Bio 140 - Chapter 6

Absolute temperature (T)

Temperature measured on the Kelvin scale

Catabolism

The set of chemical reactions that break down molecules into smaller units and. in the process, produce ATP to meet ehe energy needs of the cell

Anabolism

The set of chemical reactions that build molecules from smaller units utilizing an input of energy, usually in the form of ATP. Anabolic reactions result in net energy storage within cells and the organism

Enthalpy (H)

The total amount of energy in a system

Potenital energy

Stored energy that is released by a change in an object's structure or position

Energetic coupling

The process in which a spontaneous reaction (negative DeltaG) drives a non-spontaneous reaction (positive DeltaG).

Activators

A compound that increased the activity of an enzyme

Chemical energy

A form of potential energy held in the chemical bonds between pairs of atoms in a molecule

Cofactor

A substance that associates with an enzyme and plays a key role in its function

Inhibitors

A synthesized compound that decreased the activity of an enzyme

20. In a reaction, enzymes change the: A. Activation energy B. First law of thermodynamics C. Second law of thermodynamics D. Types of products E. DeltaG

A. Activation energy

Allosteric enzymes

An enzyme whose activity is affected by binding a molecule at a site other than active site. Typically , allosteric enzymes change their shape on binding an activator or inhibitor

19. How does protein folding allow for enzyme specificity?

An enzyme will only act on those substrates that bind to its active site (the portion of the enzyme that binds substrate and converts it to product). An enzyme has to fold into its correct shape for the active site to be the right shape to bind its substrate

Phototrophs

An organism that captures energy from sunlight

Chemotrophs

An organism that derives its energy directly from organic molecules such as glucose

Autotrophs

An organism that is able to synthesize its own food using energy from sunlight or inorganic chemicals; a primary producer

Heterotrophs

An organism that obtains its carbon from organic molecules synthesized by other organisms

16. Suppose that, in a given reaction, the enthalpy (H) increases by 10 units, and the disorder (TS) increases by 12 units. By how many units did the Gibbs free energy change? A. 2 B. -2 C. 22 D -22

B. -2

14. As a cat pounces on a mouse, its muscles consume 10 units of potential energy (which the cat previously gained from the food it consumed). However, the pounce itself only required 4 units of kinetic energy. how many units of energy were dissipated as heat? A. 2.5 B. 4 C. 6 D. 10 E. 14

B. 4

15. Which of the statements is true about exergonic reactions? A. Exergonic reactions have a positive DeltaG B. Exergonic reactions consume energy C. Exergonic reactions are found only in biological systems D. Exergonic reactions are catabolic E. Exergonic reactions measure the strength of an ionic bond

C. Exergonic reactions are found only in biological systems

3. Oak trees are categorized as: A. Photoheterotrophs B. Chemoheterotrophs C. Photoautotrophs D. Chemoautotrophs

C. Photoautotrophs

2. What is the difference between catabolism and anabolism?

Catabolism is the set of chemical reactions that break down macromolecules into smaller units, releasing energy (ATP). Anabolism is the set of chemical reactions that build macromolecules from smaller units and require an input of energy (usually in the form of ATP)

5. What is the relationship between strength of covalent bond and the amount of chemical energy it contains?

Chemical energy is a form of potential energy held in chemical bonds (such as covalent bonds) between atoms in a molecule. The stronger the covalent bond, the less chemical energy it contains. The weaker the covalent bond, the more chemical energy it contains. Carbohydrates, lipids, and proteins have many carbon - carbon and carbon - hydrogen bonds. These bonds are relatively weak and are therefore rich sources of chemical energy

21. Imagine that a researcher tries to reduce the size of an enzyme by removing all the amino acids from the protein except those flanking, and constituting, the active site. Why wouldn't this work? A. Without the additional amino acids, the protein may not fold properly B. The removal of the amino acids may affect the ability of the enzyme to bind to substrates C. The removal of the amino acids will likely affect the shape of the active site D. All of these choices are correct

D. All of these choices are correct

Exergonic

Describes reactions with a negative DeltaG that release energy and proceed spontaneously

Endergonic

Describes reactions with a positive DeltaG that are not spontaneous and so require an input of energy

8. Of the molecules, which has the greatest chemical potential energy? A. Water B. Sodium chloride C. Carbon dioxide D. Alanine E. Glucose

E. Glucose

7. Carbon-carbon covalent bonds, such as the ones in carbohydrates and lipids, are _____ and have _____. A. Weak; a lot of kinetic energy B. Strong; a lot of kinetic energy C. Strong; little kinetic energy D. Strong; a lot of potential energy E. Weak; a lot of potential energy

E. Weak; a lot of potential energy

18. Which of the following do enzymes change? DeltaG, reaction rate, types of product, activation energy, the laws of thermodynamics?

