Higher Human Biology

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 – Mutations 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 • Differentiation • Stem Cells • Somatic Cells • Germline Cells • Research & Therapeutic Uses of Stem Cells • 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: • REPRODUCE (Make copies of themselves, remaining undifferentiated) • AND • DIFFERENTIATE (Make other types of cells)

7. 1d) Different Types of Stem Cells • There are 2 different types of STEM CELLS:- • Tissue Stem Cells (also called Adult Stem Cells) • 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, so these cells can differentiate into any type of cell (Pluripotent)

9. 1f) Tissue Stem Cells 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. Somatic Cell (e.g. Cheek Cell) Diploid (2 sets of chromosomes) 1h) Somatic Cells Cell Division (Mitosis) The scientific name for a body cell is a Somatic Cell Any cell in the body other than cells involved in reproduction 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 New Somatic Cells (cheek cells) Diploid (2 sets of chromosomes)

12. Germline Stem Cell in Ovary (Diploid) Cell Division (Meiosis) 1i) Germline Cells New Egg Cell (Haploid – 1 set of 23 single chromosomes) Germline cells are gametes (sperm and ova) and the stem cells that divide to produce gametes In humans, germline cells are found in the ovaries and testes A germline stem cell is diploid (2 sets of 23 chromosomes) and can divide by mitosis OR meiosis The nucleus of a germline stem cell can divide by mitosis to produce more germline (diploid) stem cells The nucleus of a germline stem cell can divide by meiosis to produce gametes (haploid) cells It undergoes 2 divisions (first separating homologous chromosomes and secondly separating chromatids)

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 from the embryo can self-renew, under the right conditions in the lab Stem cells can be used for repairing damaged or diseased organs or tissues e.g. corneal transplants, skin grafts for burns/damaged skin Stem cells can be used as model cells to study how diseases develop or for drug testing

15. 1l) Embryonic Stem Cell Ethical Debate 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 which results in a mass of abnormal cells Some of these cells may fail to attach to each other, spreading through the body where they form secondary tumours (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 • Testing Your Knowledge 1 Page 8 Q’s 1-4 2. Testing Your Knowledge 2 Page 15 Q’s 1-3 3. Quick Quiz