Capitolo 2

Question 1

What are the main structural components of a cell?

Answer 1

The main structural components of a cell include the plasma membrane, cytoplasm, nucleus, and various organelles (e.g., mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes).

Question 2

What is the function of the plasma membrane?

Answer 2

The plasma membrane regulates the movement of substances in and out of the cell, maintaining homeostasis and facilitating cell communication through receptors.

Question 3

How does the fluid mosaic model describe the plasma membrane?

Answer 3

The fluid mosaic model describes the plasma membrane as a dynamic structure composed of a phospholipid bilayer with embedded proteins that can move laterally, creating a “mosaic” appearance.

Question 4

What is the role of proteins in the plasma membrane?

Answer 4

Proteins in the plasma membrane serve various functions, including acting as receptors, channels for transport, enzymes, and structural components.

Question 5

How do integral and peripheral proteins differ in their functions?

Answer 5

Integral proteins span the membrane and are involved in transport and communication, while peripheral proteins are attached to the membrane surface and primarily provide structural support or assist with signaling.

Question 6

What is the significance of the phospholipid bilayer in cellular function?

Answer 6

The phospholipid bilayer provides a barrier that separates the internal environment of the cell from the external environment, allowing for selective permeability and maintaining concentration gradients.

Question 7

What are the main functions of the cytoplasm?

Answer 7

The cytoplasm provides a medium for chemical reactions, houses organelles, and facilitates movement of materials within the cell.

Question 8

What is the purpose of the cytoskeleton, and what are its main components?

Answer 8

The cytoskeleton provides structural support, facilitates cell movement, and aids in intracellular transport. Its main components are microtubules, microfilaments, and intermediate filaments.

Question 9

How do microtubules, microfilaments, and intermediate filaments contribute to cell structure?

Answer 9

Microtubules provide rigidity and shape,
microfilaments (actin filaments) assist in cell movement and shape changes, and intermediate filaments provide mechanical support and stability.

Question 10

What are mitochondria, and how do they generate ATP?

Answer 10

Mitochondria are organelles that produce ATP through oxidative phosphorylation, utilizing energy derived from the breakdown of nutrients during cellular respiration.

Question 11

What role do lysosomes play in cellular function?

Answer 11

Lysosomes contain digestive enzymes that break down waste materials and cellular debris, playing a key role in recycling cellular components.

Question 12

What is the difference between rough and smooth endoplasmic reticulum?

Answer 12

Rough endoplasmic reticulum is studded with ribosomes and is involved in protein synthesis, while smooth endoplasmic reticulum lacks ribosomes and is involved in lipid synthesis and detoxification.

Question 13

How do ribosomes contribute to protein synthesis?

Answer 13

Ribosomes translate mRNA into polypeptide chains by linking amino acids in the order specified by the mRNA sequence.

Question 14

What is the function of the Golgi apparatus in the cell?

Answer 14

The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Question 15

What are the roles of peroxisomes in cellular metabolism?

Answer 15

Peroxisomes contain enzymes that break down fatty acids and detoxify harmful substances, such as hydrogen peroxide.

Question 16

How does the nucleus regulate cellular activities?

Answer 16

The nucleus houses the cell’s genetic material (DNA) and controls cellular activities by regulating gene expression and thus protein synthesis.

Question 17

What is chromatin, and how does it differ from chromosomes?

Answer 17

Chromatin is a complex of DNA and proteins found in the nucleus during interphase, while chromosomes are condensed forms of chromatin visible during cell division.

Question 18

How does the cell cycle contribute to cell growth and division?

Answer 18

The cell cycle includes phases of growth (interphase) and division (mitosis), allowing cells to replicate their DNA and divide to produce new cells.

Question 19

What is apoptosis, and why is it important for cellular health?

Answer 19

Apoptosis is programmed cell death that eliminates damaged or unnecessary cells, playing a crucial role in maintaining tissue homeostasis and preventing disease.

Question 20

What are the differences between prokaryotic and eukaryotic cells?

Answer 20

Prokaryotic cells lack a defined nucleus and membrane-bound organelles, whereas eukaryotic cells have a nucleus and various organelles, allowing for more complex functions.

