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2.1.2 - Biological molecules Flashcards

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1
Q

Define the term ‘polar’ in relation to molecules

A

Polar molecules have regions of negativity and regions of positivity

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2
Q

Explain how polar molecules like water interact with each other

A
  • The positive and negative regions of the molecules attract each other and form hydrogen bonds
  • These bonds give water its cohesive properties - It moves as one body because the molecules are attracted to each other
  • These bonds also give water its adhesive properties, its molecules are attracted to other surfaces
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3
Q

What are hydrogen bonds ?

A
  • Hydrogen bonds are weak intermolecular forces that form between a hydrogen atom from one molecule and either N,O or F atom from another molecule
  • They break and reform between the constantly moving water molecules
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4
Q

What are the unique properties of water ?

A
  • High boiling point
  • Becomes less dense when it freezes
  • Cohesive properties
  • Adhesive properties
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5
Q

Due to water being a liquid at room temperature what four things does this allow it to do?

A
  • It provides a habitat for living things
  • Forms a major component of the tissues in living organisms
  • Provides a reaction medium for chemical reaction.
  • Provides a transport medium
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6
Q

What is the density of water like ?

A
  • Solid water has a lower density than liquid water, this is because of the hydrogen bonds formed
  • As water is cooled below 4 degrees, the hydrogen bonds fix the positions of the polar molecules slightly further apart from the average distance in the liquid state
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7
Q

What are the benefits of ice floating ?

A
  • Aquatic organisms have a stable environment in which to live on or under throughput the winter
  • Ponds and other bodies of water are insulated against extreme cold
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8
Q

What is surface tension in water ?

A
  • Hydrogen bonds are very cohesive, causing surface tension
  • Tension causes the surface of the liquid to contract so that it is very thin but very strong
  • It’s caused by attractive forces that hold the molecules of the liquid together
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9
Q

Explain how the ‘skin’ of surface tension of water enables a pond skater to inhabit the surface of water

A

The skin is caused as water molecules are more strongly cohesive to each other than to air, this skin supports thepond skater.

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10
Q

What is the boiling point of water like ?

A

The boiling point of water is unusually high because it has hydrogen bonds

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11
Q

What does the high SHC of water mean ?

A

It takes a lot of energy to increase the temperature of water and cause it to evaporate

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12
Q

What is cohesion and adhesion in water ?

A
  • It moves as one mass because the molecules are attracted to each other via electrostatic forces
  • Water molecules are attracted to other materials
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13
Q

What does cohesion and adhesion lead to ?

A
  • The acts of cohesion and adhesion result in exhibiting capillary action
  • This is he process by which water can rise up a narrow tube against the force of gravity
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14
Q

What are carbohydrates ?

A

Carbohydrates are groups of substances that provide energy and are used to build bodily structures

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15
Q

What are the functions of carbohydrates ?

A
  • Provide energy via respiration
  • Used to build bodily structures
  • They are a store of energy, glycogen and starch
  • Used in nucleic acids, deoxyribose and ribose, these are known as pentose saccharides
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16
Q

What is a Monosaccharide ?

A
  • A monosaccharide is a single unit of sugar

- For example, glucose, fructose and ribose

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17
Q

What is a disaccharide ?

A
  • A disaccharide is when two monosaccharides link together

- For example, Lactose and sucrose

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18
Q

What is a polysaccharide ?

A
  • A polysaccharide is when many monosaccharides are linked together.
  • For example, glycogen, cellulose and starch
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19
Q

What is glucose ?

A
  • Glucose molecules are polar and soluble in water, this is because of the hydrogen bonds between the hydroxyl groups and water molecules
  • This means glucose is dissolved in the cytosol of the cell
  • Glucose is a hexose monosaccharide due to the fact that it has six carbons
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20
Q

What are the two structural variations of glucose ?

A

Alpha (α) glucose and Beta (β) glucose

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21
Q

How does 𝛂 glucose differ from β glucose ?

