Cell physiology basics Practice Questions
39 free Cell physiology basics practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
The basic structural and functional unit of the human body is the:
- A Tissue
- B Organ
- C Cell
- D Organelle
Correct answer: Cell
Cells are the smallest living units capable of performing vital functions. All tissues and organs are composed of cells.
The plasma membrane of a cell is primarily composed of:
- A Continuous protein bilayer
- B Phospholipid bilayer
- C Surface carbohydrate layer
- D Rigid cholesterol matrix
Correct answer: Phospholipid bilayer
The plasma membrane consists of a phospholipid bilayer with embedded proteins. This structure provides selective permeability.
Which component of the plasma membrane is mainly responsible for selective permeability?
- A Cholesterol
- B Glycoproteins
- C Phospholipids
- D Peripheral proteins
Correct answer: Phospholipids
The hydrophobic core of phospholipids restricts passage of polar molecules. This allows selective movement of substances.
The fluid mosaic model describes the plasma membrane as:
- A A rigid, static, unchanging structure
- B A protein-only layer
- C A dynamic lipid-protein mosaic
- D A carbohydrate-rich coating
Correct answer: A dynamic lipid-protein mosaic
The fluid mosaic model emphasizes lateral movement of lipids and proteins. This provides flexibility and functionality to the membrane.
Which organelle is primarily responsible for ATP production?
- A Ribosome
- B Mitochondrion
- C Golgi apparatus
- D Lysosome
Correct answer: Mitochondrion
Mitochondria generate ATP through oxidative phosphorylation. They are often called the powerhouse of the cell.
Ribosomes are directly involved in:
- A Membrane lipid synthesis
- B Protein synthesis
- C DNA replication
- D ATP production
Correct answer: Protein synthesis
Ribosomes translate mRNA into polypeptide chains. This is the process of protein synthesis.
Which organelle modifies and packages proteins for secretion?
- A Endoplasmic reticulum
- B Lysosome
- C Golgi apparatus
- D Nucleus
Correct answer: Golgi apparatus
The Golgi apparatus processes, modifies, and packages proteins. It prepares them for transport or secretion.
The rough endoplasmic reticulum is distinguished by the presence of:
- A Cholesterol
- B Ribosomes
- C Glycogen granules
- D Microtubules
Correct answer: Ribosomes
Rough endoplasmic reticulum has ribosomes attached to its surface. This allows synthesis of membrane and secretory proteins.
Lysosomes primarily function in:
- A Cellular energy production
- B Ribosomal protein synthesis
- C Intracellular digestion
- D Lipid storage
Correct answer: Intracellular digestion
Lysosomes contain hydrolytic enzymes. They digest cellular debris and damaged organelles.
Which organelle contains genetic material and controls cell activities?
- A Mitochondrion
- B Nucleus
- C Golgi apparatus
- D Ribosome
Correct answer: Nucleus
The nucleus houses DNA and regulates gene expression. It acts as the control center of the cell.
Passive transport across the cell membrane does NOT require:
- A A concentration gradient
- B Carrier proteins
- C Energy (ATP)
- D Membrane permeability
Correct answer: Energy (ATP)
Passive transport relies on existing gradients and does not consume ATP. Examples include diffusion and facilitated diffusion.
Facilitated diffusion differs from simple diffusion because it:
- A Requires ATP
- B Occurs against a gradient
- C Uses carrier proteins
- D Moves only ions
Correct answer: Uses carrier proteins
Facilitated diffusion uses specific carrier proteins. However, it still occurs down a concentration gradient.
Active transport is characterized by:
- A Passive movement down a gradient
- B No energy requirement at all
- C Movement against a gradient
- D Non-specific bulk transport
Correct answer: Movement against a gradient
Active transport moves substances against their concentration gradient. This process requires energy, usually from ATP.
The sodium-potassium pump primarily maintains:
- A Cell shape
- B Membrane potential
- C Ribosomal protein synthesis
- D Cell division
Correct answer: Membrane potential
The Na⁺/K⁺ ATPase maintains ionic gradients across the membrane. This is essential for membrane potential and excitability.
Osmosis refers to the movement of:
- A Dissolved solute across a membrane
- B Water across a membrane
- C Charged ions through open channels
- D Proteins via transport vesicles
Correct answer: Water across a membrane
Osmosis is the passive movement of water. It occurs through a semipermeable membrane toward higher solute concentration.
