1. Higher Human Biology Unit 1 Human Cells KEY AREA 1: Division & Differentiation

2. Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Human Cells key areas : - Key Area 1 – Division & Differentiation Key Area 2 – Structure & Replication Key Area 3 – Gene Expression Key Area 4 – Health & Disease Key Area 5 – Human Genomics Key Area 6 – Metabolic Pathways Key Area 7 – Cellular Respiration Key Area 8 – Energy Systems

3. Human Cells Learning Intentions KEY AREA 1 – Division & Differentiation a)Differentiation b)Stem Cells c)Somatic Cells d)Germline Cells e)Research & Therapeutic Uses of Stem Cells f)Cancer Cells

4. 1a) Differentiation a) DIFFERENTIATION Cell differentiation is when an unspecialised cell becomes specialised to carry out a specific function (e.g. a basic animal cell becoming specialised into a goblet cell in the trachea) A cell becomes specialised by the switching on and switching off of specific genes – this is called gene expression Once a cell becomes differentiated it only expresses the genes that produce proteins characteristic for that type of cell Examples of differentiated cells are sperm cells, goblet cells, nerve cells, red blood cells,

5. 1b) Stem Cells Stem cells are cells that are unspecialised and have the ability to differentiate into specialised cells

6. 1c) Stem Cells have 2 roles Stem cells are different from other cells of the body because stem cells can: 1.SELF-RENEW (Make copies of themselves) AND 2.Differentiate (Make other types of cells)

7. 1d) Different Types of Stem Cells There are 2 different types of STEM CELLS:- 1.Tissue Stem Cells (also called Adult Stem Cells) 2.Embryonic Stem Cells

8. 1e) Where do we find Embryonic Stem Cells? Embryonic Stem Cells are found in a human blastocyst ALL of the genes in an Embryonic Stem Cell have the ability to be switched on Embryonic Stem Cells can make ALL types of differentiated cells (pluripotent)

9. 1f) Where do we find Tissue Stem Cells? Tissue Stem Cells are found in the brain, skin, testicles, bone marrow, breast, intestines, muscles, surface of the eye (cornea) Some of the genes in a tissue stem cell have already been switched off which means Tissue Stem Cells produce a limited range of cell types Tissue Stem Cells are multipotent (can make SEVERAL types of differentiated cells) Tissue (adult) stem cells replenish differentiated cells that need to be replaced Example of Tissue Stem Cells are stem cells in bone marrow which can differentiate into different types of blood cells (e.g. red blood cells, platelets, phagocytes and lymphocytes)

10. 1g) Stem Cells & Medical Treatments

11. 1h) Somatic Cells The scientific name for a body cell is a Somatic Cell All differentiated cells (except gametes) arise from Stem Cells and are called Somatic Cells Somatic cells divide by mitosis to form more somatic cells Each somatic cell contains 46 chromosomes and is diploid (2 sets of 23chromosomes) Somatic cells differentiate to form different body tissue types; epithelial, connective, muscle and nerve Body organs are formed from a variety of tissues working together Epithelial cells cover the body surfaces and line body cavities Blood, bone, and cartilage cells form connective tissue Muscle cells form muscle tissue Nerve cells form nervous tissue Mutations in somatic cells are not passed to offspring Somatic Cell (e.g. Cheek Cell) Diploid (2 sets of chromosomes) Cell Division (Mitosis) New Somatic Cells (cheek cells) Diploid (2 sets of chromosomes)

12. 1i) Germline Cells The scientific name for a cell that produces gametes is a Germline Cell In humans, germline cells are found in the ovaries and testes Germline cells can divide by meiosis to produce gametes (haploid) cells Mutations in germline cells are passed to offspring Germline cells can divide by mitosis to produce more germline (diploid) cells Germline Cell in Ovary (Diploid) Cell Division (Meiosis) New Egg Cell (Haploid – 1 set of chromosomes)

13. 1j) Human Life Cycle

14. 1k) RESEARCH & 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 can be used for repairing damaged or diseased organs or tissues e.g. corneal transplants, skin grafts for burns Stem cells can be used as model cells to study how diseases develop or for drug testing Law/Regulations. Stem Cell use is regulated. Embryonic cells must not be allowed to develop beyond 14 days, around the time a blastocyst would be implanted in a uterus

15. 1l) Embryonic Stem Cell Ethical Debate AGAINST using Embryonic Stem CellsFOR using Embryonic Stem Cells  A human life begins with a fertilised egg and it should not be harmed  A fertilised egg is a human being with a soul  Stem cell research is unnatural  A fertilised egg is not a person, although it has the potential to develop into a person  At 14 days or less, the fertilised egg has developed into an embryo but it does not have a brain, or nervous system or any “feelings”  A foetus can be terminated at up to 20weeks, so destroying a 14day old embryo seems less objectionable  Stem Cell Research has the potential to benefit millions of people with medical conditions  Stem Cell Research uses Embryos that were generated for IVF but were not used & would be destroyed anyway Possible solution to the Embryonic Stem Cell Debate:- Use Induced Pluripotent Stem Cell (IPS) – these are stem cells created from reprogramming differentiated cells back to an embryonic state Problem with IPS Cells – viruses used in the procedure cause cancers in mouse models, so more research needs to be done on IPS cells

16. 1m) Cancer Cells Cancer cells divide excessively to produce a mass of abnormal cells called a tumour. Tumour cells do not respond to regulatory signals and may fail to attach to each other. Secondary Tumours form if cancer cells fail to attach to each other so they spread through the body (metastasis) Metastasis is the spread of cancer from its primary site to other places in the body

17. Human Cells Questions KEY AREA 1 – Division & Differentiation 1.Testing Your Knowledge 1Page 8 Q’s 1-4 2. Testing Your Knowledge 2Page 15Q’s 1-3 3. Quick Quiz