Metabolism WS - jbub n - Ap Biology PDF

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Name: Mehul Goel

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Mag Bio: AN INTRODUCTION TO METABOLISM & FEEDBACK CONTROL An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics. Using the e-textbook (OpenStax), along with the PPT, answer these questions. *Also refer to the Unit 1 PPT (The ‘Working Cell’- Part 2 PPT from the last unit, if needed) 1. Define metabolism. Metabolism is the chemical reactions in the body's cells that change food into energy. Our bodies need thi energy to do everything from moving to thinking to growing. Specific proteins in the body control the chemical reactions of metabolism. 2.

There are two types of reactions in metabolic pathways: anabolic and catabolic. a. Which reactions release energy? Catabolic b. Which reactions consume energy? Anabolic c. Which reactions build up larger molecules? Anabolic d. Which reactions break down molecules? Catabolic e. Which reactions are considered “uphill”? Anabolic f. What type of reaction is photosynthesis? Anabolic g. What type of reaction is cellular respiration? Catabolic h. Which reactions require enzymes to catalyze reactions? Anabolic and Catabolic

3. Contrast kinetic energy with potential energy. Kinetic energy is the energy that can be associated with the relative motion of an object. Potential energy is energy that is not kinetic or moving.

The free-energy change of a reaction tells us whether the reaction occurs spontaneously 5. What is free energy? Include the equation and the meaning of the symbols. The portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system. This is known as free energy. ∆G =∆H – T∆S ∆G = change in Gibbs Free Energy ∆H = change in enthalpy T = temperature in Kelvin ∆S = change in entropy

6. For an exergonic reaction, is ∆G negative or positive? ∆G is negative because an exergonic reaction needs less energy. 7.

Is cellular respiration an endergonic or an exergonic reaction? What is ∆G for this? reaction? Cellular respiration is an exergonic reaction, and ∆G in this reaction is -686 kilocalories per mole. 8. Is photosynthesis endergonic or exergonic? What is the energy source that drives it? Photosynthesis is an endergonic reaction, and the energy source that drives it is light energy or more precisely the sun. 9. To summarize, if energy is released, ∆G must be what? If energy is released then ∆G must be negative.

ATP powers cellular work by coupling exergonic reactions to endergonic reactions

10.

Here is a molecule of ATP. Label it. Use an arrow to show which bond is likely to break. *2021- You may use a highlighter and/or description. The phosphate group is the most likely to break and it will break using a process called hydrolysis.

a. By what process will the bond between 2nd and 3rd PO4 break? (Hint: Hydrolysis or Dehydration Synthesis) The bond between the 2nd and 3rd PO4 will break using a process called Hydrolysis. b. Explain the name ATP by listing all the molecular components. ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups bonded to it, forming adenosine triphosphate 11.

When the terminal phosphate bond is broken, a molecule of inorganic phosphate P i is released & then bonds to a different molecule. Therefore, energy is released. For this reaction: ATP  ADP + Pi

∆G = –7.3 kcal/mol

Is this reaction endergonic or exergonic? This reaction is exergonic. 12. Why is the terminal phosphate bond broken, rather than a bond within the organic part of the structure? (*look at the molecular structure of the molecule and think about electronegativity) ATP is made unstable by the three adjacent negative charges in its phosphate tail, which want to get further away from each other. Thus, the terminal phosphate bond is broken, rather than a bond within the organic part of the structure. 13. What is energy coupling? * You need to make sure you understand this concept! In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction is called energy coupling. In many cellular reactions, a phosphate group is transferred from ATP to some other molecule. It is said to be phosphorylated. It does this in order to make the second molecule less stable. (*more or less)

14.

Search online for this amazing bit of trivia: If you could not regenerate ATP by phosphorylating ADP, how much ATP would you need to consume each day?

If ATP could not be regenerated by the phosphorylation of ADP, humans would use up nearly their body weight in ATP each day.

Enzymes speed up metabolic reactions by lowering energy barriers 15.

What is a catalyst?

A catalyst is a chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

16. What is activation energy (EA)? Activation energy is required to twist the reactant molecules so the bonds can break. Also, it is the amoun of energy that reactants must absorb before a chemical reaction will start. Sometimes it is also called fre energy of activation. 17. On the graph, label the x-axis “Progress of the Reaction” and the y-axis “Free Energy.” Label EA on this sketch, both with and without enzyme.

