biological molecules Flashcards
(169 cards)
1
Q
Monomers
A
Smaller / repeating molecules from which larger molecules / polymers are made.
2
Q
Polymers
A
Molecule made up of many identical / similar molecules / monomers.
3
Q
Condensation Reaction
A
2 molecules join together, forming a chemical bond, releasing a water molecule.
4
Q
Hydrolysis Reaction
A
2 molecules separated, breaking a chemical bond, using a water molecule.
5
Q
Polymers and Monomers Example
A
Monomer Polymer
Glucose. Starch
Amino acid. Protein
Nucleotides. DNA
6
Q
Monosaccharides
A
Monomers from which larger carbohydrates are made.
7
Q
Examples of Monosaccharides
A
Glucose, fructose, galactose.
8
Q
α-glucose Structure
A
Full structure with carbon atoms labelled; simplified structure as in the specification to be memorised for exam.
9
Q
Difference between α-glucose and β-glucose
A
OH group is below carbon 1 in α-glucose and above carbon 1 in β-glucose; they are isomers with the same molecular formula but differently arranged atoms.
10
Q
Disaccharides
A
Two monosaccharides joined together with a glycosidic bond.
11
Q
Formation of Disaccharides
A
Formed by a condensation reaction, releasing a water molecule.
12
Q
Common Disaccharides
A
Maltose (Glucose + glucose), Sucrose (Glucose + fructose), Lactose (Glucose + galactose).
13
Q
Polysaccharides
A
Large carbohydrates formed from many monosaccharides.
14
Q
structure of polysaccharides
A
Many monosaccharides joined together with glycosidic bonds.
15
Q
.
A
16
Q
Starch
A
Energy store in plant cells; polysaccharide of α-glucose.
17
Q
Amylose
A
1,4-glycosidic bonds → unbranched.
18
Q
Amylopectin
A
1,4- and 1,6-glycosidic bonds → branched.
19
Q
Glycogen
A
Energy store in animal cells; polysaccharide made of α-glucose.
20
Q
Glycogen Structure
A
1,4- and 1,6-glycosidic bonds → branched.
21
Q
Starch Helical Structure
A
Helical → compact for storage in cell (amylose).
22
Q
Starch Insolubility
A
Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane.
23
Q
Glycogen Branching
A
Branched → compact / fit more molecules in small area.
24
Q
Glycogen Hydrolysis
A
Branched → more ends for faster hydrolysis → release glucose for respiration to make ATP for energy release.
25
Cellulose Function
Provides strength and structural support to plant / algal cell walls.
26
Cellulose Structure
Polysaccharide of β-glucose; 1,4-glycosidic bond → straight, unbranched chains.
27
Cellulose Microfibrils
Chains linked in parallel by hydrogen bonds forming microfibrils.
28
Hydrogen Bonds in Cellulose
Many hydrogen bonds link parallel strands (crosslinks) to form microfibrils (strong fibres).
29
Reducing Sugars
Monosaccharides, maltose, lactose.
30
Test for Reducing Sugars
1. Add Benedict's solution (blue) to sample. 2. Heat in a boiling water bath. 3. Positive result = green / yellow / orange / red precipitate.
31
Non-reducing Sugars
Sucrose.
32
Test for Non-reducing Sugars
1. Do Benedict's test and stays blue / negative. 2. Heat in a boiling water bath with acid (to hydrolyse into reducing sugars). 3. Neutralise with alkali (eg. sodium bicarbonate). 4. Heat in a boiling water bath with Benedict's solution. 5. Positive result = green / yellow / orange / red precipitate.
33
Measuring Sugar Quantity
Carry out Benedict's test as above, then filter and dry precipitate; find mass / weight.
34
Alternative Method for Sugar Quantity
1. Make sugar solutions of known concentrations (eg. dilution series). 2. Heat a set volume of each sample with a set volume of Benedict's solution for same time. 3. Use colorimeter to measure absorbance (of light) of each known concentration. 4. Plot calibration curve - concentration on x axis, absorbance on y axis and draw line of best fit. 5. Repeat Benedict's test with unknown sample and measure absorbance. 6. Read off calibration curve to find concentration associated with unknown sample's absorbance.
35
Biochemical Test for Starch
1. Add iodine dissolved in potassium iodide (orange / brown) and shake / stir. 2. Positive result = blue-black.
36
Polysaccharides
Carbohydrates formed by long chains of monosaccharides.
