1 - Biological Molecules Flashcards
1
Q
What are biological molecules
A
Groups of chemicals found within living organisms
2
Q
Where do essential biological molecules come from to build our own cells
A
Our diet
3
Q
What are the 4 main types of organic biomolecules
A
Carbohydrates
Proteins
Lipids
Nuclei acid l
4
Q
How many bonds do carbon atoms form
A
4
5
Q
What atoms are present in carbohydrates
A
Carbon
Hydrogen
Oxygen
6
Q
What atoms are present in lipids
A
Carbon
Hydrogen
Oxygen
7
Q
What atoms are present in proteins
A
Carbon
Hydrogen
Oxygen
Nitrogen
Sulphur (sometimes)
8
Q
What atoms are present in phospholipids
A
Carbon
Hydrogen
Oxygen
Phosphorus
9
Q
What are macromolecules
A
Large
10
Q
What is the name for the individual building blocks within a larger macromolecule
A
Monomers
11
Q
What is the name for the longer chain-like molecule made up of the smaller units
A
Polymers
12
Q
What process joins monomers into bigger chains
A
Condensation
13
Q
What is the monomer unit in DNA
A
Nucleotides
14
Q
What are the monomer units in carbohydrates
A
Monosaccharide
15
Q
What are the monomer units in protein
A
Amino acids
16
Q
Why are lipids not described as a polymer
A
Lipids are made of one glycerol and 3 fatty acids, not repeating monomers
17
Q
What 3 groups can carbohydrates be divided into
A
Monosaccharides
Disaccharides
Polysaccharides
18
Q
Examples of monosaccharides
A
Glucose
Fructose
Galactose
19
Q
Examples of disaccharides
A
Sucrose
Maltose
Lactose
20
Q
Examples of polysaccharides
A
Starch
Cellulose
Glycogen
21
Q
Are monosaccharides soluble
A
Yes
22
Q
What is the general formula for monosaccharides
A
(CH2O)n
23
Q
How many carbons can be in a monosaccharide
A
3-7
24
Q
Name of a 3 carbon monosaccharide
A
Triose
25
Name of a 4 carbon monosaccharide
Tetrose
26
Name of a 5 carbon monosaccharide
Pentose
27
Name of a 6 carbon monosaccharide
Hexose
28
What is the molecular formula of glucose
C6H12O6
29
Is glucose a monosaccharide, disaccharide or polysaccharide
Monosaccharide
30
What is the bond between 2 glucose units called
(Alpha 1,4) glycosidic bond
31
What type of reaction involved the loss of water during the formation of a bond
Condensation reaction
32
Word equation of the formation of maltose
Glucose + glucose = maltose + water
33
Symbol equation for the formation of maltose
C6H12O6 + C6H12O6 = C12H22O11 + H2O
34
What monosaccharides do you need to make maltose
Glucose + glucose
35
What monosaccharides do you need to make sucrose
Glucose + fructose
36
What monosaccharides do you need to make lactose
Galactose + glucose
37
Fructose formula
C12H22O11
38
How many water molecules are relaxed when 47 monosaccharides joined together and what is the general rule
46
(Always one less than the number being joined together)
39
Definition of hydrolysis
A larger molecule is broken down into smaller molecules (bond broken) using water
40
Definition of condensation
Smaller molecules join together to make bigger molecules, a new bond is formed and water is released
41
T or f
All monosaccharides and some disaccharides are said to be reducing sugars
T
42
What is ment by reducing sugar
They are able to donate eLectrons to another substance, thereby reducing the substance
43
How can we test for the presence of reducing sugars
Benedict’s reagent
44
What is Benedict’s reagent
Alkaline solution of copper (ll) sulfate
45
What is forms when a reducing sugar is heated with Benedict’s reagent
Insoluble red precipitate of copper (l) oxide
46
Describe the Benedict test
Add an equal volume of Benedict’s reagent to the liquid ample being tested and heat in a gently boiling water bath for 5 minuets. If a reducing sugar is present, a brink red precipitation will from
47
What is the difference between a qualitative and a quantitative test
Qualitative shows if something is present
Quantitative shows how much
48
How can u tell the conc of reducing sugar present in the Benedict’s test
It’s colour
None - blue
Very low - green
Low - yellow
Medium - orange
High - red
49
Explain why the Benedict’s test is said to be semi- quantitative
It shows something is present but doesn’t give an exact numerical value - yet it shows roughly how much (you can distinguish between low / medium / high)
50
What are the 2 types of glucose
Alpha
Beta
51
What is beta glucose known as
An isomer
52
Non reducing sugar test
1) add 2cm3 of the sample being tested to 2cm3 of Benedict’s reagent in a test tube and heat in a gently boiling water bath for 5 mins
2)if Benedict’s reagent does not change colour form blue then a reducing sugar is not present
3) take a clean test tube and add another 2cm3 of the sample being tested from to 2cm3 of dilute hcl acidn
4) boil for 5 mins in a gently boiling water bath
5) neutralise by adding repeated spatulas of sodium hydrogen carbonate (check with PH paper)
6) now preform the Benedict’s test again: add 2cm3 of Benedict’s reagent to your resulting solution and heat for 5mmins in a gently boiling water bath
7) is a non-reducing sugar was present in the original sample, an orange/red precipitate Will form
53
Why is the sample boiled with hcl acid in the non reducing sugar testing practical
To break any (to hydrolyse) any glycosidic bonds
54
Why is the acidic solution neutralised using sodium hydrogen carbonate in the non-reducing sugar practical
Benedict’s test won’t work in acidic conditions
55
Describe a test for starch
Add iodine solution dissolved in potassium iodide solution to your sample - if Starch is present it will change form an orange to blue/black
56
Suggest a simple test that could be used to distinguish between a monosaccharide and a polysaccharide
Add monosaccharide + polysaccharide to separate test tubes and add water . Monosaccharides are soluble so will dissolve but polysaccharides are insoluble so won’t dissolve
57
Polysaccharides are polymers - from which monomers are they formed
Monosaccharides
58
What type of reaction is involved when monosaccharides units are joined togetehr
Condensation
59
What are the 3 main polysaccharides
Starch
Cellulose
Glycogen
60
What type of cell contains starch and if what form is it present
Plant cell
Starch grains
61
Is Starch a polymer of a or b glucose
a
62
Starch use in plants
For short term storage overnight when photosynthesis cannot occur
And in long term storage such a over winter
63
Where can large amounts of starch be found in plant s
Seeds and storage organs such as bulbs and potato tubers
64
What does starch from an important component fro
Diet and is the major energy source in most diets
65
Amylose or amylopectin?
A polymer of glucose
Both
66
Amylose or amylopectin?
Single unbranched chain
Amylose
67
Amylose or amylopectin?
Has side branches
Amylopectin
68
Amylose or amylopectin?
1,4 and 1,6 glycosidic bonds
Amylosepectin
69
Amylose or amylopectin?
Tightly compacted molecule
Amylose
70
Amylose or amylopectin
Only 1,4 glycosidic bonds
Amylose
71
Amylose or amylopectin?
