Physiology Week 4 Quiz

The ECF osmolarity is mainly determined by Na+ because it is the most abundant cation in the extracellular fluid. Sodium ions play a crucial role in maintaining fluid balance and regulating osmotic pressure. Changes in the concentration of Na+ can lead to alterations in water distribution and affect cell function. The other ions mentioned, Ca++, Mg++, and K+, also contribute to osmolarity but to a lesser extent compared to Na+. Plasma proteins, while important for maintaining osmotic pressure, have a minimal impact on ECF osmolarity compared to electrolytes like Na+.

The correct answer is "Higher, lower, higher, lower." This is because the extracellular fluid has a higher concentration of sodium ions compared to the intracellular fluid. On the other hand, the extracellular fluid has a lower concentration of potassium ions compared to the intracellular fluid. Additionally, the extracellular fluid has a higher concentration of chloride ions compared to the intracellular fluid. Lastly, the extracellular fluid has a lower concentration of phosphate ions compared to the intracellular fluid.

An isosmotic solution refers to a solution that has the same concentration of solutes as the body fluids. This means that the osmolarity of the solution is equal to that of the body fluids. In other words, the solution and the body fluids have an equal number of solute particles per unit volume. Therefore, the statement that an isosmotic solution has the same osmolarity as body fluids is true.

The movement of O2 through the cell membrane is an example of simple diffusion. Simple diffusion is the passive movement of molecules or ions from an area of higher concentration to an area of lower concentration, without the need for energy or a transport protein. In this case, O2 molecules move freely across the cell membrane from an area of higher concentration (outside the cell) to an area of lower concentration (inside the cell) until equilibrium is reached.

Simple diffusion and facilitated diffusion both do not require adenosine triphosphate (ATP) because they are passive processes that rely on the concentration gradient to drive the movement of molecules across the cell membrane. Unlike active transport, which requires ATP, simple diffusion and facilitated diffusion allow molecules to move down their concentration gradient without the need for energy input.

Simple diffusion of a substance refers to the movement of molecules or ions from an area of higher concentration to an area of lower concentration, without the involvement of any carrier proteins. This process does not require any metabolic energy and can occur against an electrochemical gradient. Additionally, simple diffusion does not exhibit saturation properties or competition with other molecules for transport. Therefore, the correct answer is that simple diffusion is not carrier mediated.

Both simple and facilitated diffusion occur down an electrochemical gradient. This means that molecules move from an area of high concentration to an area of low concentration, driven by both electrical and chemical forces. In simple diffusion, molecules pass directly through the lipid bilayer of the cell membrane, while in facilitated diffusion, molecules move across the membrane through specific protein channels or carriers. The electrochemical gradient is the driving force for both types of diffusion, allowing molecules to move across the membrane without the need for energy expenditure.

Facilitated diffusion is a type of passive transport where molecules move across the cell membrane with the help of carrier proteins. Unlike active transport, facilitated diffusion does not require the use of metabolic energy such as ATP. Instead, it relies on the concentration gradient of the molecules to drive their movement. Therefore, the statement that facilitated diffusion requires the use of metabolic energy is false.

Active transport is a process that requires the use of energy to move substances against their concentration or electrochemical gradient. It is a carrier-mediated transport, meaning that specific proteins called carriers are involved in the movement of substances across the cell membrane. Active transport also exhibits saturation properties, meaning that there is a maximum rate at which substances can be transported. However, it is incorrect to say that active transport does not require metabolic energy, as energy from ATP is needed to drive the process.

Capillary pressure refers to the pressure difference between the inside and outside of a capillary. Interstitial fluid pressure, on the other hand, is the pressure exerted by the fluid in the spaces between cells. The statement suggests that capillary pressure and interstitial fluid pressure work in opposite directions. This means that when capillary pressure increases, interstitial fluid pressure decreases, and vice versa. Therefore, the given answer, "True," accurately reflects the relationship between capillary pressure and interstitial fluid pressure.

The statement is false because the human body does not have 70% water out of total body mass. The actual percentage of water in the human body varies depending on factors such as age, sex, and body composition. On average, adult males have about 60% water content, while adult females have about 55% water content. Therefore, the statement is incorrect.

