Biology Lecture Notes: Cells, Tissues, and Cell Biology Concepts

Vocabulary flashcards covering core terms from cells, tissues, organelles, and cell biology concepts. Each card presents a term and its concise definition.

Cell

The smallest living unit of structure and function in organisms; all living things are composed of cells; new cells arise from pre-existing cells.

Prokaryotes

Cells that lack a nucleus and membrane-bound organelles.

Archaea

A domain of prokaryotic organisms distinct from bacteria, often extremophiles.

Bacteria

A domain of prokaryotic organisms; one of the major groups of single-celled organisms.

Eukaryotes

Cells with a true nucleus and membrane-bound organelles.

Fungi

A eukaryotic kingdom; usually with chitin-containing cell walls and absorptive nutrition.

Animals

Multicellular eukaryotes that lack cell walls and ingest food.

Protists

A diverse group of mostly single-celled eukaryotes.

Plants

Multicellular, photosynthetic eukaryotes with cellulose cell walls.

DNA (no nucleus)

Genetic material located in the cytoplasm of prokaryotic cells; not enclosed in a nucleus.

DNA (in nucleus)

Genetic material located within a cell’s nucleus in eukaryotes.

Membrane-bound organelles

Organelles like the nucleus, mitochondria, ER, and Golgi that are enclosed by membranes in eukaryotic cells.

No membrane-bound organelles

Characteristic of prokaryotic cells lacking membrane-bound compartments.

Cytoplasm

The jelly-like substance inside the cell that surrounds organelles.

Ribosomes

Small RNA-protein particles that synthesize proteins.

Nucleus

The cell’s headquarters that houses DNA and the nucleolus.

Nucleolus

A region inside the nucleus that synthesizes ribosomal RNA (rRNA).

Endoplasmic Reticulum (ER)

A membranous network involved in processing and transport of proteins and lipids.

Rough Endoplasmic Reticulum (RER)

ER with ribosomes; synthesizes and modifies proteins.

Smooth Endoplasmic Reticulum (SER)

ER lacking ribosomes; lipid synthesis and detoxification.

Golgi apparatus

Sorting, modifying, and shipping of proteins and lipids from the ER.

Mitochondria

Powerhouse of the cell; produces ATP via cellular respiration.

Cellular respiration

Process that converts glucose and oxygen into ATP, CO2, and water.

ATP

Adenosine triphosphate; the cell’s main energy currency.

Central vacuole

Large storage organelle in plant cells that helps maintain turgor pressure.

Cell wall

Rigid layer outside the plasma membrane in plants and some organisms; mainly cellulose in plants.

Nervous tissue

Tissue for control and communication; transmits electrical impulses.

Neurons

Primary signaling cells of the nervous system that transmit impulses.

Glial cells

Supportive cells in the nervous system that provide support and protection.

Skeletal muscle

Voluntary muscle attached to bones; responsible for movement and posture.

Cardiac muscle

Involuntary, striated muscle of the heart with intercalated discs.

Smooth muscle

Involuntary muscle in the walls of hollow organs and vessels; non-striated.

Striations

Visible bands in skeletal and cardiac muscle due to organized filaments.

Multinucleate

Cells containing more than one nucleus (e.g., many skeletal muscle fibers).

Uninucleate

Cells with a single nucleus.

Intercalated discs

Specialized connections between cardiac muscle cells that coordinate contraction.

Tendon

Connective tissue that attaches muscle to bone.

Phosphorylation

Addition of a phosphate group to a molecule, often altering protein activity.

Homeostasis

Maintenance of a stable internal environment.

Flow

Movement of a substance or molecule through pathways or compartments.

Protein synthesis

Process of building proteins from genetic information.

Transcription

Synthesis of messenger RNA (mRNA) from a DNA template.

Translation

Synthesis of a protein from mRNA at the ribosome.

mRNA

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

tRNA

Transfer RNA; carries amino acids to the ribosome during protein synthesis.

