What specific molecules are secreted by cells and function to alter or regulate target-cell metabolism? O Receptors Procoagulants Hormones Immunoglobulins

What is the role of negative feedback in a cell-signalling pathway?     To switch off a signal once of the output reaches a certain threshold     To trigger the degradation of upstream signalling components     To amplify the output of a signal     To ensure a signal is transient

39 of 41 Which of the following statements best describes autocrine signalling? O A cell communication mechanism in which the signalling molecules bind to receptors located on the cell secreting the signalling molecules. A cell communication mechanism in which the signalling molecules bind to receptors located on adjacent cells. O A cell communication mechanism in which the signalling molecules are released into the circulatory system to bind to receptors located on cells in tissues some distance away. A cell communication mechanism in which the signalling molecules are peptide hormones. A cell communication mechanism in which the signalling molecules are steroid hormones.

Which of the following proteins serves a structural function (not an enzymatic function)? chymotrypsin thrombin elastase collagen trypsin