In primary active transport, transport is driven by the energy stored in ATP molecules, not by the concentration gradient of another molecule. ATP is hydrolyzed to ADP and inorganic phosphate, releasing energy that is used to power the transport of molecules against their concentration gradient. Therefore, the correct answer is False.

Simple diffusion is a passive process that occurs down a concentration gradient until a state of equilibrium is reached. This means that molecules or ions move from an area of higher concentration to an area of lower concentration until there is an equal concentration on both sides of the membrane. It does not require any carrier proteins or the activity of the Na+/K+ pump. Additionally, it does not directly require metabolic energy, as it is driven solely by the concentration gradient.

Simple diffusion through protein channels is not rate limited by an intrinsic Vmax. In simple diffusion, molecules move across a concentration gradient without the need for energy or carrier proteins. The rate of diffusion is determined solely by the concentration gradient and the permeability of the channel. There is no maximum rate of transport (Vmax) for simple diffusion because it is a passive process that does not rely on any specific transport proteins or energy sources.

Osmosis is the movement of water from a region of high concentration to a region of low concentration, not the other way around. This process occurs across a semipermeable membrane, where water molecules move to equalize the concentration of solute on both sides of the membrane. Therefore, the given statement is incorrect.

Counter-transport refers to the movement of two different molecules in opposite directions across a membrane. In this case, Na+-dependent transport of Ca++ from the cytosol to the extracellular fluid involves the movement of Na+ ions into the cell and Ca++ ions out of the cell. This is an example of counter-transport because the two ions are being transported in opposite directions.

Co-transport is the process in which two different substances are transported across a membrane together, using the energy from the movement of one substance to drive the movement of the other. In the case of glucose transport from the intestinal lumen into an intestinal epithelial cell, glucose is transported along with sodium ions through a sodium-glucose co-transporter protein. This co-transporter uses the energy from the movement of sodium ions down their concentration gradient to transport glucose against its concentration gradient into the cell. Therefore, the correct answer is co-transport.

A hyperosmotic solution refers to a solution that has a higher osmotic pressure compared to another solution. In this case, a hyperosmotic solution for 1 ml of NaCl would be 1 ml of CaCl2. This means that the CaCl2 solution has a higher osmotic pressure than the NaCl solution when both are at the same volume.

The statement is false because the fluid lost in diarrhea is actually hypotonic. Diarrhea leads to the loss of water and electrolytes from the body, resulting in a more concentrated solution in the intestines. This causes water to be drawn from the body into the intestines, leading to dehydration. Therefore, the fluid lost in diarrhea is not hypotonic, but rather hypertonic due to the increased concentration of solutes.

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The term "glycocalyx" refers to the negatively charged carbohydrate layer on the outer cell surface. This layer is composed of glycolipids and integral glycoproteins that protrude into the cytosol. It plays a crucial role in cell recognition, cell adhesion, and protection against mechanical and chemical damage. The glycocalyx also helps in maintaining the cell's shape and acts as a barrier, preventing the entry of harmful substances into the cell.

The incorrect statement is "In most diseases, homeostatic mechanisms are no longer operating in the body". This statement is incorrect because in most diseases, homeostatic mechanisms are actually still operating in the body, but they may be disrupted or dysfunctional. Homeostasis is the body's natural ability to maintain stable internal conditions, and even in the presence of disease, the body tries to restore balance and stability.

When red blood cells are placed in a solution of 140-millimolar NaCl containing 20-millimolar urea, the cells will initially shrink due to the higher osmolarity of the solution compared to the cytoplasm. However, urea is permeable to the cell membrane, allowing it to enter the cell and equilibrate with the cytoplasm. As a result, the osmolarity inside and outside the cell becomes equal, causing the cell to return to its original volume. Therefore, the correct answer is "Shrink, then return to original volume."

Overuse of diuretics can lead to hyponatremia. Diuretics are medications that increase urine production and help remove excess fluid from the body. However, when diuretics are used excessively, they can cause an imbalance in the body's electrolytes, including sodium. Sodium is an essential electrolyte that helps regulate fluid balance in the body. When sodium levels are too low, it can result in hyponatremia, which can cause symptoms such as nausea, headache, confusion, and in severe cases, seizures or coma. Therefore, overuse of diuretics can disrupt the body's electrolyte balance and lead to hyponatremia.