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A level OCR Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

Covalent bonds are…

A
  • Formed when atoms share electrons

- Strong Bonds

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2
Q

Hydrogen bonds are…

A
  • A weak interaction that occurs when a negatively charged atom is bonded to a positively charged atom
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3
Q

Water makes up… of mammals

A

60-70%

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4
Q

Water makes up… of plants

A

90%

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5
Q

Where did life originate?

A

In Water

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6
Q

Water is a polar molecule because?

A

It is made up of two positively charged hydrogen atoms and one negatively charged oxygen atom

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7
Q

What bonds makeup water

A
  • Covalent

- Hydrogen

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8
Q

Covalent bonds are formed between… in water

A

Between oxygen and hydrogen (O-H) with electrons shared between them

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9
Q

Hydrogen bonds are formed between… in water?

A

Between water molecules

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10
Q

How many water molecules can form clusters?

A

Up to four

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11
Q

Do water molecules form clusters?

A

Yes, they break and reform all the time

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12
Q

What are the key features of water?

A
  • Good solvent
  • High specific heat capacity
  • High latent heat of vaporisation
  • High cohesion
  • Reactive
  • Incompressible
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13
Q

What is Metabolism

A

The sum/total of all biochemical reactions in the body

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14
Q

What is needed to maintain a healthy body?

A
  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acid
  • Vitamins and minerals
  • Water
  • Fibre
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15
Q

What are the most common elements in living organisms?

A

Carbon, Hydrogen, Nitrogen, Oxygen

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16
Q

What are macromolecules made up of?

A

Repeating subunits that are joined end to end, they are easy to make

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17
Q

What is polymerisation?

A

The making of polymers

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18
Q

What does Anabolism do and require?

A
  • Builds smaller molecules into complex molecules

- Requires energy

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19
Q

What does Catabolism do and releases?

A
  • Breakdowns a complex molecule into simple molecules

- Releases energy

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20
Q

What happens in a Condensation reaction?

A
  • Water molecule is released
  • New covalent bond is formed
  • Larger molecule is formed by the bonding together of smaller molecules
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21
Q

What happens in a Hydrolysis reaction?

A
  • Water molecule is used
  • Covalent bond is broken
  • Smaller molecules are formed by the splitting of a larger molecule
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22
Q

What do carbohydrates contain?

A

Carbon, Hydrogen, Oxygen

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23
Q

What is the general formula for a carbohydrate?

A

Cx(H2O)y

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24
Q

What are the three main groups of carbohydrates?

A
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
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25
Q

What are the three main types of monosaccharides?

A
  • Trioses (3C)
  • Pentoses (5C)
  • Hexoses (6C)
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26
Q

What is glucose made up of?

A

A chain of atoms long enough to close up on itself

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27
Q

What do the chain of atoms in glucose make?

A

A stable ring structure

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28
Q

Carbon atom 1 joins to the…

A

O on Carbon atom 5

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29
Q

The six-sided structure from is known as a

A

Pyranose ring

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30
Q

What does a-glucose look like>

A

First cabon is bonded to O, H, OH, and second carbon
Second carbon is bonded to H, OH, and third carbon
Third carbon is bonded to H, OH, and fourth carbon
Fourth carbon is bonded to OH, H, and fifth carbon
Fifth carbon is bonded to H, O, sixth carbon
Sixth carbon is CH2OH
Oxygen is bonded to both fifth carbon and first carbon

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31
Q

Which way round is the H and OH on first carbon in a-glucose?

A

H on top

OH on bottom

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32
Q

What does b-glucose look like?

A

First cabon is bonded to O, H, OH, and second carbon
Second carbon is bonded to H, OH, and third carbon
Third carbon is bonded to H, OH, and fourth carbon
Fourth carbon is bonded to OH, H, and fifth carbon
Fifth carbon is bonded to H, O, sixth carbon
Sixth carbon is CH2OH
Oxygen is bonded to both fifth carbon and first carbon

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33
Q

Which way round is the H and OH on first cabon in a B-glucose?

A

OH on top

H on bottom

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34
Q

What is an Isomer?

A

They posses the same molecular formula but differ in arrangement of atoms.

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35
Q

a-glucose and B-glucose are different arrangments of glucose so they are?

A

Isomers

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36
Q

What are Disaccharides?

A

Two monosaccharides combined

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37
Q

How are disaccharides formed?

A

Condesation reaction occurs, so a water molecule is lost and a 1,4 glycosidic bond is formed between the monosaccharides

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38
Q

To break a disaccharide, what is needed?

