KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. (unicellular organisms divide to reproduce

The cell cycle represents the life cycle of a cell. The cell cycle has three main stages: (1) INTERPHASE (a) G1: cell grows, organelles double in number; cell does its job (b) S (DNA synthesis) DNA is copied (c) G2 : More growth; (2) Mitosis: division of the cell’s DNA (3) Cytokinesis (cell divides into 2 cells)

Why do cells divide? They become too large The volume of the cell increases faster than the surface area Cells need large surface area (cell membranes) to move things in and out

2. To make more cells so the organism can grow Why do cells divide? 2. To make more cells so the organism can grow Example: a growing baby needs more skin cells! 3. To replace old, worn out cells Cells reproduce at different times depending on their jobs.

Some cells do not divide in adults: Brain cells Nerve cells Muscle cells Stem Cells are the focus of much research to find ways to create new cells of these types. Stem cells are cells that can produce or become any type of cell.

This is called the diploid number & is abbreviated 2n KEY CONCEPT The goal of mitosis/cytokinesis is to make 2 identical daughter cells. The number of chromosomes in a mitotic cell is double the number in a sperm or egg cell This is called the diploid number & is abbreviated 2n One mitotic 2n mother cell produces 2 identical daughter cells which are also diploid or 2n

The product… Mitosis is a form of asexual reproduction that makes identical body cells It results in two 2n daughter cells that are genetically identical to each other

KEY CONCEPT To remain healthy, mitosis must be controlled.

Apoptosis is programmed cell death. It’s normal for healthy cells cell produces self-destructive enzymes Example: Webbing between Fingers in fetus webbed fingers

In cancer, mitosis is uncontrolled. Cancer cells divide constantly and form clumps called tumors. Benign tumors: remain clumped; can be removed. Malignant tumors: break apart (metastasize) and can form tumors in other parts of the body. cancer cell bloodstream normal cell

Cancerous cells do not carry out normal functions. Cancerous cells come from normal cells with damage to DNA. Carcinogens are substances known to promote cancer. Examples: Standard cancer treatments typically kill both cancerous and healthy cells. (Radiation & chemotherapy) People who have sunburns have an increased risk of cancer: Too much sun exposure can cause cancer due to radiation exposure from the sun which alters your DNA in a harmful way UV light from the sun can alter DNA in a harmful way