Cell Structures and Gene Expression

Comprehensive key vocabulary flashcards on cell transport, eukaryotic organelles, mechanism of action of antibiotics, DNA structure, and gene expression (transcription and translation).

Simple Diffusion

A passive process where small, uncharged molecules such as $O_2$ cross the cell membrane from higher concentration to lower concentration without transport proteins or energy input.

Facilitated Diffusion

The passive transport of large or hydrophilic molecules across a membrane from higher concentration to lower concentration with the assistance of specific transport proteins and without energy input.

Active Transport

The energy-requiring ($ATP$) movement of large or hydrophilic solutes across a cell membrane against their concentration gradient, from lower concentration to higher concentration, using specific transport proteins.

Osmosis

The passive movement of water molecules across a semipermeable cell membrane down its concentration gradient.

Nucleus

A eukaryotic membrane-bound organelle surrounded by a nuclear envelope that encloses DNA and provides instructions for protein production.

Hutchinson-Gilford Progeria Syndrome

A very rare genetic disorder occurring in $1$ in $4\times 10^6$ newborns worldwide that causes rapid early aging.

Ribosomes

Cellular structures that act as protein factories, reading genetic instructions to synthesize proteins in both prokaryotic and eukaryotic cells.

Rough Endoplasmic Reticulum (Rough ER)

A membrane network studded with ribosomes on its surface that participates in protein synthesis and packaging into vesicles.

Smooth Endoplasmic Reticulum (Smooth ER)

A region of the endoplasmic reticulum that lacks ribosomes and is involved in lipid synthesis and detoxification.

Golgi Apparatus

An organelle that receives protein-carrying vesicles from the ER, processes them to complete their structure, and packages them for delivery to specific cellular sites or secretion.

Lysosomes

Cellular compartments containing digestive enzymes processed in the Golgi apparatus that break down food particles and worn-out cell structures.

Peroxisomes

Organelles that break down long-chain fatty acids, synthesize cholesterol and bile acids in the liver, and contain enzymes that allow fireflies to flash.

Zellweger Syndrome

A peroxisomal disease marked by symptoms such as high forehead, hearing impairment, seizures, cataracts, glaucoma, muscle floppiness, and psychomotor retardation.

Centrioles

Structures composed of microtubule triplets arranged in pairs that assist in cellular organization.

Mitochondria

Double-membraned energy-converting organelles whose inner membrane folds, called cristae, produce ATP

Cellular Respiration

The biochemical reaction in mitochondria represented by: $\text{Carbohydrate} + O_2 \rightarrow CO_2 + H_2O + \text{ATP}$.

Prokaryotic Cell

A single-celled organism (typically 1\text{--}4\text{\thinspace}\frac{}{}\text{\textmu}m in size) that lacks membrane-enclosed organelles and has a rigid cell wall surrounding its plasma membrane.

Eukaryotic Cell

A complex cell type (typically 10\text{--}100\text{\thinspace}\frac{}{}\text{\textmu}m in size) that contains a distinct nucleus and specialized membrane-enclosed compartments (organelles).

Penicillin

An antibiotic derived from mold that inhibits bacterial cell wall synthesis, causing water to flow into the bacteria by osmosis until the weakened cell wall ruptures.

Gram-Positive Bacteria

Bacteria containing a thick layer of peptidoglycan in their cell wall that retains Gram stain, causing them to stain purple.

Gram-Negative Bacteria

Bacteria with a cell wall layer of peptidoglycan enclosed by an outer lipid membrane that does not retain Gram stain, causing them to stain pink.

Streptomycin

An antibiotic that disrupts bacterial protein synthesis by selectively binding to prokaryotic ribosomes without affecting human eukaryotic ribosomes.

Chromosomes

Discrete structures in the eukaryotic nucleus made of a single long DNA molecule wrapped around proteins; human cells contain 23 pairs

Gene

A segment of DNA on a chromosome that contains nucleotide instructions to produce at least one specific protein.

Regulatory Sequence

The region of a gene that controls the timing, location, and amount of gene expression.

Coding Sequence

The region of a gene that determines the exact amino acid sequence in a protein.

Allele

An alternative version or nucleotide variation of a specific gene located at a specific locus on a chromosome.

Nucleotides

The building blocks of nucleic acids, consisting of a sugar, a phosphate group, and one of four nitrogenous bases.

Double Helix

The spiral, two-stranded molecular structure of DNA formed by complementary base pairing held together by hydrogen bonds.

Adenine (A)

A nitrogenous base in DNA and RNA that pairs with Thymine in DNA (via two hydrogen bonds) or Uracil in RNA.

Thymine (T)

A nitrogenous base found only in DNA that forms two hydrogen bonds with Adenine.

Guanine (G)

A nitrogenous base present in DNA and RNA that forms three hydrogen bonds with Cytosine.

Cytosine (C)

A nitrogenous base present in DNA and RNA that forms three hydrogen bonds with Guanine.

Uracil (U)

A nitrogenous base found exclusively in RNA that pairs with Adenine, taking the place of Thymine.

Messenger RNA (mRNA)

A single-stranded RNA copy of a gene's coding sequence that carries instructions from the nucleus to the ribosome.

Transfer RNA (tRNA)

An RNA molecule that carries a specific amino acid and uses its anticodon sequence to match complementary mRNA codons during translation.

Ribosomal RNA (rRNA)

The structural and functional RNA component that forms a ribosome.

Transcription

The first step of gene expression where RNA polymerase uses the coding sequence of DNA to synthesize a complementary mRNA molecule.

RNA Polymerase

The primary enzyme in transcription that binds to a gene's regulatory sequence, unzips DNA, and synthesizes a complementary mRNA strand.

Codon

A group of three consecutive mRNA nucleotides that specifies a particular amino acid or translation stop signal.

Anticodon

A three-nucleotide sequence on a tRNA molecule that complementary base-pairs with a specific codon on mRNA.

Translation

The process occurring on ribosomes in the cytoplasm where mRNA sequence instructions are converted into an amino acid chain by tRNAs.

Recombinant Gene

A engineered gene created by joining a regulatory sequence from one host organism (e.g., yeast) with the coding sequence of a protein from a different donor (e.g., spider spidroin).

Transgenic Organism

An organism that carries and expresses recombinant DNA sequence instructions from another species.