37
Myofibrils
Structures found in muscle fibers that are completely different from microfibrils.
38
Microfibrils
Structures found in cellulose cell walls.
39
strength of Hydrogen bonds
Weak individually but strong in high numbers; many hydrogen bonds contribute to strength.
40
Benedict's solution
A reagent used to test for reducing sugars; the term volume should be used instead of amount.
41
Triglycerides
A type of lipid formed from one glycerol molecule and three fatty acids.
42
Phospholipids
A type of lipid where one fatty acid of a triglyceride is substituted by a phosphate-containing group.
43
Fatty acid structure
Composed of a variable R-group hydrocarbon chain and a carboxyl group (-COOH).
44
Saturated fatty acids
Fatty acids with no C=C double bonds in the hydrocarbon chain; all carbons are fully saturated with hydrogen.
45
Unsaturated fatty acids
Fatty acids with one or more C=C double bonds in the hydrocarbon chain, creating a bend or kink.
46
Condensation reaction
A chemical reaction that involves the removal of water molecules to form bonds.
47
Ester bonds
Bonds formed between glycerol and fatty acids during the formation of triglycerides.
48
Hydrophobic
Describes molecules that are insoluble in water and tend to clump together as droplets.
49
Hydrophilic
Describes molecules that are attracted to water.
50
Lipid test
Add ethanol, shake to dissolve lipids, then add water; a positive test results in a milky white emulsion.
51
Amino acid structure
Composed of a carboxyl group (COOH), a variable side chain (R), and an amine group (H2N).
52
Dipeptide
A molecule formed by two amino acids joined together.
53
Polypeptide
A molecule formed by many amino acids joined together.
54
Peptide bond
The bond formed between the carboxyl group of one amino acid and the amine group of another during a condensation reaction.
55
Common amino acids
There are 20 amino acids common in all organisms, differing only in their side group (R).
56
Primary structure of a protein
Sequence of amino acids in a polypeptide chain, joined by peptide bonds
57
Secondary structure of a protein
Folding (repeating patterns) of polypeptide chain eg. alpha helix / beta pleated sheets due to hydrogen bonding between amino acids
58
Tertiary structure of a protein
3D folding of polypeptide chain due to interactions between amino acid R groups (dependent on sequence of amino acids) forming hydrogen bonds, ionic bonds and disulfide bridges
59
Quaternary structure of a protein
More than one polypeptide chain formed by interactions between polypeptides (hydrogen bonds, ionic bonds, disulfide bridges)
60
Test for proteins
Add biuret reagent (sodium hydroxide + copper (II) sulphate). Positive result = purple / lilac colour (negative stays blue) →indicates presence of peptide bonds
61
Enzymes as biological catalysts
Each enzyme lowers activation energy of reaction it catalyses to speed up rate of reaction
62
Induced-fit model of enzyme action
Substrate binds to (not completely complementary) active site of enzyme, causing active site to change shape (slightly) so it is complementary to substrate, forming enzyme-substrate complex causing bonds in substrate to bend/distort and lowering activation energy
63
Lock and key model
Initially proposed model where active site is a fixed shape, complementary to one substrate (now outdated)
64
Specificity of enzymes
Specific tertiary structure determines shape of active site, dependent on sequence of amino acids (primary structure), allowing only a specific substrate to bind to active site
65
Effect of enzyme concentration on rate of reaction
As enzyme concentration increases, rate of reaction increases until a certain point where it levels off due to substrate concentration being the limiting factor
66
Limiting factor
All substrates in use
67
Substrate concentration effect
As substrate concentration increases, rate of reaction increases.
68
what happens to number of E-S complexes when the rate of reaction increases
More enzyme-substrate complexes form.
69
Enzyme concentration effect
At a certain point, rate of reaction stops increasing / levels off.
70
Temperature effect on reaction rate
As temperature increases up to optimum, rate of reaction increases.
71
Kinetic energy
More kinetic energy leads to more E-S complexes forming.
72
Temperature above optimum
As temperature increases above optimum, rate of reaction decreases.
73
Enzyme denaturation
Enzymes denature - tertiary structure and active site change shape.
74
Bond breakage affect on enymes
As hydrogen / ionic bonds break, active site no longer complementary.
75
pH effect on reaction rate
As pH increases / decreases above / below an optimum, rate of reaction decreases.
76
Competitive inhibitors effect on ror
As concentration of competitive inhibitor increases, rate of reaction decreases.
