Define Activation Energy

BSC1005

Study Guide for Test 2

Chapter 2

Enzymes- section 2.13

1. Define the following terms: enzyme, substrate, active site, activation energy, competitive

inhibitor, noncompetitive inhibitor, active site

  • Enzyme: a protein that serves as a biological Catalyst, changing the rate of a chemical reaction without itself being in the process.

  • Substrate: A specific substrate (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate of the reaction it catalyzes. A surface in or which an organism lives.

  • Active site: the part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically a pocket groove on an enzyme surface

  • Activation energy: Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is the energy barrier that must be overcome for reactant molecules to transform into product molecules. Activation energy determines the rate at which a reaction proceeds. Reactions with higher activation energy tend to occur more slowly, while reactions with lower activation energy occur more quickly.

  • Competitive inhibitor: A competitive inhibitor is a type of enzyme inhibitor that competes with the substrate for binding to the active site of an enzyme. It binds reversibly to the active site, preventing the substrate from binding and reducing the enzyme's activity. The presence of a competitive inhibitor increases the concentration of substrate required to achieve maximum enzyme activity.

  • Noncompetitive inhibitor: A noncompetitive inhibitor is a type of enzyme inhibitor that binds to an enzyme at a site other than the active site, causing a change in the enzyme's shape and reducing its activity. Unlike competitive inhibitors, noncompetitive inhibitors do not compete with the substrate for binding to the active site. Instead, they bind to a different site on the enzyme, known as the allosteric site. This binding alters the enzyme's conformation, making it less effective in catalyzing the reaction. As a result, the substrate cannot bind properly to the active site, leading to a decrease in enzyme activity.

2. What suffix is typically given to enzymes?

  • The suffix typically given to enzymes is "-ase".

Chapter 4

1. Define the following terms: energy, kinetic energy, potential energy, chemical energy,

heat

    • Energy: Energy is the capacity to do work or cause change. It exists in various forms such as kinetic, potential, thermal, chemical, and electrical energy.

    • Kinetic Energy: Kinetic energy is the energy possessed by an object due to its motion. It depends on the mass and velocity of the object.

    • Potential Energy: Potential energy is the energy possessed by an object due to its position or state. It can be gravitational potential energy, elastic potential energy, or chemical potential energy.

    • Chemical Energy: Chemical energy is a form of potential energy stored in the bonds of chemical compounds. It is released or absorbed during chemical reactions.

    • Heat: Heat is a form of energy that is transferred between objects or systems due to a temperature difference. It flows from hotter objects to colder objects until thermal equilibrium is reached.

2. Be able to give examples of kinetic energy and potential energy

Examples of kinetic energy include:

  1. A moving car: The car possesses kinetic energy due to its motion.

  2. A running athlete: The athlete's body is in motion, so they have kinetic energy.

  3. Wind: Moving air molecules have kinetic energy.

  4. Water flowing in a river: The flowing water possesses kinetic energy.

  5. A swinging pendulum: The pendulum's motion represents kinetic energy.

  6. light

  7. heat

Examples of potential energy include:

  1. A stretched rubber band: The potential energy is stored in the stretched rubber band.

  2. A raised object: An object lifted above the ground has potential energy due to its position.

  3. A compressed spring: The potential energy is stored in the compressed spring.

  4. Water at the top of a waterfall: The water has potential energy due to its height.

  5. A charged battery: The potential energy is stored in the chemical reactions within the battery.

  6. gasoline

3. What is chemical energy? Give examples.

  • Chemical energy is a form of potential energy stored in the bonds of chemical compounds. When chemical reactions occur, this energy can be released or absorbed.

  • Examples of chemical energy include the energy stored in food, such as carbohydrates and fats, which is converted into energy by our bodies during metabolism. Another example is the energy stored in fossil fuels like coal, oil, and natural gas, which can be released through combustion to generate heat and electricity.

