Prokaryotic vs. Eukaryotic Cells Quiz
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Questions and Answers

The nuclear envelope is composed of what?

  • Two separate phospholipid bilayers (correct)
  • A single phospholipid bilayer
  • A layer of carbohydrates
  • A layer of protein

    • What structure within the nucleus is responsible for synthesizing ribosomal RNA (rRNA)?

  • Chromosomes
  • Nucleolus (correct)
  • Ribosomes
  • Nuclear envelope

    • What is the role of messenger RNA (mRNA) in protein synthesis?

  • Providing structural support for the ribosomes
  • Carrying genetic information from the nucleus to the ribosomes (correct)
  • Acting as a catalyst for protein synthesis
  • Carrying amino acids to the ribosomes

    • Which of the following is NOT a component of the endomembrane system?

    <p>Mitochondria (B)</p> Signup and view all the answers

    What is the primary function of the rough endoplasmic reticulum (ER)?

    <p>Protein synthesis and modification (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the endomembrane system?

    <p>It is primarily found in prokaryotic cells (C)</p> Signup and view all the answers

    What is the primary function of lysosomes?

    <p>Digestion of cellular waste products (B)</p> Signup and view all the answers

    Which type of ribosome is responsible for synthesizing proteins that will function within the cytosol?

    <p>Free ribosomes (C)</p> Signup and view all the answers

    What is the role of the Golgi apparatus in the endomembrane system?

    <p>Modification, sorting, and packaging of proteins (D)</p> Signup and view all the answers

    What is the primary function of transport vesicles?

    <p>Transport of materials between different organelles (A)</p> Signup and view all the answers

    Which of the following correctly describes the flow of information during protein synthesis?

    <p>DNA -&gt; mRNA -&gt; ribosomes (D)</p> Signup and view all the answers

    Which of the following is NOT a function of the smooth endoplasmic reticulum (ER)?

    <p>Protein synthesis (C)</p> Signup and view all the answers

    Which of the following is the correct sequence of events that occur during protein synthesis?

    <p>Transcription, translation, protein folding (C)</p> Signup and view all the answers

    Where in the cell does the assembly of ribosome subunits occur?

    <p>Nucleolus (C)</p> Signup and view all the answers

    What is a key aspect of the endomembrane system that is highlighted by the ER's membrane enclosing a separate space from the cytosol?

    <p>Dividing the cell into functional compartments (A)</p> Signup and view all the answers

    Which of the following is an example of how organelles in the endomembrane system interact?

    <p>Ribosomes synthesize proteins, which are then packaged by the Golgi apparatus (C)</p> Signup and view all the answers

    What is the main structural difference between prokaryotic and eukaryotic cells?

    <p>Prokaryotic cells lack membrane-enclosed organelles. (B)</p> Signup and view all the answers

    Which statement correctly describes prokaryotic cells?

    <p>They generally possess a rigid cell wall. (B)</p> Signup and view all the answers

    Which feature is shared by both prokaryotic and eukaryotic cells?

    <p>Bounded by a plasma membrane. (D)</p> Signup and view all the answers

    What role do antibiotics play in targeting prokaryotic cells?

    <p>They inhibit protein synthesis by targeting prokaryotic ribosomes. (B)</p> Signup and view all the answers

    What composition primarily makes up the internal structure of prokaryotic cells?

    <p>Thick cytosol and ribosomes. (A)</p> Signup and view all the answers

    Why do prokaryotes often have a capsule?

    <p>To help adhere to surfaces or other cells. (B)</p> Signup and view all the answers

    Which of the following statements about the size of prokaryotic cells is correct?

    <p>They are about one-tenth the size of typical eukaryotic cells. (D)</p> Signup and view all the answers

    What is a significant structural component of prokaryotic cells that plays a crucial role in the effects of certain antibiotics?

    <p>Cell wall. (A)</p> Signup and view all the answers

    What is the primary role of smooth endoplasmic reticulum (ER) in hormone synthesis?

    <p>Synthesis of lipid-based hormones. (A)</p> Signup and view all the answers

    What happens to the amount of smooth ER when exposed to drugs or harmful substances?

    <p>It increases, enhancing the detoxification capability. (C)</p> Signup and view all the answers

    Which statement accurately describes the function of rough endoplasmic reticulum (ER)?

    <p>It synthesizes secretory proteins using bound ribosomes. (D)</p> Signup and view all the answers

    What occurs to a polypeptide during its synthesis at the rough ER?

    <p>It is folded and modified into a glycoprotein. (D)</p> Signup and view all the answers

    What is the sequence of events that occur in the Golgi apparatus for protein processing?

    <p>Receiving → modification → dispatching. (C)</p> Signup and view all the answers

    What is one role of the Golgi apparatus in relation to the proteins synthesized in the ER?

    <p>It alters the structure of carbohydrate portions in glycoproteins. (A)</p> Signup and view all the answers

    How does the function of Golgi apparatus vary in high activity secreting cells?

    <p>They have more Golgi stacks. (D)</p> Signup and view all the answers

    What role do molecular identification tags play in the Golgi apparatus?

    <p>They help sort molecules for different destinations. (C)</p> Signup and view all the answers

    What triggers the release of calcium ions from the smooth ER in muscle cells?

    <p>Stimulation by nerve signals. (A)</p> Signup and view all the answers

    What is a common feature of both prokaryotic and eukaryotic cells?

