B3a

B3a

1. Mitochondria

   • Cell respiration is carried out inside mitochondria
   • Liver and muscle cells have large numbers of mitochondria because they need large amounts of energy to carry out their funtions

2. DNA Structure

   • DNA molecules have two strands coiled to a double helix
     • The double helix has cross links made of chemicals called bases
   • There are four different bases in DNA
     • Each cross link contains two bases known as base pairs

3. Chromosomes

   • Long coiled molecules of DNA divided up into regions called genes

4. Protein

   • Protein structure is determined by DNA base code
     • The order of bases found in DNA is called base code. Each three bases for an amino acid
       • For example, the sequence CAA codes for the amino acid called valine
   • Protein Synthesis
     • > To make proteins the DNA code must be copied (transcription)
       • > The copied code is called messenger RNA (mRNA)
         • > The mRNA leaves the nucleus and travels to the ribosomes
           • At the ribosomes the code is used to put the amino acids together in the right order and form the protein (translation)
     • To make the protein, a copy of the gene is made as the gene cannot leave the nucleus.

5. DNA

   • By coding for proteins, DNA controls the functions of the cells. For example, DNA codes for the enzymes involved in respiration. Without these enzymes, respiration wouldn't take place
   • Watson and Crick used data from other scientists to build a model of DNA. Originally, they thought DNA was a triple helix. They needed an x-ray photography taken by Rosalind Franklin to confirm it was a double helix
     • When scientists make new discoveries it is important that their results are repeated by other scientists. This will help make their results valid

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