1.1 chemical elements and biological compounds Flashcards
(432 cards)
1
Q
inorganic definition
A
a molecule or ion that has no more than one carbon atom
2
Q
organic definition
A
molecules that have a high proportion of carbon atoms
3
Q
why do living organisms need a variety of inorganic ions to survive?
A
they are important in many cellular processes, including muscle contraction and nervous coordination
4
Q
what are the two groups of inorganic ions?
A
- macronutrients - needed in small concentrations
- micronutrients - needed in minute (trace) concentrations e.g copper and zinc
5
Q
what are two examples of micronutrients?
A
- copper
- zinc
6
Q
what are four examples of macronutrients? (the key elements present as inorganic ions in living organisms)
A
- magnesium (Mg 2+)
- iron (Fe 2+)
- calcium (Ca 2+)
- phosphate (PO4 3-)
7
Q
what is the role of magnesium in living organisms?
A
- constituent (being a part of)/ component of chlorophyll (needed to make chlorophyll)
- and so needed for photosynthesis
- when lacking leaves appear yellow (chlorosis)
- mammals need magnesium for their bones
8
Q
when lacking magnesium, what happens to plants?
A
their leaves turn yellow (a condition known as chlorosis)
because they can’t make chlorophyll
9
Q
what is the role of iron in living organisms?
A
- constituent / component of haemoglobin
- so is involved in the transport of oxygen in red blood cells
- a diet deficient in iron (in humans) can lead to anaemia
10
Q
what can a diet deficient in iron lead to (in humans)?
A
anaemia
11
Q
what is the role of calcium in living organisms?
A
- important structural component of bones and teeth in mammals (along with phosphate)
- is a component of plant cell walls, providing strength
- HARDENS bones and teeth
12
Q
what is the role of phosphate ions in living organisms?
A
- needed for making nucleotides, including ATP
- are a constituent part of phospholipids, found in biological membranes (in cell membranes)
13
Q
condensation definition
A
the removal of a water molecule and the formation of a covalent bond between two biochemical groups
e.g glucose + glucose = maltose + water
14
Q
hydrolysis definition
A
the breaking down of large molecules into smaller ones by the chemical addition of a molecule of water
e.g lactose + water = glucose + galactose
15
Q
dipolar definition
A
a polar molecule with a positive and negative charge, separated by a very small distance
16
Q
hydrogen bond definition
A
the weak attractive force between a partially positively charged hydrogen atom and a partially negatively charged usually oxygen or nitrogen atom
17
Q
why is water vital to life on earth?
A
- it makes up between 65% and 95% by mass of most organisms (70% of each human is water)
- it allows important reactions to take place
- it forms a habitat that covers over 70% of the earth’s surface
- is an important constituent of cells
18
Q
what is the name for water’s basic structure?
A
it is a dipolar molecule
(it’s a dipole)
19
Q
why is water said to be dipolar?
A
it has a positively charged end (hydrogen) and a negatively charged end (oxygen) but has no overall charge
20
Q
what is a molecule with separated charges said to be?
A
‘polar’
21
Q
what do the majority of water’s properties arise from?
A
its dipolar nature and hydrogen bonding
22
Q
where can hydrogen bonds form in a water molecule?
A
between one of the hydrogen atoms of one molecule and the oxygen atom of another
23
Q
are hydrogen bonds weak?
A
yes - but the very large number of them present in water makes the molecules difficult to separate
(and gives water a wide range of physical properties vital to life)
24
Q
what are some of water’s properties that are vital to life?
A
- it’s an excellent solvent
- is has a high specific heat capacity
- it has a high latent heat of vapourisation
- it is a metabolite
- cohesion
- has a high surface tension
- has a high density
- is transparent
25
why is water an excellent solvent?
due to its dipolar nature, it attracts charged particles (such as ions) and other polar molecules (such as glucose), allowing them to dissolve
26
what is the importance of water being an excellent solvent?
- it is involved in many biochemical reactions e.g hydrolysis and condensation
- allows polar molecules e.g glucose and ions to dissolve (so chemical reaction take place)
- it acts as a transport medium e.g in animals = plasma transports dissolved substances and in plants = water transports minerals in the xylem, and sucrose and amino acids in the phloem
27
what is the importance of water being a metabolite?
- it’s involved in many biochemical reactions
e.g hydrolysis and condensation
- a reactant in photosynthesis
28
specific heat capacity definition
the heat needed to raise the temperature of 1kg of water by 1.C
29
what is the importance of water having a high specific heat capacity?
- a large amount of heat energy is needed to increase the temperature of a body of water (due to large numbers of hydrogen bonds that need to be broken)
- so large fluctuations in temperature are prevented
- aquatic environments are therefore relatively thermally stable (meaning organisms don’t have to adapt to extremes of temperatures)
- also allows enzymes within cells to work efficiently
30
what is the importance of water having a high latent heat of vaporisation?
- large amounts of heat energy are needed to vaporise water (liquid -> vapour)
- so it is often used as a cooling mechanism e.g sweating in mammals
- important in temperature control
- as the water evaporates, the body cools
31
what is latent heat?
the heat or energy that is absorbed or released during a state change of a substance
(solid-> liquid -> gas)
(gas-> liquid-> solid)
32
what is the importance of cohesion of water?
- water molecules attract each other and form hydrogen bonds between themselves
- individually these are weak, but, because there are many of them, the molecules stick together in a lattice (this sticking together is called cohesion)
- it allows columns of water to be drawn up the xylem vessels of plants/trees
33
why does water have a high specific heat capacity?
- due to large numbers of hydrogen bonds that need to be broken
- the hydrogen bonds between water molecules restrict the movement of water molecules, resisting an increase in kinetic energy and therefore, resisting an increase in temperature
34
what is the importance of water having high surface tension?
- in a pond, cohesion between water molecules at the surface produces surface tension so that the body of an insect, such as the pond skater, is supported
35
what makes water have a high surface tension?
cohesion between water molecules at the surface
36
what is the importance of water being high density?
- ice floats (as it’s less dense than liquid water)
- it acts as an INSULATING LAYER preventing the water beneath from freezing completely, protecting the aquatic habitat
so life can survive when ice forms
37
at what temperature does water have a maximum density?
4.C
38
why is ice less dense than liquid water?
bc the hydrogen bonds hold the molecules further apart than they are in the liquid
39
what is the importance of water being transparent?
- it allows light to pass through, enabling aquatic plants to photosynthesise effectively
40
what are carbohydrates? what elements does it contain?
small organic molecules/compounds containing carbon, oxygen and hydrogen
41
what are the functions of carbohydrates/monosaccharides and what do they act as?
- building blocks for more complex/larger molecules e.g glucose is used to make glycogen and cellulose
- sources of energy in respiration e.g glucose
- energy storage molecules e.g glycogen and starch
- structural support e.g cellulose and chitin
- constituents of nucleotides e.g deoxyribose in DNA, ribose in RNA, ATP and ADP
42
in carbohydrates, what is the basic monomer/unit?
a monosaccharide
(simple sugar units)
43
what do two monosaccharides combine to form?
a disaccharide
44
what do many monosaccharide molecules combine to form?
a polysaccharide
45
what are some basic properties of monosaccharides?
