Bio CBA2

• What is DNA?

  DNA is a double helix comprising two strands of nucleotides, each nucleotide formed of a deoxyribose sugar molecule, a phosphate group and one of four different nitrogenous bases.
• What is the bond that exists between two deoxyribose sugars and one phosphate group?

  Phosphodiester bond.
• What is the bond that exists between two complementary strands of DNA?

  Hydrogen bond.
• The rule of complementary base pairing is that 2 hydrogen bonds exist between Adenine and Thymine, while 3 hydrogen bonds exist between Cytosine and Guanine.
• The smaller the size of the DNA piece, the smaller its molecular mass, so it can travel faster through the agarose gel.
• The chemical elements which make up carbohydrates are carbon, oxygen and hydrogen, with molecules held together by glycosidic bonds.
• The chemical elements which make up lipids are carbon, hydrogen and oxygen, with molecules held together by ester bonds.
• The chemical elements which make up proteins are carbon, hydrogen, oxygen and nitrogen, with molecules held together by peptide bonds.
• Carbohydrates provide an immediate source of energy.
• Fats provide insulation and long-term storage of energy.
• Proteins allow for growth and repair of cells.
• Glycogen and starch are synthesised from glucose.
• Polypeptides and proteins are synthesised from amino acids.
• Lipids are synthesised from glycerol and fatty acids.
• Cellulose is synthesised from carbohydrates.
• The development of cancer is a multi-step process that includes accumulation of mutations, angiogenesis and metastasis.
• Cancer is caused by carcinogens, which may be ionising radiation (e.g. X-rays, gamma rays, alpha particles) or non-ionising radiation (e.g. UV light). Chemicals such as tobacco smoke are also carcinogens.
• A haploid cell has one set of chromosomes, while a diploid cell has two sets of chromosomes.
• Meiosis produces haploid gametes, which keeps the chromosome number from doubling each time sexual reproduction occurs. When haploid gametes fuse, the resulting cell becomes diploid again.
• The function of the cell surface membrane is to control the movement of substances in and out of the cell.
• The function of the cellulose cell wall is to protect the plant cell from injury and give it a fixed shape.
• The function of the cytoplasm is to provide a place for cell activities to take place.
• The function of the nucleus is to control the cell and to store genetic information.
• The function of the cell vacuoles is to store water and other substances within the cell.
• Plant cells have a large central vacuole which contains cell sap (composed of sugars, mineral salts and amino acids). Animal cells have many small vacuoles that contain water and food substances.
• The function of the chloroplast is to make food for the plant by photosynthesis.
• The function of the rough endoplasmic reticulum (RER) is to transport proteins synthesised by ribosomes to the Golgi body for secretion out of the cell. It has ribosomes attached to its surface, which synthesise proteins to be transported out of the cell.
• Ribosomes lying freely in the cytoplasm synthesise proteins that are used within the cytoplasm of the same cell.
• The smooth endoplasmic reticulum (SER) synthesises substances such as fats and steroids, and converts harmful substances into harmless substances through detoxification.
• The function of the Golgi body is to chemically modify substances made by the ER, and store and package these substances in vesicles for secretion out of the cell.
• The mitochondria is the site of aerobic respiration, in which food substances are broken down to release energy in the form is Adenosine Triphosphate (ATP), for growth and reproduction.