Question 21

How do transport mechanisms, such as diffusion and osmosis, affect cellular homeostasis?

Answer 21

Diffusion and osmosis regulate the movement of substances across the plasma membrane, helping maintain balance in ion and nutrient concentrations within the cell.

Question 22

What is the role of cell signaling in maintaining cellular functions?

Answer 22

Cell signaling involves communication between cells that regulates various physiological processes, including growth, metabolism, and response to environmental changes.

Question 23

How do receptor proteins on the cell surface facilitate communication between cells?

Answer 23

Receptor proteins bind to specific signaling molecules (ligands), initiating a cascade of cellular responses that affect various cellular functions.

Question 24

What are the differences between active and passive transport mechanisms?

Answer 24

Active transport requires energy (ATP) to move substances against (contro) their concentration gradient, while passive transport does not require energy and moves substances along their gradient.

Question 25

How do endocytosis and exocytosis contribute to cellular transport?

Answer 25

Endocytosis involves the uptake of materials into the cell by engulfing them in vesicles, while exocytosis is the process of expelling materials from the cell by fusing vesicles with the plasma membrane.

Question 26

What are the primary mechanisms of cell locomotion?

Answer 26

The primary mechanisms of cell locomotion include amoeboid movement, ciliary movement, flagellar movement, and muscle contraction.

Question 27

How do amoeboid cells move, and what structures facilitate this movement?

Answer 27

Amoeboid cells move by extending and retracting pseudopodia, which are temporary projections of the cell membrane supported by actin filaments. This movement is facilitated by the cytoskeleton and the fluidity of the cell membrane.

Question 28

What is the role of actin filaments in amoeboid movement?

Answer 28

Actin filaments polymerize at the leading edge of the cell to push the membrane outward, forming pseudopodia. They also interact with myosin to contract and pull the rest of the cell forward.

Question 29

How does the process of pseudopodia formation contribute to amoeboid movement?

Answer 29

Pseudopodia formation allows amoeboid cells to anchor to the substrate and pull themselves forward by extending and retracting these projections in a coordinated manner.

Question 30

What are the differences between amoeboid movement and other forms of cell locomotion, such as ciliary or flagellar movement?

Answer 30

Amoeboid movement is characterized by the use of pseudopodia and is often slower and more variable, while ciliary and flagellar movement involve the coordinated beating of hair-like structures, enabling faster and more directional locomotion.

Question 31

How do chemotaxis and haptotaxis influence cell locomotion?

Answer 31

Chemotaxis is the movement of cells toward or away from chemical signals, while haptotaxis involves movement in response to the adhesion properties of the substrate. Both guide cells to specific locations in response to environmental cues.

Question 32

What role do integrins play in cell movement and adhesion?

Answer 32

Integrins are transmembrane proteins that mediate the attachment of cells to the extracellular matrix and are involved in transmitting signals that promote cytoskeletal reorganization during movement.

Question 33

How do cells use myosin in conjunction with actin for movement?

Answer 33

Myosin motor proteins interact with actin filaments to produce contraction and movement. This interaction allows the cell to generate the force needed to pull the cell body forward during amoeboid movement.

Question 34

What are the steps involved in the amoeboid movement cycle?

Answer 34

• The steps involved in the amoeboid movement cycle include: 1. Extension of pseudopodia (leading edge formation). 2. Adhesion of the pseudopodia to the substrate. 3. Contraction of the cell body, pulling the rear of the cell forward. 4. Retraction of the trailing edge.

Question 35

How do changes in the cytoskeleton contribute to the amoeboid movement of a cell?

Answer 35

Changes in the cytoskeleton, specifically the dynamics of actin filament polymerization and depolymerization, drive the extension and retraction of pseudopodia, enabling movement.

Question 36

What factors can affect the speed and efficiency of amoeboid movement?

Answer 36

Factors include the availability of nutrients, the presence of chemical signals (like attractants or repellents), substrate properties (e.g., stiffness), and the integrity of the cytoskeleton.

Question 37

How does the environment (e.g., substrate type) influence amoeboid locomotion?

Answer 37

The substrate’s texture, stiffness, and chemical composition can affect adhesion strength and the formation of pseudopodia, thus influencing the speed and direction of locomotion.

