Regulating Cell Cycle Cells move through cycle at different rates Muscle and nerve cells DO NOT DIVIDE! Bone marrow cells continuously make new blood cells Skin and digestive tract cells divide continuously Controls can be turned ON and OFF Regulatory proteins Protein CYCLIN regulates the cell cycle in eukaryotes

Regulatory Proteins Internal and External Growth factors stimulate growth and division of cells Embryonic development Wound healing

Apoptosis Cells are made; cells also die Cells may die by damage or programmed cell death APOPTOSIS starts series of steps that lead to cell self-destruction

CANCER is Uncontrolled Cell Growth Cancer cells do not respond to regulatory signals Uncontrolled division Tumor ~ mass of cancer cells Benign cells do NOT spread to nearby tissue or other parts of the body Malignant cells DO spread to other tissues and destroys them Cancer cells take nutrients from other cells, block nerves, disrupt organ function

Cancer Cell GROWTH Abnormal cell growth Tumor forms Cancer cells spread via bloodstream or lymph vessels

How Cancer Spreads

Possible causes of cancer Defective ‘cell growth and regulation’ genes Possible causes: Smoking, chewing tobacco (lungs, mouth) Radiation UV exposure (melanoma/skin cells) Defective genes, such as p53 Heredity (genetic disposition) Viruses (HPV) Treatment: removal of cancer cells, radiation, pharmaceuticals (chemical compounds), gene therapy?

VIRUSES VIRUS ~ nonliving particle that can reproduce ONLY by infecting living cells Viruses ~ Latin for ‘POISON’ STRUCTURE OF VIRUS: Capsid ~ protein coat surrounding virus Allows virus to enter host cells by binding surface proteins DNA or RNA inside

Types of VIRUSES

VIRAL Replication

Types of viral replication Lytic infection ~ Virus enters bacterial cell, replicates, causes cell to burst (lyse) Lysogenic infection ~ Virus’s nucleic acid is inserted into host DNA RNA viruses ~ Common cold, HIV

Replication ~ FLU virus

Replication ~ HIV

Diseases caused by viruses