Cellular Physiology Practice Questions

Q: All of the following cell types undergo cell division, EXCEPT:

Cardiac muscle cell. ***Cardiac muscle cell*** - **Cardiac muscle cells** are terminally differentiated and largely lose their ability to divide shortly after birth. - While some limited regenerative capacity exists, they do not undergo significant cell division for repair or growth in the adult heart. *Pericyte* - **Pericytes** are multipotent cells associated with capillaries and postcapillary venules and are involved in angiogenesis and tissue repair. - They can differentiate into **fibroblasts, smooth muscle cells, osteoblasts, and adipocytes**, and their proliferative capacity is crucial for these functions, especially after injury. *Smooth muscle cell* - **Smooth muscle cells** retain their ability to divide throughout life and can proliferate in response to injury or hormonal stimuli. - This proliferative capacity is important for the growth and repair of organs like the uterus and blood vessels, and can contribute to conditions like **atherosclerosis**. *Satellite cell of skeletal muscle* - **Satellite cells** are quiescent muscle stem cells located between the basal lamina and sarcolemma of muscle fibers. - Upon muscle injury, they become activated, proliferate, and differentiate into new muscle fibers, playing a critical role in **skeletal muscle regeneration** and repair.

Q: What is responsible for regeneration of liver cells?

HGF. **HGF** - **Hepatocyte growth factor (HGF)** is the primary growth factor responsible for stimulating hepatocyte proliferation and migration, playing a crucial role in **liver regeneration** after injury or resection. - It acts as a potent **mitogen** for hepatocytes, promoting their entry into the cell cycle and division. *VEGF* - **Vascular endothelial growth factor (VEGF)** is primarily involved in **angiogenesis**, the formation of new blood vessels. - While important for tissue repair, it does not directly stimulate the proliferation of liver cells themselves. *TGF-beta* - **Transforming growth factor-beta (TGF-β)** is generally considered an **inhibitor of cell proliferation** and a promoter of fibrosis in the liver. - It can suppress hepatocyte growth and promote the differentiation of stellate cells into myofibroblasts, leading to **scar formation**. *IFN-γ* - **Interferon-gamma (IFN-γ)** is a cytokine primarily involved in **immune responses** and has anti-proliferative and pro-apoptotic effects on various cell types. - It does not promote liver cell regeneration; instead, it can be involved in liver injury and fibrosis during chronic inflammation.

Q: Which of the following statements is false regarding intracellular receptors?

They are the fastest acting receptors.. ***They are the fastest acting receptors.*** - Intracellular receptors regulate gene expression and protein synthesis, which is a **slow process** taking hours or days to manifest effects. - Receptors like **ligand-gated ion channels** are the fastest acting, producing effects within milliseconds due to direct ion flow. *Act by regulating gene expression* - Intracellular receptors, such as **steroid hormone receptors**, typically bind to their ligands within the cytoplasm or nucleus. - This binding leads to their translocation to the nucleus (if not already there), where they act as **transcription factors** to regulate gene expression. *Glucocorticoid receptors are a type of intracellular receptor.* - **Glucocorticoids** are **lipid-soluble hormones** that can readily cross the cell membrane. - They bind to specific intracellular receptors in the cytoplasm, forming a hormone-receptor complex that then translocates to the nucleus. *DNA contains hormone responsive elements.* - Once the activated intracellular hormone-receptor complex enters the nucleus, it binds to specific sequences on the DNA called **hormone responsive elements (HREs)**. - This binding initiates or represses the transcription of target genes, leading to changes in **protein synthesis**.

Q: Which of the following statements about the Nernst equation is true?

It is used to calculate the equilibrium potential for ions.. ***It is used to calculate the equilibrium potential for ions.*** - The **Nernst equation** specifically determines the **equilibrium potential** (or reversal potential) for an **ion** across a semipermeable membrane, where net movement of that ion ceases. - This potential represents the **electrochemical gradient** required to perfectly balance the concentration gradient of a specific ion. - Formula: **E = (RT/zF) × ln([ion]outside/[ion]inside)**, where E is the equilibrium potential, R is the gas constant, T is temperature, z is the ionic charge, and F is Faraday's constant. *It can be calculated for non-ionic solutions.* - The Nernst equation fundamentally relies on the **charge of ions** and their **concentration gradients** across a membrane. - It describes the electrical potential generated by the movement of **charged species**, making it inapplicable to non-ionic solutions. *All of the options are correct.* - Since some of the other statements are incorrect, this option is invalid. - The Nernst equation has specific applications related to **ionic movement** across membranes. *The Nernst potential for Cl- is always constant regardless of concentration.* - The Nernst potential is directly dependent on the **ion's concentration gradient** across the membrane, as well as its charge and temperature. - Therefore, changes in the **extracellular or intracellular concentrations** of Cl- will indeed alter its Nernst potential.

