Chapter 9 - The cell cycle and regulation PDF

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The cell cycle and regulation...

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Chapter 9 The cell cycle and regulation Cell cycle: An orderly set of stages from the first division of a eukaryotic cells to the time the resulting daughter cells divide. 

Just prior to the next division

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Cell grows larger

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Number of organelles doubles

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DNA is replicated.

Main stage of cell cycle:  Interphase  Mitotic stage Cytokinesis: it is the movement of DNA molecules that allows cells to divide. Interphase:  Most of the cell cycle is spent in interphase.  Cell perform its usual functions.  Nerve and muscle cell do not complete the cell cycle.  Time spent in interphase varies by cell type. G1 Phase: 

Cell is in recovery from previous cell division.

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Cell double organelles.

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Cell grows in size.

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Cell accumulates raw materials from DNA synthesis.

If DNA is damaged, apoptosis will occur. Otherwise, cell is committed to divide when growth signals are present.

Apoptosis:

Necrosis:

Cell death that is generally triggered by

Cell death triggered by external factors or

normal healthy processes in body.

disease.

S- Phase: 

DNA replication takes place.

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Protein associated with DNA are synthesized.

G2 Phase: 

Mitosis will occur if DNA has replicated properly.

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Apoptosis will occur if the DNA is damaged and can not be repaired.

Mitotic stage: 

Mitosis: o Nuclear division o Daughter chromosomes are distributed by the mitotic spindle to two daughter nuclei.

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Cytokinesis: o division of cytoplasm

Control of the cell cycle:  Signal is a molecule that influences the activities of a cell.  Cell cycle is controlled by internal and external signals. 

External signals: o Growth factors are signalling proteins received at the plasma membrane. Ex. Signaling peptide.

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Internal signals: o Family of proteins called cyclin increase and decrease as the cell continues. o Specific cyclins may be present for the cell to proceed one stage to the next. o Without cyclins, the cell cycle stops at G1, M or G2. o Damage by solar radiation or X-rays is repaired at the G2 checkpoint.

Apoptosis is programmed to cell death. It does not poison the cell, nor it is dangerous. In fact, it is organized cell death. It involves a sequence of cellular events that bring about the destruction of the cell. Enzymes called caspases causes apoptosis. Mitosis and apoptosis are opposing forces. Prophase:  Nucleus starts to disappear.  Spindle fibres begin to generate. Angiogenesis is the development of new blood vessels. DNA replication: Animal cells cytokinesis: cleavage furrow Plant cells cytokinesis: cell plate Cancer and tumor: Cancer is the abnormal growth of cells and tumor is the abnormal growth of tissues. Benign

Malignant

 Not cancerous

 Cancerous

 Does not invade neighbouring tissue

 Really invade neighboring tissue

or spread. Characteristics of cancer cells:  Lack of differentiation  Have abnormal nuclei  Does not undergo apoptosis  Undergo metastasis (development of secondary malignant growths)

 Undergo angiogenesis (development of new blood vessels) Two types of gene may be mutated when the balance is upset, which cause cancer:  Oncogenes- (proto- oncogenes)  Tumor suppressor gene codes for proteins Other causes of cancer- telomeres: o Chromosome have normally special material at each end called telomeres. o Mutations in telomerase gene allows cancer cells to divide. Telomerase is an enzyme that maintains the length of telomeres.

Telophase is the first of cell division between anaphase and interphase in which the chromosome and chromatids move to opposite ends to form two cell nuclei....