Human A&P I

Structural unit of all living things

Robert Hooke in the late 1600s with a crude microscope

Two German scientists, Matthias Schleiden and Theodor Schwann.

• 1. A cell is the basic structural and functional unit of living organisms. When you define cell properties, you define the properties of life.
• 2. The activity of an orgamism depends on both the individual and the collective activities of its cells.
• 3. According to the principle of complentarity of structure and function, the biochemical activities of cells are dictated by their shapes or forms, and by the relative number of their specific subcellular structures.
• 4. Continuity of life from one generation to another has a cellular basis.

• 1. The plasma membrane - the outer boundary of the cell.
• 2. The cytoplasm - the intracellular fluid packed with organelles, small structures that perform specific cell functions.
• 3. The nucleus - an organelle that controls cellular activities. Typically, the nucleus lies near the cell's center.

Membrane, composed of phospholipids, cholesterol, and proteins, that encloses cell contents; outer limiting cell membrane.

A depiction of the membranes of a cell as phospholipid bilayers in which proteins are dispersed.

Lipid bilayer. It is constructed largely of phospholipids, with smaller amounts of glycolipids, cholesterol, and areas called lipid rafts.

Water loving

Water fearing

Lipids with attached sugar groups. Found only on the outer plasma membrane surface, glycolipids account for approximately 5% of total lipids.

With a polar and non-polar region, it wedges its platelike hydrocarbon rings between the phospholipid tails, stabilizing the membrane and decreasing the mobility of the phospholipids and the fluidity of the membrane. Accounts for approximately 20% of the membrane lipid.

Make up about half of the plasma membrane by mass and are responsible for most of the specialized membrane functions.

Proteins firmly inserted into the lipid bilayer. Some protrude from one side only, but most are transmembrane proteins that span the entire membrane and protrude on both sides.

A process in which transmembrane proteins are receptors for hormones or other chemical messengers and relay messages to the interior of the cell.

Not imbedded in the lipid bilayer, but are loosely attached to the integral proteins. Includes a network of filaments which help support the membrane from its cytoplasmic side.

Dynamic assemblies of saturated phospholipids that makes up approximately 20% of the outer membrane surface.

• A layer of externally facing glycoproteins on a cell's plasma membrane; its components determine blood type and are involved in the cellular interactions of fertilization, embryonic development, and immunity, and act as an adhesive between cells.
• (Fuzzy, sticky carbohydrate rich area at the cell surface)

• 1. Glycoproteins in the glycocalyx act as an adhesive.
• 2. Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion.
• 3. Special cell junctions form.

Area where plasma membranes of adjacent cells are tightly bound together, forming an impermeable barrier. (Impermeable Junction)

Cell junction composed of thickened plasma membranes joined by filaments. (Anchoring Junctions)

A passageway between two adjacent cells; formed by transmembrane proteins called connexons.

Fluid between the cells, derived from the blood. Contains thousands of ingredients, including amino acids, sugars, fatty acids, vitamins, regulatory substances such as hormones and nuerotransmitters, salts, and waste products.

The property of membranes that permits passage of molecules and ions.

Allows some substances to pass the plasma membrane while preventing others from passing.

Membrane transport processes that not require cellular energy (ATP), such as diffusion, which is driven by kinetic energy.

The cell provides the metabolic energy (usually ATP) needed to move substances across the membrane.

• Diffusion
• Filtration

The spreading of particles in a gas or solution with a movement toward uniform distribution of particles, driven by kinetic energy.

The difference in concentration of a particular substance between two different areas.

The driving force for diffusion is the kinetic energy of the molecules themselves. Therefore the speed of diffusion is affected by molecular size (the smaller, the faster) and temperature (the warmer, the faster).

• 1. If the molecule is lipid soluble
• 2. If the molecule is small enough to pass through the membrane channels
• 3. If the molecule is assisted by a carrier molecule

The unassisted transport across a plasma membrane of a lipid-soluble or very small particle. Some examples include oxygen, carbon dioxide, and fat-soluble vitamins.

Passive transport process used by certain large or charged molecules (such as glucose, Na1) that are unable to pass through the plasma membrane unaided. Involves movement through channels or movement facilitated by a membrane carrier. (Includes glucose and other sugars, some amino acids, and ions)

A transmembrane protein that changes shape to envelop and transport a polar substance across the cell membrane.

A transmembrane protein that forms an aqueous pore, allowing substances to move from one side of the membrane to the other.

Always open and simply allow ions or water to move according to concentration gradients.

Controlled by chemical or electrical signals.

