2.1.2 - Biological Molecules Flashcards
1
Q
Definition of carbohydrate
A
Group of substances used as both an energy source and structural material
2
Q
General formula of carbohydrates
A
Cx(H2)y
3
Q
3 main groups of simple carbohydrates
A
Monosaccharide
Disaccharide
Polysaccharide
4
Q
Key facts about glucose
A
Abundant and very important
Major energy source
Highly soluble and main form of carbohydrates transported in animals
5
Q
Why is glucose a hexose sugar
A
It has 6 carbon atoms
6
Q
What does glucose exist as
A
Structural isomers
7
Q
Common isomers of glucose
A
Alpha glucose
Beta glucose
8
Q
What is the difference between the isomers of glucose
A
The OH is below the first carbon in the structure of alpha glucose whereas it is above the first carbon in the structure of beta glucose
Minor structural difference has a major effect on roles of alpha and beta glucose
9
Q
Key points about fructose
A
Fructose is very soluble and the main sugar in fruits
It is much sweeter than glucose
10
Q
Key points about galactose
A
It is not as soluble as glucose and fructose
It is important in making glycolipids and glycoproteins
11
Q
Important pentoses
A
Ribose
Deoxyribose
12
Q
What is the difference in the structures of ribose and deoxyribose
A
Ribose has a H above the second carbon and an OH below
Deoxyribose has only a H above and below the second carbon
13
Q
What does the prefix ‘glyco’ tell us
A
It has something to do with carbohydrates
14
Q
Condensation reaction
A
Attaching two monosaccharides by the formation of a glycosidic bond to produce a disaccharide and water
15
Q
Hydrolysis reaction
A
Breaking the glycosidic bond in a disaccharide with the addition of water
16
Q
Maltose
A
Glucose and Glucose
17
Q
How is maltose joined
A
By an alpha 1-4 glycosidic bond
18
Q
Sucrose
A
Fructose and Glucose
19
Q
How is sucrose joined
A
By an alpha 1-4 glycosidic bond
20
Q
Lactose
A
Galactose and Glucose
21
Q
How is lactose joined
A
By an beta 1-4 glycosidic bond
22
Q
Are monosaccharides reducing or not
A
Reducing
23
Q
Heterogeneous
A
Composed of different types
24
Q
Macromolecules
A
Molecules consisting of large numbers of atoms
25
Metabolism
All the chemical reactions that occur in cells
26
Monosaccharide
A sweet-tasting molecule consisting of a single unit
27
Nucleic acid
A kind of acid abundant in the nuclei of cells, includes DNA and RNA
28
What makes up organic compounds
Carbon and hydrogen
29
What are the four categories of macromolecules
Lipids
Proteins
Nucleic acids
Carbohydrates
30
What is a monomer
Small building blocks that make up biological molecules
31
Why are lipids important
Make up all of the cell membranes
Great source of energy
They don’t have a single type of monomer
32
Are lipids polar or unpolar
Polar
33
What are nucleic acid monomers
RNA
| DNA
34
What are nucleic acid monomers made of
Nucleotides
35
What are the functions of nucleic acids
Carry genetic material
36
What differentiates amino acids
Their ‘R’ group
37
What are carbohydrate monomers
Sugars
38
Dehydration synthesis
The process of putting monomers together where water is lost and peptide bonds are formed between amino acids
39
Hydrolysis
Splitting apart polymers using water
40
What are the three parts of a nucleotide
Phosphate
5-carbon sugar (pentose)
Base
41
Differences between DNA and RNA
They have different bases and DNA has a double helix
42
4 nucleotides in DNA
Cytosine
Guanine
Adenine
Thymine
43
4 nucleotides in RNA
Cytosine
Guanine
Adenine
Uracil
44
What makes DNA anti parallel
The helixes run in different directions
45
How many amino acids are there
20
46
What determines the directionality of a protein
