Biology 1406 Exam 2

The correct answer is "some substances can pass through and some cannot." This is because the plasma membrane is selectively permeable, allowing certain substances to pass through while restricting the passage of others. The membrane is made up of a phospholipid bilayer with embedded proteins that regulate the movement of molecules in and out of the cell. Small, non-polar molecules like oxygen and carbon dioxide can freely diffuse across the membrane, while larger molecules and ions require specific transport proteins or channels to cross. This selective permeability is essential for maintaining homeostasis and controlling the internal environment of the cell.

The given equation represents the process of cellular respiration, which is the breakdown of glucose to produce energy in the form of ATP. In this reaction, glucose (C6H12O6) and oxygen (O2) are reactants, and carbon dioxide (CO2), water (H2O), and ATP are products. Since energy is released in this reaction, it is considered exergonic.

The correct answer is that the plasma membrane is composed of two layers of phospholipids and a mosaic of proteins. This is a well-known fact in cell biology. The phospholipid bilayer forms the basic structure of the membrane, with the hydrophilic heads facing outward and the hydrophobic tails facing inward. The proteins are embedded within the phospholipid bilayer and have various functions, such as transport of molecules, cell signaling, and structural support. This structure allows the plasma membrane to regulate the movement of substances in and out of the cell and maintain cellular integrity.

At equilibrium, the movement of solutes across the permeable membrane will continue until the concentrations on both sides of the membrane are equal. Therefore, the number of blue balls in each side of the container will be the same, resulting in 3 blue balls in side A and 3 blue balls in side B.

If the plasma membrane has more saturated fatty acids, it means that there are fewer double bonds between carbon atoms in the fatty acid chains. This results in a more tightly packed arrangement of the fatty acids, making the plasma membrane less fluid. Saturated fatty acids have straight chains that can easily stack together, reducing the movement of the phospholipids in the membrane. As a result, the membrane becomes more rigid and less fluid.

Increasing the substrate concentration in an enzymatic reaction could overcome competitive inhibition. Competitive inhibition occurs when a molecule similar in structure to the substrate binds to the active site of the enzyme, preventing the substrate from binding. By increasing the substrate concentration, the chances of the substrate successfully binding to the active site increase, thereby outcompeting the inhibitor and overcoming the inhibition.

Enzymes increase the rate of a chemical reaction by lowering the energy of activation. The energy of activation is the energy required to start a reaction. By lowering this energy barrier, enzymes make it easier for the reaction to occur, thus increasing the reaction rate. Enzymes achieve this by binding to the reactants and bringing them closer together in a way that facilitates the formation of new bonds or the breaking of existing bonds. This lowers the overall energy required for the reaction to proceed, making it more likely to happen.

An apple up on the apple tree has potential energy because it is in a higher position and can potentially fall down due to gravity. When it falls, its potential energy will be converted into kinetic energy.

Increasing the temperature causes more effective collision between enzyme and substrate. As the temperature increases, the kinetic energy of the molecules also increases. This leads to higher molecular movement and more frequent collisions between the enzyme and substrate. These collisions are necessary for the reaction to occur. Therefore, increasing the temperature enhances the chances of successful collisions, leading to an increasing rate of reaction.

Antiporters are carrier proteins that move two molecules in opposite directions across the cell membrane. They use the energy derived from the movement of one molecule down its concentration gradient to transport the second molecule against its concentration gradient. This process is known as countertransport or exchange transport. Antiporters play a crucial role in various physiological processes, such as the exchange of ions, nutrients, and waste products across cell membranes.

During energy transformation, heat is released to the environment. This occurs when energy changes form from one type to another, such as from chemical energy to heat energy or from mechanical energy to heat energy. Heat is a form of energy that is transferred from a warmer object to a cooler object, and it is often released as a byproduct of various energy conversions.

Catabolic reactions break down larger molecules into smaller ones, releasing energy in the process. This energy is used to produce ATP, which is the main energy currency of cells. Therefore, the given answer "catabolic; breaks down" is correct because catabolic reactions break down molecules and release ATP.