- sweet tasting
- soluble in water
- small organic molecules
- are the building blocks for the larger carbohydrates
46
what is the general formula of monosaccharides?
(CH2O)n
‘n’ is any number between 1 and 7
47
what are the names of monosaccharides determined by?
the number of carbon atoms (n) in the molecule
48
how many carbon atoms does a triose sugar have?
3 carbon atoms
49
how many carbon atoms does a pentose sugar have?
five
50
how many carbon atoms does a hexose sugar have?
six
51
what type of sugar is glucose an example of?
a hexose sugar (C6H12O6)
52
what is the importance of triose sugars?
they are important in respiration pathways
- important in metabolism - intermediates in the reactions of respiration and photosynthesis
53
what is the importance of pentose sugars?
e.g ribose and deoxyribose
- are important constituents of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)
54
what is the importance of glucose?
- it is the starting material for respiration
- is the building block of glycogen and other polypeptides
55
what are some examples of other hexose sugars (other than glucose)?
- galactose
- fructose
56
isomers definition
molecules that have the same chemical formula but different structure
57
how many isomers does glucose have?
2
- alpha-glucose
- beta-glucose
58
what is the difference between alpha-glucose and beta-glucose?
the positions of an (OH) and a (H) is swapped
59
what does the difference between the alpha-glucose and beta-glucose result in?
- it results in biological differences when they form polymers, such as starch and cellulose
- it affects the way in which they join to other molecules
60
how are disaccharides formed?
- by joining two monosaccharides together with the formation of a glycosidic bond and the elimination of water
- via a condensation reaction
61
what reaction can break down polymers and disaccharides into monomers?
hydrolysis reaction
(breaking the chemical bond using a water molecule)
62
what monosaccharides make maltoes?
(alpha-)glucose + (alpha-)glucose
63
what is the biological role of the disaccharide maltose?
in germinating seeds
64
what monosaccharides make sucrose?
glucose + fructose
65
what is the biological role of the disaccharide sucrose?
transport in phloem of flowering plants
- a product of photosynthesis which is transported in the phloem
66
what monosaccharides make lactose?
glucose + galactose
67
what is the biological role of the disaccharide lactose?
in mammalian milk
68
what are the prefixes of 1-6 carbon atoms? many carbon atoms?
1 - mono
2 - di
3 - tri
4 - tetra
5 - penta
6 - hexa
many - poly
69
if carbohydrate is the biological molecule, what is the monomer and polymer?
monomer - monosaccharide
polymer - polysaccharide
70
if protein is the biological molecule, what is the monomer and polymer?
monomer - amino acids
polymer - proteins and polypeptides
71
if nucleic acid is the biological molecule, what is the monomer and polymer?
monomer - nucleotide
polymer - DNA
72
what are some examples of monosaccharides?
- glucose
- fructose
- galactose
73
what are some examples of disaccharides?
- sucrose
- maltose
- lactose
74
what are carbohydrates (polysaccharides) used for in plants and animals?
1. storage
2. structure
75
how are polysaccharides used for storage in plants? in animals?
- glycogen and starch are storage carbohydrates
- animal cells store glucose as glycogen
- plant cells store glucose as starch
76
what do animal cells store glucose as?
glycogen
77
what do plant cells store glucose as?
starch
78
how are polysaccharides used for structure?
- cellulose and chitin are important structural carbohydrates
- cellulose forms the fabric of many cell walls
- chitin is a major component of the exoskeleton of many arthropods
79
how is cellulose used in structure?
- it forms the fabric of many cell walls
80
why is water a polar molecule?
O is more electronegative than H.
O attracts the electron density in the covalent bond more strongly, forming (smaller charge) - O and (smaller charge) + H
81
describe hydrogen bonding between water molecules
weak intermolecular forces of attraction form between a lone pair on a (small charge) -O and a (small charge) + H on an adjacent molecule
82
what is a metabolite?
a molecule formed or used in metabolic reaction
83
describe the role of water as a metabolite
- water is a reactant in photosynthesis and hydrolysis reactions
- water is a product in aerobic respiration and condensation reactions
84
what is the name of the bond formed when two monosaccharides react?
glycosidic bond
85
what are some examples of polysaccharides?
- starch
- glycogen
- cellulose
- chitin
86
what is the test for the presence of reducing sugars?
the Benedict’s test
87
what are examples of reducing sugars? (sugars that act as a reducing agent)
it includes all monosaccharides and some disaccharides e.g maltose
88
how is the Benedict’s test for detecting sugars carried out?
- equal volumes of Benedict’s reagent and the solution being tested are heated to at least 70.C (in a hot water bath)
- if a reducing sugar, such as glucose, is present, the solution will turn from blue through green, yellow and orange and finally a brick-red precipitate forms
89
what temperature is the solution and Benedict’s reagent heated to when testing for sugars?
at least 70.C
90
if a reducing sugar is present, what colour will the solution turn?
from blue through green, yellow and orange and finally a brick-red precipitate will form
91
what happens in terms of electrons when the test for sugar is carried out?
the sugars donate an electron to reduce copper (II) ions in copper sulphate, to red copper (I) oxide
Cu2+ + e- ——> Cu+
blue red
92
what is an example of a non-reducing sugar?
some disaccharides such as sucrose
93
what result do non-reducing sugars give when tested for sugar?
a negative one - the solution remains blue
94
what must be done for a non-reducing sugar e.g sucrose to be detected in a test for sugar?
it must be first broken down to its constituent monosaccharides, e.g by heating with hydrochloric acid
(benedict’s reagent needs alkaline conditions to work, so alkali is added. benedict’s reagent is then added and heated as before.)
if the solution now turns red then a non-reducing sugar was initially present
95
what condition does benedict’s reagent need to work?
alkaline conditions
96
what is the second way of detecting sucrose?
- by using sucrase, an enzyme that hydrolyses sucrose into glucose and fructose
the benedicts test will then give a positive result
97
what is a disadvantage of using the enzyme sucrase to help sucrose get detected in the test for sugars?
enzymes are specific. sucrase will only hydrolyse sucrose, so other non-reducing sugars will still give a negative result
98
why is the Benedicts test to detect sugars described as a semi-quantitative test?
- if 2 solutions w/ different concentrations have the same treatment in the Benedict’s test, the more concentrated will have a greater colour change
- the test doesn’t actually measure the concentration, but indicates which solution is more concentrated
99
what is a quantitative measurement (for example when testing for the presence of sugars)
giving an actual value to the concentration of sugar present
100
how do you accurately obtain the actual value to the concentration of sugar when testing for it?
by using a biosensor
101
what is an example of when it is important to know the actual value to the concentration of sugar present?
in monitoring medical conditions such as diabetes, where an accurate measurement of the concentration of blood glucose is required
102
what is the main source of energy in cells?
glucose
(and it must be stored in an appropriate form)
103
is glucose soluble in water? why is it a problem?
yes - it is soluble in water
so it would increase the concentration of the cell contents and consequently draw water in by osmosis
104
what are polysaccharides formed from?
very large numbers of monosaccharides units, which are their monomers, linked by glycosidic bonds
105
how is the problem of glucose being soluble in water avoided?
by converting the glucose into a storage product, a polysaccharide, starch
106
why does converting glucose into a storage product avoid the problem of glucose being soluble in water?