Carboxyl side
| Amino side
47
Different types of lipids
Cholesterol
Free fatty acid
Triglyceride
Phospholid
48
What is the similar structure between all the lipids
Hydrocarbon tails
49
What is significant about hydrocarbons found in lipids
They’re non polar
| A huge amount of energy can be released
50
What is unique about phospholids
It has a non polar and polar portion
| Can form bilayers or micelles
51
What does amphipathic mean
It has a charged polar portion
52
What is the difference between saturated and unsaturated fatty acids
Unsaturated fats bend because they have a double bond
53
What determines the directionality in carbohydrates
Where the bond comes off
54
Amylose
```
Form of starch
Found as granules in cells
Alpha 1-4 glycosidic bond only
Compact helical structure
Unbranched chains
```
55
Amylopectin
Form of starch
Found as granules in cells
Glucose molecules joined by alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds
Branches and cannot form a helix
56
What is the percentage composition of starch
Amylopectin - 70-80%
| Amylose - 20-30%
57
How is starch stored in plants
In plastids
58
Plastids
Intracellular starch grains in organelles
| Made from green chloroplasts and colourless amyloplasts
59
What does cellulose stop
Cells from bursting
60
Structure of cellulose
Beta glucose joined by beta 1-4 glycosidic bonds
H bonds between chains
Can form micro and macofibrils
61
Microfibrils
Glucose in a rope like form which are then layered in a network
62
What is special about formation of cellulose
Every other glucose molecule molecule rotates 180 so that the hydroxyl groups are adjacent
63
What gives cellulose great tensile strength
Hydrogen bonds
They are very weak on their own but strong in large numbers
64
Glycogen compared to starch
Less dense
More soluble
Broken down more rapidly as ends are exposed
Both insoluble
65
Structure of glycogen
Similar structure to amylopectin but it’s more branched
66
Why don’t animals store starch
They store glycogen instead
67
What molecule is produced in the condensation of nucleotides
DNA
68
What molecule is produced in the hydrolysis of DNA
Nucleotides
69
What molecule is produced in the condensation of amino acids
Protein
70
What molecule is produced in the condensation of fructose and glucose
Sucrose
71
What molecule is produced in the condensation of glycerol and fatty acid
Lipids
72
What molecule is produced in the hydrolysis of protein
Amino acids
73
What molecules are produced in the hydrolysis of sucrose
Fructose and glucose
74
What molecules are produced in the hydrolysis of lipids
Glycerol and fatty acids
75
What are the chemical elements that make up carbohydrates
Carbon
Hydrogen
Oxygen
76
What are the chemical elements that make up lipids
Carbon
Hydrogen
Oxygen
77
What are the chemical elements that make up proteins
```
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
```
78
What are the chemical elements that make up nucleic acids
```
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorous
```
79
What type of links are formed in the synthesis of lipids
Ester links are formed by condensation between the alcohol groups on a glycerol molecule and three fatty acids
80
What happens as a result of water’s polarity
Adjacent water molecules are attracted to and become bonded to each other
81
How are hydrogen bonds formed
The slight positive charge of a hydrogen atom of one molecule is attached to the slight negative charge of an adjacent oxygen atom
82
Functions of water
Transport
Chemical reactions (metabolism)
Temperature control - high latent heat of evaporation (stable environment for aquatic org.)
