B1 Biological Molecules Flashcards
(114 cards)
1
Q
Define a monomer
A
Smaller units which can create larger molecules
2
Q
Define a polymer
A
Made from lots of monomers bonded together
3
Q
Examples of monomers
A
Glucose
Amino acid
Nucleotide
4
Q
Examples of polymers
A
Starch
Cellulose
Glycogen
Protein
DNA
RNA
5
Q
What do carbohydrates contain
A
C
H
O
6
Q
What are the 3 types of carbohydrates
A
Monosaccharides (monomers)
Disaccharides (diners)
Polysaccharides (polymers)
7
Q
What are 3 examples of monosaccharides
A
Glucose
Fructose
Galactose
8
Q
What are 3 examples of disaccharides
A
Sucrose
Maltose
Lactose
9
Q
What are 3 examples of polysaccharides
A
Starch
Cellulose
Glycogen
10
Q
Define isomer
A
Same molecular formula but different structure
11
Q
What’s molecular formula of glucose
A
C6H12O6
12
Q
What are disaccharides made of
A
2 monosaccharides
13
Q
What is Bond in disaccharides
A
Glycosidic bond joining 2 monosaccharides together
14
Q
Disaccharides are formed via which reaction
A
Condensation recation
15
Q
What are the 3 disaccharides word equations
A
Glucose + glucose —> maltose + water
Glucose + galactose —> lactose + water
Glucose + fructose —> sucrose + water
16
Q
Define condensation reaction
A
Joining 2 molecules together by removing water
17
Q
Define hydrolysis reaction
A
Splitting apart molecules through addition of water
18
Q
How are polysaccharides formed
A
by condensation reactions between many glucose monomers
19
Q
Where’s starch found
A
Plant cells (e.g. in chloroplast)
(Can be found in starch grains inside plant cells)
20
Q
Where’s cellulose found
A
Plants - cell wall
21
Q
Where’s glycogen found
A
In animals - mainly in muscle + liver cells
22
Q
What’s function of starch
A
insoluble store of glucose
23
Q
What’s function of cellulose
A
Provide Structural strength for cell wall
24
Q
What’s function of glycogen
A
Insoluble Store of glucose
25
What are monomers in starch
Alpha glucose
26
What are monomers in cellulose
Beta glucose
27
What are Monomers in glycogen
Alpha glucose
28
What is bond between monomers in starch
1-4 glycosidic bonds in amylose
1-4 & 1-6 in amylopectin
29
What is bond between monomers in cellulose
1-4 glycosidic bonds
30
What is bond between monomers in glycogen
1-4 & 1-6 glycosidic bonds
31
What is structure of starch
Made of 2 polymers
Amylose - unbranched helix
Amylopectin - branched molecule
32
What is structure of cellulose
Polymer forms long, straight chains.
Chains held parallel by many HBs to form fibrils
33
What is structure of glycogen
Highly branched molecule
1-6 GB creates branch, even more 1-6 GBs branch of this branch to create highly branched polymer
34
Explain how structure leads to function in starch
Helix shape of amylose compact to fit lots of glucose in small space.
Amylopectin branched structure - multiple exposed ends of molecule, increases SA - rapid hydrolysis back to glucose.
insoluble - wont affect water potential
35
Explain how structure leads to function in cellulose
Many HBs - collective strength (HBs weak individually but collectively strong)
Insoluble - wont affect water potential
36
Explain how structure leads to function In glycogen
Branched - increases SA for rapid hydrolysis back to glucose
Insoluble - wont affect water potential
compact easily, store lots of glucose in small space
- advantage = animals need to move, movement requires energy, glucose needed in respiration to release that energy, so animals have more branched store of glucose compared to plants.
37
What is a phospholipid made up of
1 glycerol
2 fatty acids
1 phosphate group
38
How are triglycerides formed
3 condensation reaction between 1 glycerol and 3 fatty acids
Produces 3H2O as bi products
Forms 3 ester bonds
39
Define saturated fatty acid
hydrocarbon chain has only single bonds between Cs
40
Define unsaturated fatty acid
hydrocarbon chain consists of at least 1 double bond between Cs
41
What are properties of triglycerides
1) energy storage; large ratio of energy-storing C-HBs:number of Cs, a lot of energy stored in molecule
2)high ratio of H:O atoms, act as metabolic H2O source. Can release H2O if oxidised. essential for desert animals , e.g. camels
3) don’t affect water potential + osmosis; they’re large + hydrophobic - insoluble to H2O.