    <p>Presence of ribosomes (C)</p> Signup and view all the answers

    Which of the following is a characteristic unique to prokaryotic cells?

    <p>Lack of a membrane-enclosed nucleus (A)</p> Signup and view all the answers

    What structure is primarily responsible for energy processing in eukaryotic cells?

    <p>Mitochondria (A)</p> Signup and view all the answers

    Which component is part of the eukaryotic cell's structural support system?

    <p>Cytoskeleton (A)</p> Signup and view all the answers

    What feature distinguishes eukaryotic cells from prokaryotic cells?

    <p>Larger size (B)</p> Signup and view all the answers

    During which phase does the DNA in eukaryotic cells become visible as chromosomes?

    <p>Prophase (B)</p> Signup and view all the answers

    What is the function of ribosomes in eukaryotic cells?

    <p>Protein synthesis (A)</p> Signup and view all the answers

    What unique structure do plant cells have that is not found in animal cells?

    <p>Chloroplasts (C)</p> Signup and view all the answers

    What role does the nucleus play in eukaryotic cells?

    <p>Control center for genetic information (B)</p> Signup and view all the answers

    What is one function of the plasma membrane in both types of cells?

    <p>Selective barrier for ions and molecules (C)</p> Signup and view all the answers

    Which of these features is NOT found in prokaryotic cells?

    <p>Organelles such as mitochondria (C)</p> Signup and view all the answers

    How do eukaryotic cells differ from prokaryotic cells regarding DNA organization?

    <p>Eukaryotic DNA is housed in a nucleus (D)</p> Signup and view all the answers

    Which of the following is NOT a function of lysosomes?

    <p>Producing digestive enzymes (B)</p> Signup and view all the answers

    What is the primary role of contractile vacuoles in protists like Paramecium?

    <p>Maintaining cellular balance by expelling excess water (B)</p> Signup and view all the answers

    Which of the following is NOT a function of vacuoles in plants and fungi?

    <p>Producing digestive enzymes (C)</p> Signup and view all the answers

    How do lysosomal storage diseases arise?

    <p>Deficiency in one or more lysosomal enzymes (A)</p> Signup and view all the answers

    How does the large central vacuole contribute to plant growth?

    <p>By absorbing water and increasing cell size (A)</p> Signup and view all the answers

    What is a key difference between the role of vacuoles in animal cells and plant cells?

    <p>Plant vacuoles can store toxic waste products, while animal vacuoles cannot. (C)</p> Signup and view all the answers

    Which of the following best describes the relationship between lysosomes and the endomembrane system?

    <p>Lysosomes are part of the endomembrane system, receiving enzymes processed by the Golgi apparatus. (D)</p> Signup and view all the answers

    Why is the statement 'a food vacuole is part of the endomembrane system' true?

    <p>Food vacuoles are created from the plasma membrane, which is part of the endomembrane system. (A)</p> Signup and view all the answers

    Which of the following processes does NOT occur within the endomembrane system?

    <p>Breakdown of fatty acids (B)</p> Signup and view all the answers

    What is the role of the cytoskeleton in eukaryotic cells?

    <p>To provide structural support and facilitate movement (B)</p> Signup and view all the answers

    What is the primary function of the nuclear envelope?

    <p>To regulate the passage of molecules between the nucleus and the cytoplasm (B)</p> Signup and view all the answers

    Which of the following is NOT a function of the endomembrane system?

    <p>Cellular respiration (C)</p> Signup and view all the answers

    What is the primary function of the plasma membrane in regulating the exchange of materials?

    <p>It acts as a selective barrier, allowing some substances to pass through more easily than others. (C)</p> Signup and view all the answers

    Which of the following is NOT a function of proteins embedded in the plasma membrane?

    <p>Production of phospholipids for membrane synthesis (A)</p> Signup and view all the answers

    The fluid mosaic model describes the plasma membrane as a fluid structure. What feature of the membrane contributes to its fluidity?

    <p>The ability of phospholipids to move laterally within the bilayer (C)</p> Signup and view all the answers

    How does the concept of selective permeability apply to the movement of substances across the plasma membrane?

    <p>The membrane allows only certain substances to pass through based on their size, charge, or polarity. (D)</p> Signup and view all the answers

    What is the primary type of molecule that forms the structural basis of the lipid bilayer in the plasma membrane?

    <p>Phospholipids (B)</p> Signup and view all the answers

    What is the primary driving force that enables the movement of molecules across the plasma membrane in passive transport?

    <p>The concentration gradient of the molecules (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between diffusion and the fluid mosaic model?

    <p>The fluid nature of the membrane allows for diffusion, as molecules can move through the bilayer. (C)</p> Signup and view all the answers

    What is the name of the process that allows water to move across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration?

    <p>Osmosis (D)</p> Signup and view all the answers

    Which of the following scenarios would result in water moving into a cell?

    <p>The cell is placed in a hypotonic solution. (A)</p> Signup and view all the answers

    Which of the following statements best describes the difference between diffusion and facilitated diffusion?

    <p>Diffusion involves movement of small, nonpolar molecules, while facilitated diffusion involves movement of large, polar molecules. (A)</p> Signup and view all the answers

    Which term refers to the surrounding solution's ability to cause a cell to gain or lose water?