4. Define exergonic and endergonic reactions. Give examples of each.

  • Exergonic reactions release energy, while endergonic reactions require energy input.

  • Examples of exergonic reactions include cellular respiration and the combustion of fuel.

  • Examples of endergonic reactions include photosynthesis and the synthesis of proteins.

5. Describe the first and second laws of thermodynamics.

  • The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed in an isolated system, only transferred or transformed. It is often expressed as the equation ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.

  • The second law of thermodynamics states that the entropy of an isolated system tends to increase over time. It implies that natural processes are irreversible and that heat flows from hot to cold objects. It is often expressed in terms of the concept of entropy, which is a measure of the disorder or randomness in a system.

6. Give examples of the first and second laws of thermodynamics.

  • The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another. An example is the conversion of chemical energy in food to mechanical energy in our muscles.

  • The second law of thermodynamics states that the entropy of an isolated system tends to increase over time. An example is the dissipation of heat from a hot object to its surroundings, resulting in a decrease in the usable energy within the system.

7. What is ATP?

  • ATP stands for adenosine triphosphate. It is a molecule that serves as the primary energy currency in cells. ATP stores and releases energy for cellular processes through the hydrolysis of its high-energy phosphate bonds.

8. What is ADP?

  • ADP stands for Adenosine Diphosphate. It is a molecule that plays a crucial role in cellular energy metabolism. ADP is converted into ATP (Adenosine Triphosphate) through the addition of a phosphate group, releasing energy that can be used by cells for various biological processes.

9. What is the structure of ATP?

  • The structure of ATP (adenosine triphosphate) consists of three main components: a nitrogenous base called adenine, a sugar molecule called ribose, and three phosphate groups. The phosphate groups are attached to the ribose sugar in a chain-like structure.

Chapter 4: Photosynthesis

1. Give examples of organisms (at least 2), OTHER THAN PLANTS that are capable of

photosynthesis.

Sure! Here are two examples of organisms, other than plants, that are capable of photosynthesis:

  1. Algae: Algae are a diverse group of photosynthetic organisms that can be found in various aquatic environments. They can range from microscopic single-celled organisms to large seaweeds.

  2. Cyanobacteria: Cyanobacteria, also known as blue-green algae, are a type of bacteria that can perform photosynthesis. They are commonly found in freshwater and marine environments and can form colonies or mats.

2. What are the inputs (or reactants) of photosynthesis?

  • The inputs (or reactants) of photosynthesis are carbon dioxide (CO2) and water (H2O).

3. What are the outputs (or products) of photosynthesis?

  • The outputs (or products) of photosynthesis are oxygen and glucose.

4. Why is photosynthesis so important to life on Earth? List TWO reasons.

Photosynthesis is crucial for life on Earth due to the following reasons:

  1. Oxygen Production: Photosynthesis is responsible for the production of oxygen, which is essential for the survival of most organisms on Earth. Through the process of photosynthesis, plants and some microorganisms convert carbon dioxide and water into glucose and oxygen. The released oxygen is then released into the atmosphere, replenishing the oxygen levels necessary for aerobic respiration.

  2. Food Production: Photosynthesis is the primary source of energy for most ecosystems. Plants, algae, and some bacteria use photosynthesis to convert sunlight, water, and carbon dioxide into glucose, which serves as a source of energy for themselves and other organisms. This process forms the basis of the food chain, as herbivores consume plants, and carnivores consume herbivores, transferring energy through the ecosystem.

These two reasons highlight the vital role of photosynthesis in sustaining life on Earth by providing oxygen and serving as the foundation of the food chain.

5. In what cell organelle does photosynthesis occur?

  • chloroplast

6. Where do the light reactions of photosynthesis occur?

  • The light reactions of photosynthesis occur in the thylakoid membranes of the chloroplasts.

7. Where do the dark reactions (or Calvin cycle) of photosynthesis occur?

  • The dark reactions (or Calvin cycle) of photosynthesis occur in the stroma of the chloroplasts.