A

The addition of water, hydrolysis

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39
Q

What are polysaccharides?

A

Many monosaccharides

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40
Q

Polysaccharides are … because of size?

A

Insoluble

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41
Q

Are polysaccharides sugars?

A

No

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42
Q

Starch, glycogen and cellulose are examples of?

A

Polysaccharides

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43
Q

What is starch made up of?

A

Mix of Amylose and Amylopectin

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44
Q

Starch granules are … in water?

A

Insoluble

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45
Q

What is starch used for?

A

Storage in plants

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46
Q

Where is strach stored in plants?

A

Chloroplasts or storage organs

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47
Q

What are the chains like in Amylose?

A

Long, unbranching

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48
Q

What is the bond in Amylose?

A

1,4 glycosidic bond

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49
Q

Which reaction forms amylose?

A

Condesation reaction

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50
Q

What structure are the chains in, in amylose?

A

Helical Structures

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51
Q

What are the chains like in Amylopectin?

A

Shorter than amylose, branches

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52
Q

What are the bonds in Amylopectin?

A
  • 1,4 glycosidic bonds

- 1,6 glycosidic bonds

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53
Q

What do the 1,6 glycosidic bonds do in Amylopectin?

A

Form the branches

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54
Q

What is glycogen used for?

A

Storage in animals

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55
Q

Where is glycogen stored in animals?

A

Liver, Muscles

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56
Q

There are more … containing a … number of … molecules than …

A

Branches, Smaller, Glucose, Amylopectin

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57
Q

What isomer of glucose does glycogen have?

A

Alpha

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58
Q

What isomer of glucose does amylopectin and amylose have?

A

Alpha

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59
Q

What are the bonds in glycogen?

A
  • 1,4 glycosidic bonds

- 1,6 glycosidic bonds

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60
Q

What do the 1,6 glycosidic bonds do in glycogen?

A

Form the branches

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61
Q

Energy … molecules that take up … space due to their … shape. Helps to prevent a too … concentration of … in cells.

A

Storage, Little, Compact, High, Glucose

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62
Q

Why is cellulose the most abundant organic molecule on the planet?

A

Presence in cell walls

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63
Q

What is cellulose rate of breakdown?

A

Slow

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64
Q

What isomer of glucose does cellulose have?

A

B-glucose

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65
Q

How many B-glucose molecules does cellulose contain approximately?

A

10,000

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66
Q

What is the chain like in cellulose?

A

Long, Unbranching

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67
Q

Many chains run … to each other and have … linkages between the …, giving increased …

A

Parallel, Cross, Chains, Stability

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68
Q

What bond is in cellulose

A

1,4 glycosidic bonds

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69
Q

What bond forms the links between chains in cellulose?

A

Hydrogen

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70
Q

What do the hydrogen bonds do in cellulose

A

Form cross-links between chains which collectively give the structure increased strength

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71
Q

B-glucose molecules have to be rotated how many degrees?

A

180° relative to the other B-glucose molecules

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72
Q

Cellulose forms microfibrils because?

A

It becomes tightly cross-linked with each other

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73
Q

True or false: Does cellulose have high contractile strength?

A

False. Cellulose has a high tensile strength

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74
Q

What bond form cellulose fibres?

A

Hydrogen bonds

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75
Q

Which fibres form cellulose fibres?

A

Microfibrils

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76
Q

What can you test for when testing for the presence of a carbohydrate?

A
  • Starch
  • Reducing sugar
  • Non-reducing sugar
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77
Q

Which of the three main groups of carbohydrates are always reducing sugars?

A

All monosaccharides

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78
Q

What group do reducing sugars have?

A

Aldehyde group (H-C=O)

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79
Q

What does the aldehyde group in reducing sugars do

A

It contributes an electron to the sugar

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80
Q

Reducing sugars become?

A

Oxidised

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81
Q

How to test for Starch?

A

Iodine test

  • Add iodine solution to test sample
  • If sample turn blue-black then starch is present
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82
Q

Why does the test for starch work?

A

Iodine gets trapped in the amylose helix which stains it

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83
Q

How to test for reducing sugar?

A

Benedicts test

  • Add sample to boiling tube
  • Add benedicts solution
  • Heat in a water bath at 80­° for 3 minutes
  • If a red-orange precipitate forms then a reducing sugar is present
  • If there is no colour change then a reducing sugar is not present
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84
Q

Why does the benedicts test work for reducing sugars?

