1. Biological Molecules Flashcards
(94 cards)
1
Q
define monomer
give example
A
smaller units that join together to create larger molecules
e.g monosaccharides (glucose, fructose, galactose), nucleotides, amino acids
2
Q
define polymer
give example
A
molecules formed when many monomers joined together
e.g DNA/RNA, proteins, polysaccharides
3
Q
what happens in a condensation reaction
A
a chemical bond between 2 molecules and a molecule of water is produced
4
Q
what happens in a hydrolysis reaction
A
a water molecule is used to break 2 molecules
5
Q
what are 3 hexose monosaccharides
A
glucose, fructose, galactose
6
Q
what formula do all hexose monosaccharides have
A
C6H12O6
7
Q
what is a monosaccharide
A
the monomers from which larger carbohydrates are made from
8
Q
what is the bond formed when two monosaccharides react
A
(1/4 or 1/6) glycosidic bond
9
Q
how are disaccharides formed
A
condensation reaction forms glycosidic bonds between 2 monosaccharides
10
Q
what formula does maltose, sucrose and lactose all have
A
C12H22O11
11
Q
what forms maltose
A
2 alpha glucose
12
Q
what forms sucrose
A
glucose and fructose
13
Q
what forms lactose
A
glucose and galactose
14
Q
what is a covalent bond
A
a strong chemical bond where 2 atoms share a pair of electrons
15
Q
what is an ionic bond
A
a moderate chemical bond from the electrostatic attraction between oppositely charged ions
16
Q
what is a hydrogen bond
A
a weak chemical bond between the positive charge on a hydrogen atom and the negative charge on the atom of an adjacent molecule.
17
Q
what is a glycosidic bond
A
a covalent bond between a carbohydrate molecule and a hydroxyl group on another molecule, resulting from a condensation reaction
18
Q
what is a peptide bond
A
a covalent bond between two amino acids, resulting from a condensation reaction.
19
Q
what is a phosphodiester bond
A
a covalent bond between two nucleotides via a condensation reaction
20
Q
what is a dipolar molecule
A
a molecule with equal and opposite charges at each end
21
Q
structure of an alpha glucose
A
OH alpha below
22
Q
structure of beta glucose
A
OH beta above
23
Q
what is glucose
A
a monosaccharide with two isomers: alpha glucose and beta glucose.
24
Q
what is a carbohydrate
A
a molecule formed of one or more monosaccharides
25
what is a polysaccharide
a molecule formed by the condensation of many monosaccharide units
26
what is starch
a polysaccharide formed by condensation of alpha glucose in plants
27
what are the 2 types of starch
amylose and amylopectin
28
features of amylose
1,4 glycosidic bonds
helix structure with intermolecular H bonds meaning its compact
29
features of amylopectin
1,4 and 1,6 glycosidic bonds
branched structure meaning many terminal/free ends for hydrolysis into glucose
30
features of starch
-insoluble due to no osmotic effect on cells
-large so doesn't diffuse out of the cell
-compact
-some plants store starch as fruit
31
what is glycogen
a polysaccharide formed by condensation of alpha glucose , containing 1, 4 - and 1,6- glycosidic bonds in mainly animals and bacteria
32
features of glycogen
-1,4 and 1,6 glycosidic bonds
-highly branched structure meaning many -terminal/free ends for hydrolysis into glucose
-insoluble so no osmotic effect and doesn't diffuse out of cells
-compact
33
what is cellulose
a polysaccharide formed by condensation of beta glucose , containing only 1 , 4 -glycosidic bonds
34
features of cellulose
-polymer of beta glucose so gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)
-1,4 glycosidic bonds
-straight chain, unbranched molecule
-alternate glucose molecules are rated 180 degrees
-H bonds crosslink between parallel strands from microfibrils meaning makes cell wall strong
35
benedicts test for reducing sugar
-add equal volume of benedicts reagent to sample
-heat mixture
-positive result goes blue to orange/brick red
36
benedicts test for non reducing sugar
-negative result- benedict reagent remains blue
-hydrolyse non reducing sugar by adding HCl and and heat in water bath
-neutralise the mixture using sodium carbonate solution
-test with benedicts test again to observe colour change
37
concentration of benedicts test from lowest to highest
blue (no sugar present), purple, green, yellow, orange, red
38
how to make benedicts test quantitative
filter precipitate at the bottom of the tube and measure the mass to give indication of the quantity of sugars
39
why is benedicts test semi quantitative
by observing the colour change on a scale from blue to red it's possible to estimate the concentration of the reducing sugar.
