Cells: Why do they divide? Doing Life’s Work

animal cells plant cells bacteria cells Types of cells Prokaryote no organelles no nucleus animal cells Eukaryotes Organelles nucleus plant cells

Why study cells? Cells  Tissues  Organs  Bodies bodies are made up of cells cells do all the work of life!

The Work of Life Jobs that cells do to keep an organism alive… “breathe” O2 in and CO2 out Eat make energy build molecules remove wastes control internal conditions respond to external environment build more cells growth, repair, reproduction & development

Cells have 3 main jobs make energy make proteins make more cells need energy for all activities need to clean up waste produced while making energy make proteins proteins do all the work in a cell, so we need lots of them make more cells for growth to replace damaged or diseased cells

Cells have to work to live! They need to make more cells for growth repair reproduction To reproduce, repair & grow, the cell must… copy their DNA make extra organelles divide the new DNA & new organelles between 2 new “daughter” cells

What does Cell Division Repair? Dead/ injured cells Your body sheds millions of cells daily! All of these need to be replaced Broken bones, blisters, cuts. You need new cells to heal the break

Cell lifespans Not all cells are created equal, they all have a predetermined self-destruct time! red blood cells live 120 days liver cells live 200 days intestine lining cells live 3 days skin cells live 20 days stomach lining cells live 2 days brain cells live 30-50 years

Cell Division for: REPRODUCTION Cell Reproduction Asexual reproduction: involves only one parent, and the offspring all have identical DNA to the parent and each other Occurs in many single celled organisms, and ALL of your body cells except sex cells

Offspring are NOT identical REPRODUCTION Sexual Reproduction: sex cells called gametes contain only half of the DNA. DNA from two parents join to create offspring with characteristics from both parents Offspring are NOT identical

QUESTIONS - For you to answer: A cleaning product claims to kill 99.9% of all bacteria. Will a cleaned surface stay bacteria free forever? Explain your reasoning. What is the major difference between sexual and asexual reproduction? Why do cells divide instead of just getting bigger as organisms grow? Provide some evidence that suggest that not all cells in your body divide at the same rate (speed). At one time, Dr.’s transfused blood from younger individuals into the elderly. They believe that the younger blood would provide the elderly with more energy. Do older people have older blood?