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A-Level OCR Biology > Chapter 3 - Biological Molecules > Flashcards

Chapter 3 - Biological Molecules Flashcards

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1
Q

How are the electrons shared in O-H water bonds?

A

Not equally- oxygen has a much greater share

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2
Q

What primarily gives water its unique characteristics?

A

Hydrogen

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3
Q

Why is water such an important component in transport?

A

It acts as a solvent, which is essential for the movement of important solutes

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4
Q

Why is water a solvent?

A

Because it is a polar molecule, meaning molecules are attracted to the water (H2O molecules), allowing them to move as one mass

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5
Q

What is capillary action?

A

The process in which water can rise up a narrow tube against the force of gravity

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6
Q

What happens to the density of water when it freezes?

A

It becomes less dense

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7
Q

Why does the density of water decrease when it freezes?

A

Because it forms a crystalline structure, due to hydrogen bonds which fix the molecules slightly further apart than the average distance in liquid state

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8
Q

Are hydrogen bonds strong?

A

Individually, hydrogen bonds interactions are weak, however they occur in high numbers

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9
Q

What are hydrogen bonds in water?

A

The interactions between different water molecules. The delta positive hydrogens interact with the delta negative oxygens, and this electrostatic attraction forms hydrogen bonds

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10
Q

What causes water to have a ‘skin’ of surface tension?

A

Because water molecules are more strongly cohesive to each other than to air

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11
Q

What causes water to have cohesive properties?

A

Hydrogen bonds between water molecules

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12
Q

What are carbohydrates also known as?

A

Saccharides or sugars

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13
Q

If something ends is -ose, what are they?

A

Carbohydrates

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14
Q

What is a single sugar unit known as?

A

A monosaccharide

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15
Q

When monosaccharides are joined together, what do they form?

A

Polysaccharides

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16
Q

What is the chemical formula of glucose?

A

C6.H12.O6

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17
Q

How many carbons is glucose composed of and what does this make it?

A

6 carbons, making it a hexose monosaccharide

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18
Q

What are the two structural variations of glucose?

A

Alpha glucose and beta glucose

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19
Q

How are the carbons numbered in glucose?

A

Clockwise, beginning with the carbon to the right of the oxygen within the ring

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20
Q

What is the different between alpha and beta glucose?

A

The OH group on carbon 1 is in opposite positions

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21
Q

Why aren’t glucose molecules polar?

A

They are

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22
Q

Is glucose soluble in water- why?

A

Yes it is, because of hydrogen bonds that form between the hydroxyl groups (OH) and H2O molecules

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23
Q

What is a glycosidic bond?

A

The covalent bond formed in saccharides, which join carbohydrates

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24
Q

Why are reactions called condensation reactions?

A

Because they form water as one of the products

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25
Q

What type of reaction is the reaction between two glucose molecules?

A

A condensation reaction

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26
Q

What two molecules form sucrose?

A

Glucose and fructose

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27
Q

In a glycosidic bond, how do you get the prefix numbers (e.g 1,4 glycosidic bond)?

A

You find the two carbons the bond is between (e.g the first and fourth carbon)

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28
Q

Where is ribose present?

A

In RNA nucleotides

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29
Q

Where is deoxyribose found?

A

DNA nucleotides

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30
Q

What type of glucose molecule forms starch?

A

Alpha glucose

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31
Q

What are the two types of polysaccharides in starch?

A

Amylose and amylopectin

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32
Q

What is the structure of amylose?

A

Helix, which is further stranded by hydrogen bonding within the molecule

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33
Q

What are the effects of the structure of amylose on its properties?

A

It makes it more compact and much less soluble

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34
Q

When is amylose formed?

A

When alpha glucose molecules are joined only by 1,4 glycosidic bonds

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35
Q

What type of energy store is starch?

A

A chemical energy store

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36
Q

What is the structure of amylopectin?

A

It is also made by alpha glucose 1,4 glycosidic bonds, however (unlike amylose) there are also some 1,6 bonds, giving it a branched structure

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37
Q

How often do you see branching points in amylopectin?

