1.4 The Cell Cycle

Learning Goals

• Learn about the different life stages of a cell

• Learn about cell death, cell suicide, and cancer

Cells within the human body have finite life spans. The cell cycle controls the production (through interphase, mitosis, and cytokinesis) of new cells of a variety of different types.

Life Span of Cells

Cell Cycle Checkpoints: a point in the life of a cell when proteins determine whether cell division should or should not occur

There are 3 main checkpoints during the cell cycle:

1) G1 phase

2) G2 phase

3) Mitosis

Cell Cycle Checkpoints

What Controls Cell Division?

Cell division is controlled by proteins that send signals to cells. – This tells the cell to divide or not.

Cell division cannot occur if:– There are limited nutrients– DNA has not been replicated– DNA is damaged

Cell Death

ApoptosisNecrosis- “cell suicide”- Pre-programmed

in the cell - Proteins are made

with intensions of killing the cell

- “cell death”- Occurs in

damaged cells- Cells must leave

the cell cycle.

All contents of the cell are destroyed

The organelles are packaged and reused to construct other cells

Normal and healthy cells have controlled chemical reactions that determine when cell division should occur. When the cells die they are quickly replaced with new, healthy cells.

Normal Cells and the Cell Cycle

Cancer: cells with abnormal genetic material that are dividing uncontrollably and can spread to other body parts.

If the mutated cells are able to bypass the checkpoints in the cell cycle they may continue to replicate excessively and form a tumour.

Cancer and the Cell Cycle

Tumour: an abnormal clump of cells formed when cells divide repeatedly and excessively

Benign Tumour: a mass of cells (tumor) that lacks the ability to invade neighboring tissue or metastasize.

Malignant Tumour: not self-limited in its growth, is capable of invading into adjacent tissues, and may be capable of spreading to distant tissues.

Richard Jones lived in Manchester. As a postman, he was always very active as he got lots of exercise delivering the mail. Richard enjoyed being outside and getting up early, even in deepest darkest winter.

He was particularly fond of his two grandchildren – Jack and Harry – who he took to the football every Saturday. Richard had been a heavy smoker all his life. A few weeks after his 70th birthday, he developed shortness of breath and went to the doctor. It turned out he had lung cancer.

Case 1: Richard Jones

Katie Fitzgerald comes from Dublin. She has two children – George and Sarah – and a busy full time job as a journalist for the Irish Times. She loves her job as Features Editor and is always at her computer.

Kate eats organic food, and goes swimming twice a week. Both Kate’s mum and gran died of breast cancer. Kate developed breast cancer when she was 5,but because it was diagnosed early, she was successfully treated and now carries on her busy life.

Case 2: Kate Fitzgerald

David MacDougall was 65 when he found out he had bowel cancer. It had never occurred to him that he may develop cancer. He had an international reputation as an award-winning chef in Edinburgh’s Balmoral Hotel.

But David didn’t just enjoy cooking food – he also loved eating it. Haggis and sausages were his absolute favourite, and he ate them three times a day. The doctor had told him he should be careful with his weight, and eat a more balanced diet, but David found it hard to change.

Case 3: David Macdougall

• Read Section 1.4• Questions: pg. 45 # 1, 3-6• Complete Worksheet• Complete Chapter 1 Review• Cell Division Assignment

Homework