1: Biological Molecules Flashcards
(166 cards)
1
Q
What is a polymer?
A
Long chain of monomer sub-units
2
Q
What is the transformation of a monomer to a polymer?
A
Polymerisation
3
Q
What does the delta symbol mean?
A
Slightly
4
Q
What is a dipolar molecule?
A
Means a molecule which has two different charged regions
5
Q
Why is water dipolar?
A
As electrons are slightly closer to the oxygen
6
Q
What are the charges on a water molecule?
A
Oxygen is slightly negative
Hydrogen atoms are slightly positive
7
Q
What is a hydrogen bond?
A
Attraction between water molecules caused by attraction
8
Q
How strong are hydrogen bonds?
A
Very weak
Many needed to make a difference
9
Q
What is the general formula of monosaccharides?
A
(CH20)n
n= any number from 3-7
10
Q
What are the features of monosaccharides?
A
Sweet
Small
Soluble
Crystals
11
Q
What does the suffix -ose mean?
A
A sugar
12
Q
Name some examples of monosaccharides
A
Glucose, galactose, and fructose
13
Q
What are the two isomers of glucose?
A
Alpha and Beta Glucose
14
Q
What is a hexose?
A
Sugars with 6 carbons
15
Q
What is a steroisomer?
A
Different forms of the same isomers
16
Q
What is the difference between alpha and beta glucose?
A
OH (hydroxide) on carbon 1 is downwards on the alpha glucose and vice versa on the beta glucose
17
Q
What is the use of beta glucose?
A
Used in plant cells to create cellulose
18
Q
What is the use of alpha glucose?
A
Used in animals to create glycogen
19
Q
What are the features of disaccharides?
A
Small
Sweet
Soluble
Crystals
20
Q
What is a disaccharide?
A
Two monosaccharides joined together
21
Q
What reaction forms a disaccharides?
A
Condensation reaction
Creates a water molecule and glycosidic link
22
Q
What is a glycosidic link?
A
Bond that is formed between two monosaccharides
23
Q
a Glucose + a Glucose
A
Maltose
24
Q
Glucose + Fructose
A
Sucrose
25
Glucose + Galactose
Lactose
26
Where is sucrose found?
Transported in plants
27
Where is lactose found?
Milk (lactose intolerance)
28
What reaction would split up a disaccharide and why?
Hydrolysis - as water is required to form both monosaccharides
29
What are the reducing sugars?
All monosaccharides and some disaccharides (maltose & lactose)
30
What is reduction?
Chemical reaction involving the gain of electrons
31
What is a reducing sugar?
Sugar that can donate electrons to another chemical
32
What chemical is used for the reducing sugar test?
Benedict's Reagent (copper sulphate + alkaline solution)
33
What ions are relevant in the Benedict's Reagent?
Copper 2+ ions
34
What happens to the Benedict's Reagent in the reducing sugar experiment?
Forms an insoluble red precipitate (Cu2O)
| if reducing sugar present
35
Give the step-by-step method of the test for reducing sugars
Add 2 cm2 of the sample to a test tube, and if not liquid grind it up in water
Add an equal volume of Benedict's reagent
Heat the mixture in a gently boiling water bath for 5 minutes
36
Why is the colour of the reducing sugar test semi quantitative?
As it can be used to give a rough idea about the amount of sugar produced
37
What colours in the reducing sugar test show the most sugar present?
(most to least)
| red, orange, yellow, green, blue
38
Name 2 ways to make the reducing sugar quantitative?
Colorimeter
| Weighing dry mass of the precipitate
39
What is hydrolysis?
Addition of water that causes breakdown
40
Name a common non-reducing sugar
Disaccharides (Sucrose)
41
What is the non-reducing sugar test?
Breaking up disaccharides into monosaccharides (hydrolysis)
| Then perform reducing sugar test
42
Give the step-by-step method of the test for non-reducing sugars
Perform reducing sugars test
If no colour change (blue), add 2 cm2 of fresh sample to 2cm2 of HCl and place in waterbath for 5 mins
Add NaHCO3 to solution until neutralised
Perform reducing sugar test on this sample
43
What is a positive result of a the non-reducing sugar test?
The solution will go orange-brown
44
Why is it necessary to add hydrochloric acid in the non-reducing sugar test?
Hydrolyses the disaccharide into both its constituent monosaccharides
45
Why is it necessary to add sodium hydrocarbonate in the non-reducing sugar test?
Neutralise the solution as Benedict's doesn't work in acidic conditions
46
What is a polysaccharide?
Polymers of many monosaccharide molecules joined by glycosidic bonds
47
What reaction forms polysaccharides?
