Histo(Cell Injury)

What are the three basic structural components of a cell?

Plasma membrane, cytoplasm, and nucleus.

What surrounds a normal cell?

A plasma membrane.

What does the plasma membrane enclose?

The cytoplasm and nucleus.

What does the nucleus contain?

Chromatin (DNA + histones) and sometimes nucleoli.

What is chromatin composed of?

DNA and histone proteins.

What are chromocenters?

Large condensed clumps of chromatin.

What does the cytoplasm contain?

Cytosol and cellular organelles.

Name the major organelles found in the cytoplasm.

Mitochondria, endoplasmic reticulum, ribosomes, Golgi apparatus, lysosomes, and peroxisomes.

What is the plasma membrane composed of?

A lipid bilayer with embedded proteins.

List the major functions of the plasma membrane.

Transport, cell recognition, adhesion, and receptor-mediated processes.

What are the three major components of the cell?

Nucleus, cytoplasmic organelles, and plasma membrane.

What are the components of the nucleus?

Nucleolus, nuclear membrane, and chromatin.

Name the cytoplasmic organelles.

Mitochondria, rough ER, smooth ER, Golgi apparatus, lysosomes, peroxisomes, microtubules, microfilaments, and intermediate filaments.

What is the function of the nucleus?

It contains DNA and directs all cellular activities.

What is heterochromatin?

Dark-staining, transcriptionally inactive chromatin.

What is euchromatin?

Light-staining, transcriptionally active chromatin that forms mRNA.

What is the nucleolus?

A small, rounded, dark structure within the nucleus.

What is the nucleolus mainly composed of?

RNA.

What is the function of the nucleolus?

Ribosome synthesis.

Where are ribosomes transported after synthesis?

Into the cytoplasm.

What is the main function of the plasma membrane?

It forms a selective barrier regulating movement of substances.

Which membrane proteins are involved in transport?

Transport proteins.

Which membrane proteins are involved in cell recognition?

Recognition proteins.

Which membrane proteins are involved in receptor signaling?

Receptor proteins.

What are desmosomes?

Cell junctions that provide strong adhesion between cells.

What are tight junctions?

Cell junctions that seal adjacent cells together.

What is the function of microvilli?

Increase surface area for absorption.

In which cells are microvilli commonly found?

Epithelial cells.

What is receptor-mediated endocytosis?

Uptake of substances through membrane invagination into vesicles.

What are endosomes?

Vesicles that transport substances taken up by endocytosis.

What is the rough endoplasmic reticulum (RER)?

ER studded with ribosomes.

What is the main function of rough ER?

Protein synthesis.

What is the smooth endoplasmic reticulum (SER)?

ER lacking ribosomes.

What is the main function of smooth ER?

Lipid synthesis and membrane production.

What is the function of the Golgi apparatus?

Modification, packaging, and sorting of proteins and lipids.

Why is the Golgi apparatus called the finishing and packaging center?

Because it modifies and packages proteins and lipids into vesicles.

What do lysosomes contain?

Hydrolytic enzymes.

What is the function of lysosomes?

Digestion of phagocytosed material and damaged organelles.

What is autophagy?

Digestion and recycling of damaged cellular components by lysosomes.

What role do lysosomes play in immunity?

They destroy engulfed bacteria.

What do peroxisomes contain?

Oxidative enzymes.

What is the function of peroxisomes?

Oxidation-reduction reactions and detoxification.

What is the main function of mitochondria?

ATP production through oxidative phosphorylation.

Besides ATP production, what is another function of mitochondria?

Regulation of apoptosis through cytochrome c release.

What is the cytoskeleton?

The structural framework providing support, shape, and movement.

What are the functions of microtubules?

Formation of cilia, flagella, centrioles, and intracellular transport.

What proteins make up microfilaments?

Actin and myosin.

What are the functions of microfilaments?

Cell contraction and movement.

What is the function of intermediate filaments?

Structural support and tensile strength.

Which intermediate filament is found in epithelial cells?

Cytokeratin.

Which intermediate filament is found in muscle cells?

Desmin.

Which intermediate filament is found in connective tissue?

Vimentin.

Which intermediate filament is found in neurons?

Neurofilament.

Why are intermediate filaments clinically important?

They serve as immunohistochemical markers for tumour identification.

What is the function of growth in cells?

Increase in cell size and mass.

What is differentiation?

Development into specialized cells.

What is cellular respiration?

ATP generation.

What is reproduction in cells?

Cell division by mitosis or meiosis.

What is phagocytosis?

Engulfment of solid particles.

What is pinocytosis?

Uptake of extracellular fluid.

What is endocytosis?

Uptake of substances into the cell.

What is excretion?

Removal of wastes, metabolites, and toxins.

What is secretion?

Release of substances such as enzymes and hormones.

How do cells recognize other cells?

Through surface receptors.

How do cells adhere to one another?

Through desmosomes and basement membranes.

What structures are responsible for cellular motility?

Cilia, flagella, and cytoskeleton.

What is signal transduction?

Transmission of biochemical or electrical signals within cells.

What are the major forms of cell death?

Apoptosis, necrosis, and autolysis.

What is the cell cycle?

A regulated sequence of events leading to cell division or resting state.

What regulates the cell cycle?

External stimuli and genetic control mechanisms.

Name external factors regulating the cell cycle.

Steroid hormones, growth factors, irradiation, cytotoxic drugs, and trauma.

Name the genetic regulators of the cell cycle.

CDC genes, cyclins, CDKs, and p53.

What are the four phases of the cell cycle?

G1, S, G2, and M phases.

Which phase is mitosis?

M phase.

Approximately how long does M phase last?

About 1 hour.

What occurs during M phase?

Nuclear division and equal distribution of chromosomes.

What DNA content do daughter cells retain after mitosis?

Diploid DNA content.

What is G1 phase?

Gap between mitosis and DNA synthesis.

Approximately how long does G1 phase last?

8–100 hours (variable).

What occurs during G1 phase?

Cell growth and synthesis of enzymes and regulatory proteins.

Which cyclin regulates G1 phase?

Cyclin E.

What regulates Cyclin E activity?

Cyclin-dependent kinases (CDKs).

What occurs during S phase?

DNA replication.

Approximately how long does S phase last?

About 10 hours.

Which cyclin regulates S phase?

Cyclin A.

What occurs during G2 phase?

RNA synthesis, protein synthesis, and DNA repair.

Approximately how long does G2 phase last?

About 5 hours.

What is checked at the G1/S checkpoint?

DNA integrity before replication.

Which protein controls the G1/S checkpoint?

p53.

What is checked at the G2/M checkpoint?

Completion and accuracy of DNA replication.

What are the possible outcomes of the cell cycle?

Mitosis, differentiation, quiescence (G0), and apoptosis.

What is the G0 phase?

Resting phase with no active cell division.

What is apoptosis?

Programmed cell death.

What is the average duration of the cell cycle?

Approximately 24 hours.

Why is the balance between proliferation and apoptosis important?

It maintains normal tissue mass and prevents cancer or atrophy.

What is cell injury?

Damage occurring when adaptive capacity is exceeded by harmful stimuli.

What are the two possible outcomes of cell injury?

Reversible injury or irreversible injury.

What are the two major forms of cell death?

Necrosis and apoptosis.

Name the major causes of cell injury.

Physical agents, chemical agents, biological agents, vascular disturbances, immune reactions, genetic disorders, and nutritional imbalances.

Give examples of physical causes of cell injury.

Trauma, burns, frostbite, UV radiation, and X-rays.