Summary A LEVEL BIOLOGY -ESSAYS PLANS.AQA. [CELL BIOLOGY

A LEVEL BIOLOGY -ESSAYS PLANS.AQA. [CELL BIOLOGY] lOMoAR cPSD| Downloaded by michael kinyua () A level AQA-A-Level-Biology-Essay-Plans Cell Biology (Queen's University Belfast) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university lOMoAR cPSD| Downloaded by michael kinyua () Biology Essay Plans The importance of nitrogen containing substances in biological systems (25 marks) 1. DNA:  Has nitrogen containing bases- base pairing  In eukaryotes, found in nucleus as histone associated chromosomes  Stores genetic information and allows genetic continuity through generations  Replicated semi conservatively using DNA helicase and DNA polymerase to form 2 identical molecules, each containing a nucleotide strand from the original molecule  Forms DNA copies which split into genetically identical daughter cells in mitosis  And genetically different daughter cells in meiosis  Which are fundamental to biological systems 2. RNA:  Contains nitrogen containing nucleotide bases  tRNA is a clover shaped, single stranded RNA molecule held in shape by hydrogen bonds  Has a specific amino acid binding site  Anticodon complementary only to a very specific codon on mRNA  Purpose to bring amino acids to the ribosome in translation  Without tRNA, translation couldn’t occur and proteins couldn’t be made 3. ATP:  Provides energy for many reactions  Hydrolysed from ATP to ADP and Pi  Used in muscle contraction  Used to phosphorylate compounds to make them more reactive (e.g. glucose in glycolysis  Immediate source of energy from the cell 4. Amino Acids/Enzymes:  Proteins are made up of amino acids- nitrogen in amine group  Enzymes are a type of protein which act as a biological catalyst  Specific tertiary structure with an active site only complementary to substrate  Enzyme substrate complex lowers the activation energy of a reaction  ATP hydrolase catalyses the hydrolysis of ATP to AD