Condensation reactions
48
What is the solubility of polysaccharides and why?
Insoluble as very large molecules
| Therefore suitable for storage
49
What happens when polysaccharides are hydrolysed?
Breaks up into monosaccharides or disaccharides
50
What is the composition of starch?
Between 200 and 100 000 a-glucose molecules connected by glycosidic links
51
What is starch?
Polysaccharide used for energy storage
Found in starch grains in cytoplasm and chloroplasts
Can be branched and unbranched
52
What are the structures of starch?
Unbranched tight coil - very compact
| Branched - quick hydrolysis
53
Why is starch suited for its role of energy storage?
Insoluble - doesn't affect water potential
Large & insoluble - cannot diffuse out of a cell
Compact - can be stored in a small space
Made of a-glucose - easily transported & used in respiration
Branched form - many ends means enzymes can simultaneously release a-glucose
54
How easy is hydrolysis of starch?
Branched - Easy
| Unbranched coils - Not as easy
55
What are two types of starch?
Amylose (unbranched)
| Amylopectin (branched)
56
What are the digestive enzymes of starch?
Amylase
| Maltase
57
What is the tensile strength of starch?
Low
58
What is the step-by-step test for starch?
2 cm2 of sample and add two drops of iodine
Shake or stir
Starch shown by solution going black-blue
59
Where is glycogen found?
Small granules in animals and bacteria, never in plants
| Mainly in muscles and liver
60
What is the structure of glycogen?
Linear highly branched (shorter than starch)
61
What is the use of glycogen?
Carbohydrate storage in animals
62
Why is the mass of carbohydrate storage in animals small?
Fat is the main energy storage in animals
63
Why is the structure of glycogen suited to energy storage?
Insoluble - doesn't affect water potential
Large & insoluble - cannot diffuse out of a cell
Compact - can be stored in a small space
More highly branched - many ends means enzymes can break it down faster
64
Why is highly branched glycogen useful?
Means glucose can be released faster for respiration
| Important as animals with high metabolic & respiratory rate so its needed
65
What is the monomerof cellulose?
B-glucose
| Every other molecule is flipped which allows the glycosidic link to form
66
What is the structure of cellulose?
Straight unbranched chains
| They run parallel and form many hydrogen bonds
67
What is the use of cellulose?
Main component of cell wall
| Groups of them form microfibrils, and groups of these in parallel form fibres
68
What is the function of the cellulose cell wall?
Provides rigidity
Prevents bursting from osmosis - exerts inwards pressure
Cells therefore turgid and form a semi-rigid structure
69
In which plant cells are strong cell walls important?
Stems and leaves (max SA for photosynthesis)
70
Why is cellulose suited for its role?
Made of "flipped"B-glucose - forms unbranched chains
Chains are parallel - hydrogen bonds can form
Fibers and microfibrils - provide more strength
Insoluble - doesn't affect water potential
71
What is the digestive enzyme of cellulose?
Cellulase
| Not found in humans
72
Are hydrogen bonds important in cellulose?
Yes
| Although one isn't very strong, the sheer number makes a difference
73
What are the characteristics of lipids?
Made of Hydrogen, Carbon, Oxygen
Insoluble in water
Proportion of oxygen to carbon & hydrogen is smaller than in carbohydrates
Soluble in organic solvents (alcohols)
74
What are the two types of lipids?
Tryglycerides and phospholipids
75
Name some roles of lipids
```
Cell membrane
Source of energy
Waterproofing
Insulation
Protection
```
76
Why is a lipid suited to be a source of energy?
When oxidised it provides more than 2x the energy compared to the same mass of carbohydrates
Releases water
77
Why is a lipid suited to do waterproofing?
Insoluble in water
| Plants have waxy cuticles, mammals have oily secretion from glands in the skin
78
Why is a lipid suited to insulation?
Slow conductor of heat
| Acts as electrical insulator in myelin sheath around nerve cells
79
What state are lipids?
Fats are solid at room temp. whereas oils are liquids
80
What is the structure of triglycerides?
Glycerol bonded to three fatty acids
81
What type of bonding is present in lipids?
Ester bonds - formed by 3 condensation reactions
82
What causes variation in properties in triglycerides?
Fatty acid groups - all with carboxylic acid (COOH) group at the end
Over 70 different
83
What does an unsaturated or saturated fatty acid mean?
Saturated - all c-c bonds are single (holding max number of hydrogen)
Mono/poly unsaturated - one/many c-c bonds are double
84
What is the state of saturated and unsaturated lipids?
Saturated fats- straight chains so they pack closely and therefore are solids
Unsaturated oils - chains have kinks due to double bonds therefore are liquids
85
Why are triglycerides suited for energy storage?
