Cell Structure and Function Flashcards

A comprehensive set of vocabulary flashcards covering cell theory, biomolecules, membrane dynamics, gene expression, molecular transport, cell signaling, cell-cell interactions, and the cell cycle as described in the Chapter 2 lecture notes.

Robert Hooke

The scientist who discovered plant cells in cork slices and published his observations in Micrographia in $1665$.

Cell Theory

A fundamental biological theory stating that all living organisms are comprised of one or more cells, cells are the fundamental unit of life, and cells originate only from preexisting cells.

Plasma membrane

The outer boundary of the cell that acts as a selectively permeable barrier and is mainly composed of phospholipids and membrane proteins.

Cytoplasm

The intracellular fluid containing organelles that perform specific cellular functions.

Nucleus

A double-membraned structure containing DNA that controls cellular activity through the transcription of DNA.

Nucleic Acids

Biomolecules composed of nucleotides joined by phosphodiester bonds, used to create DNA and various types of RNA.

Adenosine Triphosphate (ATP)

A molecule consisting of adenine, ribose, and three phosphate groups that provides energy when its chemical bonds are broken by hydrolysis.

Proteins

Polymers made of $20$ different amino acids joined by peptide bonds, functioning in catalysis, transport, structure, and regulation.

Acylglycerol

A type of lipid that provides long-term energy storage.

Phospholipid

An amphipathic molecule with a polar hydrophilic head and two nonpolar hydrophobic tails that serves as a structural component of cell membranes.

Cholesterol

A steroid that stabilizes the lipid bilayer, regulates membrane fluidity, and serves as a precursor for steroid hormones.

Carbohydrates

Molecules with an empirical formula of $(CH_2O)_n$ that provide energy storage and serve as identification tags for proteins and lipids.

Glycosidic linkage

The type of covalent bond that joins monosaccharides to form disaccharides and polysaccharides.

Glycosylation

The process of adding carbohydrate groups to proteins or lipids to form glycoproteins or glycolipids for cell identification.

Enzymes

Proteins that act as catalysts to speed up biological reactions by binding to substrates at an active site using a lock-and-key fit.

Transmembrane proteins

Integral membrane proteins that span the lipid bilayer and function as transporters, enzymes, receptors, or identity markers.

Peripheral proteins

Proteins located at the surface of the membrane that associate through reversible interactions with phospholipid heads or anchor via GPI anchors.

Gene expression

The process by which information in DNA is used to make proteins, involving the transcription of DNA into RNA and the translation of RNA into protein.

Nucleosome

The basic unit of DNA packaging in eukaryotes, consisting of negatively charged DNA wrapped around a core of positively charged histone proteins.

Heterochromatin

Tightly coiled DNA that is not transcriptionally active.

Euchromatin

Loosely coiled DNA that is transcriptionally active and open to gene expression.

Transcription

The process in which a segment of DNA is copied into messenger RNA (mRNA) within the nucleus.

Introns

Non-coding intervening sequences in eukaryotic genes that are removed during RNA processing.

Exons

Expressed sequences of a gene that remain in mature mRNA and are translated into protein.

$5'$ cap

A modified GTP molecule added to the $5'$ end of mRNA to prevent degradation.

$3'$ poly-A tail

A sequence of $150-250$ adenine residues added to the $3'$ end of mRNA by poly-A polymerase to increase stability.

Translation

The process occurring at the ribosome where mRNA and tRNA molecules work together to synthesize a protein strand by linking amino acids.

Endomembrane System

A series of membranes throughout the cytoplasm that divide the cell into compartments for modifying, packaging, and transporting proteins and lipids.

Brownian motion

The random movement of molecules that facilitates the transport of substances along concentration gradients.

Simple diffusion

The direct, passive movement of a solute across a semi-permeable membrane from an area of higher concentration to lower concentration.

Osmosis

The passive movement of water across a membrane due to an imbalance in solute concentrations.

Isotonic solution

A solution in which erythrocytes retain their normal, biconcave shape.

Hypertonic solution

A solution that causes water to rush out of the cell, leading erythrocytes to become crenate.

Hypotonic solution

A solution that causes water to move into the cell, potentially leading to swelling and lysis.

Facilitated diffusion

The movement of impermeable solutes across a membrane using transport proteins such as channel or carrier proteins.

Sodium-potassium pump

A carrier protein that uses ATP to perform active transport by moving $3\,Na^+$ out of the cell and $2\,K^+$ into the cell.

Autocrine signaling

A mode of cell signaling where a soluble chemical messenger is secreted by and binds to the same cell.

Paracrine signaling

A mode of cell signaling where a signal is received by a nearby cell within a tissue.

Endocrine signaling

A mode of cell signaling where a signal is received by a distant cell.

Ionotropic receptors

Ligand-gated transmembrane channel proteins that open upon ligand binding to allow the rapid flow of ions across the membrane.

Nuclear receptors

Intracellular proteins that, when activated by lipid-soluble hormones, enter the nucleus to act as transcription factors.

Hemidesmosome

A cell-ECM interaction that attaches the base of a tissue cell to the extracellular matrix using integrins and laminin.

Desmosome

A cell junction that attaches two adjacent cells together using cadherins and intermediate filaments to provide elasticity.

Tight junction

A cell junction composed of occludin molecules that prevents the passage of molecules between adjacent cells.

Gap junction

A cell junction composed of connexin monomers that provides a direct passageway for small molecules between adjacent cells.

Interphase

The longest part of the cell cycle, consisting of $G_1$, S, and $G_2$ phases, during which the cell grows and replicates its DNA.

Anaphase

The shortest phase of mitosis where centromeres split and sister chromatids are pulled toward opposite poles by motor proteins.

Cytokinesis

The final stage of the cell cycle where a ring of actin microfilaments contracts to form a cleavage furrow, pinching two daughter cells apart.

Cell cycle checkpoints

Quality control systems, such as the $G_1/S$ and $G_2/M$ transitions, that stop cell division if DNA damage or replication errors are detected.