2.1.2 - Biological Molecules Flashcards
(148 cards)
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 are the 3 ways to represent glucose
A
Straight chain
Ring
Ring (simplified)
7
Q
What does glucose exist as
A
Structural isomers
8
Q
Common isomers of glucose
A
Alpha glucose
Beta glucose
9
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
10
Q
Key points about fructose
A
Fructose is very soluble and the main sugar in fruits
It is much sweeter than glucose
11
Q
Key points about galactose
A
It is not as soluble as glucose and fructose
It is important in making glycolipids and glycoproteins
12
Q
Important pentoses
A
Ribose
Deoxyribose
13
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
14
Q
What does the prefix ‘glyco’ tell us
A
It has something to do with carbohydrates
15
Q
Condensation reaction
A
Attaching two monosaccharides by the formation of a glycosidic bond to produce a disaccharide and water
16
Q
Hydrolysis reaction
A
Breaking the glycosidic bond in a disaccharide with the addition of water
17
Q
Maltose
A
Glucose and Glucose
18
Q
How is maltose joined
A
By an alpha 1-4 glycosidic bond
19
Q
Sucrose
A
Fructose and Glucose
20
Q
How is sucrose joined
A
By an alpha 1-4 glycosidic bond
21
Q
Lactose
A
Galactose and Glucose
22
Q
How is lactose joined
A
By an beta 1-4 glycosidic bond
23
Q
Are monosaccharides reducing or not
A
Reducing
24
Q
Heterogeneous
A
Composed of different types
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Macromolecules
Molecules consisting of large numbers of atoms
26
Metabolism
All the chemical reactions that occur in cells
27
Monosaccharide
A sweet-tasting molecule consisting of a single unit
28
Nucleic acid
A kind of acid abundant in the nuclei of cells, includes DNA and RNA
29
What makes up organic compounds
Carbon and hydrogen
30
What are the four categories of macromolecules
Lipids
Proteins
Nucleic acids
Carbohydrates
31
What is a monomer
Small building blocks that make up biological molecules
32
Why are lipids important
Make up all of the cell membranes
Great source of energy
They don’t have a single type of monomer
33
Are lipids polar or unpolar
Polar
34
What are nucleic acid monomers
RNA
| DNA
35
What are nucleic acid monomers made of
Nucleotides
36
What are the functions of nucleic acids
Carry genetic material
37
What differentiates amino acids
Their ‘R’ group
38
What are carbohydrate monomers
Sugars
39
Dehydration synthesis
The process of putting monomers together where water is lost and peptide bonds are formed between amino acids
40
Hydrolysis
Splitting apart polymers using water
41
What are the three parts of a nucleotide
Phosphate
5-carbon sugar (pentose)
Base
42
Differences between DNA and RNA
They have different bases and DNA has a double helix
43
4 nucleotides in DNA
Cytosine
Guanine
Adenine
Thymine
44
4 nucleotides in RNA
Cytosine
Guanine
Adenine
Uracil
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What makes DNA anti parallel
The helixes run in different directions
46
How many amino acids are there
20
47
What determines the directionality of a protein
Carboxyl side
| Amino side
48
Different types of lipids
Cholesterol
Free fatty acid
Triglyceride
Phospholid
49
What is the similar structure between all the lipids
Hydrocarbon tails
50
What is significant about hydrocarbons found in lipids
They’re non polar
| A huge amount of energy can be released
51
What is unique about phospholids
It has a non polar and polar portion
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What does amphipathic mean
It has a charged polar portion
53
What is the difference between saturated and unsaturated fatty acids
Unsaturated fats bend because they have a double bond and don’t have hydrogen all the way down
54
What determines the directionality in carbohydrates
Where the bond comes off
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Amylose
Alpha 1-4 glycosidic bond only
Compact helical structure
Unbranched chains
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Amylopectin
Glucose molecules joined by alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds
Branches and cannot form a helix
57
What is the percentage composition of starch
Amylopectin - 70-80%
| Amylose - 20-30%
58
How is starch stored in plants
In plastids
59
Plastids
Intracellular starch grains in organelles
| Made from green chloroplasts and colourless amyloplasts
60
What does cellulose stop
Cells from bursting
61
Structure of cellulose
Beta glucose joined by beta 1-4 glycosidic bonds
62
Microfibrils
Glucose in a rope like form which are then layered in a network
63
What is special about formation of cellulose
Every other glucose molecule molecule rotates 180 so that the hydroxyl groups are adjacent
64
What gives cellulose great tensile strength
Hydrogen bonds
They are very weak on their own but strong in large numbers
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Glycogen compared to starch
Less dense
More soluble
Broken down more rapidly
66
Structure of glycogen
Similar structure to amylopectin but it’s more branched
67
Why don’t animals store starch
They store glycogen instead
68
What molecule is produced in the condensation of nucleotides
DNA
69
What molecule is produced in the hydrolysis of DNA
Nucleotides
70
What molecule is produced in the condensation of amino acids
Protein
71
What molecule is produced in the condensation of fructose and glucose
Sucrose
72
What molecule is produced in the condensation of glycerol and fatty acid
Lipids
73
What molecule is produced in the hydrolysis of protein
Amino acids
74
What molecules are produced in the hydrolysis of sucrose
Fructose and glucose
75
What molecules are produced in the hydrolysis of lipids
Glycerol and fatty acids
76
What are the chemical elements that make up carbohydrates
Carbon
Hydrogen
Oxygen
77
What are the chemical elements that make up lipids
Carbon
Hydrogen
Oxygen
78
What are the chemical elements that make up proteins
```
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
```
79
What are the chemical elements that make up nucleic acids
```
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorous
```
80
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
81
What happens as a result of water’s polarity
Adjacent water molecules are attracted to and become bonded to each other
82
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
83
Functions of water
```
Transport
