Unit 2: Tissues, Organs, and Systems. The Cell Cycle

Transcription

1 Unit 2: Tissues, Organs, and Systems The Cell Cycle

2 Cells All living things are made up of one or more cells. An adult human is made up of approximately 100 trillion cells. Cells are the structural and functional unit of all living things. Cells come from living cells. The cells in living things are responsible for many cellular processes such as:

3 Cellular respiration Process that takes place in cells that requires oxygen and releases energy for use within cell. Photosynthesis Process that takes place in plant cells that requires sunlight to store energy in sugars. Osmosis The diffusion of water across a semi-permeable membrane from an area of high concentration of water to an area of low concentration of water. Reproduction Process that takes place for cells to create new cells.

4 Write the following question into your notebook and then check your answer when you are finished your work. 1. What are some of the cell processes that occur inside cells? Labelling an animal cell

5 Mitosis During an organism's lifetime, cells will reproduce to: promote growth replace old or dying cells repair damaged cells Another name for the repairing of injured cells is regeneration.

6 Before cell division can take place, the genetic material of the cell must duplicate. Surrounding the nucleus is a nuclear membrane that controls the exchange of materials between the nucleus and the cytoplasm. The nucleus has one or more nucleoli. During mitosis (The process by which duplicated genetic material divides into two identical sets of chromosomes) new cells are produced with a complete set of DNA (Deoxyribonucleic acid - a molecule that determines the inherited characteristics of an organism). Mitosis is important because it ensures that the genetic material in the daughter cells (Two cells produced during mitosis of the parent cell) is identical to the parent cell (original cell).

7 Interphase The phase before mitosis begins is called interphase. During this phase the cell is carrying out normal cellular activities. The genetic material appears as long, thread-like fibres called chromatin. Close to the end of interphase, the chromatin shortens and thickens into chromosomes and in animal cells, the centrioles duplicate.

8 Animal cell in the interphase stage. The dark, spherical nucleolus can be seen in the nucleus. The chromatin has not yet condensed.

9 » (1) Chromatid- one of the two identical parts of the chromosome» (2) Centromere - the point where the two chromatids touch, and where the microtubules attach.» (3) Short arm.» (4) Long arm. The chromatin is coiled up to form double stranded chromosomes. The two halves of the chromosome are called chromatids and are held together by a centromere.

10 Write the following question into your notebook and then check your answer when you are finished your work. 2. What happens during the process of mitosis? 3. True or False: Interphase is the first phase of mitosis.

11 Stages of Mitosis The four phases of mitosis are: Prophase Metaphase Anaphase Telophase Even though mitosis has been divided into four phases, it is a continuous process with cells constantly going through changes.

12 Prophase In the first part of prophase, the centrioles move to opposite poles (sides) of the nucleus. The chromatin appears to thicken and become shorter and the chromosomes are visible. Eventually the nucleolus and the nuclear membrane will disappear during this phase. Spindle fibres will form and connect between the two centrioles that are moving to opposite poles of the animal cell.

13 An animal cell in the prophase stage of mitosis. The two centrioles are moving to opposite poles of the cell.

14 Metaphase In metaphase, the chromosomes line up in the middle (or equator) of the cell. The spindle fibres are attached to the centromere of the chromosomes at one end and the centrioles at the other end. They help guide the chromosomes towards the poles.

15 An animal cell in the metaphase stage of mitosis. The chromosomes are lined up along the equator of the cell.

16 Anaphase In anaphase, the chromatids separate at the centromere to produce two identical single stranded chromosomes. The chromosomes move to opposite poles of the cell during this phase.

17 An animal cell in the anaphase stage of mitosis. The chromosomes are beginning to separate.

18 Telophase In telophase, the spindle fibres begin to disappear, the nuclear membrane reforms, and nucleolus reappear. The chromosomes begin to uncoil to form thin strands of chromatin. Two distinct nuclei can be seen and the cell is ready to divide.

19 An animal cell in the telophase stage of mitosis. Two separate nuclei can be seen with the cell membrane beginning to pinch inwards.

20 Cytokinesis Cell division usually begins during telophase in animal cells and continues after mitosis. Cytokinesis is the division of the cytoplasm and organelles. During cytokinesis in animal cells, the cell membrane pinches inward at the equator of the cell producing a furrow. The furrow continues to pinch inward until two daughter cells form.

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22 Tip The order of the phases of mitosis (with interphase added) can be remembered with the following mnemonic device: I Point My Arm Towards Interphase is not part of mitosis, but prophase, metaphase, anaphase, and telophase are the four phases of mitosis in sequence.

23 Write the following question into your notebook and then check your answer when you are finished your work. 4. a) Write the numbers from one to eighteen in your notes. Next write the name of the phase (interphase, prophase, metaphase, anaphase, telophase) for each of the numbered cells in the image below. b) Which phase occurs most frequently?

24 Resources Interactive animal cell mitosis Mitosis simulation

25 The Cell Cycle The cell goes through a continuous process of interphase, mitosis, and cell division called the cell cycle. The cell spends most of its time in interphase where is goes through rapid growth, DNA synthesis, and preparation for cell division. The cell spends the least amount of time going through mitosis and cytokinesis.

26 Parts of the cell cycle include: G1 phase has rapid growth and metabolic activity; S phase is DNA synthesis and replication; G2 phase includes centrioles replication and cell prepares for division; and mitosis and cytokinesis

27 Lifespan of Some Human Cells Cell Type red blood cells stomach lining cells skin epidermal cells pancreas cells bone cells sperm cells brain cells Lifespan 120 days 2 days 2-4 weeks 1 year or more years 2-3 days years

28 Write the following question into your notebook and then check your answer when you are finished your work. 5. Describe some of the things occurring during interphase. Reference Interactive cell cycle

29 Questions and answers 1. What are some of the cell processes that occur inside cells? Some of the cell processes occurring inside the cell are cellular respiration, osmosis, reproduction, and photosynthesis. 2. What happens during the process of mitosis? During the process of mitosis the genetic material (that was replicated during interphase) divides into two identical sets of chromosomes.

30 3. True or False: Interphase is the first phase of mitosis. False -Interphase occurs before the process of mitosis. The cell is carrying out normal cellular activities. 4. a) 1.metaphase, 2.prophase, 3.telophase, 4.interphase, 5.interphase, 6.interphase, 7.anaphase, 8.interphase, 9.anaphase, 10.interphase, 11.metaphase, 12.telophase, 13.interphase, 14.prophase, 15.interphase, 16.interphase, 17.metaphase, 18.interphase b) The phase that occurs most frequently is interphase.

31 5. Describe some of the things occurring during interphase. During interphase the cell is growing, carrying out metabolic activities, synthesizing and replicating DNA, replicating the centrioles, and preparing for cell division.