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MCAT Prep Biology

Subjects : mcat, science
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. Steroid hormones secreted from the adrenal cortex. The two major classes are teh mineralocorticoids and glucocorticoids. Aldosterone is the principal mineralocorticoid - and cortisol is the principal glucorcorticoid.






2. Movement across the membrane of a cell that does not require energy input from the cell. Passive transport relies on concentration gradients to provie the driving force for movement - and includes both simple and facilitated diffusion.






3. Specif ic defense of the body by antibodies - secreted into the blood by B- cells.






4. A small - extrachromosomal (outside the genome) - circular DNA molecule found in prokaryotes.






5. The reactants in an enzyme - catalyzed reaction. Substrate binds at the active site of an enzyme.






6. A protein that is associated with the plasma membrane of a cell - but that is not embedded in the lipid bilayer. Peripheral proteins typically associate with embedded proteins through hydrogen bonding or electrostatic interactions.






7. A thick muscular tube that connects the epididymis of the testes to the urethra. Muscular contractions of the vas deferns during ejaculation ehp propel the sperm outward. Severing of the vas deferens (vasectomy) results in sterility of the male.






8. The fertilization of an oocyte by more than one sperm. This occurs in some animals - but in humans - blocks to polyspermy exist (the fast block and the slow block) so that only a single sperm can penetrate the oocyte.






9. An ion channel that is opened or closed based on the binding of a specific ligand to teh channel. Once opened - the channel allows the ion to cross the plasma membrane according to its concentration gradient. An examples is the acetylcholine receptor






10. An integral protein that selectively allows molecules across the plasma membrane. See also entries under 'ion channel' - 'voltage - gated channel' - and 'ligand - gated channel'.






11. Active transport that relies directly on the hydrolysis of ATP.






12. A hormone derived from cholesterol. Steroids are generally hydrophobic and can easily cross the plasma membrane of cells - thus receptors for steroids are found intracellularly. Once this steroid binds to its receptor - the receptor - steroid complex






13. A receptor that responds to changes in temperature.






14. The movement of a hydrophobic molecule across the plasma membrane of cell - down its concentration gradient. Since the molecule can esialy interact with the lipid bilayer - no additional help (such as a channel or pore) is required.






15. Bacteria that have a thick peptido glycan cell wall - and no outer membrane. They stain very darkly (purple) in Gram stain.






16. A chemical secreted by a T cell (usually the helper Ts) that stimulates activation and proliferation of other immune system cells.






17. The deliberate exposure of a person to an antigen in order to provoke the primary immune response and memory cell production. Typically the antigens are those normally associated with pathogens - thus if the live pathogen is encountered in the future






18. The innermost layer of the eyeball. The retina is made up of a layer of photoreceptors - a layer of bipolar cells - and a layer of ganglion cells.






19. A method of DNA protection utilized by prokaryotes in which their large circular chromosome is coiled upon itself.






20. A short sequence of amino aids - usually found at the N- terminus of a protein being translated - that directs the ribosome and its associated mRNa to the membranes of the rough ER where trasnlation will be completed. Signal sequences are found on me






21. A poysaccharide found in the cell walls of fungi and in the exoskeletons of insects.






22. The nervous system of the gastrointestinal tract. It controls secretion and motility within teh Gi tract - and is linked to the central nervous system.






23. The amount of blood returned to heart by the vena cavae.






24. A nucleoside with one or more phosphate gropus attached. Nucleoside triphosphates (NTPs) are the building blocks of RNA and are also used as energy molecules - especially ATP. Deoxynucleoside triphosphates (dNTPs) are the building blocks of DNA; in t






25. A non - bony material that fills the hollow spaces inside bones. Red bone marrow is found in regiosn of spongy bone and is the site of blood cell (red and white) production. Yellow bone marrow is found in the diaphysis (shaft) of long bones - is most






26. A series of enzyme complexes found along the inner mitochondrial membrane. NADH and FADH2 are oxidized by tehse enzymes; the electrons are shuttled down the chain and are ultimately passed to oxygen and to produce water. The electron energy is used t






27. An **organic molecuel taht associates non - covalently with an enzyme - and that is required for the proper functioning of the enzyme.






28. The second major node of the cardiac conduction system (after the SA node). The cardiac impulse is delayed slightly at teh AV node - allowing the ventricles to contract just after the atria contract.






29. The valve that controls the release of urine from the bladder. It has an internal part made of smooth muscle (thus involuntary) and an external part made of skeletal muscle (thus voluntary).






30. The main air tube leading into the respiratory system. The trachea is made of alternating rings of cartilage and connective tissue.






31. Aromatic bases found in DNA and RNA that are derived from purine. They have a double rightn structure and include adenine and guanine.






32. The division of the autonomic nervous system known as the 'resting and digesting' system. It causes a general decrease in body activities such as heart rate - respiratory rate - and blood pressure - and an increase in blood flow to the GI tract and d






33. The liquid portion of blood; plasma contains water - ions - buffers - sugars - proteins - etc. Anything that dissolves in blood dissolves in the plasma portion.






34. One of the three primary (embryonic) germ layers formed during gastrulation. Ectoderm ultimately forms external structures such as the skin - hair - nails - and inner linings of the mouth and anus - as well as the entire nervous system.






35. The outer ring of cells of a blastocyst. The trophoblast takes part in the formation of the placenta.






36. An organs in the abdominal cavity with two roles. The first is an exocrine role: to produce digestive enzymes and bicarbonate - which are delivered to the small intestine via the pancreatic duct. The second is an endocrine role: to secrete insulin an






37. A trop hormone produced by the anterior pituitary gand that targets the adrenal cortex - stimulating it to relase corisol and aldosterone.






38. A neuron that arries information (action potentials) to the central nervous system; a sensory neuron.






39. Something that increases the rate of a chemical reaction by reducing the activation energy for that reaction. The free energy of reaction remains unchanged.






40. A type of white blood cell; leukocytes are either B or T cells and are involved in disease defense.






41. Movement that is directed by chemical gradients - such as nutrients or toxins. (seen in some bacteria)






42. An organism that can only survive in the absence of oxygen (anaerobic metabolism); oxygen is toxic to obligate anaerobes.






43. A flexible piece of cartilage in the larynx that flips downward to seal teh trachea during swallowing.






44. An RNA polymerase that creates a primer (made of RNA) initiate DNa replication. DNA pol binds to the primer and elongates it.






45. A carrier protein that transports two molecules acrss the plasma membrane in opposite directions.






46. Inhibitory postsynaptic potential; a slight hyperpolarization of the postysynaptic cell - moving the membrane potential of that cell further from threshold.






47. The tubes that carry urine from the kindeys to the bladder.






48. A haploid but immature cell resulting from the second meiotic division f spermatogenesis. Spermatids undergo significant physical changes to become mature sperm (spermatozoa).






49. A diploid cell formed by the fusion of two gametes during sexual reproduction.






50. A neuron that carries information (action potentials) away from the central nervous system; a motor neuron.