- it is insoluble so has no osmotic effect
- it cannot diffuse out of the cell
- it is a compact molecule and can be stored in a small space
- it carries a lot of energy in its C-H and C-C bonds
107
where are starch grains found in high concentrations?
in seeds and storage organs such as potato tubers
108
what is starch made of?
alpha-glucose molecules bonded together in two different ways, forming the polymers amylose and amylopectin
109
what are the two polymers that starch make?
amylose and amylopectin
110
what is amylose?
a linear, unbranched molecule with an alpha-1,4-glycosidic bonds
this is repeated, forming a chain, which coils into an alpha-helix
111
what does an alpha-1,4-glycosidic bond mean?
it forms a glycosidic bond between the first carbon atom (C1) on one glucose monomer and the fourth carbon atom (C4) on the adjacent one
112
what is amylopectin?
- has chains of glucose monomers
- joined with alpha-1,4-glycosidic bonds
- they are cross-linked with alpha-1,6-glycosidic bonds
- they fit inside the amylose
- when a glycosidic bond forms between the C1 atom on one glucose molecule and the C6 atom on another, a side branch is seen
- alpha-1,4-glycosidic bonds continue on from the start of the branch
113
what would happen if a cell absorbs too much water?
its solutes would not be at the appropriate concentration for the cell’s reaction
114
what would happen if an animal cell absorbs too much water?
it would burst
115
what bonds are amylose molecules joined by?
alpha-1,4-glycosidic bonds
116
what bonds are amylopectin molecules joined by?
both alpha-1,4-glycosidic bonds and alpha-1,6-glycosidic bonds
117
what is the test for the presence of starch?
-iodine solution (iodine dissolved in an aqueous solution of potassium iodide) reacts with starch
- resulting in a colour change from orange-brown to blue black
118
what is the colour change for a positive test of starch?
from orange-brown to blue-black
119
is the test for the presence of starch a qualitative or quantitative test ?
qualitative - an accurate concentration cannot be determined
120
what is the colour change for the test for the presence of sugars?
from blue through green, yellow and orange and finally a brick-red precipitate forms
121
what does the depth of blue-black colour give an indication of in the test for the presence of starch?
it gives an indication of relative concentration
(making it a qualitative test)
122
what happens to the test for the presence of starch above about 35.C? at very low pH?
- as temperature increases, the colour intensity decreases so above about 35.C, this test is unreliable
- it is also unreliable at very low pH, as the starch is hydrolysed
123
what is glycogen?
- the main storage product in animals
- used to be called animal starch bc it is very similar to amylopectin
- also has alpha-1,4 and alpha-1,6 bonds
- but has shorter alpha-1,4-linked chains and so are more branched than amylopectin
124
what bonds is glycogen joined by?
both alpha-1,4 and alpha-1,6 glycosidic bonds
125
what is the difference between glycogen molecules and amylopectin?
glucose molecules have shorter alpha-1,4-linked chains and so are more branched than amylopectin
126
what is cellulose?
- a structural polysaccharide
- its presence in plant cell walls makes it the most abundant organic molecule in earth
- consists of many long, parallel chains of beta-glucose units
127
what does cellulose consist of?
many long parallel chains of beta-glucose units
128
both ____ and ____ are readily hydrolysed to alpha-glucose, which is soluble and can be transported to where energy is needed
starch and glycogen
129
what is different about the glucose monomers in cellulose?
the glucose monomers are joined by beta-1,4-glycosidic bonds, and the beta-link rotates adjacent glucose molecules by 180.
(this allows hydrogen bonds to form between the OH groups of adjacent parallel chains and contributes to cellulose’s structural stability
130
what does the beta-link rotating adjacent glucose molecules by 180. allow to happen?
this allows hydrogen bonds to form between the (OH) groups of adjacent parallel chains and contributes to cellulose’s structural stability
131
what do between 60 and 70 cellulose molecules become? to form what?
- tightly cross-linked
- to form bundles called microfibrils
- which are, in turn, held in bundles called fibres
132
what are the bundles that hold microfibrils in cellulose called?
fibres
133
how many layers of fibres does a cell wall have? how are they found?
- several layers of fibres
- they run parallel within a layer but at an angle to the adjacent layers
(this laminated structure also contributes to the strength of the cell wall)
134
why are cellulose fibres described as freely permeable?
- because there are spaces between the fibres
- water and its solutes can penetrate through these spaces in the cell wall, to the cell membrane
135
when writing about cellulose in the cell wall, what must you always write?
plant cell wall
rather than cell wall because the cell walls of fungi and bacteria do not contain cellulose
136
what is chitin?
- a structural polysaccharide
- found in the exoskeleton of insects and in fungal cell walls
- it resembles cellulose, but has groups derived from amino acids added
- it is strong, waterproof and lightweight
137
where is chitin found?
- in the exoskeleton of insects
- in fungal cell walls
138
how does chitin resemble cellulose?
- with its long chains of beta-1,4-linked monomers
- the monomers are rotated through 180. in relation to their neighbour, and the long parallel chains are cross-linked to each other by hydrogen bonds, forming microfibrils
139
how is chitin different to cellulose? (in terms of resemblance)
it has groups derived from amino acids added, to form a heteropolysaccharide
140
what do the groups derived from amino acids added to chitin form?
a heteropolysaccharide
141
due to what makes amylopectin rapidly digested by enzymes therefore energy is released quickly?
due to the presence of many side branches
142
is chitin strong?
yes - it’s lightweight but strong
143
while ions are all charged, what can molecules have?
- no charge - non polar
- or a slight charge - polar
144
what does polar mean? non-polar? ( in terms of molecules)
polar - slight charge
non-polar - no charge
145
is a mixture a pure substance?
no - they can be divided by physical means
146
what does it mean if it’s a pure substance?
it can’t be broken down into smaller parts without a chemical or nuclear reaction
147
do particles with a charge (ions or polar molecules) have different properties from molecules with no charge (non-polar)
yes :
- ions and polar compounds attract oppositely charged particles and play important roles in the structure of molecules
- non-polar compounds do not dissolve in water but will dissolve in lipids (fats/oils) - they are said to be lipid-soluble
148
is water a polar molecule?
yes - but it has no overall charge, because the hydrogen atoms have a partial positive charge and the oxygen atoms have a partial negative charge
149
why do water molecules attract each other (by forming hydrogen bonds)?
because of their polarity
(also because of their polarity, water molecules are attracted to other water molecules and charged particles which helps charged particles dissolve in water)
150
why is water sometimes referred to as the universal solvent?
- because of their polarity, water molecules are attracted to other water molecules and charge particles.
- this helps charged particles dissolve in water
- a large number of substances can dissolve in water so it referred to as the universal solvent
151
what are examples of structural isomers?
glucose, galactose and fructose
they have the same molecular formula C6H12O6
152
what is a way to remember the position of the OH group in alpha-glucose and beta-glucose?
ABBA
Alpha OH Below - Beta OH Above
153
what isomer of glucose are both starch (plants) and glycogen (animals) made of?
alpha-glucose
154
what two different polysaccharides is starch a mixture of?
amylose (which forms coiled molecules) and amylopectin (a branched molecule)
155
why is starch known as osmotically stable?
because starch is insoluble it does not affect the water potential of the cell in which it is stored, making it osmotically stable
(also, starch is a compact molecule that is less soluble in water (ideal properties for storage of glucose))
156
what can glycogen form in cells? what can it act as?
