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AS AQA Biology > Nucleic Acids, ATP and Water > Flashcards

Nucleic Acids, ATP and Water Flashcards

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1
Q

What is the role of DNA?

A

Carries genetic information from one generation to the next

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2
Q

What are the best know nucleic acids?

A

Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)

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3
Q

What does mRNA do?

A

Copies the genetic information in DNA and takes it a ribosome

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4
Q

What are the polymers of nucleotides?

A

DNA and RNA

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5
Q

What are the 3 components of a nucleotide?

A
  • Phospahate group
  • Nitrogenous base (Cytosine, Guanine, Thymine, Uracil, Adenine)
  • Pentose sugar
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6
Q

What is the difference between ribose and deoxyribose?

A

Ribose has an OH group bound to carbon 2, Deoxyribose only has a H bound to carbon 2

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7
Q

What is the bond called between two nucleotides that have gone through a condensation reaction?

A

Phosphodiester bond

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8
Q

What type of bond is a phosphodiester bond?

A

It is a covalent bond that makes the sugar-phosphate “backbone” of the nucleic acid stable and strong

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9
Q

What direction are nucleotides added?

A

5’-3’ direction

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10
Q

What structure are DNA molecules in?

A

Helix structure

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11
Q

What is the purpose of 2 strands?

A

2 strands protect the information stored in the base sequence from radiation, free radicals, hydrolytic enzymes ect.. and they also allow semi-conservative replication

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12
Q

What makes a stable DNA molecule?

A

H bonds

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13
Q

What is the function of DNA?

A

To pass genetic information from one generation to the next

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14
Q

What provides genetic diversity within all living organisms?

A

The combination of base sequences is almost infinite

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15
Q

How is DNA adapted to carry out it’s function

A
  1. The sequence of the bases is variable. This is how information is stored in DNA
  2. DNA codes for amino acids
  3. Different bases code for different amino acids
  4. Long strands of DNA code for lots of different proteins
  5. mRNA is a comparatively shorter polynucleotide chain
  6. mRNA is a single stranded helix, mRNA constantly needs to be hydrolysed and rebuilt into different sequences
  7. mRNA is used to transfer genetic information from DNA to ribosomes
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16
Q

What does anti-parallel strands mean?

A

Two strands of DNA that run in opposite directions

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17
Q

What enzyme is involved in making the phosphodiester bond?

A

DNA Polymerase, it has a complimentary active site to the 5’ end of the molecule. Therefore it can only bind to the 3’ end of the primer/developing strand

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18
Q

mRNA -

A

Messenger RNA is single stranded, linear polynucleotide. Copies the DNA code and takes it to a ribosome to make protein

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19
Q

tRNA -

A

Transfer RNA is single stranded polynucleotide folded into a cloverleaf shape. It brings amino acids to the ribosome during protein synthesis

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20
Q

rRNA -

A

Ribosomal RNA is found is ribosomes along with protein

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21
Q

What did Griffith’s experiment designed to show?

A

It shows that DNA is the hereditary material

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22
Q

What was the first stage in Griffith’s experiment?

A

The first group of mice were injected with the “R” strain and lived

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23
Q

What was the second stage in Griffith’s experiment?

A

The second group of mice were injected with the “S” strain and died

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24
Q

What was the third stage in Griffith’s experiment?

A

The third group of mice were injected with heat killed “S” strain and lived

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25
Q

What was the fourth stage in Griffith’s experiment?

A

The fourth group of mice were injected with heat killed “S” strain and live “R” strain and died

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26
Q

What are the three possible explanations for the fourth group’s results?

A
  1. Experimental error - not all the S strain were killed eith heat
  2. The living “R” strain form had mutated into the harmful form. (Though this is extremely unlikely, as the experiment was repeated many times and the same results were obtained)
  3. The dead “S” strain has information about how to make the toxin, but as they are dead, they can’t. The “R” strain has no instructions but has the equipment needed to make the toxin. The information has been transferred from the harmful bacteria to the safe bacteria, which then produced the toxin
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27
Q

What further experiments had to be carried out for the third explanation for the possible reasons the fourth group died in Giffith’s experiment?

A

. The bacteria from the fourth experiment were collected
. Various substances were isolated and purified
. Each substance in turn was added to suspensions of living “R” strain bacteria to see if it could transform the “R” strain into the “S” strain
. The only substances that caused transformations was DNA
. When enzymes that breakdown DNA were added, no transformations were observed

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28
Q

What was Hershey and Chase’s experiment designed to show?

A

DNA is the hereditary material that is passed from generation to generation and not proteins

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29
Q

What did Hershey and Chase do to see if proteins are the hereditary material?

A

. S35 selectively labels the phage protein capsid. labelling proteins with radioactive sulfer allows the protein’s location to be monitored throughout the experiment
. The phages were allowed to infect the bacteria. The bacteria are then agitated to remove the phage capsids from the outside of the bacteria
. No S35 was found in the next generation, therefore no protein was passed on from the parent virus to the next generation of viruses

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30
Q

What did Hershey and Chase do to see if DNA is the hereditary material?