8. What is a pigment?

  • A pigment is a molecule that absorbs certain wavelengths of light and reflects or transmits others.

9. Where is chlorophyll located in the chloroplast?

  • Chlorophyll is located in the thylakoid membranes of the chloroplasts.

10. What is its main function of chlorophyll?

  • The main function of chlorophyll is to absorb light energy for photosynthesis.

11. Why do plants have different pigments?

  • Plants have different pigments to capture a wider range of light wavelengths and maximize energy absorption.

12. What colors of light are best absorbed by chlorophyll a and b?

  • Chlorophyll a absorbs best in the red and blue-violet regions, while chlorophyll b absorbs best in the blue and red-orange regions.

13. What colors of light are best absorbed by carotenoids?

  • Carotenoids absorb best in the blue and green regions of the light spectrum.

14. What is the relationship between energy and wavelength for visible light?

  • The energy of visible light is inversely proportional to its wavelength.

15. What happens during the first stage (Light Reactions) of photosynthesis?

  • During the first stage (Light Reactions) of photosynthesis, light energy is converted into chemical energy in the form of ATP and NADPH.

16. How is water used during the process of photosynthesis?

  • Water is used during photosynthesis as a source of electrons and protons in the light reactions.

17. What happens during the second stage (Calvin Cycle) of photosynthesis?

  • During the second stage (Calvin Cycle) of photosynthesis, CO2 is converted into glucose using ATP and NADPH.

18. What does CO2 fixation mean?

  • CO2 fixation refers to the process of incorporating carbon dioxide into organic molecules during photosynthesis.

19. What is the function of stomata?

  • Stomata are small openings on the surface of leaves that regulate gas exchange, including the uptake of CO2 for photosynthesis.

20. Give an example of a C4 plant.

  • An example of a C4 plant is corn (maize).

21. Give an example of a CAM plant

  • An example of a CAM plant is a succulent like a cactus.

Chapter 4: section 4.2

Define the following terms: producer, autotroph, consumer, heterotroph

  • Producer: An organism that can produce its own food through photosynthesis or chemosynthesis.

  • Autotroph: An organism that can produce its own food using energy from sunlight or inorganic compounds.

  • Consumer: An organism that obtains energy by consuming other organisms.

  • Heterotroph: An organism that cannot produce its own food and relies on consuming other organisms.

Chapter 4: Cellular Respiration

Define: aerobic respiration, kilocalorie, metabolism, fermentation

  • Aerobic respiration: The process of breaking down glucose in the presence of oxygen to produce ATP.

  • Kilocalorie: A unit of energy equal to 1000 calories.

  • Metabolism: The sum of all chemical reactions that occur within an organism.

  • Fermentation: Fermentation is a metabolic process that converts sugar into acids, gases, or alcohol in the absence of oxygen. It is carried out by microorganisms such as yeast or bacteria. This process is used in various industries, including food and beverage production, such as brewing and baking. Fermentation also plays a role in the production of biofuels and certain pharmaceuticals.

1. What are the three main stages of cellular respiration?

  • The three main stages of cellular respiration are glycolysis, the citric acid cycle (also known as the Krebs cycle), and oxidative phosphorylation (also known as the electron transport chain).

2. Which stage of cellular respiration produces the most energy (ATP molecules?)

  • The stage of cellular respiration that produces the most energy in the form of ATP molecules is oxidative phosphorylation (electron transport chain).

3. Describe the overall process of cellular respiration

  • The overall process of cellular respiration involves the breakdown of glucose molecules to produce ATP. It starts with glycolysis, where glucose is converted into pyruvate. Then, in the presence of oxygen, pyruvate enters the mitochondria and undergoes the citric acid cycle, producing NADH and FADH2. These electron carriers then enter the electron transport chain, where ATP is generated through oxidative phosphorylation. The final byproduct of cellular respiration is carbon dioxide and water.