A-level Biology > B1 Biological Molecules > Flashcards

B1 Biological Molecules Flashcards

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1
Q

Define a monomer

A

Smaller units which can create larger molecules

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2
Q

Define a polymer

A

Made from lots of monomers bonded together

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3
Q

Examples of monomers

A

Glucose
Amino acid
Nucleotide

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4
Q

Examples of polymers

A

Starch
Cellulose
Glycogen
Protein
DNA
RNA

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5
Q

What do carbohydrates contain

A

C
H
O

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6
Q

What are the 3 types of carbohydrates

A

Monosaccharides (monomers)

Disaccharides (diners)

Polysaccharides (polymers)

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7
Q

What are 3 examples of monosaccharides

A

Glucose
Fructose
Galactose

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8
Q

What are 3 examples of disaccharides

A

Sucrose
Maltose
Lactose

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9
Q

What are 3 examples of polysaccharides

A

Starch
Cellulose
Glycogen

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10
Q

Define isomer

A

Same molecular formula but different structure

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11
Q

What’s molecular formula of glucose

A

C6H12O6

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12
Q

What are disaccharides made of

A

2 monosaccharides

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13
Q

What is Bond in disaccharides

A

Glycosidic bond joining 2 monosaccharides together

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14
Q

Disaccharides are formed via which reaction

A

Condensation recation

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15
Q

What are the 3 disaccharides word equations

A

Glucose + glucose —> maltose + water

Glucose + galactose —> lactose + water

Glucose + fructose —> sucrose + water

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16
Q

Define condensation reaction

A

Joining 2 molecules together by removing water

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17
Q

Define hydrolysis reaction

A

Splitting apart molecules through addition of water

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18
Q

How are polysaccharides formed

A

by condensation reactions between many glucose monomers

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19
Q

Where’s starch found

A

Plant cells (e.g. in chloroplast)

(Can be found in starch grains inside plant cells)

