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Biology > DNA and RNA > Flashcards

DNA and RNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are nucleic acids?

A

Organic compounds including DNA, which is found in nuclei and cytoplasm as it contains the genetic material and it is hereditary.

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2
Q

What is a nucleotide structure?

A

Pentose sugar, phosphate group and nitrogenous base. It is the monomer of nucleic acids.

In DNA, the sugar is deoxyribose. In RNA, the sugar is ribose.

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3
Q

What are the nitrogenous base pairs?

A

A and T
G and C
A and U

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4
Q

How are polynucleotides formed?

A

Condensation reactions between the hydroxyl groups on the phosphate group of 1 nucleotide and the pentose sugar of another, creating a phosphodiester bond.

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5
Q

What is the structure of DNA?

A

2 long polynucleotide chains in a double helix. They are antiparallel and are held together by hydrogen bonds between the bases.

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6
Q

What is the function of RNA?

A

Messenger molecule to transfer genetic information from DNA to ribosomes for protein synthesis.
Regulation and protein synthesis
Make up ribosomes

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7
Q

What are the differences between DNA and RNA?

A

DNA:
2 strands
very long
deoxyribose
thymine
always has base pairs

RNA:
1 strand
shorter
ribose
uracil

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8
Q

What is the structure and function of ATP?

A

Adenine, ribose and 3 phosphate groups.

Regulates metabolic pathways. It is the energy currency of the cell.

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9
Q

How do ADP and ATP convert?

A

When the terminal phosphate is removed, ADP formed via a hydrolysis reaction which is catalysed by the enzyme ATP hydrolase.

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10
Q

How is ATP an immediate energy source?

A

= universal energy currency because used to transfer energy.
Energy is released when bonds between phosphates in ATP are hydrolysed - coupled with energy-needing cellular reactions

Energy can be supplied very fast and in manageable amounts.

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11
Q

What are the roles of ATP?

A

Metabolic processes eg synthesis of biological molecules
Movement
Active transport
Secretion - form vesicles
Molecule activation - make them more reactive

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12
Q

Why must cells divide?

A

Growth, reproduction and to replace old/damaged cells.
DNA is replicated in interphase.

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13
Q

What is semi-conservative replication?

A

How DNA replicates, creating 2 DNA molecules consisting of 1 original strand and 1 new strand.

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14
Q

How is DNA replicated?

A
  1. 2 strands separate as the helix unwinds (DNA gyrase)
  2. DNA helicase breaks H bonds, unzipping DNA
  3. Each strand acts as a template. Free nucleotides bind to the exposed bases by complementary base pairing
  4. DNA polymerase catalyses formation of phosphodiester bonds between adjacent nucleotides from 5’ to 3’
  5. Energy to make bonds from hydrolysis of activated nucleotides to release extra phosphate groups
  6. 2 DNA molecules formed, each contain 1 old + 1 new strand of DNA
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15
Q

What is the evidence for semi-conservative replication?

A

Meselson + Stahl - original and new DNA strands were labelled depending on their weight (N isotopes) and compared by centrifuging extracted DNA - the heavier it was, closer to the bottom of the tube

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16
Q

What were the results of the evidence for semi-conservative replication?

A

Light DNA at the top in a band
Heavy DNA near the bottom
The DNA from the bacteria was in the middle - must have both heavy and light strands.

17
Q

What are DNA mutations?

A

The wrong nucleotide is inserted, changing the genetic code. Normally removed but some different alleles can be created (good or bad).

18
Q

What is a gene?

A

A sequence of bases in DNA coding for a polypeptide or functional RNA that is located at a fixed locus on DNA.

19
Q

Define transcription.

A

Conversion of DNA code into mRNA code.

20
Q

What is the genetic code?

A

The specific sequence of bases in DNA/RNA that codes for a sequence of amino acids in protein synthesis

21
Q

What are the features of the genetic code?

A

Triplet code - 3 bases code for 1 amino acid
Degenerate - different codons can code for the same amino acid
Non-overlapping - each triplet is only read once
Universal - each triplet codes for the same amino acid in all organisms

22
Q

What is the role of mRNA?

A

Much smaller than DNA so fits through nuclear pores. Transfers genetic information from nucleus to cytoplasm which determines sequence of amino acids in a protein.

23
Q

What is the structure and function of mRNA?

A

Single stranded RNA molecule that relays genetic information stored on DNA to the cytoplasm - protein synthesis.

24
Q

Why is mRNA single stranded?

A

One DNA strand (coding strand) contains base sequence for the amino acid. The complementary strand = template strand - used as template in transcription so mRNA synthesised has same sequence as coding strand.

25
Q

What does RNA polymerase do?

A

Catalyses formation of mRNA strand from template strand.

26
Q

What are the steps of transcription?

A
  1. gene is unwound and hydrogen bonds break
  2. Exposed DNA template strand used to synthesis the mRNA. Free nucleotides pair with the template strand
  3. RNA polymerase adds RNA nucleotides by catalysing formation of phosphodiester bonds. A new mRNA strand is synthesised
  4. The mRNA strand detaches, ending transcription so the helix reforms.
27
Q

Define translation.

A

Conversion of mRNA code into aa sequence.

28
Q

What is tRNA for?

A

It specifies which amino acid is coded for by which codon. Each binds to one specific amino acid and its mRNA codon.

29
Q

What is the function of ribosomes?

A

Ribosomes are the site of translation and are made of protein and rRNA (ribosomal RNA). Mg ions bind them together.

30
Q

What is the process of translation?

A
  1. After leaving the nucleus though a pore, mRNA attaches to a ribosome on the RER
  2. tRNA carries the corresponding amino acid to each codon
  3. tRNA anticodons bind to the complementary mRNA codons by temporary hydrogen bonds
  4. The ribosome reads the code, bringing adjacent tRNA together. An enzyme catalyses the formation of a peptide bond between the amino acids with energy from ATP
  5. When the polypeptide is fully assembled, it breaks loose from the ribosome and the mRNA is broken down.
31
Q

Why must DNA be built in the 5’ to 3’ direction?

A

DNA polymerase has a specific shape, so enzymes have to work in specific direction as complementary to 3’.
So 1 strand is continuous, the other is lagging.

Biology (32 decks)

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