4) relatively low mass, therefore a lot can be stored without increasing mass + preventing movement.
42
Emulsion test for lipids
Dissolve sample in ethanol
Add distilled water
White emulsion appears
43
How are phospholipids formed
2 fatty acids bond to glycerol via 2 condensation reactions
Form 2 ester bonds
44
What are properties of phospholipid
Hydrophilic head - attract water its charged - phosphate group charged, repels other fats.
Hydrophobic tail - Fatty acid chains not charged, repel water, mix with fats.
45
Properties of phospholipids (bilayer)
2 charged regions, they’re polar.
In H2O, positioned so heads exposed to water and tails aren’t.
Forms phospholipid bilayer membrane, which makes up plasma membrane around cells.
46
Describe how the amino acids are joined together to form a dipeptide
Via condensation reaction
H2O removed
Peptide bond forms between OH of carboxyl and H of amine group
47
What is the name of bond in proteins
Peptide bond
48
What are proteins
Polymers made up of monomer amino acids
49
Describe primary structure of a protein
order (sequence) of amino acids in polypeptide chain
this is a polymer
50
Describe the secondary protein structure
sequence of amino acids causes parts of protein molecule to bend into a-helix shapes or fold into B-pleated sheets
HBs hold secondary structure
51
Where are the HBs located in the secondary structure of a protein
between C=O groups of carboxyl group of 1 amino acid
and H in amine group of another amino acid
52
Describe tertiary structure of protein
Further folding of secondary structure
form unique 3d shape
Held in place by ionic, hydrogen and disulphide bonds
53
Describe location of bonds in tertiary structure of protein
Ionic & disulphide bonds form between R groups of diff AAs.
Disulphide bonds only sometimes occur, as there must be sulfur in R groups for this bond to occur.
(S- - -S)
54
Describe quaternary structure of protein
protein made up of more than one polypeptide chain
E.g. haemoglobin is made of 4 polypeptide chains
55
What happens to the protein structure when a protein is denatured
Protein denatured
bonds holding tertiary & secondary structure in shape break (ionic and hydrogen bonds break)
Unique 3d shape lost
(e.g. enzymes lose their unique active site shape)
56
Conditions that denature protein
Too high temp (too much kinetic energy)
Too high/low pH (too many H+ or -OH)
57
Describe the importance of primary structure
AA in sequence is diff then it cause ionic/hydrogen/disulfide bonds to form in diff location
results in diff 3d shape
58
impact of change in protein structure on enzymes
have diff shaped active site (will be non-functioning)
Carrier proteins will have diff shaped binding site (molecules no longer complementary and can’t be transported across membranes)
59
What might cause a change in AA sequence
Mutations
If there’s a change in DNA sequence, it might then code for diff AA
therefore primary structure changes
60
Test for starch
Add iodine
orange —> blue/black
61
Test for reducing sugar
Add Benedict’s reagent + heat
blue —> green, yellow, orange or brick red
(more red, higher conc of reducing sugar)
62
Why does the colour change occur at the top of the solution first in the reducing sugar test?
Convection currents
Hotter particles in solution rising
hottest point in solution at top
molecules have most kinetic energy, more successful collisions + faster reaction rate
So colour change 1st occurs at the top
63
Test for non-reducing sugars
Following neg Benedict’s test (reagent remains blue)
Add acid + boil (acid hydrolysis)
Cool solution + then add alkali to neutralise
Add Benedict’s reagent + heat
blue —> green, yellow, orange or brick red
64
What are 3 types of carbohydrates
Starch
Reducing sugars
Non-reducing sugars
65
Examples of reducing sugars
Glucose
Fructose
Galactose
Lactose
Maltose
66
Example of non-reducing sugar
Sucrose
67
What are reducing sugars
Sugars that can reduce copper sulphate (blue) in Benedict’s reagent to copper oxide (brick red)
68
Why is sucrose a non-reducing sugar
Reducing group involved in glycosidic bond in sucrose
therefore sucrose cannot reduce copper sulphate to copper oxide
69
What happens to sucrose when its hydrolysed
When sucrose hydrolysed (boiling with acid)
GB is broken - reducing group becomes exposed
Pos results achieved with Benedict’s reagent following hydrolysis
70
Test for proteins
Add Biuret
blue —> purple
71
What are enzymes
Tertiary structure proteins
Catalyse reactions
72
What part of enzyme attaches to substrate
Enzymes are large molecules
Only small part of enzyme attaches to substrate to catalyse reaction
known as ‘active site’
73
Why can enzymes only attach to substrates that are complementary in shape
Active site is specific & unique in shape due to specific folding and bonding in tertiary structure of protein.