    <p>Tonicity (A)</p> Signup and view all the answers

    A cell is placed in a solution with a higher concentration of solutes than inside the cell. Which of the following describes the type of solution the cell is in?

    <p>Hypertonic (B)</p> Signup and view all the answers

    Why is diffusion across a membrane considered passive transport?

    <p>The movement of molecules occurs down their concentration gradient, requiring no energy input from the cell. (C)</p> Signup and view all the answers

    What happens to a plant cell placed in a hypotonic solution?

    <p>The cell swells because water moves in. (D)</p> Signup and view all the answers

    A red blood cell placed in a hypertonic solution will:

    <p>Shrink and become crenated. (B)</p> Signup and view all the answers

    Which of the following is a TRUE statement about osmosis?

    <p>It is driven by the movement of water down its concentration gradient. (A)</p> Signup and view all the answers

    Which process describes the movement of molecules across a membrane with the assistance of transport proteins?

    <p>Facilitated diffusion (C)</p> Signup and view all the answers

    What is the term for the maintenance of stable internal conditions within a cell or organism?

    <p>Homeostasis (D)</p> Signup and view all the answers

    Why is osmosis important for living organisms?

    <p>It helps to maintain water balance within cells and tissues. (C)</p> Signup and view all the answers

    Which of the following statements correctly describes the relationship between osmosis and tonicity?

    <p>Tonicity is a measure of the concentration of solutes in a solution, which influences the direction of water movement during osmosis. (B)</p> Signup and view all the answers

    Which of the following best describes the movement of water during osmosis?

    <p>Water moves from areas of low solute concentration to high solute concentration. (C)</p> Signup and view all the answers

    Imagine you have two solutions separated by a membrane permeable to water but not to a solute. Solution A has a higher concentration of solute than Solution B. What will happen to the water level in Solution A compared to Solution B?

    <p>The water level in Solution A will increase because water will move from Solution B. (C)</p> Signup and view all the answers

    What is the primary function of contractile vacuoles in freshwater Paramecium?

    <p>To expel excess water that enters the cell by osmosis. (B)</p> Signup and view all the answers

    What type of transport protein provides a channel for specific molecules or ions to pass through the membrane?

    <p>Channel protein (C)</p> Signup and view all the answers

    Which of the following molecules would likely require a transport protein to cross a cell membrane?

    <p>Glucose (B)</p> Signup and view all the answers

    Which of the following processes requires energy from ATP?

    <p>Active transport (C)</p> Signup and view all the answers

    What is the primary difference between passive and active transport?

    <p>Active transport moves molecules against their concentration gradient, while passive transport moves molecules down their concentration gradient. (D)</p> Signup and view all the answers

    Which of the following is an example of a molecule that is actively transported across the cell membrane?

    <p>Sodium ions (Na+) (C)</p> Signup and view all the answers

    What is the role of ATP in active transport?

    <p>ATP is used to change the shape of the transport protein, allowing it to move the molecule across the membrane. (C)</p> Signup and view all the answers

    Which of the following scenarios would be considered active transport?

    <p>Sodium ions being pumped out of a cell against their concentration gradient. (C)</p> Signup and view all the answers

    What is the difference between a channel protein and a carrier protein?

    <p>Channel proteins provide a passageway for molecules to move through, while carrier proteins bind to molecules and change shape to transport them. (B)</p> Signup and view all the answers

    Why do cells need to perform active transport?

    <p>To maintain a constant internal environment, even when the external environment changes. (B)</p> Signup and view all the answers

    What is the role of aquaporins in cell membranes?

    <p>They facilitate the rapid diffusion of water molecules across the membrane. (B)</p> Signup and view all the answers

    How do transport proteins contribute to a membrane's selective permeability?

    <p>They provide a specific pathway for certain molecules to cross the membrane, while blocking others. (A)</p> Signup and view all the answers

    Which of the following statements best describes the relationship between active transport and concentration gradients?

    <p>Active transport moves molecules against their concentration gradient, from areas of low concentration to areas of high concentration. (C)</p> Signup and view all the answers

    Why would a cell place calcium ions outside the cell during active transport?

    <p>To maintain a constant internal concentration. (B)</p> Signup and view all the answers

    Which of the following is NOT a form of energy?

    <p>Entropy (A)</p> Signup and view all the answers

    According to the first law of thermodynamics, energy can be ______ but cannot be ______.

    <p>transformed, destroyed (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of organisms as open systems?

    <p>Maintain a constant internal environment (B)</p> Signup and view all the answers

    Why is entropy a relevant principle in the context of energy transformations?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the primary reason why cells are more efficient at converting chemical energy into usable energy than car engines?

    <p>Cells use a more complex and controlled process. (C)</p> Signup and view all the answers

    How does the second law of thermodynamics explain diffusion across a membrane?

    <p>Diffusion increases the entropy of the system by dispersing solute molecules. (D)</p> Signup and view all the answers

    How can cells maintain order in the face of the increasing entropy predicted by the second law of thermodynamics?

    <p>Cells extract ordered matter and energy from their surroundings, releasing disorder as heat. (C)</p> Signup and view all the answers

    What is an important consequence of energy conversions for life?

    <p>Some energy is lost as heat, reducing efficiency and creating disorder. (C)</p> Signup and view all the answers

    How do plant cells use energy to produce their organic molecules?