- it can form granules in cells
- and act as a carbohydrate/energy store
157
what makes amylopectin and glycogen better for the release of glucose? why?
the branches - this is because there are more ‘ends’ where glycosidic bonds can be hydrolysed and glucose released, which can be used in respiration to produce ATP
158
what does the beta-1,4-glycosidic linkages of cellulose result in?
the -CH2OH groups being on opposite sides of the chain of adjacent glucose molecules
159
why is it important that within a cellulose chain, adjacent glucose molecules are rotated 180. relative to each other?
this means that OH groups are aligned and a water molecule can be removed to form a glycosidic bond
160
where do hydrogen bonds form in cellulose?
they DON’T form between glucose molecules within the same chain, but between glucose molecules in different chains
(the hydrogen bonds form cross-linkages which hold the chains together)
161
what holds the chains in cellulose together?
the hydrogen bonds form cross-linkages which hold the chains together
(this makes cellulose form into long threads called microfibrils)
162
is cellulose insoluble or soluble?
completely insoluble
163
how are microfibrils laid down in plant cell walls?
they are laid down in overlapping layers in plant cell walls
164
why is cellulose very difficult to digest?
because of the very high numbers of hydrogen bonds between the chains of beta glucose
(this also gives cellulose very high tensile strength; it is difficult to break when stretched)
165
why are cells with cellulose in their cell walls more resistant to osmotic lysis (they are not likely to burst)
cellulose has a very high tensile strength so it’s difficult to break when stretched.
(they are not likely to burst because cellulose stops too much water entering the cell)
166
why is chitin not a true polysaccharide?
it contains the element nitrogen - it is called a heteropolysaccharide
167
why can more hydrogen bonds form in chitin?
because it contains side groups containing nitrogen
168
why do chitin microfibrils have greater tensile strength than those of cellulose?
because more hydrogen bonds can form because chitin contains side groups containing nitrogen
169
what is the insoluble brick red precipitate that forms during the benedict’s test for sugars?
copper (I) oxide
because Benedict’s reagent is an alkaline solution of copper (II) sulphate
170
when does glucose exist in ring form?
when glucose is dissolved in water (in solution)
171
are all monosaccharides reducing sugars?? why?
yes - the C=O group has reducing properties
172
what are the functions of monosaccharides?
- a source of energy in respiration (C-H and C-C bonds broken)
- building blocks for larger molecules
- constituent of nucleotides
173
is sucrose a reducing sugar?
no
174
is maltose a reducing sugar?
yes
175
what does boiling sucrose (a reducing sugar) do (in order for the benedict’s test to work?
breaks glycosidic bond which releases free glucose and free fructose
176
why do you need to neutralise sucrose after you boil it in HCl when testing for non-reducing sugars?
because the Benedict’s test requires an alkali medium
177
what allows easy access for enzymes when breaking down the molecule, making starch an ideal food storage compound?
the many branches
178
what type of bond holds the cellulose molecules together side by side?
hydrogen bonds
179
explain the difference in structure of the starch molecule and the cellulose molecule?
- starch is made up of alpha-glucose molecules while cellulose is made from beta-glucose
- this is seen by the inversion of the H and OH groups in cellulose
180
explain one way in which starch molecules are adapted for their function in plant cells?
- starch is helical in shape -> makes them compact -> good for storage molecules
OR
- starch is insoluble so it doesn’t alter the water levels of cells/affect water potential
181
explain how cellulose molecules are adapted for their function in plant cells?
- cellulose molecules are long chains
- which are linked by hydrogen bonds
- which strengthed the cellulose so provides structure to the cell walll
182
describe how you would test a sample of food for the presence of starch?
- add iodine solution
- if starch was present = brown-> blue/black
183
describe a chemical test you could carry out on a sample to show that lactose is a reducing sugar?
- boiling/heating in Benedict’s for 5 mins to 70.C
- from blue-> orange
184
state three properties shared by lipids
1. insoluble in water
2. soluble in organic solvents such as ethanol
3. comprised of carbon, hydrogen and oxygen
185
describe the structure and process of bonding within triglycerides
3 fatty acids are ester bondrd via a condensation reaction tona glycerol molecule
186
what are two differences between triglycerides and phopholipids?
1. one of the fatty acids in phospholipids is replaced by a phosphate molecule (makes them polar)
2. phosphate molecules attract water (hydrophilic) whereas fatty acid molecules repel water (hydrophobic)
187
what do lipids consist of?
carbon, oxygen and hydrogen
188
what is the difference in proportion of carbon, hydrogen and oxygen do lipids have?
they contain much less oxygen
189
are lipids polar or non-polar compounds?
non-polar compounds so are insoluble in water
190
are lipids soluble or insoluble in water?
insoluble
191
are lipids soluble or insoluble in organic solvents?
soluble
192
how are triglycerides formed? (a combination of what?)
by the combination of one glycerol molecule and three molecules of fatty acids
193
is the glycerol molecule in a lipid always the same?
yes
194
are the fatty acid molecules in a lipid always the same?
no - the fatty acid components vary
195
what type of reaction join the fatty acids to glycerol when making a lipid?
condensation reaction
(3 molecules of water are removed and ester bonds are formed between the glycerol and fatty acids)
196
what is the unusual property that phospholipids have?
each molecule has one end that is soluble in water (has lots of oxygen atoms) (is hydrophilic)
(the polar head of the molecule)
197
are waxes lipids?
yes
198
at what temperature do waxes melt at?
above 45.C
199
what role do waxes have in both animals, such as in the insect exoskeleton, and plants, in the leaf’s cuticle?
they have a waterproofing role
200
what do the differences in the properties of fats and oils come from?
variations in the fatty acids
201
what is a fatty acid said to be if the hydrocarbon chains has only single carbon-carbon bonds? why?
saturated
because all the carbon atoms are linked to the maximum possible number of hydrogen atoms
(they are saturated with hydrogen atoms)
202
what are the properties of a saturated fat?
- the molecules can align readily so fats are solid
- remain solid at room temperature
- and so are useful for storage in mammals
203
what do animal lipids often contain?
saturated fatty acids
204
are saturated fats in a stright line?
yes
205
what state are unsatutated fats at room temperature?
- oils
- remain liquid at room temperature
206
are plant lipids often saturated or unsaturated?
unsaturated
(often occur as oils such as olive oil and sunflower oil)
207
if one carbon-carbon double bond is present, what is the lipid called?
a mono-unsaturatrd lipid
208
if there are many carbon-carbon double bonds, what is thr lipid described as?
polyunsaturated
209
what are the roles of phospholipids?
- in biological membranes
- electrical insulation - the myelin sheath that surrounds the axons of nerve cells
210
what are the roles of triglycerides?
- energy reserves in both plants and animals, bc lipids contain more carbon-hydrogen bonds than carbohydrates
- thermal insulation - when stored under the skin lipids insulatr against heat loss in the cold or heat gain when it is very hot
- protection - fat is often stored around delicate internal organs such as kidneys, protecting against physical damage
- metabolic water - this is water released during chemical reactions in the body. triglycerides produce a lot of metabolic water when oxidised
211
when do triglycerides produce a lot of metabolic water?
when oxidised
212
what are the roles of waxes?
