Cytology
A scientist observes a cell under a microscope and notes the presence of a nucleus, membrane-bound organelles, and linear chromosomes.
Which type of cell is most likely being observed?
A. Prokaryotic cell
B. Eukaryotic cell
C. Viral particle
D. Prion
B. Eukaryotic cell
Eukaryotic cells possess membrane-bound organelles such as mitochondria, the endoplasmic reticulum, and Golgi apparatus. They also contain a true nucleus that houses linear chromosomes.
Prokaryotic cells (bacteria and archaea) differ because they:
Lack a membrane-bound nucleus
Possess circular DNA in a nucleoid region
Lack complex organelles
Viruses and prions are not cells; viruses require host cells to replicate, while prions are infectious proteins.
A drug blocks the electron transport chain in mitochondria.
What immediate effect will occur?
A. Increased glucose uptake
B. Decreased ATP production
C. Increased DNA replication
D. Enhanced protein synthesis
B. Decreased ATP production
The electron transport chain (ETC) produces most ATP during cellular respiration via oxidative phosphorylation.
Steps of respiration include:
Glycolysis (cytoplasm)
Krebs cycle (mitochondrial matrix)
Electron transport chain (inner mitochondrial membrane)
Blocking the ETC stops proton gradients and prevents ATP synthase from generating ATP.
A cell takes in large particles by engulfing them with its membrane.
What process is occurring?
A. Endocytosis
B. Exocytosis
C. Diffusion
D. Osmosis
A. Endocytosis
Endocytosis is the process by which cells internalize substances by forming vesicles.
Types include:
Phagocytosis – ingestion of large particles
Pinocytosis – uptake of fluids
Receptor-mediated endocytosis – selective uptake
Exocytosis is the opposite process, releasing substances outside the cell.
A fertilized egg undergoes rapid cell divisions without increasing in size.
What process is occurring?
A. Gastrulation
B. Cleavage
C. Organogenesis
D. Differentiation
B. Cleavage
Cleavage refers to the early series of rapid mitotic divisions following fertilization. During cleavage:
The zygote divides repeatedly
Cells become smaller but more numerous
The embryo does not increase in overall size
The resulting cells are called blastomeres
Cleavage eventually forms structures such as:
Morula – a solid ball of cells
Blastula / Blastocyst – a hollow structure with a fluid-filled cavity
Gastrulation
Occurs after cleavage and blastula formation. During this stage, the embryo reorganizes to form three germ layers:
Ectoderm → skin and nervous system
Mesoderm → muscles, bones, circulatory system
Endoderm → digestive and respiratory organs
Organogenesis
This stage occurs after gastrulation, when the germ layers develop into specific organs and tissues such as the heart, brain, and lungs.
Differentiation
This refers to the process by which cells become specialized. Although all cells contain the same DNA, different genes are expressed in different cell types, producing specialized cells like neurons, muscle cells, and epithelial cells.
A mutation affects a gene responsible for regulating the timing of embryonic development.
What type of genes are most likely involved?
A. Metabolic genes
B. Structural genes
C. Regulatory genes
D. Housekeeping genes
C. Regulatory genes
Regulatory genes control when and where other genes are expressed during development. They often produce transcription factors that activate or repress gene expression.
A student treats a cell with a chemical that destroys the Golgi apparatus.
Which cellular process will most likely be affected?
A. Protein modification and packaging
B. DNA replication
C. ATP production
D. Lipid synthesis
A. Protein modification and packaging
The Golgi apparatus modifies, sorts, and packages proteins received from the rough endoplasmic reticulum (RER) before sending them to their destinations.
Related organelle functions:
Rough ER – protein synthesis for secretion or membranes
Smooth ER – lipid synthesis and detoxification
Mitochondria – ATP production
A plant cell is exposed to darkness for several hours.
Which process will be directly affected?
A. Glycolysis
B. Photosynthesis
C. Cellular respiration
D. Fermentation
B. Photosynthesis
Photosynthesis requires light energy to drive the light-dependent reactions that produce ATP and NADPH.