Q: Which of the following factors does the Nernst equation not depend on?

Presence of non-ionic solutions. ***Presence of non-ionic solutions*** - The **Nernst equation** calculates the **equilibrium potential** for an ion based on its concentration gradient and charge. - It does not consider the presence or effect of **non-ionic solutions** as they do not contribute to the electrochemical gradient of charged particles. *Concentration gradient* - The Nernst equation directly incorporates the **ratio of ion concentrations** inside and outside the cell. - This **concentration difference** is a primary determinant of the chemical driving force for ion movement. *Electric gradient* - The Nernst equation calculates the **electrical potential** (voltage) required to perfectly balance the chemical concentration gradient for a specific ion. - Therefore, the **electric gradient** is what the Nernst equation is designed to determine for a given ion. *Concentration difference across the membrane* - This is synonymous with the **concentration gradient**, which is a crucial component of the Nernst equation. - The formula explicitly uses the **logarithm of the ratio of extracellular to intracellular ion concentrations**.

Q: What is the equilibrium potential for potassium (K+) given an extracellular fluid (ECF) concentration of 4 mEq/L and an intracellular fluid (ICF) concentration of 140 mEq/L?

-90 mV. **-90 mV** - The **Nernst equation** is used to calculate the equilibrium potential: E = (61/z) * log([ion]out/[ion]in). For potassium, the charge (z) is +1. - Plugging in the values: E = 61 * log(4/140) = 61 * log(0.02857) = 61 * (-1.544) ≈ **-94.2 mV**, which is closest to -90 mV. *+60 mV* - This value is close to the **equilibrium potential for sodium**, which has a much higher extracellular concentration and a positive equilibrium potential. - It does not reflect the significant concentration gradient of potassium, where the intracellular concentration is much higher. *-60 mV* - While negative, this potential is **not negative enough** to accurately represent the equilibrium potential for potassium with the given concentrations. - A potential of -60 mV falls between the typical resting membrane potential and the potassium equilibrium potential, indicating other ion influences. *+90 mV* - A positive equilibrium potential for potassium would imply that the **extracellular concentration is significantly higher** than the intracellular concentration, which is incorrect. - This value contradicts the physiological reality of potassium distribution across cell membranes.

Q: Which phase of meiosis includes the stages Leptotene and Pachytene?

Prophase I. ***Prophase I*** - **Leptotene** is the first stage of Prophase I, where chromosomes begin to condense and become visible. - **Pachytene** is a later stage of Prophase I, characterized by the tight pairing of homologous chromosomes and the occurrence of **crossing over** (recombination). *Metaphase I* - During Metaphase I, **homologous chromosome pairs** align at the metaphase plate, not individual chromosomes in various stages of condensation. - This phase follows Prophase I and does not include the substages of synapsis and crossing-over. *Anaphase II* - In Anaphase II, **sister chromatids** separate and move to opposite poles of the cell, which is fundamentally different from the events of homologous chromosome pairing and exchange. - This phase occurs much later in meiosis, after meiosis I has completed. *Telophase II* - Telophase II is the final stage of meiosis, where nuclear envelopes reform around the separated chromatids, and the cells divide, resulting in four haploid cells. - It does not involve the initial condensation and pairing of homologous chromosomes seen in Leptotene and Pachytene.

Q: What is the most common mechanism for transport into the cell?

Diffusion. ***Diffusion*** - **Diffusion** is the most common mechanism as it allows small, lipid-soluble molecules like **oxygen, carbon dioxide**, and other gases to passively move across the cell membrane down their **concentration gradients** without energy expenditure. - Many essential nutrients and waste products rely on this process for cellular entry and exit, making it a fundamental and widespread transport method. *Primary active transport* - **Primary active transport** directly uses **ATP hydrolysis** to move ions or molecules against their **concentration gradients**, such as the **Na+/K+ ATPase pump**. - While critical for maintaining gradients, it is an energy-intensive process and thus not as broadly utilized for general substance movement as passive diffusion. *Antiport* - **Antiport** is a type of **secondary active transport** where two different ions or molecules are transported across the membrane in **opposite directions**, with one moving down its electrochemical gradient to power the other's uphill movement. - This mechanism is specific to certain molecules and gradients, making it less ubiquitous than simple diffusion for overall cellular transport. *Cotransport* - **Cotransport** (also known as symport) is another form of **secondary active transport** where two substances move in the **same direction** across the membrane, with one moving down its electrochemical gradient to drive the other against its gradient. - Like antiport, it is a specialized, energy-dependent process that is not as universally applied as passive diffusion for cell transport.

