Nucleic acids
Laura Armstrong
Teacher
Recall Questions
This topic requires prior knowledge of nucleic acids from GCSE. You can test your knowledge on this below.
What are the monomers of nucleic acids?
Nucleotides
Describe the structure of a DNA nucleotide.
A DNA nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine).
Where is DNA found in a eukaryotic cell?
In the nucleus, packaged into chromosomes. (There is also circular DNA in mitochondria and chloroplasts).
Topic Explainer Video
Check out this @LauraDoesBiology video that explains nucleic acids or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Structure of Nucleic Acids
- Nucleic acids (DNA and RNA) are polymers made from nucleotides.
- Nucleotides contain the elements carbon, hydrogen, oxygen, nitrogen and phosphorus.
- A nucleotide consists of three components:
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Pentose sugar (deoxyribose in DNA, ribose in RNA)
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Phosphate group
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Nitrogenous base (A, T, C, G in DNA; A, U, C, G in RNA)
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- DNA is a double-stranded molecule forming a double helix, while RNA is single-stranded.
DNA Structure and Function
- DNA strands are antiparallel, meaning they run in opposite directions.
- Complementary base pairing ensures accurate replication.
- DNA is stable, allowing it to pass genetic information from one generation to the next.
RNA Structure and Types
- RNA differs from DNA:
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It has ribose instead of deoxyribose.
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It is single-stranded.
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It has uracil (U) instead of thymine (T).
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- Types of RNA:
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mRNA – carries genetic code from DNA to ribosomes.
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tRNA – carries specific amino acids to ribosomes during translation.
- rRNA – makes up ribosomes and helps in protein synthesis.
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Key Terms
- Nucleotide: The monomer of nucleic acids, consisting of a phosphate group, pentose sugar, and nitrogenous base.
- Complementary base pairing: A-T (DNA), A-U (RNA), C-G pairing with hydrogen bonds.
- Antiparallel: DNA strands run in opposite directions (5' to 3' and 3' to 5'). This refers to the carbon number on the deoxyribose sugar.
No answer provided.
Exam Tip
Focus on being able to compare and contrast the structures of DNA and RNA as well as the different types of RNA. See the next 2 study notes to learn more!
No answer provided.
Name the components of DNA labelled A, B and C (2 marks)
A= nitrogenous base
B= Deoxyribose sugar
C= phosphate group.
3 correct= 2 marks
2 correct= 1 mark
Name the monomer of DNA.
DNA Nucleotide
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!