- waterproofing - in terrestrial organisms, waxes reduce water loss, such as in the insect exoskeleton and in the cuticle of plants
213
what is the test for fats and oils?
the emulsion test
214
what is the emulsion test?
- a sample to be tested is shaken with absolute ethanol, which dissolves any lipids present
- it is shaken with an equal volume of water
- the dissolved lipids come out of solution, because they are insoluble in water
- they form an emulsion, making the sample cloudy white
215
what are the main causes of heart disease?
- fatty deposits in the coronary arteries (atherosclerosis)
-high blood pressure (hypertension)
216
what increases atherosclerosis and high blood pressure?
- a diet high in saturated fats
- smoking
- lack of exercise
- aging
217
what happens to the lipids and proteins after the food has been absorbed at the small intestine?
lipids and proteins combine to make lipoproteins, which travel around the body in the blood stream
218
what happens if the diet is high in saturated fats?
- low-density lipoproteins (LDL) build up and cause harm
- fatty material called atheroma gets deposited in the coronary arteries, restricting blood flow and, therefore, oxygen delivery to the heart
- it can result in angina, and, if thr vessel is completely blocked, a myocardial infarction or heart attack occurs
219
what happens if the diet is high in unsaturated fats?
- the body makes more high-density lipoproteins (HDL) which carries harmful fats away to the liver for disposal
- the higher the ratio of HDL:LDL in a person’s blood, the lower their risk of cardio-vascular and coronary heart disease
220
do lipids serve as structural or nutrient substances?
both
221
what does the lipid group include?
- fats and oils
- waxes
- steroids
- phospholipids
222
the proportion of carbon to oxygen and hydrogen is smaller in lipids than in what?
carbohydrates
223
what are some examples of organic solvents that lipids are soluble in?
ethanol (alcohols), chloroform and acetone
224
what are the roles of lipids?
- contribute to the flexibility of cell membranes
- source of energy
- waterproofing
- thermal insulation
- protection
- buoyancy
225
what are triglycerides?
fats and oils are formed from molecules of glycerol and fatty acids - these compounds are triglycerides
226
why are triglycerides an excellent source of energy?
they have a higher ratio of energy- storing carbon-hydrogen bonds to carbon atoms
227
why are triglycerides a good storage molecule?
they have a low mass to energy ratio, making them a good storage molecule because much energy can be stored in a small volume
228
why does triglycerides being large, non polar molecules and therefore are insoluble in water, valuble to them?
their storage does not affect osmosis in cells or the water potential of them
229
why are triglycerides an important source of water? (especially for organisms in dry deserts)
they have a high ratio of hydrogen to oxygen atoms, so they release water when oxidised
230
what is thr general formula for a saturated fatty acid?
O
II
HO - C - (CH2)n - CH3
231
what fats are the animal fats?
saturated fats
232
the greater the number of double bonds (in fats), thr ____ the temperature at which the lipid melts?
the lower the temperature
233
what is a monoglyceride?
a single fatty acid molecule bonds with the glycerol molecule
234
what is a diglyceride?
two fatty acid molecules bond with the glycerol molecule
235
where do inorganic ions occur?
in solution in the cytoplasm and body fluid of organisms, some in high concentrations and others in very low concentrations
236
is water a metabolite?
yes
in metabolic reactions such as condensation and hydrolysis
237
what isomer of glucose is glycogen formed from?
it is formed by the condensation of alpha glucose
238
what isomer of glucose is starch formed from?
formed by the condensation of alpha glucose
239
what isomer of glucose is cellulose formed from?
formed by the condensation of beta glucose
240
does glycogen have a large number of side branches?
yes - meaning that energy can be released quickly
241
is glycogen a large molecule?
is it compact?
yes - it’s a relatively large molecule
yes - (even tho it’s large) it’s compact
= maximising the amount of energy it can store
242
what is a mixture of amylose and amylopectin?
starch
243
is amylose a branched or unbranched chain of glucose molecules?
unbranched
244
what property makes amylose coiled?
it’s an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds
245
is amylose compact?
yes - it’s a very compact molecule
meaning it can store a lot of energy
246
can amylose store a lot of energy?
yes - because it’s very compact because it’s coiled
247
is amylopectin branched or unbranched?
branched
248
what property makes amylopectin rapidly digested by enzymes?
due to the presence of many side branches
so is rapidly digested by enzymes therefotr energy is released quickly
249
is cellulose branched or unbranched?
unbranched (chains of beta glucose)
250
what are microfibrils?
- strong threads which are made of long cellulose chains joined together by hydrogen bonds
- provide structural support in plant cells
251
what isomer of glucose is chitin made from?
made of chains of beta glucose monomers (with amino acid side chains)
- one OH group of each beta glucose molecule is replaced with an amino acid
252
what kind of side chains does chitin have?
amino acid side chains
- one OH group of each beta glucose molecule is replacrd with an amino acid
253
what is chitin used to form? (why?
the exoskeletons of insects
because it is lightweight but strong
254
what can too much saturatrd fat do to your body?
- increase the cholesterol levels in blood
- so increasing the risk of coronary heart disease
255
do saturated or unsaturated fats melt at lower temperatures?
unsaturatrd fats
256
why are unsaturated fats healthy?
as they provide essential fatty acids
257
why is it that the greater the number of unsaturated bonds, the lower the melting point?
because the weaker the intermolecular bonds
258
what state are saturated fats at room temperature?
solid
259
what state are unsaturated fats at room temperature?
liquid
260
what are triglycerides used as in animal and plant cells?
as energy reserves in plant and animal cells
261
are phosphate heads hydrophilic or hydrophobic?
hydrophilic
262
are the tails of phospholipids hydrophilic or hydrophobic?
hydrophobic
263
why do phospholipids form micelles when they are in contact with water?
- as phosphate heads are hydrophilic and the tails are hydrophobic
- as heads are on the outside as they are attracted to water and tails are on the inside as they move away from water
264
how do proteins differ from carbohydrates and lipids (based on what they contain)?
in addition to carbon, hydrogen and oxugen, they always contain nitrogen
(many proteins also contain sulphur and some contain phosphorus)
265
what are the polymers of protein made of?
monomers called amino acids
266
what are the chains of amino acids called?
polypeptides
267
how many different amino acids are used to make up proteins?
about 20
268
what is the shape of different proteins determined by?
the specific sequence of amino acids in the chain
269
what does the basic structure that all amino acids have contain?
- an amino group -NH2 (the N-terminal)
- a carboxyl group -COOH (the C-terminal)
- a hydrogen atom
- the R group which is different in each amino acid
270
is the amino group of an amino acid basic or acidic?
basic
at pH7, the pH of the cell, it gains an H and becomes positively charged
271
is the carboxyl group of an amino acid basic or acidic?
acidic
at pH7, it loses an H, becoming negatively charged
272
are proteins linear sequences of amino acids?
yes
273
how does a peptide bond form?