Chain coiled into spirals, led by hydrogen bonds
Amylose
72
Example of monomers
Monosaccharides
Amino acids
Nucleotides
73
Example of monosaccharides
Glucose
Fructose
galactose
74
What is an isomer
Molecules with the same molecular formula as each other but with the atoms connected a differnt way
75
What reaction breaks down polyMyers into monomers
Hydrolysis
76
What 2 things can sugar be classified as
Reducing
Non-reducing
77
What is the general term for monosaccharides and disaccharides
Sugar
78
What is a more accurate way to compare the amount of reducing sugars in differnt solutions rather than observing colour change
Filter and way the precipitate
79
What do plants do when they needs more glucose for energy
Is breaks down starch to release glucose
80
What is starch a mixture of
2 polysaccharides of alpha glucose
Amylose and amylopectin
81
Describe amylose
A long, unbranches chain of alpha glucose, the angles of glycosidic bonds give it a coiled structure almost like a cylinder. This makes it more compact, so it’s really good for storage because you can fit more into a small space
82
Describe amylopectin
A long, branched chain of alpha glucose. It’s side branches allow enzymes that break from the molecule to get at the glycosidic bonds easily. This means that glucose can be released quickly.
83
Why do plants store glucose as starch
Starch is insoluble in water and doesn’t effect the water potential so it doesn’t cause water to enter cells by osmosis, which would make then swell.. this makes them good for storage
84
How do animals store excess glucose
As glycogen
85
What is glycogen similar to in structure
Amylopectin
Except it has loads more side branches
It is also very compact - so good for storage
86
What is cellulose made of
Long, unbranched chains of beta-glucose
87
What is formed when beta-glucose molecules bond together
Straight cellulose chains
88
What bond links cellulose chains
Hydrogen bond
89
The cellulose chains are liked together by hydrogen bonds to form ?
Strong fibres called microfibrils .
The strong fibres mean cellulose provides structural support for the cell
90
Why is starch well suited for it role in energy storage? - 5 reasons
- insoluble + therefore doesn’t affect water potential so water is not drawn into cells by osmosis
- large+ insoluble - it doesn’t diffuse out of cells
- compact - lots can be stored in a small space
- when hydrolysed it forms alpha glucose - both easily transported + readily used in respiration
- branches form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
91
Is starch found in animal cells
Never
92
In what type of organisms is glycogen found
Animals + bacteria but never in plant cells
93
Describe two ways in which glycogen is differnt from starch
Glycogen has shorter chains and is more highly branched
94
Where is glycogen stored within animals
As small granolas mainly in the muscles and the liver and
95
Describe and explain 4 ways in which the structure of glycogen suits its function
Insoluble so doesn’t tend to draw water into cells by osmosis
Insoluble - doesn’t diffuse out of cells
Compact - a lot can be stored in a small space
More highly branches than starch so has more ends that can be acted in simultaneously by enzymes so more rapidly Borden down to form glucose monomers (which is used in respiratuon)
96
Which monomers join to form the polysaccharide cellulose
Beta - glucose
97
Which structure of a plant cell contains large amounts of cellulose
Cell wall
98
Describe 2 functions of a cell wall
Prevents cell from bursting as water enter by osmosis (does it by exerting an inward pressure to stop any further influx of water
Strengthens the cell wall + provides rigidity to the plant cell
99
How is the structure of cellulose suited to its function of providing support and rigidity
- cellulose molecules are made up of b-glucose and so form long straight , unbranched chains
- there cellulose molecular chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength
-These molecules are grouped to from microfibrils which in turn are grouped to form fibres all of which provide more strength
100
What is known as animal starch
Glycogen
101
Describe simply how you might identify the concentration of glucose in a solution of unknown concentration, less than one mol
1) dilute the stock solution
2) aim to make 5 to 6 different glucose solutions
3) preform the Benedicts test on each one
4) filter precipitate dry constant mass and weight
5) graph.
6) Find unknown mass + use graph to find glucose conc.
102
What is a colourimeter
An instrument that beams a specific wavelength (colour) of light through a sample and measure how much light is absorbed
103
What are the 3 main classes of lipids
Triglycerides
Phospholipids
Waxes
104
What are the 4 main roles of lipids In living organisms
Source of energy
Waterproofing
Insulation
Protection
105
What are lipids main roles in living organisms - source of energy
When oxidise lipids provide more than twice, the energy of the same mass of carbohydrates and release valuable water
106
What are lipids main roles in living organisms - waterproofing
Lipids are insoluble in water, and therefore useful as a waterproofing. Both plants and insects have waxy lipid cuticles that conserve water.
mammals produce only secretion from glands in the skin.
107
What are lipids main roles in living organisms -insulation
Fats are slow Conductors of heat, and when stored beneath the body surface, they help to retain body heat. They also act as electrical insulator in the myelin sheath around the nerve cell
108
What are lipids main roles in living organisms - protection
Fat is often stored around delicate organs, such as the kidney
109
What are the major components of triglycerides
Glycerol
3x fatty acids
110
Formula of glycerol
C3H8O3
111
Formula of fatty acid
R- COOH
112
What is a hydrocarbon chain
A chain of only hydrogen and carbon
113
What letter is used to represent a hydrogen chain in fatty acids
R
114
What does saturated mean
No C=C double bond in the hydrocarbon chain
115
What does unsaturated mean
1 or more C=C double bonds in hydrocarbon chain
116
What does a double bond in fatty acid cause the molecule to do
Bend
They cannot pack together as closely so the triglyceride would be liquid at room temp (eg oil)
117
Fats that are solid at room temp (eg, butter) have more what bonds
Saturated fatty acids
118
Liquids at room temp have more what bonds
Unsaturated fatty acids
119
What type of reaction is involved in triglycerides formation
Condensation
120
What type of bond is in triglyceride
Ester bond
121
Are triglycerides polymers
No as they arnt made of repeating polymer units
122
Describe how a phospholipid differnt in structure compared to a triglyceride
Phospholipid and triglyceride both have a glycerol, but in phospholipid one of the 3 fatty acid has been replaced by a phosphate group
123
The phosphate head in phospholipids is …. (In terms of water)
Hydrophilic - attracted to / interacts with water
124
The fatty acid tails in phospholipids is …. (In terms of water)
Hydrophobic - repels water but mixes readily with fat
125
Due to having hydrophilic heads and hydrophobic tails, the phospholipid molecule is…?
Polar
126
When a phospholipid molecule is placed on the surface of water - what is formed
Monolayer
127
What is formed when a phospholipids is mixed into the water
Micelle
128
What is formed when there is water on both sides of a phospholipids.
