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1) Biological Molecules Flashcards

- Biological molecules - Nucleic acids

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1
Q

what is a monomer?

A

small units which are the components of larger molecules

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2
Q

what is a polymer?

A

molecules made from many monomers joined together

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3
Q

how are monomers joined?

A

by a chemical bond in a condensation reaction, whereby a water molecule is eliminated

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4
Q

what is hydrolysis?

A

when water is added to break a chemical bond between two molecules

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5
Q

carbohydrates only consist of what three elements?

A

carbon, oxygen, and hydrogen

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6
Q

what are carbohydrates long chains of?

A

sugar units, saccharides

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7
Q

what is a single sugar unit called?

A

monosaccharide

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8
Q

what is a disaccharide?

A

two monosaccharides bonded joined together

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9
Q

how is a polysaccharide formed?

A

by combining many monosaccharides

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10
Q

by what bond are saccharides joined together?

A

glycosidic bond

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11
Q

in what kind of reaction are saccharides joined?

A

condensation

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12
Q

what kind of molecule is glucose?

A

a monosaccharide

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13
Q

how many carbon atoms are in each molecule of glucose?

A

six

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14
Q

why is glucose important?

A

it is the main substrate for respiration

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15
Q

what are two isomers of glucose?

A

alpha and beta glucose

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16
Q

what is the mnemonic for the structure of alpha and beta glucose’s structure?

A

ABBA
A - alpha
B - below
B - beta
A - above

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17
Q

give the names of three common monosaccharides

A

glucose
galactose
fructose

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18
Q

how is maltose formed?

A

condensation of two glucose molecules

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19
Q

how is sucrose formed?

A

condensation of glucose and fructose

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20
Q

how is lactose formed?

A

condensation of glucose and galactose

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21
Q

what are three common polysaccharides?

A

glycogen
starch
cellulose

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22
Q

how is glycogen formed?

A

condensation of alpha glucose

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23
Q

how is starch formed?

A

condensation of alpha glucose

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24
Q

how is starch formed?

A

condensation of alpha glucose

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25
Q

what is the main difference between glycogen/starch and cellulose?

A

glycogen/starch is formed from alpha glucose whereas cellulose is from beta glucose

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26
Q

what is the main energy storage molecule in animals?

A

glycogen

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27
Q

what bonds join alpha glucose molecules to form glycogen?

A

1,4 and 1,6 glycosidic bonds

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28
Q

state three properties of glycogen that make it suitable for energy storage

A

large number of side branches
compact
insoluble

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29
Q

how does having a large number of side branches make glycogen suitable for its role?

A

enzymes can act simultaneously on these branches so energy can be released quickly

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30
Q

how does being a compact molecule make glycogen suitable for its role?

A

maximises the amount of energy it can store

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31
Q

how does being insoluble make glycogen suitable for its role?

A

it will not affect the water potential of cells and cannot diffuse out

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32
Q

what is starch’s role?

A

energy storage in plants

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33
Q

what is starch a mixture of?

A

two polysaccharides - amylose and amylopectin

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34
Q

describe the structure of amylose

A

unbranched chain of glucose molecules
coiled
compact

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35
Q

what are amylose and amylopectin?

A

polysaccharides that make up starch

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36
Q

what bonds join glucose molecules in amylose?

A

1,4 glycosidic bonds

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37
Q

what bonds join glucose molecules in amylopectin?

A

1,4 and 1,6 glycosidic bonds

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38
Q

is amylose branched or unbranched

A

unbranched

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39
Q

is amylopectin branched or unbranched?

A

branched

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40
Q

give one property of amylopectin that makes it suitable for its role

A

many side branches

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41
Q

how does having many side branches make amylopectin suitable for its role?

A

these can be acted on simultaneously by enzymes and therefore broken down to release energy

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42
Q

give two properties of starch that make it suitable for its role

A

insoluble
compact

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43
Q

how does starch being insoluble make it suitable for its role?

A

will not affect cell water potential

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44
Q

how does starch being compact make it suitable for its role?