Ribosomal RNA (rRNA)

RNA component of ribosomes that helps catalyze protein synthesis.

Initiation (transcription)

RNA polymerase binds DNA and begins RNA synthesis.

Elongation (transcription)

RNA polymerase adds nucleotides to the growing mRNA strand.

Termination (transcription)

RNA polymerase reaches end of gene; mRNA transcript is released.

Genome

The complete set of genetic material of an organism.

Nucleosome

DNA wrapped around histone proteins forming a core particle.

Chromatin

Loosely organized DNA-protein complex in the nucleus.

Chromosomes

Condensed DNA-protein structures that carry genes.

Base pairing (A-T, C-G)

DNA rule: adenine pairs with thymine; cytosine pairs with guanine.

Transcription factors

Proteins that bind DNA to regulate gene expression.

Somatic cell

Body cell; diploid; not a gamete.

Germ cell

Reproductive cell that gives rise to gametes; haploid.

Diploid

Two complete sets of chromosomes.

Haploid

One complete set of chromosomes.

Cell cycle

Orderly sequence of stages through which a cell grows and divides.

DNA replication

Copying of DNA prior to cell division.

Growth factors

Signals that promote cell growth and division.

Contact inhibition

Process by which cells stop dividing when they contact neighbors.

Checkpoints

Control points in the cell cycle that verify if conditions are right to proceed.

HeLa cells

Cell line derived from Henrietta Lacks; widely used in research.

Cellular differentiation

Process by which unspecialized cells become specialized.

Stem cells

Undifferentiated cells capable of renewing themselves and differentiating.

Transcription factors (again)

Proteins that regulate gene expression by binding DNA.

Epithelial tissue

Tissue that covers surfaces and lines cavities, and forms glands.

Connective tissue

Tissue that binds, supports, and protects other tissues and organs.

Muscle tissue

Tissue that produces movement.

Nervous tissue

Tissue for rapid communication; contains neurons and glia.

Extracellular matrix (ECM)

Network of proteins and carbohydrates surrounding cells; provides support.

Collagen

The most abundant structural protein in the body; forms sturdy ECM fibers.

Proteoglycan

Large negatively charged molecules in ECM that attract water and ions.

Tight junction

Junction that seals cells together to prevent leakage.

Gap junction

Channels that allow direct communication between neighboring cells.

Desmosome

Anchoring junction that provides strong adhesion between cells.

Microvilli

Small projections that increase surface area for absorption.

Cilia

Hairlike organelles that move fluids across cell surfaces.

Flagellum

Long, whip-like structure enabling cell movement.

Glycocalyx

Carbohydrate-rich coating on the cell surface formed by glycoproteins and glycolipids.

Glycoprotein

Protein with carbohydrate attached; part of glycocalyx.

Glycolipid

Lipid with carbohydrate attached; part of glycocalyx.

Phospholipid bilayer

Two-layer arrangement of phospholipids forming the cell membrane.

Hydrophilic (pole and head)

Water-loving; polar phosphate head of phospholipids.

Hydrophobic

Water-repelling; nonpolar fatty acid tails of phospholipids.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Intracellular fluid (ICF)

Fluid inside cells.

Extracellular fluid (ECF)

Fluid outside cells; includes interstitial fluid and plasma.

Interstitial fluid (IF)

ECF not contained within blood vessels.

Plasma

ECF contained within blood vessels.

Transmembrane protein

Proteins that span the entire cell membrane, enabling transport and signaling.

Receptors

Transmembrane proteins that bind ligands and trigger cellular responses.

Ligand

Molecule that binds to a receptor to initiate a response.

Glycoprotein/Glycolipid (in glycocalyx)

Carbohydrate-bearing proteins/lipids forming the cell surface coat.

Peripheral proteins

Proteins associated with the inner or outer surface of the membrane, not spanning it.

Diffusion

Movement of molecules from high to low concentration without energy.

Osmosis

Diffusion of water across a semipermeable membrane.

Isotonic

Solution with the same solute concentration as the cell interior; no net water movement.