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Chapter 7 : Cells Maintain Their Internal Environments
This chapter discusses how cells sense and respond to their environments, and also talks about various kinds of transport proteins involved in moving substances in and out of cells. The cell membrane determines whether energy is required to transport something and some of the many proteins embedded in the cell membrane are transport proteins. There are different types of transport proteins for different substances and situations. This chapter discusses how transport proteins function to transmit one's nerve impulses and make the heart beat and how disturbances in ion gradients can disrupt these critical body functions. The family members with hereditary heart failure have an altered form of the regulatory protein with a shape that cannot be phosphorylated. Without the phosphate group, the regulatory protein constantly inhibits the pump. Lactose intolerance results from a lack of the enzyme lactase that breaks the complex milk sugar lactose into its simple- sugar components, glucose and galactose. Water-salt imbalance also explains the symptoms of people who have cystic fibrosis, the most common fatal inherited disease of Caucasians. Water follows solutes in the body. Water will move across membranes and through aquaporins, when possible, to maintain osmotic balance in various cell compartments.