Cell Biology flashcards

All 50 cards

1. Card 1

   Which of the following best describes the primary reason why cell membranes are considered one of the most important evolutionary steps for life on Earth, alongside DNA?

   C. They compartmentalize life processes, creating small, contained spaces where molecular reactions can occur efficiently. This dramatically increases the probability of necessary reactions happening, which is crucial for sustaining life and passing characteristics to the next generation.

2. Card 2

   A researcher observes a biological membrane under an electron microscope and notes the presence of 'bumps' within the bilayer structure. What significant observation does this finding support, according to the lecture material?

   D. It supports the observation that the membrane is not uniform and contains associated molecules, particularly proteins, which are responsible for nearly all membrane functions beyond the lipid bilayer itself.

3. Card 3

   Phospholipids are described as amphipathic molecules. What does this term signify regarding their chemical structure and interaction with water?

   A. Amphipathic means they possess both a hydrophilic (water-loving) polar head region and a hydrophobic (water-repelling) tail region. This dual nature is fundamental to their self-assembly into bilayers or micelles in aqueous environments.

4. Card 4

   If phospholipids are mixed in water-based solutions, they spontaneously adopt higher-order structures. Which of the following is the most stable and biologically significant structure formed, resolving the instability of simple phospholipid films?

   B. The sealed compartment. This structure forms spontaneously from phospholipids in water, effectively creating a stable, enclosed space that is considered a precursor to primitive cells.

5. Card 5

   Which of the following types of molecules is generally impermeable to a phospholipid bilayer, necessitating specialized transport mechanisms?

   D. Large polar molecules and ions. While small hydrophobic and small uncharged molecules can diffuse freely, larger polar molecules like glucose and charged ions like Sodium, Calcium, and Potassium cannot pass through the bilayer without assistance.

6. Card 6

   The Fluid Mosaic Model, proposed by Singer and Nicolson in 1972, significantly advanced our understanding of membrane structure. What key aspect of membrane behavior does this model emphasize?

   C. The fluid nature of the cell membrane, where molecules, including proteins, move in two dimensions, akin to 'icebergs floating in the ocean'. This highlights the dynamic and flexible character of the membrane.

7. Card 7

   Membrane fluidity allows for several types of movement. Which type of movement is described as slow and rare compared to lateral diffusion?

   B. Flip-flop movement. This refers to the movement of a molecule between the two leaflets of the membrane, which is significantly slower and less frequent than lateral diffusion within a single leaflet.

8. Card 8

   Despite the overall fluidity of cell membranes, certain microdomains exhibit stability. What are these stable regions, characterized by higher concentrations of cholesterol, sphingolipids, and saturated phospholipids, known as?

   A. Lipid rafts. These specialized regions accommodate specific proteins and serve as functional hubs for various cellular reactions and signaling events, contributing to membrane heterogeneity.

9. Card 9

   Integral proteins are distinguished from peripheral proteins by their association with the cell membrane. Which statement accurately describes integral proteins?

   A. Integral proteins are embedded through the membrane. They are tightly associated with the lipid bilayer, often spanning it entirely, such as the insulin receptor, and are not easily separated without disrupting the membrane.

10. Card 10

    Cytochrome C is mentioned as an example of a peripheral protein. What characteristic defines its association with the membrane?

    D. Peripheral proteins are loosely or periodically associated with the membrane. They do not penetrate the lipid bilayer but instead bind to its surface, often through non-covalent interactions, and can be released more easily than integral proteins.

11. Card 11

    Which of the following is NOT a primary function regulated by proteins associated with cell membranes?

    C. Storing genetic information for replication. While DNA carries the code for reactions, the storage and replication of genetic information are primarily functions of DNA and the nucleus, not directly regulated by membrane proteins.

12. Card 12

    A cell needs to transport glucose into its cytoplasm from an area of higher concentration outside the cell, but glucose cannot freely cross the plasma membrane due to its charge. Which transport mechanism is most likely employed?

