Cell Biology and Membrane Transport Flashcards

A vocabulary set covering somatic and sex cells, cellular organelles, plasma membrane structure, transport mechanisms, and the processes of gene expression.

Somatic cells

Also called body cells; have $46$ chromosomes, make up most body tissues, and are not passed on to children.

Gametes

Sex cells (sperm and egg) that have $23$ chromosomes, are located in reproductive organs, and are passed on to children.

Diplod ($2N$)

A chromosome number of $46$ total, or $23$ pairs, found in somatic cells.

Haploid ($1N$)

A chromosome number of $23$ total, found in gametes or sex cells.

Plasma membrane

The outer boundary of a cell that allows interaction with the external environment.

Nucleus

A large membrane-bound structure that directs cell activities and contains $DNA$.

Cytoplasm

Material located between the plasma membrane and the nucleus containing organelles.

Organelles

Small specialized structures within a cell that perform specific functions.

Cell metabolism

The process of energy transfer and production of heat within a cell.

Glycocalyx

Combinations of carbohydrates and lipids (glycolipids) and proteins (glycoproteins) on the outer face of the plasma membrane.

Phospholipids

Membrane lipids forming a bilayer with polar (hydrophilic) heads facing the water and nonpolar (hydrophobic) tails facing each other.

Cholesterol

Interspersed among phospholipids in the membrane; its amount determines fluid nature and provides stability.

Integral membrane proteins

Proteins that extend deeply into the membrane, often from one surface to the other, sometimes forming channels.

Peripheral membrane proteins

Proteins attached to integral proteins at either the inner or outer surfaces of the lipid bilayer.

Transport Proteins

Carrier proteins or channels used for movement through the membrane, exhibiting specificity, competition, and saturation.

Channel Proteins

Integral membrane proteins forming tiny tunnels where hydrophobic regions face out and hydrophilic regions line the tunnel.

Leak ion channels

Nongated ion channels that remain always open and are responsible for membrane permeability at rest.

Gated ion channels

Ion channels that are opened or closed by specific stimuli such as ligands or voltage changes.

Ligand-gated ion channels

Channels that open in response to small molecules binding to proteins or glycoproteins.

Voltage-gated ion channels

Channels that open when there is a change in electrical charge across the plasma membrane.

Cystic Fibrosis

A genetic disorder affecting chloride ion channels that results in thick, viscous secretions.

Carrier Proteins

Also called transporters; integral proteins that change shape to move specific molecules across the membrane.

Uniporters

Carrier proteins that move one ion or molecule across the membrane.

Symporters

Carrier proteins that move two ions or molecules in the same direction at the same time (cotransport).

Antiporters

Carrier proteins that move two ions or molecules in opposite directions at the same time (countertransport).

$ATP$-powered pumps

Carrier proteins using energy from the hydrolysis of $ATP$ to $ADP$ to move substances against a gradient.

Receptor Proteins

Proteins or glycoproteins with an exposed receptor site on the outer surface for intercellular communication.

Homeostasis

The stable internal environment maintained by the selectively permeable plasma membrane.

Passive membrane transport

Movement from high to low concentration without the cell expending $ATP$, including diffusion and osmosis.

Active membrane transport

Movement from low to high concentration requiring the use of $ATP$.

Diffusion

Net movement of solutes from an area of high concentration to an area of low concentration in a solution.

Concentration gradient

The difference in concentration between two points.

Osmosis

The diffusion of water (solvent) across a selectively permeable membrane.

Aquaporins

Specific water channel proteins that facilitate osmosis.

Osmotic pressure

The force required to prevent water from moving across a membrane by osmosis.

Isosmotic

Solutions having the same concentrations of solute particles and equal osmotic pressures.

Hyperosmotic

A solution with a greater concentration of solute and higher osmotic pressure.

Hyposmotic

A solution with a lesser concentration of solute and lower osmotic pressure.

Isotonic

A solution in which a cell neither shrinks nor swells.

Hypertonic

A solution causing a cell to shrink (crenation) as water moves out.

Hypotonic

A solution causing a cell to swell and potentially rupture (lysis) as water moves in.

Facilitated diffusion

Carrier-mediated transport moving large or charged molecules down a gradient without $ATP$.

Secondary active transport

Use of potential energy in the concentration gradient of one substance (e.g., $Na^+$) to move another substance (e.g., glucose).

Vesicular transport

Movement of large substances by formation or release of a membrane-bound sac, requiring $ATP$.

Endocytosis

The vesicular transport of materials into the cell.

Phagocytosis

The ingestion of solid particles into large vesicles.

Pinocytosis

The ingestion of dissolved molecules into small vesicles.

Exocytosis

The movement of materials out of the cell via secretory vesicles.

Transcytosis

Movement through a cell combining endocytosis on one side and exocytosis on the other.

Cytosol

The fluid portion of the cytoplasm containing dissolved molecules, ions, and enzymes.

Microtubules

Hollow tubes made of tubulin protein that provide internal scaffold and help in cell division.

Actin filaments

Also called microfilaments; provide structure, support for microvilli, and contractility.

Intermediate filaments

Cytoskeletal components providing mechanical strength, such as in nerve cell extensions.

Nuclear envelope

A double membrane surrounding the nucleus with nuclear pores to regulate movement.

Nucleolus

A dense region within the nucleus where ribosomes are manufactured.

Histones

Proteins associated with $DNA$ to form chromosomes.

Nucleosomes

The structural units of chromosomes.

Chromatin

The dispersed form of chromosomes during much of the cell cycle.

Ribosomes

The sites of protein synthesis, composed of ribosomal $RNA$ ($rRNA$) and proteins.

Endoplasmic reticulum ($ER$)

A membrane network continuous with the nuclear envelope, containing internal spaces called cisternae.

Rough $ER$

Part of the $ER$ with attached ribosomes; site where proteins are produced and modified.

Smooth $ER$

Part of the $ER$ without ribosomes; manufactures lipids, detoxifies, and stores $Ca^{2+}$.

Golgi apparatus

Stacked flattened membrane sacs that modify, package, and distribute proteins and lipids.

Lysosomes

Organelles formed at the Golgi apparatus containing hydrolytic enzymes for digestion and autophagy.

Tay-Sachs Disease

A genetic disorder where lysosomal enzymes cannot break down gangliosides in neurons.

Peroxisomes

Organelles containing enzymes to break down fatty acids and amino acids, producing hydrogen peroxide as a by-product.

Mitochondria

The major site of $ATP$ synthesis, featuring infoldings called cristae and an internal matrix.

Centrioles

Microtubule-forming centers in the centrosome that organize spindle fibers for cell division.

Cilia

Appendages that move materials over the surface of cells, such as mucus in the respiratory tract.

Flagella

Long appendages used for movement by sperm cells.

Microvilli

Extensions of the plasma membrane that increase surface area; supported by actin filaments.

Genes

The functional units of heredity consisting of $DNA$ segments.

Gene expression

The production of $RNA$ or proteins from information stored in $DNA$.

Transcription

The process in the nucleus where $DNA$ is used to produce a complementary $mRNA$ molecule.

Translation

The process in the cytoplasm where the nucleotide sequence of $mRNA$ is used to build a polypeptide chain.

Codon

A sequence of $3$ nucleotides in $mRNA$ that specifies an amino acid.

Anticodon

The part of $tRNA$ that is the complement to an $mRNA$ codon.

Apoptosis

Programmed cell death used to maintain normal cell numbers and remove damaged cells.