77
Competitive inhibitor action
Similar shape to substrate, competes for / binds to / blocks active site.
78
Effect of substrate concentration on inhibitors
Increasing substrate concentration reduces effect of inhibitors.
79
Non-competitive inhibitors
As concentration of non-competitive inhibitor increases, rate of reaction decreases.
80
Non-competitive inhibitor action
Binds to site other than the active site (allosteric site), changing enzyme tertiary structure.
81
Permanent change to active site
Increasing substrate concentration has no effect on rate of reaction as change to active site is permanent.
82
Variables affecting enzyme reaction rate
Enzyme concentration / volume, substrate concentration / volume, temperature of solution, pH of solution, inhibitor concentration.
83
Control variables
All others (except inhibitors) would be control variables and need to be kept constant.
84
Temperature control
Describe how temperature can be controlled.
85
Thermostatically controlled water bath
A device used to maintain a constant temperature for experiments.
86
Buffer solution
A solution that resists changes in pH when small amounts of acid or base are added.
87
pH meter
An electronic device used to measure the pH of a solution.
88
Control experiment
An experiment that uses denatured enzymes while keeping all other conditions the same.
89
Rate of reaction measurement
The time taken for a reaction to reach a set point, such as concentration or mass of substrate or product.
90
Rate of reaction formula
Rate of reaction = 1 / time; example units = s⁻¹.
91
Continuous data logger
A device that records data continuously throughout a reaction.
92
Graph plotting
Plotting time on the x-axis and the measured variable on the y-axis.
93
calculation and units of Initial rate of reaction
Calculated as change in y / change in x; example units = cm³ s⁻¹.
94
Safety risk with enzymes
Handling enzymes may cause an allergic reaction.
95
Colorimeter advantages
Not subjective and more accurate than visual comparison to color standards.
96
Denaturing an enzyme
Boiling or adding strong acid/alkali to stop a reaction.
97
Graph presentation
Independent variable on x-axis, rate of reaction on y-axis, with appropriate scale.
98
how does Reaction rate change throughut a reastion
Initial rate is highest as substrate concentration is not limiting; reaction slows as substrate is used up.
99
Functions of DNA
Holds genetic information which codes for polypeptides (proteins).
100
Functions of RNA
Transfers genetic information from DNA to ribosomes.
101
Ribosome composition
Made from RNA and proteins.
102
DNA nucleotide
Contains deoxyribose sugar and can have thymine as a base.
103
RNA nucleotide
Contains ribose sugar and can have uracil as a base.
104
Polynucleotide formation
Nucleotides join through condensation reactions forming phosphodiester bonds.
105
DNA simplicity doubt
Many scientists doubted DNA carried genetic code due to its relative simplicity and few components.
106
DNA
Polymer of nucleotides (polynucleotide) consisting of deoxyribose, a phosphate group, and a nitrogen-containing organic base.
107
RNA
Polymer of nucleotides (polynucleotide) consisting of ribose, a phosphate group, and a nitrogen-containing organic base.
108
Phosphodiester bonds
Bonds that join adjacent nucleotides in both DNA and RNA.
109
Double helix
Structure formed by two polynucleotide chains held together by hydrogen bonds.
110
Hydrogen bonds
Weak bonds that hold together specific complementary base pairs in DNA.
111
Complementary base pairing
The specific pairing of adenine with thymine and cytosine with guanine in DNA.
112
Messenger RNA (mRNA)
Single-stranded RNA that carries genetic information from DNA to the ribosome.
113
Deoxyribose
The pentose sugar found in DNA nucleotides.
114
Ribose
The pentose sugar found in RNA nucleotides.
115
Thymine
A nitrogenous base found in DNA but not in RNA.
116
Uracil
A nitrogenous base found in RNA but not in DNA.
117
Semi-conservative replication
The process by which each new DNA molecule consists of one original/template strand and one new strand.
118
DNA helicase
An enzyme that breaks hydrogen bonds between complementary bases, unwinding the double helix.
119
DNA polymerase
An enzyme that joins adjacent nucleotides on the new strand by condensation reactions.
120
Adenine
A nitrogenous base that pairs with thymine in DNA and uracil in RNA.
121
Cytosine
A nitrogenous base that pairs with guanine in both DNA and RNA.
122
Guanine
A nitrogenous base that pairs with cytosine in both DNA and RNA.
123
Semi-conservative replication importance
Ensures genetic continuity between generations of cells.
