Biochemistry (3.1) Flashcards
1
Q
Carbohydrates
What is the general formula for a monosaccharide?
A
(CH2O)n
2
Q
Give 3 examples of a monosaccharide
A
Glucose
Fructose
Galactose
3
Q
Give 3 examples of a disaccharide
A
Sucrose
Maltose
Lactose
4
Q
Give 3 examples of a polysaccharide
A
Starch
Cellulose
Glycogen
5
Q
What is beta glucose and why?
A
An isomer
It has the same molecular formula but different structure ( the H and OH are switched)
6
Q
How is a disaccharide formed?
A
Condensation reaction
7
Q
Describe a condensation reaction.
A
Two monosaccharides join together and a water molecule is released.
8
Q
What bond joins two monosaccharides when they make a disaccharide?
A
Glycosidic bond
9
Q
What is another name for a glycosidic bond?
A
Alpha 1,4 bond
10
Q
Glucose + glucose —-> ?
A
Maltose + water
11
Q
Glucose + fructose —> ?
A
Sucrose + water
12
Q
Galactose + glucose —> ?
A
Lacoste + water
13
Q
What is the molecular formula for glucose?
A
C6H12O6
14
Q
Define the term hydrolysis.
A
A larger molecule is broken down into smaller molecules using water
15
Q
Define the term condensation.
A
Smaller molecules join together to make bigger molecules, a bond is formed and water is released.
16
Q
What is a polysaccharide’s monomer?
A
A monosaccharide
17
Q
Name 3 polysaccharides.
A
Starch
Cellulose
Glycogen
18
Q
What type of cells contain starch?
A
Plant cells
19
Q
How to plants ‘store’ starch?
A
In the form of starch grains
20
Q
Why do plants need starch?
A
Because it is a storage molecule (for long and short term storage).
E.g. overnight when photosynthesis cannot occur (stores energy for it to take place)
E.g. for long term storage over winter
21
Q
What is a reducing sugar?
A
A sugar that donates electrons to another substance (reducing that substance).
22
Q
What should you use to test for a reducing sugar? (And what is the colour change?)
A
Benedict’s reagent
Blue —> brick red
23
Q
What is the process of testing for the presence of a reducing sugar?
A
- Add an equal volume of Benedict’s reagent to the liquid sample bring tested.
- Heat in a gently boiling water bath for 5 minutes.
3.if a reducing sugar is present a brick red precipitate will form.
24
Q
What does semi-quantitative mean? (In terms of the reducing sugar test)
A
It doesn’t show an exact amount but shows a level of how much reducing sugar is present
25
What should you do to prove a sugar is non reducing after performing a Benedict’s reagent test with a blue result?
1. Add an equal volume of sample and HCl to a test tube to break the glycosidic bonds.
2. Boil for 5 minutes in a gently boiling water bath.
3. Neutralise by adding spatulas of sodium hydrogen carbonate- check wit ph paper. (The Benedict’s test wont work in acidic conditions)
4.perform Benedict’s test again (in equal volumes) and heat gently in a water bath for 5 mins.
5. If a non-reducing sugar was present in the original sample a brick red precipitate will form.
26
What are the two types of starch?
Amylose and amylopectin.
27
What type of bonds does amylopectin have?
Glycosidic
28
What ‘shape’ does amylopectin have?
Tree/brush like
29
What are the glucose monomers in amylose held together by?
Glycosidic bonds
30
How are the amylose polymer coils held into place?
Hydrogen bonds which form between hydroxyl groups
31
Is starch found in animal cells?
No only plant
32
How is starch well suited to its role of energy storage?
Insoluble -Doesn’t effect water potential
Large - doesn’t diffuse in and out of cells
Compact- a lot of it can be stored in once place
When hydrolysed it can form alpha glucose
The branched form (amylopectin) has any ends- can be acted on by enzymes simultaneously meaning glucose monomers are released rapidly
33
What is difference between the bonds in amylose and amylopectin?
Amylopectin has 1,4 and 1,6 glycosidic bonds whereas amylose has only 1,4 glycosidic bonds
34
In what type of organisms is glycogen formed?
Animals and bacteria
35
Two ways glycogen is different from starch
Shorter chains, more highly branched
36
Where is glycogen stored in animals?
