Cell Growth

Learning Objectives Explain how cell division solves the problem of cell growth

Calculating Surface Area B A Surface Area = Area X # of sides Area = A X B

Calculating Volume Volume = Length X Height X Width

Surface Area to Volume Surface area - 6mm2 Volume - 1mm3 Surface area - 24mm2 Volume - 8mm3 Surface area - 96mm2 Volume - 64mm3 As the cell grows larger, the cell’s volume increases faster than the surface area, causing problems for the cell.

Limits to Cell Growth Larger cells have more trouble moving nutrients and wastes across the membrane DNA overload - large cells cannot make enough DNA to meet it’s needs

When animals grow larger, do their cells increase in size or do they produce more cells?

Cell Division Before a cell becomes too large, it divides forming two “daughter” cells - Cell Division

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Cell Division

Learning Objectives Explain the main events of the cell cycle

The Cell Cycle During the cell cycle, a cell grows, prepares for cell division (interphase) and divides to form two daughter cells (M phase).

2 Stages of the Cell Cycle Stage 1 = Interphase Stage 2 = Mitotic phase

Interphase 90% of a cell’s time may be spent in interphase. Three parts: G1, S and G2 phases G1 phase - Cells grow and replicate organelles. S phase - DNA synthesis occurs and chromosomes are replicated. G2 phase - additional growth and preparation for mitosis. 90% of a cell’s time may be spent in interphase.

Mitotic phase (M phase) Two main stages: Mitosis and cytokinesis Mitosis - division of the cell nucleus Cytokinesis - division of the cytoplasm

Purpose of The Cell Cycle The purpose of the cell cycle is to regulate cell division, which replicates each parent cell to form two identical daughter cells.

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Phases of Mitosis

Learning Objectives Describe what happens during the four phases of mitosis

Mitosis Mitosis - division of the cell nucleus Mitosis is divided into four phases: Prophase Metaphase Anaphase Telophase

Interphase Cell grows and replicates its DNA and centrioles. Nucleolus Centrioles Chromatin Nuclear Envelope Cell grows and replicates its DNA and centrioles. Prepares for mitosis.

Prophase Chromatin condenses into chromosomes. Spindles Centrioles Nuclear Envelope Chromatin condenses into chromosomes. Centrioles separate and spindles begin to form. Nuclear envelope breaks down.

Metaphase Chromosomes line up across the center of the cell. Centromere Spindles Chromosomes line up across the center of the cell. Each chromosome is connected to the spindle fiber at its centromere.

Anaphase Sister Chromatids Paired chromosomes (sister chromatids) separate into individual chromosomes. Chromosomes move to opposite ends of the cell.

Telophase Two nuclear envelopes form around chromosomes Chromatin Nuclear Envelope Two nuclear envelopes form around chromosomes Chromosomes uncoil into chromatin.

Cytokinesis Cytokinesis - division of the cytoplasm. Two daughter cells with an identical set of chromosomes are formed.

YouTube Video Mitosis

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Regulation of the Cell Cycle

Learning Objectives Describe how the cell cycle is regulated Explain how cancer cells are different from normal cells

Functions of Cell Division Reproduction - formation of an organism, increasing the population. Growth - development of multicellular organisms. Repair - repair and renew cells that die (apoptosis) from normal wear or damage.

Regulating the Cell Cycle Not all cells move through the cell cycle at the same rate. Cells of the skin and digestive tract divide rapidly. Adult muscle and nerve cells do not divide.

How is the cell cycle regulated? Internal Regulators: Proteins that respond to events inside the cell. Ex. Cyclin External Regulators: Proteins that respond to events outside the cell. Ex. Growth Factors

Uncontrolled Cell Growth Cancer - a disorder in which some of the body’s own cells lose the ability to control growth.

Cancer Divide uncontrollably Form masses called tumors Damage surrounding tissue Break loose from tumors and spread throughout the body - Metastasis

Cancer Facts and Figures Cancer is a leading cause of death worldwide. Deaths caused by cancer this year: 7,602,215

Stem Cells Stem cells - unspecialized cells that have the potential to become a variety of cell types. Every cell in an organism was produced by mitosis from stem cells.

Cancer: Unregulated Cell Division YouTube Video Cancer: Unregulated Cell Division

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