Photosynthesis occurs in two stages:
Light reactions – capture sunlight
Calvin cycle – synthesizes glucose
Cellular respiration continues even without light.
During mitosis, sister chromatids separate and move toward opposite poles.
Which stage is this?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
C. Anaphase
During anaphase, spindle fibers pull sister chromatids apart toward opposite poles.
Mitosis stages include:
Prophase
Metaphase
Anaphase
Telophase
During embryonic development, three germ layers form.
Which process forms these layers?
A. Cleavage
B. Fertilization
C. Gastrulation
D. Differentiation
C. Gastrulation
Gastrulation forms the three germ layers:
Ectoderm → skin and nervous system
Mesoderm → muscles and bones
Endoderm → digestive organs
Cells adhere to each other during tissue formation using specialized proteins.
These structures are called:
A. Ribosomes
B. Junctions
C. Lysosomes
D. Vesicles
B. Junctions
Cell junctions allow cells to connect and communicate.
Types include:
Tight junctions – prevent leakage
Desmosomes – provide mechanical strength
Gap junctions – allow communication between cells
A plant cell is placed in a hypertonic solution and begins to shrink.
What cellular process explains this observation?
A. Diffusion
B. Facilitated diffusion
C. Active transport
D. Osmosis
D. Osmosis
Osmosis is the movement of water across a semipermeable membrane from regions of lower solute concentration to higher solute concentration.
In this case:
The external solution has higher solute concentration
Water leaves the plant cell
The cell undergoes plasmolysis
Other solution effects:
Hypotonic solution: cell swells
Isotonic solution: no net water movement
During intense exercise, muscle cells begin producing lactic acid.
Which metabolic pathway is responsible?
A. Krebs cycle
B. Electron transport chain
C. Lactic acid fermentation
D. Photosynthesis
C. Lactic acid fermentation
When oxygen is limited, cells regenerate NAD⁺ through lactic acid fermentation, allowing glycolysis to continue producing ATP.
Other fermentation types:
Alcoholic fermentation – occurs in yeast
Aerobic respiration – occurs when oxygen is available
Fermentation produces much less ATP than aerobic respiration.
A cell actively pumps sodium ions out of the cell using ATP.
What transport mechanism is involved?
A. Diffusion
B. Active transport
C. Facilitated diffusion
D. Osmosis
B. Active transport
Active transport requires energy (ATP) to move molecules against their concentration gradient.
A key example is the Sodium-potassium pump, which maintains ion balance in cells.
Stem cells are unique because they can both divide and specialize.
This ability is called:
A. Differentiation
B. Totipotency
C. Replication
D. Mutation
A. Differentiation
Differentiation allows unspecialized cells to become specialized.
Stem cell categories include:
Totipotent – can form an entire organism
Pluripotent – can form most cell types
Multipotent – limited differentiation
During embryonic development, a group of cells begins to migrate to new locations.
This process is important for forming body structures and is known as:
A. Cell migration
B. DNA replication
C. Diffusion
D. Osmosis
A. Cell migration
Cell migration is significant in shaping tissues and organs during development. Examples include neural crest cell migration in vertebrates.
A mutation prevents the formation of microtubules in a cell.
Which structure would be directly affected?
A. Ribosome
B. Cytoskeleton
C. Lysosome
D. Peroxisome
B. Cytoskeleton
Microtubules are part of the cytoskeleton, which maintains cell shape and enables intracellular transport.
The cytoskeleton includes:
Microtubules – involved in cell division and transport
Microfilaments (actin) – cell movement and contraction
Intermediate filaments – structural stability
Microtubules also form the mitotic spindle during cell division.
Which molecule serves as the primary energy currency of the cell?
A. ATP
B. DNA
C. Glucose
D. NADH
A. ATP
Adenosine triphosphate stores energy in phosphate bonds.
When ATP loses a phosphate group:
ATP → ADP + energy
This energy powers:
Active transport
Biosynthesis
Muscle contraction
DNA replication produces two identical DNA molecules.