    <p>They convert light energy into chemical energy through photosynthesis. (D)</p> Signup and view all the answers

    If a cell is considered an open system, what does this imply about its interaction with its environment?

    <p>It exchanges both energy and matter with its environment. (D)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of an endergonic reaction?

    <p>The reaction releases energy into the surroundings. (C)</p> Signup and view all the answers

    Which statement accurately describes the relationship between ATP and cellular work?

    <p>ATP provides energy for cellular work by directly donating its phosphate groups to the work-performing molecules. (A)</p> Signup and view all the answers

    What is the primary role of ATP hydrolysis in cellular processes?

    <p>ATP hydrolysis provides energy to create new chemical bonds. (C)</p> Signup and view all the answers

    Which of the following best describes the relationship between the first and second laws of thermodynamics in cellular processes?

    <p>The first law prevents energy loss, while the second law dictates that energy conversions always result in some energy being lost as heat. (D)</p> Signup and view all the answers

    Which of the following is NOT a consequence of the second law of thermodynamics in biological systems?

    <p>The tendency for biological systems to become increasingly ordered over time. (B)</p> Signup and view all the answers

    Considering the roles of ATP and ADP in energy transfer, which of the following statements is TRUE?

    <p>ATP stores energy in its chemical bonds, which is released when ATP is converted to ADP. (B)</p> Signup and view all the answers

    What is the primary role of ATP in cellular processes?

    <p>ATP provides energy for endergonic reactions by transferring a phosphate group. (B)</p> Signup and view all the answers

    What is the process called where energy released from an exergonic reaction is used to drive an endergonic reaction?

    <p>Energy coupling (D)</p> Signup and view all the answers

    What is the key difference between an exergonic and an endergonic reaction?

    <p>Exergonic reactions release energy, while endergonic reactions require energy. (D)</p> Signup and view all the answers

    What is the specific region on an enzyme where the substrate binds?

    <p>Active site (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the induced fit model of enzyme-substrate interaction?

    <p>The enzyme changes shape slightly to accommodate the substrate, forming a tighter fit. (B)</p> Signup and view all the answers

    What is the role of activation energy in chemical reactions?

    <p>Activation energy is the minimum amount of energy required for reactants to start a reaction. (A)</p> Signup and view all the answers

    How is the activation energy of a reaction lowered by enzymes?

    <p>Enzymes strain or contort the bonds in the substrate, making it more likely to react. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of enzymes?

    <p>Enzymes are permanently consumed during a chemical reaction. (A)</p> Signup and view all the answers

    Which of the following statements best describes the relationship between enzymes and substrates?

    <p>Each enzyme has a specific substrate that fits its active site. (A)</p> Signup and view all the answers

    Which of the following is a correct statement regarding the role of enzymes in cellular processes?

    <p>Enzymes are essential for catalyzing virtually all the chemical reactions that occur in cells. (A)</p> Signup and view all the answers

    What is the primary reason why cells need enzymes to carry out metabolic reactions?

    <p>Enzymes lower the activation energy barrier, making reactions proceed faster. (D)</p> Signup and view all the answers

    What is the relationship between activation energy and the rate of a chemical reaction?

    <p>Higher activation energy leads to a slower reaction rate. (C)</p> Signup and view all the answers

    Which chemical bond is essential for ATP's ability to transfer energy?

    <p>Covalent bond (A)</p> Signup and view all the answers

    What is the term for a molecule that binds to an enzyme and reduces its activity?

    <p>Inhibitor (D)</p> Signup and view all the answers

    Which type of inhibition occurs when an inhibitor binds to the active site of an enzyme, competing with the substrate?

    <p>Competitive inhibition (B)</p> Signup and view all the answers

    Which of the following is NOT a way that cells regulate enzyme activity?

    <p>Changing the temperature of the environment (D)</p> Signup and view all the answers

    What is the main advantage of a cell regulating enzyme activity?

    <p>It ensures that enzymes are active only when they are needed. (C)</p> Signup and view all the answers

    How does an enzyme lower the activation energy of a reaction?

    <p>By providing an alternative pathway for the reaction. (A)</p> Signup and view all the answers

    Which of the following is an example of an inorganic cofactor?

    <p>Iron (C)</p> Signup and view all the answers

    What is feedback inhibition?

    <p>A type of enzyme regulation where the product of a metabolic pathway inhibits an enzyme early in the pathway. (A)</p> Signup and view all the answers

    What happens to an enzyme when it is denatured?

    <p>It loses its shape and function. (D)</p> Signup and view all the answers

    Why is it important for cells to have optimal conditions for enzyme activity?

    <p>All of the above (D)</p> Signup and view all the answers

    Which of the following is an example of an enzyme that functions best at an acidic pH?

    <p>Pepsin (B)</p> Signup and view all the answers

    Which of the following statements is TRUE about cellular respiration?

    <p>It is a process that releases energy from food molecules. (C)</p> Signup and view all the answers

    What is the primary role of breathing in relation to cellular respiration?

    <p>Breathing supplies oxygen needed for cellular respiration. (A)</p> Signup and view all the answers

    Which of the following is NOT a correct statement about photosynthesis and cellular respiration?

    <p>Cellular respiration uses energy from the sun to create glucose. (A)</p> Signup and view all the answers

    Why is the statement 'Plant cells perform photosynthesis, and animal cells perform cellular respiration' misleading?