Eg,
Forms a phospholipid bilayer with a hydrophobic core
Eg. In cell membranes
129
What is the test for lipids
1) take a dry and grease free test tube
2) to 2cm3 of the sample being tested add 5cm3 of ethanol
3) shake the tube thoroughly to dissolve any lipid in the sample
4) add 5cm3 of water and shake gently
5)a cloudy white coloured (white emulsion) indicates the presence of a lipid
130
Where are inorganic ions found
Cytoplasm of cells and in the body fluids of organisms
131
Define ion
Charged particle due to loss or gain of electrons
132
Distinguish between cations and anions
Cations have a positive change and anions have a negative charge
133
Formula of phosphate ion
PO4 3-
134
Function of a phosphate ion
- a component of DNA and ATP and ATP
- major constituent of bone and teeth
- a component of cell membranes, on the form of phospholipids
- it’s the bonds between phosphate groups that store energy in ATP
- the phosphate groups in DNA and RNA z allow nucleotides to join to form the polynucleotides
135
Formula of a sodium ion
Na +
136
Function of a sodium ion
- involved in the co-transport of glucose and amino acids across cell- surface membranes
- helps to maintain electrical, osmotic and anion/cation balence across cell membranes
- a molecule of glucose or an amino acid can be transported into a cell alongside sodium ions. This is known as co-transportation
137
Formula od iron ion
Fe 2+
Fe. 3+
138
Function of an iron ion
Forms part of haemoglobin (within the haem group)
Found in electron carriers used in respiration and photosynthesis
It’s made up of 4 differnt polypeptide chains, each with an iron ion in the centre
When oxygen is bound, the fe 2+ ion temporary becomes a fe 3+ ion until oxygen is released
139
Formula of hydrogen
H+
140
Function of hydrogen
PH is a measure of the conc. of this ion; the more of this ion , the lower the PH
141
Function of magnesium ion
Found within the chlorophyll molecule
142
What is an Organic molecule
Molecules that contain carbon and gap hydrogen and can include other elements
143
What is ATP
Adenosine TriPhosphate
- a nucleotide
- an energy carrier/ chemical used in living organisms to transfer energy
144
What makes up ATP
Adenine (base)
Ribose (5 sugar carbon)
3x phosphate
145
ADP + Pi
What does Pi stand for
Inorganic phosphate
146
How does ATP store energy
In the bonds
The bonds between the phosphate groups are unstable and so have a low activation energy - so are easily broken - when this happens energy is released.
Usually only the terminal phosphate is removed
147
What type of reaction is ATP synthesis
Condensation
Needs and input of energy
148
What is ATP synthesIs catalysed by
Enzyme ATP synthase
149
What is ATP hydrolysis catalysed
Enzyme ATP hydrolase / ATPase
150
what does ATP hydrolysis release
Energy
151
T or f
The conversion of ATP to ADP is reversible
T
152
What is the name for an addition of a phosphate group
Phosphorylation
153
Energy is needed for phosphorylation
What 3 reactions can give the energy needed
Photophosphorylation (light - photosynthesis)
Oxidative phosphorylation
Substrate-level phosphorylation
( respiration reactions)
154
ATP synthesis reaction
ADP + Pi —> ATP + H2O
155
ATP hydrolysis reaction
ATP + H20 —> ADP + Pi + (energy)
156
Why is ATP not a good long term energy store
Due to its instability of its phosphate bonds
157
Why is ATP better than glucose for immediate energy
- hydrolysis of 1 ATP molecule releases less energy than each glucose molecule. The energy for reactions is therefor being released in smaller and more manageable quantities than that released by glucose
- ATP is broken (hydrolysed) in a single step reaction and so energy is release is quicker (ATP is readily hydrolysed), the breakdown of glucose is a long series of reactions such that energy release takes much longer.
158
What are the lipids found in cell membranes called
Phospholipids
159
Why are triglycerides insoluble in water
The tails are hydrophobic
160
Why are triglycerides mainly used as energy storage molecules
+ why don’t they affect water potential in a cell
1) the long hydrocarbon tails of the fatty acids contain lots of chemical energy - a load of energy is released when there broken down . Because of these tails, lipids contain about twice as much energy pre gram as carbohydrates
2)they’re insoluble, so they don’t affect the water potential of the cell amd cause water to enter the cells by osmosis (which would make them swell) the triglycerides clump together as insoluble droplets in cells becuase the fatty acid tails are hydrophobic - the tails face inward shielding themselves with th water from there glycerol heads
161
Why can’t water-soluble substances easily pass though the cell membrane
The centre of the bilayer is hydrophobic
The membrane acts as a barrier to those substances
162
Plant and animal cells release energy from glucose via
Respiration
163
A cell can’t get its energy directly from glucose
So..
In respiration the energy released from glucose is used to make ATP
164
What is ATP known as and why
Nucleotide derivative because its a modified form of a nucleotide
165
Once ATP is made - where does it go
ATP diffuses to the part of the cell that needs energy
166
Where is the energy stored in ATP
In high energy bonds between the phosphate groups.
It’s released via hydrolysis reactions
167
When energy is needed by a cell ATP is broken down into “
ADP and Pi
168
ATP hydrolysis can be ‘coupled’ to other energy requiring reactions in the cell
- what does this mean
The energy released can be used directly to make the coupled reaction happen, rather than lost as heat
169
From ATP broken down , what can the Pi be used for
Added to another compound (called phosphorylation) which oftern makes the compound more reactive
170
What does ADP stand for
Adenosine diphosphate
171
What is an ion
An atom or group of atoms that have an eletrical charge
172
What are the 5 uses of ATP
Metabolic processes
Movement
Active transport
Secretion
Activation of molecules
173
ATPs use in metabolic processes
Energy For building up macromolecules from their basic units
Eg. Starch from glucose
174
Use of ATP In movement
Energy for muscle contraction, in muscle contraction, ATP provides energy for the filament of muscle to slide past each other + therfore shorten the actual length of the muscle fibre
175
Use of ATP in active transport
Energy to change the shape of carrier proteins in plasma membranes- allows molecules or ions to move against the concentration gradient
176
Uses of ATP in secretion
ATP is needed to from the lysosomes necessary for the secretion of cell products
177
Use of ATP in activation of molecules
Inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive , thus lowering activation energy in enzyme - catalysed reactions
Eg. Addition of phosphate to glucose molecules at the start of glycolysis
178
Why is ATP continuously produced
ATP can’t be stored so it Is continuously produced to be used as an immediate energy source. Also ATP can’t diffuse in + out of cells
179
Waters chemical formula
H2O
180
What are water molecules described as being
Polar
181
Why are water molecules described as being polar
The hydrogen atoms have a slight positive change and the oxygen has a slight negative change .
182
Why are water molecules polar
It’s due to the uneven distribution of electrons
183
Why do hydrogen bonds form between adjacent water molecules
Opposite changes attract so attractive forces called hydrogen bonds form
184
Why is cohesion
The tendency of molecules to ‘stick’ together
185
Does water have a strong or weak cohesion
Strong
186
What does water having a strong cohesion explain in plants
Explains why long columns of water can be pulled upward through the xylem vessels of tall trees in the process of transpiration
It also explains surface tension which allows small animals to walk on water
187
What does it mean that water has a relatively high heat capacity
It doesn’t change temperature easily
188
How is water having a high heat capacity usefull
It minimises fluctuations in temperature, aquatic organisms such as fish can live in very stable environments, it also helps larger organisms which are mainly composed of water maintain a stable temp.
189
What does it mean that water has a relatively large latent heat of vaporisation
Water requires a lot of energy to change state from a liquid to a gas.
