Tutor profile: Emily M.

Draw the chemical structure of water. Explain the polarity and special qualities of water.

Water is a polar molecule. This means that the electrons are shared unequally. The oxygen has more elecromegnativity and hogs more of the electrons, making it partially negative. The hydrogen end is partially positive. This polarity gives water molecules the ability to dissolve other charged particles like salts and polar molecules. Water’s polarity also gives it the ability to create hydrogen bonds which gives water lots of special qualities like capillary action, cohesion.

Describe the plasma membrane. What are the main components? How does it function? Why is it called a semipermeable membrane? Include the concepts of hydrophilic and hydrophobic in your answer.

The plasma membrane is made of a phospholipid bilayer with proteins embedded in it. Two other main components of the membrane are cholesterol and the glycocalyx. The plasma membrane is a semipermeable membrane that separates the contents of the cell from the extracellular fluid. Semipermeable means that it can selectively allow certain substances in or out. The phospholipids have a hydrophilic (or water loving) head, and a hydrophobic (or water “fearing”) tail. The hydrophobic tails line the inside of the membrane while the hydrophilic heads face the extracellular matrix on the outside and the cytoplasm on the inside. This orientation of phosholipids creates a region of hydrophobicity that aids in the membrane's semipermeability.

Describe the differences between thick skin and thin skin.

There are several differences between thick skin and thin skin. First, thin skin has four epidermal layers; the Straum Basale, Stratum Spinosum, Stratum Granulosum, and Stratum Corneum. Thick skin has an additional layer, called the Stratum Ludicum which lies superficial to the Stratum Granulosum and deep to the Stratum Corneum. The second main difference between thick and thin skin is thick skin has a much thicker Stratum Corneum than thin skin. Thick skin is only found on the palms of our hands and soles of our feet and contains epidermal ridges which increase the overall surface area of the epidermal layer. Thick skin does not have hair follicles or sebaceous glands.