Which of the following describes a positive feedback loop? When blood sugar concentration is too low, the endocrine system secretes hormones that increase blood sugar concentration to a normal level.

When the body senses that the heart rate is very high, it secretes hormones that decrease the heart rate.

When blood sugar concentration is too high, the endocrine system secretes hormones that decrease blood sugar concentration to a normal level.

When someone is exercising intensely, the body secretes hormones that increase oxygen supply for cellular respiration.

Which statements about the fluid mosaic structure of a membrane are correct? select the three correct statements.which statements about the fluid mosaic structure of a membrane are correct? select the three correct statements.the framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center.because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.the diverse proteins found in and attached to membranes perform many important functions.the kinky tails of some proteins keep the membrane fluid by preventing the component molecules from packing solidly together.membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer.