1. Compare and contrast ATP, NADPH, NADH, FADH2 and Acetyl CoA, four important e
ID: 144605 • Letter: 1
Question
1. Compare and contrast ATP, NADPH, NADH, FADH2 and Acetyl CoA, four important energy carriers in the cell. Included in your discussion should be their structure, type of energy carried, and mechanism for energy transfer.
2. Recently, one of my introductory biology students told me that plants use photosynthesis to create ATP for use in cellular processes in the cell and did not use respiration. Discuss whether or not this is correct and justify your answer.
3. Insulin functions in the extracellular space by binding to receptors in the cellular membrane. Using what you know about disulfide bridges and conditions within the cell and in the extracellular space, discuss why insulin would not be able to work within the cell, even if a receptor was available.
Explanation / Answer
1. ATP (adenosine triphosphate) - It consists of adenosine which is composed of an adinine ring and a ribose sugar, three phosphate groups. It is known as energy currency of the cell that is it is capable to store and transport chemical energy within cells. Energy is released by the hydrolysis of the third phosphate group.
NADPH - It is the reduced form of NADP+, Nicotinamide adenine dinucleotide phosphate. The oxidative chemical reactions of respiration release energy, some of which is heat and some of it is captured in the form of high energy compounds such as ATP & NADPH. It is an electron carrier used in photosynthesis.
NADH - It is known as Nicotinamide adenine dinucleotide(two nucleotides joined through their phosphate groups), this is used as a reducing agent to donate electrons to the electron carriers of the electron transport chain which results in the production of ATP under aerobic condition. one NADH worth 3 ATP.
FADH2 - It stands for Flavin adenine dinucleotide. It is a powerful reducing agent to pass or donate electrons to the electron transport chain. This is produced during the krebs cycle. One FADH2 worth 2 ATP.
Acetyl CoA - It is produced during the aerobic respiration after glycolysis. It carries the carbon atoms of the acetyl group and this is oxidised for energy production in TCA Cycle. It participates in Lipid Carbohydrate and protein metabolism.
2. Photosynthesis - It is a process by which green plants use energy from the sunlight to convert carbon dioxide & water into simple sugar glucose.
when coming to Cellular respiration - It is a process in which glucose is broken down into the energy- carrying molecule, ATP by using Oxygen.
Through these definitions it was clear that photosynthesis requires energy to produce food and the cellular respiration breaks the food and releases energy. In simple form, photosynthesis makes the glucose that is used in cellular respiration to produce ATP. Hence the statement is wrong.
3. The insulin receptor in composed of two alpha subunits and two beta subunits linked by disulfide bridge bonds which is embeded in the plasma membrane.The alpha chains are entirely extracellular & help in binding and the beta chains can penetrate through the plasma membrane. Binding of alpha subunits causes the beta subunits to autophosphorylate, thus activating the catalytic activity of the receptor. This activated receptor then phosphorylates a number of intracellular proteins and this leads to the alteration in their activity and this results in generating a biological response which activates the cell glucose transporter molecules to give entrance in the cell membrane. In short, Insulin binds to the receptors on the cell surface because so that the glucose can enter the cell.
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