Cell Biology Lecture Notes

These flashcards cover key vocabulary and concepts related to cell structure, function, and signaling as presented in the lecture notes.

Cell

The smallest unit of life that can replicate independently, composed of cytoplasm and a nucleus.

Epithelial cells

Cells that form the layer of tissue covering the body's surfaces and lining its cavities.

Nucleus

The control center of a cell that contains genetic material (DNA) and is responsible for regulating cellular activities.

Phospholipid bilayer

A double layer of phospholipids that makes up the cell membrane, providing structural integrity and selective permeability.

Glycocalyx

A carbohydrate-rich layer that covers the exterior of many cells, involved in cell recognition and adhesion.

Endocytosis

The process by which cells internalize substances by engulfing them in vesicles formed from the plasma membrane.

Phagocytosis

A type of endocytosis also known as 'cell eating,' where cells engulf large particles or microorganisms.

Pinocytosis

A type of endocytosis also known as 'cell drinking,' involving the ingestion of extracellular fluid.

Receptor-mediated endocytosis

A process where cells absorb metabolites and hormones by the binding of ligands to specific receptors on the cell surface.

Exocytosis

The process of vesicle secretion where contents are expelled from the cell into the extracellular space.

Hydrophilic signaling molecules

Molecules that interact with receptors on the cell surface, often leading to signal transduction through second messengers.

Hydrophobic signaling molecules

Molecules like steroid hormones that can pass through the cell membrane and bind to intracellular receptors.

Chromatin

A complex of DNA and proteins that forms chromosomes within the nucleus, existing in active (euchromatin) and inactive (heterochromatin) states.

Nuclear envelope

A double membrane that encloses the nucleus, separating it from the cytoplasm.

Cytoplasm

The gel-like substance inside the cell membrane, excluding the nucleus, containing organelles and cytosol.

Integral proteins

Proteins that are embedded within the phospholipid bilayer of the cell membrane, often spanning the membrane.

Peripheral proteins

Proteins that are loosely attached to the outer or inner surface of the cell membrane.

Fluid mosaic model

A model that describes the cell membrane structure as a mosaic of various components, including phospholipids, proteins, and carbohydrates, in a fluid state.

Signal transduction

The process by which a chemical or physical signal is transmitted through a cell as a series of molecular events.

Lipid bilayer

The fundamental structure of cell membranes, consisting of two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.

Mitochondria

Organelles known as the 'powerhouse of the cell' that generate most of the cell's supply of adenosine triphosphate (ATP) through oxidative phosphorylation.

Ribosomes

Small organelles composed of RNA and proteins that serve as the site of protein synthesis in both prokaryotic and eukaryotic cells.

Rough Endoplasmic Reticulum (RER)

An organelle studded with ribosomes on its surface, primarily involved in the synthesis and folding of proteins for secretion or membrane insertion.

Smooth Endoplasmic Reticulum (SER)

An organelle involved in lipid synthesis, detoxification of chemicals, and calcium ion storage, lacking ribosomes on its surface.

Golgi Apparatus

A series of flattened membrane sacs responsible for modifying, sorting, and packaging proteins and lipids for transport to their final destinations.

Lysosomes

Membrane-bound organelles containing hydrolytic enzymes used to break down macromolecules, old organelles, and foreign substances.

Cytoskeleton

A dynamic network of protein filaments, including microtubules, microfilaments, and intermediate filaments, that provides structural support and enables cell motility.

Peroxisomes

Small organelles that contain enzymes for metabolic reactions, including the breakdown of fatty acids and the detoxification of hydrogen peroxide (H{2}O{2}).

Diffusion

The passive process by which molecules move from an area of higher concentration to an area of lower concentration until they are evenly distributed.

Osmosis

The specific type of diffusion involving the movement of water molecules through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.

Active Transport

The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy in the form of ATP.

Nucleolus

A dense structure within the nucleus where ribosomal RNA (rRNA) is synthesized and the assembly of ribosome subunits begins.

Centrioles

Paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope, playing a key role in organizing microtubules during cell division.

Facilitated Diffusion

The passive movement of molecules across a cell membrane via specific transmembrane integral proteins without the use of energy.

Microtubules

Hollow tubes made of tubulin subunits that are part of the cytoskeleton, providing structural support and acting as tracks for organelle movement.

Microfilaments

Contractile protein filaments made of actin that support cell shape and are involved in cell motility and division.

Intermediate filaments

Fibrous cytoskeletal elements that provide high tensile strength to cells and help stabilize the positions of organelles like the nucleus.

Transcription

The first step of gene expression, where a particular segment of DNA is copied into RNA by the enzyme RNA polymerase.

Translation

The process by which ribosomes synthesize proteins using the genetic code provided by mRNA after the transcription of DNA.

Tight junctions

Impermeable junctions that encircle the cell, preventing molecules from passing through the intercellular space between adjacent cells.

Desmosomes

Strong cell-to-cell adhesion junctions that act like spot welds to resist mechanical stress, common in tissues like the skin.

Gap junctions

Channels between neighboring cells that allow for direct chemical and electrical communication through the passage of ions and small molecules.

Proteasomes

Barrel-shaped protein complexes that degrade damaged or unneeded proteins that have been tagged with ubiquitin.

Plasma Membrane

The semipermeable membrane surrounding the cytoplasm of a cell, composed of a phospholipid bilayer with embedded proteins and signaling molecules.

Cytosol

The liquid component of the cytoplasm, excluding organelles, consisting mainly of water, ions, and soluble proteins where many metabolic reactions occur.

Euchromatin

A loosely packed form of chromatin that contains genes currently being transcribed into RNA.

Heterochromatin

Highly condensed chromatin that is transcriptionally inactive and often found at the periphery of the nucleus.

Cilia

Hair-like projections on the cell surface composed of microtubules that move in a coordinated wave-like manner to transport fluids or mucus.

Flagella

Long, whip-like extensions of the cell membrane containing microtubules that provide motility, such as in human sperm cells.

Vesicles

Small, membrane-enclosed sacs used for storing and transporting substances to and from the cell surface or between organelles.

Mitosis

The phase of the cell cycle during which the nucleus divides into two identical nuclei in preparation for cell division.

Apoptosis

A regulated process of programmed cell death used to remove damaged or redundant cells without eliciting an inflammatory response.

Autophagy

A catabolic process where cells digest their own components, such as damaged organelles, by sequestering them in double-membrane vesicles that fuse with lysosomes.

Ubiquitin

A small regulatory protein that is attached to other proteins to label them for degradation by the proteasome.