    <p>Cellular respiration occurs in both plant and animal cells. (A)</p> Signup and view all the answers

    Which of the following best describes the relationship between breathing and cellular respiration?

    <p>Breathing supplies the oxygen needed for cellular respiration. (A)</p> Signup and view all the answers

    Which of the following is a TRUE statement about energy flow and matter cycling in ecosystems?

    <p>Energy flows in a one-way direction through ecosystems, while matter is recycled. (D)</p> Signup and view all the answers

    How are photosynthesis and cellular respiration connected in terms of matter cycling?

    <p>All of the above are correct. (D)</p> Signup and view all the answers

    Which of the following statements BEST describes the relationship between cellular respiration and ATP?

    <p>Cellular respiration produces ATP as a form of energy for the cell. (A)</p> Signup and view all the answers

    How many ATP molecules are produced per glucose molecule during glycolysis?

    <p>2 (A)</p> Signup and view all the answers

    What is the role of NADH and FADH2 in cellular respiration?

    <p>They are electron carriers that donate electrons to the electron transport chain. (C)</p> Signup and view all the answers

    Where does oxidative phosphorylation occur?

    <p>Inner mitochondrial membrane (A)</p> Signup and view all the answers

    What is the role of oxygen in cellular respiration?

    <p>It is the final electron acceptor in the electron transport chain. (A)</p> Signup and view all the answers

    Which of the following statements about substrate-level phosphorylation is TRUE?

    <p>It involves the direct transfer of a phosphate group from a substrate to ADP. (A)</p> Signup and view all the answers

    What is the net gain of ATP molecules per glucose molecule during cellular respiration?

    <p>32 (A)</p> Signup and view all the answers

    How many turns of the citric acid cycle occur for each glucose molecule?

    <p>2 (D)</p> Signup and view all the answers

    Which of the following is a key difference between glycolysis and the citric acid cycle?

    <p>Glycolysis occurs in the cytoplasm, while the citric acid cycle occurs in the mitochondria. (D)</p> Signup and view all the answers

    What is the name of the process by which ATP is generated from the proton gradient across the inner mitochondrial membrane?

    <p>Chemiosmosis (B)</p> Signup and view all the answers

    What is the main function of NAD+ in cellular respiration?

    <p>To transport electrons in the electron transport chain. (B)</p> Signup and view all the answers

    Which of the following is NOT a stage in cellular respiration?

    <p>Calvin Cycle (C)</p> Signup and view all the answers

    Where does glycolysis occur in the cell?

    <p>Cytoplasm (A)</p> Signup and view all the answers

    What is the product of glycolysis that is further oxidized in the next stage of cellular respiration?

    <p>Pyruvate (D)</p> Signup and view all the answers

    What is the role of NADH in glycolysis?

    <p>To carry electrons to the electron transport chain (C)</p> Signup and view all the answers

    What happens to the two molecules of pyruvate produced during glycolysis?

    <p>They are further oxidized in the citric acid cycle. (B)</p> Signup and view all the answers

    What is the role of enzymes in glycolysis?

    <p>To catalyze the chemical reactions (A)</p> Signup and view all the answers

    How does the process of substrate-level phosphorylation differ from oxidative phosphorylation?

    <p>Substrate-level phosphorylation produces ATP through a direct transfer of a phosphate group, while oxidative phosphorylation utilizes the proton gradient. (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the energy payoff phase of glycolysis?

    <p>It produces ATP and NADH through redox reactions. (B)</p> Signup and view all the answers

    What is the main function of the electron transport chain in cellular respiration?

    <p>To generate a concentration gradient of protons across the inner mitochondrial membrane. (D)</p> Signup and view all the answers

    Which of the following is NOT a product of the citric acid cycle?

    <p>Glucose (D)</p> Signup and view all the answers

    What is the primary product of cellular respiration that provides energy for cellular work?

    <p>Adenosine triphosphate (ATP) (D)</p> Signup and view all the answers

    Which of the following is NOT a reactant in cellular respiration?

    <p>Carbon dioxide (CO2) (A)</p> Signup and view all the answers

    What is the approximate efficiency of cellular respiration in converting glucose energy into ATP?

    <p>34% (D)</p> Signup and view all the answers

    What is the name of the process by which electrons are transferred from one molecule to another, like in cellular respiration?

    <p>Redox reaction (D)</p> Signup and view all the answers

    In a redox reaction, what happens to a molecule that is oxidized?

    <p>It loses electrons. (A)</p> Signup and view all the answers

    Which coenzyme plays a key role in accepting electrons during the oxidation of glucose in cellular respiration?

    <p>NAD+ (B)</p> Signup and view all the answers

    What is the final electron acceptor in the electron transport chain during cellular respiration?

    <p>Oxygen (O2) (A)</p> Signup and view all the answers

    What is the role of dehydrogenases in cellular respiration?

    <p>They remove hydrogen atoms from organic molecules. (C)</p> Signup and view all the answers

    How does heat released during cellular respiration contribute to the survival of many animals?

    <p>It helps maintain a constant body temperature. (C)</p> Signup and view all the answers

    What is the primary function of electron transport chains in cellular respiration?

    <p>To generate ATP by using the energy released from electron transfer. (A)</p> Signup and view all the answers

    Which of the following statements about the energy demands of the human body is CORRECT?

