errata 24235

modules/m66479/index.cnxml

@@ -47,7 +47,7 @@
 <section id="fs-id2571351">
 <title>Positive Regulation of the Cell Cycle</title>
 <para id="fs-id2338602">Two groups of proteins, called <term id="term-00004">cyclins</term> and <term id="term-00005">cyclin-dependent kinases</term> (Cdks), are termed positive regulators. They are responsible for the progress of the cell through the various checkpoints. The levels of the four cyclin proteins fluctuate throughout the cell cycle in a predictable pattern (<link target-id="fig-ch10_03_02"/>). Increases in the concentration of cyclin proteins are triggered by both external and internal signals. After the cell moves to the next stage of the cell cycle, the cyclins that were active in the previous stage are degraded by cytoplasmic enzymes, as shown in <link target-id="fig-ch10_03_02"/> below.</para>
-<figure id="fig-ch10_03_02"><media id="fs-id1472126" alt="This graph shows the concentrations of different cyclin proteins during various phases of the cell cycle. Cyclin D concentrations increase in G subscript 1 baseline phaes, and decrease at the end of mitosis. Cyclin E levels rise during G subscript 1 baseline phase and fall during S phase. Cyclin A levels rise during S phase and fall during mitosis. Cyclin B levels rise in S phase and fall during mitosis.">
+<figure id="fig-ch10_03_02"><media id="fs-id1472126" alt="This graph shows the concentrations of different cyclin proteins during various phases of the cell cycle. Cyclin D concentrations increase in G subscript 1 baseline phase, and decrease at the end of mitosis. Cyclin E levels rise during G subscript 1 baseline phase and fall during S phase. Cyclin A levels rise during S phase and fall during mitosis. Cyclin B levels rise in S phase and fall during mitosis.">
 <image mime-type="image/jpg" src="../../media/Figure_10_03_02-820d.jpg" width="400"/>
 </media>
 <caption>The concentrations of cyclin proteins change throughout the cell cycle. There is a direct correlation between cyclin accumulation and the three major cell-cycle checkpoints. Also note the sharp decline of cyclin levels following each checkpoint (the transition between phases of the cell cycle), as cyclin is degraded by cytoplasmic enzymes. (credit: modification of work by "WikiMiMa"/Wikimedia Commons)</caption></figure><para id="fs-id1242469">Cyclins regulate the cell cycle only when they are tightly bound to Cdks. To be fully active, the Cdk/cyclin complex must also be phosphorylated in specific locations to activate the complex. Like all kinases, Cdks are enzymes (<emphasis effect="italics">kinases</emphasis>) that in turn phosphorylate other proteins. Phosphorylation activates the protein by changing its shape. The proteins phosphorylated by Cdks are involved in advancing the cell to the next phase. (<link target-id="fig-ch10_03_03"/>). The levels of Cdk proteins are relatively stable throughout the cell cycle; however, the concentrations of cyclin fluctuate and determine when Cdk/cyclin complexes form. The different cyclins and Cdks bind at specific points in the cell cycle and thus regulate different checkpoints.</para><figure id="fig-ch10_03_03"><media id="fs-id2106304" alt="This illustration shows a cyclin protein binding to a upper case C lower case d lower case k. The cyclin slash upper C lower d lower k complex is activated when a kinase phosphorylates it. The cyclin slash upper C lower d lower k complex, in turn, phosphorylates other proteins, thus advancing the cell cycle.">