A

a lot of energy can be stored in a small space

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45
Q

what is the role of cellulose?

A

component of plant cell walls

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46
Q

describe the structure of cellulose

A

long, unbranched chains of beta glucose, joined by glycosidic bonds

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47
Q

describe the structure of microfibrils

A

strong threads of long cellulose chains running parallel to one another, joined by hydrogen bonds, forming strong cross linkages

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48
Q

how is cellulose important in cell walls?

A

stops it from bursting under osmotic pressure

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49
Q

how does cellulose prevent cell walls from bursting?

A

it exerts inward pressure that stops the influx of water

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50
Q

what is the biochemical test for the presence of reducing sugars?

A

benedict’s reagent and heat

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51
Q

what kinds of saccharides are reducing sugars?

A

all monosaccharides and some disaccharides

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52
Q

why do reducing sugars give a positive result in the benedict’s test?

A

they can donate an electron to the reagent

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53
Q

describe how to carry out the biochemical test for reducing sugars and state the positive result

A
  1. add 2cm³ of food sample in liquid form
  2. add 2cm³ of benedict’s
  3. heat mixture gently in a water bath
    positive result is solution turns brick-red
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54
Q

which saccharides are non-reducing sugars?

A

some disaccharides and all polysaccharides

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55
Q

what is the biochemical test for non-reducing sugars?

A

benedict’s reagent with hydrochloric acid and sodium hydrogen carbonate and heat

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56
Q

describe how to carry out a biochemical test for non-reducing sugars and give the positive result

A
  1. 2cm³ of sample in liquid form added to 2cm³ of benedict’s reagent, and warmed gently
  2. if colour does not change to brick-red then reducing sugar is not present
  3. another 2cm³ of sample is taken and 2cm³ of HCl is added, then warm in water bath
  4. add NaHCO₃
  5. retest with benedict’s and heat
    if non-reducing sugar is present then brick-red colour
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57
Q

why is hydrochloric acid added when testing for non-reducing sugars?

A

to hydrolyse the disaccharides and polysaccharides into their monosaccharides

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58
Q

why is sodium hydrogen carbonate added when testing for non-reducing sugars?

A

to neutralise the solution as benedict’s will not work in acidic conditions (created by the HCl)

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59
Q

what is the biochemical test for starch? give the positive result

A

potassium iodide
blue/black

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60
Q

what elements are lipids made from?

A

carbon, hydrogen, and oxygen

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61
Q

what solvents are lipids soluble in? give an example

A

organic solvents
alcohols

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62
Q

what are the two main lipid types?

A

triglycerides
phospholipids

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63
Q

what are the components of triglycerides?

A

one molecules of glycerol and three fatty acids

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64
Q

by what kind of reactions are the components of triglycerides joined?

A

condensation reactions

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65
Q

by what bonds are the components of triglycerides joined?

A

ester bonds

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66
Q

what is the difference between saturated and unsaturated lipids?

A

saturated don’t contain any C=C, whereas unsaturated do

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67
Q

what does the presence of a C=C prevent a molecule being able to do?

A

bend

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68
Q

why are unsaturated lipids liquid at room temperature?

A

the C=C prevents them packing together tightly so they take less heat energy to melt, therefore liquid at room temperature

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69
Q

give four properties of triglycerides that makes them suitable for their role

A

high ratio of C-H to C
low mass to energy ratio
large and non-polar
high ratio of H-O atoms

70
Q

how does triglycerides having a high ratio of C-H bonds to C atoms make them suitable for their role?

A

makes them an excellent energy store

71
Q

how does triglycerides having a low mass to energy ratio make them suitable for their role?

A

makes them a good storage molecule as a lot of energy can be stored in a small volume
beneficial for animals as less mass to move

72
Q

how does triglycerides being large and non-polar make them suitable for their role?

A

their storage does not affect cell’s water potential

73
Q

how does triglycerides having a high ratio of H to O atoms make them suitable for their role?

A

means they release water when oxidised therefore providing a source of water for organisms to live in dry environments

74
Q

what is the key structural difference between a phospholipid and triglyceride?

A

in phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group

75
Q

are phosphate heads hydrophilic or hydrophobic?

A

hydrophilic

76
Q

are phosphate tails hydrophilic or hydrophobic?

A

hydrophobic

77
Q

how are phospholipids polar?

A

because heads are hydrophilic and hydrophobic

78
Q

what does phospholipids form when in contact with water?

A

micelles

79
Q

in an aqueous environment what do phospholipids form and why?

A

a bilayer because they are polar

80
Q

what does phospholipid’s structure allow them to form with carbohydrates?

A

glycolipids

81
Q

what is the biochemical test for lipids?

A

emulsion test

82
Q

describe how an emulsion test would be carried out and give the positive result

A
  1. add 2cm³ of the sample and 5cm³ of ethanol to a clean test tube
  2. shake to dissolve the lipid in the solution
  3. add 5cm³ of water and shake
    positive result is white/milky
83
Q

what are the monomers from which proteins are made?

A

amino acids

84
Q

what are the components of an amino acid?

A

amino group, carboxylic acid group, and variable R group

85
Q

how many different amino acids are there?

A

20

86
Q

what determines different amino acids?

A

different R groups

87
Q

what bonds join amino acids?

A

peptide bonds

88
Q

what kind of reaction joins amino acids?

A

condensation

89
Q

when amino acids are joined, what is also formed?

A

a molecule of water

90
Q

describe the primary structure of a protein

A

the order and number of amino acids in a protein

91
Q

what determines the protein’s final function?

A

its primary structure - sequence of amino acids

92
Q

describe the secondary structure of a protein

A

the shape that the chain of amino acids makes - either alpha helix or beta pleated sheet

93
Q

why can weak hydrogen bonds form between amino acids?

A

because the hydrogen in the -NH has a slight positive charge and the oxygen in the -C=O has a slight negative charge

94
Q

describe the tertiary structure of proteins

A

the 3D shape of a protein
is formed from further folding

95
Q

what are the bonds that maintain the tertiary structure

A

disulphide bridges
ionic bonds
hydrogen bonds

96
Q

where do disulphide bridges form in protein tertiary structures?

A

interactions between the sulphur of the R group of the amino acid cysteine

97
Q

how strong are disulphide bridges that form protein’s tertiary structure compared to the others?

A

strong and not easily broken

98
Q

where do ionic bonds form in a protein’s tertiary structure?

A

between the carboxyl and amino groups not involved in the peptide bonds

99
Q

how strong are the ionic bonds formed in a protein’s tertiary structure compared to other bonds?

A

weaker than disulphide bridges

100
Q

what are ionic bonds in a protein’s tertiary structure broken by?

A

pH

101
Q

describe the hydrogen bonds in a protein’s tertiary structure

A

numerous and easily broken

102
Q

what two kinds of proteins are there?

A

globular and fibrous

103
Q

what is the difference between globular and fibrous proteins?

A

globular are compact, whereas fibrous are long and therefore can be used to form fibres

104
Q

what is the biochemical test for proteins

A

the biuret test

105
Q

describe the steps to carry out the biuret test and give the positive result

A
  1. place the sample in a test tube and add an equal volume of sodium hydroxide at room temperature
  2. add a few drops of dilute copper sulphate solution and mix gently
  3. positive result is purple
106
Q

what do enzymes do?

A

increase the rate of reaction

107
Q

how do enzymes increase the rate of reaction?

A

by lowering the activation energy by providing an alternative reaction pathway

108
Q

describe the general structure of an enzyme

A

3D tertiary structured globular proteins

109
Q

what determines an enzymes shape?

A

the primary sequence of amino acids

110
Q

what is an enzyme’s active site?

A

area of an enzyme that forms a small depression in the enzyme

111
Q

what is the substrate?

