WEEK 2 - Pre2 Organization of Cells

Vocabulary flashcards covering the key structures, organelles, cytoskeleton components, extracellular structures, cell junctions, and prokaryotic features described in Pre-Lecture 2.

Mitochondria

site of cellular respiration

producing ATP from fuels and oxygen,

enclosed by a double lipid bilayer membrane

containing their own DNA and ribosomes.

Cristae

Infoldings of the inner mitochondrial membrane that separate the matrix from the intermembrane space,

increasing surface area for membrane-bound enzymes to increase the rate of cellular respiration.

Chloroplasts

Specialized plastids surrounded by a double membrane where photosynthesis occurs to produce sugars from $\text{CO}_2$, water, and light, containing their own DNA and ribosomes.

Thylakoids

Flattened, interconnected membrane sacs within chloroplasts where photosynthetic enzymes are located.

Granum

A stack of thylakoids inside a chloroplast.

Stroma

The fluid-filled space outside the thylakoids in a chloroplast containing photosynthetic enzymes, DNA, and ribosomes.

Endosymbiont Theory

The theory that mitochondria and chloroplasts were once free-living prokaryotes that were engulfed by larger ancestral cells and eventually became organelles.

• Mitochondria: Evolved from oxygen-using, nonphotosynthetic bacteria.

• Chloroplasts: Evolved from photosynthetic bacteria.

Peroxisome

An organelle bound by a single lipid bilayer containing enzymes that transfer hydrogen atoms from substrates to oxygen, producing hydrogen peroxide ($\text{H}_2\text{O}_2$) which is converted to water; involved in fatty acid breakdown and detoxification.

Cytoskeleton

A dynamic network of fibers extending throughout the cytoplasm that provides mechanical

support,

structure,

organelle anchorage,

and functions in cell motility.

Microtubules

Hollow rods constructed from dimers of $\text{α}$-tubulin and $\text{β}$-tubulin that possess directionality, maintain cell shape by resisting compression, and serve as tracks for motor protein movement.

Centrosome

Made up of two centrioles. A region located near the nucleus in eukaryotic cells from which microtubules grow.

Centrioles

A single centriole is made up of nine triplets of microtubules arranged in a ring. built out of structural proteins called microtubules and plays a crucial role in cell division and the formation of cellular structures like cilia and flagella.

Flagella and Cilia

Microtubule-containing cellular hair-like, microscopic extensions involved in cell motility, fluid movement across cell surfaces (cilia), and cellular signaling (cilia).

Microfilaments

Twisted double chains of actin subunits ($7 \text{nm}$ diameter) involved in tension bearing, cell shape maintenance, and cell motility such as muscle cell contraction.

Intermediate Filaments

Cytoskeletal fibers ($8\text{--}12 \text{nm}$ diameter) composed of diverse fibrous proteins like keratins coiled together that form permanent structural elements to support cell shape in some eukaryotic cells.

Cell Wall

An extracellular layer made of cellulose microfibrils embedded in polysaccharides and proteins found in plant cells that maintains shape, protection, and water balance.

Middle Lamella

A thin layer rich in pectin located between adjacent plant cell walls that glues adjacent cells together.

Extracellular Matrix (ECM)

An extracellular layer surrounding animal cells composed of glycoproteins such as collagen, polysaccharides, and proteoglycans, functioning in support, cell attachment, and signaling.

Integrins

Cell-surface receptor proteins that sit on the outside of cells and let the cells stick to things around them like other cells or the extracellular matrix. (mainly in animal cells) + signalling

Plasmodesmata

Channels connecting adjacent plant cells that allow direct transfer of compounds between cells.

Gap Junctions

Intercellular channels in animal cells that act as the functional equivalents of plant plasmodesmata.

Tight Junctions

Intercellular connections that form tight seals between adjacent animal cells to prevent leakage of extracellular fluid.

Desmosomes

Anchoring cell junctions that fasten animal cells together into strong sheets, secured by intermediate filaments.

Prokaryotic Cells

Cells lacking a membrane-bound nucleus and endomembrane system, featuring DNA localized in a nucleoid, unique flagella, and a cell wall.

Nucleoid

The non-membrane-bound region in a prokaryotic cell where the bacterial chromosome and DNA are located.

Bacterial Shapes

Morphological forms of prokaryotic cells, specifically classified as spirilla (spiral), bacilli (rod-shaped), or cocci (spherical).