- the amino group of one amino acid reacts with the carboxyl group of another with the elimination of water
- the bond that is formed from this condensation reaction is a peptide bond, and the resulting compound is a dipeptide
274
is the dipeptide NH2-R1-R2-COOH the same or different to NH2-R2-R1-COOH?
it’s a different dipeptide with different properties
275
how can the structure of a protein be thought of?
at different levels of organisation:
- primary structure
- secondary structure
- tertiary structure
- quaternary structure
276
what is the primary structure of a protein?
the sequence of amino acids in a polypeptide chain
(the 20 amino acids can be joined in any number, order and combination = huge number of possible polypeptides)
based on:
- which amino acids present
- the number of each type of amino acid
- the sequence of amino acids
277
what is the primary structure of a proteins determined by?
the base sequence on one strand of the DNA molecule
(+ the order of amino acids in the polypeptide chain)
278
what is the secondary structure of a protein?
- shape bc of folding of a polypeptide chain
- of hydrogen bonding beyween the =O on -CO groups and the -H and -NH groups in the peptide bonds along the chains
279
between what does the hydrogen bonding occur in the secondary structure of proteins?
between the =O on -CO groups and the -H on -NH groups in the peptide bonds along the chain
280
what causes the long polypeptide chain to be twisted into a 3D shape (in the secondary structure)
the hydrogen bonds between tbe =O and -H
(the spiral shape is the a-helix)
281
what are the two types of secondary structure of proteins?
1. alpha-helix
2. beta pleated sheet (less common)
282
what does the protein keratin have a high proportion of?
alpha-helix
283
what does the protein fibroin (in silk) have a high proportion of?
beta-pleated sheet
284
what is the tertiary structure of a protein?
the alpha-helix of the secondary structure can be folded and twisted to give a more complex, compact 3D structure
- can be globular or fibrous
285
what is the shape of the tertiary structure of a protein maintained by?
- hydrogen bonds
- ionic bonds
- disulphide bonds
- hydrophobic interactions
(these bonds are important in giving globular proteins e.g enzymes, their shape)
286
what is the quaternary structure of proteins?
(some polypeptide chains are not functional unless they are in combination)
- in some cases, they may combine with another polypeptide chain, e.g insulin
- they may also be associated with non-protein groups and form large, complex molecules, such as haemoglobin
287
what do the roles of proteins depend on?
their molecular shape
288
what are fibrous proteins?
- they have long, thin molecules
- their shape makes them insoluble in water
- so they have structural functions, as in bones
- the polypeptides are in parallel chains or sheets, with many cross-linkages forming long fibres
- they are strong and tough
289
are fibrous proteins soluble or insoluble in water?
their shape makes them insoluble
290
how are fibrous proteins’ polypeptides arranged?
in parallel chains or sheets, with many cross-linkages forming long fibres
291
what is an example of a fibrous protein?
- collagen - providing the strength and toughness needed in tendons
292
what does the fibrous protein collagen provide?
the strength and toughness needed in tendons
293
what are globular proteins?
- are compact and folded into spherixal molecules
- this makes them soluble in water
- and so they have different functions, including enzymes, antibodues, plasma proteins and hormones
- e.g haemoglobin
294
are globular proteins soluble in water?
yes - they are compact and folded into spherical molecules which makes them soluble in water
(and so they have many different functions)
295
what are examples of the functions that globular proteins can be?
- enzymes
- antibodies
- plasma proteins
- hormones
296
what is an example of a globular protein?
- haemoglobin
- insulin
297
what does haemoglobin as a globular protein consist of?
- consisting of 4 folded polypeptide chains, at the centre of each of which is the iron-containing group, haem
298
what is the test for protein?
the biuret test
299
how do you carry out the biuret test for protein?
- add a few drops of biuret reagent (sodium hydroxide and copper (II) sulphate)
- pale blue -> purple if positive
300
how does the biuret test for proteins work?
- the sodium hydroxide and copper sulphate react to make blue copper hydroxide, which interacts with the peptide bonds present in the protejn to make biuret, which is purple
301
at a low protein concentration, can the colour change during the biuret test be seen clearly?
no - it’s difficult to detect by eye
302
the more concentrated the protein, the __ the purple colour (during the biuret test)
the darker the purple colour
303
is the biuret test qualitative or quantitative?
qualitative (the more concentrated the protein, the darker the purple colour) but could be used as a semi-quantitative test, comparing the intestity of purple in two identically treated solutions
304
what is the name for two amino acids?
many amino acids?
2 = dipeptide
many = polypeptide
305
in the secondary structure, what is the shape (either alpha-helix or beta-pleated sheet) determined by?
the type of bonding present such as hydrogen bonding, ionic bonding and disulphide bridges
306
what is the difference between globular and fibrous proteins?
- globular proteins such as enzymes are compact and have metabolic functions in the body
- fibrous proteins such as keratin are long and thus can be used to form fibres and have structural roles in the body
307
why is collagen a fibrous protein of great strength?
due to presence of both hydrogen and covalent bonds in the structure
(collagen molecules wrap around each other and form fibrils which form string collagen fibres)
308
what is collagen used for in the body?
- it forms the structure of bones, cartilage and connective tissue
- and is the main component of tendons which connects muscles to bones
309
what does haemoglobin do in the body?
it carries oxygen in the blood as oxygen can bind to the haem (Fe2+) group and oxygen is then released when required
310
apart from the amino acid, what else does changing the R group change?
the properties of the amino acid (which will also affect the properties of any protein)
311
how is the disulfide bridge bond formed?
the -SH group of one cysteine can form a covalent bond with the -SH group of another cysteine
312
how can amino acids polymerise to give dipeptides and polypeptides?
through a condensation reaction
313
what is the bond between two amino acids called?
the peptide bond
314
where do peptide bonds form?
between the carboxyl group of one amino acid and the amino group of another
315
how are hydrogen bonds formed in the secondary structure of proteins?
each chain of amino acids contain many polar groups:
- the amino group -N-H small+
- the carboxylic acid group -C=O small-
because opposite charges attract, the -N-H+ and -C=O - groups attract each other, forming hydrogen bonds
316
does the folding of the amino acid chain to form a new shape (secondary structure) involve the R group?
no
317
what kind of role do proteins with a secondary structure play in organisms?
important structural roles
e.g:
Alpha Helix
- alpha-keratin in wool
- collagen in skin and blood vessels
Beta Pleated Sheets
- fibroin in silk
318
does the tertiary structure of a protein or polypeptide depend on the R group?
yes - it depends on the properties of the R group
319
how are ionic bonds formed in the tertiary structure? how can it help?
- from charged variable groups
- can interact with water, which helps a protein to dissolve
320
how are covalent bonds formed in the tertiary structure?
- from variable groups containing sulfur atoms - two of these can bond together to form a disulfide bridge
- as they are covalent bonds, disulfide bridges are strong and more difficult to break - a higher temp or more extreme pH would be needed to break these bonds
321
how are hydrogen bonds formed in the tertiary structure?
- additional hydrogen bonds can also form between polar variable groups
322
when do hydrophobic interactions take place?
when the variable groups are non-polar
- they are repelled by water and are usually found on the inaide of the protein as far away from water as possible; a protein rich in non-polar side groups will be less soluble in water
323
a protein rich in non-polar side grouos will be __ soluble in water?
less
324
what are the metabolic functions of globular proteins (enzymes, antibodies + hormones) in organisms?