A
  • The hydroxyl group (OH) on carbon 1 is in opposite positions
  • This affectsthe structure and properties of the polysaccharides when it bonds
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22
Q

What is a condensation reaction ?

A
  • A condensation reaction is one which forms a disaccharide
  • 2 monosaccharides join together
  • The two OH groups interact and bonds are broken
  • A new glycosidic bond is formed
  • Water is released
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23
Q

How is lactose formed ?

A
  • A condensation reaction between glucose and galactose

- Glucose + Galactose = Lactose

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24
Q

How is maltose formed ?

A
  • A condensation reaction between two glucose molecules

- Glucose + Glucose = Maltose

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25
Q

How is sucrose formed ?

A
  • A condensation reaction between glucose and fructose

- Glucose + Fructose = Sucrose

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26
Q

What is a hexose monosaccharide ?

A

A sugar that contains six carbons

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27
Q

What is a pentose monosaccharide ?

A

A sugar that contains five carbons

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28
Q

Which two pentose sugars are important components of biological molecules?

A
  • Deoxyribose, present in DNA molecules

- Ribose, present in RNA molecules

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29
Q

What are the properties and structure of starch ?

A
  • Made of amylose (mainly, 1-4 glycosidic bonds) and amylopectin(1-4 and some 1-6glycosidic bonds)
  • Insoluble, does not create a water potential gradient
  • Chemical energy store
  • Compact and ideal for storage
  • Easily digestible
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30
Q

What are the properties and structure of amylose ?

A
  • Long unbranched chains of alpha glucose
  • Joined by 1-4 glycosidic bonds
  • Insoluble (does not create water potential gradient)
  • Metabolically inactive
  • Compact and ideal for storage
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31
Q

What are the properties and structure of amylopectin ?

A
  • Long, branched chains of alpha glucose
  • Joined by 1-4glycosidic bonds (chains) and 1-6 glycosidic bonds (branches)
  • 1-6 branching points occur approximately one in every 25 glucose subunits.
  • Insoluble (do not affect water potential)
  • Compact and ideal for storage
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32
Q

What do 1-4 glycosidic bonds cause ?

A

Chains

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33
Q

What do 1-6 glycosidic bonds cause ?

A

Branches

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34
Q

What are the benefits of coiling and branching in polysaccharides ?

A
  • Makes them very compact which is ideal for storage.
  • Allows for free ends where glucose can be added or removed quickly. This speeds up the process of storing/releasing glucose molecules required.
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35
Q

What are the properties and structure of glycogen ?

A
  • Short, branched chains of alpha glucose
  • Joined by 1-4glycosidic bonds (chains)and 1-6 glycosidic bonds (branches)
  • Compact so ideal for storage
  • Insoluble
  • Branchingmeans many free ends so glucose can be released (or stored) quickly
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36
Q

What is the function of glycogen ?

A
  • Energy store in animals

- Stores soluble glucose until it is needed

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37
Q

What are the similarities between amylopectin and glycogen ?

A
  • Insoluble
  • Branched
  • Compact so ideal for storage
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38
Q

Describe the structure and properties of cellulose

A
  • Long, unbranched chains ofbeta(β)glucose
    • Every alternatebeta(β)glucose molecule is turned upside down.
    • Forms straight cellulose chains
    • Contains 1-4 glycosidic bonds
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39
Q

What are cellulose chains ?

A
  • The cellulose chains are linked by hydrogen bonds forming strong fibres called microfibrils, microfibrils are compact
  • Microfibrils join to make macrofibrils, which combine to make fibres
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40
Q

Describe the function of cellulose

A
  • Cellulose is a fibre necessary for a healthy digestive system. This is due to the fact that it is very hard to break down.
  • Celluloseprovides structural support for cells in plants
  • e.g. cellulose cell wall in plants
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41
Q

What is a hydrolysis reaction ?

A
  • A hydrolysis reaction is how a disaccharide is broken down
  • Addition of water to hydrolyse the disaccharide into (useable) monomers
  • Reactions are catalysed by enzymes
  • These are the opposite of condensation reactions that form glycosidic bonds.
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42
Q

What test is used for the presence of starch ?