EA without enzyme EA with enzyme Reactants ∆G Free Energy

Products Progress of the Reaction  a. What effect does an enzyme have on EA? The enzyme catalyzes the reaction and lowers the activation energy (EA). b. Label ∆G. Is it positive or negative? Delta G is negative in this case. c. How is ∆G affected by the enzyme? It is unable to make an endergonic reaction into an exergonic one.

18.

Label this figure while you define each of the following terms: enzyme

substrate

active site

products

Enzyme: A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins. Substrate: The reactant on which an enzyme works. Active Sites: The specific region of an enzyme that binds the substrate and that forms the pocket in whic catalysis occurs. Products: A material resulting from a chemical reaction. 19. What is meant by ‘induced fit’? How is it shown in this figure? When the substrate enters the active site, it forms weak bonds with the enzyme, inducing a change in the shape of the protein. This change allows additional weak bonds to form, causing the active site to enfold th substrate and hold it in place. 20.

Enzymes lower activation energy. Describe at least one mechanism of how they lower it.

The enzyme-substrate complex can lower activation energy by bending substrate molecules in a way that facilitates bond-breaking, helping to reach the ideal transition state. 21. Many factors can affect the rate of enzyme action, one being temperature. Explain how temp would affect rate if temp was lowered and if temp was raised. Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. Sometimes, extreme high temperatures can cause an enzyme to denature and stop working. 22.

Recall that enzymes are globular proteins. Why can extremes of pH or very high temperatures affect enzyme activity? (Hint- think about the type of bonds affected) Each enzyme has an ideal pH range. If one changes the pH outside of this range it will slow enzyme activity 23. There is a human enzyme that functions well with a pH 2. Where do you think it is found? I think it is found in the human stomach considering that gastric fluids generally are very acidic. 24. Distinguish between cofactors and coenzymes. Give an example of each. Coenzymes are small, non-protein organic molecules that carry chemical groups between enzymes A Cofactor is a non-protein chemical compound that tightly and loosely binds with an enzyme or other protein molecules. Cofactors - iron, magnesium, manganese, cobalt, copper, zinc, and molybdenum and Coenzyme - B vitamins and S-adenosyl methionine and also coenzyme A. 25.

There can be both competitive inhibitors and noncompetitive inhibitors with enzymes.

Explain which types of competitors are shown in the below diagram and how you know.

Competitive inhibitors are substances that reduce the activity of an enzyme by entering the active site in place of the substrate, on the other side noncompetitive inhibitors are substances that reduce the activity of an enzyme by binding to a location remote from the active site, changing the enzyme’s shape so that the active site can no longer catalyze the conversion from substrate to product. 26.

What is the allosteric site of an enzyme?

The allosteric site of an enzyme is where a molecule that is not a substrate binds, thus changing the shape of the enzyme and influencing its ability to be active. 26. Study this figure. Although it looks a bit intimidating, relate this to the mechanisms of feedback control (similarly to the thermostat example we discussed in class). Just follow the arrows and give these questions a try. No penalty for trying and missing a question! Nothing ventured, nothing gained!

a. What is the substrate molecule to initiate this metabolic pathway? Threonine b. What is the inhibitor molecule? Isoleucine c. What type of feedback is it? Positive feedback d. When does it have the most significant regulatory effect? When it starts to bind to an allosteric site e. How does this affect the formation of the end-product? It helps fasten the rate at which the end-product will be made.

In negative feedback systems, the response reverses a change in a controlled condition. In positive feedback systems, the response strengthens the change in a controlled condition. State whether each of the following indicates negative or positive feedback: 1. Negative If blood temperature rises too high, specialized neurons in the hypothalamus of the brain sense the change. These neurons signal other nerve centers, which in turn send signals to the blood vessels of the skin. As these blood vessels dilate, more blood flows close to the body surface and excess heat radiates from the body. 2. Negative If the blood temperature falls too low, specialized neurons in the hypothalamus of the brain sense the change and signals are sent to the cutaneous arteries (those supplying the skin) to constrict them. Warm blood is then retained deeper in the body and less heat is lost from the surface. 3. Positive During childbirth stretching of the uterus triggers the secretion of the hormone oxytocin, which stimulates uterine contractions and speeds up labor. 4. Negative The body regulates blood pressure in a process in which nerves sense the blood flow resistance associated with higher blood pressure; the nerves relay this message to the brain; the brain then slows down the heart rate and dilates the blood vessels, lowering the blood pressure....