190
What is water having a large latent heat of vaporisation due to
The hydrogen bonding between water molecules making them more difficult to separate
191
Why is water having a large latent heat of vaporisation usefull
Ensures that sweating in animals and transpiration in plant are effective cooling mechanisms - as water evaporates it extracts heat from around it, cooling the organism
192
T or f
Water is a very good solvent
T
193
Water is not easily compressed so it can be used to provide an internal ……..
Support
194
What % of our cells content is water
80%
195
Functions of water
A metabolite
Solvent
Temperature contr9
Cohesive
196
Examples of what water is a metabolite in
Condensation and hydrolysis reactions
197
What is a metabolic reaction
Chemical reaction that happens in a living organism to keep the organism alive. a metabolite is a substance involved in a metabolic reaction
198
What is the name of the bonding between the negatively charges oxygen and positive hydrogen on other water molecules
Hydrogen bonding
199
How is water an important metabolite
Many metabolic reactions involve condensation or hydrolysis
Hydrolysis requires a molecule of water to break a bond and condensation released a molecules of water when a new bond is formed
200
Why can water buffer changes in temp
Hydrogen bonds between water molecules can absorb a lot of energy
So water has a high specific heat capacity - it takes a lot of energy to heat it up
201
Why is water being able to buffer temperature useful
Means that water doesn’t experience rapid temp change.
Makes water a good habitat because the temp under water is likely to be more stable than on land. The water inside organisms also remain at a fairly stable temp,- helping them maintain a constant internal body temp
202
What makes water a usefull solveny
Polarity
203
What is cohesion
The attraction between molecules of the same type
Water molecules are very cohesive as they are polar
204
What does strong cohesion make water do
Flow
Great for transporting substances
+ has a high surface tension when it comes into contact with air
205
Are proteins polymer
Yes
206
From which monomer units are they formed
Amino acids
207
Which four elements are found in all proteins
Carbon
Hydrogen
Oxygen
Nitrogen
208
When element is found in some proteins
Sulphur
209
Are proteins organic or inorganic molecules
Organic
210
Name 6 functions of proteins
Structural
Catalytic
Regulatory
Transport
Immunological
Cell transport + recognition
211
Function of proteins as cell transport + recognition
Some proteins act as membrane pumps, channels and receptors
212
Function of proteins are transport examples
Carrier molecules such as haemoglobin
213
Examples of proteins are immunological function
Antibodies
214
Examples of proteins as regulatory
Hormones such as insulin, glucagon and Adrenalin
215
Examples of proteins as structural proteins
Collagen and keratin
216
Examples of proteins as catalytic
Enzymes
Eg. Amylase, lipase
217
How many naturally occurring amino acids are there
20
218
What does an amino acid general structure consists of
Central carbon atom
Amino group
R group
Carboxyl group
219
Which group in an amino acid is chemically basic
Amino group
220
Which group in an amino acid is acidic
Carboxyl
221
What letter in an amino acid represents the variable group
R
222
What is the smallest amino acid
Glycine
223
What reaction joins 2 amino acids together
Condensation
224
What are the products formed when 2 amino acids join together
Water
Dipeptide
225
What is the bond formed in between 2 amino acids
Peptide bond
226
Many amino acids can join up in a series of condensation reactions to form an unbranched chain called.
And through what process?
Polypeptide
Polymerisation
227
What is always at the end of a polypeptide
The N-terminus (amino group)
The C terminus (Carboxylic acid group)
228
Can proteins consist of one or more polypeptides
Yes
229
How do u test for a protein
Add burnet
Changes from blue to purple
230
What are the 4 levels of organisation of protein structure
Primary
Secondary
Tertiary
Quaternary
231
Describe the primary structure of the organisation of a protein
The specific order of amino acid in a protein
232
Describe the secondary structure of the organisation of a protein
The rotation or twisting of a polypeptide chain into a repeating pattern such as an a-helix or b-pleated sheet
233
Describe the tertiary structure of the organisation of a protein
The overall 3D structure of a polypeptide as the result of interachain interactions between R groups
234
Describe the quaternary structure of the organisation of a protein
The linking together of more than one polypeptide chain
235
What bonds are involved in the primary structure of proteins
Peptide
236
What bonds are involved in the secondary structure of proteins
Hydrogen bonds between the peptide bonds
237
What are the bonds in the tertiary structure of a protein
Hydrogen bonds,
Ionic bonds
Disulphide bridges
238
What are the bonds in the quaternary structure of a proteins
Peptide
Hydrogen
Ionic
Disulphide
239
Is the primary structure present in all proteins
Yes
240
Is the secondary structure present in all proteins
Yes
241
Is the tertiary structure present in all proteins
Yes
242
Is the quaternary structure present in all proteins
No
243
When is a polypeptide formed
When 2 or more amino acids join together
244
What are proteins made from
One or more polypeptides
245
When do disulphide bridges form
Whenever 2 molecules of the amino acid cysteine come close together
The sulfur atom in one cystesine bound to the sulfur atom in the other.
246
For what proteins is tertiary the final structure
Proteins made from a single polypeptide chain
247
Examples of when the quaternary structure is the final 3D structure
haemoglobin
Insulin
Collagen
248
Shape of enzymes + why
They’re usually roughly spherical in shape due to the tight folding of the polypeptide chains
249
Are enzymes soluble
Yes
250
Enzymes examples of roles
In metabolism
Synthesis large molecules
251
What are antibodies made up of
2 light polypeptide chains and 2 heavy polypeptide chains bonded together
They have variable regions
The amino acid sequence in these regions vary greatly
252
Explain transport proteins
Channel proteins are present in cell membranes. Channel proteins contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel.
These proteins transport molecules and ions across membranes
253
What do structural proteins consist of
Long polypeptide chains lying parallel to each other with cross links between them
Eg, keratin and collagen
254
What is the test for portion
1) the test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution
2) then add some copper (ll) sulfate solution
- if the protein is present it will turn purple
- if there are no proteins it will stay blue
255
Definition of the secondary structure of proteins
The secondary structure refers to the folding of a polypeptide chain as a result of hydrogen bonds forming between peptide bonds within the chain, resulting in regions called alpha-helices or beta-pleated sheets
256
Define disulphide bonds
Form between two amino acids that contain thiol (SH) groups. The two SH groups can be oxidised and join together to form a disulphide bond, its a strong covalent bond
257
Explain ionic bonds in the tertiary structure
Formed between amino acids with negatively charged R-groups and Those with positively charged R-groups, these are stronger than hydrogen bonds but weaker than disulphide bridges
258
Definition of tertiary structure
The tertiary structure is the 3rd shape of a polypeptide caused as a result of intrachain bonds between Rgroups of differnt amino acids. The bonds involved in the tertiary structure inculde: ionic bonds, hydrogen bonds and disulphide bridges
259
How many polypeptide chains link to form the quaternary structure
Two or more
260
When are bonds said to be interchain
The R- grounds of amino acids within differnt polypeptide chains can form bonds with one another two form the overall proteins.