Oxygen (O2) and carbon dioxide (CO2) molecules move in and out of the cell through the process of diffusion. Diffusion is the passive movement of molecules from an area of high concentration to an area of low concentration, down the concentration gradient. In the case of O2 and CO2, they diffuse across the cell membrane, which is selectively permeable to allow the passage of these gases. This process is essential for the exchange of gases between the cell and its surroundings, ensuring that the cell receives oxygen for cellular respiration and removes carbon dioxide waste.

Simple diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration, without the need for transport proteins. On the other hand, facilitated diffusion also involves the passive movement of molecules, but it requires the assistance of transport proteins embedded in the cell membrane. These proteins act as channels or carriers to facilitate the movement of specific molecules across the membrane. Therefore, the correct answer is that simple diffusion requires no transport proteins while facilitated diffusion requires transport proteins.

Passive transport is the movement of materials along the concentration gradient, meaning from an area of high concentration to an area of low concentration, without the need for energy. On the other hand, active transport moves materials against the concentration gradient, meaning from an area of low concentration to an area of high concentration, and requires energy. Therefore, the given answer correctly distinguishes between passive and active transport based on the direction of material movement and the requirement of energy.

When a red blood cell (RBC) with a lower concentration of NaCl (0.9%) is placed in a solution with a higher concentration of NaCl (1.8%), water molecules will move out of the RBC through osmosis. This is because the solution outside the RBC has a higher solute concentration, creating a hypertonic environment. As water leaves the RBC, it will shrink or crenate. Therefore, the correct answer is that the RBC will shrink.

The net movement of the blue solutes is from side A to side B because there is a higher concentration of blue solutes in side A compared to side B. On the other hand, the net movement of the red solutes is from side B to side A because there is a higher concentration of red solutes in side B compared to side A.

The ball rolling on the grass and the person diving in the swimming pool both have kinetic energy. Kinetic energy is the energy possessed by an object due to its motion. In both cases, the ball and the person are in motion, so they possess kinetic energy. The rock sitting at the top of the cliff and the book on a table are not in motion, so they do not have kinetic energy.

O2 is the terminal electron acceptor in aerobic respiration. During aerobic respiration, glucose is broken down in the presence of oxygen to produce ATP, carbon dioxide, and water. Oxygen serves as the final electron acceptor in the electron transport chain, which is the last step of aerobic respiration. It accepts electrons from the electron carriers and combines with protons to form water. Without oxygen, aerobic respiration cannot proceed, and cells would not be able to produce sufficient energy.

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The proton motive force that develops in the electron transport system (ETS) in the mitochondrion is the difference in concentration of H+ (protons) in and out of the inner membrane. This difference in proton concentration is created by the movement of electrons through the ETS, which pumps protons from the matrix to the intermembrane space. The accumulation of protons in the intermembrane space creates an electrochemical gradient, which drives the synthesis of ATP through ATP synthase.

Osmosis is the process by which water molecules move across a membrane from an area of lower solute concentration to an area of higher solute concentration. This movement occurs to equalize the solute concentration on both sides of the membrane. The correct answer is "water" or "H2O" because osmosis specifically refers to the movement of water molecules.

Integral membrane proteins are responsible for the transport of substances across the cell membrane. These proteins are embedded within the lipid bilayer of the membrane and have hydrophobic regions that allow them to interact with the hydrophobic interior of the membrane. They play a crucial role in transporting molecules such as ions, nutrients, and signaling molecules across the membrane, ensuring the proper functioning and homeostasis of the cell. Glycoproteins, peripheral proteins, and intracellular membrane proteins may also have various functions within the cell, but they are not specifically responsible for substance transport across the membrane.

Glucose, being a large and polar molecule, cannot passively diffuse across the cell membrane. Facilitated transport is the process by which glucose is transported inside the cell. This process involves the use of carrier proteins embedded in the cell membrane that bind to glucose molecules and facilitate their movement across the membrane. Unlike active transport, facilitated transport does not require the input of energy. Therefore, facilitated transport is the most suitable explanation for how glucose is transported inside the cell passively.

According to the induce-fit model of enzyme action, the active sites of enzyme change slightly in shape to conform to the shape of the substrate.

Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic respiration uses sulfates and carbonates. This is because aerobic respiration occurs in the presence of oxygen, which acts as the final electron acceptor in the electron transport chain. In contrast, anaerobic respiration occurs in the absence of oxygen, so alternative molecules such as sulfates and carbonates are used as the final electron acceptors. Additionally, aerobic respiration generates more ATP than anaerobic respiration. This is because aerobic respiration produces ATP through oxidative phosphorylation, which generates a larger amount of ATP compared to the substrate-level phosphorylation used in anaerobic respiration.

Oxidizing agents are substances that cause other substances to lose electrons, while they themselves are reduced. In other words, they gain electrons and are reduced, not oxidized. Therefore, the correct answer is False.

Chymotrypsin is denatured at basic pH because it is an enzyme that functions optimally at a slightly acidic pH. Basic pH conditions can disrupt the enzyme's active site and alter its structure, leading to denaturation. Cholinesterase, pepsin, and papsin are not affected by basic pH and can function under a wider range of pH conditions.

As the electrons are passed from one acceptor to another in the Electron Transport System (ETS) in the cristae, they contribute to the pumping of protons (H+) across the inner mitochondrial membrane. This creates a higher concentration of protons outside the cristae compared to inside. Therefore, the H+ concentration inside the cristae decreases as electrons are passed along the ETS.

Plants that survive winter or tolerate cold temperatures have plenty of unsaturated fatty acids in their plasma membranes. Unsaturated fatty acids have double bonds in their carbon chains, which gives them a more fluid and flexible structure. This allows the plasma membranes of these plants to remain functional even in cold temperatures, as they can adjust their fluidity to prevent freezing and maintain membrane integrity. Saturated fatty acids, on the other hand, have no double bonds and tend to have a more rigid structure, making them less suitable for cold tolerance.

Pinocytosis is a bulk transport process performed by cells where they take in droplets of liquids. This process involves the formation of small vesicles that engulf the liquid and bring it into the cell. It is a one-word answer and the correct spelling is important.

The movement of electrons along the electron transport system in cristae generates a proton gradient across the inner mitochondrial membrane. This gradient is established by pumping H+ ions from the matrix (inside of cristae) to the intermembrane space (outside of cristae). The energy released during this process is used to transport H+ from inside of cristae to the outside of the cristae.

Enzymes are catalysts that speed up chemical reactions by decreasing the activation energy required for the reaction to occur. This allows the reaction to proceed more quickly and efficiently. Enzymes are highly specific for their reactions, meaning that each enzyme is designed to catalyze a particular reaction or set of reactions. Additionally, enzymes are not consumed or permanently altered during the reaction, so they can be reused multiple times.

Proteins are broken down into amino acids in order to generate ATP. This process involves the breaking of peptide bonds between the amino acids in the protein molecule. These individual amino acids can then be further metabolized to produce ATP through various metabolic pathways, such as glycolysis and the citric acid cycle. Amino acids are the building blocks of proteins and play a crucial role in energy production within cells.

The examples provided in the answer demonstrate different forms of energy transformation. Burning wood releases heat and light energy, which is a transformation from chemical energy stored in the wood. Plants transform light energy from the sun into chemical energy stored in glucose through photosynthesis. When animals consume plants, the chemical energy in glucose is transformed into ATP, which is a form of energy used by cells. Finally, when animals move, the chemical energy in ATP is transformed into mechanical energy, allowing for physical motion.

Aerobic cellular respiration is the process that generates the most ATP from one molecule of glucose. This process occurs in the presence of oxygen and involves the complete breakdown of glucose to produce a large amount of ATP. On the other hand, fermentation is the process that generates the least ATP from one molecule of glucose. This process occurs in the absence of oxygen and involves the partial breakdown of glucose, resulting in the production of a small amount of ATP.

In prokaryotes, aerobic respiration generates a maximum of 32 ATP molecules from one molecule of glucose. This process involves glycolysis, the Krebs cycle, and the electron transport chain. During glycolysis, 2 ATP molecules are produced, while the Krebs cycle generates 2 ATP molecules. The majority of ATP production occurs in the electron transport chain, where 28 ATP molecules are produced through oxidative phosphorylation. Therefore, the total ATP production in prokaryotes through aerobic respiration is 32 ATP.

