OCR Gateway Science B3 Notes

MOLECULES OF LIFE- The Nucleus contains the cell's DNA.- DNA is used to make genes. Because they code for proteins they control the cells activity e.g. DNA codes for enzymes needed in respiration.DNA forms structures called chromosomes and each region of the chromosome is called a GENE.- DNA is a code for making proteins which are used for growth and repair of cells.-James WATSON & Francis Crick are credited for the structure of DNA which is a double helix shape formed by 2 coiled strands of cross linked chemicals called bases ( A and T, C and G), called base pairs.HOW? - rosalind franklin & maurice wilkins Xray crystallography showed DNA as 2 chains which wound to form a double helix/ erwin chargaff's data that proved there was equal amounts of A and T, and C and G bases.Mitochondria is the site of cell respiration and is within the cytoplasm; in the presence of oxygen energy is released from glucose. can't be seen under microscope.Cells that respire a lot like muscle and liver cells have more mitochondria present compared to other cells; they need more energy to carry out their functions.- Different proteins in the body have different DNA codes. - DNA is coded by bases and each three bases code for an amino acid.- Different base sequences cause proteins to differ in shape and therefore also function.To validate findings, results must be repeated by other scientists; this is why new discoveries aren't immediately accepted.making proteins;Base A can only code with base T and the base C can only code with G. This is important to the cross link structure of DNA and when DNA is copied to make proteins.* first the DNA code is copied TRANSCRIPTION - the copied code is now called Messenger RNA (mRNA)* mRNA leaves the nucleus and goes to the ribosomes and is used to put amino acids in the right order to form the protein TRANSLATION, tRNA transports the amino acids to the ribosome and then binds with mRNA,