    <p>The human body consumes nearly its entire body weight in ATP each day if cellular respiration is not possible. (B)</p> Signup and view all the answers

    What happens to the oxygen atoms that are inhaled during breathing?

    <p>They become part of water molecules produced in cellular respiration. (C)</p> Signup and view all the answers

    Which of the following is the reduced form of NAD+?

    <p>NADH (B)</p> Signup and view all the answers

    What is the consequence of the absence of oxygen during oxidative phosphorylation?

    <p>NADH and FADH2 cannot deliver electrons. (D)</p> Signup and view all the answers

    What total yield of ATP molecules is produced from one glucose molecule during cellular respiration?

    <p>32 ATP (D)</p> Signup and view all the answers

    During which phase of cellular respiration is CO2 produced?

    <p>Oxidation of pyruvate and Citric acid cycle (D)</p> Signup and view all the answers

    Which part of cellular respiration primarily drives ATP production through a H+ gradient?

    <p>Electron Transport Chain (D)</p> Signup and view all the answers

    Study Notes

    Prokaryotic vs. Eukaryotic Cells

    • Prokaryotic cells evolved first, dominating Earth for over 1.5 billion years.
    • Prokaryotic cells, found in Bacteria and Archaea, lack a membrane-bound nucleus and other organelles.
    • Eukaryotic cells evolved from prokaryotic cells around 1.8 billion years ago.
    • Eukaryotic cells, found in Eukarya, have a membrane-bound nucleus and various membrane-bound organelles.
    • Both cell types share basic features: plasma membrane, cytosol, chromosomes, and ribosomes.
    • Prokaryotic cells are significantly smaller than eukaryotic cells, typically one-tenth the size.
    • Prokaryotic DNA is coiled into a nucleoid region rather than a nucleus.
    • Prokaryotic ribosomes are different in structure from eukaryotic ribosomes. This difference is exploited by some antibiotics.
    • Prokaryotic cells often have a rigid cell wall, providing shape and protection. Certain antibiotics target this cell wall.
    • Some prokaryotes have a capsule for adhesion and flagella for movement.
    • Eukaryotic cells have a nuclear envelope, separating the nucleus from the cytoplasm. The cell's DNA is organized into chromosomes.

    Cellular Compartments (Eukaryotic)

    • Eukaryotic cells have internal membranes, creating compartments for different chemical activities.
    • Organelles (e.g., mitochondria, chloroplasts, endoplasmic reticulum, lysosomes, peroxisomes) are enclosed by membranes, each with specific functions.
    • These membranes maintain specific chemical conditions, enabling compartmentalized metabolic function. (e.g., peroxisomes detoxify harmful compounds).
    • Plant cells have unique structures not found in animal cells: cell wall of cellulose, plasmodesmata, chloroplasts, a large central vacuole.
    • Eukaryotic cells have non-membranous structures, like the cytoskeleton, and ribosomes, both free in the cytoplasm and attached to the endoplasmic reticulum.
    • Lysosomes are membrane-bound sacs containing digestive enzymes, produced by the rough ER and processed in the Golgi apparatus. Lysosomes break down food, bacteria, and damaged organelles; they act as cellular recycling centers. Inherited lysosomal storage diseases result from missing lysosomal enzymes, causing undigested material buildup and cellular dysfunction.
    • Vacuoles are large vesicles performing various functions mimicking lysosomes (in animal cells). Plant cells have a large central vacuole for water absorption, chemical storage, and waste disposal. Protist contractile vacuoles maintain water balance. Vacuoles can store protein reserves in seeds, pigments, and compounds that deter herbivores.
    • Peroxisomes are metabolic compartments that do not arise from the endomembrane system; they break down fatty acids and detoxify harmful compounds in the liver.
    • Food vacuoles are formed by pinching in from the plasma membrane; this is a part of the endomembrane system.

    Nucleus and Protein Synthesis:

    • The nucleus contains the cell's genetic instructions (DNA) organized into chromosomes.
    • Chromatin is the complex of DNA and proteins when the cell isn't dividing.
    • The nuclear envelope (double membrane) controls material movement in and out of the nucleus. It is connected to the endoplasmic reticulum.
    • The nucleolus assembles ribosomal RNA (rRNA) from DNA instructions.
    • mRNA carries instructions from DNA in the nucleus to the cytoplasm for protein synthesis.
    • Ribosomes translate mRNA into proteins, following the DNA blueprint.

    Ribosomes and Protein Synthesis

    • Ribosomes build proteins following nucleus instructions.
    • Free ribosomes synthesize proteins for use within the cell.
    • Bound ribosomes synthesize proteins that are either incorporated into membranes or secreted from the cell.
    • Ribosomes interact with mRNA to produce proteins following nucleotide sequences.

    Endomembrane System

    • The endomembrane system is a network of interconnected membranes involved in protein synthesis and molecule processing.
    • It includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, and the plasma membrane.
    • The endoplasmic reticulum (ER) is a major component, consisting of smooth and rough sections.
    • The smooth ER synthesizes lipids and detoxifies harmful substances. It also stores calcium ions.
    • The rough ER synthesizes proteins for secretion or membrane insertion, facilitated by attached ribosomes and packaging into vesicles.
    • Vesicles transport proteins and other molecules between the ER, Golgi, lysosomes, vacuoles, and the plasma membrane. The Golgi modifies, sorts, and packages proteins.