A

The iodine test

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43
Q

Explain the iodine test

A
  • Add iodine dissolved in potassium iodide solution to test sample
  • If starch is present the colour will change from brown/orange to dark blue/black
  • If no starch is present, the colour stays brown/orange
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44
Q

What test is used for the presence of protein ?

A

The Biuret test

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45
Q

Explain the Biuret test

A
  • First step is to add few drops of sodium hydroxide solution this is because the solution has to be alkaline
  • Next add the copper (ii) sulphate solution
  • If a protein is present the solutionturns purple
  • If no proteinis presentthe solutionstays blue
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46
Q

What does the Biuret test really discover?

A

Peptide bonds in proteins

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47
Q

How is the colour formed in the Biuret test?

A

A complex is formed between the nitrogen atoms in a peptide chain and Cu2+ ions

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48
Q

What test is used for the presence of lipids ?

A

The emulsion test

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49
Q

Explain the emulsion test

A
  • Shake the test sample which contains ethanol for about 1 minute then pour solution into cold water
  • If lipid is present, solution turns milky
  • If there is no lipid present the solution stays clear
  • The more lipid present, the more noticeable the milky colour
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50
Q

What is a reducing sugar ?

A
  • A sugar which can give electrons to other molecules

- Reducing sugars include all monosaccharides and some disaccharides

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51
Q

What is used to test for reducing sugars ?

A

The Benedict’s test, using Benedict’s solution

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52
Q

Explain the Benedict’s test

A
  • Add Benedict’s reagent to the sample and heat it in a water bath
  • If a coloured precipitate is formed than the test is positive and there is a reducing sugar present
  • Colour of precipitate changes from: blue - green - yellow - orange - brick red
  • The higher the concentration of reducing sugar, the further the colour change goes
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53
Q

What causes the change in colour of the Benedict’s solution?

A

The Cu2+ ions in the Benedict’s solution reduce to Cu+ ions which give it that orange colour

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54
Q

What is another way to test for reducing sugars ?

A
  • Reagent strips
  • The advantage to reagent strips is that with the use of a colour coded chart, the concentration of the sugar can be determined
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55
Q

What is the test for non reducing sugars ?

A

Benedicts test

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56
Q

What must first happen to the sugar solution before it can tested for non-reducing sugars?

A
  • It must be boiled with hydrochloric acid to hydrolyse the bonds and free up the reducing sugar group e.g. Sucrose split into glucose and fructose
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57
Q

Why is Sodium hydrogen carbonate added after adding HCl ?

A

To neutralise the acid

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58
Q

What are the non-reducing sugars Benedict’s test results?

A
  • Positive result, forms coloured precipitate.
  • Colour changes:
    • Blue - Green - Yellow - Orange - Red
  • Negative result, stays blue so no sugar present
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59
Q

How can colorimetry be used to calculate the concentration of reducing sugar present ?

A
  • A colorimeter is a piece of equipment that quantitatively measures the absorbance, or transmission, of light of a coloured solution.
  • The more concentrated a solution is the more light it will absorb and the less light it will transmit.
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60
Q

What are lipids ?

A
  • Lipids are molecules containing carbon, hydrogen and oxygen
  • They are non polar and insoluble in water
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61
Q

What are the three types of lipids ?

A
  • Triglycerides
  • Phospholipids
  • Sterols
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62
Q

How do u test for lipids ?

A

Emulsion tests

63
Q

What is a triglyceride ?

A

A triglyceride is made from three fatty acids (Carboxylic Acid) and a glycerol (Alcohol)

64
Q

What are the functions of triglycerides ?

A
  • Protection of vital organs
  • Thermal insulation
  • They form the myelin sheath around some neurones, acting as electrical insulators
  • As a water source from the respiration of lipids
  • Components of cell membranes
65
Q

Why are they useful for storage ?

