2:1:2 Biological Molecules Flashcards
(124 cards)
1
Q
What is the bonding of water (H2O)
A
- The charge of water is electrically neutral but the sharing of electrons if uneven between the H and O atoms making a dipole
- The O attracts the electrons more strongly making a weak negatively charge region on the O and a weak positively charged region on the H
- H2O is a polar molecule
2
Q
What are hydrogen bonds
A
Weak bonds that form between the positive and negative regions of adjacent water molecules
3
Q
What properties of water are hydrogen bonds responsible for
A
- Solvent ability
- High specific heat capacity
- Less dense when solid
- High surface tension and cohesion
- Acts as a reagent
4
Q
Why is waters solvent abilities useful
A
- Ions and covalently bonded polar substances can dissolve in it allowing chemical reactions to occur (e.g. respiration)
- Metabolites can be transported efficiently
- Due to its polarity H2O is considered a universal solvent
5
Q
Why is waters specific heat capacity useful
A
- High specific heat capacity due to the many hydrogen bonds present
- Provides suitable habitats for organisms
- Can maintain a constant temperature which helps maintaining the optimal for enzymes
- H2O in blood plasma is vital to transfer heat and maintain a constant temperature
6
Q
Why is waters latent heat of vaporisation useful
A
- To change state large amounts of energy must be absorbed to beak the hydrogen bonds
- Allows only small amount of water to evaporate for heat loss providing a cooling effect
7
Q
Why is waters cohesion and adhesion ability useful
A
- Hydrogen bonds allows for strong cohesion between molecules so water can move through vessels and xylems, and also provides surface tension where water meets air
- Water molecules can adhere to each other to move as a unit
8
Q
What are monomers
A
Smaller units from which larger molecules are made
9
Q
What are polymers
A
Molecules made from a large number of monomers joined together in a chain
10
Q
What is polymerisation
A
The process of joining monomers together to make a long chain of molecules called a polymer (e.g. carbon compounds)
11
Q
What are macromolecules
A
Molecules that contain 1000 or more atoms and have a high molecular mass. Polymers can be macromolecules but not all macromolecules are polymers
12
Q
What happens to electrons during polymerisation
A
The valance electrons of two monomers that are close together are shared and form a covalent bond. This then repeats with other monomers
13
Q
What is a condensation reaction
A
When monomers combine together by covalent bonds and form polymers, whilst releasing water
14
Q
What is hydrolysis
A
Covalent bonds in polymers that are broken when water is added
15
Q
What are organic compounds
A
Compounds containing carbon (C) and hydrogen (H)
16
Q
Why are carbon atoms key to organic compounds
A
- Each carbon atoms forms 4 covalent bonds
- Carbon atoms can form straight, branched and ring chains
17
Q
What are carbohydrates
A
- All carbohydrates contain C, H and O, with H and O in a 2:1 ratio (hydrate)
18
Q
What are the function of carbohydrates
A
- Source of energy (glucose for respiration)
- Store of energy (glycogen in muscles)
- Structurally important (cellulose in plant cell walls)
19
Q
What is a monosaccharide and its function
A
- Single sugar monomer, all are reducing sugars (e.g. glucose 6C)
- Source of energy for respiration and building blocks for polymers
20
Q
What is a disaccharide
A
Sugar formed from two monosaccharide joined by a glycosidic bond (C-O-C) in a condensation reaction (e.g. maltose)
21
Q
What is a polysaccharide and its function
A
Polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction (e.g. glycogen), which are stores of energy
22
Q
What are lipids
A
Compounds that contain C, H and O, but the proportion of O is lower than carbohydrates. They are non-polar and hydrophobic
23
Q
What are the functions of lipids
A
- Source of energy to be respired
- Store of energy
- Insulating layer (e,g, thermal or electrical)
- Component of biological membranes
24
Q
What are the functions of proteins
A
- Cell growth and repair
- Structural (e.g. muscles)
- Act as character molecules
25
What is a nucleic acid
A compound containing C, H and O as well as including N in their bases and phosphate groups (e.g. DNA and RNA)
26
What is the function of nucleic acids
- Carry the genetic code of organisms
- Essential in control of processes (protein synthesis)
27
What is a reducing sugar
Sugars that can donate electrons (carbonyl group becomes oxidised) and become a reducing agent (e.g. glucose, fructose and galactose)