    Golgi Apparatus

    • The Golgi apparatus modifies, sorts, and packages proteins for secretion or delivery to other cellular destinations.
    • It receives products from the ER in transport vesicles.
    • Modifies molecules (adding/removing sugars, phosphate groups).
    • Sorts the modified molecules into transport vesicles for delivery to various destinations.
    • Finished products can be secreted, become part of the plasma membrane, or incorporated into other organelles (e.g., lysosomes).

    Mitochondria and Chloroplasts

    • Mitochondria are energy-processing organelles; they carry out cellular respiration, converting chemical energy from food into ATP; they have an outer and highly folded inner membrane forming cristae, enhancing ATP production. The matrix contains mitochondrial DNA, ribosomes, and enzymes for cellular respiration.
    • Chloroplasts are organelles responsible for photosynthesis, converting light energy into chemical energy; enclosed by two membranes, they contain stroma and thylakoids—chlorophyll molecules trap solar energy inside thylakoid membranes.

    Additional Information

    • Eukaryotic cell structures are grouped by function: genetic control, endomembrane system, energy processing, and structural support/movement. Structural similarities reflect general functions (e.g., manufacturing uses connecting membranes; recycling uses membranous sacs).
    • Cells control enzyme activity through gene switching or enzyme activity regulation. This ensures proper timing and location for enzyme action.

    Plasma Membrane

    • Membranes (e.g., plasma membrane) are fluid mosaics of lipids and proteins. The fluid mosaic model describes a membrane's structure as diverse protein molecules suspended in a fluid phospholipid bilayer.
    • The plasma membrane exhibits selective permeability, regulating the exchange of materials across and between cells.
    • Plasma membrane proteins perform diverse functions: Attachment to the cytoskeleton and extracellular matrix (ECM), signal reception and relay, enzymatic activity, cell-cell recognition, intercellular joining, and transport.
    • The lipid bilayer is a fundamental membrane structure. Hydrophilic heads interact with water, while hydrophobic tails repel water.
    • Passive transport is diffusion without energy input. Molecules diffuse from high to low concentrations. Oxygen and carbon dioxide cross membranes readily. Transport proteins aid polar or charged molecules.
    • Facilitated diffusion is passive transport aided by transport proteins. Aquaporins are transport proteins specialized for water.
    • Osmosis is the diffusion of water across a selectively permeable membrane. Water moves from higher to lower water concentration (or lower solute to higher solute)
    • Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water. Isotonic solutions maintain cell volume. Hypotonic solutions cause water influx, possibly leading to cell lysis (animal) or turgidity (plant). Hypertonic solutions cause water efflux and plasmolysis. Osmoregulation controls water balance; contractile vacuoles in freshwater protists regulate water to prevent cell lysis. Vacuoles can store protein reserves in seeds, pigments, and compounds that deter herbivores.
    • Active transport moves substances against their concentration gradient (low to high), requiring energy (ATP). The sodium-potassium pump is an example of active transport.
    • Diffusion increases entropy: molecules move from concentrated to dispersed states, consistent with the second law of thermodynamics.

    ATP and Energy Coupling

    • ATP, adenosine triphosphate, is the main energy source for cellular activities.
    • ATP consists of adenosine and a tail of three phosphate groups; repulsion between the negative charges stores potential energy.
    • Hydrolysis of ATP (breaking bonds with water) releases energy; it is an exergonic reaction.
    • ATP hydrolysis can be coupled to endergonic reactions (energy-requiring) by transferring a phosphate group (phosphorylation), which energizes molecules.
    • Cells perform three main types of work: chemical, transport, and mechanical.
    • ATP is a renewable resource, continuously generated from exergonic reactions like cellular respiration (glucose breakdown), which bonds phosphates to ADP.
    • ATP hydrolysis releases energy to drive endergonic reactions in a rapid cycle.

    Enzymes and Catalysts

    • Enzymes are biological catalysts, speeding up reactions without being consumed.
    • Most enzymes are proteins, but some are RNA molecules.
    • Enzymes lower activation energy, the energy required for a reaction to begin.
    • This allows reactions to proceed much faster without enzymes.
    • A substrate is a specific reactant an enzyme acts on.
    • An enzyme's active site, a pocket or groove, is specific to its substrate.
    • The induced fit model describes the enzyme changing shape slightly to accommodate the substrate during binding.
    • Optimal enzyme conditions include appropriate temperature and pH.
    • Most human enzymes function best at 35–40°C and a neutral pH.
    • Cofactors, nonprotein helpers, bind to active sites and aid catalysis; some are inorganic (like zinc, iron, copper), others are organic (coenzymes).
    • Vitamins often act as coenzymes or precursors to them.
    • Cells regulate enzyme activity by controlling gene expression, enzyme activity levels, or substrate availability.

    Enzyme Inhibition

    • Inhibitors are chemicals interfering with enzyme activity.
    • Competitive inhibitors resemble substrates, competing for the active site.
    • Noncompetitive inhibitors bind to a different site on the enzyme, altering its shape (and thus influencing active site shape) and reducing the enzyme's effectiveness.
    • Feedback inhibition, when a metabolic pathway product inhibits an earlier step in the pathway, is a way cells regulate metabolism.

