophobic
37
amino acid definition
monomers of all proteins | all have same basic structure
38
protein functions
structural: muscles add of protein, whore catalytic: form enzymes carriers and pores: carrier and channel proteins of plasma membrane
39
amino acid general structure
carboxyl group amino group central hydrogen varying R group
40
buffer definition
substance that helps to resist large changes in pH
41
how amino acids join and break up
condensation reaction forms peptide bond (OCHN) between amino group of one amino acid and carboxyl group of another amino acid release water hydrolysis reaction breaks peptide bond requires water forms 2 amino acids
42
primary structure definition
sequence of amino acids in a polypeptide chain
43
secondary structure definition
coiling or folding of peptide chain to form alpha-helices or beta-pleated sheets due to hydrogen bonding
44
why primary structure is important
determines shape of molecule (determines secondary, tertiary, quaternary structure) many possible sequences so gives each enzyme a unique shape and specific function
45
how alpha-helices form
peptide chain coils | held by hydrogen bonds that form between -NH group and -CO group of different amino acids
46
how beta-pleated sheets form
chains fold over on itself slightly to form zig-zag structure hydrogen bonds form between -NH and -CO groups of different amino acids
47
tertiary structure definition
overall 3D shape of protein molecule due to hydrogen bonding, disulphides bridges, ionic bonds and hydrophobic interactions between R groups of amino acids
48
quaternary structure definition
how multiple polypeptide chain subunits come together | only in complex proteins e.g. haemoglobin, insulin
49
hydrogen bonds in tertiary structure
between carboxyl, hydroxyl and amino groups | between R groups of amino acids
50
ionic bonds in tertiary structure
carboxyl and amino groups in R group ionise into COO- and NH3+ respectively oppositely charged ions strongly attracted to each other to form ionic bond
51
disulfide bridges in tertiary structure
R group of cysteine has sulfur | strong covalent bonds form between sulfur on R groups of 2 cysteine amino acids
52
hydrophobic/philic interactions in tertiary structure
hydrophobic parts tend to associate together at centre of polypeptide to avoid water hydrophilic parts found at edge of polypeptides close to water both causes twisting and changing of polypeptide chain’s shape
53
fibrous proteins features
regular, repetitive sequence of small range of amino acids insoluble in water long chain thin structure has structural function (e.g. collagen, elastin) little/no tertiary structure
54
globular protein features
relatively spherical shape soluble in water have very specific shape often have metabolic roles (enzymes, hormones, haemoglobin)
55
collagen properties and functions
mechanical strength (lots of hydrogen bonds) collagen around arteries to prevent from bursting tendons, cartilage and connective tissue made out of collagen bones made out of collagen then reinforced with calcium phosphate
56
keratin properties and functions
lots of cysteine so more disulfide bonds makes it strong provides mechanical protection, impermeable barrier to infection, waterproof found in nails, hair, claws, hooves, forms, scales, fur, feather (anywhere hard)
57
elastin properties and features
cross-linking + coiling so strong and extensible | found in skin, lungs, blood vessels (anything that needs to change its shape and stretch)
58
haemoglobin structure, properties and functions
two alpha and 2 beta globin chains each chain holds a prosthetic haem group (Fe2+) conjugated protein oxygen molecule binds to iron ions in haem groups and gets released at tissues
59
insulin structure, properties and functions
2 polypeptide chains (A and B) joined by disulfide bridges A chain begins with alpha helix B chain ends with beta pleated sheet hydrophilic R groups on outside of molecule so is soluble binds to glycoprotein receptors (muscle, fat cells) to increase intake and consumption of glucose from blood
60
pepsin structure, properties and functions
single polypeptide chain folded into symmetrical tertiary structure held by hydrogen bonds and disulfide bridges made up of 43 AA with acidic R groups few basic groups to accept hydrogen ions so low pH has little effect on structure
61
Ab initio (in italics) protein modelling
protein model is built based on physical and electrical properties of atoms in each amino acid in sequence multiple solutions can be made other methods required to deduce real structure of protein
62
comparative protein modelling
``` protein threading (scans a amino acid sequence against related proteins with known structures) produces set of possible models ```
63
Ca 2+ functions
``` involved in transmission of nervous impulses regulating of protein channels muscle contractions hardening of teeth and bones ```
64
Na + functions
involved in transmission of nervous impulses active transport Na+ pump co-transport of glucose and amino acids across membranes
65
K + functions
