Cell Division Chapter 3.1

Do Now What happens when you get cut? Explain in your own words what happens when you are cut and the healing process.

Cell division occurs in all organisms –Unicellular organisms (ex: bacteria) Binary fission- Division of 2 identical cells (clone) –Multicellular organisms (ex: US!) Mitosis Binary Fission Mitosis

Cellular Division Videos Binary Fission – _Q1iHfYhttps:// _Q1iHfY Mitosis – RhXl7w_ghttps:// RhXl7w_g

Cell division is involved in growth, development, and repair 1.All organisms start as a single cell a)Growth: limited by surface area (needs high ratio of surface area to volume) -Large organisms do not have larger cells than smaller organisms. (They just have more cells!!) -As an adult, you have about 100 trillion cells! b) Cells are limited in size: a)Nutrients in and wastes out through membrane. b)If cell grows too big, not enough material can cross the membrane fast enough c)So the Cell divides

Worksheet!!

Cell division is involved in growth, development, and repair Cont. c) Development: –Makes specialized cells- Cells modified (structure) for particular functions –Ex: blood cell, nerve cells, muscle cells (These cells have the same genetic material)

Cell division is involved in growth, development, and repair Cont. d ) Repair: –Heals cuts and any wounds –Cells divide (reproduce) and fill up space to close the wound. We are made up of 200 different types of cells As cells age and die, they need to be replace. Every minute, you lose 40,000 skin cells! Brain cells live long and do not divide often

DNA – deoxyriobonucleic acid A chemical that contains information for an organism’s growth and functions. –Has directions on how to make proteins! Double helix like a twisted ladder Eukaryotes: Located in nucleus!

Chromosome Structure DNA coils around histones (proteins) to form nucleosomes. This coils to form chromatin fibers. The chromatin fibers supercoil to form chromosomes!

We have 46 total chromosomes= 23 pairs

Question Even when you are done growing and development appears to stop, is cell division still occurring?