3- Biological Molecules Flashcards
(153 cards)
1
Q
How many bonds can carbon atoms form?
A
4
2
Q
How many bonds can nitrogen atoms form?
A
3
3
Q
How many bonds can oxygen atoms form?
A
2
4
Q
how many bonds can hydrogen atoms form?
A
1
5
Q
What is the chemical formula of methane?
A
CH4
6
Q
What is the chemical formula of ammonia?
A
NH3
7
Q
what 4 key elements are all living things primarily made from?
A
Oxygen
Hydrogen
Carbon
Nitrogen
8
Q
what are the two elements also have important roles in the biochemistry of cells?
A
phosphorus
sulphur
9
Q
What happens in ionic bonds?
A
One atom in the pair donates an electron and the other receives it. This forms positive and negative ions that are held together by the attraction of opposite charges
10
Q
what are ions in solution called?
A
Electrolytes
11
Q
what are the five cations (+ve ions) that play important roles in organisms
A
Calcium ions - nerve impulse transmission and muscle contraction
Sodium ions -nerve impulse transmission and kidney function
Potassium, ions – nerve impulse, transmission and stomatal opening
Hydrogen ions – catalystis of reactions and pH determination
Ammonium ions (NH4+) - production of nitrate ions
12
Q
what are the five anions (-ve ions) that play important roles in organisms?
A
Nitrate ions (NO3-) - nitrogen supply the plants for amino acid and protein formation
Hydrogen carbonate ions (HC03-) -maintenance of blood pH
chloride ions (Cl-) - balance positive charge of sodium and potassium ions in cells
Phosphate ions (PO4 3-) - cell membrane formation, nucleic, acid and ATP formation, bone formation
Hydroxide ions (OH-) - catalysis of reactions, pH determination
13
Q
what is a molecule the gains electrons called
A
negative charge = anion
14
Q
what is a molecule that loses electrons called
A
positive charge = cation
15
Q
what elements are present in carbohydrates?
A
Carbon
Hydrogen
Oxygen
16
Q
What elements are present in lipids?
A
carbon
Hydrogen
Oxygen
17
Q
what elements are present in proteins?
A
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
18
Q
what elements are present in nucleic acids
A
carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
19
Q
What are polymers?
A
long-chain molecules made up by the linking of multiple individual molecules called monomers in a repeating pattern
20
Q
what is meant by the term polar in relation to molecules?
A
-Molecules that have regions of negativity and regions of positivity
-This is due to the way in which electrons are distributed between elements joined by a covalent bond
-The electrons spend more time closer to one of the atoms then another
21
Q
How do polar molecules like water interact with eachother?
A
-the positive and negative regions attract each other to form bonds called hydrogen bonds
-these bonds, give water its cohesive properties - it moves as one body because the molecules are attracted to each other
-these bonds also give water its adhesive properties - it’s molecules are attracted to other surfaces
22
Q
How does hydrogen bonding occur between water molecules?
A
-water = H20
-covalent bond between oxygen and hydrogen atoms
-unequal sharing of electrons
-oxygen has a greater share of electrons in O-H bond
-oxygen is slightly negative, hydrogen is slightly positive
23
Q
Hydrogen bonds are….
A
-Relatively weak interactions which break and reform between constantly moving water molecules
-Occur in high numbers which give water its unique characteristic that are essential for life on Earth
24
Q
What are the unique characteristics of water that are essential for life on Earth?
A
-unusually high specific heat capacity (boiling point)
-becomes less dense when it freezes
-cohesive properties
-adhesive properties
-‘skin’ of surface tension
-capillary action
25
What makes it more difficult for water to become a gas?
hydrogen bonding between molecules
26
Water has a low viscosity. What does this mean?
It flows easily
27
Why is it good that water has a high specific heat capacity?
-keeps habitats stable for living things add a lot of energy is required to change it by 1°C
28
explain how the ‘skin’ of surface tension of water enables a pond skater to inhibit the surface?
The skin is because water molecule are more strongly cohesive to each other than air, the skin supports the pond skater
29
due to water being a liquid at room temperature what four things does this allow it to do?
-provide a habitat for living things
-form major component of tissues in living organisms
-provide a reaction medium for chemical reactions
-provide efficient, transport medium
30
Why is it good that ice is less dense than water?