    Photosynthesis and Cellular Respiration

    • Life requires energy, provided by photosynthesis and cellular respiration.
    • In most ecosystems, energy originates from the sun.
    • Photosynthesis uses sunlight to convert carbon dioxide and water into organic molecules and oxygen.
    • Cellular respiration consumes oxygen to break down organic molecules into carbon dioxide and water, capturing energy as ATP.
    • Photosynthesis occurs in some prokaryotes and in chloroplasts of plants and algae; cellular respiration happens in many prokaryotes and mitochondria of most eukaryotes (including plants, animals, fungi, and protists).
    • Energy conversions lose some energy as heat. Life on Earth is powered by the sun. Energy flows through ecosystems in one direction. Matter, however, is recycled.
    • Carbon dioxide and water released by cellular respiration are transformed by photosynthesis into sugar and oxygen, used in respiration. These processes illustrate the theme of energy and matter.

    Breathing and Cellular Respiration

    • Respiration, often synonymous with "breathing," involves exchanging gases: an organism inhales oxygen and exhales carbon dioxide.
    • Breathing and cellular respiration are closely related. Lungs take up oxygen, which the bloodstream carries to muscle cells. Cellular respiration in muscles produces ATP, providing muscle cell energy.
    • During cellular respiration, inhaled oxygen atoms become part of water in the cell, while CO2 (derived from glucose) is produced as waste.
    • The bloodstream carries CO2 to lungs for exhalation.

    Cellular Respiration: ATP Production

    • Cellular respiration is the process cells use to produce ATP, the energy currency for cell work.
    • Reactants for cellular respiration are breathing and eating.
    • Primary fuel is glucose, but other organic molecules (fats, proteins, complex carbs) can also be used.
    • Atoms in glucose and oxygen rearrange to form carbon dioxide and water.
    • This exergonic process releases energy stored in glucose; some is stored as ATP, rest released as heat.
    • Cellular respiration is a controlled process, unlike rapid burning of sugar.

    Cellular Respiration Stages

    • Cellular respiration occurs in three main stages. In eukaryotic cells, these stages take place in specific locations; in prokaryotes, the steps occur in the cytosol, with electron transport built into plasma membrane.
    • Stage 1: Glycolysis (cytosol): Glucose is broken down into two pyruvate molecules.
    • Stage 2: Pyruvate oxidation and Citric Acid Cycle (Mitochondria): complete glucose breakdown to CO2. A small amount of ATP is produced. Electrons are released for the next stage.
    • Stage 3: Oxidative Phosphorylation (inner mitochondrial membrane): This stage involves the electron transport chain and chemiosmosis, generating most of the ATP. Electron carriers NADH and FADH2 transfer electrons. Final electron acceptor is oxygen, reduced to form water. Chemiosmosis uses a proton gradient to generate ATP using ATP synthase.

    Glycolysis

    • Glycolysis, "splitting of sugar," involves breaking down one glucose molecule into two pyruvate molecules.

    • Nine enzyme-catalyzed reactions, oxidizing glucose and reducing NAD+ to NADH. The net gain is two molecules of ATP.

    • Substrate-level phosphorylation forms ATP in glycolysis, where an enzyme transfers a phosphate group from a substrate molecule to ADP. Some ATP is produced by substrate-level phosphorylation in other stages but most ATP is formed via electron transport chain.

    • Glucose breakdown to pyruvate releases energy, stored in ATP and NADH. ATP can be used right away; NADH energy is released when electrons move through electron transport chain. Pyruvate still contains about 90% energy from glucose.

    • For each glucose molecule, the molecular products of Glycolysis are two pyruvate molecules, two ATP molecules and two NADH molecules.

    Citric Acid Cycle (Krebs Cycle)

    • Pyruvate, from glycolysis, is transported to mitochondria.
    • Pyruvate oxidation produces acetyl CoA and NADH.
    • Citric acid cycle completes glucose breakdown to CO2; small amounts of ATP are produced. But, it primarily supplies electrons for oxidative phosphorylation
    • For each acetyl CoA, the cycle produces 2 CO2, 1 ATP, 3 NADH and 1 FADH2. Since two acetyl CoA molecules are formed per glucose, the cycle turns twice for each glucose molecule.

    Redox Reactions

    • Redox reactions involve one substance losing electrons (oxidation) and other gaining electrons (reduction).
    • "OIL RIG" (Oxidation Is Loss, Reduction Is Gain) helps remember.
    • In cellular respiration, glucose loses hydrogen atoms and is oxidized to CO2; O2 gains hydrogen atoms and is reduced to H2O. This process releases energy harnessed for ATP production.
    • NAD+ is an important coenzyme that accepts electrons and becomes reduced to NADH.

    Oxidative Phosphorylation & Oxygen

    • Without oxygen (O2) to accept electrons at the end of the electron transport chain, the system cannot function, halting ATP production via oxidative phosphorylation.

    Cellular Respiration Summary

    • Oxygen, the final electron acceptor in the electron transport chain, is essential for oxidative phosphorylation.
    • Carbon dioxide, a byproduct of intermediary compound oxidation, is released during pyruvate oxidation and the citric acid cycle.
    • The lack of oxygen prevents the flow of electrons down the electron transport chain, halting the production of ATP through chemiosmosis.

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    Test your knowledge on the differences between prokaryotic and eukaryotic cells. This quiz covers their structure, evolution, and key features that set them apart. Discover what makes these two types of cells unique in the biological world.

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