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biology > NUCLEIC ACIDS > Flashcards

NUCLEIC ACIDS Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Name the 2 important information carrying molecules

A

. deoxyribonucleic acid - DNA
. Ribonucleic acid - RNA

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2
Q

what does DNA and RNA do ?

A

DNA holds genetic material and RNA transfers genetic material from the DNA to the ribosomes.

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3
Q

what are ribosomes made from ?

A

RNA and Proteins

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4
Q

explain what DNA and RNA are made of as they are polymers of nucleotides

A

each nucleotide is formed from a pentose sugar , a nitrogen-containing organic base and a phosphate group.

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5
Q

what are the components of a DNA molecule ?

A

a deoxyribose , a phosphate group and one of the organic bases , adenine, thymine , guanine and cytosine.

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6
Q

what components are a RNA molecule made of ?

A

a ribose , a phosphate group and one of the organic bases , adenine , uracil, guanine and cytosine.

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7
Q

In RNA what is the organic base thymine replaced with ?

A

Uracil.

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8
Q

what is a DNA molecule ?

A

a DNA molecule is a double helix with two polynucleotide chains held together by hydrogen bonds between the complementary base pairs.

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9
Q

explain the complementary base pairing between the organic bases

A

in DNA :
. adenine always pairs with thymine and are bonded together by 2 hydrogen bonds
.guanine always pairs cytosine and are bonded together by 3 hydrogen bonds.

> in RNA : thymine is replaced with uracil and uracil and adenine are complementary to each other.

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10
Q

name the structures of the organic bases

A

. adenine & Guanine > have a purine structure ( a pentagon and a hexagon stuck together)
. thymine/uracil & cytosine > have a pyrimidine structure ( a hexagon shape)

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11
Q

what are bases held together by ?

A

they are held together by weak hydrogen bonds which holds the two stands of DNA together and guanine and cytosine contain more hydrogen bonds so are more stable.

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12
Q

explain the structure of RNA

A

> it is a ribose and their are two types of RNA , TRNA (Transfer RNA) and MRNA (messenger RNA).
has oxygen and hydrogen on second carbon
single stranded
smaller than DNA
contain no hydrogen bonds.
thymine is replaced with uracil
short polynucleotide chain

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13
Q

explain the structure of DNA

A

> the sugar is a deoxyribose
double stranded
contain hydrogen bonds

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14
Q

what is ATP made of ?

A

ATP is a nucleotide derivative and is formed from a ribose , a molecule of adenine and 3 phosphate groups.
> energy is stored in the bonds between the phosphate groups.

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15
Q

what occurs in the hydrolysis of ATP ?

A

in the hydrolysis of ATP energy is released to form ADP and Pi and the bonds between the phosphate groups store energy and that is released. The hydrolysis of ATP is hydrolysed by ATP hydrolase.

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16
Q

what occurs in the condensation to form ATP ?

A

condensation of ADP and inorganic phosphate ( pi) is catalysed by ATP synthase which produces ATP during photosynthesis and respiration.

16
Q

what does the inorganic phosphate in ATP do ?

A

it can be used to phosphorylate other compounds , making them more reactive .

17
Q

explain the properties of ATP

A

> ATP is an immediate source of energy and it is more desirable to use than glucose as ATP can be broken down in a single step to release energy.
ATP is not stored in large quantities and can be reformed from ADP in seconds
ATP is used in a variety of ways which need energy such as metabolic processes , active transport , secretion etc ..

18
Q

formula of the condensation forming ATP

A

ADP + Pi > ATP

19
Q

formula of the hydrolysis of ATP

A

ATP > ADP + Pi

20
Q

explain what occurs in semi conservative replication of DNA

A

The enzyme DNA helicase unwinds the double helix of DNA and breaks the hyrdogen bonds between complementary bases of the two DNA strands. Each original strand turns into a template strand to build a new strand. the free DNA nucleotides are attracted to the exposed bases on the template strand and they attach to them by complementary base pairing. The free nucleotides and joined to the new strand with a condensation reaction that is catalysed by DNA polymerase which forms hydrogen bonds between the bases on the two strands and reforms a phosphodiester bond between the bases. Each new DNA molecule contains one original strand from the original DNA and one new strand.

