Bio 212 Exam 1 Possible Short Essay Questions with Correct Answers

What is the function of the plasma membrane? - Physical isolation of cell contents from extracellular fluid - Sensitivity to changes in the extracellular fluid - Structural support of the cell - Regulation of exchange of materials between the cell and the extracellular fluid Explain why the unique molecular structure of the phospholipid molecules form a bi-layer. Also, describe how small lipid-soluble substances cross and small water-soluble substances cross the membrane. - molecules are arranged so that the heads are at the cell surface and their tails are on the inside - ions and water soluble substances will not cross the lipid portion of the plasma membrane because the tails will not associate the water molecules Thoroughly describe the difference between facilitated diffusion and endocytosis. Be sure to include whether it is an active or passive process and what that means in regards to energy usage. facilitated diffusion: Lipid-insoluble substances helped by membrane carrier proteins (like swinging door) down a concentration gradient endocytosis: Cell membrane engulfs (wraps around) a molecule, organism, etc. forms a vesicle by pinching off and bringing the vesicle within. It is independent of concentration gradient f. diffusion: passive process (no ATP) endocytosis: active process (ATP) Name and describe the 3 modes of secretion for an exocrine gland cell. Give an example for each mode. merocrine: only a vesicle pinches off (ex: sweat glands) apocrine: top portion of cell pinches off (mammary glands) holocrine: whole cell burts (sebaceous gland cells) List specific changes that occur due to aging of the integumentary system. Then describe the effect the changes have on the skin. - epidermis thins as basal cell activity decreases, older people are now more prone to injury and infections - Langerhans cells decrease by 50 percent, weakens immunity and encourage skin damage - vitamin d3 decreases by 75 percent and weakens muscle and bones - glandular activity decreases, skin becomes dry/scaly, How are fingerprints formed? Epidermal ridges correspond to dermal papillae ridges Ridges and grooves prominent on plantar and palmar surfaces May be straight or whorls Pattern genetically determines, and small variations due to movement in womb