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Biochemistry (3.1) Flashcards

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1
Q

Carbohydrates

What is the general formula for a monosaccharide?

A

(CH2O)n

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2
Q

Give 3 examples of a monosaccharide

A

Glucose
Fructose
Galactose

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3
Q

Give 3 examples of a disaccharide

A

Sucrose
Maltose
Lactose

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4
Q

Give 3 examples of a polysaccharide

A

Starch
Cellulose
Glycogen

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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)

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6
Q

How is a disaccharide formed?

A

Condensation reaction

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7
Q

Describe a condensation reaction.

A

Two monosaccharides join together and a water molecule is released.

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8
Q

What bond joins two monosaccharides when they make a disaccharide?

A

Glycosidic bond

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9
Q

What is another name for a glycosidic bond?

A

Alpha 1,4 bond

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10
Q

Glucose + glucose —-> ?

A

Maltose + water

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11
Q

Glucose + fructose —> ?

A

Sucrose + water

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12
Q

Galactose + glucose —> ?

A

Lacoste + water

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13
Q

What is the molecular formula for glucose?

A

C6H12O6

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14
Q

Define the term hydrolysis.

A

A larger molecule is broken down into smaller molecules using water

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15
Q

Define the term condensation.

A

Smaller molecules join together to make bigger molecules, a bond is formed and water is released.

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16
Q

What is a polysaccharide’s monomer?

A

A monosaccharide

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17
Q

Name 3 polysaccharides.

A

Starch
Cellulose
Glycogen

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18
Q

What type of cells contain starch?

A

Plant cells

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19
Q

How to plants ‘store’ starch?

A

In the form of starch grains

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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

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21
Q

What is a reducing sugar?

A

A sugar that donates electrons to another substance (reducing that substance).

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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

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23
Q

What is the process of testing for the presence of a reducing sugar?

A
  1. Add an equal volume of Benedict’s reagent to the liquid sample bring tested.
  2. Heat in a gently boiling water bath for 5 minutes.
    3.if a reducing sugar is present a brick red precipitate will form.
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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

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25
Q

What should you do to prove a sugar is non reducing after performing a Benedict’s reagent test with a blue result?

A
  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.
  4. If a non-reducing sugar was present in the original sample a brick red precipitate will form.
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26
Q

What are the two types of starch?

A

Amylose and amylopectin.

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27
Q

What type of bonds does amylopectin have?

A

Glycosidic

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28
Q

What ‘shape’ does amylopectin have?

A

Tree/brush like

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29
Q

What are the glucose monomers in amylose held together by?

A

Glycosidic bonds

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30
Q

How are the amylose polymer coils held into place?

A

Hydrogen bonds which form between hydroxyl groups

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31
Q

Is starch found in animal cells?

A

No only plant

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32
Q

How is starch well suited to its role of energy storage?

A

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

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33
Q

What is difference between the bonds in amylose and amylopectin?

A

Amylopectin has 1,4 and 1,6 glycosidic bonds whereas amylose has only 1,4 glycosidic bonds

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34
Q

In what type of organisms is glycogen formed?

A

Animals and bacteria

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35
Q

Two ways glycogen is different from starch

A

Shorter chains, more highly branched

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36
Q

Where is glycogen stored in animals?

A

Muscles and liver

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37
Q

Describe 4 ways in which the structure of glycogen suits its function

A

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.

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38
Q

What type of cells is cellulose found in?

A

Plant cells

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39
Q

What part of the plant cell contains large amounts of cellulose?

A

Cell wall

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40
Q

What is cellulose’s monomer

A

Beta glucose

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41
Q

What must happen for the glycosidic bonds to form between two adjacent beta glucose monomers?

A

Each molecule must rotate 180 degrees relative to the one beside it.

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42
Q

what type of bonds are there between the monomers in cellulose?

A

1,4 glycosidic bonds

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43
Q

What is the effect of the alternating beta glucose molecules in cellulose?

A

Makes cellulose very straight

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44
Q

What is the structure of the chains of beta glucose in cellulose?

A

Long and unbranched

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45
Q

How do microfibrils form?

A

Hydrogen bonds form cross-links between parallel chains of beta glucose

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46
Q

Why are microfibrils so strong?

A

There are large numbers of hydrogen bonds

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47
Q

How are fibres formed?

A

Microfibrils are arranged in parallel groups

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48
Q

How are fibres arranged in the cell wall?

A

Aligned in a criss-cross direction

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49
Q

How Is cellulose well suited for its function?

A

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

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50
Q

What are 3 types of lipids you must know about?