High ratio of c-h energy storing bonds to c atoms
Low mass to energy ratio - animal doesn't have to waste energy on carrying heavier store
Large and non-polar - insoluble, no affect on water potential
High ratio of hydrogen to oxygen - release water when oxidesed, important for desert animals
86
What is the structure of a phospholipid?
Glycerol
Two fatty acids
One phosphate group
87
What is the solubility of phospholipids ?
Hydrophillic phosphate "head" - attracted to water
| Hydrophobic fatty acid "tails"
88
What does the polar nature of phospholipids cause?
Bilayers which is the basis of membranes
| Hydrophobic barrier formed between inside and outside of cell
89
What do phospholipids do in water?
Hydrophillic head tries to get as close to water
| Hydrophobic tails tries to get as far away as possible
90
What can an interaction between a carbohydrate and a phospholipid?
Glycolipid can be formed
| Used for cell recognition
91
What is the name of the test for lipids?
Emulsion test
92
Give the step-by-step test for lipids
2 cm3 of sample in a dry and clean test tube with 5 cm3 of ethanol
Shake thoroughly to dissolve lipid
Add 5 cm3 of water and shake gently
Cloudy-white coloured emulsion indicates lipid
93
Give the step-by-step test for proteins
Add sample to test tube with equal volume of sodium hydroxide
Add a few drops of very dilute copper (II) sulphate solution (biuret solution)
Purple indicates presence of peptide bonds
94
What is the size of proteins?
Very large molecules
95
What elements are in proteins?
Carbon, oxygen, hydrogen, nitrogen
96
What is the monomer and polymer called of a protein?
Amino acids
| Polypeptides
97
How many amino acids have been identified?
100 amino acids
| 20 naturally occurring
98
What does 20 naturally occurring amino acids suggest?
Indirect evidence for evolution
99
What are the four parts of amino acid?
```
Amino group (NH2)
Carboxyl group (COOH)
Hydrogen atom (H)
R group (different chemical)
```
100
What reaction joins amino acids?
Condensation reaction forms peptide bond
101
Where is a peptide bond?
Between the carboxyl group of one and a amino group is another
102
How can a peptide bond be broken?
Hydrolysis
103
What is the primary structure of proteins?
Polypeptide chain
Many different possible sequences
Simple protein
104
What are the two secondary protein structures?
Alpha helix
| Beta pleat
105
What does protein structure determine?
Protein function
106
Why do proteins form alpha helix?
H of NH group is positive and O of CO is negative
| Causes hydrogen bonds which cause alpha helix
107
What forms between beta pleats?
Hydrogen bonding
108
How can tertiary protein structure be described?
Globular like structure
| Formed by twisting and folding secondary
109
What bonds are found in tertiary protein structure?
Disulphide bridges - quite strong, not easily broken
Ionic bonds - between carboxyl and amino acids, weak adn broken by pH change
Hydrogen bonds - numerous but easily broken
110
What is the solubility of globular proteins?
Soluble
111
What is a prosthetic group?
Non-protein structure
| Found in Quaternary structure
112
Name a prosthetic group
Myoglobin has a haem prosthetic
113
What is the Quaternary structure?
Two or more interlinked globular proteins
114
What type of proteins are enzymes?
Globular tertiary proteins
115
What is a catalyst?
Something that alters the rate of a chemical reaction without undergoing permanent changes
116
What is activation energy?
The minimum amount of energy required to active a reaction
117
How do enzymes affect activation energy?
Lowers activation energy by forming an enzyme-substrate complex
118
What is an intra-cellular enzyme?
Works inside the cell
| DNA
119
What is an extracellular enzyme?
Secreted by cells and words outside
| Pepsin, amylase
120
What is the suffix typically associated with enzymes?
-ase
121
What is a catabolic reaction?
Larger molecules broken helped by active sites affecting bonds
122
What is an anabolic reaction?
Enzymes bring substrate molecules together
123
What does the lock-and-key hypothesis suggest?
The enzyme and substrate molecules fit together exactly like a lock and key
124
What is the problem with the lock-and-key hypothesis?
It suggests the active site is rigid
| However crystallographic studies indicates proteins are flexible
125
What is the induced-fit hypothesis?
The active site only assumes catalytic confirmation (shape) after the substrate molecule binds to the site
126
What happens if the incorrect molecule binds to an enzyme?
Will bind but causes no conformational change
| No reaction occurs
127
What happens to the active site after a substrate is broken down?
Reverts to inactive state
128
What is a substrate?
A molecule which an enzyme acts on
129
How do enzymes lower activation energy?
Strains the bonds in the substrate
130
What two things must occur for an enzyme to work?
