CELL BIOLOGY Below are mutliple choice questions Dont mind t

CELL BIOLOGY. Below are mutliple choice questions. Don\'t mind the circled answers. Please provide me with the correct answers and maybe a little explanation as to why you chose that one Thank you SOOO MUCH!!

03. The glucose concentration is higher in the cytosol of an intestinal epithelial cell (IEC) than it is in the intestinal lumen and in the basal extracellular fluid. Thus, to prevent glucose from leaving the IEC and going into the intestine lumen and to allow glucose to enter into the blood a. IEC symporters are found only in the plasma membrane (PM) facing the intestine lumen. b. IEC Na+/glucose symporters are found only in the plasma membrane (PM) facing the basal extracellular fluid c, IEC glucose uniporters are found only in the PM facing the basal extracellular fluid. d. IEC glucose uniporters are found only in the PM facing the intestine lumen. e Both a and c are correct answers.

Solution

3). The sodium glucose symporters are located in the plasma membrane of the intestinal epithelial cell facing the intestinal lumen. Na⁺-glucose symporters take up glucose from the intestine in a process which is driven by the downhill flow of Na⁺ .Glucose is thus cotransported with Na⁺ across the apical plasma membrane into the epithelial cell. Glucose uniporters such as GLUT2 is a passive glucose uniporter located in the basal surface and facing the extracellular fluid. The role of this uniporter is to transport glucose from the cell into the blood.

Therefore, the correct option for this question is option (e) i.e. both a and c are correct answers.

4). When the neuron is in a resting state, neurotransmitters are stored in vesicles at the pre-synaptic terminal. Neurotransmitters are slowly released from these vesicles in quantal units. Ca²⁺ plays a very essential role in the release of neurotransmitters. When the Ca²⁺ channels are blocked the release of neurotransmitters are also inhibitied. Therefore, injection of Ca²⁺ into a nerve terminal would result in release of neurotransmitters.

Injection of calcium ions into nerve terminal would cause the neurotransmitter-containing vesicles to dock and fuse to the presynaptic neuron\'s cell membrane. Further, fusion of the vesicular membrane with the presynaptic cell membrane results in the emptying of the vesicle\'s contents (acetylcholine) into the synaptic cleft. Acetylcholine then diffuses into the synaptic cleft and binds to the nicotinic acetylcholine receptors on the motor endplate.

6). The sodium potassium pump uses ATP energy to transport 3 ions of Na⁺ from the cytosol to the extracellular space, while it simultaneously pumps 2 K⁺ ions from the extracellular space to the cytosol. Thus the correct choice is option (e).

7). Change in voltage below the threshold causes the voltage gated sodium channels to open. As a result of this sodium ions diffuse freely into the cell down both their concentration and electric gradients. The corresponding movement of positive charge into the cell causes the membrane to reverse potential briefly becoming positive at about +40mV, which approaches the equilibrium potential for Na⁺. After approximately 1 sec, the sodium channels spontaneously inactivate, blocking further influx. The change in membrane potential caused by the opening of sodium channels then triggers the opening of voltage gated potassium channels, to cause the membrane potential to swing back to a negative value. Thus, the correct answr is option (b).

8).Glucose crosses apical surface of epithelial cells primarily by Na⁺/Glucose co-transport. While K⁺ transport depends on active transport by the sodium potassium pump. Thus they have separate transporter proteins, making the correct answer choice, option (a).

21). It is assumed that the hydrophobis regions corresond to membrane spanning domains. In the above plot, there are 2 such hydrophobic peaks so the answer should be optiob (b).

22).The sodium ptoassium pump helps to maintain the concentration gradient of Na⁺ across the membrane by keeping the intracellular concentration of Na⁺ low. The resting membrane potential of a cell is maintained by the sodium-potassium pump. Not only does the sodium-potassium pump maintain correct concentrations of Na^++start superscript, plus, end superscript and K^++start superscript, plus, end superscript in living cells, but it also plays a major role in generating the voltage across the cell membrane in animal cells. While voltage gated channels are responsible for action potentials. Therefore, the correct choice for this question is option (d).

23). Copy number variations (CNV) refer to the variations in large segments of DNA leading to dosage imbalances. CNVs are a type of structural variant involving alterations in the number of copies of specific regions of DNA, which can either be deleted or duplicated. Therefore the correct answer choice is option (b).