Said to be interchain binds because they are between differnt polypeptide chains
261
Explain the structure of haemoglobin
4- protein chains
- 2 alpha and 2 beta each with a ring like heme group containing an iron atom
262
Describe the structure of insulin
2 long amino acid chains or polypeptide chains
263
Describe the structure of collagen
3 chains
-wound together in a triple helix
264
Explain how a change in the sequence of bases in DNA a may prevent an enzyme from carrying out its normal function
1-
265
From which biological molecules are all enzymes made
Proteins
266
What monomer units are joined together to build a enzyme
Amino acids
267
What is a biological catalyst
They give an alternate reaction pathway with a lower activation energy to increase rate of reaction in living organisms
They are not used up
268
Are enzymes vital for life
Yes
Body reactions would be too slow to sustain life
269
What does intracellularly working enzymes mean
enzymes use the inside of cell
270
What are extracellularly working enzymes
Released from other cells
271
Explain the lock and key model
The enzyme acts as a lock and substrate as a key
As keys are specific to locks substrates are specific (complementary) to enzymes
272
Can enzymes by used again
Yes
It’s active sight stays almost the same so remeians complementary
273
Explain how enzymes can be involved in anabolic and catabolic reactions.
Catabolic breaks the substrate up (big molecules to small)
Anabolic builds up molecules
274
What determines an enzymes function
There 3D shape
(Tertiary structure)
275
What is enzymes tertiary structure determine by
The position of hydrogen, ionic and disulphide bonds that forms between the r-groups of amino acids. These bonds cause the polypeptides to fold up into a specific overall 3D structure
276
When the substrate binds to the active site what is it called
Enzyme-substrate complex
277
Why are products released from the active sight
As they are no longer complementary to the active site
278
Explain how a change in primary structure of a protein may prevent an enzyme from carrying out its normal function
(Exam Q)
1) a change in the primary structure means a differnt sequence of amino acids
2) this means that the type and or order of the R group has changed
3) this changed the type and the position of hydrogen, ionic and disulphide bonds that form between the R groups
4) eg. If additional cysteine amino acid appears in the polypeptide, extra disulphide bonds may be formed in new locations
5) the protein folds into differnt overall tertiary structure
6) the active site of the enzyme may have a new shape
7) the substrate is no longer able to bind to the active site
8) the enzyme can or carry out its normal function
279
What is the activation energy
The minimum amount of energy required for a reaction to start
280
What do enzymes do to activation energy
Lower it
281
Describe two ways in which energetics of with/without catalysts are the same
- reactants and products have the same energy at the start and end
- releasing same amount of energy overall in both reactions
282
How do enzymes lower activation energy
They split up the reaction into several stages, each which has a smaller activation energy.
Eg, the substrate first binds to the enzymes to form an enzymes substrate complexm then the products are formed, then the products are released.
Each of these smaller steps require less energy. Without an enzyme the substrate is converted directly into products
283
What do enzymes allow for reactions
To take place at lower temperatures.
More molecules will have the necessary lower energy to allow the reaction to proceed
Product is formed more quickly -
The rate of reaction has increased
This allows some metabolic processes to occur rapidly at human temps.
284
Except form breaking up into several stages how else do enzymes lower activation enru
- the formation of an enzyme substrate complex might bring the substrate molecules close together and in the correct orientation, making it easier and more probable that a reaction will occur
- the enzyme may put the substrate molecules under stress so that bonds are weakened and therefore bonds may break easier
285
Who proposed the lock and key model + when
German chemist
Emil Fischer in 1894
286
What does the lock and key model propose
That emzymes work in the same way as a key operates a lock; each key has a specific shape that will only fit into and therfore open a particularly shapes, single lock. In this way , the tow fit together a bit like rigid puzzle pieces
287
How long did lock and key stay the accepted theory
60 years
288
Why was the lock and key model repelac3s
New experimental techniques allowed researchers to probe enzyme action more closely,
A number of observations began to emerge that did not fit with the lock and key model
289
When and who replaced the lock and key theory
1950s
Daniel Koshland
290
What did new techniques reveal about enzymes
Proteins are not rigid structure
Other molecules were showed to bind to enzymes away from the active site and actually alter the shape of the enzyme. This shows that enzymes are flexible and able to change shape rather than being fixed, rigid structures.
291
What is a limitation of lock and key model
It could not explain non-competitive inhibiation
292
What theory did Koshland propose
Induced fit model
293
What is rhe induced Fit model
Enzyme is not a rigid lock but it actually changes shape slightly to fit the profile of the substrate.
Before the substrate Bind to the enzyme, the substrate and the active site are not precisely complimentary in shape as the substrate binds, the active site, changes, shape and moulds more closely around the substrate to form the functional active site.
The proximity of the substrate therefore induces the active site to adopt a perfect fit as the active site changes, shape, substrate molecule are put under tension
Once the product leaves rhe active sire relaxes back to the original position
294
When did Koshland induced fit theory become accepted
Had to wait for the development of a technique known as x-ray crystallography, which allowed scientists to measure very small movements of chemical groups in the active site. With research becoming more technical, involving specialist knowledge
295
Suggest why the induced fit model can be likened to a hand in a glove
The glove is complementary to the hand alike the active site to the enzymes is not rigid and slightly changed shape to give the perfect fit for the hand (like the perfect fit for substrates)
296
What is the multi-disciplinary approach
Lots of differnt researchers Woking together
297
What must happen for enzymes or work
Come into physical contact with its substrate
Have an active site which fits the substrate
298
What factors influence rate of enzyme catalysed reactions
Temperature
PH
Enzyme concentration
Substrate conc
299
How can you track progress of an enzyme controlled reaction
Formation of prodcuts over time
Substrate disappearing
300
Describe the graph wich shows product forming over time
-at first, there is a lot of substrate, but no product
-It is easy for the plentiful substrate molecule to come into contact with empty active site on enzyme molecules
- at any given moment all of the enzymes, active sites are filled The substrate is rapidly broken down into products
-the reactions proceed and the substrate is converted into products, the substrate concentration decreases while the products concentration increases
-is difficult for substrate molecules to interact with enzyme molecules as there are fewer substrate, molecules and product molecules may get in the way
-It therefore takes longer for substrate molecules to be broken down, and so the rate of substrate disappearance/product formation slows
-The rate of reaction slows until there is so little substrate left that any further substrate disappearance/product formation cannot be measured
-The graph flatten out because all the substrate has been used up and so no product can be formed
301
How to estimate rate of reaction at a specific point
A tangent
Find gradient
302
What do enzymes do
Catalyse metabolic reactions at a cellular level and for organisms as a whole
303
If two substrate molecules needed or be joined up how does an enzyme reduce activation energy
The enzyme holds them close together, reducing any repulsion between the molecules so they can bind easier
304
Rate of enzyme controlled reaction …….. when the temp increases
Increases
305
Why does temp increase rate of reactiom
More kinetic energy so molecules move faster.
Makes enzymes more likely to collide with the substrate molecule.