When carrot sticks are left in a dish with fresh tap water for several hours, they become stiff and hard because the solution inside the cells of the carrot is hypertonic to fresh tap water. This means that the concentration of solutes inside the carrot cells is higher than that of the tap water. As a result, water from the tap water moves into the carrot cells through osmosis, causing the cells to expand and become stiff and hard.

The level of solution in side A increases because the concentration of protein is higher in side B compared to side A. As the semipermeable membrane is permeable to NaCl and water, but not to protein, water will move from side A to side B in order to dilute the higher concentration of protein. This movement of water causes the level of solution in side A to increase.

Oxidative-level phosphorylation in animal cells takes place in the cristae of mitochondria. Cristae are the folds in the inner membrane of mitochondria that provide a large surface area for the electron transport chain and ATP synthase enzymes to carry out oxidative phosphorylation. This process involves the transfer of electrons through the electron transport chain, which pumps protons across the inner membrane into the intermembrane space. The protons then flow back into the matrix through ATP synthase, driving the synthesis of ATP. Therefore, the cristae play a crucial role in the production of ATP in animal cells.

The net movement of water molecules is from side B to side A because the semipermeable membrane is permeable to water but not to urea. This means that water molecules can pass through the membrane, but urea molecules cannot. As a result, there is a higher concentration of water molecules on side B compared to side A. According to the principle of osmosis, water molecules will move from an area of higher concentration (side B) to an area of lower concentration (side A) in order to equalize the concentrations on both sides.

When H+ goes back inside the membrane through ATP synthase, it combines with ADP (adenosine diphosphate) and inorganic phosphate to form ATP (adenosine triphosphate). ATP is the main energy currency of cells and is used to power various cellular processes.

In feedback inhibition, the final product of a biochemical pathway acts as the inhibitor. This means that when the concentration of the final product reaches a certain level, it binds to and inhibits one of the enzymes in the pathway, effectively shutting down the production of more product. This mechanism helps regulate and maintain homeostasis within the cell or organism by preventing the overproduction of certain molecules.

In the given reaction, C6H12O6 is the reducing agent because it undergoes oxidation by losing electrons to form 6CO2. On the other hand, 6O2 is the oxidizing agent because it undergoes reduction by gaining electrons to form 6H2O.

Exocytosis is the process by which animals secrete digestive enzymes into the stomach and small intestines. During exocytosis, vesicles containing the enzymes fuse with the cell membrane, releasing their contents into the extracellular space. This allows the enzymes to be transported and delivered to the appropriate locations for digestion.

In glycolysis, one molecule of glucose is converted into two molecules of pyruvate. During this process, a net of two molecules of ATP are generated. This occurs through substrate-level phosphorylation, where ATP is directly synthesized from ADP and a phosphate group. Therefore, the correct answer is 2 ATP.

The negative ∆G indicates that the reaction is thermodynamically favorable and spontaneous. This means that the products of the reaction have a lower free energy than the reactants, and the reaction will proceed in the forward direction without the need for external energy input.

The semipermeable membrane only allows water to pass through, not glucose. Therefore, over time, water will move from the side with lower concentration of solute (side A with 1% glucose) to the side with higher concentration of solute (side B with 10% glucose) in order to equalize the concentration. As a result, the concentration of glucose in side A will increase, while the concentration in side B will decrease. At equilibrium, the concentration of glucose in side A and side B will be equal.

Allosteric enzymes have a unique regulatory mechanism where activators and inhibitors bind to a site other than the active site. This means that they do not compete with the substrate for binding in the active site. Instead, the binding of an activator or inhibitor at the allosteric site causes a conformational change in the enzyme, either stabilizing the active form or stabilizing the inactive form. Therefore, the statement that activators and inhibitors compete with the substrate for binding in active sites is false.

Competitive enzyme inhibitors are molecules that bind to the active site of an enzyme and compete with the substrate for binding. This means that they have a similar structure to the substrate and can effectively block the enzyme's active site, preventing the substrate from binding and inhibiting the enzyme's activity. Therefore, the correct answer is "competitive enzyme inhibitor only" as it specifically refers to inhibitors that bind in the active site.