-aquatic animals have a stable environment in which to live throughout winter
-ponds and other bodies of water are insulated against extreme cold
31
because water is a good solvent what two things?
-Acts as a medium for chemical reactions
-Help transport dissolved compounds in and out of a cell
32
how does water dissolve solutes?
-The negative part of water molecules attach to the positive parts of the solutes
-The positive part of water molecules attach to the negative parts of solutes
-this keeps them away from each other eventually dissolving the solute in a solution
33
why when water freezes does it turn into ice?
-it becomes less dense than ice due to hydrogen bonds being formed
-Water is cooled at 4°C because the hydrogen bonds fix the positions of the polar molecules slightly apart from the average distance in liquid state
-This produces a giant, rigid but open structure, with each oxygen atom, at the centre of a tetrahedral arrangement of hydrogen atoms
-Resulting in a solid that is less dense than liquid
-Due to this, ice floats
34
how is water an efficient transport medium?
-cohesive properties between water molecules, when water transported through body, molecules will stick together
-adhesive properties between other molecules (polar)
-effects of adhesion and cohesion result in water exhibiting capillary action
-This is a process by which water can rise up a narrow tube against gravity
35
why is water being a coolant efficient for life?
-Helps to buffer temperature changes during chemical reactions in prokaryotic and eukaryotic cells due to it, taking a large amount of energy to overcome hydrogen bonding
-Important in cellular environments, as enzymes are often only active in narrow temperature ranges
36
what does a condensation reaction?
-Joins two monomers together
-Formation of a covalent bond
-Involves elimination of a water molecule
37
What is a hydrolysis reaction?
-Opposite of a condensation reaction
-Breaks the covalent bond between two monomers
-Water is added to break the chemical bond, involves use of a water molecule 
38
what covalent bond is created by the joining of carbohydrates, proteins and nucleic acids?
Carbohydrates- glycosidic
Proteins- peptide
Nucleic acids- phosphodiester
39
which enzymes need chlorine and zinc to function correctly?
chlorine- amylase
zinc- carbonic anhydrase
40
what is a single sugar known as?
Monosaccharide
41
what are the monosaccharides of carbohydrates?
Glucose
Fructose
Galactose
42
what are monosaccharides?
-Individual sugar molecules that make up disaccharides and polysaccharides
-Glucose, fructose and galactose
43
What are the two types of sugar molecules?
hexose sugars - 6 carbon atoms
Pentose sugars - 5 carbon atoms
44
What is the structure of glucose?
-hexose sugar
-Can form isomers: a-glucose (alpha) and b-glucose (beta)
-C6H12O6
-Carbon ring structure
45
What is a disaccharide?
-formed through condensation reaction
-Two monosaccharides joined together
-Form a glycosidic bond between the two OH groups
46
what are three examples of disaccharides? What monosaccharides are used to form then?
Maltose - glucose + glucose (reducing)
Lactose - glucose + galactose (reducing)
Sucrose - glucose + fructose (non-reducing)
47
what is a polysaccharide?
-Formed when more than two monosaccharides are joined together by condensation reaction
-Can be broken down by hydrolysis into their monomers
-Glycosidic bonds formed
-examples: startch (amylose and amylopectin) , glycogen, cellulose
48
What are the properties and structure of startch?
-made from monosaccharide a-glucose
-Mixture of two polysaccharides: amylose and amylopectin
AMYLOSE
-unbranded chain
-joined by 1,4 gylcosidic bonds
- meaning it is coiled
-coiled = compact, more stored in smaller space, lots of energy stored
AMYLOPECTIN
-long branched chain
-1,6 and 1,4 glycosidic bonds
-branches increase surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released quickly
-insoluble
-Strach is insoluble - does not affect cells water potential
-Compact so lots of energy is stored in one place
-Can be hydrolysed to release glucose for respiration
-Easily digestible
49
how does a-glucose differ from b-glucose?
-The hydroxyl groups (OH) on carbon one are in opposite positions (flipped)
-This effects the structure and properties of the polysaccharides when it bonds
50
Which two pentose sugars are important components of biological molecules?
Ribose (in RNA)
Deoxyribose (in DNA)
51
What are the properties and structure of glycogen?
-long branches chains of a-glucose
-lots of side branches
-Joined by 1-4 glycosidic bonds (chains) and 1-6 glycosidic bonds (branches)
-Lots of branches increase surface area for enzymes to hydrolyse bonds and release glucose quickly (during respiration)
-compact and insoluble so good for storage
52
What are the properties and structure of cellulose?