    B. Facilitated Diffusion. This process uses specific proteins, like GLUTs, to assist the movement of larger, polar, or charged molecules down their concentration gradient without requiring cellular energy (ATP).

13. Card 13

    What is the key distinguishing feature between simple diffusion and facilitated diffusion across a cell membrane?

    A. Simple diffusion does not require assistance from membrane proteins, while facilitated diffusion does. Both move molecules down their concentration gradient without energy, but facilitated diffusion is necessary for molecules that cannot pass the bilayer unaided.

14. Card 14

    Active transport is a crucial mechanism for cells to maintain specific intracellular concentrations of molecules. What is the defining characteristic of active transport that differentiates it from passive transport methods?

    B. Active transport moves molecules against their concentration gradient and requires energy, typically in the form of ATP. This allows cells to accumulate substances even when their external concentration is lower than internal.

15. Card 15

    The lecture highlights that cell membranes are impermeable to ions. If a cell needs to move sodium ions from a region of low concentration to a region of high concentration, which transport mechanism would be necessary?

    D. Active Transport. Moving ions against their concentration gradient requires energy and specialized protein pumps, which are characteristic of active transport.

16. Card 16

    Which statement accurately describes the role of non-covalent bonds in maintaining the structure of biological membranes?

    A. Non-covalent bonds, such as van der Waals forces and hydrogen bonds, hold together the thin film of specialized lipids in the membrane. These weak interactions allow for the membrane's fluidity and dynamic nature.

17. Card 17

    The complexity of a eukaryotic cell, with its various organelles like the nucleus and mitochondria, is heavily reliant on membranes. What is the primary benefit of this extensive compartmentalization?

    C. It allows the cell to perform many different life processes in ever more confined spaces, each optimized for the specific reactions it contains. This enhances efficiency and prevents interference between incompatible reactions.

18. Card 18

    Which of the following phospholipid types is NOT explicitly mentioned in the source notes as contributing to membrane composition?

    D. Phosphatidylglycerol. The lecture lists Phosphatidylcholine, Phosphatidylserine, Phosphatidylethanolamine, Phosphatidylinositol, and Sphingomyelin, along with Cholesterol, but not Phosphatidylglycerol.

19. Card 19

    The experiment by Fry and Edinin in 1970, involving fused cells with different fluorescent labels on their membrane proteins, provided key evidence for what characteristic of cell membranes?

    B. Membranes are highly dynamic. The even distribution of fluorescent labels over time in the heterokaryon demonstrated that membrane proteins are not static but can move within the fluid lipid bilayer.

20. Card 20

    If a cell's environment suddenly becomes hypertonic, causing water to move out of the cell, which transport mechanism is responsible for this water movement?

    A. Osmosis. Osmosis is the specific term for the movement of water across a semi-permeable membrane from an area of higher water concentration to an area of lower water concentration, a form of passive transport.

21. Card 21

    Cholesterol plays a significant role in membrane structure and function. Which of the following is a described function of cholesterol within the cell membrane?

    C. It can make a membrane firm, protect it from damage, and helps bind certain proteins. Cholesterol's presence modulates membrane fluidity and stability, preventing extreme changes in either.

22. Card 22

    The formation of micelles is one possible outcome when amphipathic phospholipids are mixed in water. What is the characteristic structure of a micelle?

    A. Small spheres with a hydrophobic core. In micelles, the hydrophobic tails of the phospholipids cluster together in the interior, shielded from water, while the hydrophilic heads face outwards towards the aqueous environment.

23. Card 23

    Why is the regulation of intra-cellular and intra-organelle spaces by specialized transport mechanisms crucial, given the properties of the phospholipid bilayer?

    B. Because the bilayer is impermeable to larger polar molecules and ions. This impermeability means that cells and organelles cannot passively maintain their internal compositions and must actively control the movement of these essential substances.

24. Card 24

    The concept of 'lipid rafts' in membranes is significant because:

    C. They provide functional regions where different reactions and signaling events can occur by accommodating specific proteins. Lipid rafts create stable microdomains within the fluid membrane, allowing for localized and organized cellular processes.