A cell placed in a hypotonic solution will:
- A Shrink
- B Remain unchanged
- C Swell
- D Undergo crenation
Correct answer: Swell
In a hypotonic solution, water enters the cell. This causes the cell to swell and may lead to lysis.
Endocytosis is the process by which a cell:
- A Expels substances
- B Synthesizes proteins
- C Engulfs substances
- D Moves ions actively
Correct answer: Engulfs substances
Endocytosis involves engulfing extracellular material into vesicles. It allows uptake of large particles.
Exocytosis primarily functions to:
- A Remove metabolic waste
- B Secrete substances
- C Digest engulfed particles
- D Generate cellular ATP
Correct answer: Secrete substances
Exocytosis releases substances from the cell. It is important for hormone and neurotransmitter secretion.
Which cytoskeletal element is primarily involved in cell movement?
- A Intermediate filaments
- B Microtubules
- C Microfilaments
- D Centrioles
Correct answer: Microfilaments
Microfilaments, composed of actin, are involved in cell movement and shape. They play a role in muscle contraction and motility.
Apoptosis differs from necrosis because it is:
- A An uncontrolled process
- B Always pathological
- C Programmed cell death
- D Associated with inflammation
Correct answer: Programmed cell death
Apoptosis is a regulated, programmed process. It removes unwanted cells without causing inflammation.
Which organelle is responsible for synthesizing lipids and detoxifying certain chemicals within the cell?
- A Rough endoplasmic reticulum
- B Smooth endoplasmic reticulum
- C Golgi apparatus
- D Lysosome
Correct answer: Smooth endoplasmic reticulum
The smooth endoplasmic reticulum (SER) lacks ribosomes and is the primary site for lipid synthesis, steroid hormone production, and detoxification of drugs and toxins.
What is the primary role of cholesterol within the animal cell plasma membrane?
- A To act as a primary source of energy
- B To catalyze reactions in the cytoplasm
- C To regulate membrane fluidity and stability
- D To facilitate the transport of water across membranes
Correct answer: To regulate membrane fluidity and stability
Cholesterol molecules are interspersed within the phospholipid bilayer, where they help maintain the appropriate level of membrane fluidity across varying temperatures.
Which component of the cytoskeleton is the thinnest and primarily composed of actin subunits?
- A Microtubules
- B Intermediate filaments
- C Microfilaments
- D Myosin filaments
Correct answer: Microfilaments
Microfilaments (actin filaments) are the thinnest cytoskeletal elements and are crucial for cell shape, muscle contraction, and amoeboid movement.
The 'Powerhouse of the cell' produces ATP through which of the following processes?
- A Glycolysis in the cytosol
- B Oxidative phosphorylation
- C Translation at ribosomes
- D Exocytosis of vesicles
Correct answer: Oxidative phosphorylation
Mitochondria generate the majority of the cell's ATP supply through oxidative phosphorylation, which occurs along the inner mitochondrial membrane.
Which of the following best describes the 'Nucleolus'?
- A The primary site of DNA replication within the nucleus
- B A membrane-bound sac used for storing cellular waste products
- C The outer membrane structure surrounding the nucleus
- D An area within the nucleus where ribosomal RNA is synthesized
Correct answer: An area within the nucleus where ribosomal RNA is synthesized
The nucleolus is a dense region within the nucleus responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosome subunits.
Peroxisomes are specialized organelles that primarily function to:
- A Synthesize proteins that are destined for export from the cell
- B Break down fatty acids and neutralize hydrogen peroxide
- C Store calcium ions for muscle contraction signaling
- D Package digestive enzymes into transport vesicles
Correct answer: Break down fatty acids and neutralize hydrogen peroxide
Peroxisomes contain oxidative enzymes (like catalase) that break down fatty acids and convert toxic hydrogen peroxide into water and oxygen.
What happens to a human red blood cell when it is placed in a hypertonic solution?
- A It remains unchanged
- B It swells and eventually bursts (lysis)
- C It divides by binary fission
- D It shrivels due to water loss (crenation)
Correct answer: It shrivels due to water loss (crenation)
In a hypertonic solution, the solute concentration is higher outside the cell than inside, causing water to move out of the cell by osmosis, resulting in crenation.
Which organelle is often referred to as the 'shipping center' of the cell because it modifies and sorts proteins?
- A Golgi apparatus
- B Centrosome
- C Mitochondrion
- D Rough ER
Correct answer: Golgi apparatus
The Golgi apparatus receives proteins from the ER, modifies them (e.g., glycosylation), and packages them into vesicles for their final destination.
