Chapter 7

Question 1

Cellular Membrana is…

Answer 1

Selectively permeable

Question 2

Amphipathic

Answer 2

Has both a hydrophilic and hydrophobic regions

Question 3

Fluid mosaic model

Answer 3

The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids

Question 4

Evolution of Differences in Membrane Lipid Composition

Answer 4

Evolution led to differences in lipid composition (e.g. fish in icy-cold water have a high proportion of unsaturated hydrocarbon tails, enabling the membrane to stay fluid. Bacteria in extreme heats and their composition allows them to stay fluid in that heat. