1) Biological Molecules Flashcards
- Biological molecules - Nucleic acids
1
Q
what is a monomer?
A
small units which are the components of larger molecules
2
Q
what is a polymer?
A
molecules made from many monomers joined together
3
Q
how are monomers joined?
A
by a chemical bond in a condensation reaction, whereby a water molecule is eliminated
4
Q
what is hydrolysis?
A
when water is added to break a chemical bond between two molecules
5
Q
carbohydrates only consist of what three elements?
A
carbon, oxygen, and hydrogen
6
Q
what are carbohydrates long chains of?
A
sugar units, saccharides
7
Q
what is a single sugar unit called?
A
monosaccharide
8
Q
what is a disaccharide?
A
two monosaccharides bonded joined together
9
Q
how is a polysaccharide formed?
A
by combining many monosaccharides
10
Q
by what bond are saccharides joined together?
A
glycosidic bond
11
Q
in what kind of reaction are saccharides joined?
A
condensation
12
Q
what kind of molecule is glucose?
A
a monosaccharide
13
Q
how many carbon atoms are in each molecule of glucose?
A
six
14
Q
why is glucose important?
A
it is the main substrate for respiration
15
Q
what are two isomers of glucose?
A
alpha and beta glucose
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
17
Q
give the names of three common monosaccharides
A
glucose
galactose
fructose
18
Q
how is maltose formed?
A
condensation of two glucose molecules
19
Q
how is sucrose formed?
A
condensation of glucose and fructose
20
Q
how is lactose formed?
A
condensation of glucose and galactose
21
Q
what are three common polysaccharides?
A
glycogen
starch
cellulose
22
Q
how is glycogen formed?
A
condensation of alpha glucose
23
Q
how is starch formed?
A
condensation of alpha glucose
24
Q
how is starch formed?
A
condensation of alpha glucose
25
what is the main difference between glycogen/starch and cellulose?
glycogen/starch is formed from alpha glucose whereas cellulose is from beta glucose
26
what is the main energy storage molecule in animals?
glycogen
27
what bonds join alpha glucose molecules to form glycogen?
1,4 and 1,6 glycosidic bonds
28
state three properties of glycogen that make it suitable for energy storage
large number of side branches
compact
insoluble
29
how does having a large number of side branches make glycogen suitable for its role?
enzymes can act simultaneously on these branches so energy can be released quickly
30
how does being a compact molecule make glycogen suitable for its role?
maximises the amount of energy it can store
31
how does being insoluble make glycogen suitable for its role?
it will not affect the water potential of cells and cannot diffuse out
32
what is starch's role?
energy storage in plants
33
what is starch a mixture of?
two polysaccharides - amylose and amylopectin
34
describe the structure of amylose
unbranched chain of glucose molecules
coiled
compact
35
what are amylose and amylopectin?
polysaccharides that make up starch
36
what bonds join glucose molecules in amylose?
1,4 glycosidic bonds
37
what bonds join glucose molecules in amylopectin?
1,4 and 1,6 glycosidic bonds
38
is amylose branched or unbranched
unbranched
39
is amylopectin branched or unbranched?
branched
40
give one property of amylopectin that makes it suitable for its role
many side branches
41
how does having many side branches make amylopectin suitable for its role?
these can be acted on simultaneously by enzymes and therefore broken down to release energy
42
give two properties of starch that make it suitable for its role
insoluble
compact
43
how does starch being insoluble make it suitable for its role?
will not affect cell water potential
44
how does starch being compact make it suitable for its role?
a lot of energy can be stored in a small space
45
what is the role of cellulose?
component of plant cell walls
46
describe the structure of cellulose
long, unbranched chains of beta glucose, joined by glycosidic bonds
47
describe the structure of microfibrils
strong threads of long cellulose chains running parallel to one another, joined by hydrogen bonds, forming strong cross linkages
48
how is cellulose important in cell walls?
stops it from bursting under osmotic pressure
49
how does cellulose prevent cell walls from bursting?
it exerts inward pressure that stops the influx of water
50
what is the biochemical test for the presence of reducing sugars?
benedict's reagent and heat
51
what kinds of saccharides are reducing sugars?
all monosaccharides and some disaccharides
52
why do reducing sugars give a positive result in the benedict's test?
they can donate an electron to the reagent
53
describe how to carry out the biochemical test for reducing sugars and state the positive result
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
54
which saccharides are non-reducing sugars?
some disaccharides and all polysaccharides
55
what is the biochemical test for non-reducing sugars?
benedict's reagent with hydrochloric acid and sodium hydrogen carbonate and heat
56
describe how to carry out a biochemical test for non-reducing sugars and give the positive result
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
57
why is hydrochloric acid added when testing for non-reducing sugars?
to hydrolyse the disaccharides and polysaccharides into their monosaccharides
58
why is sodium hydrogen carbonate added when testing for non-reducing sugars?
to neutralise the solution as benedict's will not work in acidic conditions (created by the HCl)
59
what is the biochemical test for starch? give the positive result
potassium iodide
blue/black
60
what elements are lipids made from?