A

Once every approximately 25 glucose molecules

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38
Q

Why is ice floating useful for living environments?

A
  • Insulates environment below; water below does not freeze and is kept at higher temperature
  • Habitat for certain animals e.g. polar bears
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39
Q

Why is water being a solvent useful for living environments?

A
  • Solvent for important ions that organisms uptake

- e.g. nitrates for amino acids

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40
Q

Why does ice float?

A

Because when water freezes the molecules spread out and form a fixed lattice

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41
Q

How does ice insulating the water below help the survival of organisms?

A
  • Organisms can still move
  • Organisms do not freeze
  • Allows nutrients to continue to circulate
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42
Q

Why is water an excellent solvent?

A

As it is polar, so attracts and binds to other polar/charged molecules e.g. ions

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43
Q

Why is water’s stable temperature useful for living environments?

A
  • Large number of hydrogen bonds mean high specific heat capacity
  • Temperature of enzymes remains constant, preventing them from working too slowly or denaturing
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44
Q

What bonds form between amino acids?

A

Peptide bonds

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45
Q

What type of reaction is the reaction between amino acids?

A

Condensation

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46
Q

What is the opposite of condensation reactions?

A

Hydrolysis

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47
Q

What are amine groups made up of?

A

H-N-H

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48
Q

What are carboxyl groups made up of?

A

O=C-O-H

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49
Q

What forms when many amino acids are joined together?

A

A polypeptide

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50
Q

What part of an amino acid distinguishes it from other amino acids?

A

Its R-group

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51
Q

What do different sequences of amino acids lead to?

A

Different protein structures with different shapes being produced

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52
Q

What is primary protein structure?

A

The base initial sequence in which amino acids are joined

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53
Q

What bonds are involved in the primary structure of proteins?

A

Only peptide bonds

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54
Q

What are R-groups in amino acids?

A

The part that can vary

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55
Q

What are two types of secondary structure?

A

Alpha helices

Beta pleated sheets

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56
Q

What is secondary protein structure?

A

When the amino acid chain structure change as a result of hydrogen bonding

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57
Q

Properties of globular proteins

A
  • compact
  • water soluble
  • roughly spherical
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58
Q

When do globular proteins form?

A

When proteins fold into their tertiary structures in such a way that the hydrophobic R-groups on the amino acids are kept away from the aqueous environment, making them soluble

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59
Q

Give one example of a globular protein

A

Insulin

60
Q

Insulin properties

A
  • globular protein

- hormone involved in maintaining blood glucose levels

61
Q

What does insulin need to be fulfill its purpose?

A
  • soluble in blood to allow transportation

- precise shape to fit into specific receptors to have their effect

62
Q

What are conjugated proteins?

A

Globular proteins that contain a non protein component called a prosthetic group

63
Q

What make up triglycerides?

A

One glycerol molecule and three fatty acids

64
Q

How do fatty acids and glycerol molecules react to form lipids?

A

The hydrogens from the glycerol molecule react with the hydroxyls from the fatty acids, forming water.
The glycerol oxygens then react with the carbonyl groups of the fatty acids, forming an ester bond

65
Q

What is bond in triglycerides called?

A

Ester bond

66
Q

What are saturated fatty acid chains and what are their structure?

A

Chains with no double bonds between carbons; form straight chains

67
Q

What are monounsaturated fatty acid chains?

A

Chains with one double bond between carbons

68
Q

What are polyunsaturated fatty acid chains and what are their structure?

A

Chains with more than one double bond between carbons, meaning they can’t pack together closely

69
Q

In fatty acid chains, what do double bonds do?

A

Cause the molecule to bend

70
Q

What state are polyunsaturated fatty acid chains at room temperature?

A

Liquid (i.e they are oils)

71
Q

What are phospholipids made up of?

A

One hydrophilic phosphate head attached to two hydrophobic fatty acid tails

72
Q

Why are phospholipids called surfactants?

A

Because they form a layer on the surface of water, with the hydrophobic fatty acid tails sticking out of the water

73
Q

What are sterols also known as?

A

Steroid alcohols

74
Q

What are sterols?

