Chapter 3 - Cells: the Living Unit

Question 1

Cell theory is:

Answer 1

• The cell is the smallest unit of life
• All organisms are made of one or more cells
• Cells only arise from other cells

Question 2

principle of complementarity of structure and function is:

Answer 2

the activities of cells are dictated by their shapes, and by the types and relative numbers of the subcellular structures they contain.

Question 3

A human cell has three main parts:

Answer 3

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.

Question 4

Extracellular fluid (ECF) includes:

Answer 4

interstitial fluid,
blood plasma,
and cerebrospinal fluid.

Question 5

Cellular secretions

Answer 5

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).

Question 6

_____is the most abundant extracellular material. Serves as the cell glue and in connective tissue ranges from soft to rock-hard

Answer 6

extracellular matrix

Question 7

______separates two of the body’s major fluid compartments—the intracellular fluid within cells and the extracellular fluid outside cells

Answer 7

The Plasma Membrane

Question 8

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.

Answer 8

fluid mosaic model

Question 9

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

Answer 9

Tight Junction

Question 10

Cell junction composed of thickened plasma membranes joined by filaments.

Answer 10

Desmosomes Junction

Question 11

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

Answer 11

Gap Junction

Question 12

What basic structure do all cellular membranes share?

Answer 12

All cellular membranes consist of a double layer of phospholipids in which proteins are embedded.

Question 13

Which two types of cell junctions would you expect to find between muscle cells of the heart?

Answer 13

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.

Question 14

Which type—saturated or unsaturated—would make the membrane more fluid? Why?

Answer 14

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.

Question 15

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

Answer 15

active process

Question 16

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:

Answer 16

Passive process

Question 17

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

Answer 17

Concentration Gradient

Question 18

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:

Answer 18

Diffusion

Question 19

The three types of passive transport across the plasma membrane are

Answer 19

simple diffusion, facilitated diffusion, and osmosis.

Question 20

The speed of diffusion is influenced by three factors:

Answer 20

Concentration
Molecular Size
Temperature

Question 21

A membrane that allows certain substances to pass while restricting the movement of others; also called differentially permeable membrane.

Answer 21

Selectively permeable membrane

Question 22

What determines whether a given substance can cross the plasma membrane?

Answer 22

Lipid solubility, and size

Question 23

Simple Diffusion is

Answer 23

The unassisted transport across a plasma membrane of a lipid-soluble or very small particle.

Question 24

Facilitated Diffusion is

Answer 24

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.

Question 25

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

Answer 25

Carrier

Question 26

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

Answer 26

Channel

Question 27

These channels are always open and simply allow ions or water to move according to concentration gradients.

Answer 27

leakage channels

Question 28

Theses channels are controlled (opened or closed), usually by chemical or electrical signals.

Answer 28

Gated Channels

Question 29

Diffusion of a solvent through a selectively permeable membrane from a dilute solution into a more concentrated one is:

Answer 29

Osmosis

Question 30

Transmembrane proteins that form water channels describes

Answer 30

Aquaporins (AQP’s)

Question 31

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

Answer 31

Osmolarity

Question 32

Pressure of fluid in a system

Answer 32

Hydrostatic Pressure

Question 33

A measure of the tendency of a solvent to move into a more concentrated solution.

Answer 33

Osmotic Pressure

Question 34

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)

Answer 34

Tonicity

Question 35

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

Answer 35

Isotonic Solution

Question 36

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).

Answer 36

Hypertonic Solutions

Question 37

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.

Answer 37

Hypotonic Solution

Question 38

What is the energy source for all types of diffusion?

Answer 38

Kenetic diffusion

Question 39

How do the two types of facilitated diffusion differ?

Answer 39

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.

Question 40

The two major means of active membrane transport:

Answer 40

active transport and vesicular transport.

Question 41

Active Transport is

Answer 41

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.

Question 42

Primary Active Transport

Answer 42

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

Question 43

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

Answer 43

electrochemical gradients

Question 44

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).

Answer 44

Secondary Active Transport

Question 45

Transport of large particles and macromolecules into or out of a cell or between its compartments in membrane-bound sacs.

Answer 45

Vesicular Transport

Question 46

Phagocystosis

Answer 46

Engulfing of solids by (phagocytic) cells. (cell eating)

Question 47

Vesicle formed as a result of phagocytosis.

Answer 47

phagosome

Question 48

The flowing movement of the cytoplasm of a phagocyte as it moves across a surface is

Answer 48

amoeboid motion

Question 49

also called fluid-phase endocytosis, a bit of infolding plasma membrane surrounds a very small volume of extracellular fluid containing dissolved molecules

Answer 49

pinocytosis (“cell drinking”)

Question 50

Engulfing of extracellular fluid by cells.

Answer 50

pinocytosis (“cell drinking”)

Question 51

receptor-mediated endocytosis

Answer 51

The type of endocytosis in which engulfed particles attach to receptors before endocytosis occurs.

Question 52

Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane.

Answer 52

Exocytosis

Question 53

Does the Na+-K+ ATPase pump K+ into or out of the cell? What is the ratio of Na+ to K+ it pumps?

Answer 53

The Na+-K+ ATPase pumps K+ into the cell. It expels three Na+ for every two K+ it brings in.

Question 54

As a cell grows, its plasma membrane expands. Does this membrane expansion involve endocytosis or exocytosis?

Answer 54

The plasma membrane expands as a result of exocytosis.

Question 55

Phagocytic cells gather in the lungs, particularly in the lungs of smokers. What is the connection?

Answer 55

Phagocytic cells engulf debris, and a smoker’s lungs would be laden with carbon particles and other debris from smoke inhalation.

Question 56

Which vesicular transport process allows a cell to take in cholesterol from the extracellular fluid?

Answer 56

Cholesterol is taken in by receptor-mediated endocytosis

Question 57

Voltage across the plasma membrane.

Answer 57

Membrane potential

Question 58

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.

Answer 58

resting membrane potential

Question 59

What process establishes the resting membrane potential?

Answer 59

Diffusion of ions, mainly the diffusion of K+ from the cell through leakage channels, establishes the resting membrane potential.

Question 60

Is the inside of the plasma membrane negative or positive relative to its outside in a polarized membrane of a resting cell?

Answer 60

In a polarized membrane of a resting cell, the inside is negative relative to its outside.