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biology > 2.3 - nucleotides and nucleic acids * > Flashcards

2.3 - nucleotides and nucleic acids * Flashcards

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1
Q

what is ATP?

A
  • adenosine triphosphate
  • immediate source of energy for biological processes
  • constant steady supply of ATP required for metabolic reactions in cells to continually occur
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2
Q

what is the structure of ATP?

A
  • nitrogenous base of adenine
  • ribose (pentose sugar)
  • three inorganic phosphate groups
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3
Q

how is ATP made?

A
  • during respiration
  • made from adenosine diphosphate (ADP), by the addition of an inorganic phosphate via a condensation reaction and using the enzyme ATP synthase
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4
Q

how/what can ATP be broken down into?

A
  • hydrolysed by hydrolysis reaction and the enzyme ATP hydrolase
  • ATP + H2O -> ADP + Pi
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5
Q

how is ATP an IMMEDIATE energy source?

A
  • bonds between the inorganic phosphate groups are high energy
  • by breaking one of these bonds, a small amount of energy is released to the surroundings, which can be used in chemical reactions
  • only one bond has to be hydrolysed to release energy, and as ATP cannot be stored, this occurs immediately
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6
Q

what is phosphorylation and how does it happen?

A
  • ATP transferring energy to other compounds
  • inorganic phosphate released during the hydrolysis of ATP is bonded onto completely different compounds to make them more reactive
  • happens to glucose at the start of respiration
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7
Q

five properties of ATP?

A
  1. releases energy in small amounts
  2. small and soluble
  3. only one bond needs to be broken to release energy
  4. can transfer energy to another molecule
  5. ATP cannot leave the cell
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8
Q

why is it an advantage that ATP releases energy in small, manageable amounts?

A
  • no energy is wasted
  • cells don’t overheat from wasted heat energy
  • cells are less likely to run out of resources
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9
Q

why is it an advantage that ATP is small and soluble?

A
  • easily transported around cell
  • can move around the cytoplasm with ease to provide energy for chemical reactions within the cell
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10
Q

why is it an advantage that in ATP only one bond needs to broken to release energy?

A
  • energy release is immediate
  • glucose would need several bonds to be broken down to release all its energy
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11
Q

why is it an advantage that ATP can transfer energy to another molecule?

A
  • ATP can enable phosphorylation making other compounds more reactive
  • glucose can’t do this as it does not contain phosphate groups
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12
Q

why is it an advantage that ATP cannot leave the cell?

A
  • all cells have a constant supply of ATP or ADP + Pi but a cell can run out of glucose
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13
Q

what is RNA?

A
  • polymer of a nucleotide formed of a ribose, a nitrogenous base, and a phosphate group
  • the nitrogenous bases in RNA are adenine, guanine, cytosine, and uracil as RNA has uracil instead of thymine
  • relatively short polynucleotide chain and is single stranded
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14
Q

what is the function of RNA?

A
  • to copy and transfer the genetic code from DNA in the nucleus to the ribosomes
  • some RNA is also combined with proteins to create ribosomes
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15
Q

what are the three types of RNA?

A

mRNA, tRNA and rRNA

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16
Q

describe mRNA and its production?

A
  • messenger RNA
  • copy of gene from DNA
  • created in the nucleus and then leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm
  • as DNA is too large to leave the nucleus and would be at risk of being damaged by enzymes, so would destroy the genetic code
  • every 3 bases in the sequence code for a specific amino acid
  • 3 bases= 1 codon
17
Q

what is a polynucleotide and how is it formed?

A
  • polymer of nucleotides
  • created via condensation reactions between the deoxyribose sugar and the phosphate group, creating a phosphodiester bond
  • phosphodiester bonds are strong covalent bonds and therefore help ensure that the genetic code is not broken down
  • has a sugar-phosphate ‘backbone’ which is describing the strong covalent bonds between the sugar and phosphate groups that hold the polymer together
18
Q

describe the structure of a DNA polymer?