28
What are non-reducing sugars
Sugars that can’t donate electrons and can’t be oxidised (e.g. sucrose)
29
What are trioses
Monosaccharides with 3 carbons (e.g. glyceraldehyde)
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What are pentoses
Monosaccharides with 5 carbons (e.g. ribose)
31
What are hexoses
Monosaccharides with 6 carbons (e.g. glucose)
32
What is glucose
- Most common hexose monosaccharide
- Carbohydrate monomer
- C6H12O6
- Energy source
- Soluble
- Isomer
33
What is alpha glucose
A structurally different (isomer) form of glucose (forms a ring in aqueous solutions)
34
What is beta glucose
A structurally different (isomer) form of glucose (forms a ring in aqueous solution)
35
What is starch made of
Alpha and beta glucose
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What is glycogen made of
Only alpha glucose
37
What is cellulose made of
Only beta glucose
38
What is sucrose made of
Fructose and galactose
39
What is lactose made of
Galactose and alpha glucose
40
What is ribose
Pentose sugar that makes up RNA
41
What is deoxyribose
Pentose sugar that makes up DNA
42
What is maltose made of
2 alpha glucoses
43
Less sweet to sweetest monosaccharides
Galactose, glucose, fructose
44
What is a glycosidic bond
The bond that forms disaccharides and polysaccharides where the hydroxyl (-OH) groups from different saccharides form a strong covalent bond, and a molecule of water is removed due to the condensation reaction catalysed by enzymes
45
What is a 1,4-glycosidic bond
A glycosidic bond between the 1st and 4th carbon of the two different saccharides
46
What glycosidic bond is present in maltose
Alpha 1,4
47
What type of glycosidic bond is present in sucrose
Alpha 1,2
48
How are glycosidic bonds broken
When water is added via a hydrolysis reaction catalysed
49
What is amylose
- 1 of the 2 polysaccharides which makes up 10%-30% of starch
- Unbranched helix shaped chain with 1,4 glycosidic bonds between alpha glucose molecules
- Compact and resistant to digestion due to helix shape
50
What is amylopectin
- 1 of the 2 polysaccharides that makes up 70%-90% of starch
- 1,4 glycosidic bonds between alpha glucose and 1,6 glycosidic bonds creating a branch
51
What is glycogen
A polysaccharide consisting of 1,4 glycosidic bonds between alpha glucose and 1,6 glycosidic bonds between glucose molecules making it branched
52
What is cellulose
A polysaccharide consisting of 1,4 glycosidic bonds between beta glucose, which forms hydrogen bonds between its hydroxy groups making it strong
53
What is the function of starch
- Storage polysaccharide of plants stored as granules in plastids
- Takes a long time to digest
- Easily hydrolysed for use in cellular respiration - Compact for easy storage
- Insoluble so there’s no osmotic effect
54
What is the function of glycogen
- Glycogen is the storage polysaccharide of animals and fungi
- Present in liver and muscles as granules
- Highly branched so compact for easy storage
- Highly branched so many free ends for easy condensation and hydrolysis reactions
55
What is the function of cellulose
- Main structural component of cell walls due to many hydrogen bonds
- High tensile strength
- Support cell walls
- Cellulose fibres are freely permeable so water and solutes can leave or reach the cell surface membrane
56
Describe the test for reducing sugars
- Add excess of Benedict’s solution to test tube
- Heat test tube in a water bath
- Reducing sugar present will reduce the copper (II) sulphate to copper (I) oxide (insoluble in water)
- Positive result: colour change of blue to brick red
57
Describe the test for non-reducing sugars
- Add dilute HCl to the sample and heat in a water bath
- Neutralise with NaHCO3, then add more to make solution alkaline (check with red litmus paper)
- Benedict’s test as normal
- Positive result is no colour change
58
Describe the test for starch
- Add drops of potassium iodide to solution
- If starch is present, iodine molecules interact with the centre of starch molecules
- Positive result is orange/brown to blue/black colour change
59
What are triglycerides
Made up by 1 molecule of glycerol (alcohol) and 3 of fatty acid (RCOOH) monomers joined together by condensation reactions resulting in an ester bond
60
What is a saturated fatty acid
- Single C-C bonds
- Form solids (animal fat)
61
What is a monounsaturated fatty acid
- Has one double C=C bond
- Liquid so form oils
- Have cis (metabolised by enzymes) or trans (unable to form enzyme complexes so can’t be metabolised)