Muscles and liver
37
Describe 4 ways in which the structure of glycogen suits its function
Insoluble - does not tend to draw water into the cells by osmosis
Compact - can be stored in small places
More highly branched than starch- more ends that enzymes can act on simultaneously (can rapidly be broken down into glucose monomers.
Insoluble- does not diffuse out of cells.
38
What type of cells is cellulose found in?
Plant cells
39
What part of the plant cell contains large amounts of cellulose?
Cell wall
40
What is cellulose’s monomer
Beta glucose
41
What must happen for the glycosidic bonds to form between two adjacent beta glucose monomers?
Each molecule must rotate 180 degrees relative to the one beside it.
42
what type of bonds are there between the monomers in cellulose?
1,4 glycosidic bonds
43
What is the effect of the alternating beta glucose molecules in cellulose?
Makes cellulose very straight
44
What is the structure of the chains of beta glucose in cellulose?
Long and unbranched
45
How do microfibrils form?
Hydrogen bonds form cross-links between parallel chains of beta glucose
46
Why are microfibrils so strong?
There are large numbers of hydrogen bonds
47
How are fibres formed?
Microfibrils are arranged in parallel groups
48
How are fibres arranged in the cell wall?
Aligned in a criss-cross direction
49
How Is cellulose well suited for its function?
Made out of Beta glucose which means they form straight unbranched chains. This means the chains can run parallel to each other and form microfibrils. These microfibrils then form fibres which provide the plant more strength
50
What are 3 types of lipids you must know about?
Triglycerides
Phospholipids
Waxes
51
How are lipids a source of energy?
When oxidised they produce energy. They release more energy than a carbohydrate
52
Why are lipids good for waterproofing?
They are insoluble.
Plants and insects have a waxy cuticle that conserve water.
Mammals produce an oily secretion from glands in the skin.
53
Why are lipids good insulators?
Fats are slow conductors of heat
Lipids can also insulate electricity eg in myelin sheath around nerve cells
54
Why are lipids good for protection?
Fat is stored round delicate organs eg kidneys
55
What is a triglyceride made of?
1 glycerol and 3 fatty acid molecules
56
What is the molecular formula for glycerol?
C3H8O3
57
What is the molecular formula for a fatty acid and what does the R stand for?
R-COOH
R stands for the hydrocarbon chain
58
What type of reaction forms a triglyceride?
Condensation
59
What molecules are released in a condensation reaction to form a triglyceride?
3 water molecules
60
How can you identify a saturated hydrocarbon?
No C=C bonds in the hydrocarbon chain
61
how can you identify an unsaturated hydrocarbon?
1 or more C=C bonds
62
Why is an unsaturated hydrocarbon liquid at room temperature?
The C=C bond/s causes the molecule to bend so it cannot pack together
63
What state of matter is a saturated hydrocarbon at room temperature?
Solid
64
What type of bond is formed in a triglyceride?
Ester bond
65
What does ATP stand for?
Adenosine Triphosphate
66
What is ATP?
An energy carrier/ chemical used in living organisms to transfer energy
67
What is the name of the base in ATP?
Adenine
68
What is the name of the 5 carbon sugar in ATP?
Ribose
69
What causes the terminal phosphate to be removed?
There are unstable bonds between phosphate groups meaning they have a low activation energy so the bonds are easily broken.
70
What type of reaction is ATP synthesis?
Condensation
71
What are the three energy sources for ATP synthesis?
Photo phosphorylation
Oxidative phosphorylation
Substrate-level phosphorylation
72
What is ATP synthesis catalysed by?
ATP synthase
73
What is the formula for ATP synthesis?
ADP + Pi ——> ATP + H20
74
What is ATP hydrolysis catalysed by?
ATP hydrolyse
75
What is the chemical equation for ATP hydrolysis?
ATP+ H20 ——> ADP + Pi + energy
76
What is an ion?
An atom or group of atoms that have an electrical charge
77
How are Ions formed?
Through loss or gain of electrons
78
What is an anion?
An ion with a negative charge
79
What is a cation?
An ion with a positive charge
80
What does an inorganic ion not contain?
Carbon
81
What is an organic molecule?
