Cell growth and repair

Learning goals We are learning what is cancer. We are learning the difference between the types of tumours. We are learning the differences between a normal cell and cancer cell.

cell division frequency growing organism = rapid mitosis of cells in areas of growth cells likely to be damaged or injured as they function also have high rates of mitosis

Some examples cell division happens at different rates depending on type of cell nerve cells do not undergo mitosis once they mature skin cells and cells in the digestive tract, undergo cell division regularly Intestinal cells – roughly every three days Red blood cells – roughly every four months

checkpoints Proteins monitor cell activities and surroundings and send messages to nucleus G1 cell size, nutrients, growth factors, DNA damage G2 cell size, DNA replication M chromosome attachments to spindles

checkpoints Cells remain in interphase if: Signals from other cells not to divide Not enough nutrients DNA not replicated DNA is damaged

G0 Phase Cells can enter a resting phase called G0 Temporary (muscle cells) or permanent (nerve cells, DNA damage)

Cell death Apoptosis Controlled death of old cells White blood cells Necrosis Cells may die due to external factors Toxins, infections

cancer Abnormal cell division Mutations, carcinogens Instead of apoptosis, these cells divide uncontrollably Don’t stay in interphase

tumour Mass of cells continue to grow with no obvious function Can reduce the effectiveness of surrounding tissue

tumours Benign – does not affect surrounding cells other than crowding Malignant – interferes with surrounding cells; cancerous Metastasis – cells that break away

cancer May stimulate other cells to start replicating uncontrollably, thus spreading cancer and causing different types of cancer

causes Mutations – random changes in DNA Carcinogens – environmental factor causing cancer Mutagen – carcinogen that causes a mutation

A B C Ds A = asymmetry B = borders are irregular C = color D = diameter

Let’s watch! Video

Comparing cancer and normal cells Explain how you know which diagram shows cancer cells? three cells with irregularly shaped nucleus irregular shape

Cancer vs normal cells What do you think is happening in this picture? If the cancerous cells were left untreated, what do you predict would happen? What are the limitations of visual inspection as a diagnostic tool for cancer?

Rate of cancer growth: Doubling time It takes about 30 doubling times for a cancer cell to form a tumour that is large enough to be felt through the skin with hands. Calculate how many months it would take for the cells in the picture to form a tumour that could be felt if the doubling rate is two months. How many cancer cells would there be?

Learning goals We are learning what is cancer. We are learning the difference between the types of tumours. We are learning the differences between a normal cell and cancer cell.