- enzymes = active sites to bind to a substrate
- antibodies = sites for binding to antigens
- hormones = sites for binding to specifix receptors
325
what is the order of strength of: peptide bonds (covalent), ionic bonds, hydrogen bonds, disulphide bonds (covalent) and hydrophobic interactions?
1. peptide bond (covalent)
2. disulphide bond (covalent)
3. ionic bond
4. hydrogen bond
5. hydrophobic interactions
326
what is the arrangement of several polypeptides called?
the quaternary structure of a protein
327
what are examples of proteins with a quaternary structure, that have disulfide bridges that bond the polypeptide chains together?
- insulin
- haemoglobin
- immunoglobuline
(these are all globular protejns which have a metabolic function in the body)
328
what roles do globular proteins have in the body? fibrous proteins?
globular - metabolic functions
fibrous - structural roles
329
explain how the structure of glycogen is related to its function
it’s multi branched which allows access for the rapid hydrolysis to release glucose -> good energy store
330
which ppt do reducing sugars form when heated with Benedict’s?
copper oxide
331
what is the arrangement of molecules in phospholipids?
how do these properties contribute to cell structure?
- the phosphate head is polar and the tail is non-polar so…
- it has a hydrophilic phosphate head and a hydrophobic tail. the tails face each other - allows formation of phospholipid bilayer in water
- it allows cells to form a plasma phospholipid around the cell (cell membrane)
332
why do some lipids form solids at room temperatures and some form oils?
lipids that are unsaturates have C=C double bonds. the more double bonds, the lower the melting temperature bc they compact more closely together
333
suggest three roles of lipids that are especially important for the survival of fast-moving seals in cold waters
- release 2x energy as a carbohydrate when oxidised = used to swim fast
- insoluble in water = seal is waterproof
- slow conductors of heat = maintain body temperature
334
what are the advantages of lipids?
- higher ratio of energy-storing carbon-hydrogen bonds to carbon atoms -> excellent source of energy
- low mass to energy ratio -> good storage molecules bc much energu can be stored in a small volume
- being large, non-polar molecules, triglycerides are insoluble in water. so their storage doesn’t affect osmosis in cells or the water potential of yhem
- as they have a high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised and therefore provide an important source of water
335
what do saturated phospholipids look like?
they have straight tails
336
what do unsaturated phospholipids look like?
kinked tails
337
what are the different functions of proteins?
- enzymes
- hormones
- antibodiea
- oxygen transporters
338
are proteins 3D?
yes
339
what are proteins?
huge 3D molecules whose building blocks or monomers are the variety of different amino acids found in nature
340
what are the two functional groups of proteins?
- carboxyl group (COOH)
- amine group (NH2)
341
does the R-group stay the same for every amino acid?
no - it differs for every amino acid
(is the variable group)
342
what is the name for two amino acids bonded together?
dipeptide
343
what is the name for many amino acids bonded together?
polypeptide
344
how is the quaternary structure of a protein formed?
it arises from a combination of 2+ polypeptide chains in tertiary form
(consist of more than one polypeptide chain)
345
what is meant by an unsaturated fatty acid?
- has double C=C bonds
- unsaturated fatty acids are not saturated with hydrogens
346
what is another name for proteins?
polypeptides
347
what do proteins form the bulk of?
- skin
- hair
- feathers
- nails
- cartilage
348
what do proteins contain?
carbon, hydrogen, oxygen and nitrogen
349
what are proteins built up from?
linear sequences of amino acids
350
what shape do individual amino acids display?
a tetrahedral shape due to the angles of the bonds between the atoms
351
is the amino acid that has a carboxylic acid group in the R group acidic, basic or neutral?
acidic
bc it has 2 acid groups and 1 basic group
352
what helps to stabilise the secondary structures?
hydrogen bonds
353
what does the amino acid chain coil into to make the alpha-helix structure?
a right-handed helix
(then hydrogen bonds form between oxugen and hydrogen atoms that havr been brought into close proximity)
354
what happens to the amino acid chain when making the beta-pleated sheet structure?
it folds back upon itself many times forming anti-parallel chains
(the oxygen and hydrogen atoms that have been brought into close proximitu form hydrogen bonds)
355
what bonds maintain the tertiaru structures?
- disulphide
- ionic
- hydrogen bonds
356
what are molecules that have a quatrtnary structure associated with?
non-proteins groups and form large, complex molecules
e.g haemoglobin
357
what does haemoglobin consist of?
- 4 polypeptide chains that are held together by weak Van der Waals forces
- each polypeptide chain (4) contains an iron containing Haem group that binds to molecules of oxygen
358
between what do hydrogen bonds form?
hydrogen and oxygen atoms (from both the main chain and the R group)
359
between what do disulphide bridges form?
the R group of two amino acids containing sulphur atoms
S-S
360
between what do ionic bonds form in proteins?
oppositely chatged groups
e.g many of the carboxylic acid and amino groups form charged groups in solution
361
where do hydrophobic interactions tend to be in protein molecules?
many hydrophobic R groups tend to cluster towards the interior of the protein molecule (forming hydrophobic interactions)
362
what is the test for protein? and what id the colour change?
- biuret test
- blue -> purple/violet indicates the presence of a protein
363
are globular proteins soluble or insoluble in water?
soluble
364
what shape are globular proteins?
- compact
- folded as spherical molecules
365
what are enzymes?
- proteins
- biologica catalysts
- they control cellular metabolism and catalyse the hydrolysis of food materials during digestion
366
what are examples of protein hormones that regulate blood glucose levels?
insulin and glucagon
367
what are examples of globular proteins?
- enzymes
- antibodies
- plasma proteins
- hormones
368
what does haemoglobin do?
(in mammalian red blood cells) transports oxygen to the tissues
369
what does myoglobin function as?
an oxygen store in muscles
(a globular protein)
370
are channel proteins involved in simplr diffusion, facilitated diffusion or active transport?
facilitated diffusion
371
are carrier proteins involved in simplr diffusion, facilitated diffusion or active transport?
facilitated diffusion and active transport
372
what do membrane transport proteins (channel and carrier proteins) do?
transfer substances across cell membranes
373
are fibrous proteins soluble or insoluble in water?
insoluble
374
what do fibrous proteins consist of?
polypeptides in parallel chains or sheets with cross linkages
375
are fibrous proteins strong or weak?
strong and tought
376
what functions do globular proteins have?
they perform a variety of function
377
what functions do fibrous proteins have?
- structural functions
378
what are examples of fibrous proteins?
collagen and keratin
379
what is collagen?
the structural protein of bone and connective tissue
380
what is alpha-keratin?
the structural protein of hair, horns and nails
381
what is the test for reducing sugars?
1. mix the test solution with an equal volume of Benedict’s reagent
2. heat the mixture in a water bath between 70.C and 90.C for 5 mins
382
what is the test for proteins?
1. mix the test solution with equal volume of Biurey reagent in a boiling tube
2. cover the top of the boiling tube and invert it once
383
what is the test for starch?
1. mix (2cm^3) the test solution with (2 drops) of iodine in potassium-iodine solution
384
what is the test for fats and oils?