A

. Radioactive phosphorus P32 was used to label phosphate in the DNA, which is not found in proteins
. The phages were allowed to infect the bacteria. The bacteria are then agitated to remove the phage capsids from the outside of the bacteria
. P32 was found in the new generation of phage showing that DNA must be hereditary, proving DNA is passed from parents to offspring

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31
Q

What does semi-conservative replication do?

A

It ensures genetic information stays the same between generations of cells and allows daughter cells to produce the same proteins and therefore have the same characteristics and role as the parent cell

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32
Q

What is the first step in semi-conservative replication?

A

DNA helicase attaches and moves along the DNA molecule, and breaks the H bonds between complementary bases

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33
Q

What is the second step in semi-conservative replication?

A

The two strands separate and create a replication bubble. Each strand acts a s a template

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34
Q

What is the third step in semi-conservative replication?

A

Primase makes primers that bind to the template to keep the two strands separated and allow DNA polymerase to bind to the 3’ of the primer

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35
Q

What is the fourth step in semi-conservative replication?

A

New DNA nucleotides are attracted to exposed complimentary bases on template strands and base pairing occurs (A-t and C-G)

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36
Q

What is the fifth step in semi-conservative replication?

A

DNA polymerase now aligns and joins the DNA nucleotides together

37
Q

What is the sixth step in semi-conservative replication?

A

Through a condensation reaction forming phosphodiester bonds between new DNA nucleotides

38
Q

What is the seventh step in semi-conservative replication?

A

Semi-conservative replication ensures that each new DNA molecule contains an original and a new strand and is identical to the original DNA

39
Q

How many DNA polymerase enzymes are involved?

A

Two DNA polymerase enzymes work in opposite directions at the same time on each strand to make two new molecules of DNA

40
Q

What are Okazaki fragments?

A

The “leading strand” can be made continuously, whereas the opposite strand “lags” behind.
The “lagging strand” is made up in small fragments, called Okazkai fragments. These small fragments of DNA are later joined together using an enzyme called DNA Ligase

41
Q

Who discovered the structure of DNA?

A

Watson and Crick along with Franklin, their idea was the semi-conservative replication model

42
Q

What does the conservative model show?

A

The original strand of DNA is conserved. The new DNA strand is built up of new nucleotides. Of the two new DNA molecules, one strand contains the original material and the other is made of entirely new material

43
Q

What does the semi-conservative model show?

A

The DNA molecule is split into 2 strands, and each strand is replicated as a mirror image. Each new molecule would contain one strand of original material and one strand of new material

44
Q

What 3 things did Meselson and Stahl base their experiments on?

A
  1. All the DNA bases contain nitrogen
  2. Nitrogen has 2 isotopes: N14 which has fewer neutrons, and therefore “less dense”, N15 which has 1 more neutron, and is therefore “more dense”
  3. Bacteria will use nitrogen from their environments to make all of their new DNA nucleotides
45
Q

What did Meselson and Stahl control in their experiment?

A

They grew bacteria on a N14 medium
Therefore all the bacteria DNA contains is “less dense”
They broke open the cells and centrifuged the DNA in a caesium chloride solution to seperate molecules based on their density
This DNA formed 1 band that settled at the top of the tube

46
Q

What did Gen 0 show in the Mselson and Stahl experiment?

A

They grew bacteria on a medium containing only N15, therefore all of the bacteria had DNA that only contained more dense N15
They then broke open some cells and centrifuged the DNA
This DNA formed 1 band that settled at the bottom of the tube

47
Q

What did Gen 1 show in the Meselson and Stahl experiment?

A

They then took some of the original, Gen 0 bacteria grown in N15 and put them on a medium containing only N14. They then allowed the cells to replicate
They broke open some of the cells and centrifuged the DNA
This DNA formed 2 separate bands
1 band settled in the middle of the tube, the second band settled at the top of the tube

48
Q

What is ATP?

A

Adenine Triphosphate is made from: 1 nitrogen containing organic base (Adenine); 1 ribose sugar and 3 phospahte groups which are joined together through several condensation reactions

49
Q

What is ATP used for?

A

ATP is the main energy source in cells

50
Q

How does ATP store energy?

A

The bonds between the phosphates have low activation energy, the bonds are unstable and easily broken. When broken these bonds release energy. In living cells, it’s usually only the terminal phosphate that is removed

51
Q

What is the ATP equation?

A

ATP + H20 = ADP + Pi + E

52
Q

What enzyme is used in the hydrolysis of ATP?

A

ATPhydrolase (ATPase)

53
Q

What enzyme is used in the making of ATP?

A

ATPsynthase

54
Q

What are the 3 ways phosphorylation can occur?

A
  1. In chloryphyll containing plant cells using light energy (photophosphorylation)
  2. In plant and animal cells during aerobic respiration (oxidative phosphorylation)
  3. In plant and animal cells when phosphate groups are transferred to donor molecules (substrate level phosphorylation)
55
Q

Why is ATP considered an immediate energy source?