A molecule that contains carbon and hydrogen
82
What is the symbol for phosphate ion and its function?
PO4 3-
A component of DNA and ATP
83
What is the symbol for sodium ion and its function?
Na+
Involved in the co-transport of glucose and amino acids across cell surface membranes
84
What is the symbol for iron ion and what is its function?
Fe2+ or Fe3+
Forms part of haemoglobin
85
What is the symbol for hydrogen ion and what is its function ?
PH - a measure of the concentration of this ion
H+ (Ello. Remember you look beautiful x)
86
What is the difference between a phospholipid and a triglyceride?
One of the three fatty acids had been replaced by a phosphate group
87
What are the three parts of a phospholipid?
Phosphate head
Glycerol body
2 Fatty acid tails
88
What part of a phospholipid is hydrophilic?
Phosphate head
89
What part of the phospholipid is hydrophobic?
Fatty acid tails
90
What does hydrophilic mean?
Attracted to/interacts with water
91
What does hydrophobic mean?
Repels water but mixes readily with fat
92
The head and tails of a phospholipid behave different, what is this described as?
Polar
93
What do phospholipids form when placed on water?
A monolayer
94
Why do phospholipids form a monolayer when placed on water?
The heads are hydrophilic therefore are attracted to the water, whereas the tails are hydrophilic therefore they repel water>
95
When do phospholipids form a phospholipid bilayer?
When water is present on either side of the phospholipid e.g. cell membranes
96
why do phospholipids form a phospholipid bilayer?
So the hydrophobic tails are not in contact with water
97
What test do you perform when testing for lipids?
Emulsion test
98
What indicates the presence of lipids in the emulsion test?
A milky emulsion
99
How do you perform the emulsion test?
1. To 2cm3 of he sample being tested add 5cm3 of ethanol
2. Shake thoroughly to dissolve any lipids in the sample
3. Add 5cm3 of water and shake gently
4. A milky emulsion indicates the presence of a lipid
100
How would you perform calorimetry to find the concentration of an unknown glucose sample?
1) put your precipitate (from Benedict’s test) in a cuvette
2) put it in a calorimeter (which passes light through the sample
3)measure the absorbance/ transmittion
4) repeat for a number of glucose concentrations
5) do on unknown sample and use calibration curve on graph to determine its concentration
101
How do you perform a serial dilution test to estimate the concentration of an unknown glucose solution?
1) prepare a water bath.
2) label test tubes 1-5
3)using a 10cm3 pipette, place 10cm3 of 10% glucose solution in tube 1
4) take 1cm3 of the solution from tube 1 and place it in tube 2
5) add 9cm3 of water to tube 2. Shake to mix the contents (this is now a 1% glucose solution)
6)pipette 1cm3 of solution 2 into tube three. Add 9cm3 of water and shake. (0.1%) glucose.
7) repeat steps 4, 5,6 until all 5 test tubes contain glucose solution.
8) remove 1cm3 from test tube 5 so it also contains 9cm3
9)add 5cm3 of Benedict’s reagent into all 5 test tubes and put into a boiling water bath for 3 minutes.
10) remove the tubes and put in a test tube rack
11) place 9cm3 of solution ‘x’ into a test tube and add 5cm3 of Benedict’s reagent. Place in the water for 3 minutes.
12) remove from water and use results from tubes 1-5 to estimate glucose concentration in solution ‘x’.
13) record results in a suitable table.
102
What are the problems with using a serial dilution test to find out the concentration of an unknown glucose solution?
-subjective - estimates/ perception of colours are different
- 5 colour standards (not accurate)
- Benedict’s test is only sensitive to a certain level (does not identify low concentrations)
103
Are monosaccharides insoluble or soluble?
Soluble
104
Are polysaccharides soluble or insoluble?
Insoluble
105
ATP is an ______ energy source for a cell.
Immediate
106
Name two reasons why ATP is better than glucose.
- hydrolysis of 1 ATP molecule releases less energy than each glucose molecule. However, it is released in **smaller** more **manageable** quantities than released by glucose.
- ATP id hydrolysed (broken down) in a **single-step** reaction which means energy is released quickly, whereas the breakdown of glucose is aa long series of reactions (energy release takes much longer).