25. Card 25

    What is the primary energy source typically used for active transport mechanisms in cells?

    A. ATP (Adenosine Triphosphate). Active transport requires energy to move molecules against their concentration gradient, and this energy is commonly supplied by the hydrolysis of ATP.

26. Card 26

    Which of the following best describes the primary role of integral proteins in a cell membrane?

    A. Integral proteins are embedded through the membrane and play crucial roles in functions like receptor binding, such as the insulin receptor. They are not merely loosely associated.

27. Card 27

    A cell needs to move a large, polar molecule from an area of low concentration outside the cell to an area of high concentration inside the cell. Which transport mechanism would most likely be employed?

    D. Active transport is the only mechanism listed that can move molecules against their concentration gradient, which is necessary when moving from low to high concentration. This process requires energy.

28. Card 28

    What is the primary difference between primary active transport and secondary active transport?

    A. Primary active transport directly uses energy, typically from ATP hydrolysis, to move solutes. Secondary active transport, in contrast, harnesses energy from an existing electrochemical gradient, often created by primary active transport.

29. Card 29

    A mutation in the CFTR protein leads to Cystic Fibrosis. Based on the provided notes, what type of transport system is the CFTR protein, and what is its primary function?

    C. The CFTR protein is described as a primary active transport system that moves Chloride ions out of the cell. Its disruption impairs the balance of salt and water on many body surfaces.

30. Card 30

    Which of the following molecules can typically pass through a cell membrane via simple diffusion?

    B. Simple diffusion allows small, non-polar molecules like O2 and CO2 to move directly through the lipid bilayer down their concentration gradient. Large polar molecules and ions require assistance.

31. Card 31

    A patient is diagnosed with a condition affecting glucose uptake into cells, despite normal extracellular glucose levels. Which membrane protein is most likely impaired?

    D. GLUTs (Glucose Transporters) are specifically responsible for facilitating the transport of glucose into cells down its concentration gradient. Their impairment would hinder glucose uptake.

32. Card 32

    What is the approximate net charge difference across the membrane of a neuron or muscle cell at rest, and what causes this polarization?

    C. The net charge difference is about -70mV, with the inside being more negative. This polarization is primarily established by the combined action of the Sodium-Potassium Transporter and Potassium 'Leak' Channels, leading to a net efflux of positive charge.

33. Card 33

    The Sodium-Potassium Transporter is an example of which type of transport, and what is its specific ion movement?

    A. The Sodium-Potassium Transporter is a primary active transport system that moves three sodium ions out of the cell and two potassium ions into the cell, utilizing ATP directly.

34. Card 34

    How does the Potassium 'Leak' Channel contribute to the resting membrane potential of -70mV, beyond the -5mV established by the Sodium-Potassium Transporter?

    B. The Potassium 'Leak' Channel allows potassium ions to move down their concentration gradient, from high concentration inside the cell to lower concentration outside. This continuous efflux of positive charge significantly contributes to the more negative resting membrane potential.

35. Card 35

    Which statement accurately describes the role of membrane potential in cellular function?

    C. Membrane potential, the potential energy in an electrochemical gradient, is crucial for various physiological processes. It drives ATP formation in mitochondria, enables neuronal action potentials, and controls heart contractions.

36. Card 36

    What would be the immediate consequence if a cell's Sodium-Potassium Transporter suddenly ceased to function?

    A. The Sodium-Potassium Transporter actively moves three sodium ions out and two potassium ions in. If it stopped, sodium would accumulate inside the cell and potassium would decrease inside, disrupting the electrochemical gradients crucial for membrane potential.

37. Card 37

    Facilitated diffusion differs from simple diffusion in which key aspect?

    B. Facilitated diffusion requires the assistance of proteins (like transporters or channels) to move molecules, even though it still moves them down their concentration gradient and does not require direct energy input. Simple diffusion does not require protein assistance.