62
What is a polyunsaturated fatty acid
- Has more than one double C=C bond
- Has cis (metabolised by enzymes) and trans (unable to form enzyme complexes so can’t metabolise) forms
63
What is a phospholipid
- Formed from 1 molecule of glycerol, 2 of fatty acid, and 1 phosphate group
- Phosphate is polar so soluble in water so hydrophilic
- Fatty acid ‘tails’ are non-polar so hydrophobic
- Hydrophilic and hydrophobic so are called amphipathic
64
What are the roles of phospholipids
- Present in the bilayer of cell membranes
- Saturated phospholipids make the bilayer rigid
- Unsaturated phospholipids make the bilayer fluid
65
What are sterols and their roles
- Complex alcohol molecules (lipids) that are hydrophobic and hydrophilic (e.g. cholesterol)
- Used to stabilise the cell membranes and bilayer
66
What are ester bonds
- Esterification to form triglycerides results in an ester bond
- -OH from glycerol bonds with -COOH from the fatty acid to form a water molecule
- For each triglyceride molecule formed, three ester bonds are formed and 3 water molecules are released
67
Why are triglycerides used for energy storage
- Long hydrocarbon chains with little oxygen, allowing them oxidise and release energy used to produce ATP
- Store more energy per gram than protein
- Hydrophobic so don’t cause osmotic water uptake in cells so more can be stored
- Oxidation of C-H bonds release water that can be retain for when it’s needed
68
Why are triglycerides used for insulation
- Part of the composition of myelin sheath which surrounds nerve fibres
- Insulates to increase speed of transmission
- apart of the adipose tissue layer to insulate against heat loss
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Why are triglycerides used for buoyancy
- Fat tissue has low density to allow animals to float
70
Why are triglycerides used for protection
- Adipose tissue helps to protect organs
71
What are phospholipids used for
- Main component of cell membranes due to the hydrophobic fatty acid tails forming a hydrophobic core
- Hydrophilic phosphate heads forming hydrogen bonds with water allowing the cell membrane to be used to compartmentalise
- Controls membrane protein orientation via the weak hydrophobic reactions between them which hold proteins in the bilayer whilst also keeping it fluid
72
What is cholesterol used for
- Has hydrophobic and hydrophilic regions so can exist in the bilayer
- Affects the fluidity by disrupting the close-packing of phospholipids and increasing the rigidity of the bilayer
- Acts as a barrier to prevent water soluble substances diffusing
- Produce steroid- base hormones (e.g. testosterone)
73
Describe the test for lipids
- Emulsion test
- Add ethanol to a sample and shake
- Add the mixture to water
- Positive result is a milky emulsion on top of the water
74
What are proteins
Polypeptides made up of monomers called amino acids which determine the shape and therefore function of the protein
75
What do proteins form
- Enzymes
- Cell membrane proteins
- Hormones
- Immunoproteins
- Transport proteins
- Structural proteins
- Contractile proteins
76
What are amino acids
- Monomers of polypeptides
- 20 amino acids found in proteins common to all organisms
- Structure of amino acid includes a basic amine (-NH2) group and an acidic carboxylic acid (-COOH) group, with an H atom and a unique R group all attached to a central carbon
77
What is a peptide bond
- Covalent bonds that form between amino acids occurring in the ribosomes and catalysed by enzymes
- Hydroxyl (-OH) is lost from the carboxylic group of one amino acid and an H is lost from the amine group of another amino acid
- The remaining C and N of the to aminos bond releasing the molecule of water in a condensation reaction
- When water is added they can be hydrolysed and broken
78
What is a dipeptide
Formed by the condensation of 2 amino acids
79
What is a polypeptide
Formed by the condensation of 3 or more amino acids
80
What is the primary structure of a protein
- Sequence of amino acids bonded by peptide bonds which is determined by the DNA of the cell
- Structure is specific for each protein
81
What is the secondary structure of a protein
- Occurs when weak negatively charged N and O interact with weak positively charged H atoms to form hydrogen bonds
- H-bonds cause two shapes inside proteins: alpha helix, and beta pleated sheets
- H-bonds can be broken by heat and pH change
82
What is the alpha helix in the secondary structure of proteins
Occurs when hydrogen bonds form between every 4th peptide bond (between the O of the carboxylic group and the H of the amine group)