107
Name 3 uses of ATP.
- active transport
- cell division
- biosynthesis
- secretion
- activation of other molecules
- cell motility
- muscle contraction
108
Why is so much ATP produced?
- it cannot be stored so lots of ATP need to be produced to keep on providing energy (re-synthesising).
- it doesn’t diffuse in or out of cells so it has to keep on re-synthesising.
109
How des ATP effect the activation of other molecules?
The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive. This lowers their activation energy in enzyme-catalysed reactions e.g. the addition of phosphate to glucose molecules at the start of glycolysis.
110
What type of molecule is water?
Polar
111
What is a polar molecule?
A molecule that has oppositely charged ends
112
What charges do the oxygen and hydrogen have in water molecule?
Oxygen- slight negative
Hydrogen- slight positive
113
What do the oxygen and hydrogen atoms in water have different charges?
Because of the uneven sharing of electrons in the covalent bonds between oxygen and hydrogen atoms
114
Why does water have a strong cohesion?
There are hydrogen bonds between H20 molecules due t the oppositely charged poles that attract each other.
115
What explains why long columns of water can be pulled upwards through the xylem (in transpiration) and surface tension which allows small animals to walk on water?
Cohesion
116
Water has a relatively high heat capacity. What does this mean?
It means water cannot change **temperature** very easily.
117
Why does water having a high heat capacity benefit aquatic and larger organisms?
It minimises fluctuations in temperature meaning aquatic organisms live in very stable habitats and larger organisms that are mainly composes of water maintain a stable temperature.
118
Water has a relatively large **latent heat of vaporisation**. What does this mean?
It requires a lot of energy to change the state of H20 from a liquid to a gas.
119
Why does water have a large latent heat of vaporisation?
The hydrogen bonds between water molecules make them different to separate.
120
How does water’s large latent heat of vaporisation effect cooling systems of plants and animals?
It ensures that sweating in animals and transportation in plants are effective colony systems as when the water evaporates it extracts a large amount of energy from around it, cooling the organism.
121
Why is water a good solvent?
It readily dissolves other substances.
Ionic compounds dissolve in water because the ions are attracted to the charged ends of the water molecule.
122
In what process is water used to split large molecules into smaller ones?
Hydrolysis
123
What process is water needed for in plants?
Photosynthesis
124
Water cannot be easily compressed. What benefit does this have?
It can provide internal support. For example in the hydrostatic skeletons of earthworms and jellyfish. Also for turgidly in plant cells.
125
What is a protein’s monomer?
Amino acid
126
How many amino acids are there?
20
127
Give 3 examples of functions of a protein.
- structural proteins
- catalytic proteins
- regulatory proteins
- transport
- Immunological
- cell transport and recognition
128
What is the chemically ‘basic group’ in an amino acid?
The amino group
129
What is the **R** group in an amino acid?
The variable side chain
130
What is the acidic group in an amino acid?
Carboxyl group
131
How is a dipeptide formed?
The condensation reaction between two amino acid molecules
132
How is a polypeptide formed?
A series of condensation reactions of amino acids that form an unbranched chain
133
What is the amino group called at the end of a polypeptide chain?
N-terminus
134
What is the name of the carboxylic acid group at the end of a polypeptide chain?
C-terminus
135
What bonds join amino acids in the primary structure of a protein?
Peptide bonds
136
Describe the primary structure of a protein
The specific order of amino acids in a protein.
137
Describe the secondary structure in a protein.
The rotation or twisting of a polypeptide chain into a repeating pattern e.g alpha helix or beta pleated sheet.
138
What are the bonds in the secondary structure of a protein?
Hydrogen bonds between peptide bonds.
139
Describe the tertiary structure of a protein.
The overall 3D structure of a polypeptide as the result of interchain reactions between R-groups.
140
What bonds are there in the tertiary structure of a protein?
Hydrogen bonds, ionic bonds, and disulphide bridges.
141
Describe the quaternary structure of a protein.
Linking together of more than one polypeptide chain.
142
Is the quaternary structure present in all proteins?
No
143
What bonds are in the quaternary structure of a protein?
Any
(Peptide, hydrogen, ionic, disulphide bridges)
144
What are enzymes?
