Chapter 3 Cell Membrane Structure and Function

Question 1

Active Transport

Answer 1

The movement of materials across a membrane through the use of cellualar energy, normally against a conecentration gradient.

Question 2

Carrier Protein

Answer 2

A membrane protein that facilitates the diffusion of specific substances across the membrane. The molecule to be transported bind to the outer surface of the carrier protein; the protein then changes shape, allowing the molecule the move across the membrane through the protein.

Question 3

Cell Wall

Answer 3

A layer of material, normally made up of cellulose or cullulose-like material, that is outside the plasma membrane of plants, fungi, bacteria, and some protists.

Question 4

Channel Protein

Answer 4

A membrane protein that forms a channel or pore completely through the membrane and that is usually permeable to one or to a few water-soluble molecules, especially ions.

Question 5

Concentration Gradient

Answer 5

The difference in concentration of a substance between two parts of a fluid or across a barrier such as a membrane.

Question 6

Diffusion

Answer 6

The net movement of particles from a region of high concentration of that type of particle to a region of low concentration, driven by the concentration gradient; may occur entirely within a fluid or across a barrier such as a membrane.

Question 7

Endocytosis

Answer 7

The process in which the plasma membrane engulfs extracellular material, forming membrane-bound sacs that enter the cytoplasm and the thereby move material into the cell.

Question 8

Exocytosis

Answer 8

The process in which intracellular material is enclosed within a membrane-bound sac that moes to the plasma membrane and fuses with it, releasing the material outside the cell.

Question 9

Facilitated Diffusion

Answer 9

The diffusion of molecules across a membrane, assisted by protein pores or carrieres embedded in the membrane.

Question 10

Fluid Mosaic

Answer 10

A model of membrane structure; according to this model, membranes are composed of a double layuer of phospholipids in which various proteins are embedded. The phospholipid bilayer is a somewhat fluid matrix that allows the movement of proteins within it.

Question 11

Hydrophilic

Answer 11

Pertaining to a substance that dissolves readily in water or to parts of a large molecule that form hydrogen bonds with water.

Question 12

Hydrophobic

Answer 12

Pertaining to a substance that dissolves readily in water or to parts of a large molecule that form hydrogen bonds with water.

Question 13

Osmosis

Answer 13

The diffusion of water across a differentially permeable membrane, normally down a concentration gradient of free water molecules. Water moves into the solution that has na lower conecentration of free water from a solution with the higher concentration of free water.

Question 14

Passive Transport

Answer 14

The movement of materials across a membrane down a gradient of concentration, pressure, or eletrical charge without using cellular energy.

Question 15

Phospholipid Bilayer

Answer 15

A double layer of phospholipids that forms the basis of all cellular membranes. The phospholipid heads, which are hydrophilic, face the water of extracellular fluid or the cytoplasm; the tails, which are hydrophobic are buried in the middle of the bilayer.

Question 16

Plasma Membrane

Answer 16

The outer membrane of a cell, composed of a bilayer of phospholipids in which proteins are embedded.

Question 17

Receptor Protein

Answer 17

A protein, located on a membrane (or in the cytoplasm), that recognizes and binds to specific molecules. Binding by receptor proteins typically triggers a response by a cell, such as endocytosis, increased metabolic rate, or cell division.

Question 18

Recognition Protein

Answer 18

A protein or glycoprotein protuding from the outside surface of a plasma membrane that identifies a cell as belongin to a particular species, to a specific individual of that species, and in many cases to one specific organ within the individual.

Question 19

Selectively Permeable

Answer 19

Refers to membranes across which some substances may pass freely while other substances cannot pass.

Question 20

Simple Diffusion

Answer 20

The diffusion of water, dissolved gases, or lipid-soluble molecules through the phospholipid bilayer of a cellular membrane.

Question 21

Transport Protein

Answer 21

A protein that regulates the movement of water-soluble molecules through the plasma membrane.

Question 22

Vesicle

Answer 22

(1) a small membrane-bound sac within the cytoplasm; (2) a small, hollow ball composed of mprotein and lipid; forms spontaneously when a solution of protein and lipid is agitated.