-made of beta glucose
-long unbranded straight chains
-contains 1-4 glycosidic bonds
-Beta glucose molecules bond forming straight cellulose chains
-Every other glucose molecule is orientated 180°
-Chains are linked by hydrogen bonds forming strong fibres called microfibrils (compact)
-Microfibrils are very strong but still flexible allowing them to provide support
53
What is the function of glycogen?
-main energy store in animals
-stores soluble glucose that affects water potential as insoluble polysaccharide until needed
54
What is the function of cellulose?
-Cellulose is an important part of our diet as it is very hard to break down so if the fibre necessary for a healthy digestive system
-Cellulose provides structural support for cells
55
How is a disaccharide broken down?
-hydrolysis reaction
-addition of water to hydrolyse the disaccharide into monomers
-reactions are catalysed by enzymes
56
How can you tell if a molecule is a reducing sugar?
-free OH group at the anomeric carbon
57
What is the anomeric carbon?
Find a carbon which is bonded directly to 2 different oxygen atoms
58
What is a reducing sugar?
-can donate electrons
-reduce another molecule or chemical
59
Which of the disaccharides are reducing and non-reducing sugars?
Maltose - reducing
Lactose - reducing
Sucrose - non-reducing
60
What is the test for identification of reducing sugars?
-Benedict’s test
1. add 2cm^3 of the same into a boiling tube. (if non liquid, grind it up or blend it in water)
2. add 2cm^ of Benedict’s reagent
3. heat the mixture gently in a boiling water bath for five minutes
4. Record observations
positive result = brick red
61
What is the test for non-reducing sugars?
1. Add 2cm^3 of the same into a boiling tube
2. Add 2cm^3 of dilute hydrochloride acid
3. Place the boiling tube in a water bath for 5 minutes. (the dilute HCl will hydroluse the sample into their constituent monosaccharides)
4. Neutralise the acid by adding sodium hydrocarbonate until no effervescence is observed (could also use pH paper)
5. Now add 2cm^3 of benedict’s reagent to the sample
6. Place in a water bath for 5 minutes
7. Record your observations
positive result = change from blue to brick red
62
What is the test for starch?
Iodine test
1. Add a few drops of iodine
positive result = from yellow/brown to purple/back
63
What is benedict’s reagent?
An alkaline solution of Copper (II) Sulfate
64
What colour would blue Benedict’s Reagant change is reducing sugars are present?
Brick Red
65
Why does Benedict’s Reagant turn red when reducing sugars are present?
Because the blue Cu2+ ions have an electron is added to form brick red Cu+ ions
66
What percentage of starch is amylopectin and what percentage is amylose?
70-80% amylopectin
20-30% amylose
67
How can you make the Benedict’s test quantative?
Use a colorimeter to test the transmission of red light in the soloutions
more reducing sugars = more red light
68
What are 2 examples of biosensors?
Pregnancy test, blood sugar monitor
69
What is an analyte in a biosensor?
the sample containing the molecule you are testing for
70
What is the receptor in a biosensor?
The part which interacts with the molecule you are testing for
71
What is the transducer in a biosensor?
Detects the change in the receptor and provides a response
72
What does the display do in a biosensor?
Gives a visual representation of the change in the receptor
73
What are biosensors?
use biological components to determine the presents and concentration of molecules (such as glucose)
74
What are the two types of lipids?
Phospholipids
Triglycerides
75
Are phospholipids polar?
Partially
-they have a polar head (phosphate group)
-non-polar tail (fatty acids)
76
What is the difference between fats and oils?
-oils are liquids at room temperature, fats are solid
77
What is the structure of a triglyceride?
-a glycerol molecule and 3 fatty acids (hydrocarbon chains with a carboxyl group)
-joined by ester bonds (between 3 OH groups and glycerol)
78
Where are triglycerides found in the body?
-bloodstream
-adipose tissue
79
Why are triglycerides insoluble in water?
Because of their non polar tails
80
What is the structure of a phospholipid?
-a glycerol molecule, a phosphate group and 2 carry acid chains
-ester bond between 2 OH groups on the glycerol and OH groups of each fatty acid chain
-bilayer arrangement
81
What is the main use of triglycerides and why?
