Cell Biology and Immunology Lecture

A comprehensive set of question-and-answer flashcards covering microscopy, cell chemistry, organelles, membrane physiology, cell cycle, stem cells, immunology, inflammation, and tumor immunity as discussed in the lecture.

What is the primary structural difference between prokaryotic and eukaryotic cells?

Prokaryotes lack a nuclear envelope and membrane-bound organelles, whereas eukaryotes possess both.

What is the usual maximum useful magnification of a modern light (bright-field) microscope?

About 1,000×.

Which microscope is routinely used for immunological and histochemical fluorescence studies?

The fluorescence microscope.

On what optical principle does the phase-contrast microscope rely?

It converts differences in refractive index within a transparent specimen into differences in brightness (phase shifts into amplitude).

Which acidic dye commonly stains cytoplasm pink?

Eosin.

In tissue culture, what is the role of the enzyme trypsin?

It dissociates cells by digesting extracellular matrix proteins, allowing them to separate for culture.

Which electron microscope variant provides three-dimensional images of cell surfaces at ≈20,000× magnification?

The scanning electron microscope (SEM).

Name the four chemical elements that together constitute ≈98 % of cell mass.

Oxygen, carbon, hydrogen, and nitrogen.

Which class of macromolecules forms 7–10 % of a cell’s weight and is built from amino acids?

Proteins.

List the two sulfur-containing amino acids.

Cysteine and methionine.

Give one defensive function performed by proteins.

They form antibodies (immunoglobulins) that neutralize foreign antigens.

What are lipoproteins composed of?

A protein covalently or non-covalently linked to lipids.

Which major class of biomolecules is the structural basis of all biological membranes?

Lipids (especially phospholipids and cholesterol).

What is the basic repeating unit (monomer) of nucleic acids?

The nucleotide (a pentose sugar, phosphate group, and nitrogenous base).

Name the three main types of RNA found in cells.

Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

Which organelle is commonly called the “powerhouse of the cell” because it produces most ATP?

The mitochondrion.

What membrane protein anchors ribosomes to the rough endoplasmic reticulum?

Ribophorin.

Give two major functions of the smooth endoplasmic reticulum.

Synthesis of lipids/steroids and detoxification of drugs or toxins.

What are the three possible destinations for vesicles that bud from the trans face of the Golgi apparatus?

Fusion with lysosomes, incorporation into the plasma membrane, or exocytosis to the extracellular space.

Which organelle is packed with ≈40–50 hydrolytic enzymes and can cause autolysis of cells?

The lysosome.

What is the structural form of mitochondrial DNA?

It is circular (double-stranded) DNA.

What term describes a messenger RNA strand with multiple ribosomes attached simultaneously?

A polysome (polyribosome).

Which antibiotic blocks amino-acyl-tRNA entry into the ribosomal A-site?

Tetracycline.

What is the primary function of the centrosome during mitosis?

It nucleates microtubules to form the mitotic spindle.

The 9 + 2 microtubule arrangement is characteristic of which cellular structures?

Motile cilia and flagella.

List three fundamental functions of the plasma membrane.

Selective transport, cell recognition/signalling, and structural boundary protection.

What is the human name for the major histocompatibility complex (MHC)?

Human leukocyte antigens (HLA).

Define passive immunity.

Short-term protection conferred by transfer of preformed antibodies or sensitized cells from another source.

Which follicular stromal cells present un-internalized antigen to B lymphocytes?

Follicular dendritic cells.

Which leukocyte type is usually the first to arrive at sites of acute inflammation?

Neutrophils (polymorphonuclear leukocytes).

Which filamentous protein forms the contractile ring that produces the cleavage furrow in cytokinesis?

Actin (with myosin).

During which specific phase of the cell cycle does DNA replication occur?

The S phase of interphase.

Which tumor-suppressor gene halts the cell cycle in G1 or triggers apoptosis?

TP53 (p53).

What is the biological term for programmed, genetically regulated cell death?

Apoptosis.

What are totipotent stem cells able to generate?

All cell types of the embryo plus extra-embryonic tissues, forming a complete organism.

Name the enzyme that elongates telomeres in stem cells and some cancer cells.

Telomerase.

What is the final complement pathway product that perforates target cell membranes?

The membrane attack complex (MAC).

Which immunoglobulin class mediates allergic reactions and activates eosinophils?

IgE.

Give one example of an onco-fetal antigen re-expressed in certain tumors.

Alpha-fetoprotein (AFP) or carcinoembryonic antigen (CEA).

Which cellular process engulfs solid particles by membrane invagination forming a phagosome?

Phagocytosis.

Define facilitated diffusion across a membrane.

Passive movement of molecules down their concentration gradient via a specific carrier protein without energy expenditure.

Which membrane proteins create ion channels that allow free passage without ATP usage?

Channel (pore-forming) proteins.

What is exchanged by the Na⁺/K⁺ pump for each ATP hydrolyzed?

Three Na⁺ ions are pumped out and two K⁺ ions pumped into the cell.

List the four classical clinical signs of acute inflammation.

Rubor (redness), calor (heat), tumor (swelling), and dolor (pain).

Which connective-tissue cells synthesize collagen during wound healing and scar formation?

Fibroblasts.

What microscope uses ultraviolet light to excite fluorochromes in a specimen?

The fluorescence microscope.

Which amino acid has only hydrogen as its side-chain (R group)?

Glycine.

Which classical staining method impregnates neurons with silver to reveal morphology?

The Golgi (silver impregnation) technique.

During anaphase, which motor protein helps pull chromosomes toward spindle poles?

Dynein (minus-end–directed motor).

What is the clinical term describing a benign tumor’s confinement to its original site?

It is said to be encapsulated and non-invasive (benign).

In which mitotic phase do chromosomes line up on the metaphase plate?

Metaphase.

Which sterol modulates membrane fluidity in animal cells?

Cholesterol.

Where inside the nucleus are rRNAs transcribed and partially assembled?

In the nucleolus.

Name the lysosomal storage disease caused by acid α-glucosidase deficiency.

Pompe disease.

Which organelle is especially abundant in adrenal cortex cells to synthesize steroid hormones?

Smooth endoplasmic reticulum.

What is the sedimentation coefficient of an intact eukaryotic ribosome?

80 S (with 60 S and 40 S subunits).

Which physical property of the lipid bilayer allows it to reseal after minor injury?

Membrane fluidity (self-healing due to hydrophobic interactions).

Metabolically active cells typically contain what percentage of water?

About 75–85 %.

Which light-microscope technique shows bright specimens against a dark background?

Dark-field microscopy.

What analytical technique separates complex molecular mixtures based on differential affinity for a stationary phase and a mobile phase?

Chromatography.