A

If added to a reducing agent (reducing sugar), Cu^2+ ions are reduced to Cu^+, which gives the red colour of Copper (I) sulphate

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85
Q

If lipids are not polymers, then what are they?

A

Large molecules

86
Q

What are the features of lipids?

A
  • Have few Oxygen atoms
  • Have many Carbon and Hydrogen atoms
  • It is hydrophobic
  • Less dense than water
87
Q

What does hydrophobic mean?

A

Repels/fails to mix with water

88
Q

What does hydrophilic mean?

A

Mixes with water

89
Q

What are the two important groups of lipids?

A
  • Triglycerides

- Phospholipids

90
Q

What are the two sub-groups of triglycerides?

A

Fats

Oils

91
Q

What state is fat in at room temperature?

A

Solid

92
Q

What state is oil in at room temperature?

A

Liquid

93
Q

What are the functions of lipids?

A
  • Source of energy
  • Store of energy
  • Biological membranes
  • Thermal insulators/Insulation
  • Buoyancy
  • Protection (Cuticle of a leaf/Internal organs)
  • Metabolic source of water
  • Hormones
94
Q

What does the structure of glycogen look like?

A

3 carbon atoms each bonded to one H and one OH

The two end carbon atoms are bonded to an extra H

95
Q

What does the structure of a fatty acid look like?

A 
An acid (Carboxyl) group at one end (COOH), attached to a hydrocarbon tail
Hydrocarbon chain (2-20 carbons long)
Can be either saturated or unsaturated
96
Q

What is a saturated fatty acid?

A

No double bonds between carbon atoms on the carbon skeleton (C-C)

97
Q

What is an unsaturated fatty acid?

A

One or more double bonds between carbon atoms on the carbon skeleton (C-C or C=C)

98
Q

What is a polyunsaturated fatty acid?

A

Has more than one double bond

99
Q

What is a monosaturated fatty acid?

A

Has only one double bond

100
Q

What do animal lipids tend to be and occur as?

A

Saturated

Fats

101
Q

What do plant lipids tend to be and occur as?

A

Unsaturated

Oils

102
Q

What is the most common form of lipid?

A

Triglycerides

103
Q

What are triglycerides made up of?

A

Three fatty acids and one glycerol molecule

104
Q

Glycerol is a type of…?

A

Alcohol

105
Q

What type of reaction occurs between the three OH groups on a glycerol molecule and the carboxyl groups of a fatty acid?

A

Condensation

106
Q

What type of bond is formed between glycerol and the fatty acids?

A

Ester bond

107
Q

Features of Triglycerides

A
  • Insoluble in water
  • Soluble in some organic solvents
  • Non-polar (not charged)
  • Hydrophobic
108
Q

What are the roles of triglycerides?

A
  • Energy reserve
  • Insulator against heat loss
  • Buoyancy
  • Protection (vital organs)
  • Metabolic source of water
109
Q

What are phospholipids?

A

A special type of lipid

110
Q

What is one of the fatty acids replaced by in phospholipids?

A

A phosphoric acid

111
Q

What is phosphoric acid (in terms of water)?

A

Hydrophilic, it is the head of the phospholipid

112
Q

What are the hydrophobic tails?

A

Fatty acids

113
Q

Cholesterol is a … molecule

A

Small

114
Q

The … group is polar

A

-OH

115
Q

The … rings and the … tail are non-polar

A

4 carbon rings, Hydrocarbon

116
Q

What are the functions of cholesterol?

A
  • Found in biological membranes
  • Steroids are made from cholesterol
  • Excess cholesterol forms gallstones and causes atherosclerosis in blood vessels
117
Q

How much of the dry mass of cells is protein?

A

50%

118
Q

What are the important functions of proteins?

A
  • Cell membranes

- Enzymes

119
Q

What are proteins made of?

A

Amino acids

120
Q

How many amino acids are there?

A

20

121
Q

What changes between amino acids?

A

The residual group (R group)

122
Q

A single chain of amino acids makes a?

A

Polypeptide

123
Q

What types of bonds are between amino acids in a polypeptide chain?

A

Peptide bonds

124
Q

Wha is the structure of an amino acid?

A

Amine group (NH2)
Carboxyl group (COOH)
R group
Hydrogen

These are joined at the same C atom in the middle of the amino acid

125
Q

What reaction forms a peptide bond?

A

Condensation

126
Q

What is the primary structure?

A

It is the proteins amino acid sequence

127
Q

What determines the primary structure?