Energy storage because their hydrocarbon tails contain lots of energy released when the fatty acid chains are broken down
82
What is the tests for lipids in food?
Emulsion test
83
What result indicates the presence of lipids when using the emulsion test?
A milky emulsion forming
84
How would you conduct a test for lipids?
1. Add 2cm^3 of ethanol to the sample
2. Add 2cm^3 of water and shake gently
3. observe the appearance of the test tube contents
85
What are the hazards associated with the emulsion test?
-ethanol is flammable - do not conduct near naked flame
86
Why can ethanol form emulsions
it is not polar
87
Why do unsaturated fats tend to be liquid rather then solid at room temperature?
Because the double bonds cause a kick in the hydrocarbon chain so the molecules can’t pack closely together
88
What type of alcohol is cholesterol?
A sterol alcohol
89
Where is cholesterol made?
Mostly livers and intestine
90
What are saturated fatty acids?
-don’t have double bonds between carbon atoms
-has all of its hydrogens
91
What are unsaturated fatty acids?
-double bonds between carbon atoms
-fewer hydrogens
-causes a kink/bend
- can contain one (mono) or many (poly) carbon double bonds
92
What is the bilayer arrangement like in phospholipids?
-phospholipid heads = hydrophilic
-tails = hydrophobic
-when placed in water form a double layer with heads facing outwards towards the water and tails facing inwards
-centre of bilayer is hydrophobic, water soluble substances cannot easily pass through, creates a barrier + allows separation of solutions and create different conditions either side of membrane
93
What is meant by hydrophobic?
Section of molecule which is repulsed by water
94
What is meant by hydrophilic?
Section of molecule which is attracted to water
95
What are sterols?
-type of lipid found in cells
-complex alcohol molecules based on a four carbon ring structure with a hydroxyl (OH) group at one end
-dual hydrophilic/hydrophobic characteristics like phospholipids
eg. cholesterol
96
What is cholesterol and its function in the body?
-primarily manufactures in liver + intestines
-important role in formation of cell membranes, adds stability to cell
-regulates cell fluidity by keeping low temperatures and stopping them becoming too fluid at high temps
-hormones (eg. testosterone, oestrogen, vitamin D) made from cholesterol. Because they are small and hydrophobic they can pass through hydrophobic part of cell membrane
97
What are the roles of lipids?
-membrane formation and the farted on of hydrophobic barrie’s
-hormone production
-electrical insulation necessary for impulse transmission
-waterproofing
-energy storage
98
what are the chemical properties of water?
-hydrogen bonding, polar molecule
-good solvent
99
What are the monomeric units (monomers) of proteins?
Amino Acids
100
How many common amino acids are there?
20
101
Give 4 functions of proteins?
-enzymes
-hormones
-antibodies
-structural proteins
102
What do the interactions of differing R-groups determine?
The types of bond, leading to the folding of the protein
103
What type of reaction occurs when 2 amino acids join?
-condensation reaction
-peptide bond forms (between amine group of one and hydroxyl group of another)
-water molecule released and a dipeptide formed
104
What is the general formula of an amino acid?
-R group (at top)
-Carbon in the middle
-Hydrogen at the bottom
-Amine group (H2N) on left
-Carboxyl group (COOH) on right
105
What is a chain of amino acids called?
A polypeptide
106
What is the end of a polypeptide with an amino group called?
The N-terminus
107
What is the end of a polypeptide with an carboxyl group called
The C-terminus
108
What is the definition of primary structure of a protein?
-the sequence of amino acids in the polypeptide chain
-this contains the initial sequence of amino acids which will influence how the polypeptide folds to give its final shape. This is turn determines its function
109
What type of bonding holds the primary structure of a protein together?
Peptide
110
What shape is the primary structure of a protein?
Linear
111
What forms the secondary structure of a protein?
-the folding of the primary structure
112
What type of bonds hold together the secondary structure of a protein?
Hydrogen
113
In the secondary structure what do hydrogen bonds form between?
Partially positive H and partially negative O
114
What are the two possible shapes of the secondary structure?
-alpha helix
-beta pleated sheets
(caused by the hydrogen bonds pulling it into a shape)
115
What is the tertiary structure of a protein?
-interactions of R groups (which are closer together due to folding in the secondary structure) causing further folding
116
What are the 4 types of bond formed at the tertiary structure level?
