Biology B1

• Eukaryotes: all animals and plants, made from complex eukaryotic cells.
• Prokaryotes: bacteria, made from simple prokaryotic cells.
• Nucleus

  Genetic material (eukaryotes)
• Mitochondria


  Respiration and enzymes (eukaryotes)
• Cytoplasm


  Site of chemical reactions (eukaryotes and prokaryotes)
• Cell membrane


  Partially permeable barrier and receptors for cell communication e.g. hormones (eukaryotes and prokaryotes)
• Chloroplasts


  Photosynthesis and green chlorophyll (plant cells-eukaryotes)
• Cell wall

  Rigid, cellulose, support for cell (plants and prokaryotes)
• Chromosomal DNA


  Circular chromosome, free floating, controls cell activities and replication (prokaryotes)
• Plasmids

  Loops of DNA-not part of chromosome, contain genes e.g. antibiotic resistance and can be passed between bacteria (prokaryotes)
• Light microscopes: view cells and things like nuclei and chloroplasts.
• Electron microscopes: smaller things in more detail e.g. structure of mitochondria, plasmids and viruses.
• Transmission Electron Microscopes (TEMs): expensive, not portable and cannot look at living tissue.
• Microscopes magnify and increase resolution (distinguishes two close points)
• Total magnification = eyepiece lens mag. × objective lens mag.
• Magnification = image size/object size
• DNA: arranged into chromosomes (coiled DNA), sections are called genes.
• Nucleotides (monomer) join to make DNA (polymer), each nucleotide contains a base, a sugar and a phosphate.

  Bases: Adenine, Guanine, Thymine and Cytosine, complementary AT and GC.
• Gene: section of DNA that codes for a protein.
• Proteins: made from chains of amino acids. Different numbers and orders which creates different shapes and functions.
• Each amino acid is coded for by a sequence of 3 bases in the gene.
• Amino acids join together to make proteins, following the order of bases in a gene.
• DNA needs to move from the nucleus to the cytoplasm for protein synthesis, done using mRNA-a single strand of DNA.
• Transcription: DNA strands unzip around gene then copied using complimentary bases = mRNA
• Translation: mRNA is in the cytoplasm, amino acids match the triplet codes and join together to form a protein.
• Enzymes: biological catalysts, speeds up reaction without changing or being used up.

  Reduce the need for high temps.

  Each reaction has its own enzyme.

  Enzymes = protein, each with own unique shape.
• Substrate: molecule changed in the reaction.
• Active site: part that binds to substrate.
• Enzymes have high specificity for their substrate, only work with one substrate.
• Substrate has to fit into the active site, if not the reaction won't be catalysed, 'lock and key'
• High temp. = Rate increases

  Too hot = denaturing of enzyme-shape changes, substrate cannot fit in active site, reaction no longer catalysed and stops