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50 Cards in this Set

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Plasma Membrane
Membrane made of a double layer of lipids within which proteins are embedded. Serves as an external cell barrier, acts in transport of substances into or out of the cell, maintains a resting potential that is essential for functioning of excitable cells. Dynamic and selectively permeable.
Cell Membrane Proteins
May extend entirely thought the lipid bilayer or protrude on only one face; externally facing proteins associated with sugar groups and may act as receptors and/or contributors to cell-cell recognition
Cytoplasm
Cellular region between the nuclear and plasma membranes consisting of fluid cytosol, organelles, and inclusions.
Mitochondria
Rodlike double-membrane structures with inner membrane folded into projections called cristae. Site of ATP synthesis. "Powerhouse" of the cell.

Occur more densely in cells with higher energy requirements.
Ribosomes
Dense particles consisting of two subunits, each composed of ribosomal RNA and protein. Free or attached to rough ER.

Act as the site of protein synthesis.
Rough Endoplasmic Reticulum
Membrane system enclosing a cavity--the cisterna--and coiling through the cytoplasm.

Proteins are synthesized and bound in vesicles for transport to the Golgi apparatus and other sites. External face synthesizes phospholipids and cholesterol.
Smooth Endoplasmic Reticulum
Membranous system of sacs and tubules, free of ribosomes.

Site of lipid and steroid synthesis, lipid metabolism, and drug detoxification. Catalyzes reactions.
Golgi Apparatus
A stack of smooth membranous sacs and associated vessicles close to the nucleus.

Packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane.
Lysosomes
Membranous sacs containing acid hydrolases.

Sites of intracellular digestion.
Peroxisomes
Membranous sacs of oxidase enzymes.

The enzymes detoxify a number of toxic substances. Catalase breaks down H2O2.
Microtubules
Cylindrical structures made of tubulin proteins. Largest members of the cytoskeleton.

Support the cell and give it shape. Involved in intracellular and cellular movements. Form centrioles.
Cytoskeleton
Fibres that give cells shape and support. Involved in cell movement and acts as transport network within the cell.
Microfilaments
Fine filaments of the contractile protein actin.

Involved in muscle contraction and other types of intracellular movement. Help form the cell's cytoskeleton, cilia, and flagella (if present).
Intermediate Filaments
Intermediate sized protein fibres of varying composition.

Stable cytoskeletal elements that resist mechanical forces acting on the cell. Tough, used to anchor organelles in place. Involved in maintaining shape, desmosomes.
Centrioles
Paired cylindrical bodies, each composed of nine triplets of microtubules.

Organize a microtubule network during mitosis to form the spindle and asters. Form the bases of cilia and flagella.
Nuclear Envelope
Double-membrane structure pierced by pores. Outer membrane continuous with the ER.

Separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus.
Nucleolus
Dense spherical non-membrane-bounded bodies composed of ribosomal RNA and proteins.

Site of ribosome subunit manufacture and assembly.
Chromatin
Granular, threadlike material composed of DNA and histone proteins.

DNA constitutes the genes.
Passive Transport
Transportation of materials across the plasma membrane without the use of ATP.

Includes diffusion (simple and facilitated) and filtration.
Active Transport
Transport of materials across the plasma membrane by using energy from ATP.

Includes primary and secondary active transport, and vesicular transport (exocytosis/endocytosis--phagocytosis and pinocytosis) (pumping and bulk transport)
Simple Diffusion
Net movement of particles from an area of higher concentration to an area of lower concentration (along the concentration gradient).

Utilizes kinetic energy.
Facilitated Diffusion
Net movement of particles along their concentration gradient carried out by attaching the substance to a lipid-soluble membrane carrier protein or by moving through a membrane channel.

Utilizes kinetic energy.
Osmosis
Simple diffusion of water through a selectively permeable membrane.

Utilizes kinetic energy.
Filtration
Movement of water and solutes through a semipermeable membrane from a region of higher hydrostatic pressure to a region of lower hydrostatic pressure--along a pressure gradient.