Biological catalysts.
145
Why are enzymes biological catalysts?
They lower the activation energy in a reaction by providing an alternate reaction pathway.
Found in living organisms.
Not used up in reactions.
146
What are enzymes made of?
Proteins
147
What is an enzymes monomer?
Amino acid
148
What is an intracellularly enzyme?
An enzyme that works inside the cell e.g. in the cytoplasm
149
What is an extracellularly enzyme?
Enzymes that are released from a cell.
150
What is an anabolic enzyme?
An enzyme that builds molecules up.
151
What is a catabolic enzyme?
An enzyme that breaks down molecules.
152
What do the active site and substrate have to be?
Complimentary
153
What is it called when the substrate ‘locks’ into the enzyme?
An enzyme-substrate complex
154
What is different about the products when they leave the enzyme’s active site?
They are no longer complimentary to the enzyme.
155
The ____ of an enzyme determines its function.
Shape
156
What is activation energy?
The minimum amount of every needed to start a reaction.
157
What does an enzyme do to the activation energy in a reaction?
It lowers it
158
What do enzymes do to the rate of a reaction?
Increase the rate of reaction.
159
How are the energetics of a reaction that isn’t catalysed by an enzyme the same as a reaction that is catalysed by an enzyme?
The reactants start with the same amount of energy and the products end with the Same amount of energy.
160
How does the induced fit enzyme model differ from the lock and key model?
It states that the enzyme is not a ridged lock but changes shape slightly to fit the profile of the substrate. Therefore they are not precisely complimentary in shape.
161
What is the changed active site shape called?
The functional active site
162
Does the active site turn to its original shape when the products leave (according to the induced fit model)?
Yes it relaxes to its original shape and is free to accept another substrate molecule.
163
What happens to the bonds when the substrate locks into an enzyme’s active site?
The bonds weaken a when the active site moulds to the shape of the substrate it puts the substrate molecule under stress.
164
How does an enzyme make a reaction between substrates more likely to happen?
It brings the substrate molecules closer together and in the correct orientation making it easier and more probable to occur
165
How do enzymes lower the activation energy?
They provide an alternative reaction pathway
166
How does an enzyme lower the activation energy?
It splits the reaction into several stages which has smaller activation energy. E.g the substrate 1st binds to the enzyme to form an enzyme - substrate complex, then the products are formed, then the products are released.
167
What would happen if we didn’t have enzymes?
Reactions would occur too slowly for us to stay alive.
168
Which factors affect the rate of an enzyme controlled reaction?
Temperature
PH
Substrate concentration
Enzyme concentration
169
Explain how temperature affects the rate of an enzyme controlled reaction.
An increase in temperature causes in increase in the kinetic energy of the enzyme substrate molecules. This causes them to move more rapidly and therefore collide with the active sites more frequently.
These collisions are more forceful meaning they release enough energy to overcome the activation energy and more enzyme-substrate complexes form.
A further increase in temperature above the optimum temperature (the temperature in which the rate of reaction is greatest) causes a decrease in the rate of reaction because the atoms within the enzyme vibrate too vigorously causing the hydrogen and ionic bonds in the enzyme to break.
The breaking of these bonds causes the tertiary structure to change, changing the shape of the active site. (At first this causes a small change in shape so the substrate fits less easily - decreasing the number of enzyme substrate complexes, decreasing the rate of reaction. However as temperature continues to increase the enzyme becomes denatured and no complexes can form. This is a permanent change so eventually when all the enzymes have been denatures the rate of reaction falls to 0)
170
What is PH a measure of?
The concentration of hydrogen ions in a solution.
171
How do you Calculate PH?
PH= -log10[H+]
172
Is PH is increased or decreased rate of reaction ______.
Falls
173
How does PH affect the rate of an enzyme controlled reaction?
A change in PH affects the charges on an enzyme and a substrate, leading to denaturation.
This change in charge can also cause regions of the enzyme and the substrate to adopt the same electrical charge, causing electrostatic repulsion.
Changes in PH can also cause ionic and hydrogen bonds that maintain the enzymes tertiary structure to break meaning the active site would therefore change and enzyme-substrate complexes would not form.
174
Describe the effect of enzyme concentration on the rate of an enzyme controlled reaction.