A

Triglycerides
Phospholipids
Waxes

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51
Q

How are lipids a source of energy?

A

When oxidised they produce energy. They release more energy than a carbohydrate

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52
Q

Why are lipids good for waterproofing?

A

They are insoluble.

Plants and insects have a waxy cuticle that conserve water.
Mammals produce an oily secretion from glands in the skin.

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53
Q

Why are lipids good insulators?

A

Fats are slow conductors of heat

Lipids can also insulate electricity eg in myelin sheath around nerve cells

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54
Q

Why are lipids good for protection?

A

Fat is stored round delicate organs eg kidneys

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55
Q

What is a triglyceride made of?

A

1 glycerol and 3 fatty acid molecules

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56
Q

What is the molecular formula for glycerol?

A

C3H8O3

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57
Q

What is the molecular formula for a fatty acid and what does the R stand for?

A

R-COOH

R stands for the hydrocarbon chain

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58
Q

What type of reaction forms a triglyceride?

A

Condensation

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59
Q

What molecules are released in a condensation reaction to form a triglyceride?

A

3 water molecules

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60
Q

How can you identify a saturated hydrocarbon?

A

No C=C bonds in the hydrocarbon chain

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61
Q

how can you identify an unsaturated hydrocarbon?

A

1 or more C=C bonds

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62
Q

Why is an unsaturated hydrocarbon liquid at room temperature?

A

The C=C bond/s causes the molecule to bend so it cannot pack together

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63
Q

What state of matter is a saturated hydrocarbon at room temperature?

A

Solid

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64
Q

What type of bond is formed in a triglyceride?

A

Ester bond

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65
Q

What does ATP stand for?

A

Adenosine Triphosphate

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66
Q

What is ATP?

A

An energy carrier/ chemical used in living organisms to transfer energy

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67
Q

What is the name of the base in ATP?

A

Adenine

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68
Q

What is the name of the 5 carbon sugar in ATP?

A

Ribose

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69
Q

What causes the terminal phosphate to be removed?

A

There are unstable bonds between phosphate groups meaning they have a low activation energy so the bonds are easily broken.

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70
Q

What type of reaction is ATP synthesis?

A

Condensation

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71
Q

What are the three energy sources for ATP synthesis?

A

Photo phosphorylation
Oxidative phosphorylation
Substrate-level phosphorylation

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72
Q

What is ATP synthesis catalysed by?

A

ATP synthase

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73
Q

What is the formula for ATP synthesis?

A

ADP + Pi ——> ATP + H20

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74
Q

What is ATP hydrolysis catalysed by?

A

ATP hydrolyse

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75
Q

What is the chemical equation for ATP hydrolysis?

A

ATP+ H20 ——> ADP + Pi + energy

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76
Q

What is an ion?

A

An atom or group of atoms that have an electrical charge

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77
Q

How are Ions formed?

A

Through loss or gain of electrons

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78
Q

What is an anion?

A

An ion with a negative charge

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79
Q

What is a cation?

A

An ion with a positive charge

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80
Q

What does an inorganic ion not contain?

A

Carbon

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81
Q

What is an organic molecule?

A

A molecule that contains carbon and hydrogen

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82
Q

What is the symbol for phosphate ion and its function?

A

PO4 3-
A component of DNA and ATP

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83
Q

What is the symbol for sodium ion and its function?

A

Na+
Involved in the co-transport of glucose and amino acids across cell surface membranes

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84
Q

What is the symbol for iron ion and what is its function?

A

Fe2+ or Fe3+
Forms part of haemoglobin

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85
Q

What is the symbol for hydrogen ion and what is its function ?

A

PH - a measure of the concentration of this ion
H+ (Ello. Remember you look beautiful x)

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86
Q

What is the difference between a phospholipid and a triglyceride?

A

One of the three fatty acids had been replaced by a phosphate group

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87
Q

What are the three parts of a phospholipid?

A

Phosphate head
Glycerol body
2 Fatty acid tails

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88
Q

What part of a phospholipid is hydrophilic?

A

Phosphate head

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89
Q

What part of the phospholipid is hydrophobic?

A

Fatty acid tails

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90
Q

What does hydrophilic mean?

A

Attracted to/interacts with water

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91
Q

What does hydrophobic mean?

A

Repels water but mixes readily with fat

92
Q

The head and tails of a phospholipid behave different, what is this described as?

A

Polar

93
Q

What do phospholipids form when placed on water?

A

A monolayer

94
Q

Why do phospholipids form a monolayer when placed on water?