Utilizes hydrostatic pressure.
Primary Active Transport
Transport of substances (mostly ions) against a concentration or electrochemical gradient across the plasma membrane. Utilizes a solute pump.

Directly uses energy of ATP hydrolysis.
Secondary Active Transport
Cotransport of two solutes (polar or charged) across a membrane. Energy supplied by the ion gradient created by a primary active solute pump (indirectly). Symport and antiport.

Energy from ATP.
Exocytosis
Secretion or ejection of substances from a cell. The substance is enclosed in a membranous vesicle, which fuses with the plasma membrane and ruptures, releasing the substance to the exterior.

Utilizes energy from ATP.
Endocytosis
Intake of substances into the cell via vesicles. Phagocytosis and pinocytosis.
Phagocytosis
"Cell eating." A large external particle is surrounded by a pseudopod and becomes enclosed in a clathrin-coated vesicle.

Utilizes energy from ATP.
Pinocytosis
"Cell drinking." Plasma membrane sinks beneath an external fluid droplet containing small solutes. Membrane edges fuse, forming a fluid-filled vesicle.

Utilizes energy from ATP.
Fluid Mosaic Model
Depicts the plasma membrane as a thin structure composed of a bilayer of lipid molecules with protein molecules dispersed in it. The bilayer consists of phospholipid, cholesterol, and glycolipids.
Glycolipids
Phospholipids with attached sugar groups found on the outer plasma membrane surface.
Cholesterol
Platelike hydrocarbon rings which stabilize the lipid membrane by wedging themselves between the phospholipid tails and restraining movement of the phospholipids.
Integral Proteins
Proteins firmly inserted into the lipid bilayer. Most are transmembrane.
Transmembrane proteins
Integral proteins that span the entire width of the membrane and protrude on both sides. Mainly involved in transport as channels or carriers. Some act as receptors for hormones or other chemical messengers.
Peripheral Proteins
Proteins attached loosely to integral proteins or membrane lipids. Include a network of filaments that helps support the membrane from its cytoplasmic side.
Glycoprotein
Protein with associated sugars.
Glycolipid
Lipid with associated sugars
Glycocalyx
Branching carbohydrate-rich area at the cell surface which provides highly specific biological markers by which approaching cells recognize one another.
Microvilli
Fingerlike extensions of the plasma membrane that increase its surface area and are most often found on the surface of absorptive cells.
Membrane Junctions
Glycoproteins in the glycocalyx act as an adhesive.

Wavy contours of the membranes of adjacent cells fit together tongue-and-groove fashion.

Special membrane junctions: tight, gap, and desmosomes.
Tight Junction
Series of integral protein molecules in the plasma membranes of adjacent cells fuse together to from an impermeable junction that encircles the cell.

Found in digestive tract, epithelium, etc.
Desmosomes
Anchoring junctions. Mechanical couplings scattered along the sides of abutting cells that prevent their separation.Plaque on inner surface with thin linker protein filaments that extend and interdigitate in the intercellular space. Adjacent cells are held together by thin linker protein filaments.

Found in epithelium, heart, etc.
Receptor
Point on a protein where molecules can bind.
Gap Junction
A communicating junction that allows chemical substances to pass between adjacent cells. Adjacent plasma membranes are very close and the cells are connected by connexons (made of transmembrane proteins).

Present in electrically excitable tissues (such as heart and smooth muscle) where ion passage from cell to cell helps synchronize electrical activity and contraction.
Osmolarity
The total concentration of all solute particles in a solution.
Hypotonic
Lower concentration of solute in solution. The solution will lose water or take up more solute.

Cells in hypotonic solution take in water, swelling or even lysing.
Hypertonic
Solution contains a higher concentration of solute. It will take up water or lose solute.

Cells in hypertonic solution lose water and crenate.
Anucleate
Having no nucleus.

RBC's, for example, eject their nuclei.
Multinucleate
Having many nuclei.

For example, skeletal muscle cells are often fused cells containing several nuclei.