A

the molecule that the enzyme acts upon

112
Q

explain the induced fit model of enzyme action

A

enzymes are specific to substrates
when enzyme and substrate bind, they form an E-S complex
and the enzyme’s structure is altered so the active site fits around the substrate

113
Q

give five factors that affect the rate of enzyme-controlled reactions

A

temperature
pH
enzyme concentration
substrate concentration
inhibitor concentration

114
Q

how does increasing temperature affect the rate of enzyme-controlled reaction?

A

RoR increases up to the optimum temperature as enzyme’s kinetic energy increases
Above optimum, RoR decreases as enzyme becomes denatured

115
Q

how does changing pH affect the rate of enzyme-controlled reaction?

A

Enzymes have an optimum pH
Above and below the optimum the shape gets altered and so it becomes denatured

116
Q

how does increasing enzyme concentration affect the rate of enzyme-controlled reaction?

A

RoR increases as there are more active sites for substrates to bind to
Only to a point however as eventually there will be more active sites than substrates so substrate concentration becomes the limiting factor

117
Q

how does increasing substrate concentration affect the rate of enzyme-controlled reaction?

A

RoR increases as more E-S complexes are formed
However only to a point as eventually enzyme concentration becomes the limiting factor

118
Q

how does increasing concentration of competitive inhibitor affect the rate of enzyme-controlled reaction?

A

RoR decreases as the active sites become blocked preventing substrates binding to them

119
Q

how does increasing concentration of non-competitive inhibitors affect the rate of enzyme-controlled reaction?

A

RoR decreases as the shape of the enzyme is altered by the inhibitors, preventing E-S complexes forming

120
Q

what does DNA do?

A

holds genetic information

121
Q

what does RNA do?

A

transfers genetic information from DNA to ribosomes for protein synthesis

122
Q

what are the components of any nucleotide?

A

pentose sugar
organic base
phosphate group

123
Q

what are the components of a DNA nucleotide?

A

deoxyribose sugar
phosphate group
organic base

124
Q

name the four organic bases that a DNA nucleotide could have

A

adenine
cytosine
guanine
thymine

125
Q

what are the components of an RNA nucleotide?

A

ribose sugar
phosphate group
organic base

126
Q

name the four bases that an RNA nucleotide could have

A

adenine
cytosine
guanine
uracil

127
Q

what bonds join nucleotides? between what?

A

phosphodiester bonds
the deoxyribose sugar and one nucleotide and the phosphate group of another

128
Q

describe the structure of a DNA molecule

A

double helix composed of two polynucleotides joined by hydrogen bonds between complementary bases

129
Q

what bonds join complementary base pairs in a DNA molecule?

A

hydrogen bonds

130
Q

what are the four key differences between the structure of DNA and RNA

A
  1. sugar in RNA is ribose, whereas it is deoxyribose in DNA
  2. RNA is single-stranded, whereas DNA is double-stranded
  3. RNA contains uracil in place of thymine
  4. RNA is a shorter polynucleotide chain than DNA
131
Q

state the complementary base pairing of adenine, thymine, guanine, and cytosine

A

A - T
G - C

132
Q

what are ribosomes formed from?

A

RNA and proteins

133
Q

give the name of the process by which DNA replication occurs

A

semi-conservative replication

134
Q

what is the advantage of semi-conservative replication?

A

ensures genetic continuity between generations

135
Q

describe the process of semi-conservative replication of DNA

A
  1. DNA helicase causes the two stands to separate, breaking the hydrogen bonds between complementary bases
  2. one strand is used a template and complementary base pairing occurs between the template strand and free nucleotides
  3. once nucleotides are bound, DNA polymerase joins them by catalysing the formation of phosphodiester bonds
136
Q

name the two enzymes involved in DNA replication

A

DNA helicase
DNA polymerase

137
Q

what is the role of DNA helicase in DNA replication?

A

separates the two DNA strands by breaking the hydrogen bonds between bases

138
Q

what is the role of DNA polymerase in DNA replication?

A

catalyses the formation of phosphodiester bonds

139
Q

what are the components of ATP?

A

ribose
adenine
three phosphate groups

140
Q

how is energy released from ATP?