The energy of the collisions also increases, which means each collision is more likely to result in a reaction
But if the temp gets Too high the reactions tops
306
Describe the temp and rate of reaction graph look
1) the rise in temp makes enzyme molecules vibrate more
2) if the temp goes above a certain level thus Vibration breaks some of the bonds that hold the enzyme in shape
3) the active sire changes shape and the enzyme and substrate no longer fit together
4) at this point the enzyme is denatures - it no longer functions as a catalyst
307
What is human enzymes optimum temp
37°c
308
What is rhe optimum PH for human enzymes
7
Some exceptions such as pepsin that works best at 2 (this is usefull as it’s found in the stomach)
309
What happens to enzymes when the ph is above or below the optimum
The H+ and OH- ion found in acids and alkalis can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place. This makes the active site change shape, so the enzyme is denatured.
310
How does enzyme concentration affect enzyme rate of reaction
The more enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate complex. So increasing the concentration of the enzyme increases rate of reaction.
311
Why can the top of a rate of reaction to conc of enzymes level of
If the amount of substrate is limited, there come a point where there’s more than enough enzyme molecules to deal with all the available substrate so adding more enzymes has no further effect
312
How does substrate conc effect rate of reaction up to a point
The higher the substrate conc, the faster the reaction- more substrate molecules means collision between substrate and enzyme is more likely and so more active sites will be used
This is only true up to saturation point. (All active sites full) adding more makes not differnce.
Substrate conc decrease with thin during a reaction so if no other variables are changed the rate of reactaiom will decreases over time too
313
How can you measure the rate of an enzyme- controlled reaction due to temperatures
By collecting a gas
Catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
1) set up boiling tubes containing the same volume and concentration of hydrogen peroxide. To keep the ph constant, add equal volumes of a suitable buffer solution, add equal volumes of a suitable buffer solution to each tube. (Buffer added to resist changes to ph when smau amounts of acne or alkali are added
2) set up the apparatus, either with a gas, syringe, or an upsidedown measuring cylinder in a trough of water
3) put each boiling tube in a water bath to a different temperature along with another tube containing catalase and wait five minutes
4) use a puppet to add the same volume and concentration of catalase to each boiling tube, then quickly attach the bung and delivered tube (at school. We use potatoes)
5) record how much oxygen is produced every 30 seconds using a stopwatch. Repeat each temperature three times.
6) calculate the average rate of reaction each temperature
314
How to measure rate of enzyme controlled reactions by measuring how just the substrate is broken down.
The enzyme amylase catalyses the breakdown of starch to maltose
you can set up the experiment with a spotting tile with drops of iodine in potassium iodide .
A drop of iodine in potassium iodide is put into each well on a spotting tile a known concentration and relays and starch, and then mixed together in a test tube
A dropping pippett is used to put a drop of this mixture into one of the wells containing the iodienevsolution on the spotting tile, a regular intervals, and the resulting colour is observed
The iodine solution goes dark, blue black when starchis present, but remains its normal orange colour when no starch is present
you can see how fast amylase is working by recording how long it takes for the iodine solution to turn blue black when starch /amylase is added,
Repeate the experiment using different concentration of amylase (. repeat the experiment, three times for each amylase concentration.
315
How to complete the practical:
The effect of temperature on the rate of an enzyme reaction
1) using a marker pen, write an x on the glass halfway down 3 test tubes
2) add 10cm3 of the solution of milk powder to each of these tree test tubes
3) add 2cm3 of trypsin solution to 2cm3 of PH7 buffer in another set of three test tubes
4) stand the three test tubes containing the solution of milk powder and the three test tubes containg trypsin and buffer in a water bath at 20°c
5) leave all 6 tubes in a water bath for 10 mins
6) mix one of each textures togerth
7) put back in water bath
8) repeate for the next 2 and then the next 2
9 time how long it takes for the milk to go clear ( when u can see the x)
10) record the time
11) repeate at temps, 30, 40, 50, 60
316
2 types of inhibitors?
Competitive
Non-competitive
317
What is a competitive inhibitor
Molecules that have a similar shape to that of the substrate molecule
They compete with the substrate to bind to the active site (but no reaction takes place)
They block the active site - sono substrate can fit in
318
What does how much enzyme is inhibited depend on
The relative concentrations o the in inhibitor and the substrate
319
If there is a high concentration a the competitive inhibitor how will it effect rate
It will take up all the active sites and hardly any of the substrates will get to the enzyme
So a lower rate of reaction
320
What will happen if there is a higher concentration of substrate than competitive inhibitor
The substrate chances of getting to an active site before rhe inhibitor increase. So increasing the concentration of subsrate will increase rate of reaction ( up to a point)
321
What is a non competitive inhibitor + how does it work
Bind to the enzyme away form its active site
Causes active site to change shape so the substrate molecule can no longer bind to it
322
Why don’t non competitive inhibitors compete with substrate
Inhibitors don’t bind to the active site becuase they are a differnt shape
323
How does increasing concentration of substrate effect rate of reaction with non competitive inhibitors
Inc, conc, of substrate won’t make any differnce to the reaction rate
324
What does DNA carry
The genetic code
325
What are both DNA. And RNA known as
Nucleic acids
326
Why are DNA and RNA known as nucleic acids
They are weak acids
327
What is the monomer nucleic acids are made from
Nucleotides
328
Are nucleic acids polymers
Yes
329
What elements does a nucleotide contain
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphate
330
What 3 components make up a nucleotide
1) a 5 carbon sugar called pentose
2) a phosphate group
3) a organic, nitrogenous base
331
What is the formula for the phosphate group of nucleic acids
PO4 2-
332
In DNA what is the sugar called
Deoxyribose
333
What charge does the phosphate group in DNA have and what does it make DNA
Negative charge
Makes DNA a highlt charged molecule
334
What properties does the negatively charges phosphate group give DNA
It’s acidic properties
335
How many bases does DNA contain
R
336
What elements does the 4 bases in DNA contain
Carbon
Hydrogen
Oxygen
Nitrogen
337
What are the 4 bases of DNA known as
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
338
Which pairs bases have similar structures
C and T ( smaller)
And A G ( larger)
339
What structure do thymine and cytosine have
A single ring structure called pyrimidines
340
What is rhe structure of adenine and guanine
Double ring
Called purines
341
Via what reaction are the deoxyribose sugar, phosphate and base assembles
Through condensation
342
Deoxyribose sugar , phosphate and base are assembled through condensation reaction to form a ………….
Mononucleotide
343
What is DNA made of
4 differnt types of nucleotides
344
How do 2 nucleotide units combine together
Through condensation reaction between sugar and phosphate group
345
What is the bind formed between sugar and phosphate in DNA called
Phosphodiester bond
346
What is a phosphodiester bond
Strong covalent bonds between sugar and phosphate group in DNA
347
When many nucleotides join up, what is it called?
Polynucleotide strand
348
The 2 strands of DNA are joined by what?
Weak hydrogen bonds
349
What form between the bases in DNA
Weak hydrogen bonds
350
How many hydrogen bonds form between A and T
2
351
How many hydrogen bonds form between C and G
3
352
When and by who did Chargaffs rule of base pairing arise
1951
Edwin chargaff
353
What did Edwin chargaff do
Analysed DNA from differnt species, he separated the 4 bases from DNA and measured them quantitatively.
He discovered that amount of A and T where very similar and C and G.