A
  • Can be stored in a compact way

- They are not water soluble

66
Q

How do triglycerides compare to carbohydrates in terms of energy ?

A

Triglycerides release more energy per gram

67
Q

Why do we not use triglycerides as energy ?

A

Too much energy is required to break them down so it is not efficient

68
Q

Explain the synthesis of a triglyceride

A

The hydroxyl groups interact, leading to the formation of three water molecules and three ester bonds between the fatty acids and the glycerol

69
Q

Explain the hydrolysis of a triglyceride

A

To break down a triglyceride you have to add 3 H2O molecules to hydrolyse it

70
Q

What is a saturated fatty acid ?

A

Fatty acid chains that have no double bonds present between the carbon atoms

71
Q

What is an unsaturated fatty acid ?

A

Fatty acids with double bonds between some carbon atoms

72
Q

What does a double bond cause in the chain ?

A

Double bond causes the molecule to kink or bend

73
Q

Why are unsaturated fatty acids liquid at room temp ?

A
  • The double bonds cause the molecule to bend so they can’t pack closely together
  • Therefore they are oils and not fats
74
Q

What is a phospholipid ?

A
  • Phospholipids are modified triglycerides

- One of the fatty acid chains in a triglyceride is replaced with a phosphate group to make a phospholipid

75
Q

How are phospholipids formed ?

A

A condensation reaction between a glycerol molecule, 2 fatty acids, and a phosphate group

76
Q

What bonds are involved in the formation of a phospholipids ?

A

Ester bonds

77
Q

What properties does the phospholipid head have ?

A

The head is charged and polar due to the phosphate ions therefore it is hydrophilic and attracts water

78
Q

What properties does the phospholipid tail have ?

A

Tail is not charged and non polar due to the long chain hydrocarbons therefore it is hydrophobic and repels water

79
Q

How do phospholipids interact with water ?

A
  • They will form a layer on the surface with heads in the water and the tails sticking out of the water.
  • They are called surfactants.
80
Q

What is a phospholipid bilayer ?

A

The heads protect the tails from the water the tails point inwards and the heads point outwards

81
Q

What does the phospholipid bilayer allow ?

A
  • They are able to separate an aqueous environment in which cells usually exist from the aqueous cytosol within cells
  • They play a key role in forming cell membranes
82
Q

Explain the differences between phospholipids and triglycerides

A
  • Triglycerides contain 3 fatty acids but phospholipids only contain two and a phosphate group
  • Triglycerides contain 3 ester bonds but phospholipids only contain 2
  • Phospholipids have a hydrophilic head
83
Q

What are sterols ?

A

Sterols are another type of lipid

84
Q

What is the structure of sterols ?

A

They are complex alcohol molecules based on a four carbon ring structure with a hydroxyl group at one end

85
Q

Where are the sterols manufactured ?

A

They are manufactured in the liver and intestines

86
Q

What are the functions of sterols ?

A
  • Adds stability to the cell membrane
  • Regulates fluidity by keeping the membrane fluid at low temperatures and stopping them becoming too fluid at high temperatures
  • Used to make steroid hormones
87
Q

How does cholesterol sit in phospholipid bilayers?

A

With the hydroxyl group in contact with the phosphate head

88
Q

Which part of the sterol is hydrophilic ?

A

The hydroxyl group

89
Q

Which part of the sterol is hydrophobic ?

A

The four carbon ring structure and the rest of the body

90
Q

What are the basic units of proteins ?

A

Amino acids

91
Q

How many common amino acids are there ?

A
  • There are 20 common amino acids in the body

- There are 3.2 million different ways they could join and bond together

92
Q

What is a special feature of amino acids ?

A
  • They are amphoteric

- They act as a pH buffer, helping to stabilise the pH of your blood

93
Q

Why are amino acids able to be amphoteric ?

A

The reason they can act as a buffer is because if the blood is not acidic enough the hydroxyl group can let a hydrogen ion go. If the blood is too acidic its got too many hydrogen ions, the amine group can take in some of these hydrogen ions.