This process occurs during which cell cycle phase?
A. S
B. G1
C. G2
D. M
A. S
The S phase (synthesis phase) of the cell cycle is when DNA replication occurs.
Cell cycle phases include:
G1 – growth
S – DNA replication
G2 – preparation for division
M phase – mitosis
Cells in early embryos communicate using chemical signals to determine their fate.
This process is called:
A. Cell signaling
B. Replication
C. Mutation
D. Osmosis
A. Cell signaling
Cell signaling involves communication between cells through signaling molecules.
These signals regulate:
Gene expression
Cell differentiation
Tissue pattern formation
An embryo develops distinct body regions such as head, thorax, and abdomen.
This developmental pattern is controlled by:
A. Metabolic enzymes
B. Lysosomal enzymes
C. Ribosomal proteins
D. Homeotic genes
D. Homeotic genes
Homeotic genes, such as the Hox genes, control the body plan along the anterior-posterior axis.
Mutations in these genes can cause dramatic changes in body structures.
A researcher studies a cell that lacks mitochondria but can still generate ATP through glycolysis.
Which type of cell exhibits this feature?
A. Red blood cells
B. Muscle cells
C. Neurons
D. Liver cells
A. Red blood cells
Mature red blood cells (erythrocytes) lack mitochondria. They rely entirely on glycolysis for ATP production.
This adaptation prevents RBCs from consuming the oxygen they transport.
Other cells such as muscle cells and neurons rely heavily on mitochondrial oxidative phosphorylation.
A toxin blocks the function of ATP synthase. What would be the most immediate effect?
A. Glucose accumulation
B. Increased photosynthesis
C. Increased glycolysis
D. Failure of oxidative phosphorylation
D. Failure of oxidative phosphorylation
ATP synthase uses the proton gradient generated by the electron transport chain to synthesize or produce ATP.
If ATP synthase is inhibited:
Proton gradient builds up
ATP cannot be produced efficiently
Oxidative phosphorylation stops
A mutation prevents ribosomes from functioning properly.
Which process would be directly affected?
A. DNA replication
B. Protein synthesis
C. Lipid metabolism
D. Cellular respiration
B. Protein synthesis
Ribosomes translate mRNA into proteins during the process called translation.
The central dogma of molecular biology describes:
DNA → mRNA → Protein
Thus ribosome malfunction disrupts protein production.
During development, some cells die in a controlled manner to shape tissues.
What is this process called?
A. Necrosis
B. Autolysis
C. Fermentation
D. Apoptosis
D. Apoptosis
Apoptosis is programmed cell death, essential for development.
Examples include:
Formation of fingers by removing webbing between digits
Removal of damaged cells
Necrosis, in contrast, is uncontrolled cell death caused by injury.
A researcher treats cultured muscle cells with a chemical that makes the inner mitochondrial membrane permeable to protons (H⁺). As a result, the proton gradient across the membrane disappears even though electrons continue moving along the electron transport chain.
What will most likely happen to ATP production?
A. ATP production will stop because the proton gradient required for ATP synthase will collapse
B. ATP production will increase because protons move faster across the membrane
C. ATP production will remain unchanged because glycolysis compensates fully
D. ATP production will increase because the Krebs cycle accelerates
A. ATP production will stop because the proton gradient required for ATP synthase will collapse
ATP production in mitochondria depends on a process called chemiosmosis, which was proposed by Peter Mitchell.
During oxidative phosphorylation:
Electrons move through the electron transport chain (ETC) in the inner mitochondrial membrane.
The energy released pumps protons (H⁺) from the mitochondrial matrix into the intermembrane space.
This creates a proton gradient (also called a proton motive force).
Protons then flow back through ATP synthase, driving the production of ATP from ADP.
If the inner membrane becomes permeable to protons, the proton gradient collapses. Without this gradient, ATP synthase cannot function, so ATP production stops even if electrons continue moving through the ETC.
Compounds that cause this effect are called uncoupling agents because they uncouple electron transport from ATP synthesis.