Chapter 3 - Cells: the Living Unit Flashcards
Chapter 3 - Cells: the Living Unit
Cell theory is:
- The cell is the smallest unit of life
- All organisms are made of one or more cells
- Cells only arise from other cells
principle of complementarity of structure and function is:
the activities of cells are dictated by their shapes, and by the types and relative numbers of the subcellular structures they contain.
A human cell has three main parts:
The plasma membrane: the outer boundary of the cell, which acts as a selectively permeable barrier.
The cytoplasm (si′to-plazm): the intracellular fluid packed with organelles, small structures that perform specific cell functions.
The nucleus (nu′kle-us): an organelle that controls cellular activities. Typically the nucleus lies near the cell’s center.
Extracellular fluid (ECF) includes:
interstitial fluid,
blood plasma,
and cerebrospinal fluid.
Cellular secretions
Cellular secretions. These secretions include substances that aid in digestion (intestinal and gastric fluids) and some that act as lubricants (saliva, mucus, and serous fluids).
_____is the most abundant extracellular material. Serves as the cell glue and in connective tissue ranges from soft to rock-hard
extracellular matrix
______separates two of the body’s major fluid compartments—the intracellular fluid within cells and the extracellular fluid outside cells
The Plasma Membrane
The ________of membrane structure depicts the plasma membrane as an exceedingly thin (7–10 nm) structure composed of a double layer, or bilayer, of lipid molecules with protein molecules “plugged into” or dispersed in it.
fluid mosaic model
Area where plasma membranes of adjacent cells are tightly bound together, forming an impermeable barrier.
Tight Junction
Cell junction composed of thickened plasma membranes joined by filaments.
Desmosomes Junction
A passageway between two adjacent cells; formed by transmembrane proteins called connexons.
Gap Junction
What basic structure do all cellular membranes share?
All cellular membranes consist of a double layer of phospholipids in which proteins are embedded.
Which two types of cell junctions would you expect to find between muscle cells of the heart?
The heart has desmosomes (anchoring junctions) that secure cardiac cells together as the heart pumps, and gap junctions (communicating junctions) that allow ions to flow from cardiac cell to cardiac cell.
Which type—saturated or unsaturated—would make the membrane more fluid? Why?
Unsaturated phospholipids would make the membrane more fluid. The double bonds cause the fatty acid chains to kink so that they cannot be packed closely, and this makes the membrane more fluid.
Membrane transport processes for which ATP is directly or indirectly required, e.g., solute pumping and endocytosis. (2) “Active transport” also refers specifically to solute pumping.
The cell provides the metabolic energy (usually ATP) needed to move substances across the membrane. This describes
active process
Membrane transport processes that move substances down their concentration gradients (e.g., diffusion). They are driven by kinetic energy and so do not require cellular energy (such as ATP).
Substances cross the membrane without any energy input from the cell describes:
Passive process
The difference in the concentration of a particular substance between two different areas.
Concentration Gradient
is the movement of molecules or ions from an area where they are in higher concentration to an area where they are in lower concentration describes:
Diffusion
The three types of passive transport across the plasma membrane are
simple diffusion, facilitated diffusion, and osmosis.
The speed of diffusion is influenced by three factors:
Concentration
Molecular Size
Temperature
A membrane that allows certain substances to pass while restricting the movement of others; also called differentially permeable membrane.
Selectively permeable membrane
What determines whether a given substance can cross the plasma membrane?
Lipid solubility, and size
Simple Diffusion is
The unassisted transport across a plasma membrane of a lipid-soluble or very small particle.
Facilitated Diffusion is
Passive transport process used by certain large or charged molecules (e.g., glucose, Na+) that are unable to pass through the plasma membrane unaided. Involves movement through channels or movement facilitated by a membrane carrier.
A transmembrane protein that changes shape to envelop and transport a polar substance across the cell membrane is a
Carrier
A transmembrane protein that forms an aqueous pore, allowing substances to move from one side of the membrane to the other.
