Structure and function of cell components

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Structure and function of cell components

1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids
5. Membranes
6. Cytoskeleton

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Revision

• What do we remember about the structure of DNA
  and RNA from Higher?

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Nucleotide structures

• The building block of a nucleic acid is a
  nucleotide.
• Nucleotides consist of
• A pentose sugar
• A nitrogenous base
• A phosphate group

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Pentose Sugars

• Deoxyribose and ribose differ by the group
  attachment at the 2C.

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Bases

• There are 5 bases
• These can be classified into two types
• Purines
• Double ringed
• Adenine and Guanine

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Bases cont

• Pyrimidines
• Single ringed
• Cytosine, Thymine and Uracil

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Formation of a nucleotide

• A condensation reaction occurs between the OH
  group on the 5 C and phosphate group to form a
  strong phosphodiester bond.
• A condensation reaction occurs between the base
  and the 1 C to form a strong glycosidic bond

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Formation of a nucleotide cont..
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Formation of nucleic acid

• A phosphodiester bond also forms between the 3 C
  and the phosphate group of the next nucleotide to
  form the sugar phosphate backbone.

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Base Pairing in DNA

• A and T join by two weak hydrogen bonds
• G and C join by three weak hydrogen bonds

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DNA strands

• DNA strands are antiparallel

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Revision

• What do we remember from Higher about replication
  and transcription?
• Both processes are controlled by enzymes. Where
  do you think they need to be used and why?
• DNA synthesis always proceeds in the direction 5
  to 3. What problems does this cause and how
  would you overcome these if you were designing a
  cell.

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Enzymes

• DNA polymerase
• Catalyses the linking together of DNA nucleotides
  during replication
• DNA polymerase can only add a nucleotide to the
  3 end of the previous nucleotide.
• RNA polymerase
• Catalyses the linking of RNA nucleotides during
  transcription (and in the replication of the
  lagging strand during DNA replication)

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Enzymes cont

• DNA ligase
• Joins short sections of DNA together
• DNA replication animation
• http//207.207.4.198/pub/flash/24/menu.swf

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Learning Activities

• Read DART pg 48 53 and take notes
• Scholar 4.5
• Nucleic Acids worksheet
• DNA replication worksheet
• Advanced Higher questions
• http//www.maxanim.com/genetics/index.htm
• Look at
• Replication fork
• DNA replication
• Meselson-Stahl experiment
• Make notes on DNA and RNA structure
• Make notes on replication and transcription
• Think about how you will remember which bases are
  purines and which are pyrimidines
• Write a summary of all the different bonds formed
  between molecules by dehydration reactions.