Support
Efficient transport medium - cohesion and adhesion
Reproduction
83
Transport as a function of water
Transpiration stream and water-based movement of sugars and amino acids, hormones etc. in phloem occurs in solution
Many essential metabolites dissolve completely
84
What is the transpiration stream held together by
Cohesion
| Adhesion
85
Cohesion
Water molecules hydrogen bond to other molecules
86
Adhesion
Water molecules bind to the side of xylem vessel
87
Chemical reactions as a function of water
Combination of thermal stability and excellent solvent properties make water and ideal environment for chemical reactions
Water acts as a reactant for:
1) . Light dependent stage in photosynthesis
2) . Hydrolytic reactions
88
Support as a function of water
In plant cells water offers turgidity
In animals, water-filled tissues also contribute to skeletal support
For aquatic organisms, water provided support through buoyancy
89
Reproduction as a function of water
Water brings the male and female gametes together in fertilisation
Foetus develops in water filled sac
90
Test for starch
Iodine dissolved in KI turns from brown/orange to blue/black
91
Test for reducing sugars (all mono, maltose and lactose)
Benedict’s test
Add Bendicts reagent
Heat solution in water bath > 80 degrees for 5 mins
Solution turns from blue to green/ yellow/ orange/ brown or brick-red suspension
92
Test for proteins
Biurets test
Add NaOH
Add copper (II) sulphate solution
Solution turns from blue to purple if protein's present
93
Test for lipids
Emulsion test
Add water and shake
Add ethanol to dissolve lipid
A white emulsion/ band floating near or at the top in the presence of lipids
94
Properties of water influenced by its polar nature
Solvent properties
Thermal properties
Cohesion tension
Specific heat capacity
95
Types of lipids
Triglycerides
Phospholipids
Saturated and unsaturated fatty acid
96
What chemical elements make up lipids
Carbon
Hydrogen
Oxygen
97
Components of a triglyceride
1 glycerol molecule and 3 fatty acid chains attached by Ester bonds
98
What are triglycerides known as
True fats or neutral fats
99
Characteristics of triglycerides
Rich in energy and used to store energy
Good insulators and provide buoyancy
Can be broken down in aerobic respiration and water is released
100
Saturated fats
```
Solid at room temp
Only single bonds
Have a lot of hydrogen
Found in animals
Higher melting point
```
101
Unsaturated fats
```
Liquid at room temp
Double carbon bonds
Bent (linked)
Found in plants
Lower melting point
```
102
Function of lipids in the body
```
Energy store
Thermal insulation
Repel water
Shock absorbent
Buoyant
Waterproof
```
103
How do phospholipids differ in their structure from triglycerides
Phosphate group replaces one fatty acid
104
Why are lipids useful storage molecules
Insoluble molecules
| High energy yield (2x as much as carbohydrates)
105
What factors do substances need to have to be 'transport' carbohydrates
Small
Soluble
Not reactive
106
What causes the colour change in the Benedict's test
The copper is reduced by the reducing sugars to form ions
107
Why can't humans digest all polysaccharides
We do not possess the appropriate enzymes
108
How to reverse condensation reactions
Hydrolysis reactions
| Adding acid
109
Functions of proteins
```
Signalling
Catalysis
Structure and movement
Defence and survival
Transport
```
110
How do plants make amino acids
From photosynthesis and nitrate/mmonium
111
How many amino acids do human need
Twenty but we cannot make any of the 8/10 essential and 12/10 non essential amino acids
112
Why is the R group important
The Residual group is the only thing that differs in amino acids
113
Formation of peptide bond
Water is removed (condensation reaction)
| Peptide bond is formed (covalent C-N bond)
114
Dipeptide
2 amino acids
115
Polypeptide/ protein
Many amino acids
116
Primary structure of proteins
Subunits held together by peptide bonds
| Order determined by base sequences in DNA
117
Secondary structure of proteins
Folding or coiling of polypeptide chains for stabilisation
| Hydrogen bonds cause polypeptide to coil into alpha helix or fold into beta sheets
118
What breaks hydrogen bonds
High temperature
| pH change
119
How does a breakage of bonds affect the protein
It affects the shape and function
120
Tertiary structure of proteins
The secondary structure is folded into a more complex 3D shape
121
What is the tertiary structure stabilised by
Disulphide bonds between sulfur containing R groups
Ionic bonds between R groups
Hydrogen bonds between polar R groups
Hydrophobic/ hydrophilic interaction
122
Quaternary structure of proteins
Made up from multi sub-unit proteins
Held together by same bonds in 3'
Most proteins only have one polypeptide chain and so no quaternary structure
123
Globular proteins
Spherical and usually soluble
Hydrophobic R groups in centre, hydrophilic R groups point outside
Activity in metabolism relies on 3D shape
Shape and activity sensitive to high temp.