Come into physical contact with substrate
| Have an active site which fits the substrate
131
How do you measure the rate of reaction of enzymes?
Formation of products
| Disappearance of substrate
132
What is the turnover number?
Number of substrate molecules transformed / minute by one enzyme
133
Describe the rate of reaction vs enzyme concentration graph?
As enzyme conc. increases the rate of reaction increases
| Until a point when it plateaus, when the rate of reaction doesn't change as conc. increases
134
Explain the start of the rate of reaction vs enzyme concentration graph?
Enzyme is the limiting factor
Substrate molecules outnumber enzymes
Adding more enzymes adds more active sites
135
Explain the latter part of the rate of reaction vs enzyme concentration graph?
Substrate is limiting factor
Adding more enzymes doesn't affect reaction
Adding more substrate makes more ESC
136
How can you calculate the change in rate of reaction?
Calculate gradient of a graph of product produced or substrate disappearance
137
How can the rate of reaction graph vs substrate reaction be described?
As substrate conc. increases the rate of reaction increases
| Until a point when it plateaus, when the rate of reaction doesn't change as conc. increases
138
How can the rate of reaction graph vs substrate reaction be explained?
```
Same as enzyme concentration
Except reversed (at first substrate is limiting factor, then enzyme)
```
139
What is denaturation?
Permanent change whereby an enzyme can no longer function
140
What is pH?
A measure of the number of H+ ions present in a solution
141
What is the mathematical process behind working out pH?
-log10(H+)
E.g 0.1M = pH1
142
How do enzymes perform in varying pH?
Only work in a narrow range of pH
| Have an optimum pH which their rate is fastest
143
How do H+ ions denature enzymes?
Charges on the active site
| Disrupts hydrogen and ionic bonds
144
How does changing the charge of the active site denature the enzyme?
H+ ions reversed the charge of the active site
| Substrate can no longer bind to the AS and ESC can't form
145
How does disrupting bonds in the enzyme denature the enzyme?
Hydrogen and ionic bonds which keeps 3D structure is disrupted
Shape of AS is lost and no ESC can form
146
Describe the temp. vs enzyme activity graph
Increases steadily as temp. increases
| Until optimum, after which is denatured. Then as temp. increases it decreases quickly
147
Explain the gradual increase in enzyme activity as temperature increases
Increases kinetic energy of molecules
Moves more rapidly and and collisions more often between enzyme and substrate
More ESC form
148
Explain the dramatic decrease in enzyme activity as temperature increases past a point
High kinetic energy means atoms within enzyme vibrate
Causes weak hydrogen bonds to break
Loses tertiary structure and AS lost, no ESC can form
149
What is the temperature coefficient (Q10)?
Rate of change of a reaction when the temp is increased by 10C
(rate doubles every 10C rise in temp.)
150
What is the equation of Q10?
Rate of reaction at (x+10) / rate of reaction at x
151
What is an inhibitor?
A chemical which inhibits enzyme activity
152
What are the two types of inhibitors?
Competitive and non-competitive
153
How do competitive inhibitors work?
Same shape as substrate
Binds to enzyme but causes no change in shape
Not broken down
Therefore enzyme not breaking down substrate so slows rate of reaction
154
How can you overcome the effect of competitive inhibitors?
Try to remove inhibitor from solution
| Increase concentration of substrate
155
Explain why competitive inhibitors can be overcome
Increasing conc. of substrate increases the likelihood that ESC will form
156
What will the graph of rate of reaction vs substrate conc. look like with competitive inhibitors?
Reaches same plateau but takes longer to get there
| less steep curve
157
How do non-competitive inhibitors work?
Binds to allosteric site
Changes shape of AS
No ESC can form
158
Why do non-competitive inhibitors support the induced fit hypothesis?
Suggests that the AS is somewhat flexible
159
Is an inhibitor permanent?
Can be reversible or irreversible
160
What is the effective change to an enzyme from a irreversible non-competitive enzyme?
Denaturation
161
Can non-competitive inhibition be overcome?
No
| Unless make the inhibitor disassociate
162
What will the graph of rate of reaction vs substrate conc. look like with non-competitive inhibitors?
Plateaus lower
| Takes longer to get there
163
What chemical process is associated with gout?
Xanthine -> uric acid
Uses enzyme xanthine oxidase
Uric acid causes gout
164
What chemical is used to treat gout and why?
Allopurinol
Acts as a competitive inhibitor
Less uric acid produced
165
What is a metabolic pathway?
Series of chemical reactions converting substrate into end products using enzymes
166
What is end-product inhibition?
The final product of a metabolic pathway inhibits one of the enzymes
Non-competitive
