bio 215 exam 1

Central Dogma

The fundamental flow of genetic information from DNA to RNA (transcription) and then from RNA to protein (translation).

Prokaryotes

Small, simple cells that lack a nucleus and are divided into two primary domains:

Bacteria and Archaea. Archaea

A domain of prokaryotes often found in extreme environments, such as hot volcanic mud or concentrated brine, that resemble conditions on primitive Earth.

Eukaryotes

Complex cells that contain a distinct nucleus and various membrane-enclosed organelles.

Nucleus

The information store of the eukaryotic cell, enclosed in a double membrane (nuclear envelope), containing the molecules of DNA.

Model Organism

A species studied intensely to understand fundamental cellular processes, such as E. coli for molecular mechanisms or brewer's yeast for eukaryotic biology.

Saccharomyces cerevisiae

A simple eukaryotic model organism (brewer's yeast) used to study essential mechanisms like the cell-division cycle.

Amphipathic

A term describing molecules, such as phospholipids and cholesterol, that possess both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Lipid Bilayer

A two-ply sheet of lipid molecules that forms the basic structure of all cell membranes and serves as a permeability barrier.

Unsaturated

Descriptive of hydrocarbon tails that contain one or more double bonds, creating kinks that interfere with tight packing and increase membrane fluidity.

Cholesterol

A sterol that modulates membrane fluidity in animal cells by filling gaps between phospholipid tails, making the bilayer stiffer and less permeable.

Scramblase

A transporter protein in the ER membrane that randomly redistributes phospholipids between monolayers to ensure symmetric growth of the bilayer.

Flippase

An enzyme in the Golgi membrane that maintains membrane asymmetry by selectively moving specific phospholipids to the cytosolic face.

Transporters

Membrane proteins that move small organic molecules or ions across the bilayer by undergoing a series of conformational changes.

Channels

Membrane proteins that form hydrophilic pores through which specific solutes or ions pass by diffusion.

Active Transport

The movement of a solute against its concentration gradient, a process that requires an input of energy such as ATP hydrolysis.

Electrochemical Gradient

The net driving force for a charged solute, combining the force of its concentration gradient and the membrane potential (voltage).

Osmosis

The movement of water across a membrane from a region of low solute concentration to a region of high solute concentration.

Symport

A gradient-driven pump that moves two different solutes in the same direction across the membrane.

Na+ Pump

An ATP-driven pump in animal cells that expels Na+ and imports K+, maintaining the steep gradients used to power other transport processes.

Mitochondria

Organelles that generate ATP through cellular respiration; they contain their own DNA and likely evolved from engulfed aerobic bacteria.

Chloroplasts

Plant-specific organelles that perform photosynthesis; they are thought to have evolved from engulfed photosynthetic bacteria.

Endoplasmic Reticulum (ER)

An extensive system of membranes where cell membrane components and materials for export are synthesized.

Golgi Apparatus

A stack of flattened sacs that modifies, sorts, and packages molecules received from the ER for secretion or transport.

Lysosomes

Small organelles where intracellular digestion occurs, breaking down unwanted molecules and worn-out organelles.

Signal Sequence

A specific amino acid sequence that acts as a sorting signal, directing a protein to its correct cellular destination.

Endocytosis

The process by which cells import extracellular materials through the invagination of the plasma membrane to form vesicles.

Exocytosis

The process by which intracellular vesicles fuse with the plasma membrane to release contents, such as hormones, into the external medium.