A
  • polymer occurs in pairs, and these pairs are joined together by hydrogen bonds between the bases forming double helix structure as two chains twist
  • Adenine and thymine form 2 hydrogen bonds, but cytosine and guanine can form 3 hydrogen bonds
19
Q

how does structure of DNA relate to its function?

A
  • stable structure due to sugar-phosphate backbone (covalent bonds) and the double helix
  • double stranded so replication can occur using one strand as a template
  • weak hydrogen bonds for easy unzipping of the two strands in a double helix during replication
  • large molecule that carries lots of information
  • complementary base pairing allows identical copies to be made
20
Q

what is tRNA and its function?

A
  • transfer RNA
  • single stranded but folded to create a shape that looks like a cloverleaf, held together by hydrogen bonds
  • function is to attach to one of the 20 amino acids and transfer this amino acid to the ribosome to create the polypeptide chain
21
Q

what is function of DNA?

A

codes for the sequence of amino acids in the primary structure of a protein, which in turn determines the final 3D structure and function of a protein.

22
Q

describe structure of a DNA nucleotide?

A
  • deoxyribose (pentose sugar), a nitrogenous base, and one phosphate group
  • the nitrogenous base can be guanine, cytosine, adenine, or thymine
  • these bases are classified as either purines or pyrimidines, depending on whether the base is a single or double-ring structure
  • adenine and guanine are both double-ring so are purines
  • thymine and cytosine are both single-ring structures so are pyrimidines
23
Q

what type is DNA replication?

A

semi-conservative replication

24
Q

what is the first step of DNA replication?

A

the double helix unwinds and the hydrogen bonds between the complementary
bases break using DNA helicase (enzyme) thus separating the two strands of DNA

25
Q

2nd step of DNA replication?

A

both strands are used as
templates and complementary base pairing occurs between the template strands and free floating DNA nucleotides

26
Q

3rd step of DNA replication?

A

adjacent nucleotides are
joined by phosphodiester bonds formed in condensation reactions
using DNA polymerase

27
Q

what is the genetic code?

A
  • consists of triplets of bases, each triplet of bases codes for a particular amino acids and is known as a codon
  • the amino
    acids are then joined together by peptide bonds and form a polypeptide chain
  • a gene is a sequence of bases on a DNA molecule coding for a sequence of amino acids in a
    polypeptide chain
28
Q

what are introns and exons?

A
  • introns are the non-coding sections of DNA
  • exons are the coding regions of DNA
29
Q

describe three features of the genetic code?

A
  • non-overlapping meaning that each triplet is only read once and
    triplets don’t share any bases
  • degenerate meaning that more than one triplet codes for the same amino acids, which reduces the phenotypic effect of mutations
  • contains start and stop codons which either start or stop protein synthesis
30
Q

what is transcription?

A
  • DNA strand is transcribed into mRNA
  • a molecule of mRNA is made in the nucleus
31
Q

what are the 4 steps of transcription?

A
  • the hydrogen bonds between the complementary bases break and the DNA uncoils
    thus separating the two strands
  • one of the DNA strands is used as a template by RNA polymerase to make the
    mRNA molecule, the DNA template is called the antisense strand
  • free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds made by RNA polymerase, forming a single stranded molecule of mRNA
  • mRNA then moves out of the nucleus through a pore and attaches to a ribosome in
    the cytoplasm which is the site of translation
32
Q

what is translation?

A

process during which the amino acids are assembled together to form a polypeptide chain/protein

33
Q

what are the four steps of translation?

A
  • mRNA attaches to a ribosome and transfer RNA collects amino acids from cytoplasm and carries them to the ribosome
  • tRNA attaches itself to mRNA by complementary base pairing – two molecules attach to mRNA at a time
  • the amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach themselves from the amino acids, leaving them behind
  • this process is repeated, leading to the formation of a polypeptide chain until a stop codon is reached on mRNA and ends the process of protein synthesis

biology (9 decks)

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