Q: Which of the following is the MOST important feature of simple diffusion?

Does not require carrier protein. ***Does not require carrier protein*** - **Simple diffusion** directly involves the movement of substances across the lipid bilayer without the need for a **carrier protein** or channel. - This characteristic distinguishes it from **facilitated diffusion** and **active transport**, which both utilize proteins for transport. *Moves against a concentration gradient* - Movement against a **concentration gradient** (from low to high concentration) is characteristic of **active transport**, not simple diffusion. - **Simple diffusion** always occurs down a concentration gradient, from an area of higher concentration to an area of lower concentration. *Easy for non-polar substance* - While simple diffusion is indeed easier for **non-polar substances** due to the lipid nature of the cell membrane, this is a factor influencing the *rate* and *permeability*, not the *most important defining feature* of the process itself. - The fundamental aspect of simple diffusion is the absence of protein involvement, regardless of the substance's polarity. *More effective in thin membranes* - A **thinner membrane** would indeed allow for a faster rate of simple diffusion, following Fick's Law of Diffusion. - However, this describes a condition that *enhances* diffusion rather than being the defining characteristic of the process itself.

Q: What generates intracellular signals when cells are subjected to shear stress?

Integrins. ***Integrins*** - **Integrins** are transmembrane receptors that link the extracellular matrix to the cytoskeleton, acting as mechanosensors. - When cells experience **shear stress**, integrins undergo conformational changes that activate intracellular signaling pathways, mediating cellular responses. - They are the **primary mechanotransducers** that directly sense and convert mechanical forces into biochemical signals. *Cadherins* - **Cadherins** are primarily involved in cell-to-cell adhesion, especially in epithelial tissues, forming adherens junctions. - While they contribute to tissue integrity, their primary role is not in sensing and transducing **shear stress** signals. *Selectins* - **Selectins** are a family of cell adhesion molecules involved in initial leukocyte rolling and adhesion to endothelial cells during inflammation. - They bind to carbohydrates on other cells but are not directly involved in the intracellular signaling response to **shear stress**. *Focal adhesion molecules* - **Focal adhesion molecules** are a complex of proteins that includes integrins along with intracellular adaptor proteins like talin, vinculin, and paxillin. - While focal adhesions are important for mechanotransduction, they represent the **downstream signaling complex** rather than the primary receptor that generates the initial signal. - **Integrins** are the specific transmembrane component that directly senses shear stress and initiates the cascade.

Question 1

All of the following cell types undergo cell division, EXCEPT:

Accepted Answer

Cardiac muscle cell

Answer

Pericyte

Answer

Smooth muscle cell

Answer

Satellite cell of skeletal muscle

Question 2

What is responsible for regeneration of liver cells?

Accepted Answer

HGF

Answer

TGF-beta

Answer

VEGF

Answer

IFN-γ

Question 3

Which of the following statements is false regarding intracellular receptors?

Accepted Answer

They are the fastest acting receptors.

Answer

Act by regulating gene expression

Answer

Glucocorticoid receptors are a type of intracellular receptor.

Answer

DNA contains hormone responsive elements.

Question 4

Which of the following statements about the Nernst equation is true?

Accepted Answer

It is used to calculate the equilibrium potential for ions.

Answer

All of the options are correct.

Answer

It can be calculated for non-ionic solutions.

Answer

The Nernst potential for Cl- is always constant regardless of concentration.

Question 5

Which of the following factors does the Nernst equation not depend on?

Accepted Answer

Presence of non-ionic solutions

Answer

Concentration gradient

Answer

Electric gradient

Answer

Concentration difference across the membrane

Question 6

What is the equilibrium potential for potassium (K+) given an extracellular fluid (ECF) concentration of 4 mEq/L and an intracellular fluid (ICF) concentration of 140 mEq/L?

Accepted Answer

-90 mV

Answer

+60 mV

Answer

-60 mV

Answer

+90 mV

Question 7

Which phase of meiosis includes the stages Leptotene and Pachytene?

Accepted Answer

Prophase I

Answer

Metaphase I

Answer

Anaphase II

Answer

Telophase II

Question 8

What is the most common mechanism for transport into the cell?

Accepted Answer

Diffusion

Answer

Primary active transport

Answer

Antiport

Answer

Cotransport

Question 9

Which of the following is the MOST important feature of simple diffusion?

Accepted Answer

Does not require carrier protein

Answer

Easy for non-polar substance

Answer

Moves against a concentration gradient

Answer

More effective in thin membranes

Question 10

What generates intracellular signals when cells are subjected to shear stress?

Accepted Answer

Integrins

Answer

Focal adhesion molecules

Answer

Cadherins

Answer

Selectins

Cellular Physiology — MCQs

Cellular Physiology — MCQs

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