40
test for starch
-add iodine solution to sample
-positive result is blue to black
41
how could colorimetry be used to give quantitative results for presence of sugars and starch
-make standard solution with known concentrations and record abundance
-plot calibration curve with absorbance on y axis and concentration on x axis
-record abundance of unknown samples and use calibration curve to read off concentration
42
test for lipids
-dissolve sample solids in ethanol and shake
-then add equal volume of water and shake
-positive result is milky white emulsion
43
what is a triglyceride
A molecule formed by condensation, with
ester bonds joining three fatty acids to one molecule of glycerol
44
what are the 2 types of fatty acids
the R group of fatty acid can be saturated or unsaturated
45
features of saturated fatty acids
-contains only one C bond
-straight chin molecule so many contact points
-higher melting points means solid at room temp
-found in animal fats
46
features of unsaturated fatty acids
-contain double carbon bonds
-kinked molecule so fewer contact points
-lower melting points means liquid at room temp
-found in plant oils
47
features of fatty acid
has carboxylic acid at start joining to a hydrocarbon chain, more C-H is more energy storage
48
what are the 2 types of lipids
phospholipids and triglycerides
49
functions and structures of triglycerides
-high energy to mass ratio so increase in energy storage
-insoluble hydrocarbon chain providing waterproofing
-slow conductor of heat for thermal insulation
-source of water
50
what is a phospholipid
A molecule formed by condensation reaction with two fatty acids and a phosphate group bonded to one molecule of glycerol.
51
where is the phosphodiester bond in a phospholipid
between phosphahte group and glycerol
52
where is the ester bond in a phospholipid
between glycerol and 2 fatty acids
53
what shape does a phospholipid have
kinked
54
what is the key feature of a fatty acid and phospahte molecule of a phospholipid
-fatty acid repels water so has a hydrophobic tail
-phosphate molecules attracts water so has a hydrophilic head
55
what type of molecule is a phospholipid
polar molecule
56
what is the main function of a phospholipid
main component of cell membrae
57
importance of phospholipid bilayer
contributes to flexibility and transfer of lipids meaning its soluble, also its a barrier
58
what is formed when a phospholipid combines with a carbohydrate and why is it important
glycolipid formed and important for cell recognition
59
similarities of phospholipids and triglycerides
-both have glycerol backbone
-both attached to mixture of saturated, unsaturated and polysaturated fatty acids
-both formed by condensation reactions
60
differences in phospholipids and triglycerides
phospholipids:
-2 fatty acids and 1 phosphate group
-hydrophilic head and hydrophobic tail
-used in cell membrane formation
triglycerides:
-3 fatty acids
-entire molecule is hydrophobic
-used for storage for oxidation to release energy
61
why is water a polar molecule
O is more electronegative than H so, attracts the electron density in covalent bond ore strongly. Forms O partially negative and H partially positive
62
5 properties of water
Due to polarity and intermolecular H bonds:
-a metabolite for chemical reactions in the body like respiration
-a solvent so metabolic reactions can occur
-high specific heat capacity so buffers change in temperature
-high latent heat of vaporisation so provides cooling effect
-cohesion between water molecules so supports columns of water in plants
63
why is water important for living organisms
-solvent for polar molecules during metabolic reactions
-cohesion tension of water molecules in transpiration stream
64
where are inorganic ions found
found in cytoplasm and extracellular fluids in high or low concentrations
65
role of H+ ions in body
-high concentration of H+ ions means very acidic so low pH
-H+ ions interact with H bonds and ionic bonds in tertiary structure of proteins which can cause them to denature
66
general structure of an amino acid
R group, amine group and COOH group
67
test for proteins
-add equal volume of food sample to biuret regent in test tube
-shake and leave for 5 mins
-positive result goes from blue to purple
68
how many amino acids are there and how do they differ
20