83
What is the beta pleated sheet of the secondary protein structure
- Forms when the protein folds so two parts of the polypeptide chain are parallel so hydrogen bonds can form
84
What is the tertiary structure of proteins
- Additional bonds forming between the R groups of amino acids
- Determines the protein function due to the different interactions between R groups making different protein configurations
85
What are the disulphide bonds in tertiary protein structure
- Strong covalent bonds formed between 2 cysteine R groups (only amino acid with S)
- Strongest bond within proteins but rare
- Stabalise the protein
- Form disulphide bridges
- Can only be broken by oxidation
86
What are the ionic bonds in tertiary structures of proteins
- Bonds formed between positively charged (amine -NH3+) and negatively charged (carboxylic acid -COO-) R groups
- Stronger than H-bonds but rare
- Broken by pH changes
87
What are hydrogen bonds in tertiary structures of proteins
- Bonds formed between strongly polar R groups
- Weakest bonds but most common
88
What are hydrophobic reactions in tertiary structures of proteins
Form between the non-polar (hydrophobic) R groups in proteins
89
What is the quaternary structure of proteins
Exists in proteins with more than one polypeptide chain working together (e.g. haemoglobin) which are each referred to as subunits of the protein
90
What are globular proteins
Proteins that are compact, spherical in shape and soluble in water
91
Why are globular proteins spherical and soluble
- When folding in their tertiary structure the non-polar hydrophobic R groups are in the centre and the hydrophilic R groups are on the outside of the protein
- This makes globular proteins soluble which allows them to be easily transported and also involved in metabolic reactions
- Some globular proteins are conjugated (contains a non-protein group) and contain a prosthetic (permanent non-protein group)
92
What is haemoglobin and its structure
- Globular protein which is O carrying and found in RBC’s
- Quaternary structure with 4 polypeptide chains (2 alpha globin and 2 beta globin) held together by disulphide bonds
- Each subunit has a prosthetic haem group containing an Fe2+ ion which can reversibly combine with O to form oxyhaemoglobin
93
What is the role of haemoglobin
- Binds to O in the lungs to transport it to tissue to be used in respiration
- Oxygen isn’t soluble in water but haemoglobin is, so haemoglobin can carry it effectively
- Each O molecule that binds alters the quaternary structure of the protein allowing it to have a higher affinity for oxygen
94
What are enzymes
- Biological catalysts that speed up the rate of chemical reactions without being used up
- Globular proteins
- Control metabolic pathways
95
What is insulin
- Hormone
- Globular protein important in controlling blood glucose concentration
- Consists of 2 polypeptide chains held together by three disulphide bridges , one with 21 amino acids and another with 30
96
What are fibrous proteins
- Long strands of polypeptide chains with cross linkages due to hydrogen bonds
- Little or no tertiary structure
- Large number of hydrophobic R groups, so insoluble
- Sequences are highly repetitive causing very organised structures
97
What is collagen
- Insoluble fibrous protein
- Most common structural protein providing structural support
- Component of connective tissue which forms: tendons, cartilage, ligaments, bones, teeth, skin, walls of blood vessels, cornea
98
What is the structure of collagen
- Formed of 3 polypeptide chains held together by hydrogen bonds to form a triple helix (tropocollagen)
- Each polypeptide chain is a helix shape containing about 1000 amino acids
- It’s primary structure consists of every third amino acid being glycerine allowing the chains to form a tight triple helix
- Cross links between R groups on amino acid hold collagen molecules together forming fibrils
- Fibrils are arranged to form fibres which are lined up with the forced they are withstanding
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What is the function of collagen
- Flexible structural protein forming connective tissues
- Great tensile strength due to many H-bonds in triple helix structure
- Staggered ends of collagen molecules in fibrils provide strength
- Stable protein due to high amounts of proline and hydroxyproline
- Long chains so insoluble in water
100
What is a cation
An ion with a +ve charge
101
What is an anion
An ion with a -ve charge
102
