Cell Cycle A cell is very small with an average size of 1/100 th of a millimeter

Cell Cycle A human is made of about 10 trillion cells. But the number of bacteria cells both on and in one human is more than that!!!

Each fertilized cell DIVIDES and Divides and DIVIDES and DIVIDES.

Development of a Frog Egg Early development in a frog egg illustrates how a single egg develops hundreds of cells through division.division

Why Are Cells small? Cells are small to let materials easily and quickly diffuse into all parts of the cell. Which materials diffuse in? ____________________________ Cells are small to let materials easily and quickly diffuse out of all parts of the cell. Which materials diffuse out? ____________________________ Glucose and oxygen Carbon dioxide and wastes

A cell grows to its optimal size and then it divides in half. Each half will form a new cell that grows until it reaches its optimal size, and then it too will divide in half.

Exception A bird’s egg is one large cell. The yolk is a food source for the growing embryo. How is it possible for a bird’s egg to function when it is so large? Food is already present—diffusion isn’t needed to meet the nutritional needs of cell

1 parent cell divides into 2 daughter cells. When the cell divides in half, the DNA (genetic material) and cytoplasm must be divided evenly

A structure found in the nucleus of cells Each chromosome is one molecule of DNA wrapped around proteins Chromosomes Proteins DNA

Cells and Chromosomes Each cell contains a nucleus with chromosomes. Each species has a characteristic number of chromosomes. Humans have 46 chromosomes in the nucleus of each of their cells (23 chromosomes from each parent)

The Cell Cycle Interphase: Longest part of cell cycle (90%). This is when the cell is “doing its job”. –Cell grows; proteins and organelles are made –At the end of Interphase the cell gets ready to divide by copying each of the chromosomes Interphase Start of Cell Division

Cell Division Mitosis (4 phases) = division of the cell’s nucleus

What happens? –Chromosomes can be seen in the nucleus (they look like dark spaghetti) –Each chromosome is made up of two identical copies, attached together in the middle.

Spindles - Fan-like structures grow out from the opposite ends of the cell The nucleolus disappears. The nuclear envelope breaks down*.down*. Centrioles Sister Chromatids

Chromosome DNA Interphase Mitosis Cell Division

Chromosomes line up at the center of the cell. Each chromosome is attached to a spindle fiber at the center.

Anaphase –Spindles shorten -- causing the chromosomes to move towards opposite ends of the cell near the poles of the spindles*.spindles*.

Telophase –Chromosomes gather at either end of the cell and begin to lose their shape. –A nuclear envelope forms around each group of chromosomes. –Spindle fibers break apart.

Division of cytoplasm Occurs at same time as telophase Cell membrane pinched into two parts with one nucleus and an equal number of organelles in each part. New cell membrane forms around each cell*.each cell*

The Whole Process*Process*

The Purpose of Cell Division Multicellular organisms = growth, development and repair

What Happens when there are Problems with the Cell Cycle?

Cancer is a family of diseases. Some are relatively easy to cure, others are fatal. –All types of cancer involve a break-down in the normal cell cycle. –All cancer cells divide at a rapid rate indefinitely without stopping.

Usually, a cell that does not respond to the cell cycle controls is destroyed. If not, a tumor forms = a mass of abnormal cells developing within a tissue. Cells are disorganized and grow irregularly.

Benign tumors - remain at original site, are non-invasive and can be surgically removed. They do not spread to other parts of the body. Malignant tumors - cause cancer--cells invade and disrupt functioning of organs. These cells usually contain an abnormal number of chromosomes.

Types of tumors (continued) Metastases - Cancer cells (depending on type) may be invasive. Cells from a tumor may break off and spread through the body in blood cells and invade other organs*. organs*.

Types of Cancers Leading cancers in the USA –Bladder Cancer Bladder Cancer –Lung CancerLung Cancer –Breast Cancer Breast Cancer –MelanomaMelanoma –Colon and Rectal Cancer Colon and Rectal Cancer –Non-Hodgkin LymphomaNon-Hodgkin Lymphoma –Endometrial Cancer Endometrial Cancer –Pancreatic CancerPancreatic Cancer –Kidney (Renal Cell) Cancer Kidney (Renal Cell) Cancer –Prostate CancerProstate Cancer –Leukemia Leukemia –Thyroid CancerThyroid Cancer

In USA: 1 of 4 deaths is caused by cancer. What causes cancer cells to form? –Smoking tobacco –Exposure to radiation –Certain viruses –Environmental factors –Genetic factors

First step (usually) is surgical removal of tumor. If all cancer cells are removed and the affected organ is not damaged the person is considered cured. Other treatments: –Radiation therapy –Chemotherapy Used separately or together

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