38. Card 38

    A cell is exposed to a toxin that specifically inhibits ATP hydrolysis. Which membrane transport mechanism would be most directly and severely affected?

    A. Active transport, particularly primary active transport, directly relies on ATP hydrolysis to provide the energy needed to move molecules against their concentration gradient. Without ATP, these pumps would cease to function.

39. Card 39

    Mitochondria generate a membrane potential (ΔΨm). What is the primary mechanism for generating this potential?

    D. The mitochondrial membrane potential (ΔΨm) is generated by the electron transport chain, which actively accumulates positively charged hydrogen ions (protons) across the inner mitochondrial membrane.

40. Card 40

    Why are membranes considered an important evolutionary event supporting cellular life?

    B. Membranes compartmentalize life processes into small, defined spaces, allowing reactions to occur efficiently and creating distinct internal environments necessary for cellularity. They also regulate what enters and leaves the cell.

41. Card 41

    If a cell has a high concentration of a specific amino acid outside the cell and needs to transport it inside, but the amino acid is charged, which mechanism is most likely to be used if the cell also has a high extracellular sodium concentration?

    C. Secondary active transport is often used to move charged molecules like amino acids against their concentration gradient by coupling their movement to the movement of another ion (like sodium) down its electrochemical gradient.

42. Card 42

    A disease known as Long QT Syndrome is associated with abnormal repolarization of cardiomyocytes. Based on the notes, what fundamental cellular process is disrupted in this condition?

    B. Long QT Syndrome involves abnormal repolarization, which is a critical aspect of how cardiomyocytes change their electrical voltage. This indicates a disruption in the control and maintenance of the membrane potential, essential for heart contractions.

43. Card 43

    Which of the following accurately describes the 'fluidity' of cell membranes?

    C. Cell membranes are fluid, meaning their components can move laterally within the plane of the membrane. However, they also possess stable regions, such as lipid rafts, which have distinct compositions and functions.

44. Card 44

    Consider a scenario where a drug prevents the binding of glucose to GLUT transporters. What would be the immediate effect on glucose transport into cells?

    B. GLUT transporters are essential for facilitating glucose entry into cells. If glucose cannot bind, facilitated diffusion of glucose would be inhibited, leading to a decrease in intracellular glucose levels despite an extracellular concentration gradient.

45. Card 45

    What distinguishes peripheral proteins from integral proteins in terms of their association with the cell membrane?

    A. Peripheral proteins are loosely or periodically associated with the membrane surface, often interacting with integral proteins or the lipid head groups. Integral proteins, conversely, are embedded within or span the lipid bilayer.

46. Card 46

    Why are ions unable to freely pass across the cell membrane, despite their electrochemical properties?

    C. Ions are charged molecules, and the hydrophobic interior of the lipid bilayer acts as a barrier to their passage. They require specific transporter systems or channels to move across the membrane.

47. Card 47

    If a cell's internal environment becomes excessively negative due to an uncontrolled efflux of positive ions, what term describes this state relative to the normal resting potential?

    D. Hyperpolarization refers to a state where the membrane potential becomes even more negative than the resting potential. This would occur if there was an uncontrolled efflux of positive ions, making the inside of the cell more negative.

48. Card 48

    Which statement correctly identifies a key component of membrane structure and its role?

    B. Cholesterol is a vital component of cell membranes, contributing to their fluidity and stability. It helps regulate membrane permeability and ensures proper membrane function.

49. Card 49

    The concept of 'raft biology' is mentioned in relation to complex signaling hubs like the T-cell Receptor. What does understanding raft biology primarily contribute to?

    A. Understanding raft biology is important for comprehending a wide range of cellular processes, including development and immunity, as these stable regions within the membrane serve as platforms for specific protein interactions and signaling events.

50. Card 50

    A cell needs to rapidly move a large volume of water across its membrane to maintain osmotic balance. Which mechanism is primarily responsible for this movement?

    B. Osmosis is the specific term for the movement of water across a semi-permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration), often facilitated by aquaporins (though not explicitly mentioned, it's the primary water transport).

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