A

when ATP is hydrolysed

141
Q

what are the products of ATP hydrolysis?

A

ADP and a phosphate molecule

142
Q

what enzyme catalyses ATP hydrolysis?

A

ATP hydrolase

143
Q

where does the energy released in ATP hydrolysis come from?

A

the bonds between the phosphate molecules

144
Q

why are the bonds between phosphate molecules in ATP easily broken?

A

because they are unstable and have a low activation energy

145
Q

how can the inorganic phosphate from ATP be used?

A

to phosphorylate other compounds, making them more reactive

146
Q

how is ATP produced? give the enzyme

A

condensation of ADP and inorganic phosphate
catalysed by ATP synthase
during photosynthesis and respiration

147
Q

why is ATP more desirable to use than glucose?

A

because it can be broken down in a single step to release a more manageable amount of energy

148
Q

why is ATP not stored in large quantities?

A

as it can easily be reformed from ADP in seconds

149
Q

give five uses of ATP

A

metabolic processes
movement
active transport
secretion
activation of molecules

150
Q

why is water a polar molecule?

A

due to uneven distribution of charge within the molecule - the H atoms are more positive than the O atom causing one end of the molecule to be more positive

151
Q

give six key properties of water

A

polar
metabolite
solvent
high specific heat capacity
high latent heat of vaporisation
cohesive

152
Q

how is water a metabolite? give two examples

A

in metabolic reactions such as condensation and hydrolysis

153
Q

why is water useful as a solvent?

A

most metabolic processes take place in solution

154
Q

explain how water’s high specific heat capacity is useful for living organisms

A

means water doesn’t experience rapid temperature changes so it makes a stable habitat and helps organisms to maintain a constant internal body temperature

155
Q

why does water have a high specific heat capacity and high latent heat of vaporisation?

A

because it has strong hydrogen bonding

156
Q

what is latent heat of vaporisation (of water)?

A

the energy required to evaporate 1 gram (of water)

157
Q

explain how water’s large latent heat of vaporisation is useful for living organisms

A

it means evaporation of water provides a cooling effect with little water loss
e.g. by sweating

158
Q

what does water’s strong cohesion allow?

A

transport of water in tubes e.g. in the xylem

159
Q

what is an effect of water’s strong cohesion?

A

the surface tension at the water-air boundary is high

160
Q

where do inorganic ions occur?

A

in solution in the cytoplasm and body fluid of organisms

161
Q

give four essential inorganic ions

A

hydrogen ions
iron ions
sodium ions
phosphate ions

162
Q

what is the role of hydrogen ions in the body?

A

determine the pH of substances such as blood

163
Q

what is the role of iron ions in the body?

A

a component of haemoglobin

164
Q

what is the role of sodium ions in the body?

A

involved in co-transport of glucose and amino acids

165
Q

what is the role of phosphate ions in the body?

A

a component of DNA and ATP

166
Q

what is the R group of a fatty acid?

A

everything except the COOH

167
Q

Describe two differences between thestructure of a triglyceride and a phospholipid

A
  1. Triglyceride has 3 fatty acids whereas phospholipid has 2
  2. Phospholipid contains a phosphate whereas triglyceride does not
168
Q

Explain why phospholipids can form a bilayer but triglycerides cannot

A

-phospholipids are polar molecules whereas triglycerides are only hydrophobic
- This causes them to arrange themselves in a bilayer as the heads are attracted to water on the outside of the bilayer and tails are repelled by it

169
Q

The human papilloma virus contains a double-stranded DNA genome.
Which components are found in a human papilloma virus?
- capsid and attachment protein
- capsid, attachment protein, and reverse transcriptase
- capsule and attachment protein
- cell-surface membrane and attachment protein

A

Capsid and attachment protein (option 2)

170
Q

Name 2 enzymes that are involved in DNA replication and describe their roles in the process

A
  1. DNA helicase - breaks hydrogen bonds between bases to separate the two strands
  2. DNA polymerase - synthesis of phosphodiester bonds between bases

Biology (8 decks)

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