A
  • Another type of lipid
  • They are alcohols
  • The OH group is hydrophilic, but the rest is hydrophobic
75
Q

Example of sterol

A

Cholesterol

76
Q

What is the general structure of an amino acid?

A

Carbon, which is attached to an amine group, a carboxyl group, an R-group and a hydrogen

77
Q

What are proteases?

A

Enzymes that catalyse the hydrolysis reaction of peptides

78
Q

What makes up a peptide bond?

A

C - N

79
Q

What is catalase?

A

An enzyme that breaks down hydrogen peroxide

80
Q

What are fibrous proteins?

A

Long insoluble proteins

81
Q

2 difference between globular and fibrous proteins

A
  • Globular are soluble, fibrous aren’t

- Fibrous aren’t folded into complex 3-D shapes, globular are

82
Q

3 examples of fibrous proteins

A
  • Keratin
  • Elastin
  • Collagen
83
Q

Where is keratin found?

A

In hair, skin and nails

84
Q

Where is elastin found?

A

In walls of blood vessels and aveoli

85
Q

Where is collagen found?

A

Connective tissue found in skin, tendons, ligaments and the nervous system

86
Q

What are the three components of a nucleotide?

A
  • Phosphate group
  • Pentose sugar
  • Nitrogenous base
87
Q

What are the bonds between nucleotides?

A

Phosphodiester bonds

88
Q

What are the 4 types of base?

A
  • Adenine
  • Thymine
  • Guanine
  • Cytosine
89
Q

What can the 4 types of base be divided into?

A

2 groups- pyrimidines and purines

90
Q

What bases are pyrimidines?

A

Thymine and Cytosine

91
Q

What bases are purines?

A

Guanine and Adenine

92
Q

Which are bigger, purines or pyrimidines and why?

A

Purines, due to their double ring structure

93
Q

How many hydrogen bonds do A and T form?

A

2

94
Q

How many hydrogen bonds do G and C form?

A

3

95
Q

What is thymine replaced by in RNA?

A

Uracil

96
Q

What is the sugar in DNA?

A

Deoxyribose

97
Q

What is the sugar in RNA?

A

Ribose

98
Q

What is the function of DNA helicase in semi-conservative replication?

A

Enzyme that cause the two strands of DNA to separate

99
Q

What is the function of DNA polymerase in semi-conservative replication?

A

Enzyme that cause the nucleotides to join up (form phosphodiester bonds)

100
Q

What is semi-conservative replication?

A

Where two new molecules of DNA are produced, each one consisting of one strand of the old DNA, and one strand of the new DNA

101
Q

What is a codon?

A

A triplet code

102
Q

What is transcription?

A

Process where DNA is turned into RNA

103
Q

What is translation?

A

Process where mRNA is translated into a sequence of amino acids

104
Q

What is the sense strand?

A

The strand of DNA that contains the desired sequence of bases to code for the amino acids

105
Q

What is the antisense strand?

A

The complimentary strand to the sense strand- it acts as a template strand, so the complementary RNA strand carries the same base sequence as the sense strand

106
Q

What is the function of DNA polymerase?

A

Enzyme that catalyses the formation of phosphodiester bonds

107
Q

What does tRNA contain which is necessary for protein synthesis?

A

Anticodons

108
Q

What do anticodons do?

A

Bind to their complimentary codon, which brings amino acids together in the correct sequence

109
Q

Properties of ATP

A
  • Soluble
  • Small
  • Contains bonds that release amount of energy suitable for most cellular needs, but not so much energy is wasted as heat
110
Q

How is energy released by ATP?

A

Bond reforming from ADP + P to ATP

111
Q

What type of energy store is ATP and why?

A

It is a good immediate energy store, as the interconversion of ATP to ADP is happening constantly, meaning they don’t need a large store of it

112
Q

Why is ATP not a long term energy store?

A

Due to the instability of the phophate bonds

113
Q

What is the structure of ADP?

A

3 phosphates - ribose - adenine

114
Q

Why is haemoglobin a conjugated protein?