124
Why is haemoglobin a conjugated protein
It has a prosthetic group
125
What is a prosthetic group in a protein
An attachment not made from protein e.g. Haem
126
Structure of haemoglobin
All 4 polypeptide chains are attached to a haem group
127
What ions do haem contain
Fe 2+ ions and they bond with O2
128
Sub units of haemoglobin
2 alpha chains
2 beta chains
4 haem groups
129
Amylase
Alpha helix and beta sheets
Globular shape has an complementary active site
Active site holds Cl- (co-factor - essential for correct action)
130
Insulin
2 polypeptides held together by disulphide bridges
Globular protein w/ spp, fixed shape
Specific 3D shape complementary to glycoproteins receptor
131
Fibrous proteins
Form long strands and usually insoluble
Have structural roles in the body
Regular sequence of amino acids
Unreactive
132
Collagen
3 polypeptide chains wound around each other
Fibrous protein that is flexible but does not strech
Not easily stretched
Found in walls of arteries and tendons
133
Keratin
2 coiled polypeptide chains containing sulfur
Protect delicate things e.g. nails,claws, hair, feathers, hooves
Found in outer layers of skin cells (permeability)
134
Elastin
Linking tropelastin fibres
Coiled and can be stretched and recoiled
Used where stretching is required e.g. alveoli, walls of arteries, airways, bladder
135
Test for non reducing sugars (sucrose)
Add HCl to sample whilst heating iin a water bath > 80 degrees (to hydrolyse sample)
Add NaOH (to neutralise sample)
Then conduct test for reducing sugars
136
Where are peptide bonds formed
Between the hydroxide from the amine group and the H from the carboxyl group
137
What happens when proteins are over heated
```
Increased kinetic energy
Molecule vibrates
H bonds break
Change in 3’ structure
Denatures
```
138
What is thin layer chromatography used for
Separation of proteins, carbs, vitamins or nucleic acids
139
Starch + amylase —>
Maltose
140
Properties of water useful to living things
Strong cohesive forces between water molecules at the water surface mean that it is a good medium for support
H bonds attract water molecules to each other but are weak so that water molecules can move easily in relation to one another
141
Test for reducing sugars if using a solid
Crush the solid w/ water
Filter out the solid
Continue test as normal
142
Compare conc. of reducing sugars
Filter sol. and weigh ppt. formed, the heaver the ppt, the more conc.
Compare colours after benedict's test - less accurate
143
Colorimetry - to find unknown glucose sol.
Make up several sol. of KNOWN glucose conc. (serial dilution)
Carry out Benedicts's test - same vol. of reagent
Remove any ppt
Using colorimeter measure absorbance
Plot calibration curve , with glucose conc. on x and absorbance on y
144
How to use a colorimeter
Set up w/ red filter - no effect w/ blue
Add distilled water to cuvette to calibrate colorimeter- light should pass through clear side
Use a pippette to transfer each solution of sol. of known glucose conc into seperate cuvettes
Measure absorbance for each
145
Glucose bisensors
Determines conc of glucose in a solution
Glucose oxidase immobilised to electrodes, binds to and catalyses oxidation of glucose
Creates a charge which is then converted by a transducer
The electrical signal is then processed to work out the glucose conc.
146
Mobile phase in chromatography
Where the molecules can move
Solvent (ethanol) in bother paper and TLC
The more time spent here the faster/ further up the stationary phase
147
Stationary phase in chromatography
Where the molecules can't move
| Paper in paper chromatography or silica gel on a glass plate in TLC
148
Structure of cholesterol
Sterol
4 carbon rings w/ hydroxyl group
Hydroxyl group is polar o rest of molecule is hydrophobic
149
Biological roles of lipids due to their non polar nature
Membrane formation and the creation of hydrophobic barrier
Hormone production
Electrical insulation (nerves)
Waterproofing
150
Separating amino acids w TLC
Follow normal TLC procedure but after silica gel plate has been allowed to dry, spray w/ ninhydrin spray to give a purple/brown colour
151
Catalase
4' protein w 4 haem groups
| Fe2+ speeds up the breakdown of H2O2 - common by-product of metabolism but dangerous if accumulates
