MCAT Biology Practice Exam Questions with Correct Answers Explained to Provide Complete Solutions for the Latest Updates

1. Glucose typically enters the cell through which mechanism? A. Simple diffusion through the cell membrane B. Facilitated diffusion through a carrier protein C. Pinocytosis through a channel protein D. Active transport by a glucose transport protein - AnsFacilitated diffusion through a carrier protein Glucose is too large and polar to move quickly through the cell membrane by simple diffusion. Typically, the concentration of glucose outside the cell is higher than inside the cell. Since glucose is moving down a concentration gradient by entering the cell, the process does not require ATP. Glucose typically enters cells by facilitated diffusion through a carrier protein. 2. Which type of membrane protein is most likely to be a hormone? A. Lipid-bound protein B. Peripheral protein C. Integral protein D. Steroid - AnsPeripheral protein Hormones move through the circulatory system, acting as signaling molecules to specific organs/cells. A steroid is not a membrane protein. An integral protein can not easily leave the cell membrane and would therefore be a poor signaling molecule. Lipid-bound proteins remain within the phospholipid bilayer by the fatty acid tails of phospholipids. They would also be poor signaling molecules. Peptide hormones like insulin and growth hormone interact with integral protein receptors in cell membranes. These hormones can be considered peripheral membrane proteins. 3. Pulmonary edema occurs when fluid builds up in the interstitium between the pulmonary capillaries and the alveoli, and eventually enters the alveoli. How do you decrease the risk of pulmonary edema? A. Decrease hydrostatic pressure and increase osmotic pressure B. Decrease hydrostatic pressure and decrease osmotic pressure C. Increase hydrostatic pressure and decrease osmotic pressure D. Increase hydrostatic pressure and increase osmotic pressure - AnsDecrease hydrostatic pressure and increase osmotic pressure Hydrostatic pressure is the pressure a liquid exerts on its container, and reflects the volume of liquid in a space. Osmotic pressure is the pressure required to prevent movement across a semipermeable membrane, and reflects the protein content of the blood. To decrease the risk of pulmonary edema, hydrostatic pressure exerted by the fluid must decrease, and osmotic pressure exerted on the fluid must increase. 4. At what point does crossing over between sister chromatids occur? A. During anaphase I of meiosis B. During prophase I of meiosis C. During anaphase II of meiosis D. During prophase II of meiosis - AnsDuring prophase I of meiosis Crossing over is a form of genetic recombination in which homologous chromosomes pair up and exchange pieces of their genetic material. Crossing over occurs in prophase I of meiosis, and is often referred to as synapsis. However, crossing over occurs between homologous chromosomes, and not between the sister chromatids of an individual chromosome. Sister chromatids are identical pieces of DNA joined at the centromere to make up one chromosome. 5. Your trachea has short hair-like cell process that moves the mucus. What is the name of these hair-like structures and which cytoskeletal elements form them? A. Cilia, microfilaments B. Villi, microfilaments C. Villi, microtubules D. Cilia, microtubules - AnsCilia, microtubules Villi are macroscopic foldings of tissue Microvilli are foldings of the cell membrane that increase the surface area of cell but are not responsible for movement Cilia are eyelash-like structures derived from microtubules, they are responsible for creating motion outside the cell. 6. An organic molecule has been isolated from the nucleus of a human cell. Nuclear magnetic resonance studies reveal the core structure of the molecule to be a six-membered ring containing carbon and nitrogen. The ring also expresses an amine group and a keto group, and is attached to a five carbon sugar moiety. No phosphate groups are noted. What is the most likely identity of the molecule