Cells I: Cell Structure and Function

Vocabulary flashcards covering the key terms, membrane structures, transport mechanisms, organelles, and nuclear components outlined in the Cells I lecture notes.

Cell

The basic structural and functional unit of living organisms and the smallest living unit in biology that carries out chemical activities needed to sustain life.

Plasma Membrane

A flexible membrane composed of a phospholipid bilayer with embedded proteins that divides the intracellular and extracellular environments and regulates ion concentrations.

Membrane Potential

A charge difference across the plasma membrane produced by regulation of intracellular and extracellular ion concentrations, where the inside is negatively charged with respect to the outside.

Fluid Mosaic Model

A model describing the plasma membrane as highly flexible and capable of changing its shape and composition through time, rather than being rigid or static.

Phospholipids

Bilayer components of the plasma membrane featuring hydrophilic head groups facing water on the interior and exterior, and hydrophobic tails facing each other on the interior.

Integral Proteins

Transmembrane proteins embedded in the membrane that function as transport channels, receptors for signal transduction, enzymatic sites, and intercellular joinings.

Cholesterol

A plasma membrane component that stabilizes the membrane and whose amount determines membrane fluidity.

Selective Permeability

The characteristic of the plasma membrane that allows small, hydrophobic, non-charged substances to cross more easily than others.

Simple Diffusion

Passive movement of lipid-soluble materials and small molecules down their concentration gradient through membrane pores without requiring energy.

Facilitated Diffusion

Passive movement of molecules like glucose, amino acids, and ions down their concentration gradient using specific transport or carrier proteins without energy expenditure.

Active Transport

Movement of solutes against their concentration gradient (low to high) requiring energy ($\text{ATP}$) and a carrier protein.

$Na^+/K^+$ Exchange Pump

An active transport carrier mechanism that moves solutes against concentration gradients to create electrical potentials across cell membranes.

Endocytosis

Vesicular transport mechanism involved in bulk or large molecule transport into the cell.

Phagocytosis

A type of endocytosis ('cell eating') in which cells like white blood cells engulf invaders or cell debris.

Pinocytosis

A type of endocytosis referred to as 'cell drinking'.

Receptor Mediated Endocytosis

Endocytosis process triggered when surface protein receptors are activated, prompting the membrane to take in specific substances from the outside.

Exocytosis

Vesicular transport mechanism involved in bulk or large molecule transport out of the cell.

Osmosis

Diffusion of water ($H_2O$) across a selectively permeable membrane, moving from a hypotonic solution to a hypertonic solution.

Osmolarity

The total concentration of all solute particles in a solution.

Hypotonic

A solution with a lower solute concentration compared to the human body plasma compartment.

Hypertonic

A solution with a higher solute concentration compared to the human body plasma compartment.

Isotonic

A solution with the same solute concentration compared to the human body plasma compartment.

Cytosol

The jello-like fluid matrix of the cytoplasm surrounding embedded organelles.

Mitochondria

Organelles responsible for $ATP$ synthesis that provide all energy for cellular work and contain a small amount of their own DNA.

Anaerobic Respiration

An energy-releasing pathway (glycolysis) occurring in the cytoplasm that does not require oxygen and yields very little $ATP$.

Aerobic Respiration

An energy-releasing pathway occurring in the mitochondria that requires oxygen and yields a large amount of $ATP$.

Ribosomes

Organelles responsible for protein synthesis, found either free in the cytosol or attached to the endoplasmic reticulum.

Free Ribosomes

Ribosomes suspended in the cytosol that synthesize proteins meant to stay inside the cell.

Attached Ribosomes

Ribosomes bound to the endoplasmic reticulum that synthesize proteins destined for secretion outside the cell.

Smooth Endoplasmic Reticulum

Organelle involved in drug detoxification, lipid and cholesterol production, and steroid hormone production.

Rough Endoplasmic Reticulum

Organelle involved in preparing proteins for transport and secretion, as well as acting as a membrane factory that produces integral membrane proteins and phospholipids.

Golgi Apparatus

Organelle that packages, modifies, and segregates proteins.

Lysosomes

Organelles that serve as sites of intracellular digestion and are filled with hydrolyzing enzymes.

Peroxisomes

Organelles that neutralize dangerous free radicals and detoxify harmful substances such as alcohol and formaldehyde.

Inclusions

Temporary storage structures within the cell for pigments, fat droplets, and other materials.

Cytoskeleton

Small internal rods (microtubules, microfilaments, and intermediate filaments) that determine cell shape, support organelles, and provide machinery for cell transport and division.

Centrioles

Structures located within the centrosome that produce microtubule spindle fibers necessary for cell division and replication.

Cilia

Hair-like cellular projections that beat in only one direction to propel substances across the cell surface.

Flagella

A single tail-like cellular projection used to propel an entire cell forward, such as in a sperm cell.

Microvilli

Finger-like cellular projections that increase surface area for absorption.

Nucleus

The control center for cell activities containing genetic information stored in the chemical form of $DNA$.

Chromatin

Uncoiled $DNA$ present within the cell nucleus.

Chromosomes

Tightly coiled $DNA$ present within the cell nucleus.

Nucleolus

Nuclear structure containing $RNA$ for ribosome assembly.