A

The gene that codes for the polypeptide

128
Q

What is the secondary structure?

A

Polypeptides become twisted or coiled

129
Q

What structures does the secondary structure occur in?

A
  • Alpha helix (Right-handed)

- Beta-pleated sheet

130
Q

What holds the coils in place in an alpha helix?

A

Hydrogen bonds

131
Q

What do the hydrogen bonds give to a protein molecule?

A

Stability

132
Q

What is a tertiary structure?

A

The folding of the polypeptide to give a move complex 3-D shape

133
Q

The tertiary structure is … to the … of the polypeptide

A

Specific

Function

134
Q

What are the three bonds and one interaction that helps to hold the folded protein in its precise shape?

A
  • Hydrogen bonds
  • Ionic bonds
  • Disulphide bonds
  • Hydrophobic interactions
135
Q

Where are the hydrogen bonds in a tertiary structure?

A

Between polar groups

  • Electronegative oxygen atoms of the -CO
  • Electropositive hydrogen atoms on -OH/-NH
136
Q

Where are the disulphide bonds in a tertiary structure?

A

Between sulfur-containing R-groups

137
Q

What type of bond are disulphide bonds?

A

Covalent

138
Q

How do disulphide bonds make the tertiary protein structure very stable?

A

By forming strong links

139
Q

How can disulphide bonds be broken?

A

Reducing agents

140
Q

Where are ionic bonds in a tertiary structure?

A

Between R groups

141
Q

The ionic bonds in a tertiary ionise to form…

A

Positively and negatively charged groups that attract each other

142
Q

Where do hydrophobic interactions occur in a tertiary structure?

A

Between non-polar side chains of a protein molecule

143
Q

Bonds form between …, … R groups on amino acids in a tertiary structure

A

Non-polar

Hydrophobic

144
Q

What attraction reinforces the interactions when the two hydrophobic molecules are close together?

A

Van der Waals attractions

145
Q

What do Van der Waal attractions provide to a tertiary structure?

A

Weak bonds

146
Q

Electrons are… and …?

A

Always in motion

Not evenly distributed around a molecule

147
Q

The constant movement of electrons and the electrons not being evenly distributed around a molecule causes?

A

Areas of positive and negative charges which are continuously changing

148
Q

What do Van der Waals attractions allow?

A

Molecules to ‘stick’ to one another

149
Q

What is a quaternary structure?

A

The association of different polypeptide chains bonded together to form intricate shapes

150
Q

What do quaternary structures sometimes contain?

A

Prosthetic groups

151
Q

What are prosthetic groups?

A

A permanent part of a protein molecule, but not made of amino acids

152
Q

What are globular proteins?

A

Molecules curl up into a ‘ball’ shape

153
Q

What are examples of globular proteins?

A

Haemoglobin, Myoglobin, Insulin

154
Q

What are conjugated proteins?

A

Globular proteins that contain a prosthetic group

155
Q

What is an example of a conjugated protein?

A

Haemoglobin

156
Q

What are fibrous proteins?

A

Structural proteins

157
Q

What are the features of fibrous proteins?

A
  • Long strands

- Usually insoluble

158
Q

What are examples of fibrous proteins?

A
  • Keratin
  • Elasticin
  • Collagen
159
Q

What is the function of Haemoglobin?

A

It is an oxygen-carrying pigment found in red blood cells

160
Q

What is the structure of Haemoglobin?

A
  • Four polypeptides
    - 2 Alpha-globin
    - 2 Beta-globin
  • Each polypeptide has a 3-D structure
  • In the middle, each polypeptide has a Haem group
161
Q

What is the 3-D structure stabilized by in Haemoglobin?

A

Hydrophobic interactions in the centre

162
Q

What type of protein is collagen?

A

Fibrous protein

163
Q

Collagen is a important…?

A

Structural protein

164
Q

How many polypeptide chains are in collagen? (Structure)

A

Three identical polypeptide chains

165
Q

The three polypeptide chains in collagen are would in a …? (Structure)

A

Left-handed triple helix

166
Q

How long is each polypeptide in collagen?

A

About 1000 amino acids long

167
Q

What type of structure does the three polypeptide chains have in collagen?

A

Primary structure

168
Q

Which amino acid is found every three amino acids in collagen?

A

Glycine

169
Q

What happens to the sequence in the polypeptide chains in collagen that allows glycine to be found at every position along the triple helix?

A

The polypeptide chains are staggered

170
Q

What bonds hold the three polypeptide chains together in collagen?

