The Correct Answer is D
Eyes that do not require corrective lenses or refractive surgery to achieve good quality of vision are considered to have a normal ‘neutral’ refractive state that we call
emmetropia. Although emmetropic eyes require no refractive correction, subtle refractive errors and aberrations are still present that are significant for the quality of vision. Equally important to the presbyopic patient are the subtle refractive errors and aberrations experienced during accommodation.
Myope:
- The eye at rest has a dioptre power that is too strong and/or the eye is longer than the non-
accommodated focal length of the refractive elements (cornea + lens). The light rays from distance focus within the eye and not on the macula.
- A near sighted person is helped with minus lenses.
Symptoms: Does not see well at distance but sees well near objects.
Answer: C
Proteins targeted for the secretory pathway most commonly begin with translocation from the cytoplasm across the lipid bilayer into the lumen of the endoplasmic reticulum. It must then pass through a number of compartments including the Golgi apparatus where they are further processed and sorted and end up in a secretory vesicle or lysosome.
Answer: a, b
The prototypic intracellular messenger is cAMP. To function as a mediator, the concentration of cAMP must change rapidly. In resting cells, cAMP is continuously being degraded by a specific enzyme, cAMP phosphodiesterase. cAMP levels can increase 10-fold or more within seconds of receptor binding through activation of adenylate cyclase. cAMP acts as an allosteric regulator, and most, if not all, of its actions are mediated by activation of cAMP-dependent protein kinase A. cAMP is not the only cyclic nucleotide active as an intracellular messenger. Most animal cells also produce cGMP. Intracellular calcium ions also serve as second messengers in a large number of cells.
Answer: D
The cytoskeleton is a collection of filamentous protein structures that allow cells to assume and maintain a variety of shapes, to produce directed movement of organelles within the cell, and to affect movement of the entire cell relative to other cells. These multiple activities depend upon three main types of filaments: actin filaments, intermediate filaments, and microtubules.
Answer: b, c
Mitochondria are the major source of energy production in eukaryotic cells.
The endoplasmic reticulum is the network of interconnected membranes forming closed vesicles, tubules, and saccules. The endoplasmic reticulum has a number of functions and is primarily involved in the synthesis of proteins and lipids.
Adjacent to the rough endoplasmic reticulum and functionally involved in the sorting and package of secreted protein is the Golgi complex.
Lysosomes are membrane-limited organelles containing acid hydrolytic enzymes that degrade polymers such as proteins, carbohydrates, and nucleic acids.
The Correct
Answer: c
Transcription of a gene begins at an initiation site associated with a specific DNA sequence, termed a promoter region.
After binding to DNA, the RNA polymerase opens up a short region of the double helix to expose the nucleotides. Once the two strands of DNA are separated, the strand containing the promoter acts as a template to which ribonucleoside triphosphates base pair by hydrogen bonds. The initial products of
transcription are known as heterogeneous nuclear RNA because of their large size variation.
These primary transcripts are then processed to form mRNA. RNA splicing accounts for mature RNA being much shorter than nuclear RNA. Moreover, alternative splicing can lead to the production of different mRNA molecules and in some cases different proteins from the same gene. mRNA is exported from the nucleus only after processing is complete.
Answer: c, d
The selectivity of the plasma membrane, although impressive, cannot account for the nonequilibrium composition of living cells. A cell can be maintained in a nonequilibrium state only by continual expenditure of energy. The maintenance of a steady-state, nonequilibrium cellular composition is possible because the plasma membrane is the site of energy converters, membrane proteins that function as biologic transport machines using energy derived from metabolic processes to perform transport work. The archetype for the biologic transport machine is the Na+-K+-ATPase, a membrane protein that hydrolyses cytosolic ATP and couples the resulting free energy to transport of Na+ and K+. A second equally important type of energy-converting transporter is one in which the energy inherent in a transmembrane ion gradient, usually that of Na+ can be used to drive the transport of a second species such as protons, calcium, amino acids, or glucose.
