1. You are comparing how fructose is transported into two different types of bac
ID: 277938 • Letter: 1
Question
1. You are comparing how fructose is transported into two different types of bacterial cells. You expose both cell types to a single concentration of fructose then measure the rate of transport based on accumulation in the cells. Cell type #1 accumulates fructose rapidly until the concentration inside the cell is essentially equal to that outside the cell. Cell type #2 accumulates fructose at an equal rate but continues to accumulate fructose to a concentration 10-fold greater than that outside the cell. Further examination reveals that the pH of the cytosol has decreased during the experiment for Cell type #2 but not for Cell type #1. What is the most likely transport mechanism and type of transporter for each cell type? Be specific.
2. Botox is a neurotoxin produced by the bacterium Clostridium botulinum that inhibits the ability of neurons to convert their action potential into a chemical signal at the axon nerve terminal. In order to understand how Botox works, your friend first asks you to explain how a neuron normally converts its electrical signal into a chemical signal at the nerve terminal. Please explain and be sure to describe which molecules are involved and how.
3. The citric acid cycle (or TCA cycle) generates NADH and FADH2, which are then used in the process of oxidative phosphorylation to make ATP. If the citric acid cycle and oxidative phosphorylation are separate processes, then why is it that the citric acid cycle stops almost immediately upon removal of O2?
Explanation / Answer
Ans. 1.
The transport mechanism in cell type1 is passive transport i.e., energy is not required for the transport of fructose inside the cell. the cell must be having some kind of channels in their membranes through which fructose enters the cells until there is equal concentration inside and outside the cell.
the transport system in cell type 2 is active transport i.e., it requires ATP. that's why cell type 2 continues to accumulate fructose to a concentration 10-fold greater than that outside the cell. as the pH of the cytosol is decreased during the experiment for Cell type 2 it suggests that the protons move from outside of the cell to inside and drive the synthesis of ATP which is used to accumulate fructose inside the cell.
Ans. 2.
When the electrical signal reaches the nerve terminal it triggers the fusion of synaptic vesicles to the plasma membrane. these synaptic vesicles carry the neurotransmitters which are released into the synaptic cleft upon fusion. the neurotransmitters bind to the receptor on the membrane of post synaptic neuron and initiate another action potential in the post synaptic neuron.
Ans. 3.
upon removal of O2 citric acid cycle stops because O2 is the final electron acceptor in the oxidative phosphorylation. if O2 is removed NADH and FADH2 are not oxidized to NAD and FAD. NAD and FAD are used in citric acid cycle as they are reduced by accepting electrons. hence in the absence of O2 citric cycle stops immediately.
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