94
Q

What are the functions of proteins ?

A
  • Enzymes
  • Signal; hormone proteins
  • Structural; keratin and collagen
  • Contractile; spindle fibres, actin and myosin in muscles
  • Storage; albumin present in eggs and casein present in milk
  • Transport; haemoglobin and myoglobin
  • Defensive; antibodies
95
Q

What type of reaction occurs to form a protein from 2 amino acids?

A

Condensation

96
Q

What catalyses the reaction of two amino acids ?

A

Peptidyl transferase

97
Q

What is produced in the reaction of two amino acids ?

A

A dipeptide and water

98
Q

What type of bond is formed from the synthesis of a protein ?

A

Peptide bond

99
Q

Between which parts of the amino acid molecules does the condensation reaction between two amino acids occur?

A

The carboxyl group of one amino acid and the amine group of another amino acid

100
Q

What is the primary structure of a protein ?

A

The sequence of amino acids

101
Q

What type of bonding holds the primary structure of a protein together?

A

Peptide bonds

102
Q

What shape is the primary structure of a protein?

A

Linear

103
Q

What forms the secondary structure of a protein?

A

The folding of the primary structure

104
Q

What type of bonds hold together the secondary structure of a protein?

A

Hydrogen bonds

105
Q

In the secondary structure, what do hydrogen bonds form between?

A
  • Between a hydrogen (H) atom and another electronegative atom bearing a lone pair of electrons
  • Hydrogen and either Oxygen, Nitrogen or Fluorine
106
Q

What are the two possible shapes of the secondary structure?

A
  • Beta pleated sheet is when the polypeptide chains lie parallel to one another. Hydrogen bonds hold it together.
  • Alpha helix is formed due to the hydrogen bonds pulling the amino acid chains together
107
Q

Between which amino acids do the hydrogen bonds form?

A

The hydrogen bonds form with the fourth amino acid along the chain.

108
Q

What is the tertiary structure formed by?

A

The folding of the secondary structure

109
Q

Why do proteins fold at the tertiary level of structure?

A

Interactions between the R - groups

110
Q

What are the 4 types of bond formed at the tertiary level of structure?

A
  • Hydrogen bonds
  • Ionic bonds
  • Disulphide bonds
  • Hydrophobic and hydrophilic interactions
111
Q

What do ionic bonds form between?

A

Oppositely charged ions

112
Q

What do hydrogen bonds form between?

A

Between a hydrogen (H) atom and another electronegative atom bearing a lone pair of electrons

113
Q

What do disulphide bridges form between?

A

Sulphur atoms contained within separate R groups

114
Q

What do hydrophobic and hydrophilic interactions form between?

A

Polar and non polar R - groups

115
Q

What forms the quaternary structure?

A
  • Formed by the interaction of more than one tertiary protein
  • Two or more tertiary proteins being held together by different bonds
116
Q

What type of bonds holds together the quaternary structure?

A
  • Ionic
  • Hydrogen
  • Disulphide
  • Hydrophobic and Hydrophilic interactions
117
Q

Explain the breakdown of peptides

A
  • Water molecule is used to break the peptide bond in a hydrolysis reaction, reforming the amine and carboxylic acid group
  • Protease enzymes catalyse the reverse reaction - turning peptides back into their constituent amino acids
118
Q

What is a globular protein?

A

Spherical, water soluble protein

119
Q

What are globular proteins used for ?

A
  • Essential for regulating processes such as :

- Chemical reactions, immunity and muscle contractions; along with many others

120
Q

Give 3 characteristics of globular proteins

A
  • Compact
  • Water soluble
  • Roughly spherical
121
Q

Why are globular proteins water soluble ?

A
  • Hydrophilic R-groups are on the outside, this allows for them to be soluble in water
  • The tertiary structure is folded so that the hydrophobic R-groups are kept away from the aqueous environment
122
Q

What are some examples of globular proteins ?