Enzymes increase the reaction rate and decrease the activation energy. Enzymes do not change other parameters

17. What are three characteristics of enzymes, and how does each permit chemical reactions to occur in cells?

Enzymes reduce the activation energy of a chemical reaction (or the energy input necessary to reach the transition state) by stabilizing the transition state and decreasing its free energy. See Fig. 6.12. Enzymes are catalysts that participate in a chemical reaction, forming complexes with products and reactants, but are not themselves consumed in the process. Enzymes are also highly specific. They can influence enzyme activity. Inhibitors decrease the activity of enzymes, whereas activators can influence enzyme activity. See Fig. 6.16 for an example of two different types of inhibitors

12. How does increasing the temperature affect the change in free energy (DeltaG) of a chemical reaction?

Increasing the temperature increases the value of TDeltaS, which decreases DeltaG, since DeltaG = DeltaH - TDeltaS. As a result, an increase in temperature makes it more likely that a reaction will proceed without a net input of energy

10. Cold air has less entropy than hot air. The second law of thermodynamics states that entropy always increases. Do air conditioners violate this law?

No, because the second law of thermodynamics applies to the universe as a whole. This means that we have to consider not just the air in the room but the heat released to the outdoors as well. An air conditioner produces more hot air than cold air, and therefore total entropy increases, as described by the second law of thermodynamics

4. What are the two forms of energy? Provide an example of each.

One form of energy is kinetic energy (the energy of motion). Examples of kinetic energy are flexing a muscle and throwing a ball. The other form of energy is potential energy (stored energy). Potential energy depends on the structure of the object or its position relative to its surroundings, and it is released by a change in the object's structure or position. A ball sitting on the top of the stairs has a great deal of potential energy, which is released when the ball starts to roll down the stairs (at which point, the energy is converted into kinetic energy)

1. What are the ways that organisms obtain energy and carbon from the environment? What are the names used to describe these organisms?

Organisms obtain energy from the environment in two ways: (1) by harvesting energy from sunlight (phototrophs), and (2) by harvesting energy from chemical compounds (chemotrophs). These groups are further distinguished by how they obtain carbon. Autotrophs obtain carbon directly from inorganic sources - such as carbon dioxide - and convert it into an organic source of carbon, such as glucose. Heterotrophs obtain carbon from organic compounds made by other organisms. (See Fig. 6.1 for examples)

9. What are the first and second laws of thermodynamics and how do they relate to chemical reactions?

See Figs. 6.5 and 6.6. The first law of thermodynamics is the law of conservation of energy. It states that energy can be neither created nor destroyed; it can only be transformed from one form into another. The second law of thermodynamics states that the transformation of energy is associated with an increase in the disorder of the universe. The degree of disorder is called entropy. Chemical reactions are subject to the laws of thermodynamics (like everything else). As a result, the total amount of energy remains the same before and after a chemical reaction, but some of the energy is used to increase the entropy of the system, and only some of the energy is available to do the work of the cell

Entropy (S)

The amount of disorder (or the number of of possible positions and motions of molecules) in a system

11. For a chemical reaction with a positive value of DeltaG, what are the possible relative values for DeltaH and TDeltaS? Is the reaction spontaneous or not? Answer the same questions for a chemical reaction with a negative value of DeltaG.

The amount of energy available to do work is called Gibbs free energy (G). In a chemical reaction, you compare the free energy of the reactants and products to tetermine whether there is energy available to do work. This difference is called DeltaG. DeltaG = DeltaH - TDeltaS. If the enthalpy difference (DeltaH) is positive and the entropy difference (DeltaS) is negative, then DeltaG is positive. This kind of reaction is endergonic and non-spontaneous. By contrast, if the enthalpy difference (DeltaH) is negative and the entropy difference (DeltaS) is positive, then DeltaG is negative. This kind of reaction is exergonic and occurs spontaneously

Metabolism

The chemical reactions occurring within cells that convert one molecule into another and transfer energy in living organisms

Second law of thermodynamics

The principle that the transformation of energy is associated with an increase in the degree of disorder in the universe

Negative feedback

The effect in which the final product of a biochemical pathway inhibits the first step; the process in which a stimulus acts on a sensor that communicates with an effector producing a response that opposes the initial stimulus Negative feedback is used to maintain steady conditions, or homeostasis

Activation energy (Ea)

The energy input necessary to reach the transition state

Kinetic energy

The energy of motion

13. How can the hydrolysis of ATP drive non-spontaneous reactions in a cell?

The hydrolysis of ATP releases energy. This energy can be used to drive non-spontaneous reactions in a cell if the total DeltaG for the entire pathway is negative. See Fig. 6.10

First law of thermodynamics

The law of conservation of energy: energy can neither be created no destroyed - it can only be transformed from one form into another

Adenosine triphosphate (ATP)

The molecule that provides energy in a form that all cells can readily use to perform the work of the cell

Active site

The portion of an enzyme that binds substrate and converts it to product