74
What are the 2 models of enzyme action
Lock & key model
Induced fit model
75
Define activation energy
All reactions require certain amount of energy before they occur
76
How do enzymes speed up a reaction
Enzymes attach to substrate
Can lower activation energy needed for reaction to occur
so speed up reaction
77
Describe the lock and key model
Enzyme = lock and substrate = key that fits into it due to being complementary in shape
Model suggests : active site is fixed shape + due to random collisions substrate can collide & attach to enzyme - forms an enzyme-substrate complex (E-SC)
When E-SC , charged groups in active site are thought to distort the substrate & so lower Ea
Products then released & active site is empty and ready to be reused
78
Describe induced fit model (accepted model for how enzymes function)
Enzyme = glove and substrate = hand
Empty glove isn’t exactly complementary in shape to a hand, but when hand enters it enables glove to mould around hand and become completely complementary.
Induced fit is where active site’s induced/slightly changes shape to mould around substrate.
When E-SC occurs, due to enzyme moulding around substrate - puts strain on bonds + so lowers Ea. Products are then removed, active sire returns to original shape.
79
Factors that affect rate of enzyme controlled reactions
Temp
pH
Substrate conc
Enzyme conc
Inhibitors
80
Temp affect on enzymes
Temp too low, not enough Ek for successful collisions between enzymes and substrate
Temp too high, enzymes denature, active site changes shape, E-SC cannot form
81
pH effect on enzymes
Too high/too low pH, it’ll interfere with charges in AAs in active site.
This can break bonds holding tertiary structure in place & so active site changes shape.
So enzyme denatures & fewer E-SC form
Diff enzymes have a diff optimal pH
82
Substrate & enzyme conc effect on enzymes
Insufficient substrate, reaction will be slower as there’ll be fewer collisions between enzymes & substrate.
Insufficient enzymes, active site will become saturated with substrate & unable to work any faster.
83
What are Competitive inhibitors
Same shape as substrate & bind to active site,
prevents substrate binding & reaction occurring.
add more substrate it will out-compete inhibitor, knocking them out of active site.
84
Non-competitive inhibitors
Bind to enzyme away from active site, allosteric site
causes active site change shape, substrate no longer bind, regardless of how much substrate added.
85
Describe structure and function of globular proteins
Spherical & compact
Hydrophilic R groups face outwards & hydrophobic
R groups face inwards = usually water-soluble
Involved in metabolic processes e.g. enzymes & haemoglobin.
86
Describe the structure and function of fibrous proteins.
Can form long chains or fibres
insoluble in water
Useful for structure and support e.g. collagen in skin.
87
Outline how chromatography could be used to identify the amino acids in a mixture.
Use capillary tube to spot mixture onto pencil origin line & place chromatography paper in solvent.
Allow solvent to run until it almost touches other end of paper. Amino acids move different distances based on relative attraction to paper & solubility in solvent.
Use revealing agent or UV light to see spots.
Calculate R, values & match to database.
88
Contrast competitive and non-competitive inhibitors.
Competitive inhibitors
- similar shape to substrate = bind to active site
- don’t stop reaction; E-SC forms when inhibitor is released
- increasing substrate conc decreases their effect
Non-competitive inhibitor
- bind at allosteric binding site
- may permanently stop reaction; triggers active site to change shape
- increasing substrate conc has no impact on their effect
89
Outline how to calculate rate of reaction from a graph.
gradient of line or tangent to a point.
initial rate: draw tangent at t = 0.
90
Outline how to calculate reaction rate from raw data
Change in conc of product or reactant/time
91
Why is it advantageous to calculate initial rate?
Represents maximum rate of reaction before concentration of reactants decreases & 'end product inhibition'.
92
Similarities of phospholipids and triglycerides.
Both have:
glycerol backbone
may be attached to mixture of saturated, monounsaturated & polyunsaturated fatty acids
contain elements C, Н, О
formed by condensation reactions
93
Contrast phospholipids and triglycerides.
Phospholipids
- 2 fatty acids & 1 phosphate group attached
- Hydrophilic head & hydrophobic tail
- Used primarily in membrane formation
triglycerides:
- 3 fatty acids attached
- Entire molecule is hydrophobic
- Used primarily as a storage molecule (oxidation releases energy)
94
Are phospholipids and triglycerides polymers?