carbon, hydrogen, and oxygen
61
what solvents are lipids soluble in? give an example
organic solvents
alcohols
62
what are the two main lipid types?
triglycerides
phospholipids
63
what are the components of triglycerides?
one molecules of glycerol and three fatty acids
64
by what kind of reactions are the components of triglycerides joined?
condensation reactions
65
by what bonds are the components of triglycerides joined?
ester bonds
66
what is the difference between saturated and unsaturated lipids?
saturated don't contain any C=C, whereas unsaturated do
67
what does the presence of a C=C prevent a molecule being able to do?
bend
68
why are unsaturated lipids liquid at room temperature?
the C=C prevents them packing together tightly so they take less heat energy to melt, therefore liquid at room temperature
69
give four properties of triglycerides that makes them suitable for their role
high ratio of C-H to C
low mass to energy ratio
large and non-polar
high ratio of H-O atoms
70
how does triglycerides having a high ratio of C-H bonds to C atoms make them suitable for their role?
makes them an excellent energy store
71
how does triglycerides having a low mass to energy ratio make them suitable for their role?
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
how does triglycerides being large and non-polar make them suitable for their role?
their storage does not affect cell's water potential
73
how does triglycerides having a high ratio of H to O atoms make them suitable for their role?
means they release water when oxidised therefore providing a source of water for organisms to live in dry environments
74
what is the key structural difference between a phospholipid and triglyceride?
in phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group
75
are phosphate heads hydrophilic or hydrophobic?
hydrophilic
76
are phosphate tails hydrophilic or hydrophobic?
hydrophobic
77
how are phospholipids polar?
because heads are hydrophilic and hydrophobic
78
what does phospholipids form when in contact with water?
micelles
79
in an aqueous environment what do phospholipids form and why?
a bilayer because they are polar
80
what does phospholipid's structure allow them to form with carbohydrates?
glycolipids
81
what is the biochemical test for lipids?
emulsion test
82
describe how an emulsion test would be carried out and give the positive result
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
what are the monomers from which proteins are made?
amino acids
84
what are the components of an amino acid?
amino group, carboxylic acid group, and variable R group
85
how many different amino acids are there?
20
86
what determines different amino acids?
different R groups
87
what bonds join amino acids?
peptide bonds
88
what kind of reaction joins amino acids?
condensation
89
when amino acids are joined, what is also formed?
a molecule of water
90
describe the primary structure of a protein
the order and number of amino acids in a protein
91
what determines the protein's final function?
its primary structure - sequence of amino acids
92
describe the secondary structure of a protein
the shape that the chain of amino acids makes - either alpha helix or beta pleated sheet
93
why can weak hydrogen bonds form between amino acids?
because the hydrogen in the -NH has a slight positive charge and the oxygen in the -C=O has a slight negative charge
94
describe the tertiary structure of proteins
the 3D shape of a protein
is formed from further folding
95
what are the bonds that maintain the tertiary structure
disulphide bridges
ionic bonds
hydrogen bonds
96
where do disulphide bridges form in protein tertiary structures?
interactions between the sulphur of the R group of the amino acid cysteine
97
how strong are disulphide bridges that form protein's tertiary structure compared to the others?
strong and not easily broken
98
where do ionic bonds form in a protein's tertiary structure?
between the carboxyl and amino groups not involved in the peptide bonds
99
how strong are the ionic bonds formed in a protein's tertiary structure compared to other bonds?
weaker than disulphide bridges
100
what are ionic bonds in a protein's tertiary structure broken by?
pH
101
describe the hydrogen bonds in a protein's tertiary structure
numerous and easily broken
102
what two kinds of proteins are there?
globular and fibrous
103
what is the difference between globular and fibrous proteins?
globular are compact, whereas fibrous are long and therefore can be used to form fibres
104
what is the biochemical test for proteins
the biuret test
105
describe the steps to carry out the biuret test and give the positive result
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
what do enzymes do?
increase the rate of reaction
107
how do enzymes increase the rate of reaction?
by lowering the activation energy by providing an alternative reaction pathway
108
describe the general structure of an enzyme
3D tertiary structured globular proteins
109
what determines an enzymes shape?
the primary sequence of amino acids
110
what is an enzyme's active site?
area of an enzyme that forms a small depression in the enzyme
111
what is the substrate?
the molecule that the enzyme acts upon
112
explain the induced fit model of enzyme action
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
give five factors that affect the rate of enzyme-controlled reactions
temperature
pH
enzyme concentration
substrate concentration
inhibitor concentration
114
how does increasing temperature affect the rate of enzyme-controlled reaction?
RoR increases up to the optimum temperature as enzyme's kinetic energy increases
Above optimum, RoR decreases as enzyme becomes denatured
115
how does changing pH affect the rate of enzyme-controlled reaction?
Enzymes have an optimum pH
Above and below the optimum the shape gets altered and so it becomes denatured
116
how does increasing enzyme concentration affect the rate of enzyme-controlled reaction?
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
how does increasing substrate concentration affect the rate of enzyme-controlled reaction?
