To further investigate the cellular response in photoreceptor cells, we will now look at the actual effect of cGMP within the phototransduction pathway. Again, we will compare what happens in the dark and in the presence of light to understand how an electric signal is generated in either condition. Comparing both conditions (in the dark or under the light), researchers have measured the molar concentration of cytosolic cGMP and recorded the membrane potential of rod cells by placing micro-electrodes on either side of their plasma membrane (see figure below). A negative membrane potential means that there are more negatively charged ions inside the cell compared to outside the cell, or equivalently, that there are less positively charged ions inside the cell compared to outside the cell. A positive membrane potential means that there are more negatively charged ions outside the cell compared to inside the cell, or equivalently, that there are less positively charged ions outside the cell compared to inside the cell. The readings are presented below: In the dark Inside of the cell [CGMP] = 14 mM -10mV Outside of the cell In the presence of light Inside of the cell [CGMP] = 4 μM -70mV Outside of the cell 11. Based on the cytosolic concentration of cGMP and the membrane potential readings in both conditions, what can you conclude about the role of cGMP during phototransduction? A. CGMP helps maintain a constant membrane potential B. Light increases the concentration of cytosolic cyclic-GMP (CGMP) C. Light decreases the concentration of cytosolic GMP D. CGMP increases the membrane potential (= depolarization from -70mV up to -10mV) E. CGMP decreases the membrane potential (= hyperpolarization from -10mV down to -70mV).
To further investigate the cellular response in photoreceptor cells, we will now look at the actual effect of cGMP within the phototransduction pathway. Again, we will compare what happens in the dark and in the presence of light to understand how an electric signal is generated in either condition. Comparing both conditions (in the dark or under the light), researchers have measured the molar concentration of cytosolic cGMP and recorded the membrane potential of rod cells by placing micro-electrodes on either side of their plasma membrane (see figure below). A negative membrane potential means that there are more negatively charged ions inside the cell compared to outside the cell, or equivalently, that there are less positively charged ions inside the cell compared to outside the cell. A positive membrane potential means that there are more negatively charged ions outside the cell compared to inside the cell, or equivalently, that there are less positively charged ions outside the cell compared to inside the cell. The readings are presented below: In the dark Inside of the cell [CGMP] = 14 mM -10mV Outside of the cell In the presence of light Inside of the cell [CGMP] = 4 μM -70mV Outside of the cell 11. Based on the cytosolic concentration of cGMP and the membrane potential readings in both conditions, what can you conclude about the role of cGMP during phototransduction? A. CGMP helps maintain a constant membrane potential B. Light increases the concentration of cytosolic cyclic-GMP (CGMP) C. Light decreases the concentration of cytosolic GMP D. CGMP increases the membrane potential (= depolarization from -70mV up to -10mV) E. CGMP decreases the membrane potential (= hyperpolarization from -10mV down to -70mV).
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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