Biology Questions

The structural unit of compact bone is Osteons or Haverisan systems.

Epithelial tissue is made of layers of cells that cover the surfaces of the body that come into contact with the exterior world, line internal cavities, and form glands.

The four types of tissue in the body are epithelial, connective, muscle, and nervous. 

Receptors for hearing the organ of corti or the spiral organ is located in the the mammalian cochlea.

Improving muscular strength and endurance slows bone density loss.

Amino acids are the building blocks of proteins. There are about 21 essential amino acids in the human body like histidine, leucine, lysine... The general formula for amino acid is R-CH(NH2)-COOH.

Cytoplasm does not contains all the organelles.

All enzymes are proteins but all proteins are not enzymes since, enzymes are subset of proteins.

True, Stress is a factor that contributes to heart disease risk.

More factors that contributes to heart disease risk are blood pressure, cholesterol, smoking, physical inactivity and overeating.