BIOLOGY

• Chloroplasts are organelles found in plant cells that are responsible for photosynthesis, converting light energy into chemical energy.
• Protein synthesis involves transcription of a gene into messenger RNA (mRNA), and translation of mRNA into an amino acid sequence at the ribosomes.
• In eukaryotic cells, transcription occurs in the nucleus.
• Additional sources for Enzymes can be found in the DNA & Proteins Video Playlists on the Stage 2 Biology website.
• Critical & Creative Thinking ~ Food Spoilage is discussed on pages 4-5 of the Appendices in the Extra Resources section.
• Enzymes - Activities are discussed on page 45-52 of the Biology Essentials Workbook and can be completed as Worksheet 1.4 – Enzymes on page 53.
• Genes are a segment of DNA on a chromosome that has a complete sequence of bases to direct the manufacture of a protein or RNA.
• Proteins are made of subunits called amino acids – an organic molecule.
• There are twenty different amino acids that are found in proteins.
• The instructions for which amino acids and in what order for each protein are contained on the gene.
• The nucleotide bases on the gene form a simple four letter alphabet which can code for the 20 amino acids.
• In the language of the genetic code, all the words, called “codons”, for the individual amino acids are exactly three bases long.
• The gene sequence on the DNA molecule acts as a template to make a complementary mRNA molecule.
• Only one strand of the DNA is used to provide the code to make the mRNA and hence the polypeptide, this is called the template strand.
• The term codon describes a three base mRNA sequence that codes for one amino acid.
• The term codon is also used for a DNA bases triplet on the non-template strand.
• DNA is a double helical molecule that consists of two complementary strands, with four bases A, T, G, C.
• Competitive Inhibitors block the substrate entering the active site by binding to the active site, mimicking the shape of the enzyme.
• Enzyme Concentration: The concentration of an enzyme can affect the rate of reaction, with higher enzyme concentration leading to a higher reaction rate.
• Inhibitors: Chemicals that reduce the action of enzymes are known as inhibitors, with two main types being Competitive Inhibitors and Non-Competitive Inhibitors.
• Denaturation: Both extremely high temperature and extreme pH (far from optimum pH) cause reduced enzyme activity due to the enzyme denaturing, breaking bonds in the enzyme and altering the shape of the active site.
• Enzymes Activity: When the temperature exceeds a certain level (50°C), the enzyme denatures, changing the shape of the active site and preventing the substrate molecules from binding.
• Increasing the concentration of the substrate increases the chance of colliding with the enzyme, therefore increasing the reaction rate, but it can not occur indefinitely as then the amount of enzyme present will become a limiting factor instead.
• The rate of an enzyme-controlled reaction is affected by the concentration of reactants, the concentration of the enzyme, and the concentration of Substrate.
• Enzyme Activity - pH: The optimum range for most human enzymes is around pH 6-8, with each enzyme having its own optimum pH and working in a narrow pH band.
• Non-Competitive Inhibitors bind elsewhere on the enzyme and this changes the shape of the enzyme and thus reduces enzyme-substrate binding.
• One strand of DNA acts as a coding (gene) strand, the other as a complementary strand, the template strand.
• A gene composes a length of DNA that codes for one protein.
• Messenger RNA (mRNA) originates in the nucleus and migrates to the cytoplasm.
• mRNA is a single stranded molecule about 00’s to 000’s of nucleotides long, with four bases A, C, G, and Uracil (U replaces T).
• mRNA nucleotide contains ribose sugar.
• mRNA consists of a sequence of mRNA nucleotides transcribed from the DNA template strand.
• mRNA contains groups of three bases called codons which code for specific amino acids.
• Transfer RNA (tRNA) is like mRNA but in a clover leaf shape, single stranded about 80 nucleotides long, with four bases A, C, G, and Uracil (U replaces T).
• Antibodies are part of the immune system and act by binding to antigens, which inactivates the antigen.
• Antigens are foreign or non-self molecules.
• All reactions in cells require an input of energy, enzymes lower the activation energy.
• Enzymes are not consumed in the reaction, but can be used over and over again.
• The product forms and breaks away from the enzyme, leaving the enzyme unchanged.
• tRNA’s function is to pick up amino acids and place in the order specified on the mRNA molecule.