National 5 Biology Producing New Cells

Cells & Chromosomes As cells grow, they must divide to create newer smaller cells and more of them. In order to do this, the information in the nucleus must be copied so that each new cell gets a complete set of information, before the cell divides. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cells & Chromosomes This information is carried on the chromosomes within the nucleus of the cell. Human body cells have 46 chromosomes or 23 pairs. All body cells are said to be diploid. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cells & Chromosomes Sex cells only have 23 chromosomes and they are said to be haploid. The number of chromosomes found in a cell is called the chromosome complement. This is one set from each parent. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cells & Chromosomes This chromosome complement is different for different organisms, e.g. Onion – 8 pairs Man – 23 pairs Privet hedge – 23 pairs Chimp – 24 pairs Dog – 39 pairs Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cell Division Before the cells can divide, the nucleus must divide into 2 new daughter nuclei. Each daughter nucleus must receive the same information as the original nucleus. This is done by a process called mitosis. Mitosis is essential for cell growth and cell repair. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Mitosis Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Mitosis Prophase – the chromosomes appear as double threads, each made up of two chromatids. The 2 chromatids are held together by a centromere. Metaphase – the nuclear membrane disappears and the chromosomes line up on the equator of the cell. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Mitosis Anaphase – the chromatids attach to the spindle fibres and they are then pulled apart. Telophase – the nuclear membranes are now reformed around each of the sets of chromosomes to form two new nuclei. The cytoplasm can now divide and the cell becomes two new daughter cells, each with identical chromosomes to each other as well as the mother cell. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cell Culturing We can use the process of mitosis and cell division to culture cells in an artificial environment. This involves growing cells under favourable conditions and requires: A suitable temperature A suitable pH A supply of oxygen A suitable growing medium Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cell Culturing We can grow cells in a liquid called nutrient broth. This broth provides the cells with all the nutrients it will require to grow and multiply. This broth can also be added to agar which is a jelly-like substance and sets hard at room temperature and the cells will grow on top. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cell Culturing In industry, cells can be cultured in vessels called fermenters. These allow the scientist to control the environment very carefully. They have various inlet pipes which allow essential materials to be passed into the vessel. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Fermenter Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Cell Culturing Scientists can grow bacteria and fungi in fermenters to rapidly increase their numbers. However, when carrying out this type of work it is important to avoid unwanted cells from growing. To achieve this, we use aseptic techniques to create sterile conditions. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Aseptic Techniques We must try to maintain as sterile an environment as possible at all times. The bench should be sterilised with disinfectant before we start and after we finish. Only equipment needed should be out. The bench should be a non-absorbent material like plastic or glass. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Aseptic Techniques Long hair should be tied back. Protective clothing should be worn at all times, i.e. labcoat, gloves, mask, safety glasses, etc… Hands should be thoroughly washed before and after working with any cultures. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Aseptic Techniques All equipment should be sterilised. All glassware should be sterilised. An autoclave is used for sterilising equipment and glassware. It is used to heat its contents to 121oC for 20 minutes. It uses pressure to achieve this temperature. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Autoclave Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Aseptic Techniques Dishes and bottles should not be left open. Transfer of cells or materials should be conducted as quickly as possible to lessen the chances of contamination. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Preparing Plates We often use petri dishes to culture micro-organisms. The nutrient agar is sterilised in the autoclave. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Preparing Plates It is then carefully poured into the petri dish using the following precautions: The work is carried out in a column of warm air which carries spores upwards instead of downwards onto the plate. The neck of the McCartney bottle is flamed. The lid of the petri dish is opened, the broth poured in, and the lid closed as quickly as possible. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Preparing Plates The dish is now left to cool and the agar jelly should set. We can now transfer cells from a pure culture onto our agar. This is done using an inoculating loop to spread the cells across the agar surface. Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Preparing Plates Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson

Preparing Plates Good Contaminated Saturday, 17 November 2018Saturday, 17 November 2018 Mr G Davidson