The Cellular Level of Organization - Vocabulary Flashcards

Vocabulary flashcards covering cell membranes, transport, organelles, DNA/RNA biology, protein synthesis, cell cycle, and differentiation.

Cell membrane

A flexible, dynamic barrier that separates the cell’s interior from the exterior and regulates material movement.

Phospholipid bilayer

Two layers of phospholipids forming the core structure of the cell membrane with hydrophilic heads facing water and hydrophobic tails inside.

Amphipathic

A molecule that has both hydrophilic and hydrophobic regions.

Hydrophilic head

The water-attracting part of a phospholipid that faces the aqueous environment.

Hydrophobic tail

The water-repelling fatty acid portion of a phospholipid directed away from water.

Intracellular fluid (cytosol)

Fluid inside the cell.

Extracellular fluid (ECF)

Fluid outside the cell.

Membrane proteins

Proteins associated with the membrane that act as channels, receptors, enzymes, and in cell–cell recognition; can be integral or peripheral.

Transmembrane (integral) proteins

Proteins that span the entire cell membrane and facilitate transport and signaling.

Peripheral proteins

Proteins attached to the interior or exterior surface of the membrane that do not span the membrane.

Glycoprotein

A protein with carbohydrate groups that aid in cell recognition.

Glycocalyx

A carbohydrate-rich coating formed by glycoproteins that helps in cell recognition and binding.

Passive transport

Movement of substances across the membrane that does not require energy and follows a concentration gradient.

Simple diffusion

Movement of small nonpolar molecules directly through the lipid bilayer down their concentration gradient.

Facilitated diffusion

Diffusion of polar or charged molecules through membrane proteins down their concentration gradient.

Osmosis

Movement of water across a semipermeable membrane from areas of lower solute to higher solute concentration.

Isotonic

A solution with equal solute concentration to the cytosol, causing no net water movement.

Hypertonic

A solution with more solute outside the cell, causing water to exit and cell shrink.

Hypotonic

A solution with less solute outside the cell, causing water to enter and potential swelling or bursting.

Tonicity

The osmolarity of the extracellular fluid relative to the cytosol.

Endocytosis

Active transport in which the cell membrane engulfs material to form a vesicle inside the cell.

Exocytosis

Process where vesicles fuse with the cell membrane to release contents outside the cell.

Primary active transport

Active transport that uses ATP directly to move substances against their gradient.

Secondary active transport

Active transport that uses an electrochemical gradient as the energy source.

Symporters

Transporters that move two substances in the same direction across the membrane.

Antiporters

Transporters that move two substances in opposite directions across the membrane.

Sodium-potassium pump

A primary active transport mechanism that pumps 3 Na+ out and 2 K+ in per cycle, using ATP.

Endoplasmic reticulum (ER)

A network of membranous tubules continuous with the nuclear envelope; involved in synthesis and transport of biomolecules.

Rough ER

ER surface studded with ribosomes; involved in protein synthesis.

Smooth ER

ER without ribosomes; involved in lipid synthesis and detoxification.

Golgi apparatus

Flattened sacs that sort, modify, and package proteins for transport; cis-face receives and trans-face ships out.

Lysosome

Membrane-bound vesicles containing digestive enzymes for intracellular breakdown.

Peroxisome

Detoxification and lipid metabolism organelle that contains enzymes including those producing hydrogen peroxide.

Mitochondrion

Organelle known as the energy transformer; site of aerobic respiration and ATP production; has cristae.

Cytoskeleton

Network of protein filaments that provides structure, organization, and transport within the cell.

Microtubule

Cytoskeletal filament made of tubulin; supports structure and facilitates movement.

Intermediate filament

Cytoskeletal filament providing mechanical support; made of keratin.

Microfilament

Actin-based cytoskeletal filament involved in cell shape and movement.

Microvilli

Small projections that increase the surface area of the cell membrane.

Cilia

Hairlike structures that move substances across the cell surface or over the cell surface.

Flagellum

Long projection used for cell locomotion.

Nucleus

Organelle that houses DNA; surrounded by a nuclear envelope with nuclear pores; contains a nucleolus.

Nuclear envelope

Membrane surrounding the nucleus containing nuclear pores for material exchange.

Nuclear pores

Protein-lined channels in the nuclear envelope that regulate movement of molecules into and out of the nucleus.

Nucleolus

Nuclear region involved in ribosome production.

Nucleic acids

DNA, mRNA, tRNA, and rRNA found in human cells; DNA stores the genome; RNA carries genetic information for protein synthesis.

DNA

Deoxyribonucleic acid; the genetic material that stores the genome.

mRNA

Messenger RNA; carries genetic information from DNA to the ribosome for protein synthesis.

tRNA

Transfer RNA; brings amino acids to the ribosome and contains anticodons that pair with mRNA codons.

rRNA

Ribosomal RNA; structural component of ribosomes.

Histone

Protein around which DNA winds to form chromatin.

Chromatin

Looser form of DNA; becomes tightly packed into chromosomes during replication.

Chromosome

Condensed DNA molecule that carries genetic information; formed from chromatids during replication.

Sister chromatid

Identical copy of a chromosome held together at the centromere; separated during mitosis.

Transcription

Process of creating an mRNA strand from a DNA template in the nucleus.

Translation

Process of protein synthesis in the cytoplasm using mRNA, tRNA, and rRNA at the ribosome.

Codon

A three-nucleotide sequence in mRNA that codes for an amino acid.

Anticodon

A three-nucleotide sequence in tRNA that pairs with a specific mRNA codon.

Proteome

The complete set of proteins expressed by a cell or organism.

Ribosome

Ribonucleoprotein complex that carries out protein synthesis; composed of rRNA and proteins.

Initiation (translation)

Ribosome assembles at the start codon to begin polypeptide synthesis.

Elongation (translation)

Amino acids are added one by one to the growing polypeptide chain as tRNAs deliver them.

Termination (translation)

Translation ends when a stop codon is reached, releasing the finished protein.

DNA replication

Process of duplicating the cell’s DNA before cell division.

Helicase

Enzyme that unwinds the DNA double helix to enable replication.

DNA polymerase

Enzyme that synthesizes a new DNA strand by adding nucleotides.

Interphase

Phase of the cell cycle where the cell grows, replicates DNA, and prepares for division.

Mitosis

Nuclear division producing two genetically identical diploid daughter cells; followed by cytokinesis.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells.

Prophase

First mitotic phase; chromatin condenses into chromosomes and spindle apparatus forms.

Metaphase

Mitotic phase where chromosomes align along the cell’s equator.

Anaphase

Mitotic phase where sister chromatids separate and move to opposite poles.

Telophase

Mitotic phase where nuclei reform around separated chromatids; chromosomes de-condense.

Diploid

Cells containing two sets of chromosomes (2n), typically somatic cells with 46 in humans.

Haploid

Cells containing one set of chromosomes (n), typically gametes with 23 in humans.

Growth factors

Signals that stimulate cell growth and division.

Contact inhibition

Prevention of cell division when cells are densely packed and touch each other.

Differentiation

Process by which cells become specialized for a specific function.

Stem cell

An undifferentiated cell with the potential to become various cell types.

Transcription factors

Proteins that turn on specific genes during differentiation.