Figure 11.1 Each of us, like these other large multicellular organisms, begins life as a fertilized egg. After trillions of cell divisions, each of us develops into a complex, multicellular organism. (credit a: modification of work by Frank Wouters; credit b: modification…
Cell Division Prokaryotes have a single circular chromosome composed of double-stranded DNA, whereas eukaryotes have multiple, linear chromosomes composed of chromatin, all surrounded by a nuclear membrane. The 46 chromosomes of human somatic cells are composed of 22 pairs of…
LEARNING OBJECTIVES In this section, you will explore the following question: Prokaryotes, such as bacteria, propagate by binary fission. For unicellular organisms, cell division is the only method to produce new individuals. In both prokaryotic and eukaryotic cells, the outcome…
LEARNING OBJECTIVES In this section, you will explore the following question: Connection for AP® Courses Cancer results from unchecked cell division caused by a breakdown of the mechanisms that regulate the cell cycle. The loss of control begins with a change…
LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses Each step of the cell cycle is closely monitored by external signals and internal controls called checkpoints. There are three major checkpoints in the cell cycle:…
LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses The cell cycle describes an orderly sequence of events that are highly regulated. In eukaryotes, the cell cycle consists of a long preparatory period (interphase) followed…
LEARNING OBJECTIVES In this section, you will explore the following question: Connection for AP® Courses All organisms, from bacteria to complex animals, must be able to store, retrieve, and transmit genetic information to continue life. In later chapters, we will explore…
Figure 10.1 A sea urchin begins life as a single cell that (a) divides to form two cells, visible by scanning electron microscopy. After four rounds of cell division, (b) there are 16 cells, as seen in this SEM image. After many…
Signaling Molecules and Cellular Receptors Cells communicate by both inter- and intracellular signaling. Signaling cells secrete ligands that bind to target cells and initiate a chain of events within the target cell. The four categories of signaling in multicellular organisms…
LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses Cell signaling allows bacteria to respond to environmental cues, such as nutrient levels and quorum sensing (cell density). Yeasts are eukaryotes (fungi), and the components and…