Cellular Structure, Proteins, and Metabolic Pathways

Vocabulary flashcards generated from lecture notes covering cellular components, membrane junctions, organelle functions, protein binding, and metabolic pathways.

Cytosol

The fluid portion of the cytoplasm surrounding the cell organelles.

Cytoplasm

The complete cellular region outside the nucleus, comprising both the cytosol and cell organelles.

Plasma Membrane

A major structural element that acts as a selective barrier, detects chemical messengers, links adjacent cells, and anchors cells to the extracellular matrix.

Phospholipid Bilayer

The core membrane structure consisting of nonpolar fatty acid chains in the interior and polar regions oriented toward the membrane surfaces.

Cholesterol

A lipid component of the plasma membrane that functions to maintain membrane fluidity.

Integral Membrane Proteins

Amphipathic membrane proteins that associate with fatty acid chains in the membrane and can span the entire membrane as transmembrane proteins.

Peripheral Membrane Proteins

Membrane proteins that do not associate with fatty acids and are located at the membrane surface bound to integral membrane proteins.

Fluid-Mosaic Model

A model describing the plasma membrane structure as a flexible phospholipid bilayer embedded with cholesterol and dynamic proteins.

Integrins

Transmembrane proteins that bind to specific proteins in the extracellular matrix and link to membrane proteins in adjacent cells.

Desmosomes

Cell junctions where plasma membranes are separated by about $20\,\text{nm}$, using dense plaques and cadherins to anchor adjacent cells together.

Cadherins

Proteins extending from dense plaques into the extracellular space to link with cadherins of an adjacent cell.

Tight Junctions

Cell junctions that leave no space between adjacent cells, forming a continuous barrier around the cell circumference to block movement of material through tissue.

Gap Junctions

Protein junctions consisting of joined connexins that create $1.5\,\text{nm}$ diameter channels connecting the cytosols of adjacent cells.

Connexins

Membrane proteins from adjacent cells that join together to form the protein-lined channels of gap junctions.

Chromatin

The complex of nuclear DNA bound to proteins called histones.

Chromosomes

Densely condensed forms of chromatin that become visible during cell division.

Nuclear Envelope

A double-membrane structure surrounding the nucleus that contains nuclear pores formed where the inner and outer membranes join.

Nucleolus

A nuclear structure associated with DNA regions containing ribosomal RNA genes, serving as the site where ribosomes are assembled.

Ribosomes

Protein factories composed of protein and RNA that can be bound to the endoplasmic reticulum or free in the cytoplasm.

Rough Endoplasmic Reticulum

An organelle studded with ribosomes on its surface that packages newly synthesized proteins and sends them to the Golgi apparatus.

Smooth Endoplasmic Reticulum

A ribosome-free organelle involved in lipid synthesis, cellular detoxification, and calcium storage.

Golgi Apparatus

An organelle that receives proteins from the rough ER, modifies and sorts them into transport vesicles, and routes them to their intended destinations.

Cristae

The inner membrane foldings of a mitochondrion.

Matrix

The innermost compartment enclosed by the inner mitochondrial membrane.

Lysosomes

Acidic organelles containing digestive enzymes that degrade bacteria, cellular debris, and old or damaged organelles.

Peroxisomes

Organelles that consume oxygen to remove hydrogen from organic molecules, break down lipids into 2-carbon fragments, and generate $\text{H}_2\text{O}_2$.

Actin Filaments

Cytoskeletal microfilaments with a $7\,\text{nm}$ diameter composed of G-actin subunits that participate in cell movement, shape, division, and muscle contraction.

Intermediate Filaments

Cytoskeletal filaments with a $10\,\text{nm}$ diameter made of proteins like keratin, desmin, or lamin that anchor the nucleus and provide mechanical strength.

Microtubules

Cytoskeletal structures with a $25\,\text{nm}$ diameter made of tubulin subunits that radiate from the centrosome and act as tracks for organelle movement.

Centrosome

A region surrounding two centrioles that regulates the formation and assembly of microtubules.

Cilia

Hair-like motile surface extensions on certain epithelial cells containing a central core of microtubules arranged in a 9 + 2 pattern.

Gene

A specific sequence of DNA containing information that specifies the amino acid sequence of a polypeptide chain.

Triplet Code

The arrangement of 4 nucleotide bases into 64 distinct three-letter combinations (codons) used to specify amino acids.

Ligand

Any molecule or ion that non-covalently binds to a specific site on a protein.

Binding Site

The region on a protein where a ligand attaches.

Chemical Specificity

The ability of a protein's binding site to selectively bind specific ligands based on complementary structural shape.

Affinity

The strength of binding between a ligand and a protein, which determines how easily the ligand detaches from the binding site.

Enzymes

Protein catalysts that accelerate biological reactions by lowering their activation energy.

Substrates

Reactant molecules that specifically bind to an enzyme during a chemical reaction.

Glycolysis

A cytoplasmic metabolic pathway that breaks down 1 glucose molecule into 2 pyruvate molecules, yielding a net total of 2 ATP and reducing $\text{NAD}^+$ to NADH.

Krebs Cycle

A mitochondrial pathway that oxidizes Acetyl CoA, producing $\text{CO}_2$ as waste while reducing $\text{NAD}^+$ to NADH and FAD to $\text{FADH}_2$.

Oxidative Phosphorylation

The process in which high-energy electrons pass through cytochrome proteins in the electron transport chain to $\text{O}_2$, generating ATP and $\text{H}_2\text{O}$.