A

Hydrogen

171
Q

Which type of bond holds together adjacent molecules of collagen?

A

Covalent bonds

172
Q

Where are the covalent bonds formed in collagen?

A

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

173
Q

Collagen is a structural protein, what property allows this?

A

It is a tough, rope-like protein

174
Q

What type of structure does collagen have overall?

A

Quaternary

175
Q

What do the staggered ends allow the proteins to do, in collagen?

A

Join end to end

176
Q

What are the fibrils called that collagen produces?

A

Tropocollagen

177
Q

What do the tropocollagen fibrils do that produce strong fibres in collagen?

A

They cross-link

178
Q

What two other amino acids, other than glycine, make up a high proportion of collagen?

A

Proline, hydroxyproline

179
Q

What do the R groups in proline and hydroxyproline do that adds to the stability of collagen?

A

Repel each other

180
Q

Elastin is made by linking?

A

Many soluble tropoelastin protein molecules

181
Q

What do the soluble tropoelastin molecules form?

A

A large, insoluble, and stable, cross-linked structure

182
Q

Tropoelastin molecules are said to act similar to springs, why is this?

A

They are able to stretch and recoil without breaking

183
Q

What do tropoelastin molecules contain?

A

Alternate hydrophobic and lysine-rich areas

184
Q

When is elastin formed?

A

When multiple tropoelastin molecules aggregate via interactions between the hydrophobic areas

185
Q

How is elastin stabilised?

A

By cross-linking covalent bonds, involving the amino acid lysine

186
Q

Elastin gives the … to expand when needed

A

Flexibility

187
Q

What type of protein is elastin?

A

Fibrous protein

188
Q

Where is elastin found?

A

In elastic fibres

189
Q

What structure protein is elastin?

A

Quaternary

190
Q

Keratin has a high proportion of…?

A

The sulfur-containing amino acid, cysteine

191
Q

What does the cysteine amino acid result in, in keratin?

A

Many strong disulphide bonds

192
Q

What do the disulfide bonds form, in keratin?

A

Strong, inflexible, and insoluble materials

193
Q

What does the degree of disulphide bonds determine in Keratin

A

The flexibility of the molecules

194
Q

What is the biuret test actually looking for, instead of the presence of proteins?

A

The presence of peptide bonds

195
Q

What makes up biuret A?

A

Sodium Hydroxide, NaOH

196
Q

What makes up biuret B?

A

Copper Sulphate, CuSO4

197
Q

How do you perform a biuret test for proteins?

A

Mix biuret A with biuret B in the sample.
If there is a protein present, then the sample will turn purple
If no protein present, sample will not change colour

198
Q

How do you do a test for lipids?

A

Emulsion test

  • Add ethanol to the solution
  • Mix solution
  • Add some water
199
Q

Why do you add ethanol to the sample when testing for lipids

A

Lipids are soluble in alcohols

200
Q

Why do you add water to the sample when testing for lipids?

A

All of the dissolved lipids will come out of the solution and are dispersed as small droplets throughout the solution of ethanol and water

201
Q

Explain why water can form hydrogen bonds

A

The positive and negative regions of the water molecule attract each other and form hydrogen bonds because it is polar

202
Q

Hydrogen bonds allow water to act as a solvent

Why is the ability of water to act as a solvent important for the survival of organisms?

A

Many of the solutes in organisms can be dissolved in water. Water acts as a medium for chemical reactions and also helps transport dissolved compounds in and out of cells

203
Q

Agarose forms part of a more complex carbohydrate called agar, which is used as a growth medium for bacteria. Bacteria cannot break down the agarose in agar.
Suggest why bacteria cannot break down agarose.

A

Do not have the necessary enzyme

204
Q

State the name given to the sequence of amino acids in a protein molecule

A

Primary structure

205
Q

State one function of haemoglobin

A

Transports oxygen in the blood

206
Q

What does this description describe:

The type of reaction that occurs when water is added to break a bond in a molecule?

A

Hydrolysis

207
Q

What does this description describe:

The phosphate group of a phospholipid that readily attracts water molecules?

A

Hydrophilic

208
Q

Collagen is found in the ligaments which hold bones together at joints.
State two properties of collagen that make it suitable for this purpose

A

Strong

Insoluble

209
Q

Suggest why a student would be unsure if the positive result for lipid was correct for the milk sample

A

The milk is already white

210
Q

State three roles of lipids in living organisms

A
  • Protection of vital organs
  • Buoyancy
  • Insulator

A level OCR Biology (7 decks)

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