Unit 1

• A somatic cell is any cell in the body other than cells involved in reproduction.
• Slow twitch muscle fibres contract relatively slowly, but can sustain contractions for longer.
• Diploid refers to a somatic cell that has two sets of chromosomes.
• Somatic cells divide by mitosis to form more somatic cells, maintaining the diploid chromosome number.
• Gametes (sperm and ova) and the stem cells that divide to form gametes are part of the germline cells.
• Haploid refers to a germline cell with only one set of chromosomes.
• If a germline cell is dividing to make more diploid germline cells, it uses mitosis.
• If a germline cell is dividing to make haploid gametes, it uses meiosis.
• During meiosis, the nucleus of a germline stem cell undergoes two divisions, firstly separating homologous chromosomes and secondly separating chromatids.
• Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell.
• Cellular differentiation allows a cell to carry out specialised functions.
• Embryonic stem cells are found in the very early embryo and can differentiate into all the cell types that make up the individual.
• Embryonic stem cells can differentiate into all the cell types that make up the individual due to the ability of pluripotency.
• Tissue stem cells can differentiate into all of the types of the cell found in a particular tissue type, a process known as multipotent differentiation.
• Blood stem cells located in bone marrow can give rise to blood cells such as red blood cells, platelets, phagocytes and lymphocytes, a process known as haematopoiesis.
• Therapeutic uses of stem cells involve the repair of damaged or diseased organs or tissues.
• Bone marrow transplants, regeneration of damaged skin and corneal repair are examples of therapeutic uses of stem cells.
• Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work.
• Stem cells are used as model cells in research to study how diseases develop and for drug testing.
• Cancer cells do not respond to regulatory signals and divide excessively to form a mass of abnormal cells called a tumour.
• Cells within the tumour may fail to attach to each other, spreading through the body, a process known as secondary tumour formation.
• DNA is stored in the nucleus and has a double helix shape.
• The 3 parts of a DNA nucleotide are phosphate, deoxyribose sugar and a base.
• The 4 DNA bases are Thymine, Guanine, Cytosine, Adenine.
• The complementary base partner for thymine is Adenine.
• DNA strands are held together by hydrogen bonds between the bases.
• A single strand of DNA is held together by a sugar-phosphate backbone.
• The 5’ end of a DNA strand is the end with a phosphate.
• The 3’ end of a DNA strand is the end with a deoxyribose sugar.
• DNA strands can be antiparallel, meaning they run in opposite directions.
• Lactate is the product of pyruvate breakdown when no oxygen is present.
• The substrate molecule(s) have a high affinity for the active site.
• Oxaloacetate combines with acetyl CoA to produce citrate in the citric acid cycle.
• Glycolysis is the conversion of glucose to pyruvate.
• The enzyme concentration has become a limiting factor as all the active sites are occupied.
• Competitive inhibitor binds at the active site preventing the substrate from binding.
• Aerobic respiration consists of three stages: Glycolysis, the citric acid cycle and the electron transport chain.
• The substrate attaches to the active site on the enzyme.
• Fast twitch muscle fibres contract relatively quickly, over short periods.
• The electron transport chain is a series of membrane-bound proteins.