RoR increases as more E-S complexes are formed
However only to a point as eventually enzyme concentration becomes the limiting factor
118
how does increasing concentration of competitive inhibitor affect the rate of enzyme-controlled reaction?
RoR decreases as the active sites become blocked preventing substrates binding to them
119
how does increasing concentration of non-competitive inhibitors affect the rate of enzyme-controlled reaction?
RoR decreases as the shape of the enzyme is altered by the inhibitors, preventing E-S complexes forming
120
what does DNA do?
holds genetic information
121
what does RNA do?
transfers genetic information from DNA to ribosomes for protein synthesis
122
what are the components of any nucleotide?
pentose sugar
organic base
phosphate group
123
what are the components of a DNA nucleotide?
deoxyribose sugar
phosphate group
organic base
124
name the four organic bases that a DNA nucleotide could have
adenine
cytosine
guanine
thymine
125
what are the components of an RNA nucleotide?
ribose sugar
phosphate group
organic base
126
name the four bases that an RNA nucleotide could have
adenine
cytosine
guanine
uracil
127
what bonds join nucleotides? between what?
phosphodiester bonds
the deoxyribose sugar and one nucleotide and the phosphate group of another
128
describe the structure of a DNA molecule
double helix composed of two polynucleotides joined by hydrogen bonds between complementary bases
129
what bonds join complementary base pairs in a DNA molecule?
hydrogen bonds
130
what are the four key differences between the structure of DNA and RNA
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
state the complementary base pairing of adenine, thymine, guanine, and cytosine
A - T
G - C
132
what are ribosomes formed from?
RNA and proteins
133
give the name of the process by which DNA replication occurs
semi-conservative replication
134
what is the advantage of semi-conservative replication?
ensures genetic continuity between generations
135
describe the process of semi-conservative replication of DNA
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
name the two enzymes involved in DNA replication
DNA helicase
DNA polymerase
137
what is the role of DNA helicase in DNA replication?
separates the two DNA strands by breaking the hydrogen bonds between bases
138
what is the role of DNA polymerase in DNA replication?
catalyses the formation of phosphodiester bonds
139
what are the components of ATP?
ribose
adenine
three phosphate groups
140
how is energy released from ATP?
when ATP is hydrolysed
141
what are the products of ATP hydrolysis?
ADP and a phosphate molecule
142
what enzyme catalyses ATP hydrolysis?
ATP hydrolase
143
where does the energy released in ATP hydrolysis come from?
the bonds between the phosphate molecules
144
why are the bonds between phosphate molecules in ATP easily broken?
because they are unstable and have a low activation energy
145
how can the inorganic phosphate from ATP be used?
to phosphorylate other compounds, making them more reactive
146
how is ATP produced? give the enzyme
condensation of ADP and inorganic phosphate
catalysed by ATP synthase
during photosynthesis and respiration
147
why is ATP more desirable to use than glucose?
because it can be broken down in a single step to release a more manageable amount of energy
148
why is ATP not stored in large quantities?
as it can easily be reformed from ADP in seconds
149
give five uses of ATP
metabolic processes
movement
active transport
secretion
activation of molecules
150
why is water a polar molecule?
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
give six key properties of water
polar
metabolite
solvent
high specific heat capacity
high latent heat of vaporisation
cohesive
152
how is water a metabolite? give two examples
in metabolic reactions such as condensation and hydrolysis
153
why is water useful as a solvent?
most metabolic processes take place in solution
154
explain how water's high specific heat capacity is useful for living organisms
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
why does water have a high specific heat capacity and high latent heat of vaporisation?
because it has strong hydrogen bonding
156
what is latent heat of vaporisation (of water)?
the energy required to evaporate 1 gram (of water)
157
explain how water's large latent heat of vaporisation is useful for living organisms
it means evaporation of water provides a cooling effect with little water loss
e.g. by sweating
158
what does water's strong cohesion allow?
transport of water in tubes e.g. in the xylem
159
what is an effect of water's strong cohesion?
the surface tension at the water-air boundary is high
160
where do inorganic ions occur?
in solution in the cytoplasm and body fluid of organisms
161
give four essential inorganic ions
hydrogen ions
iron ions
sodium ions
phosphate ions
162
what is the role of hydrogen ions in the body?
determine the pH of substances such as blood
163
what is the role of iron ions in the body?
a component of haemoglobin
164
what is the role of sodium ions in the body?
involved in co-transport of glucose and amino acids
165
what is the role of phosphate ions in the body?
a component of DNA and ATP
166
what is the R group of a fatty acid?
everything except the COOH
167
Describe two differences between thestructure of a triglyceride and a phospholipid
1. Triglyceride has 3 fatty acids whereas phospholipid has 2
2. Phospholipid contains a phosphate whereas triglyceride does not
168
Explain why phospholipids can form a bilayer but triglycerides cannot
-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
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
Capsid and attachment protein (option 2)
170
Name 2 enzymes that are involved in DNA replication and describe their roles in the process
1. DNA helicase - breaks hydrogen bonds between bases to separate the two strands
2. DNA polymerase - synthesis of phosphodiester bonds between bases