A

ATP can not be stored, unlike fats, carbs and glycogen. As well as this ATP is easily resynthesised and recycled so cells don’t require a lot of ATP

56
Q

Two reasons ATP is better as an immediate energy source than glucose is because…

A
  1. ATP releases less energy than one glucose molecule would. The energy is released in small, manageable quantities. This reduces the amount of heat released that would denature proteins and enzymes.
  2. The hydrolysis of ATP is a single step reaction that releases energy immediately. The oxidation of glucose has hundreds of stages, so releasing energy would take too long
57
Q

Where is the most mitochondria found?

A

The mitochondria constantly resynthesises ATP, so cells with a higher demand for energy (like the muscle cells) require more larger mitochondria

58
Q

Metabolic processes -

A

ATP provides the energy needed to make polymers from monomers (e.g. making proteins from amino acids or making glycogen from alpha glucose)

59
Q

Movement -

A

ATP provides the energy for muscle cintraction

60
Q

Active transport -

A

ATP provides energy to change the shape of the carrier proteins in the cell surface membrane. This allows molecules to move against their concentration gradient

61
Q

Secretion -

A

ATP is needed to form and move vesicles needed for the secretion of cell products

62
Q

Activation of molecules -

A

The inorganic phosphate released during hydrolysis of ATP can be used to phosphorylate other compounds to make them more reactive, lowering the activation energy needed for enzyme catalysed reactions (e.g. in the first stage of respiration, glycolysis glucose is phosphorylated to help split into 2 molecules)

63
Q

What are waters unusual properties due to?

A

Waters dipolar nature and it’s ability to readily form H bonds

64
Q

What charge does water have?

A

Overall water has no charge, however there is a slight negative charge on the oxygen and a slight positive charge on hydrogen. This gives one end of the molecule a negative charge and the other end a positive charge. Therefore water is a dipole

65
Q

What is the attractive force between the 2 oppositely charged poles called?

A

Hydrogen bonds

66
Q

Why is water called a “universal solvent”?

A

More molecules dissolve in water compared to any other liquid

67
Q

Why is water one of the major components in cytoplasm?

A

It allows chemicals and enzymes to dissolve and so metabolic reactions can occur

68
Q

What is cohesion?

A

When H bonds form between molecules of the same type. Water molecules form H bonds this is cohesion

69
Q

Surface Tension

A

H bonds allow surface tension to be created

70
Q

What is adhesion?

A

When H bonds form between different types of molecules

71
Q

Where is an example of cohesion and tension being used?

A

Cohesion and adhesion allow water molecules to form continuous columns in xylem vessels of plants

72
Q

What chemical reactions use/make water?

A

. Hydrolysis reactions and photosynthesis use water
. Condensation reactions and respiration produce water
. Water is a raw material in photosynthesis
. Chemicals need to dissolve in water so they can be used in enzyme controlled reactions

73
Q

Specific heat capacity -

A

Water has a high specific heat capacity that acts as a buffer to sudden temperature change. This makes aqua environments thermally stable. As organisms are mostly water it buffers them from temperature changes

74
Q

Latent heat (of Vaporisation of Water) -

A

Latent heat refers to the amount of thermal energy needed to evaporate 1g water.
H bonds require a lot of energy to be broken, additional energy is needed to evaporate water. This means lots of body heat is required to evaporate a small volume of sweat, which therefore lowers the internal temperature of the organism

75
Q

What happens to water when it freezes

A

it becomes less dense

76
Q

Water is not easily compressed so…

A

. Provides turgor in plants

. Provides support to the hydro skeleton in worms

77
Q

Water is transparent so…

A

. Plants underwater can photosynthesise

. Light can pass through the jelly like fluid that fills the eye

78
Q

What is an inorganic ion?

A

An ion that doesn’t contain carbon

79
Q

What is the function of acid (Hydrogen/H+)

A

Affect the acidity of solutions (pH)
H+ used in respiration to provide energy to make ATP
H+ used in photosynthesis to provide energy to make ATP

80
Q

What is the function of alkali (Hydroxide/OH)

A

To neutralise

81
Q

What is the function of iron (Fe2+/Fe3+)

A

Structural component of haemoglobin (binds 02)

82
Q

What is the function of Sodium (Na+)

A

Na+ used in the co-transport of glucose and amino acids from the lumen of the small intestine, into intestinal epithelial cells

83
Q

What is the function of potassium (K+)

A

Na+K+ are also used in nervous conduction

84
Q

What is the function of phosphate ((PO4)3-)

A

Components of phospholipids (make the cell surface and organelle membranes), DNA, RNA and ATP

85
Q

What is the function of nitrates (NO3-)

A

Taken up from the soil by plant roots. Sole source of nitrogen used in making amino acids and nucleotides

86
Q

What is the function of chloride (Cl-)

A

Used in regulating the water potential of the small intestine and maintaining the relative negative internal charge of a nerve cell

87
Q

Which bases have a single ring structure?

A

Pyrimidines - Cytosine, Thymine and Uracil

88
Q

Which bases have a double ring structure?

A

Purines - Guanine and Adenine

AS AQA Biology (14 decks)

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