What is an inorganic ion
An ion that doesn’t contain carbon that occur in solution
103
What is a cofactor
Non-protein chemical compounds that are required for a protein to function
104
What is hydrogen ions symbol and function
- H+
- Hydrogen bonding
- ATP formation
- Control of blood pH
- Transport of CO2
105
What is calcium ions symbol and function
- Ca^2+
- Bone/enamel structure
- Cofactors in blood clotting
- Synaptic transmission of nerve impulses
- Muscle contraction
106
What is iron ions symbol and function
- Fe^2+/Fe^3+
- Transport if O2 via haemoglobin
- Transfer of electrons
107
What is sodium ions symbol and function
- Na+
- Electrolyte
- Nerve transmission
- Reabsorption of water in kidneys
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What is potassium ions symbol and function
- K+
- Electrolyte
- Nerve transmission
- Reabsorption of water in kidneys
- Opening of stomata
109
What is nitrate ions symbol and function
- NO3^-
- Source of nitrogen for plants
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What is hydrogen carbonate ions symbol and function
- HCO3^-
- CO2 transport in blood
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What is chloride ions symbol and function
- Cl-
- Maintaining pH balance during CO2 transport
112
What is phosphate ions symbol and function
- PO4^3-
- Component of cell membrane
- Component of bone
- Component of ATP and nucleic acids
113
What is hydroxide ions symbol and function
- OH-
- Bonding between biochemical molecules
114
Describe the test for proteins
- Biuret test where alkali and copper (II) sulphate react with peptide bonds present
- Add NaOH to solution to make alkaline
- Add Biuret reagent to solution
- Repeat with control solution
- Positive result: blue to lilac (observed on white tile)
- If the sample contains amino acids/dipeptide bonds there will be a negative result
115
What is the limitation of the tests for proteins, lipids etc
They are qualitative not quantitative so can’t give amounts of substance present
116
Describe how to produce a serial dilution to achieve quantitative results
- Taking a series of dilutions from a stock solutions where the concentration decreased by the same quantity under sterile conditions
117
Describe how to use a colorimeter to achieve quantitative results
- Colorimeter beams a wavelength of light through a sample and measures how much light is absorbed by it
- Colour filters control the light wavelength (e.g. if the sample is orange, a blue light filter will be used)
- Colorimeters must be calibrated by placing a cuvette with water in which absorbs no light
- Results plot a calibration curve
118
Describe how biosensors work
- Use catalysts to turn biological responses into electrical signals (e.g. blood glucose biosensors use glucose oxidase which uses FAD to oxidise glucose, forming FADH2, which is then oxidised by the electrode in the device to produce a current which is a measure of blood glucose)
- Drop of blood from the finger taken by a sterile lancet which is placed on a test strip and measured
119
What is chromatography
A technique that can be used to separate a mixture into individual components, due to the difference of solubility between solutes in a mixture
120
What is the mobile phase of chromatography
When the components in the mixture separate and depending on solubility move up the chromatography paper. Components with higher solubility spend more time in the mobile phase, so travel further
121
Describe the paper chromatography process
- A spot of mixture is left to dry on the chromatography paper
- The paper is then suspended in solvent
- The solvent travels through the paper, and the components in the mixture move up the paper at different speeds (large molecules = slow) producing a chromatogram
122
How does the chromatography process have to be altered for non-coloured molecules
The non-coloured molecules (e.g. monosaccharides) have to be stained and placed on the paper with dots of known standard solutions of other monosaccharides so they can be compared
123
What is the Rf value calculation
- Retardation factor
- Small Rf value indicates less soluble and large in size
- Rf = distance from original to centre of solute/distance from origin to solvent front
- Number should always be lower than 1
124
What is the order of chloroplasts pigments on a chromatography paper (from origin to solvent front)
- Chlorophyll B has the lowest Rf value
- Chlorophyll A has a low Rf value
- Xanthophylls have an Rf value in the middle
- Carotenoids have the highest Rf value