Chemical reactions (metabolism)
Temperature control
Support
Movement
Reproduction
```
84
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
85
What is the transpiration stream held together by
Cohesion
| Adhesion
86
Cohesion
Water molecules hydrogen bond to other molecules
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Adhesion
Water molecules bind to the side of xylem vessel
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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
89
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
90
Reproduction as a function of water
Water brings the male and female gametes together in fertilisation
Foetus develops in water filled sac
91
Test for starch
Iodine dissolved in KI turns from brown/orange to blue/black
92
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
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Test for proteins
Biurets test
Add NaOH
Add copper (II) sulphate solution
Solution turns from blue to purple if protein's present
94
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
95
Properties of water influenced by its polar nature
Solvent properties
Thermal properties
Cohesion tension
Specific heat capacity
96
Types of lipids
Triglycerides
Phospholipids
Saturated and unsaturated fatty acid
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What chemical elements make up lipids
Carbon
Hydrogen
Oxygen
98
Components of a triglyceride
1 glycerol molecule and 3 fatty acid chains attached by Ester bonds
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What are triglycerides known as
True fats or neutral fats
100
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
101
Saturated fats
```
Solid at room temp
Only single bonds
Have a lot of hydrogen
Found in animals
Higher melting point
```
102
Unsaturated fats
```
Liquid at room temp
Double carbon bonds
Bent (linked)
Found in plants
Lower melting point
```
103
Function of lipids in the body
```
Energy store
Thermal insulation
Repel water
Shock absorbent
Buoyant
Waterproof
```
104
How do phospholipids differ in their structure from triglycerides
Phosphate group replaces one fatty acid
105
Why are lipids useful storage molecules
Insoluble molecules
| High energy yield (2x as much as carbohydrates)
106
What factors do substances need to have to be 'transport' carbohydrates
Small
Soluble
Not reactive
107
What causes the colour change in the Benedict's test
The copper is reduced by the reducing sugars to form ions
108
Why can't humans digest all polysaccharides
We do not possess the appropriate enzymes
109
How to reverse condensation reactions
Hydrolysis reactions
| Adding acid
110
Functions of proteins
```
Signalling
Catalysis
Structure and movement
Defence and survival
Transport
```
111
How do plants make amino acids
From photosynthesis and nitrate/ ammonium
112
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
113
Why is the R group important
The Residual group is the only thing that differs in amino acids
114
Formation of peptide bond
Water is removed (condensation reaction)
| Peptide bond is formed (covalent C-N bond)
115
Dipeptide
2 amino acids
116
Polypeptide/ protein
Many amino acids
117
Primary structure of proteins
Subunits held together by peptide bonds
| Order determined by base sequences in DNA
118
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
119
What breaks hydrogen bonds
High temperature
| pH change
120
How does a breakage of bonds affect the protein
It affects the shape and function
121
Tertiary structure of proteins
The secondary structure is folded into a more complex 3D shape
122
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
123
Quaternary structure of proteins
Made up from multi sub-unit proteins
| Most proteins only have one polypeptide chain and so no quaternary structure
124
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.
125
Why is haemoglobin a conjugated protein
It has a prosthetic group
126
What is a prosthetic group in a protein
An attachment not made from protein e.g. Haem
127
Structure of haemoglobin
All 4 polypeptide chains are attached to a haem group
128
What ions do haem contain
Fe 2+ ions and they bond with O2
129
Sub units of haemoglobin
2 alpha chains
2 beta chains
4 haem groups
130
Amylase
Alpha helix and beta sheets
Globular shape has an complementary active site
Active site holds Cl+ (co-factor - essential for correct action)
131
Insulin
2 polypeptides held together by disulphide bridges
One polypeptide has 21 amino acids and the other 30
Specific 3D shape complementary to glycoproteins receptor
132
Fibrous proteins
Form long strands and usually insoluble
Have structural roles in the body
Regular sequence of amino acids
Unreactive
133
Collagen
3 polypeptide chains wound around each other
Not easily stretched
Found in walls of arteries and tendons
134
Keratin
2 coiled polypeptide chains
Protect delicate things e.g. nails,claws, hair, feathers, hooves
Found in outer layers of skin cells (permeability)
135
Elastin
Linking tropelastin fibres
Coiled and can be stretched and recoiled
Used where stretching is required e.g. alveoli, walls of arteries, airways, bladder
136
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
137
Where are peptide bonds formed
Between the hydroxide from the amine group and the H from the carboxyl group
138
What happens when proteins are over heated
```
Increased kinetic energy
Molecule vibrates
H bonds break
Change in 3’ structure
Denatures
```
139
What is thin layer chromatography used for
Separation of proteins, carbs, vitamins or nucleic acids
140
Starch + amylase —>
Maltose
141
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
142
Test for reducing sugars if using a solid
Crush the solid w/ water
Filter out the solid
Continue test as normal
143
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
144
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
145
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
146
Glucose bisensors
Determines conc of glucose in a solution
Glucose oxidase catalyses oxidation of glucose at electrodes
Creates a charge which is then converted by a transducer
The electrical signal is then processed to work out the glucose conc.
147
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
148
Stationary phase in chromatography
Where the molecules cants move
| Paper in paper chromatography or silica gel on a glass plate in TLC