Involved in transmission of nervous impulses active transport plant cell turgidity
66
H + functions
The higher the concentration, the lower the pH of bodily fluids
67
NH4 + functions
Source of nitrogen used to make organic molecules
68
NO3 - functions
Source of nitrogen used to make organic molecules
69
HCO3 - functions
Involved in the regulation of blood pH and transport of carbon dioxide in the blood
70
Cl - functions
involved in transport of carbon dioxide in the blood through the chloride shift production of hydrochloric acid
71
allosteric effect
binding of ligand to one site of protein molecule so properties of another sire on same protein molecule are affected
72
ligand meaning
ion or molecule that binds to another (usually larger) molecule
73
PO4 3- functions
Component of biological molecules such as nucleotides, ATP and the formation of the phospholipid bilayer
74
OH - functions
The higher the concentration, the higher the pH of bodily fluids
75
deficiency definition
when organism doesn’t have enough of a particular inorganic ion
76
test for starch
add iodine dissolved in potassium iodide to sample positive if yellow-brown turns blue black triiodide ions slips into middle of amylose helix, causes colour change
77
test for reducing sugars
add Benedict’s solution in excess (alkaline copper (II) sulfate) heat in water bath (80°C, 3 minutes) positive if colour change from blue to brick-red and anything in between blue Cu 2+ ions turn into brick red Cu + ions as are donated electrons from reducing sugars
78
test for non-reducing sugars
test for reducing sugars first take separate sample and boil with hydrochloric acid (hydrolyse to form monosaccharides) cool solution, neutralise using hydrogencarbonate solution test for reducing sugars again positive if only second test has colour change
79
test for lipids
mix sample throughout with ethanol filter and pour solution into water in clean test tube positive if cloudy white emulsion forms tiny lipid droplets come out of ethanol solution when mixed with water
80
test for proteins
add biuret A (sodium hydroxide) add biuret B (copper sulfate) positive if lilac-colour formed complex formed between Cu 2+ and nitrogen atom in peptide chain
81
quantitative test for reducing sugar
conduct reducing sugar test with excess Benedict’s solution separate unreacted Benedict’s solution using centrifuge collect supernatant using pipette and place into cuvette place (red) colour filter into colorimeter calibrate colorimeter using distilled water test supernatant with colorimeter less transmission / more absorption = more unreacted copper sulfate solution = less reducing sugar more transmission / less absorption = less copper dilate solution = more reducing sugar
82
creating calibration curve
carry out Benedict’s test on samples of known concentrations of reducing sugar separate Benedict’s solution from each sample with centrifuge use colorimeter and record percentage transmission of light through each supernatant plot graph (transmission of light against glucose concentration) and draw line of best fit can estimate glucose concentration of unknown samples with transmission readings
83
biosensor definition
takes biological or chemical variable hard to measure and converts it into electrical signal
84
biosensors general mechanism
molecules to be measured bind to biological layer via receptors transducer surface creates electronic signal signal conditioner creates an output
85
stationary phases
chromatography paper (made of cellulose) or thin-layer chromatography plate (sheet of plastic coated with thin layer of silica gel or aluminium hydroxide)
86
mobile phase
solvent that carries biological molecules | flows through and across stationary phase
87
how chromatography works
solvent moves up stationary phase, carrying soluble pigments with it pigments move at different speeds (due to polarity, size, solubility in solvent) more polar = stick to the stationary phase more = slowly and vice versa
88
relative distance (chromatography) formula
``` Rf = x/y Rf = relative distance travelled by a pigment x = distance between CENTRE of spot of pigment and pencil line y = distance between solvent and pencil line ```
89
how to spot colourless molecules in chromatography with UV light
TLC plates have chemical that fluoresces under UV light, colourless pigment will mask plate from UV light so no glowing
90
how to spot colourless molecules in chromatography with ninhydrin
allow plate to dry spray with ninhydrin binds to amino acids, become visible as brown or purple spots
91
how to spot colourless molecules in chromatography with iodine
allow plate to dry place in enclosed space with few iodine crystals gas formed from iodine binds to molecules in each spot
92
uses of chromatography
monitor progress of reactions (as it is quick) | analyse for illegal drugs in urine of athletes, purity of components of drugs, contaminants in food
93
reducing sugar disaccharides
lactose maltose cellobiose

A-Level Biology (24 decks)

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