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Biology Alevel > Nucleic Acids (biological Molecules) > Flashcards

Nucleic Acids (biological Molecules) Flashcards

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1
Q

What charge does a water molecule obtain

A

Although the molecule has no overall charge the oxygen atom has a slight negative charge while the hydrogen atoms have a slight positive one

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2
Q

Why is water dipolar

A

The water molecule has both positive and negative poles

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3
Q

Why is waters specific heat capacity higher than expected

A

Because water molecules stick together it takes more energy to separate them

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4
Q

How does water act as a buffer and how does this help organisms

A

Water acts as a buffer against sudden temperature variations as it has such a high specific heat capacity and therefore high boiling point. Making the aquatic environment a temperature - stable one. It also buffers them against sudden temperature changes in terrestrial enviroments

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5
Q

Why is it good for humans that waters latent heat of vaporisation is high

A

Evaporation of water such as sweat needs a lot of energy and therefore is very effective in cooling mammals as we use our body heat to evaporate the water (losing heat and energy to cool down)

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6
Q

what is an organic ion

A

ions that contain atleast one carbon to hydrogen bond and contain carbon

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7
Q

what is an inorganic ion

A

charged molecules that do not contain carbon-hydrogen bonds

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8
Q

how does the concentration of hydrogen ions affect PH

A

the greater concentration of hydrogen ions , the lower the PH and the lower the concentration of hydrogen ions , the higher the Ph

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9
Q

how does this make the concentration of hydrogen important

A

this makes the concentration of h+ ions very important for enzyme - controlled reactions(7.4 is average enzyme ph)

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10
Q

how can abnormal levels of hydrogen ions affect enzymes

A

can interact with the side chains of amino acids and change the secondary and tertiary structures.

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11
Q

where do inorganic ions occur

A

inorganic ions occur in solution in the cytoplasm and bodily fluids of organisms. the concentration of certain ions can fluctuate and can be used in cell signalling and neuronal transmission

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12
Q

what is the role of sodium(na+) ions

A

sodium is the major extraceullular cation in animal cells. they are important in the transport of glucose and amino acids across plasma membranes. they are also involved in transmission of nerve impulses and in fluid and electrolyte balance.

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13
Q

what do sodium ions do in plants

A

in plants na + ions are involved in maintaining cell turgor and in opening and closing stomata

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14
Q

what are the main roles of hydrogen ions

A

they are important in determining the PH of solutions and therefore the functioning of enzymes. they can also establish trans - membrane electrochemical gradients which can be used to generate ATP

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15
Q

what is the role of calcium (ca2+) ions

A

component of teeth and bone . and is involved in muscle contraction , blood clotting , activation of some enzymes and cell signalling

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16
Q

in plants what does calcium do

A

in plants calcium is a component of the cell wall

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17
Q

predict the biological consequences of inadequate levels of calcium in the diet

A

weak bones and teeth , impaired blood clotting and muscular weakness

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18
Q

what feature of inorganic ions structure enables them to be involved in acid - base regulation

A

they can accept or donate protons

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19
Q

which inorganic ions are involved in acid - base regulation

A

HCO3- , CL-, OH-,NH4+,H+

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20
Q

what is the role of nitrate (NO3-) ions

A

they are an important souce of nitrogen for plants . nitrogen is a component of amino acids and nucleotides.

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21
Q

how do plants obtain nitrate ions

A

they obtain their nitrogen by eating other organisms. they get their nitrogen from proteins made in plants or in other animals

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22
Q

what is the role of iron ions

A

found in haemoglobin where they play a role in the transport of oxygen . iron ions are also essential as they are involved in the transfer of electrons during respirtation and photosynthesis.

