Which statements about the proteins and glycoproteins in cell surface membranes are correct? 1
They can allow cells to bond together to form tissues.
They can recognise messenger molecules like hormones.
2
3
They can be antigens and allow cell to cell recognition.
A
1, 2 and 3
B
1 and 2 only
С
1 and 3 only
2 and 3 only
D

Which of the following birds remained ancient looking in the miocene epoch? a. crows b. owls c. grouses d. none of the above

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit. there is a precise compatibility between the active site and the lactose molecule. specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed. reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.