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WJEC AS Biology > Nucleic Acids- Unit 1.5 > Flashcards

Nucleic Acids- Unit 1.5 Flashcards

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1
Q

What 3 components are nucleotides made up of?

A

1+ phosphate groups
Pentose sugar
Organic base containing nitrogen

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2
Q

What is ATP? (2)

A
  • A nucleotide

- Major energy currency of the cell

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3
Q

Describe ATP’s structure. (4)

A

3 phosphate groups
Ribose sugar
Adenine base
Bonds formed by condensation reaction

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4
Q

What is made when ATPase breaks the bond in ATP?

A

ATP + H20 —> ADP + phosphate group + energy

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5
Q

How is ATP and water made?

A

Energy + ADP + phosphate group

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6
Q

What is an exergonic reaction?

A

Energy is released

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7
Q

What is an endergonic reaction?

A

Energy is needed

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8
Q

Where is ATP produced?

A

Cytoplasm, mitochondria and chloroplasts.

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9
Q

What does ATP provide energy for? (4)

A
  1. Metabolic processes (building large, complex molecules from smaller & simpler ones)
  2. Active transport (changes shape of carrier proteins to allow molecules to be transported)
  3. Movement (muscle contraction)
  4. Secretion (packaging & transport secretory products into vesicles)
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10
Q

Advantages of ATP: (3)

A
  1. Involves single reaction, releasing energy immediately.
  2. Energy releases in small amount when and where needed. (unlike glucose)
  3. Soluble & easily transported.
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11
Q

What are the 2 types of nucleic acid?

A 
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
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12
Q

What sugar and bases do DNA nucleotides have?

A

Deoxyribose sugar & adenine, thymine, guanine & cytosine.

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13
Q

What sugar and bases do RNA nucleotides have?

A

Ribose sugar & adenine, uracil, cytosine and guanine.

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14
Q

Which bases are purines and what does their structure look like?

A

Guanine & Adenine- double ring structure

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15
Q

Which bases are pyrimidines and what is their structure like?

A

Cytosine, Uracil & Thymine- single ring structure.

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16
Q

How many hydrogen bonds do the pyrimidines and purines have?

A

Adenine —> Thymine/Uracil has TWO

Cytosine —> Guanine has THREE

17
Q

How is the double helix shape of DNA maintained?

A

Hydrogen bonds.

18
Q

Where is DNA found and what does it do?

A

In nucleus of eukaryotic cells- replicates and synthesises proteins.

19
Q

Is RNA shorter or is DNA shorter?

A

RNA

20
Q

What are the 3 types of RNA?

A 
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
21
Q

What is mRNA? (4)

A
  • Long single-stranded molecule.
  • Synthesised in nucleus.
  • Carries genetic code from DNA to ribosomes.
  • Each strand contains genetic code for one gene that codes for a polypeptide.
22
Q

What is rRNA? (3)

A
  • Found in cytoplasm and component part of ribosomes.
  • Ribosomes synthesised in nucleolus which leave via nuclear pores.
  • Ribosomes are site of protein synthesis by translation.
23
Q

What is tRNA? (5)

A
  • Small single stranded molecule folded into shape of a clover.
  • Each has an amino acid attachment site.
  • At opposite end of tRNA there is a triplet of bases called anticodon.
  • Transport amino acids to ribosomes.
  • Anticodon bases form a complex with mRNA molecule, (codon) allowing translation.
24
Q

Describe DNA replication: (5)

A
  1. Hydrogen bonds holding base pairs break and 2 halves of the DNA molecule separate.
  2. DNA unwinds.
  3. DNA polymerase catalyses free nucleotides to the exposed bases.
  4. Each chain acts as template so free nucleotides can be joined.
  5. Results in 2 identical DNA molecules made from 1 NEW CHAIN and 1 ORIGINAL.
25
Q

What is Meselson and Stahl’s semi-conservative hypothesis?

A

Each DNA strand acts as template for new DNA.

EACH NEW STRAND OF DNA FORMED IS COMPOSED OF ORIGINAL & NEWLY SYNTHESISED STRAND.

26
Q

What is transcription?

A

•DNA acts as template for production of mRNA which is copied from specific regions of DNA called the CISTRON. (equivalent to a gene and codes for polypeptide)

27
Q

Explain the process of transcription. (8)

A
  1. DNA unwinds and unzips at a particular region for copying due to helicase.
  2. RNA polymerase attached to DNA at beginning of sequence to be copied.
  3. One strands acts as template to be copied.
  4. Occurs when free RNA nucleotides align themselves opposite complementary ones on DNA.
  5. RNA polymerase moves along DNA, forming bonds that add nucleotides to RNA.
  6. Results in synthesis of mRNA alongside unzipped DNA.
  7. DNA strands re-join to reform double helix.
  8. mRNA carries DNA code out of nucleus through nuclear pore to cytoplasm and attached to ribosome.
28
Q

Explain the steps in translation. (5)

A

(Begins when mRNA attaches itself to ribosome- after transcription)

  1. Ribosome moves along mRNA and reading code.
  2. mRNA has codons, coding for different amino acid.
  3. tRNA attach to specific amino acid and carry them to mRNA.
  4. Complimentary anticodon & codon bases align, held together by ribosome at attachment site.
  5. Peptide bonds formed between adjacent amino acids by condensation reaction.
29
Q

What do the sequence on the anticodon of tRNA determine?

A

Which amino acid it carries.

e.g CCC attaches to GGG

30
Q

What is initiation?

A

Ribosome attaches to start codon at an end of mRNA molecule.

31
Q

What is elongation?

A

2 amino acids close enough together for a peptide bond to form between them—> new amino acid added to polypeptide chain.

32
Q

What is termination?

A

Amino acids are added until ribosome reaches stop codon. Ribosome detaches from mRNA and polypeptide is released.

33
Q

Where are proteins modified?

A

Golgi body

34
Q

What are exons?

A

They code for proteins:

Exons converted into mRNA to allow gene to be transcribed to protein.

35
Q

What are introns?

A

A nucleotide sequence within a gene. They cause an increase in length.
Also are non-coding regions which are removed in a process called splicing.

36
Q

How are introns removed?

A

Splicing:

Introns removed from pre-mRNA so that the mRNA created can be translated into protein.

WJEC AS Biology (9 decks)

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