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Cell Growth and Reproduction

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Presentation on theme: "Cell Growth and Reproduction"— Presentation transcript:

1 Cell Growth and Reproduction

2 Limitations on Cell Size
Diffusion Larger the cell, the longer it takes to get nutrients from outside the cell through diffusion. DNA Larger cells need more DNA to support the functions of the cell (i.e. protein synthesis).

3 Limitations on Cell Size
Surface Area to Volume Ratio Volume increases at a higher rate than surface area. As cell increases in volume, more nutrients are needed and more wastes are created. Surface area of the cell is not sufficient for the diffusion of nutrients and wastes.

4 Cell Division Occurs before the cell becomes too large to be efficient. Results in two cells which are identical to the original parent cell.

5 Chromosomes, Chromatin, and Sister Chromatids
Long strands of DNA wrapped around proteins called histones. Each groups of histones is called a nucleosome. Exist between times of division.

6 Chromosomes, Chromatin, and Sister Chromatids
Before a cell can divide, chromatin must be reorganized into tight coils called chromosomes. Appear before cell division and disappear soon after cell division is complete.

7 Chromosomes, Chromatin, and Sister Chromatids
Accurate transmission of chromosomes during cell division is critical, so before division chromosomes copy themselves. When copied, chromosomes form two sister chromatids that are exact copies of each other. The two sister chromatids are held together by a centromere.

8 Chromosomes, Chromatin, and Sister Chromatids

9 Cell Cycle Sequence of growth and division in a cell.
Divided into two parts: Interphase Mitosis

10 Interphase Growth period in which a cell spends most of its life.

11 Interphase 3 distinct divisions:
Cell grows and protein production is high. Cell copies its chromosomes and DNA synthesis occurs. Short period of growth during which mitochondria and other organelles are manufactured and cell parts needed for cell division are assembled.

12 Mitosis Period of nuclear division.
During mitosis, two daughter cells are formed. Each daughter cell contains a complete set of chromosomes. Following mitosis, the cytoplasm divides, separating the two daughter cells.

13 4 Phases of Mitosis Prophase Metaphase Anaphase Telophase

14 Prophase Longest phase of mitosis.
Long, stringy chromatin coils up into visible chromosomes. Nucleus disappears as the nuclear envelope and nucleolus disintegrate.

15 Prophase In animal cells, the centrioles migrate to opposite sides of the cell and the spindle forms between them. In plant cells the spindle forms without centrioles.

16 Prophase

17 Centrioles Small dark, cylindrical structures made of microtubules.
Located just outside the nucleus. Play a role in chromotid separation.

18 Spindle Football shaped, cage like structure consisting of thin fibers made of microtubules. Plays a vital role in separation of sister chromatids.

19 Metaphase Short Doubled chromosomes become attached to the spindle fibers by their centromeres. Chromosomes are pulled by the spindle fibers and begin to line up on the mid-line of the spindle.

20 Metaphase Each sister chromatid is attached to its own spindle fiber. Each of these spindle fibers extend to opposite poles to ensure that each new cell receives and identical and complete set of chromosomes.

21 Metaphase

22 Anaphase Beginning is marked by the separation of sister chromatids.
The centromeres split apart and chromatid pairs from each chromosome separate from each other. Chromatids are pulled apart by the shortening of microtubules in the spindle fibers

23 Anaphase

24 Telophase Begins as chromatids reach the opposite poles of the cell.
Many of the changes that occurred during prophase are reversed as the new cells prepare to exist independently.

25 Telophase Tightly wound chromosomes begin to unwind.
Spindle begins to break down. Nucleolus reappears. New nuclear envelope forms around each set of chromosomes. New double membrane begins to form between the two nuclei.

26 Telophase

27 Cytokinesis Division of the cytoplasm following telophase. Animals:
Towards the end of telophase, the plasma membrane pinches in along the equator and the two cells begin to separate.

28 Cytokinesis Plants: A structure called a cell plate is laid down across the equator of the cell. A cell membrane forms around each cell and new cell walls form on each new side of the cell plate until separation is complete.

29 Cytokinesis

30 Results of Mitosis Unicellular organisms produce two new single-celled organisms. Multicellular organisms produce groups of cells that work together as tissues to perform specific functions. Tissues further organize to form organs. Multiple organs form an organ system.

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