-ionic bonds
-hydrogen bonds
-disulfide bonds
-hydrophobic and hydrophilic reactions
117
What do ionic bonds form between in the tertiary structure of a protein?
positively and negatively charged ions (oppositely charged R groups)
118
What do hydrogen bonds form between in the tertiary structure of a protein?
Partially positive H and partially negative O (weakest bond)
119
What do disulfide bridges form between in the tertiary structure of a protein?
Sulfur atoms contained within some R-groups
120
Which amino acid contain sulfur?
Cysteine
121
What do hydrophobic and hydrophilic interactions form between in the tertiary structure of a protein?
polar and non-polar R groups
122
What kind of shape does the tertiary structure have?
3D
123
What forms the quaternary structure?
Formed by the interaction of more than one tertiary protein and/or with prosthetic groups
124
What type of bonds holds a quaternary structure together?
-ionic
-hydrogen bonds
-disulfide bridges
-hydrophobic and hydrophilic interactions
125
What is a prosthetic group?
A non-protein component of a conjugated protein
126
What is an example of a quaternary protein?
-haemoglobin
-Antibodies
127
define simple proteins
Proteins without a prosthetic group
128
What are three characteristics of globular proteins?
-Compact
-Water soluble
-Roughly spherical shape
129
why are globin proteins water soluble?
-tertiary structures are folded so that the hydrophobic R-groups are kept away from aqueous environment
-hydrophilic R-groups are on the outside
130
What are globular proteins used for?
-regulating many processes
131
What is an example of a globular protein?
Insulin
132
what is insulin? why is it beneficial for insulin to be water soluble?
-globular protein
-hormone involved in the regulation of blood glucose concentration
-hormones are transported in the blood stream so must be water soluble
133
what is the structure of insulin?
-2 polypeptide chains held together by hydrogen bonds and disulphide bridges
-no beta pleated sheets
-compact
-tertiary structure held together by 3 S-S bonds
-hydrophobic core, hydrophilic exterior
134
Are conjugated proteins a type of globular protein?
Yes
135
What are conjugated proteins?
globular proteins that contains a non-protein component called a prosthetic group
136
Give an example of 2 conjugated proteins?
-haemoglobin
-catalase
137
What is the function of haemoglobin?
carries oxygen in the blood in erythrocytes
138
What is the structure of haemoglobin?
-made of 4 polypeptide chains (2 alpha-helixes and 2 beta-pleated sheets)
-4 subunits which each contain a prosthetic haem group
-each haem group contains Fe 2+ ion
-iron ions in haem groups can reversibly combine with a molecule of oxygen
139
What is catalase? Its structure and function?
-an enyme
-quaternary protein containing 4 haem prosthetic groups
-Fe2+ ions are present which allow catalase to interact with hydrogen peroxide (by product of metabolism which is damaging to cell components if allowed to accumulate) and speed up its breakdown
140
What are fibrous proteins?
-long, insoluble, structural proteins
-due to the presence of a high proportion of amino acids with hydrophobic R-groups in their primary structure
-amino acids sequence in primary structure is usually quite repetitive leading to an organised structure, makes strong molecules that do not fold in complex 3D shapes
141
What type of protein is catalase?
conjugated (globular)
142
What are examples of fibrous proteins?
-collagen
-elastin
-keratin
143
Where is keratin found?
in hair, skin, nails
144
what amino acid does keratin contain in a high proportion?
cysteine - which contains sulfur
145
What type of bonding occurs a lot in keratin?
disulfide bonds/bridges
146
How does the high proportion of disulfide affect the properties of keratin?
it makes it inflexible and strong
147
How does the degree of disulfide change in different places where keratin is found?
hair = fewer bonds making it less flexible then nails which contain more bonds
148
Where is elastin found?
in the walls of blood vessels and alveoli in the lungs
149
What do elastin tissue do?
allow structures the flexibility to expand and return to size when needed
150
What makes up elastin?
aggregates of tropoelastin (stretchy molecules)
151
Where is collagen found?
in the skin, tendons, ligaments and nervous system
152
What is the basic structure of collagen like?
-3 polypeptides wound together in a long and strong rope-like structure
-has flexibility
-glycine for every 3rd amino acid as it is the smallest amino acid so allows collagen to pack together more tightly
153
What property does collagen have?
flexibility