A

Because it contains the haem prosthetic group

115
Q

What is glycogen functionally equivalent to?

A

Starch

116
Q

What types of organisms is glycogen found in?

A

Animals and fungi

117
Q

What are the key properties of amylopectin (found in plants) and glycogen (found in animals)?

A

Insoluble
Branched
Compact

118
Q

What is glucose stored as in plants?

A

Starch

119
Q

What is glucose stored as in animals?

A

Glycogen

120
Q

What type of reactions must starch/glycogen undergo to release glucose for respiration?

A

Hydrolysis reactions

121
Q

Why are beta glucose molecules unable to join together in the same way alpha glucose molecules do?

A

Because the hydroxyl groups on carbon 1 and 4 are too far away from each other to react and form a bond

122
Q

What is the only way beta glucose molecules can be joined together?

A

Alternate beta glucose molecules are turned upside down, to bring the hydroxyl groups close enough together

123
Q

What is the outcome of this bonding of beta glucose molecules?

A

The polysaccharide formed is unable to coil or form branches, so is a straight chain molecule

124
Q

What is the name of the straight chain molecule formed from the join of beta glucose molecules?

A

Cellulose

125
Q

What is the test for reducing sugars?

A

Warm with Benedict’s reagent

126
Q

What are the different positive results for the test for reducing sugars and what does each tell you?

A

Blue - no reducing sugars
Green - low concentration
Orange - medium concentration
Red - high concentration

127
Q

What will happen when non-reducing sugars and Benedict’s are mixed?

A

They will not react (the solution will remain blue)

128
Q

How do you test for non-reducing sugars?

A

You must boil it with dilute hydrochloric acid, and then warm with Benedict’s reagent

129
Q

In the test for non-reducing sugars, why must it first be boiled with dilute HCl?

A

Because the non-reducing sugar will be hydrolysed by the acid, turning into its reducing sugar components, hence giving a positive test

130
Q

What is the test for starch and positive result?

A

Add iodine solution, and the positive test is a colour change from yellow to purple/black

131
Q

How do you test for lipids and what is the positive result?

A

Emulsion test- sample mixed with ethanol and then shaken with water. If a white emulsion forms, lipids are present

132
Q

How are peptide bonds formed?

A

A hydrogen from amino acid 1, and the OH from amino acid 2 join together to form water.
The nitrogen from amino acid 1 forms the peptide bond with the carbon from amino acid 2

133
Q

What is tertiary protein structure?

A

The protein folding into its final shape

134
Q

What 5 interactions are found in tertiary proteins?

A
  • Dipole-dipole interactions
  • London forces
  • Hydrogen bonds
  • Ionic bonds
  • Disulphide bridges
135
Q

Where do ionic bonds form between in tertiary proteins?

A

Between oppositely charged R-groups

136
Q

What are disulphide bridges?

A

Covalent bonds that form between R-groups that both contain sulphur

137
Q

What are quaternary proteins?

A

Where interactions form between two or more individual proteins (called subunits). These can be identical or different proteins

138
Q

What interactions are present in quaternary proteins?

A

All the same interactions as in tertiary proteins, however they are between different protein molecules rather than within one molecule

139
Q

Why is genetic code referred to as degenerate code?

A

Because different codons can code for the same amino acid

140
Q

What enzyme causes phosphodiester bonds to be formed between RNA nucleotides?

A

RNA polymerase

141
Q

What must happen to the DNA double helix for transcription to occur?

A

The DNA double helix must be unzipped (by DNA helicase)

142
Q

Where does the mRNA first bind to during translation?

A

The start codon (AUG) binds to the small subunit of the ribosome

143
Q

What does tRNA carry that is necessary in translation?

A

Each tRNA molecule carries an amino acid corresponding to the correct triplet code

144
Q

What does the first tRNA molecule always carry?

A

The amino acid methionine

145
Q

What happens between amino acids during translation?

A

They form peptide bonds between each other, which in turn causes the 1st tRNA to release the 1st amino acid

146
Q

What does the ribosomes do during translation?

A

It moves along the mRNA

A-Level OCR Biology (21 decks)

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