No; they are not made from a small repeating unit. They are macromolecules.
95
Describe 2 types of secondary protein structure
Alpha helix:
- all N-H bonds on same side of protein chain
-spiral shape
- HBs parallel to helical axis
Beta pleated sheet:
- N-H & C=O groups alternate from 1 side to other
96
Define tertiary protein structure + name bonds in it
3D Structure formed by further folding of polypeptide
- disulfide bridges
- ionic bonds
- hydrogen bonds
97
Define quaternary protein structure
Functional proteins may consist of more than 1 polypeptide
Precise 3D structure held together by same types of bond as tertiary structure
May involve addition of prosthetic groups e.g. metal ions or phosphate groups
98
What are enzymes
Biological catalysts for intra & extracellular reactions
Specific tertiary structure determines shape of active site, complementary to a specific substrate
Formation of enzyme-substrate (ES) complexes lowers Ea of metabolic reactions
99
How have models of enzyme action changed
Initially lock & key model: rigid shape of active site complementary to only 1 substrate
Currently induced fit model : also explains why binding at allosteric sites can change shape of active site
100
Name 5 factors that affect enzyme-controlled reactions rates
Enzyme conc
Substrate conc
Conc of inhibitors
pH
Temp
101
How does substrate conc affect reaction rate
Given that enzyme conc is fixed, rate increases proportionally to substrate conc
Rate levels off when maximum number of ES complexes form at any given time
102
How does enzyme conc affect reaction rate
Given that substrate is in excess, rate increases proportionally to enzyme conc
Rate levels off when maximum number of ES complexes form at any given time.
103
How does temp affect reaction rate
Rate increases as Ek increases & peaks at optimum temp
Above optimum, ionic & HBs in tertiary structure break = active site no longer complementary to substrate (denaturation)
104
How does pH affect reaction rate
Enzymes have a narrow optimum pH range
Outside range, H+/OH- interact with HBs & ionic bonds in tertiary structure = denaturation
105
Contrast competitive & non-competitive inhibitors
Competitive =
- similar shape to substrate = bind to active site
- don’t atop reaction; ES complexes forms when inhibitor is released
- increasing substrate conc decreases their effect
Non-competitive =
- bind at allosteric binding site
- may permanently stop reaction; triggers active site to change shape
- increasing substrate conc has no impact on their effect
106
Name 3 hexose monosaccharides and their molecular formula
Glucose
Fructose
Galactose
All have molecular formula = C6H12O6
107
What are the molecular formula of maltose sucrose and lactose
All have molecular formula C12 H22 O11
108
Describe structure & functions of starch
Storage polymer of a-glucose in plant cells
. Insoluble = no osmotic effect on cells
. Large = doesn’t diffuse out of cells
Made from amylose:
> 1,4-GB
> Helix with intermolecular HBs = compact
And amylopectin:
> 1,4 & 1,6 GBs
> branched = many terminal ends for hydrolysis into glucose
109
Describe structure & functions of glycogen
Main storage polymer of a-glucose in animal cells (but also found in plant cells)
> 1,4 & 1,6 GBs
> branched = many terminal ends for hydrolysis
> insoluble = no osmotic effect & doesn’t diffuse out of cells
> compact
110
Describe structure & functions of cellulose
Polymer of B-glucose gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)
> 1,4 GBs
> straight-chain, unbranded molecule
> alternate glucose molecules are rotated 180*
> HB crosslinks between parallel strands form microfibrils = high tensile strength
111
Describe test for starch
1. Add iodine
2. Pos result = colour change from orange to blue-black
112
Outline how colorimetry could be used to give qualitative results for presence of sugars and starch
1. Make standard solutions with known concs.
Record absorbance or % transmission values.
2. Plot calibration curve: absorbance or % transmission (y-axis), conc (x-axis)
3. Record absorbance or % transmission values of unknown samples. Use calibration curve to read off conc
113
Contrast saturated & unsaturated fatty acids
Saturated
- contain only single bonds
- straight chain molecules have many contact points
- higher melting point = solid at room temp
- found in animal fats
Unsaturated
- contains C=C
- ‘kinked’ molecules have fewer contact points
- lower MP = (l) at room temp
- found in plant oils
114
Relate structure of triglycerides to their functions
High energy:mass ratio = high calorific value from oxidation (energy storage)
Insoluble hydrocarbon chain = no effect on water potential of cells & used for water proofing
Slow conductor of heat = thermal insulation e.g. adipose tissue
Less dense than water = buoyancy of aquatic animals