Later reasearch showed these bases must pair up
354
Why does A or G have to pair whir C or T
Because the distance between rhe 2 polynucleotide strands must be constant. As A , G are double ringed (larger) if they paired it would be long ‘rung’ ( if C and T joined it would be short’ rung’)
The distance between the 3 sugar phosphate backbones can only be maintained by ATand CG bonding
355
When and by who found the exact overall structure of DNA
1953
Crick and Watson
356
If you had 21% of Adenine how much thymine should you have
21%
They pair together
357
Why in virus DNA is there not the same amount of T and A bases
It’s single stranded
358
What 2 strands are DNA made up form
Polynucleotide strands
359
What are the 2 polynucleotide strands in DNA describes as
Anti parrallel
They run in opposite directions
360
DNA has a ……………….. backbone
Sugar phosphate
361
What is a sugar phosphate backbone
The alternating sugar and phosphate groups are joined together by strong covalent bonds called phophodiester bonds
362
What is the structure of DNA
Double helix
363
What do hydrogen bonds offer during DNA replication
Natural line of cleavage
364
Describe DNA replication
1) DNA double helix is nicked and the hydrogen bonds between the complementary base pairs are broken
2) this occurs due to the action of hot enzyme helicase and results in the unwinding and separation of the two polynucleotides
3) bases are now exposed, the separate polynucleotides act as templets for the addition of free activated nucelotides
4) these pair with complement Barry vases that have been exposed on unwound DNA
5) once in position the enzyme DNA polymerase catalysed the linking together of the activated nucelousided through covalent phosphodiester bonds. Two new polynucleotides strands are formed
6) there are now 2 daughter DNA molecules each of which contains one of the orgiiinal stands of DNA and one new one
7) this is called semi conservative replication
365
What enzyme nicks the hydrogen bonds in DNA and results in the unwinding and separation of the 2 polynucleotides
Helicase
366
Is DNA replication active or passive
Active
Energy is needed for the process of activation of nucleotides
367
Which enzymes catalysises the linking of the activated nucleotides through covalent phospdiester bonds
DNA polymerase
368
What is the process of DNA replication called
Semi- conservative replication
369
How does an increase in temperature effect rate of reaction
- inc kinetic energy of enzyme and substrate molecules
- moves more rapidly and collide more frequently with active site
- more forceful collision so greater proportion release enough energy to overcome the activation energy - more enzyme-substrate complexes form
- inc in rate
-optimum temp = greatest rate of reaction
- further inc, in temp over the optimum decreases the rates
- because atoms within the enzymes vibrate so vigorously that it causes her hydrogen bonds (and some ionic ) to break rate of the reaction/This is because the atoms within the enzyme vibrate so vigorously that it causes the ....
..Tertiary structure of the enzyme changes, including the shape of the active site.
At first this causes a small change in the shape of the active site such that the substrate fits less easily, decreasing the formation of ...enzyme... - substrate complexes and decreasing the rate of the reaction. However, as the temperature continues to increase, the enzyme's tertiary structure is so disrupted that the enzyme stops working altogether; we say that the enzyme is … denatured
and enzyme-substrate complexes cannot form. This is a
..permanent change that cannot be reversed by cooling. Eventually a temperature is reached where, All of the enzyme molecules have been denatured; the rate of reaction falls to 0
370
What is PH of a solution a measure of?
Concentration of hydrogen ions (H+) in a solution
More acidic is more hydrogen bonds
371
What is rhe formula to calculate PH of a solution
-log 10(H+)
Negative logarithm of the hydrogen ion concentration
372
What is the key feature of the PH graph on rate of reaction
It’s symmetrical
373
How does PH effect rate of reaction
Denaturation occurs because changes in pH affect the charges. on the enzyme (including charges on amino acid side chains of the enzyme's active site) and the substrate.
This could cause regions of the enzyme and substrate to adopt the Same electrical charge, thus causing electrostatic /repulsion.
Changes in pH could also cause ionic bonds and hydrogen bonds that maintain the enzyme's tertiary structure to break.. The active site would therefore change ..Shape... and enzyme-substrate complexes would not from
374
Describe rate of reaction in a low concentration of enzymes
There are too few enzyme molecules to allow all substrate molecules to find an active site at one time. The rate of reaction is therefore only half the maximum possible for the number of substrate molecules available
375
Describe rate of reaction at optimum enzyme concentration
with twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time.
The rate of reaction has doubled to its maximum because all active site are filled.
376
Describe rate of reaction when enzyme concentrations has gone beyond the optimum
The addition of further enzyme molecules has no effect as there are already enough active sites to accomodate all the available substrate molecules. There is no increase in rate of reaction
377
Describe rate of reaction with a low substrate concetnration on enzyme action
There are too few substrate molecules to occupy all the available active sites. The rate of reaction is therefore only half the maximum possible for the number of enzyme molecules available.
378
Describe rate of reaction when substrate conc is at its optimum
With twice as many substrate molecules available, all the active sites are occupied at one time. The rate of reaction has doubled to its maximum because all the active sites are filled.
379
Describe the rate of Reaction of substrate concentration past the optimum
The addition of further substrate molecules has no effect as all active sites are already occupied at one time. There is no increase in the rate of reaction
380
What is an enzyme inhibitor
Directly or indirectly interfere with the functioning of the active site of an enzyme and in doing so reduce enzyme activity
381
Are inhibitors permanent of not
Some bind permanently to the enzyme and are non reversible
But most only attach temporarily to the enzyme and so are known as reversible inhibitors
382
What is the shape of competative inhibitors
3D molecular shapes that are very similar to the enzymes normal substrate
383
How do competative inhibitors work
Competitive inhibitors have 3D molecular shapes that are very _Similar to that of an enzyme's normal substrate. They can therefore compete with the substrate for an available actine
When the inhibitor molecule is bound to the active site, it prevents the normal Substrare from binding and so no enzume Substrate complex is formed. It therefore temporarily inhibits this enzyme molecule from catalysing its reaction - the rate of the reaction is therefore slowed down.
384
What does the overall effect on enzyme activity depend on with competative inhibitors
The overall effect on enzyme activity (the rate of the reaction) depends on the relative amount of substrate and inhibiter molecules.
For example, if there were 99 substrate molecules for every inhibitor molecule, then 99% of collisions would be between enzyme and substrate and only 1% between enzyme and inhibitor. Consequently, at any one time, only 1% of the enzyme molecules would be inhibited and the reaction would proceed at_99% of the maximum rate. If the ratio was 75% substrate: 25% inhibitor, the rate would fall to 75% of its maximum.
For a fixed amount of inhibitor, an increase in substrate concentration reduces the effect of the inhibitor
Given that the inhibitors only bind temporarily to the enzyme, eventually a point will be reached when all substrate molecules will occupy an active site. However, the greater the concentration of inhibitor, the longer this will take.