1. mix the fat or oil with (5cm^3) of absolute alcohol in a boiling tube
2. shake the tube
3. pour the mixture into another boiling tube half full of cold water
385
what is the test for non-reducing sugars?
1. put (2cm^3) of the test solution in a boiling tube, add (2 drops) of hydrochloric acid, and heat in a water bath to 70.C and 90.C for 2 minutes
2. add 2 drops or sodium hydroxide
3. add 2cm^3 of Benedict’s reagent
4. heat the mixture in a water bath to between 70.C and 90.C for 5 minutes
386
what type of bonds are formed between two monomers in a condensation reaction?
covalent bonds
387
which (carbohydrate) structure is the most highly branched structure?
glycogen
388
what type of bond holds together the B-glucose chains that make up cellulose?
hydrogen bonds
389
is cellulose branched?
no
390
is glycogen short or long? branched or unbranched?
glycogen is short, highly branched chains
391
is cellulose long or short? straight or coiled? branched or unbranched?
cellulose is long, straight, unbranched chains
392
is amylopectin long or short? branched or unbranched?
long, branched chains
393
which (carbohydrate) molecule forms fibres?
cellulose
394
why is sucrose known as a non-reducing sugar?
it does not reduce copper sulfate
395
what do you need to do to non-reducing sugars such as sucrose before testing with Benedict’s reagent?
hydrolyse it into its constituent monosaccharides
396
what is the order of colour in the Benedict’s test?
blue -> green -> orange -> brick red
397
what do reducing sugars donate to Benedict’s reagent?
electrons
398
at what temperature is the test for starch carried out at?
room temperature
399
to test for reducing sugars, non-reducing sugars, starch and protein, what must happen to the food sample first?
be ground up in water
400
what are the names of the functional groups at the end of the chain in fatty acids?
- carboxyl group (-COOH)
( - methyl group (-CH3))
401
what ions present in the Biuret test reagent bind to nitrogens present in peptide bonds of protein?
copper (II) ions
402
where are inorganic ions found?
in the cytoplasm
403
what is another test to compare glucose and starch that is quicker and requires no scientific knowledge?
reagent strips + compare on a colour chart
404
what builds up if our diet is too high in saturated fats?
what fatty materil does it cause?
low-density lipoproteins
causing fatty material, called atheroma
405
where is atheroma deposited in?
the coronary arteries
406
what is the disease where atheroma builds up in the coronary arteries, impeding blood flow and restricts oxygen flow to the heart muscle?
atherosclerosis
407
what does the body produce if our diet contains more unsaturated fats?
what do they do?
the body produces more high-density lipoproteins
which carry harmful fats to the liver for processing
408
state two ways the quaternary structure of a protein is diffferent from the tertiary structure
- it includes other polypeptide chains/more than one polypeptide chain present
- and may contain prostetic groups
409
why is it recommended that humans eat a higher proportioj of lipids containing double-bonds (unsaturated)?
- unsaturated fats decrease level of low-density lipoproteins/cholesterol OR unsaturated fats increase level of high-density lipoproteins
- this reduces risk of heart disease/atherosclerosis/atheroma formation
410
are triglycerides polymers?
no
411
what is atherosclerosis?
- the buildup of fatty deposits or plaques called atheromas within artery walls
- as a result of low-density lipoproteins (LDL) from a diet high in saturated fats
- which leads to the narrowing of the arteries
412
how does atherosclerosis eventually cause a heart attack?
- atherosclerosis is the build up of athromas within the artery walls
- this leads to the narrowing of the arteries
- as they narrow, they lose their elasticity and begin to restrict blood flow, which limits oxygen delivery to the heart
- which can result in angina, and eventually a heart attack
413
how does atherosclerosis eventually cause strokes?
- atherosclerosis is the build up of atheromas
- atheromas can cause the endothelial lining to rupture, which causes a clot to form (thrombosis), which can also cause strokes
414
a diet with a higher proportion of unsaturated fats result in what?
the body manufacturing more high-density lipoproteins which carry harmful fats to the liver for disposal
(unsaturated fats + exercise)
415
the higher the ratio of HDL:LDL in a patient’s blood, the (higher/lower) the risk of cardiovascular disease?
lower
416
what happens to the arteries as they narrow?
they lose their elasticity and begin to restrict blood flow, which limits oxygen delivery to the heart, which can result in angina and eventually a heart attack
417
polymers are complex molecules that are formed by combining monomers using ___ bonds?
covalent
418
where is starch primarily stored in plants?
seeds
419
why must polymers in food be hydrolysed in the body?
monomers are easier to transport than polymers
420
why is the high surface tension of water important for organisms?
- enables the transport of water and nutrients through plant stems and small blood vessels in the body
- allows small insects to ‘walk’ on water
421
describe the structure and function of cellulose
- linear polysaccharide that is the main component of the cell wall in plants
- consists of many B-glucose molecules joined by B-1,4-glycosidic bonds
- alternate glucose molecules rotated 180° allowing hydrogen bonds between parallel chains, forming microfibrils
422
describe the structure and function of chitin
- linear polysaccharide found in the exoskeleton of insects and crustaceans as well as fungal cell walls
- consists of many B-glucose molecules (with amino acid side chains) joined by B-1,4-glycosidic bonds
- alternate glucose molecules rotate 180° allowing hydrogen bonds between parallel chains, forming microfibrils
423
relate the structure of triglycerides to their function
- high energy-to-mass ratio - energy storage
- insoluble hydrocarbon chain - no effect on water potential of cells, used for waterproofing
- slow conductor of heat - thermal insulation
- less dense than water - buoyancy of aquatic animals
424
what is meant by a low density lipoprotein (LDL)?
- combination of triglycerides from saturated fats and protein
- blocks receptor sites, reducing cholesterol absorption
- known as ‘bad’ lipoproteins
425
how do LDLs contribute to the risk of cardiovascular disease?
the high blood cholesterol level caused by LDLs lead to formation of atherosclerosis plaques
426
describe how the structure of fibrous proteins relates to their function
- long polypeptide chains, folded in parallel
- little tertiary/quaternary structure aside from cross-linkages for strength
- this makes them insoluble and good for structural roles
427
describe how the structure of globular proteins relates to their function
- spherical, compact, highly folded with complex tertiary/quaternary structures
- hydrophilic R groups face outwards and hydrophobic R groups face inwards ∴ water-soluble
- metabolic roles e.g enzyme
428
explain the importance of the (-S-S-) linkages in a protein to the functioning of the enzyme:
- links between different parts of polypeptide chains
- produces a specific shape for the molecule
- reference to active site
- complementary to substrate
- allows enzyme-substrate complexes to form
429
explain why triglycerides are not considered polymers?
glycerol and fatty acids have different structures
430
describe the structure of a collagen molecule. [3]
state one function of collagen. [1]
- polypeptide chains (not proteins)
- three chains (not strands)
- (three) alpha helices
- tightly/closely bound
- held together by hydrogen bonds
- structural/relevant example e.g tendons or named tissue strengthened
431
explain what is meant by the term hydrolysed [2]
- breaking a bond (not molecule broken down)
- insertion of a molecule of water / chemical addition of water (not adding water)
432
describe two functions of lipids in plants [2]
- energy storage/respiratory substrate/source of energy
- waxy cuticle/leaf waterproofing
- membrane structure