**Low enzyme concentration**
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.
**Intermediate 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 doubles to its maximum because all active sites are filled.
**High enzyme concentration**
The addition of further enzyme molecules has no effect as there are already enough active sites to accommodate all the available substrate molecules. There is not increase in the rate of reaction.
175
Describe the effect of substrate concentration on an enzyme controlled reaction.
**low substrate concentration**
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.
**intermediate substrate concentration**
With twice as many substrate molecules available, all the give sites are occupied at one time. The rate of reaction had doubles to its maximum because all the active sites are filled.
**High substrate concentration**
The addition of further substrate molecules has no effect as all active sites are already occupies at one time. There is no increase in rate of reaction.
176
What does DNA stand for?
Deoxyribose nucleic acid
177
Nucleic acid is a _______. It’s monomers are _______.
Polymer
Nucleotides
178
What 3 components is a nucleotide made up of?
Deoxyribose sugar (a 5 carbon sugar - Pentose)
A phosphate group (which has a negative charge)
An organic, nitrogenous base (A,T,C,G)
179
Bases C and T are a single ring structure called ____________.
Pyrimidines
180
Bases A and G are double ring structures called ______.
Purines
181
How to the deoxyribose sugar, phosphate and base form a mononucleotide?
Condensation reaction
182
What is the name of the bond formed between the sugar and phosphate group in a nucleotide?
Phosphodiesthter (a strong covalent bond)
183
What bonds form between the bases in DNA?
Hydrogen
184
CONDENSATION
Nucleotide + Nucleotide ————————> ?
Dinucleotide + water
185
What does base **A** stand for?
Adenine
186
What does base **T** stand for?
Thymine
187
What does base **C** stand for?
Cytosine
188
What does base **G** stand for?
Guanine
189
What is Cargaff’s rule of base pairing?
He discovered that the amounts of adenine and thymine were the same or very similar and that the amounts of cytosine and guanine were the Same or very similar.
190
Why will a purine always pair with a pryimidine?
Because in a molecule of DNA the distance between the 2 polynucleotide strands must be constant.
Adenine and guanine (purines) are double ring structures so are much longer than cystine and thymine. If adenine is paired with guanine this would produce a long ‘rung’ while cytosine pairing with thymine would create a short ‘rung’.
191
Viral DNA has an irregular number of bases, therefore it is ______ ___________ and has no base pairs.
Single stranded
192
W_____________ and C_______ worked out the exact structure of DNA in 1953.
Watson and Crick
193
Why are the polynucleotide strands in DNA described as anti-parallel?
They run in opposite directions
194
Why are the polynucleotide strands in DNA described as anti-parallel?
They run in opposite directions
195
The alternating sugar and phosphate groups are joined together by phosphoethster bonds. This forms the________.
Sugar-phosphate backbone
196
Describe the process of semi conservative DNA replication.
- The hydrogen bonds between the complementary base pairs are broken.
- this occurs to the action of the enzyme **helicase** and results in the unwinding and separation of the two polynucleotide strands.
- Bases are now exposed on each strand. These separated polynucleotide strands both act as templates for the addition of free, activated nucleotides (energy is needed for the process of activation).
- These pair with complementary bases that have been exposed on the unwound DNA (A with T and C with G)
- Once in position, the enzyme **DNA polymerase** catalyses the ‘linking together’ of the activated nucleotides through covalent phosphodiesther bonds. Two new polynucleotide strands are formed.
- There are now two daughter DNA molecules, each of which contains one of the original stands of DNA and one new one.
- For his reason, the process is known as semi-conservative replication.
197
The action of the enzyme _______ results in the unwinding and separation of the two polynucleotide strands.
Helicase
198
The enzyme ____ __________ catalyses the lining together of thee activated nucleotides through covalent phosphodiethster bonds to form two new polynucleotide strands.
DNA polymerase
199
Why is DNA replication known as **semi-conservative replication**?
Each of the daughter DNA molecules contain one of the original strands of DNA and a new one.
200
what proves semi-conservative replication of DNA?
Density gradient centrifugation
201
describe the experiment that proves semi-conservative replication of DNA.
