Cell Biology Vocabulary Flashcards

Vocabulary practice flashcards covering cell origins, organization, membrane transport, cell division, enzymes, metabolic pathways, and photosynthesis based on the Cell Biology course notes.

Big Bang Theory

The scientific model placing the origin of the Universe between $10$ and $20$\,billion years ago, proposing that all matter existed in a cosmic egg smaller than a hydrogen atom that exploded.

Red Shift

An example of the Doppler effect where light energy emitted by stars or galaxies moving away from Earth is shifted toward longer wavelengths on the red side of the visible spectrum.

Panspermia

The hypothesis that life originated in space and arrived on Earth inside a meteorite, also referred to in revised forms as Cosmic Ancestry.

Miller's Experiment

A $1950$ experiment by Stanley Miller that discharged electric sparks into a simulated primordial atmosphere, yielding organic amino acids from inorganic precursor molecules.

RNA World

A molecular concept proposed by Walter Gilbert suggesting that $\text{RNA}$ was the first nucleic acid hereditary system to form prior to the evolution of $\text{DNA}$.

Autotroph

An organism that synthesizes its own food by capturing energy from inorganic sources through photosynthesis or chemosynthesis.

Heterotroph

An organism that obtains its energy and structural organic molecules by consuming other organisms.

Cell Theory

A foundational biological principle asserting that all living things consist of one or more cells, cellular chemical reactions occur inside cells, all cells arise from pre-existing cells, and cells contain hereditary information.

Fluid-Mosaic Model

A structural model of the cell membrane consisting of a flexible phospholipid bilayer with hydrophilic heads, hydrophobic tails, embedded proteins, and cholesterol.

Endosymbiosis

The theory proposed by Lynn Margulis stating that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by larger host cells in a mutualistic relationship.

Mitochondrion

A double-membrane eukaryotic organelle containing its own $\text{mDNA}$ that serves as the site of cellular energy release and $\text{ATP}$ synthesis via chemiosmosis.

Chloroplast

A double-membrane organelle in plants and algae containing its own $\text{cpDNA}$, thylakoid stacks called grana, and stroma, serving as the site of photosynthesis.

Osmosis

The net diffusion of water molecules across a selectively permeable membrane from an area of higher water potential to an area of lower water potential.

Hypertonic Solution

A solution containing a higher solute concentration (and lower water potential) relative to the cytoplasm of a cell, causing net water movement out of the cell.

Hypotonic Solution

A solution containing a lower solute concentration (and higher water potential) relative to the cytoplasm of a cell, causing net water movement into the cell.

Active Transport

The energy-requiring movement of substances across a cell membrane against their concentration gradient, usually powered by $\text{ATP}$.

Facilitated Diffusion

A passive transport process where specific integral carrier proteins assist solutes across the plasma membrane down their concentration gradient without expending energy.

Binary Fission

The asexual division process in prokaryotes where a single circular chromosome replicates, attaches to the cell membrane, and segregates as the cell splits.

Kinetochore

The protein structure located on the centromere region of a chromosome where spindle apparatus microtubules attach during cell division.

Centromere

The constricted junction region connecting two identical sister chromatids in a replicated eukaryotic chromosome.

Prophase

The initial phase of mitosis during which chromatin condenses into visible chromosomes, the nuclear envelope dissolves, centrioles migrate, and the spindle forms.

Metaphase

The stage of eukaryotic cell division where replicated chromosomes align along the equatorial plane of the spindle apparatus.

Anaphase

The mitotic or meiotic stage characterized by the separation of centromeres or homologous pairs and the movement of chromosomes toward opposite spindle poles.

Telophase

The final stage of nuclear division where separated chromosomes reach the poles, uncoil into diffuse chromatin, and new nuclear envelopes and nucleoli re-form.

Cytokinesis

The division of the cytoplasm following nuclear division, segregating organelles and cellular contents into two distinct daughter cells.

Synapsis

The pairing and physical alignment of replicated homologous chromosomes during Prophase I of meiosis to form a four-strand tetrad.

Crossing-Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during meiotic Prophase I at sites called chiasmata.

Exergonic Reaction

A spontaneous chemical reaction that releases free energy into its environment.

Endergonic Reaction

A non-spontaneous chemical reaction that requires an input of free energy to proceed.

Glycolysis

The universal metabolic pathway occurring in the cytoplasm that breaks down one $6\text{-carbon}$ glucose molecule into two $3\text{-carbon}$ pyruvic acid molecules, producing a net gain of $2$\,$\text{ATP}$ and $2$\,$\text{NADH}$.

Citric Acid Cycle

Also known as the Krebs Cycle; a series of reactions in the mitochondrial matrix that oxidizes acetyl Co-A, producing $\text{CO}_2$, $\text{ATP}$, $\text{GTP}$, $\text{NADH}$, and $\text{FADH}_2$.

Stomata

Microscopic pores in leaf epidermis flanked by two guard cells that regulate the diffusion of $\text{CO}_2$, $\text{O}_2$, and water vapor.

Calvin Cycle

The light-independent pathway of photosynthesis taking place in the chloroplast stroma, where $\text{CO}_2$ is fixed by ribulose bisphosphate (RuBP) to yield glyceraldehyde phosphate (PGAL) and sugar.

C-4 Pathway

A photosynthetic adaptation in warm-climate plants where $\text{CO}_2$ is initially fixed into a $4\text{-carbon}$ oxaloacetate molecule in mesophyll cells before transport to bundle-sheath cells for the Calvin cycle.