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23
Q

what is the role of phosphate ions

A

phosphate ions form a structural role in DNA and a role in storing energy in ATP molecules

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24
Q

What is the monomer of a nucleic acid

A

Nucleotide

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25
Q

What is a gene

A

A short sequence of bases which codes for a specific protein

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26
Q

What is a genome

A

All the genes in an organism

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27
Q

How is dna stored in the nucleus of cells

A

Chromosomes

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28
Q

What does dna stand for

A

Deoxyribonucleic acid

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29
Q

What is the shape of DNA

A

double helix

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30
Q

Who discovered the structure of DNA

A

James Watson and Francis crick in the 1950s

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31
Q

What is dna

A

A long chain of repeated units called nucleotides therefore it can be referred to as a polymer

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32
Q

What are the two long strands in dna called

A

Sugar phosphate backbone

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33
Q

What is the role of the sugar phosphate backbone

A

Helps hold the bases in the middle of the DNA molecule

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34
Q

What does a DNA nucleotide consist of

A

Phosphate, base and sugar( deoxyribose pentose sugar)

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35
Q

What does a nucleotide base always contain

A

Nitrogen

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36
Q

How is a nucleotide formed

A

Vía a condensation reaction which forms an ester bond between the phosphate and sugar (h20 released) and a glycosidic bond between the sugar and base (h20 released)

37
Q

How many hydrogen bonds between a and T bases

A

2

38
Q

How many hydrogen bonds between c and G bases?

A

3

39
Q

How are the nucleotides arranged in a DNA molecule?

A

They run anti parallel

40
Q

When the sugar of one nucleotide joins two, the phosphate of another nucleotide, what bond is formed

A

Phosphodiester bond

41
Q

Why does DNA from a double helix structure?

A

Because of the specific hydrogen bonds between the bases and because bases are hydrophobic, where is the phosphate groups are hydrophilic

42
Q

What is RNA?

A

RNA is a type of nucleic acid called ribonucleic acid.

43
Q

How does RNA differ from DNA?

A

RNA differs from DNA because rna is single stranded, whereas DNA has two strands. Additionally, DNA is much longer than RNA .RNA has a sugar called ribose, whereas DNA has a sugar called deoxy ribose. RNA has the base uracil. Where is DNA. Has the base thymine .

44
Q

How is DNA stable?

A

DNA is stable because the phosphodiester backbone protects the more chemically reactive organic bases inside the double helix. Additionally, hydrogen bonds link the organic base pairs forming bridges between the phosphodiester uprights as there are three hydrogen bonds between cytosine and guanine the higher the proportion of c - G pairings, the more stable, the DNA molecule.

45
Q

How is DNA adapted to carry out its functions

A

It is a very stable structure which normally passes from generation to generation without significant change. Most mutations are repaired, so persistent mutations are rare.

It’s two separate strands are joined only with hydrogen bonds which allow them to separate during DNA replication and protein synthesis

It is an extremely large molecule and therefore carries an immense amount of genetic information

By having the base pairs within the helical cylinder of the deoxy, ribose, phosphate backbone, the genetic information is to some extent, protected from being corrupted by outside, chemical and physical forces

Base pairing leads to DNA being able to replicate, and to transfer information as mRNA

46
Q

when does a dna moleule need to replicate

A

before a cell divides during mitosis and meiosis , this is when a cell divides the two daughter cells will contain the correct amount of genetic material - genetially identical

47
Q

what is the first step in DNA replication

A

the origional dna molecule unwinds

48
Q

what is the 2nd step in dna replication

A

dna helicase breaks the hydrogen bonds and causes the 2 strands of dna to seperate

49
Q

what is the 3rd step in dna replication

A

free nucleotides in the nucleoplasm are attracted to their complemetary base pairs

50
Q

what is the fourth step in dna replication

A

the strong sugar phosphate backbone is re joined by dna polymerase which forms a phosphodiester bond between the sugar and phosphate of two nucleotides

51
Q

what is step 5 in dna replication

A

this forms 2 identical strands of dna

52
Q

what is step 6 in dna replication

A

because the strands each contain half of the origional material it is each called the semi conservative method of replication

53
Q

where is energy released from

A

mitocondria

54
Q

what process releases the most energy

A

respiration

55
Q

what is needed in this process

A

oxgen and glucose

56
Q

what is energy used for in living things?

