M1 – L3: Microscopy of Cell Structure – VOCABULARY Flashcards

Vocabulary flashcards covering key concepts, structures, and terms related to cell structure, organelles, cytoskeleton, membranes, and transport as described in the lecture notes.

Eukaryotic cell

Cell with a membrane-bound nucleus and membrane-bound organelles; humans are composed of eukaryotic cells.

Prokaryotic cell

Smaller, simpler cells lacking a membrane-bound nucleus and organelles; bacteria.

Cytoplasm

Material inside the cell excluding the nucleus, including cytosol and organelles.

Cytosol

The intracellular fluid, mainly water with dissolved solutes.

Cytoplasmic inclusions

Stored substances within the cytoplasm that are not membrane-bound (e.g., lipid droplets, glycogen granules).

Lipid droplets

Intracellular fat storage inclusions; appear as pale spheres in TEM.

Glycogen granules

Stored carbohydrate granules in the cytoplasm; appear as dark grains in TEM and cluster together.

Pigmented deposits

Naturally colored substances deposited in cells.

Melanin

Pigment that protects skin cells from UV light.

Lipofuscin

Brownish pigment found in aging cells (e.g., older neurons); accumulates with age.

Organelles

Membrane-bound structures within a cell that perform specific functions.

Plasma membrane

Dynamic, selective boundary of the cell composed of lipids and proteins; about 5–10 nm thick.

Glycocalyx

Layer of carbohydrate chains on the cell surface; involved in cell recognition and adhesion.

Glycoproteins

Carbohydrates attached to proteins in the plasma membrane.

Glycolipids

Carbohydrates attached directly to membrane lipids.

Vesicles

Membrane-bound sacs that transport substances within or outside the cell.

Endocytosis

Process by which substances enter the cell via vesicle formation.

Pinocytosis

Non-specific uptake of extracellular fluid through endocytosis.

Receptor-mediated endocytosis

Specific uptake triggered by ligand binding to cell receptors.

Phagocytosis

Ingestion of large particles by phagocytes, often using pseudopodia.

Pseudopodia

Temporary cellular projections used to engulf particles during phagocytosis.

Exocytosis

Vesicles fuse with the plasma membrane to release contents outside the cell.

Simple diffusion

Movement of molecules across the membrane without transport proteins.

Facilitated diffusion

Movement down a concentration gradient via carrier proteins.

Osmosis

Diffusion of water across a semipermeable membrane.

Active transport

Movement of substances against their gradient requiring energy.

Fluid mosaic model

Plasma membrane model describing a fluid phospholipid bilayer with embedded and peripheral proteins.

Integral proteins

Proteins embedded within the phospholipid bilayer.

Peripheral proteins

Proteins associated with the membrane surface, not embedded in the bilayer.

Microvilli

Finger-like projections that increase surface area for absorption.

Cytoskeleton

Network of protein filaments that supports, stabilizes, and moves the cell.

Microfilaments (Actin)

Thinnest cytoskeletal filaments (~5–7 nm) composed of actin; enable movement and support microvilli.

Intermediate filaments

Cytoskeletal filaments (~10–12 nm) providing structural support; keratin in epithelia, neurofilaments in neurons.

Microtubules

Large cytoskeletal filaments (~25 nm) of tubulin; form centrioles, mitotic spindle, cilia, and flagella; enable vesicular transport.

Centrosome

Microtubule organizing center (MTOC) consisting of a pair of centrioles and pericentriolar matrix.

Centrioles

Triplet microtubule structures arranged in a 9x3 pattern; paired perpendicularly in the centrosome.

Pericentriolar matrix

Protein-rich region around centrioles that nucleates microtubules.

Ribosomes

Ribonucleoprotein particles (~20–30 nm) that synthesize proteins; can be free or attached to RER; composed of large and small subunits.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; synthesizes proteins; continuous with the outer nuclear membrane.

Prominent in cells that produce protein and lysosomes

rER

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; synthesizes lipids, metabolizes drugs, and stores calcium.

Golgi apparatus

Stack of flattened cisternae; modifies, sorts, and ships proteins; has cis (receiving) and trans (shipping) faces.

cis face

Forming/receiving face of the Golgi, facing the RER.

trans face

Maturing/shipping face of the Golgi, facing the plasma membrane.

cisterna

Flattened sacs within the Golgi apparatus.

Lysosomes

Digestive organelles produced by the Golgi; acidic pH and enzymes; digest endocytosed material; autophagy and autolysis.

Autophagy

Degradation and recycling of old or nonfunctional cellular components.

Autolysis

Self-digestion and breakdown of the cell at death.

Peroxisomes

Small organelles (microbodies) that break down toxins; abundant in liver; originate from the ER; contain enzymes.

Difference in TEM between peroxides and lysosomes

Peroxisomes have a central aggregate of enzymes that appear as a small dark accumulation

Mitochondria

Organelles generating ATP; contain own DNA; double membrane with inner membrane folds (cristae). Activate apoptosis, self replicate

Cristae

Folded inner mitochondrial membrane increasing surface area for ATP production.

Outer mitochondrial membrane

Permeable to ions and small metabolites. Between cytoskeleton and outer compartment of mitochondria

Inner mitochondrial membrane

Layer between outer compartment and matrix - arranged into Cristal - proteins for production of ATP

Matrix

The innermost compartment of the mitochondrion, located inside the inner membrane.

Nucleus

Large organelle containing DNA and a nucleolus; double membrane; controls cellular activities. Will stain basophlic with H&E

Nuclear envelope

Double membrane surrounding the nucleus; outer membrane continuous with RER; inner membrane lines nucleus; contains nuclear lamina.

Nuclear pores

Gated openings in the nuclear envelope that regulate transport between nucleus and cytosol.

Chromatin

DNA-protein complex that condenses into chromosomes during division; exists as euchromatin or heterochromatin.

Euchromatin

Loosely coiled, gene-rich, transcriptionally active chromatin; lighter staining.

Heterochromatin

Densely packed, gene-poor, transcriptionally inactive chromatin; darker staining.

Pyknotic

Condensed, dark-staining nuclei indicating reduced cellular activity or death.

Marginal heterochromatin

Heterochromatin located at the periphery of the nucleus.

Nucleolar-associated chromatin

Heterochromatin surrounding the nucleolus.

Chromosomes

Condensed chromatin visible during cell division, often appearing X-shaped.

Nucleolus

Nuclear substructure that assembles ribosomal subunits; lacks a membrane; very dark in TEM; basophilic in LM.

Nucleolus function

Synthesis and assembly of ribosomal subunits.