385
Where do non competative inhibitors bind
Allosteric site
386
How do non competative inhibitors work
, non-competitive inhibitors do not compete with substrate molecules for the active site. Instead they bind to another area of the enzyme that is known as the ALLOSTERIC SITE! The binding of this inhibitor causes a change in Shape (conformational change) of the enzyme's active site such that substrate molecules can no longer bind - the enzyme cannot lunchen The effectiveness of a non-competitive inhibitor is not affected by the concentration of the substrate -
387
What is a metabolic pathway
A series of reactions in which each step is catalysed by a specific enzyme
388
In any one cell how many different structured metabolic pathways are there
Hundreds of
389
Where are the enzymes that control structures metabolic pathways
Attached to the inner membrane of the cell organelle in a very precise sequence
390
Describe the loook of the rate of reaction graph of enzymes for the vol of o2 on time
• At first there is a lot of substrate (hydrogen peroxide or starch),
but no product (water and oxygen or maltose)
- is is easy for the plentiful substrate molecules to come into contact with empty active sites on enzyme molecules
At any given moment all the enzyme active sites are filled the substrate is rapidly broken down into productions
As the reaction proceeas,and substrate is converted into product, The substrate concentration decreases untill The produce concentration increases
It Is more difficult for substrate molecue to come into contact with enzyme molecules as there are fewer substrate molecules may ‘get in The way’
It therefore takes longer for substrate molecules to be broken down, and so the rate of substrate disappearance slows
The rate of reaction slows until there is so little substrate left, but any further substrate disappearance cannot be measured
The graph. Flatterns out because all the subject has been used up and so no new product can be formed
391
How can we track a enzyme controlled reaction
Formation of product over time
Substrate disappearing
392
For an enzyme to work it must ….
Come into physical contact with its substrate
Have an active site which fits the substrate
393
The level of chemicals in a cell can be maintained at relatively constant levels through a process called …..
End product inhibition
394
How does end product inhibition work
If the level of end product increases in a cell above normal levels then this product can inhibit the action of an enzyme within the metabolic pathway, this prevents the substrate being converted into the next intermediate that needed the inhibited enzyme,
So ultimately less product will be produced
The levels will returned to Normal
395
What type of inhibitors is end product inhibiation ususlalt
Non competative
396
What is end product inhibition an example of
Negative feedback
397
Why is end product inhibition important
It would be imifficeint to produce something that is in excess of what is required
High conc of some substances could be toxic and may damage the cell
398
An enzyme controlled reaction is inhibited by substance x
Suggest a simple way in which you could tell whether substance x is acted as a competative or non competative I hibitor
Add lots more substare if the rate doesn’t increase its non competative
Is it does increase it is competative
399
What were the only 2 possible mechanisms for DNA replication
Conservative model
Semi conservative model
400
What is the conservative model
Suggested that the original DNA molecule remained inactive and that a separate daughter DNA copy was built up form new molecules of deoxyribose, phosphate and organic bases
Of the 2 molecules produced one would be made of entirely new materials while the other would be entirely origional material
401
What is the semi conservative model
Proposes that the origional DNA molecule split into two separate strands each of which then replicated it mirror image
Each of the 2 new molecules would have one strand of new material and one origional strand
402
Who found evidence for semi conservative replication
Meselsohn
Stahl
403
What 3 facts where the semi conservative replication experiment based om
1) all the bases in DNA contain nitrogen
2) nitrogen has 2 forms : the lighter N14 and heavier N15
3) bacteria will incoporate nitrogen form their growing medium into any new DNA that they make
404
Explain the semi conservative DNA replication experiment
They labelled the origional DNA of basketry by growing them on a medium of N 15
Then they transferred the bacteria to a medium of N14 for a single generation to allow it to replicate once
The mass of each new dna molecule would depend on which methord of replication has taken place
To separate out the differnt DNA types, they centrifuged the extracted DNA in a special solution
(Density gradient centrifugation )
The lighter the DNA the nearer he top of the centrifuge tube it collected
The heavier the DNA the n3arwr the bottom of the tube it collected
They also analysed the dna after 2,3 generation
405
What part of DNA contains nitrogen
The bases
406
Explain why after one generation all the DNA is made up of an equal mixture of N14 and N 15
DNA replication is semi conservative
This means the daughter dna has one new strand on each
407
What does RNA stand for
Ribonucleic acid
408
Describe the structure of RNA
Made of nucleotides (ribosesuga attached to nitrogenous bases and phosphate groups)
Mainly single strand
Bases (ACUG)
409
What does mRNA stand ofr messenger ribosnucelic acid
To carry protein nformarion form DNA in a cell nucleus to the cells cytoplasm where ribosomes read the mRNA sequence and translated each 3 bases into its corresponding amino acid
410
What does tRNA stand for
Transfer ribosnucleic acid
411
What does tRNA do
Helps decode messenger RNA sequence into a protein
Function at specific sites in the ribosomes during translation
412
What does rRNA stand for
Ribosomal ribonucleic acid
413
What is rRNAs function
Part of the ribosomes
Responsible for reading the order of amino acids and linking amino acids together
414
Why is DNA. Stable molecule
The phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
Hydrogen bond link, organic, base pairs, forming bridges (rungs) between the phosphodiester upright. As there are three hydrogen bonds between cystine and guanine the higher proportion of
C and G , pairings, the most stable, the DNA molecule.
There are other interactive forces between the base pairs that hold the molecule together
415
How has DNA adapted to carry out its function
1). It is a very stable structure which normally passes from generation to generation without change. Only rarely does it mutate
2) It’s two separate strands adjoined only with hydrogen bonds which allow them to separate during DNA replication and protein synthesis
3( it is an extremely large molecule and therefore carries an amount of genetic informatio
4) by having the base pairs within the helical cylinder of the deoxyribose phosphate backbone. The genetic information is to some extent, protected from being corrupted by outside, chemicals and physical forces.
5) base pairing leads to DNA, being able to replicate, and to transfer information as mRNA
416
What does the function of DNA depend on?
Sequence of base pairs
417
Function of rna
Transfer genetic information form dna to the ribosomes
Ribosomes read the rna to. Make polypeptides in translation
418
What are ribosomes made from
RNA
Protein
419
When was DNA first observed and what was the criticisms
What did some people believe
1800s
Lots of scientists doubted that it could carry the genetic code because it has a relatively simple chemical composition
Some belived that genetic info must be carried by proteins (which are more chemicaly varied)
420
WhenDNA showed to carry the genetic code and what else was discovered in this year
1953
Double helix structure also discovered by crick and Watson
421
What is shorter DNA or RNA
RNA
422
What does a phosphodiester bond consist of
The phosphate group and 2 ester bonds in dna
423
What is the bond between phosphate group and deoxyribose sugar
Ester bond
424
How are the ends of DNA stands differnt
one end is called 3’ (three prime) end and one end called 5’
425
How does the 3’ and 5’ end run in dna
In opposite directions
Antiparallell
426
The active site of DNA polymerase is only complementary to what
The 3’ end of the Newley forming dna stand
427
What end can DNA polymerase only add nucleotides too
New 3’ end
428
What is the new strand of DNA made in in terms of 5’ Nad 3’
5’ to 3’ direction and that DNA polymerase moves down the template strand in a 3’ to 5’ direction
Because the strands int he double helix are anti parallel the dna polymerase working on one of the strands moves into the opposite direction to the DNA polymerase working on the other template strand
429
Why did they use bacteria for the evidence of semi conservative replication
It’s divides quickly