A

muscle contraction , maintaining body temperature , chemical reactions ( condensation for example)

57
Q

what is the structure of ATP

A

adenine molecule , ribose molecule , and 3 phosphate groups

58
Q

what does ATP stand for

A

adenosine tri phosphate because the adenine and ribose together can be called adenosine

59
Q

what is ATP

A

atp is a nucleotide

60
Q

why is
ATP a phosphorylated macromolecule

A

it has three phosphate groups

61
Q

how is atp an immediate energy source

A

it has unstable bonds between the 2nd and 3rd phosphate which means it has a low activation energy to break. so this bond breaks to release energy

62
Q

how is ATP recylcable

A

the bond is constantly breaking and reforming to release energy. it is not used up

63
Q

what enzyme is needed for the hydrolysis reaction of atp

A

ATP hydrolase ( this is found in cell membranes and pretty much everywhere)

64
Q

what is left after the hydrolysis reaction of ATP

A

adenosine di phosphate and a phosphate ingorganic ion

65
Q

what reaction joins back the inogranic ion and ADP

A

condensation reaction

66
Q

what enzyme is needed for the condensation reaction of ADP

A

atp synthase (atpase)
and energy and the phosphate

67
Q

what is the benefit that ATP releases a small but sufficient amount of energy from the complete hydrolysis of ATP

A

this is enough energy to drive important metabolic reactions while keeping energy wastage low

68
Q

What is the benefit that ATP can be recycled

A

The breakdown of ATP is a reversible reaction so can be reformed from ADP and Pi so can be used elsewhere

68
Q

what is the benefit that ATP exists as a stable molecule

A

It doesn’t break down unless a catalyst (ATPase) is present so energy won’t be wasted

69
Q

What is the benefit that the hydrolysis of ATP is quick and easy

A

It allows cells to respond to a sudden increase in energy demand

70
Q

What is the benefit that ATP is soluble and moves easily within cells

A

Can transport energy to different areas of the cell

71
Q

What is the benefit that ATP forms phosphorylated intermediates

A

This can make metabolites more reactive and lower the activation energy needed for a reaction

72
Q

What’s an example of a metabolic process that atp is used for

A

Cell division and active transport

73
Q

who proposed the DNA models

A

watson and crick

74
Q

who did the DNA experiment

A

meselson and stahl

75
Q

what were the methods of dna replication proposed

A

semi conservative , conservative and fragmented .

76
Q

what is the semi conservative method of dna replication

A

each new synthesised strand is paired with half the origional

77
Q

what is the conservative method of dna replication

A

two strands , 1 origional and 1 new synthesised strand

78
Q

what is the fragmented method of dna replication

A

sections of origional and sections of new synthesised stranf

79
Q

what was the key thing watson and crick provided that enabled the experiment

A

the discovery of DNAs structure by watson and crick provided evidence that complementary base pairing was key to dnas ability to replicate

80
Q

which is the most abundant nitrogen isotope in bases

A

N14 so we assume all DNA bases will contain N14.

81
Q

what is a centrifuge

A

seperates substances out by mass

82
Q

what is the method meleson and stahl did

A

first control 1 is made by E coli bacteria grown in a solution of N14 bases. then control 2 , E.coli bacteria is grown in a solution of N15 and left to replicate a few times . the N15 will fully incorporate into the bases.
first experiment - E. coli bacteria with N15 incorporated into the bases are put in N14 medium . it is left to replicate once and the DNA is extracted and put into a centrifuge . a medium band pattern is observed as it is made of half the origional (n!%) and the new (N14) strand
2nd experiment - bacteria from first generation containing half the N15 bases and half N14 bases are put into a solution of N14 and left to replicate a second time . the dna is then extracted and put into a centrifuge . a medium band and light band will be observed . some new strands will contain all light bases and some will contain both

83
Q

which band shows its semi conservative

A

the medium band

84
Q

Describe and explain how the structure of DNA results in accurate replication

A

Weak hydrogen bonds allows strands to separate , two strands therefore semi - conservative replication is possible,

85
Q

Why do humans release sm ATP per day

A

ATP cannot be stored

86
Q

what base does atp contain

A

adenine

87
Q

Use your knowledge of enzyme action and DNA replication to explain why new nucleotides can only be added in a 5’ to 3’ direction.

A

dna polymerase is only complementary to 5’ side as dna strands are complementary

88
Q

what do the single DNA strands do

A

determinr the order of bases / nucleotides

Biology Alevel (18 decks)

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