- they ‘labelled’ the original DNA of bacteria by growing them on a medium of 15N (an isotope of nitrogen) for a single generation to replicate once.
- they then transferred the bacteria to a medium of 14N for a single generation to allow it to replicate once.
- to separate the different DNA types they centrifuge the extracted DNA in a solution.
- the lighter the DNA (14N), the nearer to the top of the centrifuge tube it collected. The heavier the DNA (15N), the nearer to the bottom of the centrifuge tube it collected.
202
describe the experiment that proves semi-conservative replication of DNA.
- they ‘labelled’ the original DNA of bacteria by growing them on a medium of 15N (an isotope of nitrogen) for a single generation to replicate once.
- they then transferred the bacteria to a medium of 14N for a single generation to allow it to replicate once.
- to separate the different DNA types they centrifuge the extracted DNA in a solution.
- the lighter the DNA (14N), the nearer to the top of the centrifuge tube it collected. The heavier the DNA (15N), the nearer to the bottom of the centrifuge tube it collected.
203
What is an enzyme inhibitor?
Any molecule that reduces or stops a reaction
204
What type of inhibitors are there?
Competitive
Non-competitive
205
How does a competitive inhibitor inhibit an enzyme?
Competes with the substrate as it fits into the active site of the enzyme, forming a barrier that prevents the formation of enzyme-substrate complexes
206
How does a non-competitive inhibitor inhibit an enzyme?
Binds to the allosteric site of the enzyme which causes a conformational change. This alters the shape of the enzyme’s active site so it’s not complementary with its substrate.
207
Non-competitive inhibitors have a ___________ inhibition effect.
Powerful
208
Competitive inhibitors have a _________ inhibition effect.
Weaker
209
Why do competitive inhibitors have a less powerful inhibition effect?
For every given substrate concentration the rate is lowered, but optimism rate of reaction is still reached.
210
Most competitive inhibitors bind _____________.
Reversibly
211
Most non competitive inhibitors bind _______________.
Permanently
212
Describe end-product inhibition.
A cell may only want a certain amount of a molecule being produced so one the products of may act as an inhibitor for another enzyme in the pathway, stopping the production of that molecule.
213
If the concentration of the final product is high, ______ inhibition will occur.
________ inhibition will lead to a decrease in the amount of end product being produced.
This is called a _______ feedback loop.
More
Greater
Negative
214
What does RNA stand for?
Ribonucleic acid
215
What is RNA made up of?
Nucleotides - ribose sugars attached to nitrogenous bases and phosphate groups.
216
What are the nitrogenous bases in RNA?
Adenine - **Uracil**
Cytosine - Guanine
217
RNA only has ____ polynucleotide strand.
One
218
What does mRNA stand for?
Messenger ribonucleic acid
219
what is the role of mRNA?
Carry protein information form the DNA in a cell’s nucleus to the cell’s cytoplasm.
Involved in protein synthesis
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What does tRNA stand for?
Transfer ribonucleic acid
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What is the role of tRNA?
- helps decode a mRNA sequence into a protein.
- brings amino acids to the ribosome for protein synthesis.
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What does rRNA stand for?
Ribosomal ribonucleic acid
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What is the role of rRNA?
- reads the order of amino acids and links amino acids together
- ensures the proper alignment of the mRNA and the ribosomes during protein synthesis and catalyses the formation of peptide bonds between two aligned amino acids during protein synthesis
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Give two reasons why DNA is stable.
- the phosphodiesther backbone protects the more chemically reactive organic bases inside the double helix.
- hydrogen binds link then organic base pairs forming bridges (rungs) between the phosphodiethster uprights. As there are 3 hydrogen bonds between cystine and guanine, the higher proportion of C-G pairing, the more stable the DNA molecule.
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How is DNA adapted to carry out its function?
- rarely mutates
- the two phosphodiethster strands are joined only with hydrogen bonds. This allows them to easily separate during DNA replication and protein synthesis
- the base pairs are within the helical cylinder of the deoxyribose-phosphate backbone meaning it is protected from being corrupted by outside chemical and physical forces.
- base painting leads to DNA brings able yo replicate and to transfer information as mRNA
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What is the function of DNA?
DNA is the hereditary material responsible for passing genetic information from cell to cell and generation.