A

The heads are hydrophilic therefore are attracted to the water, whereas the tails are hydrophilic therefore they repel water>

95
Q

When do phospholipids form a phospholipid bilayer?

A

When water is present on either side of the phospholipid e.g. cell membranes

96
Q

why do phospholipids form a phospholipid bilayer?

A

So the hydrophobic tails are not in contact with water

97
Q

What test do you perform when testing for lipids?

A

Emulsion test

98
Q

What indicates the presence of lipids in the emulsion test?

A

A milky emulsion

99
Q

How do you perform the emulsion test?

A
  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
Q

How would you perform calorimetry to find the concentration of an unknown glucose sample?

A

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
Q

How would you use a Büchner funnel to determine the unknown concentration of a glucose solution?

A

1) aim to make 5-6 different glucose solutions eg 0.2M, O.4M, 0.6M et
2) perform Benedict’s test on each one (heat with Benedict’s)
3) filter the precipitate, dry to a constant mass and weigh
4) plot data
5) take an unknown solution and do the Benedict’s test again.
6) read across the calibration curve to find the concentration of the unknown glucose solution

102
Q

How do you perform a serial dilution test to estimate the concentration of an unknown glucose solution?

A

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.

103
Q

What are the problems with using a serial dilution test to find out the concentration of an unknown glucose solution?

A

-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)

104
Q

Are monosaccharides insoluble or soluble?

A

Soluble

105
Q

Are polysaccharides soluble or insoluble?

A

Insoluble

106
Q

ATP is an ______ energy source for a cell.

A

Immediate

107
Q

Name two reasons why ATP is better than glucose.

A
  • 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).
108
Q

Name 3 uses of ATP.

A
  • active transport
  • cell division
  • biosynthesis
  • secretion
  • activation of other molecules
  • cell motility
  • muscle contraction
109
Q

Why is so much ATP produced?

A
  • 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.
110
Q

How des ATP effect the activation of other molecules?

A

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.

111
Q

What type of molecule is water?

A

Polar

112
Q

What is a polar molecule?

A

A molecule that has oppositely charged ends

113
Q

What charges do the oxygen and hydrogen have in water molecule?

A

Oxygen- slight negative
Hydrogen- slight positive

114
Q

What do the oxygen and hydrogen atoms in water have different charges?

A

Because of the uneven sharing of electrons in the covalent bonds between oxygen and hydrogen atoms

115
Q

Why does water have a strong cohesion?

A

There are hydrogen bonds between H20 molecules due t the oppositely charged poles that attract each other.

116
Q

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?

A

Cohesion

117
Q

Water has a relatively high heat capacity. What does this mean?

A

It means water cannot change temperature very easily.

118
Q

Why does water having a high heat capacity benefit aquatic and larger organisms?

A

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.

119
Q

Water has a relatively large latent heat of vaporisation. What does this mean?

A

It requires a lot of energy to change the state of H20 from a liquid to a gas.

120
Q

Why does water have a large latent heat of vaporisation?

A

The hydrogen bonds between water molecules make them different to separate.

121
Q

How does water’s large latent heat of vaporisation effect cooling systems of plants and animals?

A

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.

122
Q

Why is water a good solvent?

A

It readily dissolves other substances.
Ionic compounds dissolve in water because the ions are attracted to the charged ends of the water molecule.

123
Q

In what process is water used to split large molecules into smaller ones?

A

Hydrolysis

124
Q

What process is water needed for in plants?

A

Photosynthesis

125
Q

Water cannot be easily compressed. What benefit does this have?

A

It can provide internal support. For example in the hydrostatic skeletons of earthworms and jellyfish. Also for turgidly in plant cells.

126
Q

What is a protein’s monomer?

A

Amino acid

127
Q

How many amino acids are there?

A

20

128
Q

Give 3 examples of functions of a protein.

A
  • structural proteins
  • catalytic proteins
  • regulatory proteins
  • transport
  • Immunological
  • cell transport and recognition
129
Q

What is the chemically ‘basic group’ in an amino acid?

A

The amino group

130
Q

What is the R group in an amino acid?

A

The variable side chain

131
Q

What is the acidic group in an amino acid?

A

Carboxyl group

132
Q

How is a dipeptide formed?

A

The condensation reaction between two amino acid molecules

133
Q

How is a polypeptide formed?

A

A series of condensation reactions of amino acids that form an unbranched chain

134
Q

What is the amino group called at the end of a polypeptide chain?

A

N-terminus

135
Q

What is the name of the carboxylic acid group at the end of a polypeptide chain?

