The Cell Cycle Chapter 5

If your cells didn’t divide, you wouldn’t live All cells divide, so that you can live. How long does it take? Depends… Skin cells are replaced every 2 weeks Red blood are replaced every 4 months Liver cells are replaced every 1 to 2 years Some muscle tissues are replaced every 16 years

Mitosis Chromosomes condense at the beginning of mitosis. What do they look like before mitosis?

Vocabulary Check Chromosome – a strand of DNA. Histones – a protein that helps wind up the super long strand of DNA to prepare for mitosis. Centromere – middle hinge that holds original and replicated DNA together during mitosis. Chromatid – each end of the wound DNA and replicated DNA.

Stages of Mitosis

What if there’s a problem? The cell cycle is closely regulated. – External factors, such as growth factors and cell- cell contact. – Internal factors, such as specific proteins that help move cells through the cell cycle and eventually bring about apoptosis. Sometimes, cell division continues to happen, unregulated, regardless of internal and external factors.

Cancer Cancer is a disease characterized by unregulated cell division. – Benign tumors remain closely clustered together and are relatively harmless. – Malignant tumors tend to break away, or metastasize, and can move around the body, causing tumors elsewhere. Usually, cancerous cells have suffered damage to the genes and no longer perform necessary functions.

Asexual Reproduction Asexual reproduction is the creation of offspring from a single parent. – Does not include the joining of gametes – Offspring are mostly genetic copies of parent cell Binary fission is a type of asexual reproduction common to prokaryotes – End result is similar to mitosis, but process is slightly different

Multicellular Life Many cells add up to make a tissue – Tissues are groups of cells that work together to perform a similar function Many tissues add up to make an organ – Organs are groups of tissues that work together to perform a similar function Many organs add up to make an organ system – Organ systems are groups of organs that work together to perform a similar function

Specialized Cells Some cells are highly specialized to perform specific functions – Neurons are designed to transmit electrical impulses efficiently – Blood cells lack a nucleus so that they can carry more oxygen – Stem cells can develop into different types of cells depending on what is needed