Channel
These channels are always open and simply allow ions or water to move according to concentration gradients.
leakage channels
Theses channels are controlled (opened or closed), usually by chemical or electrical signals.
Gated Channels
Diffusion of a solvent through a selectively permeable membrane from a dilute solution into a more concentrated one is:
Osmosis
Transmembrane proteins that form water channels describes
Aquaporins (AQP’s)
The number of solute particles present in 1 liter of a solution is
Osmolarity
Pressure of fluid in a system
Hydrostatic Pressure
A measure of the tendency of a solvent to move into a more concentrated solution.
Osmotic Pressure
refers to the ability of a solution to change the shape (or plasma membrane tension) of cells by altering the cells’ internal water volume (tono = tension)
Tonicity
A solution with a concentration of nonpenetrating solutes equal to that found in the reference cell is
Isotonic Solution
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).
Hypertonic Solutions
A solution that is more dilute (containing fewer nonpenetrating solutes) than the reference cell. Cells placed in hypotonic solutions plump up rapidly as water diffuses into them.
Hypotonic Solution
What is the energy source for all types of diffusion?
Kenetic diffusion
How do the two types of facilitated diffusion differ?
In channel-mediated diffusion, the diffusing substance moves through a channel protein. In carrier-mediated diffusion, the diffusing substance attaches to a carrier protein that moves it across the membrane.
The two major means of active membrane transport:
active transport and vesicular transport.
Active Transport is
Membrane transport processes for which ATP is directly or indirectly required, e.g., solute pumping and endocytosis. (2) “Active transport” also refers specifically to solute pumping.
Primary Active Transport
A type of active transport in which the energy needed to drive the transport process is provided directly by hydrolysis of ATP.
The combined difference in concentration and charge; influences the distribution and direction of diffusion of ions describes`
electrochemical gradients
A type of active transport in which the energy needed to drive the transport process is provided by the electrochemical gradient of another molecule (which moves “downhill” through the transport protein at the same time as another molecule is moved “uphill” against its gradient). Also called cotransport or symport (when the two transported molecules move in the same direction) or antiport (when the two transported molecules move in opposite directions).
Secondary Active Transport
Transport of large particles and macromolecules into or out of a cell or between its compartments in membrane-bound sacs.
Vesicular Transport
Phagocystosis
Engulfing of solids by (phagocytic) cells. (cell eating)
Vesicle formed as a result of phagocytosis.
phagosome
The flowing movement of the cytoplasm of a phagocyte as it moves across a surface is
amoeboid motion
also called fluid-phase endocytosis, a bit of infolding plasma membrane surrounds a very small volume of extracellular fluid containing dissolved molecules
pinocytosis (“cell drinking”)
Engulfing of extracellular fluid by cells.
pinocytosis (“cell drinking”)
receptor-mediated endocytosis
The type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs.
Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane.
Exocytosis
Does the Na+-K+ ATPase pump K+ into or out of the cell? What is the ratio of Na+ to K+ it pumps?
The Na+-K+ ATPase pumps K+ into the cell. It expels three Na+ for every two K+ it brings in.
As a cell grows, its plasma membrane expands. Does this membrane expansion involve endocytosis or exocytosis?
The plasma membrane expands as a result of exocytosis.
Phagocytic cells gather in the lungs, particularly in the lungs of smokers. What is the connection?
Phagocytic cells engulf debris, and a smoker’s lungs would be laden with carbon particles and other debris from smoke inhalation.
Which vesicular transport process allows a cell to take in cholesterol from the extracellular fluid?
Cholesterol is taken in by receptor-mediated endocytosis
Voltage across the plasma membrane.
Membrane potential
The voltage that exists across the plasma membrane during the resting state of an excitable cell; typically ranges from −50 to −90 millivolts depending on cell type.
resting membrane potential
What process establishes the resting membrane potential?
Diffusion of ions, mainly the diffusion of K+ from the cell through leakage channels, establishes the resting membrane potential.
Is the inside of the plasma membrane negative or positive relative to its outside in a polarized membrane of a resting cell?
In a polarized membrane of a resting cell, the inside is negative relative to its outside.