A

C-terminus

136
Q

What bonds join amino acids in the primary structure of a protein?

A

Peptide bonds

137
Q

Describe the primary structure of a protein

A

The specific order of amino acids in a protein.

138
Q

Describe the secondary structure in a protein.

A

The rotation or twisting of a polypeptide chain into a repeating pattern e.g alpha helix or beta pleated sheet.

139
Q

What are the bonds in the secondary structure of a protein?

A

Hydrogen bonds between peptide bonds.

140
Q

Describe the tertiary structure of a protein.

A

The overall 3D structure of a polypeptide as the result of interchain reactions between R-groups.

141
Q

What bonds are there in the tertiary structure of a protein?

A

Hydrogen bonds, ionic bonds, and disulphide bridges.

142
Q

Describe the quaternary structure of a protein.

A

Linking together of more than one polypeptide chain.

143
Q

Is the quaternary structure present in all proteins?

A

No

144
Q

What bonds are in the quaternary structure of a protein?

A

Any

(Peptide, hydrogen, ionic, disulphide bridges)

145
Q

What are enzymes?

A

Biological catalysts.

146
Q

Why are enzymes biological catalysts?

A

They lower the activation energy in a reaction by providing an alternate reaction pathway.

Found in living organisms.

Not used up in reactions.

147
Q

What are enzymes made of?

A

Proteins

148
Q

What is an enzymes monomer?

A

Amino acid

149
Q

What is an intracellularly enzyme?

A

An enzyme that works inside the cell e.g. in the cytoplasm

150
Q

What is an extracellularly enzyme?

A

Enzymes that are released from a cell.

151
Q

What is an anabolic enzyme?

A

An enzyme that builds molecules up.

152
Q

What is a catabolic enzyme?

A

An enzyme that breaks down molecules.

153
Q

What do the active site and substrate have to be?

A

Complimentary

154
Q

What is it called when the substrate ‘locks’ into the enzyme?

A

An enzyme-substrate complex

155
Q

What is different about the products when they leave the enzyme’s active site?

A

They are no longer complimentary to the enzyme.

156
Q

The ____ of an enzyme determines its function.

A

Shape

157
Q

What is activation energy?

A

The minimum amount of every needed to start a reaction.

158
Q

What does an enzyme do to the activation energy in a reaction?

A

It lowers it

159
Q

What do enzymes do to the rate of a reaction?

A

Increase the rate of reaction.

160
Q

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?

A

The reactants start with the same amount of energy and the products end with the Same amount of energy.

161
Q

How does the induced fit enzyme model differ from the lock and key model?

A

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.

162
Q

What is the changed active site shape called?

A

The functional active site

163
Q

Does the active site turn to its original shape when the products leave (according to the induced fit model)?

A

Yes it relaxes to its original shape and is free to accept another substrate molecule.

164
Q

What happens to the bonds when the substrate locks into an enzyme’s active site?

A

The bonds weaken a when the active site moulds to the shape of the substrate it puts the substrate molecule under stress.

165
Q

How does an enzyme make a reaction between substrates more likely to happen?

A

It brings the substrate molecules closer together and in the correct orientation making it easier and more probable to occur

166
Q

How do enzymes lower the activation energy?

A

They provide an alternative reaction pathway

167
Q

How does an enzyme lower the activation energy?

A

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.

168
Q

What would happen if we didn’t have enzymes?

A

Reactions would occur too slowly for us to stay alive.

169
Q

Which factors affect the rate of an enzyme controlled reaction?

A

Temperature
PH
Substrate concentration
Enzyme concentration

170
Q

Explain how temperature affects the rate of an enzyme controlled reaction.

A

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)

171
Q

What is PH a measure of?

A

The concentration of hydrogen ions in a solution.

172
Q

How do you Calculate PH?

A

PH= -log10[H+]

173
Q

Is PH is increased or decreased rate of reaction ______.

A

Falls

174
Q

How does PH affect the rate of an enzyme controlled reaction?

A

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.

175
Q

Describe the effect of enzyme concentration on the rate of an enzyme controlled reaction.

A

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.

176
Q

Describe the effect of substrate concentration on an enzyme controlled reaction.

A

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.

177
Q

What does DNA stand for?

A

Deoxyribose nucleic acid

178
Q

Nucleic acid is a _______. It’s monomers are _______.

A

Polymer
Nucleotides

179
Q

What 3 components is a nucleotide made up of?

A

Deoxyribose sugar (a 5 carbon sugar - Pentose)
A phosphate group (which has a negative charge)
An organic, nitrogenous base (A,T,C,G)

180
Q

Bases C and T are a single ring structure called ____________.

