Cell Growth and Differentiation Notes Biology - Ms. Spinale

Development is slow and generally results in permanent changes. Development begins at fertilization and ends at death.

Changes in Development Growth - an increase in the size of an organism due to an increase in the number of cells. Diffusion and osmosis don’t work in cells if they get too big. Exception = adipose cells (fat cells).

Changes in Development All the developing cells in the body contain the same set of DNA...the same set of 46 chromosomes. We have different types of cells in our bodies because different cells use different parts of DNA.

Changes in Development

Changes in Development Differentiation - changes in structure and function of cells within the organism. Senescence - aging. Leads to progressive and irreversible loss of function. Genetically controlled.

What prompts different types of cells to reproduce in an embryo? Coordinating Growth What prompts different types of cells to reproduce in an embryo? Internal factors - different types of cells contain different proteins. External factors - those cells secrete growth signals to nearby cells (induction).

Hormones coordinate the proportional growth of your body. Controlling Growth Contact inhibition - cells stop dividing when cells reach a certain population density (think about repairing a cut on your skin. Hormones coordinate the proportional growth of your body.

What happens if too much cell division takes place? Cancer What happens if too much cell division takes place? A tumor can form. If the tumor is cancerous, it may metastasize (spread).

Cancer Cancer results from cells that have lost their differentiated characteristics and grow uncontrollably. Scavenger cells in the immune system usually destroy these but some can escape and grow into a tumor.

Benign tumors are localized (do not spread) Cancer Cancer can be a result of genetic or environmental factors, or a combination of both. Benign tumors are localized (do not spread)

Oncogenes - cancer-causing genes. Malignant tumors release enzymes that allow them to spread to other parts of the body (metastasis). Oncogenes - cancer-causing genes. May result from mutations in normal genes (inherited) that regulate cell growth.

Cancer May result from infection by certain viruses (most viruses are not cancer-causing).

A sperm fertilizes an egg to create the first cell; the zygote. Reproduction Gametes - sex cells. Female = ova. Male = sperm. A sperm fertilizes an egg to create the first cell; the zygote. The zygote contains a complete set of DNA for an organism.

Reproduction

This zygote begins to divide through mitosis. Reproduction This zygote begins to divide through mitosis. Regulatory molecules get separated into different cells.

Soon, a hollow sphere forms; a blastula. Reproduction Soon, a hollow sphere forms; a blastula.

Will become placenta and umbilical cord. Reproduction The blastula contains cells that will eventually grow into the embryo. Blastula Will become placenta and umbilical cord. Will become embryo.

Reproduction These cells (embryonic stem cells) can differentiate into anything, it just depends on which regulatory molecules are present.

Reproduction

Differentiation occurs in several ways: Reproduction Differentiation occurs in several ways: Internal regulation - molecules inside the cell control different genes that determine the fate of the cell. Induction - tissues release molecules that influence nearby tissues.

The blastula starts to fold in to form a gastrula (gastrulation). Reproduction The blastula starts to fold in to form a gastrula (gastrulation). The layers of the gastrula are called germ layers. They will form into different cells.

At 8 weeks, we call the gastrula an embryo. Reproduction At 8 weeks, we call the gastrula an embryo. The cells continue to divide through mitosis and differentiate through internal and external controls. From 12 weeks to birth, the embryo is then called a fetus.

Reproduction