The Correct Answer is
B
Cell junctions are classified as occluding, anchoring, and communicating. The major occluding junction is the
tight junction or zonula occludens which connects cells in epithelia and thereby allows epithelia to serve as selective permeability barriers. Tight junctions are normally located near the apical pool of the cell and form a belt that completely encircles the cell. Anchoring junctions connect the cytoskeleton of the cell to the extracellular matrix or neighboring cells. Morphologically these are adherens junctions or desmosomes. Desmosomes are button-like points of attachment with a prominent intracellular plaque that serves to weld together adjacent cells by serving as anchoring sites for intermediate filaments within the cell. The third functional type of cell junction is a gap junction which is specialized for communication. This junction mediates both electrical and chemical coupling.
Answer: a, b, c
Transport vesicles that bud off the Golgi network carry both material to be secreted from the cell and protein destined to become components of the plasma membrane. These vesicles can fuse with the plasma membrane in a process termed exocytosis. Vesicular transport to the cell surface can be divided into two components, constitutive and regulated secretion. Regulated secretion occurs in cells secreting digestive enzymes, hormones and other regulatory molecules, and neurotransmitters. In regulated secretion, the material to be secreted is sorted in a storage vesicle or granule; fusion with the plasma membrane in exocytosis then takes place in response to external stimulation. Regulated secretion is triggered in most cases by a hormone or neurotransmitter. The ensuing process is termed stimulus-secretion coupling. In most cases the coupling involves an increase in cytoplasmic concentration of Ca++, but may also involve generation of diacylglycerol or production of cyclic AMP which activate kinases or phosphatases.
Answer: b, c
The energetics of water transport across cell membranes is simplified by the fact that water moves only passively due to gradients of hydrostatic pressure or water concentration. Hydrostatic pressure is an important driving force only for certain specialized cells—the capillary endothelium and the glomerulus of the kidney. For most cells of the body, the transmembrane hydrostatic pressure is 0 and water moves only in response to water concentration gradients. Because the concentration of water is determined by the amount of dissolved solute, the difference in water concentration is typically expressed as a function of the difference in solute concentration or osmotic pressure difference. Because there are no specialized, energy-converting transport mechanisms for water, water is distributed at equilibrium. Water distribution is determined entirely by solute to solute distribution.
Answer: BD
DISCUSSION:
Tensile strength measures load per cross-section area at rupture, whereas burst strength measures load required to break a wound, regardless of dimension. Therefore, skin wounds have comparable tensile strength, regardless of thickness. Collagen appears in the wound by 3 to 4 days. Minimal wound strength on day 2 is due to fibrin polymerization and adhesion of globular proteins. Wounds rapidly gain strength for about 4 months and then continue to gain strength at a slower rate for more than a year. Wounds do not regain the strength of normal tissue.
Option B
Radiating pain is a classic symptom of nerve root involvement. Disc displacement is known to cause nerve impingement.
Magee DJ.
Orthopedic Physical Assessment
, 3rd Ed. Philadelphia, PA: WB Saunders; 1997, p 473, 476.
A common symptom of an aortic aneurysm is continuously throbbing pain. This serious condition must be immediately reported to MD.
Goodman C, Snyder T.
Differential Diagnosis in Physical Therapy.
3rd Edition. Pennsylvania: Sauders; 2000, p 450.
Option B
Grade I/II joint mobilizations decrease pain while increasing the quality of synovial fluid. The other options increase joint pressure and pain or may increase inflammation.
Kisner C, Colby L.
Therapeutic Exercise: Foundations and Techniques
. 4th Edition. Pennsylvania: F.A. Davis Company; 2002, p 622-623.
of the puffer fish, tetrodotoxin, acts by blocking the Na+ channels that are responsible for the conduction of nerve impulse. The diuretic, amiloride, acts by blocking the Na+ channels that inhabit the apical membrane of the epithelial cells of the distal nephron. Local anesthetics such xylocaine also act by blocking ion channels. 