Diffusion of a solvent through a membrane from a dilute solution into a more concentrated one.

Transmembrane proteins that form water channels.

The number of solute particles present in 1 liter of a solution.

Pressure of fluid in a system.

A measure of the tendency of water to move in a more concentrated solution.

A measure of the ability of a solution to cause a change in cell shape or tone by promoting osmotic flows of water.

A solution with a concentration of nonpenetrating solutes equal to that found in the reference cell.

A solution that has a higher concentration of nonpenetrating solutes than the reference cell; having greater osmotic pressure than the reference solution (blood plasma, or interstitial fluid).

A solution that is more dilute (containing fewer nonpenetrating solutes) than the reference cell. Cells placed in hypotonic solutions plump up rapidly as the water rushes into them.

A solution's osmolarity is based solely on its total solute concentration. Its tonicity is based on how the solution affects cell volume, which depends on (1) solute concentration and (2) solute permeability of the plasma membrane.

(1) Membrane transport processes for which ATP is required, such as solute pumping and endocytosis. (2) "Active Transport" also refers specifically to solute pumping.

Enzyme-like protein carrier that mediates active transport of solutes such as amino acids and ions uphill against their concentration gradients.

• - Primary active transport, in which the energy to do work comes directly from the hydrolysis of ATP.
• - Secondary active transport, in which the transport is driven indirectly by energy stored in the ionic gradients created by primary active transport pumps.

A type of active transport in which the energy needed to drive the transport process is provided directly by hydrolysis of ATP.

A primary active transport system that simultaneously drives Na1 out of cell against a steep gradient and pumps K1 back in. Also called the Na1-K1 ATPase.

The combined difference in concentration and charge; influences the distribution and direction of diffusion of ions.

Transport of large particles and macromolecules into or out of a cell or between its compartments in membrane-bound sacs. Energized by ATP or sometimes GTP (guanosine triphosphate).

Moving substances into, across, and then out of the cell.

Moving substances from one area (or membraneous organelle) in the cell to another.

Engulfing of foreign solids by phagocytic cells

Vesicle formed as a result of phagocytosis

The flowing movement of the cytoplasm of a phagocyte.

Engulfing of extracellular fluid by cells. (also called fluid-phase endocytosis)

The type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs. Substances taken up by this process include enzymes, insulin, low-density lipoprotein, and iron. Unfortunately, flu viruses, diphtheria, and cholera toxins also use this route to enter our cells.

Tubular of flask shaped inpocketings of the plasma membrane seen in many cell types. They are smaller than clathrin-coated pits, and their protein coat is thinner.

They play a significant role in all forms of endocytosis.

Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane. Accounts for hormone secretion, neurotransmitter release, mucus secretion, and in some cases ejection of waste.

Voltage across the plasma membrane. It is electrical potential energy resulting from the separation of oppositely charged particles. In cells, the oppositely charged particles are ions, and the barrier that keeps them apart is the plasma membrane.

The voltage that exists across the plasma membrane during the resting state of an excitable cell; ranges from 50 to 100 millivolts depending on the cell type.

State of a plasma membrane of an unstimulate neuron or muscle cell in which the inside of the cell is relatively negative in comparison to the outside; the resting state.

The cellular material surrounding the nucleus and enclosed by the plasma membrane.

Viscous, semitransparent fluid substance of cytoplasm in which other elements are suspended.

Small cellular structures (ribosomes, mitochondria, and others) that perform specific metabolic functions for the cell as a whole.

Cytoplasmic organelles responsible for ATP generation for cellular activities. Have two membranes - outer membrane smooth and featureless, inner membrane folds inward forming shelflike cristae that protrude into the matrix, the gel-like substance within the mitochondrion.

Multistep mitochondrial process where metabolites are broken down and oxidized, some of the energy is released and used to attach phosphate groups to ADP molecules to form ATP.

Cytoplasmic organelles at which proteins are synthesized. Composed of proteins and a variety of RNAs called ribosomal RNAs.

Float freely in the cytoplasm, make soluble proteins that function in the cytosol, as well as those imported into mitochondria and some other organelles.

Attached to membranes, forming a complex called the rough endoplasmic reticulum. Synthesize proteins destined either for incorporation into cell membranes or lysosomes, or for export from the cell.

Membraneous network of tubular or saclike channels in the cytoplasm of a cell.

Any cavity or enclosed space serving as a reservoir.

Membraneous system close to the cell nucleus that packages proteins secretions for export, pacakages enzymes into lysosomes for cellular use, and modifies proteins destined to become part of cellular membranes.