An organized assembly of specialized cells and extracellular matrix that forms a distinct part of an animal or plant.
Extracellular matrix (ECM)
A network of polysaccharides and proteins secreted by cells. The ECM surrounds cells, protects cells, and guides their movements. The ECM is a structural component of tissues.
Epidermal cells are tightly packed with many adhesions between cells and between cells. There is little ECM in the epidermal layer.
Basement membrane (also known as the basal lamina)
Composed of ECM. The basement membrane serves to support the epidermis and provide a layer that is impermeable to macromolecules.
tissue layer composed mostly of ECM with scattered cells throughout.
cells that comprise the vast majority of skin epidermis; they are packed with the intermediate filament protein known as keratin.
the “top” surface of an epithelial sheet, it is exposed to air or a bodily fluid.
rests on a basal lamina.
Epithelial stem cells
Dividing cells resting on the basal lamina
skin cells that secrete pigment
tissue cells that combat infection and dispose of dying cells and debris
cells that endocytosis antigen during host defense against microbes
intraepidermal and intradermal lymphocytes
lymphocytes that combat infection
cells that line blood vessels, transfer nutrients and wastes from tissues to blood
cells that secrete extracellular matrix materials and form connective tissue.
cells used for sensory and cognitive functions
A fibrous protein made of extended coiled coils. There are about 30 different types of collagen, which vary in the way that the triple helices are assembled.
long chains of carbohydrate that typically form watery gels.
is a glycosaminoglycan that is abundant in animal ECM. It is formed in places in animals where cells are rapidly dividing. It is also abundant in joints as it has lubricating properties.
ECM proteins with numerous carbohydrate chains.
These are huge molecular complexes of glycosaminoglycan and protein, with molecular weights of several million. Abundant in cartilage, proteoglycans provide strength, resiliency, and pliability.
A protein dimer that binds both to collagen and to the surface of cells. It is a connector protein.
ECM proteins that bind to cell surface receptors and to other ECM molecules. “Paths” of laminin are secreted by cells and used as guides for cellular migration, especially during fetal development.
Proteases that break down ECM proteins. Required for tissue maintenance and renewal.
plasma membrane proteins that couple the cytoskeleton of animal cells to the ECM. Fibronectin receptor, an integrin that binds to fibronectin in the ECM and cytoskeletal proteins intracellularly
A family of integral membrane proteins that allow cells of the same type to bind to one another when calcium is bound. Cadherins usually exhibit homotypic binding, meaning that each kind of cadherin binds to its own type.
A protein-based junction that seals neighboring cells together to prevent leakage of molecules between them
A junction that joins cells via their actin microfilaments. Provides a strong mechanical connection and links the contractile actin network across cells allowing groups of cells to contract in an organized way.
A junction that joins cells via their intermediate cytoskeletal filaments. Provides a very strong mechanical connection. Used in skin and other tough tissues.
Site of cellular attachment to the basement membrane. The attachment links the cellular cytoskeleton to the ECM of the basement membrane.
Aqueous pores composed of the protein connexin between two animal cells. Gap junctions allow small intracellular contents (usually molecules less than 1000 dalton) to pass from one cell to another.
The narrowest cytoskeletal filament, it is
responsible for cellular contraction and expansion
These cytoplasmic structures are centers for microtubule organization during formation of the spindle body
The stacked internal membrane system of a
The internal gel-like matrix of a chloroplast
Large multi-protein assemblies that allow passage of
molecules through the nuclear membrane.
nuclear pore complex
The intermediate cytoskeletal filament in skin
An organelle that acidifies and curls
The name of the reaction that links monomers into polymers such polysaccharides and proteins
Dehydration synthesis or condensation reaction
This class of biomolecule is composed of fatty
acids and glycerol
The type of non-covalent bond that occurs
between polar molecules
A type of non-covalent bond between non-charged, non-polar atoms
Van der Waals force
Long chains of carbohydrates that form watery
Combined secondary structures that form a
functional unit in proteins
Motifs or domains
The enzyme that synthesizes cAMP
Adenylyl cyclase aka adenylate cyclase
This molecule is made by oxidative phosphorylation
This states the first law of thermodynamics
the concept that “energy is conserved”
This states the second law of thermodynamics
the concept that “entropy is increasing”
He defined the energy of chemical bonds
An energy change symbolized by deltaGo
standard free energy change
These proteins lower activation energy
During these reactions, an electron is gained
This parameter must be less than zero for a reaction to procede
free energy change
The state in which the forward and reverse rates of a chemical reaction are thermodynamically equally favorable
Proteins that connect cells to the extracellular matrix and transmit signals based on adhesion
The most abundant protein in animals
Specialized junctions that occur at the apical ends of epithelial cells and prevent diffusion of solutes between cells
Most common cellular junction among keratinocytes
This junction allows the passage of small molecules between cells
The extracellular matrix upon which epithelial sheets
basal lamina (or basement membrane)
Stiffens the lipid bilayer and obliterates the normally sharp transition between gel and liquid states
This enzyme causes phospholipids to switch leaflets
A term that describes the network of cytoskeletal and membrane attached proteins that are just beneath the plasma membrane
The transport of a solute against its electrochemical gradient
A transmembrane protein that is both a channel and an enzyme. It is responsible for returning nerve cell ionic balance to its resting state
A neurotransmitter that acts as a ligand to open chloride channels in nerve cell membranes
The phospholipid that is the source of IP3 and diacyl glycerol (DAG)
Phosphotidyl inositol aka inositol phospholipid
This signal molecule is made by endothelial cells and causes smooth muscle relaxation
NO (Nitric Oxide)
This is the number of times a G-protein-linked signal receptor crosses the membrane
This kinase is activated by cAMP
Protein kinase A
In heart muscle a G-protein coupled receptor binds to acetylcholine and triggers activation of a G protein that opens this
A potassium channel
A monomeric G protein responsible for activation of the MAP kinase cascade
This protein acts as an allosteric activator of several enzymes, but only when bound to calcium
This class of signal receptors forms dimers that trans-autophosphorylate