different R group
69
how do dipeptide and polypeptide bonds formed
a condensation reaction between 2 amino acids (di) or 3 amino or more amino acids (poly) by the removal of water
70
how many level of protein structures are there
4
71
what is the primary structure
-specific sequence of amino acids in polypeptide chain
-amino acid arranged in particular order determined by DNA
72
what is the secondary structure
-polypeptide folds due to H bonds forming within
-H bonding doesn't involve R group but forms between O and H atoms on polypeptide backbone
-common structures are alpha helices and beta pleated sheets (3D structure)
73
what is the tertiary structure
-further folding into 3D structure caused by bonding of atoms between R groups of diff amino acids
-ionic bonding, hydrogen bonding, disulfide bonding
-forms functional (e.g enzyme) or structral (e.g keratin) proteins
74
what is the quaternary structure
-made up of more than 1 polypeptide chains (subunit)
-some are conjugated protein which is a prosthetic group added to it
75
what are enzymes
a biological catalyst that increases rate of reactions and the formation of e-s complexes lowers activation energy. specific tertiary structure determines shape of active site, complementary to a specific substrate
76
what is the induced fit model
shapes of the enzyme's active site and its substrate are not exactly complementary, but when the substrate enters the active site, a conformational change enables e-s complexes to form, puts strain on substrate bonds lowering ae
77
5 factors that affect enzymes
pH
Temp
Enzymes conc
Substrate conc
Conc of inhibitors
78
how have the models of enzymes changed
Initially lock and key model: rigid shape of active site, complementary to only 1 substrate
Current induced fit model: explains why binding at allosteric sites can change active site
79
how do E-S complexes form
Substrate held in place by temporary bonds
Bonds form between amino acids of active site and groups on substrate
80
how does temp affect enzymes activity
Increase temp increases KE As temp increase H bonds can break
Enzymes and substrates collide more often Shape of enzyme and active site changes
Rate of reaction increases Substrate fits less easily at first then denature
81
how does pH affect enzymes
Changes in pH can alter changes on amino acids of active site
Arrangement of active site is partly determined by H bonds between amine and carboxylate group
Bonds break leading to a distortion in shape of active site so substrate can’t attach as no longer complementary
If bonds in tertiary structure break enzyme is denatured
82
how does substrate concentration affect enzymes
Increasing substrate conc will increase rate of reaction until maximum rate of reaction
83
how does enzyme con affect enzymes
Increasing enzyme conc will increase rate of reaction as long as there’s excess substrates
84
Competitive inhibitors features
Similar shape to substrate so binds to active site
Doesn’t stop reaction as only temporary, ES complexes form when inhibitor is released
Increasing substrate conc decreases their effect
85
Non competitive inhibitors features
Binds at allosteric site
Can permanently stop reaction as triggers active site to change shape
Increasing substrate conc has no impact on their effect
86
what is the pentose sugar in DNA and RNA
DNA: deoxyribose
RNA: ribose
87
what is the structure of a nucleotide
phosphate group
pentose sugar
nitrogenous base
88
what is the role of DNA in living cells
DNA replication
Holds genetic info
Base sequence of genes codes for functional RNA and amino acids and sequences of polypeptides
89
how do polynucleotides form
Condensation reactions between nucleotides form phosphodiester bonds (sugar phosphate backbone)
90
structure of DNA
double helix of 2 polynucleotide strands
H bonds between complementary purine and pyrimidine base pairs on opposite strands
Adenine + Thymine
Guanine + Cytosine
91
Which bases are purine and which bases are pyrimidine
A & G = 2 ring purine bases
T & C & U = 1 ring pyrimidine bases
92
what are the complementary base pairs in DNA
2 H bonds between adenine and thymine
3 H bonds between guanine and cytosine
93
complementary base pairs in RNA
2 H bonds between adenine and uracil
3 H bonds between guanine and cytosine
94
relate structure of DNA to its functions