Question 38

What is the significance of amoeboid movement in immune response, particularly in macrophages?

Answer 38

Amoeboid movement enables macrophages to migrate to sites of infection or injury, allowing them to engulf pathogens and debris through phagocytosis, which is crucial for the immune response.

Question 39

How do amoeboid cells navigate through complex tissue environments?

Answer 39

Amoeboid cells navigate through tissues by sensing chemical gradients (chemotaxis), altering their shape, and using their pseudopodia to maneuver through gaps in the extracellular matrix.

Question 40

What molecular signals trigger amoeboid movement in response to environmental cues?

Answer 40

Molecular signals such as growth factors, chemokines, and other cytokines can activate signaling pathways that promote actin polymerization and guide cell movement toward the source of these signals.

Question 41

How do amoeboid cells perform phagocytosis during their movement?

Answer 41

Amoeboid cells extend pseudopodia to surround and engulf particles (like bacteria or debris), forming a phagosome that is then fused with lysosomes for digestion.

Question 42

What adaptations do amoeboid organisms have for survival in different environments?

Answer 42

Amoeboid organisms may have adaptations such as varied forms of locomotion, different types of pseudopodia (e.g., lobopodia or filopodia), and the ability to modify their membrane composition to respond to environmental changes.

Question 43

How does the study of amoeboid movement contribute to our understanding of cancer metastasis?

Answer 43

Understanding amoeboid movement can provide insights into how cancer cells invade tissues and migrate to distant sites, highlighting potential therapeutic targets to inhibit metastasis.

Question 44

What experimental techniques are used to study cell locomotion and amoeboid movement?

Answer 44

Techniques include time-lapse microscopy, live-cell imaging, transgenic models, fluorescence microscopy, and assays measuring cell migration speed and directionality.

Question 45

How do changes in intracellular calcium levels affect amoeboid movement?

Answer 45

Changes in intracellular calcium levels can influence actin dynamics and myosin activity, affecting the contraction and extension of pseudopodia, thereby modulating the speed and direction of amoeboid movement.

Question 46

What is the role of cholesterol in the plasma membrane?

Answer 46

Cholesterol helps to maintain membrane fluidity and stability, allowing the membrane to remain flexible while also providing structural integrity.

Question 47

How do gap junctions facilitate communication between adjacent cells?

Answer 47

Gap junctions consist of connexin proteins that form channels between adjacent cells, allowing the direct transfer of ions and small molecules, which facilitates coordinated cellular activity.

Question 48

What is the function of cilia and flagella in cellular movement?

Answer 48

Cilia and flagella are motile structures that help propel cells or move substances across cell surfaces. Cilia typically move in a coordinated, wave-like manner, while flagella have a whip-like motion.

Question 49

How do cellular junctions contribute to tissue integrity?

Answer 49

Cellular junctions, such as tight junctions, adherens junctions, and desmosomes, create strong connections between cells, maintaining tissue structure and preventing the leakage of materials between cells.

Question 50

What are the differences between tight junctions, adherens junctions, and desmosomes?

Answer 50

Tight junctions create a seal between adjacent cells to prevent leakage of substances; adherens junctions connect the actin cytoskeletons of neighboring cells, providing mechanical support; desmosomes provide strong adhesion between cells by linking intermediate filaments.

Question 51

How does the sodium-potassium pump function, and why is it important for cellular physiology?

Answer 51

The sodium-potassium pump actively transports sodium ions out of the cell and potassium ions into the cell, maintaining the electrochemical gradient essential for various cellular functions, including nerve impulse transmission and muscle contraction.

Question 52

What is resting membrane potential, and what factors contribute to its establishment?

Answer 52

Resting membrane potential is the electrical charge difference across the plasma membrane of a cell at rest, primarily established by the distribution of potassium and sodium ions, permeability of the membrane to these ions, and the activity of the sodium-potassium pump.

Question 53

How do voltage-gated ion channels operate during an action potential?

Answer 53

Voltage-gated ion channels open in response to membrane depolarization, allowing the influx of sodium ions, which further depolarizes the membrane, followed by the opening of potassium channels to repolarize the membrane.

Question 54

What is the process of transcription, and where does it occur within the cell?