21
Q

how does DNA polymerase work ?

A

the DNA strands are antiparallel , DNA polymerase is complimentary to the 3 prime end and adds nucleotides all the way to the 5 prime end , due to DNA strands being antiparallel the new DNA strand is built from the 5’ prime end to the 3’ prime end.

22
Q

explain mesehlsons and stahls experiment evidence that DNA replication is semi - conservative.

A

Bacteria are grown in a broth containing the heavy (15N) nitrogen isotope
. DNA contains nitrogen in its bases
. As the bacteria replicated, they used nitrogen from the broth to make new DNA nucleotides
. After some time, the culture of bacteria had DNA containing only heavy (15N) nitrogen
A sample of DNA from the 15N culture of bacteria was extracted and spun in a centrifuge
This showed that the DNA containing the heavy nitrogen settled near the bottom of the centrifuge tube
The bacteria containing only 15N DNA was then taken out of the 15N broth and added to a broth containing only the lighter 14N nitrogen. The bacteria were left for enough time for one round of DNA replication to occur before their DNA was extracted and spun in a centrifuge
If conservative DNA replication had occurred, the original template DNA molecules would only contain the heavier nitrogen and would settle at the bottom of the tube, whilst the new DNA molecules would only contain the lighter nitrogen and would settle at the top of the tube
If semi-conservative replication had occurred, all the DNA molecules would now contain both the heavy 15N and light 14N nitrogen and would therefore settle in the middle of the tube (one strand of each DNA molecule would be from the original DNA containing the heavier nitrogen and the other (new) strand would be made using only the lighter nitrogen)
. Meselson and Stahl confirmed that the bacterial DNA had undergone semi-conservative replication.

23
Q

explain the processes of transcription

A

. transcription is the process of how MRNA is made :
> RNA enters through the nuclear pores . DNA helicase breaks the hydrogen bonds between the section of DNA that contains the desired gene that will make the desired protein. The breaking of the nucleotides leaves the nucleotides exposed. RNA polymerase binds to the promoter region and moves along the template strand forming complimentary base pairing between the exposed nucleotides. thymine gets replaced with uracil and a pre - MRNA strand is made. the pre - MRNA strand contains introns and exons introns do not code for a specific amino acid so interupt exons that do code for a specific amino acid therefore the Pre - MRNA strand is spliced to remove the introns and then you are left with MRNA.

24
Q

Why does transcription occur ?

A

transcription takes place in the nucleus. DNA is to large to leave through the nuclear pores so MRNA is used to copy a section of DNA that codes for that particular protein and this MRNA leaves the nucleus and joins with a ribosome where the protein is then made , via translation.

25
Q

what is a genome ?

A

entire set of genes or genetic material of an organism.

26
Q

what is a proteome ?

A

it is the entire complement of proteins

27
Q

what is a codon ?

A

when a group of 3 bases code for a particular amino acid.

28
Q

why is it important that genetic code does not overlap ?

A

as a nucleotide is only part of one codon a single nucleotide can not be part of two codons.

29
Q

DNA code is said to be degenerate , what is the meaning of degenerate ?

A

degenerate is when an amino acid can be coded by more than one codon.

30
Q

explain the structure of MRNA

A

. short single strand with no hydrogen bonds
. doesnt contain a amino acid binding site
. does contain a codon binding site

31
Q

explain the structure of TRNA

A

. it is a single short strand of RNA
. it is folded into a 4 clover leaf shape and held together by hydrogen bonds between the complementary base pairs.
. contains a anti codon binding site

32
Q

what is translation ?

A

second stage of protein synthesis takes place at the ribosomes and happens on both eukaryotes and prokaryotes.

33
Q

explain the process of translation

A

a ribosome attaches to the start codon of MRNA and TRNA arrives with a complementary anticodon to the start codon which binds to the MRNA and has a specific amino acid attached to it , methionine. The ribosome moves along to the next codon and it can fit around two at a time. The process is catalysed by an enzyme which catalyses the condensation reaction between the amino acids forming a peptide bond which forms a polypeptide. The ribosome continues to move along the MRNA and TRNA arrives with amino acid at the start codon until a stop codon is reached. The ribosome, MRNA and TRNA separate and the polypeptide is complete.

biology (9 decks)

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