The resting membrane potential of a typical cell is primarily established by the leakage of which ion?
- A Potassium (K+)
- B Sodium (Na+)
- C Calcium (Ca2+)
- D Chloride (Cl-)
Correct answer: Potassium (K+)
The resting membrane potential is highly dependent on the outward 'leak' of Potassium ions through non-gated channels down their concentration gradient.
Which structural feature increases the surface area of a cell for efficient absorption?
- A Cilia
- B Flagella
- C Tight junctions
- D Microvilli
Correct answer: Microvilli
Microvilli are finger-like projections of the plasma membrane that significantly increase surface area, commonly found on cells in the small intestine.
Tight junctions are primarily responsible for:
- A Allowing direct electrical communication between adjacent cells
- B Anchoring cells firmly to the extracellular matrix
- C Generating mechanical force for cell contraction
- D Preventing the passage of molecules between adjacent cells
Correct answer: Preventing the passage of molecules between adjacent cells
Tight junctions create an impermeable or semi-permeable seal between adjacent epithelial cells, forcing substances to travel through the cells rather than between them.
Which of the following is true regarding 'Phagocytosis'?
- A It is a form of completely passive cellular transport
- B It involves only the passive intake of small extracellular fluid droplets
- C It is a process used exclusively by specialized immune cells
- D It is the process by which a cell engulfs large solid particles
Correct answer: It is the process by which a cell engulfs large solid particles
Phagocytosis is a type of endocytosis where the cell membrane extends around a large particle (like a pathogen) to form an internal vesicle called a phagosome.
Proteins that are destined to be secreted from the cell are synthesized by:
- A Ribosomes attached to the Rough ER
- B Free-floating ribosomes in the cytosol
- C The Smooth ER
- D The nucleolus
Correct answer: Ribosomes attached to the Rough ER
Ribosomes bound to the rough endoplasmic reticulum synthesize proteins meant for membrane insertion, lysosomal storage, or secretion (exocytosis).
What is the function of 'Gap Junctions'?
- A To provide additional mechanical strength to body tissues
- B To act as a complete physical barrier to ion movement
- C To anchor the nucleus firmly to the surrounding cell plasma membrane
- D To allow the direct flow of ions and small molecules between cells
Correct answer: To allow the direct flow of ions and small molecules between cells
Gap junctions (connexons) are channels that bridge the space between neighboring cells, allowing for rapid electrical and chemical communication (e.g., in cardiac muscle).
The term 'Cytosol' refers specifically to:
- A The fluid portion of the cytoplasm in which organelles are suspended
- B All of the contents contained within the cell membrane, including organelles
- C The interior space enclosed within the nuclear envelope membrane
- D The extracellular fluid surrounding the plasma membrane
Correct answer: The fluid portion of the cytoplasm in which organelles are suspended
Cytosol is the semi-fluid substance of the cytoplasm; whereas 'cytoplasm' includes both the cytosol and the organelles (excluding the nucleus).
Which organelle contains hydrolytic enzymes that break down worn-out organelles and cellular debris?
- A Lysosome
- B Ribosome
- C Vacuole
- D Peroxisome
Correct answer: Lysosome
Lysosomes are acidic organelles containing digestive enzymes that perform autophagy (self-eating) to recycle cellular components.
A phospholipid molecule is 'amphipathic' because it contains:
- A A hydrophilic head and a hydrophobic tail
- B Two identical, non-polar fatty acid tails
- C Only polar, hydrophilic functional groups
- D A protein core surrounded by lipids
Correct answer: A hydrophilic head and a hydrophobic tail
Amphipathic molecules have both a polar (hydrophilic) region and a non-polar (hydrophobic) region, allowing them to form the foundation of biological membranes.
What is the function of the 'Centrioles' during cell division?
- A To form the spindle fibers that separate chromosomes
- B To replicate the cell's DNA before division
- C To produce the cellular energy needed for cytokinesis
- D To synthesize the new cell membrane during division
Correct answer: To form the spindle fibers that separate chromosomes
Centrioles, found within centrosomes, help organize the microtubule assembly that forms the mitotic spindle during mitosis and meiosis.
Which of the following is an example of an 'Inclusion' rather than an organelle?
- A Mitochondrion
- B Golgi complex
- C Glycogen granule
- D Endoplasmic reticulum
Correct answer: Glycogen granule
Cell inclusions are non-living, often temporary chemical substances such as glycogen granules, lipid droplets, or pigments, which are not membrane-bound organelles.