Answer 54

Transcription is the process by which DNA is copied into messenger RNA (mRNA) by RNA polymerase, occurring in the nucleus of eukaryotic cells.

Question 55

What role does RNA play in protein synthesis?

Answer 55

RNA acts as a template for protein synthesis. mRNA carries the genetic information from the DNA to the ribosomes, where tRNA brings the appropriate amino acids to assemble the protein.

Question 56

What are the differences between mRNA, tRNA, and rRNA?

Answer 56

mRNA (messenger RNA) carries genetic information from DNA; tRNA (transfer RNA) transports amino acids to the ribosome during protein synthesis; rRNA (ribosomal RNA) is a structural component of ribosomes and plays a role in protein synthesis.

Question 57

How does the cell respond to stress or damage at the molecular level?

Answer 57

Cells respond to stress or damage by activating stress response pathways, including the upregulation of heat shock proteins, repair mechanisms for damaged proteins and DNA, and, if damage is severe, initiating apoptosis.

Question 58

What are the main differences in energy production between anaerobic and aerobic metabolism?

Answer 58

Anaerobic metabolism occurs without oxygen and produces less ATP (2 ATP per glucose) and lactic acid, while aerobic metabolism requires oxygen and produces significantly more ATP (up to 36 ATP per glucose) through oxidative phosphorylation. Cioè il processo che crea più energia in assoluto.

Question 59

How do environmental factors, such as temperature and pH, influence cellular activity?

Answer 59

Environmental factors like temperature and pH can affect enzyme activity, membrane fluidity, and overall cellular metabolism, impacting cellular functions and health.

Question 60

What mechanisms do cells use to regulate their internal environment (homeostasis)?

Answer 60

Cells maintain homeostasis through feedback mechanisms, ion transport, osmotic balance, temperature regulation, and cellular signaling to respond to changes in their environment.

Question 61

What is the importance of cellular differentiation in multicellular organisms?

Answer 61

Cellular differentiation allows for the development of specialized cells with specific functions, enabling complex tissue and organ formation necessary for multicellular life.

Question 62

How do stem cells differ from differentiated cells in terms of function and potential?

Answer 62

Stem cells have the ability to divide indefinitely and differentiate into various cell types, while differentiated cells have specialized functions and typically cannot revert to a stem cell state.

Question 63

What are the consequences of impaired cellular function on overall health?

Answer 63

Impaired cellular function can lead to various health issues, including metabolic disorders, degenerative diseases, and impaired tissue repair, potentially affecting overall organ function and homeostasis.

Question 64

How do cells communicate with each other through autocrine and paracrine signaling?

Answer 64

Autocrine signaling occurs when a cell secretes signaling molecules that bind to receptors on its own surface, while paracrine signaling involves the release of signals that affect nearby cells.

Question 65

What is the role of the extracellular matrix in supporting cell structure and function?

Answer 65

The extracellular matrix provides structural support, influences cell behavior, facilitates communication between cells, and plays a role in tissue organization and repair.

Question 66

How do reactive oxygen species (ROS) affect cellular function?

Answer 66

ROS can cause oxidative damage to cellular components, including DNA, proteins, and lipids, potentially leading to cell dysfunction, aging, and diseases like cancer.

Question 67

What is the role of heat shock proteins in cellular stress responses?

Answer 67

Heat shock proteins act as molecular chaperones that help refold misfolded proteins and prevent aggregation during cellular stress, thus protecting cells from damage.

Question 68

How do changes in membrane permeability affect cell signaling and homeostasis?

Answer 68

Changes in membrane permeability can alter the flow of ions and molecules, affecting the cell’s resting potential, signaling pathways, and overall homeostasis

Question 69

What is the significance of telomeres in cellular aging and replication?

Answer 69

Telomeres protect the ends of chromosomes from degradation during replication. With each cell division, telomeres shorten, and their length is associated with cellular aging and the limit to the number of times a cell can divide.

Question 70

How do cells respond to changes in nutrient availability?

Answer 70

Cells adapt to changes in nutrient availability by altering metabolic pathways, upregulating or downregulating nutrient transporters, and activating stress response mechanisms to optimize energy production and maintain function.