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20
Q

Where’s cellulose found

A

Plants - cell wall

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21
Q

Where’s glycogen found

A

In animals - mainly in muscle + liver cells

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22
Q

What’s function of starch

A

insoluble store of glucose

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23
Q

What’s function of cellulose

A

Provide Structural strength for cell wall

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24
Q

What’s function of glycogen

A

Insoluble Store of glucose

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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. 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.
45
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
46
What is the name of bond in proteins
Peptide bond
47
What are proteins
Polymers made up of monomer amino acids
48
Describe primary structure of a protein
order (sequence) of amino acids in polypeptide chain this is a polymer
49
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
50
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
51
Describe tertiary structure of protein
Further folding of secondary structure form unique 3d shape Held in place by ionic, hydrogen and disulphide bonds
52
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)
53
Describe quaternary structure of protein
protein made up of more than one polypeptide chain E.g. haemoglobin is made of 4 polypeptide chains
54
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)
55
Conditions that denature protein
Too high temp (too much kinetic energy) Too high/low pH (too many H+ or -OH)
56
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
57
impact of change in protein structure on enzymes
diff shaped AS (will be non-functioning) Carrier proteins will have diff shaped binding site (molecules no longer complementary and can’t be transported across membranes)
58
What might cause a change in AA sequence
Mutations change in DNA sequence, might then code for diff AA primary structure changes
59
Test for starch
Add iodine orange —> blue/black
60
Test for reducing sugar
Add Benedict’s reagent + heat blue —> green, yellow, orange or brick red (more red, higher conc of reducing sugar)
61
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 At top molecules have most Ek, more successful collisions + faster reaction rate colour change 1st occurs at top
62
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
63
What are 3 types of carbohydrates
Starch Reducing sugars Non-reducing sugars
64
Examples of reducing sugars
Glucose Fructose Galactose Lactose Maltose
65
Example of non-reducing sugar
Sucrose
66
What are reducing sugars
Sugars that can reduce copper sulphate (blue) in Benedict’s reagent to copper oxide (brick red)
67
Why is sucrose a non-reducing sugar
Reducing group involved in glycosidic bond in sucrose therefore sucrose cannot reduce copper sulphate to copper oxide
68
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
69
Test for proteins
Add Biuret blue —> purple
70
What are enzymes
Tertiary structure proteins Catalyse reactions
71
What part of enzyme attaches to substrate
Enzymes are large molecules small part of enzyme attaches to substrate to catalyse reaction - AS
72
Why can enzymes only attach to substrates that are complementary in shape
AS specific & unique shape due to specific folding & bonding in tertiary structure of protein.
73
What are the 2 models of enzyme action
Lock & key model Induced fit model
74
Define activation energy
All reactions require certain amount of energy before they occur
75
How do enzymes speed up a reaction
Enzymes attach to substrate lower Ea needed for reaction to occur speeds up reaction
76
Describe the lock and key model
Enzyme = lock & substrate = key that fits into it due to being complementary in shape Model suggests : AS fixed shape + due to random collisions substrate can collide & attach to enzyme - forms (E-SC) When E-SC , charged groups in AS are thought to distort substrate & lower Ea Products released & AS is empty and ready to be reused
77
Describe induced fit model (accepted model for how enzymes function)
Enzyme = glove and substrate = hand Empty glove isn’t exactly complementary in shape to hand, hand enters it enables glove to mould around hand & become completely complementary. Induced fit is where As 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 then removed, AS returns to original shape.
78
Factors that affect rate of enzyme controlled reactions
Temp pH Substrate conc Enzyme conc Inhibitors
79
Temp affect on enzymes
Temp too low, not enough Ek for successful collisions between enzymes and substrate Temp too high, enzymes denature, AS changes shape, E-SC cannot form
80
pH effect on enzymes
Too high/low pH, interfere with charges in AAs in AS can break bonds holding tertiary structure in place & so AS changes shape. enzyme denatures & fewer E-SC form Diff enzymes have diff optimal pH
81
Substrate & enzyme conc effect on enzymes
Insufficient substrate, reaction be slower as fewer collisions between enzymes & substrate. Insufficient enzymes, AS will become saturated with substrate & unable to work any faster.
82
What are Competitive inhibitors
Same shape as substrate & bind to AS prevents substrate binding & reaction occurring. add more substrate it will out-compete inhibitor, knocking them out of AS
83
Non-competitive inhibitors
Bind to enzyme away from AS - allosteric site causes AS change shape, substrate no longer bind, regardless of how much substrate added.
84
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.
85
Describe 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.
86
Outline how chromatography could be used to identify AAs in mixture.
Use capillary tube to spot mixture onto pencil origin line & place chromatography paper in solvent. Allow solvent to run until almost touches other end of paper. AAs move diff distances based on relative attraction to paper & solubility in solvent. Use revealing agent or UV light to see spots. Calc R, values & match to database.
87
Contrast competitive and non-competitive inhibitors.
Competitive inhibitors - similar shape to substrate = bind to AS - don’t stop reaction; E-SC forms when inhibitor released - increasing substrate conc decreases effect Non-competitive inhibitor - bind at allosteric binding site - may permanently stop reaction; triggers AS to change shape - increasing substrate conc has no impact on effect
88
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.
89
Outline how to calculate reaction rate from raw data
Change in conc of product or reactant/time
90
Why is it advantageous to calculate initial rate?
Represents maximum rate of reaction before concentration of reactants decreases & 'end product inhibition'.
91
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
92
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)
93
Are phospholipids and triglycerides polymers?
No; they are not made from a small repeating unit. They are macromolecules.
94
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
95
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
96
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
97
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
98
Name 5 factors that affect enzyme-controlled reactions rates
Enzyme conc Substrate conc Conc of inhibitors pH Temp
99
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
100
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.
101
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)
102
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
103
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
104
Name 3 hexose monosaccharides and their molecular formula
Glucose Fructose Galactose All have molecular formula = C6H12O6
105
What are the molecular formula of maltose sucrose and lactose
All have molecular formula C12 H22 O11
106
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
107
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
108
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
109
Describe test for starch
1. Add iodine 2. Pos result = colour change from orange to blue-black
110
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
111
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
112
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
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