A
  • Insulin
  • Haemoglobin
  • Catalase
123
Q

What is the function of insulin ?

A
  • Hormone involved in the regulation of blood glucose concentration.
  • Stored as energy for later use.
  • When there is a high glucose concentration in the blood, insulin tells the body to store leftover glucose in the liver
124
Q

Where is insulin produced ?

A

Produced in the pancreas

125
Q

Why is it beneficial for insulin to be water-soluble?

A

Hormones are transported in the blood so must be water soluble

126
Q

What are conjugated proteins ?

A

Conjugated proteins are globular proteins that contain a prosthetic group

127
Q

What is a prosthetic group ?

A

A non protein component

128
Q

State some examples of prosthetic groups

A
  • Haem groups, include iron (II) ions
  • Different metal ions
  • Vitamin molecules
129
Q

Define a simple protein

A

A simple protein is one without a prosthetic group

130
Q

Give 2 examples of conjugated proteins

A
  • Haemoglobin

- Catalase

131
Q

What is the function of haemoglobin ?

A
  • Carries oxygen around the body in red blood cells
  • Carries it from the lungs to the cells that need it
  • Stores, transports and releases oxygen
132
Q

What is haemoglobin made up of ?

A
  • 4 subunits
  • 2 alpha helixes
  • 2 beta pleated sheets
133
Q

What prosthetic group does each subunit of haemoglobin contain?

A

Haem group

134
Q

What is a haem group ?

A

It is a prosthetic group that contains Iron (II) ions

135
Q

What is the function of the haem groups in haemoglobin ?

A

The iron (II) ions in haem are able to combine reversibly with an oxygen molecule which allows haemoglobin to transfer oxygen

136
Q

What is the function of catalase ?

A
  • Break down of hydrogen peroxide which is otherwise harmful to cells
  • Protects the cell from oxidative damage
137
Q

What is catalase made up of ?

A
  • It is made up of 4 tetrahedral polypeptide chains, each of which have a haem group
138
Q

What prosthetic group does catalase include ?

A

Haem group

139
Q

What is the function of haem groups in catalase ?

A

It allows the iron (II) ions to interact with hydrogen peroxide and speed up its breakdown

140
Q

What are fibrous proteins ?

A
  • They are long, insoluble, structural proteins

- This is because they have a high amount of amino acids

141
Q

How does the repetitive amino acid sequences affect the properties of fibrous proteins?

A
  • Gives them more organised structures

- Makes strong molecules that do not fold into complex 3D shapes

142
Q

Give 3 examples of fibrous proteins

A
  • Keratin
  • Collagen
  • Elastin
143
Q

Where is Keratin found ?

A

Keratin is found mainly in hair, skin and nails

144
Q

Which amino acid does keratin contain in a high proportion?

A

Cysteine, contains sulphur

145
Q

What type of bonding occurs in keratin ?

A

Disulphide bonds

146
Q

What does the amount of disulphide bonds determine ?

A
  • It determines the flexibility, the fewer bonds the more flexible it is
  • Hair is more flexible compared to nails because it has fewer bonds compared to nails
147
Q

What does the high amount of sulphur lead to in keratin ?

A

It makes it insoluble, inflexible and strong

148
Q

Where is Elastin found ?

A

In the walls of blood vessels and lungs

149
Q

What makes up elastin ?

A
  • Quaternary structure made from many molecules called tropoelastin
  • This makes a very large insoluble and stable, cross linked structure.
150
Q

What is the function of elastin ?

A

Elastin gives structures flexibility to expand when they need to and then also return back to their original position

151
Q

Why is it beneficial for tissues to contain elastin?

A

It confers strength and elasticity

152
Q

Where is collagen found ?

A

In the skin, tendons, ligaments, and nervous system

153
Q

What is the structure of collagen ?

A

All forms of collagen are made up of three polypeptides wound together in a long and strong rope-like structure

154
Q

What property does collagen have ?

A
  • Long and flexible under low stress

- Insoluble

Biology (30 decks)

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