A

Pyrimidines

181
Q

Bases A and G are double ring structures called ______.

A

Purines

182
Q

How to the deoxyribose sugar, phosphate and base form a mononucleotide?

A

Condensation reaction

183
Q

What is the name of the bond formed between the sugar and phosphate group in a nucleotide?

A

Phosphodiesthter (a strong covalent bond)

184
Q

What bonds form between the bases in DNA?

A

Hydrogen

185
Q

CONDENSATION
Nucleotide + Nucleotide ————————> ?

A

Dinucleotide + water

186
Q

What does base A stand for?

A

Adenine

187
Q

What does base T stand for?

A

Thymine

188
Q

What does base C stand for?

A

Cytosine

189
Q

What does base G stand for?

A

Guanine

190
Q

What is Cargaff’s rule of base pairing?

A

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.

191
Q

Why will a purine always pair with a pryimidine?

A

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’.

192
Q

Viral DNA has an irregular number of bases, therefore it is ______ ___________ and has no base pairs.

A

Single stranded

193
Q

W_____________ and C_______ worked out the exact structure of DNA in 1953.

A

Watson and Crick

194
Q

Why are the polynucleotide strands in DNA described as anti-parallel?

A

They run in opposite directions

195
Q

Why are the polynucleotide strands in DNA described as anti-parallel?

A

They run in opposite directions

196
Q

The alternating sugar and phosphate groups are joined together by phosphoethster bonds. This forms the________.

A

Sugar-phosphate backbone

197
Q

Describe the process of semi conservative DNA replication.

A
  • 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.
198
Q

The action of the enzyme _______ results in the unwinding and separation of the two polynucleotide strands.

A

Helicase

199
Q

The enzyme ____ __________ catalyses the lining together of thee activated nucleotides through covalent phosphodiethster bonds to form two new polynucleotide strands.

A

DNA polymerase

200
Q

Why is DNA replication known as semi-conservative replication?

A

Each of the daughter DNA molecules contain one of the original strands of DNA and a new one.

201
Q

what proves semi-conservative replication of DNA?

A

Density gradient centrifugation

202
Q

describe the experiment that proves semi-conservative replication of DNA.

A
  • 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
Q

describe the experiment that proves semi-conservative replication of DNA.

A
  • 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.
204
Q

What is an enzyme inhibitor?

A

Any molecule that reduces or stops a reaction

205
Q

What type of inhibitors are there?

A

Competitive
Non-competitive

206
Q

How does a competitive inhibitor inhibit an enzyme?

A

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

207
Q

How does a non-competitive inhibitor inhibit an enzyme?

A

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.

208
Q

Non-competitive inhibitors have a ___________ inhibition effect.

A

Powerful

209
Q

Competitive inhibitors have a _________ inhibition effect.

A

Weaker

210
Q

Why do competitive inhibitors have a less powerful inhibition effect?

A

For every given substrate concentration the rate is lowered, but optimism rate of reaction is still reached.

211
Q

Most competitive inhibitors bind _____________.

A

Reversibly

212
Q

Most non competitive inhibitors bind _______________.

A

Permanently

213
Q

Describe end-product inhibition.

A

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.

214
Q

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.

A

More
Greater
Negative

215
Q

What does RNA stand for?

A

Ribonucleic acid

216
Q

What is RNA made up of?

A

Nucleotides - ribose sugars attached to nitrogenous bases and phosphate groups.

217
Q

What are the nitrogenous bases in RNA?

A

Adenine - Uracil
Cytosine - Guanine

218
Q

RNA only has ____ polynucleotide strand.

A

One

219
Q

What does mRNA stand for?

A

Messenger ribonucleic acid

220
Q

what is the role of mRNA?

A

Carry protein information form the DNA in a cell’s nucleus to the cell’s cytoplasm.
Involved in protein synthesis

221
Q

What does tRNA stand for?

A

Transfer ribonucleic acid

222
Q

What is the role of tRNA?

A
  • helps decode a mRNA sequence into a protein.
  • brings amino acids to the ribosome for protein synthesis.
223
Q

What does rRNA stand for?

A

Ribosomal ribonucleic acid

224
Q

What is the role of rRNA?

A
  • 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
225
Q

Give two reasons why DNA is stable.

A
  • 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.
226
Q

How is DNA adapted to carry out its function?

A
  • 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
227
Q

What is the function of DNA?

A

DNA is the hereditary material responsible for passing genetic information from cell to cell and generation.

Biology (7 decks)

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