124
Watson and Crick
Scientists who proposed models of the chemical structure of DNA and of DNA replication.
125
Meselson and Stahl
Researchers who validated the Watson-Crick model of semi-conservative DNA replication.
126
Antiparallel strands
The orientation of DNA strands running in opposite directions.
127
Genetic information storage
The capacity of DNA to store a large amount of genetic information that codes for polypeptides.
128
Compact DNA structure
The coiled double helix structure of DNA allows for efficient storage.
129
Heavy nitrogen (15N)
Nitrogen isotope used in experiments to trace DNA incorporation.
130
Light nitrogen (14N)
Nitrogen isotope used in experiments to trace DNA replication.
131
DNA polymerase
Enzyme that joins adjacent nucleotides, forming phosphodiester bonds.
132
Hydrolysis reaction
Chemical reaction involving the breaking of a bond in a molecule using water.
133
DNA helicase
Enzyme that breaks hydrogen bonds to unzip the double helix of DNA.
134
Phosphodiester bonds
Bonds formed between the phosphate group of one nucleotide and the deoxyribose of another.
135
Complementary base pairing
The process by which free nucleotides attach to exposed nucleotide bases.
136
ATP
Adenosine triphosphate, the primary energy carrier in cells.
137
Structure of ATP
Ribose bound to a molecule of adenine and 3 phosphate groups.
138
ATP hydrolysis
ATP (+ water) → ADP + Pi, a reaction that releases energy.
139
ATP hydrolase
Enzyme that catalyzes the hydrolysis of ATP.
140
Energy requiring reactions
Reactions in cells that require energy, such as active transport and protein synthesis.
141
Phosphorylation
The process of adding a phosphate group to a compound, making it more reactive.
142
ATP resynthesis
ADP + Pi → ATP (+ water), a condensation reaction that stores energy.
143
ATP synthase
Enzyme that catalyzes the resynthesis of ATP during respiration and photosynthesis.
144
Properties of ATP
Releases energy in small amounts, immediate energy release, and cannot pass out of the cell.
145
Water
A major component of cells, essential for various biological processes.
146
why Hydrogen bonds in water occur
Occur due to the attraction between slightly negatively charged oxygen and slightly positively charged hydrogen atoms.
147
Metabolite
Substance involved in metabolic reactions, such as condensation and hydrolysis.
148
Solvent
Water's ability to dissolve solutes, allowing metabolic reactions to occur faster.
149
High specific heat capacity
Water's ability to buffer changes in temperature, providing a stable environment for organisms.
150
Aquatic habitat
Water provides a stable temperature environment, making it a good habitat for aquatic organisms.
151
High latent heat of vaporisation
Allows effective cooling via evaporation of a small volume (eg. sweat).
152
Strong cohesion between water molecules
Supports columns of water eg. transpiration stream through xylem in plants.
153
Surface tension
Produces surface tension, supporting small organisms (to walk on water).
154
Transpiration
The loss of water vapour from leaves.
155
Transpiration stream
The constant movement of water through the plant.
156
Hydrogen ions (H+)
Maintain pH levels in the body → high conc. = acidic / low pH.
157
Iron ions (Fe2+)
Component of haem group of haemoglobin, allowing oxygen to bind / associate for transport as oxyhaemoglobin.
158
Sodium ions (Na+)
Involved in co-transport of glucose / amino acids into cells.
159
Sodium ions (Na+)
Involved in action potentials in neurons.
160
Sodium ions (Na+)
Affects water potential of cells / osmosis.
161
Phosphate ions (PO4 3-)
Component of nucleotides, allowing phosphodiester bonds to form in DNA / RNA.
162
Phosphate ions (PO4 3-)
Component of ATP, allowing energy release.
163
Phosphate ions (PO4 3-)
Phosphorylates other compounds making them more reactive.
164
Phosphate ions (PO4 3-)
Hydrophilic part of phospholipids, allowing a bilayer to form.
165
Common mistake: Water has a high latent heat of evaporation
Water has a high latent heat of vaporisation.
166
Common mistake: Water is a solute
Water is a solvent that dissolves other substances (solutes).
167
Common mistake: Water is cohesive which aids transpiration
Cohesion aids the transpiration stream.
168
Common mistake: Naming an ion as an element
You need to say 'iron ions' and not just 'iron'.
169
Common mistake: ATP hydrolysis creates energy
Energy cannot be created - only transferred / released.
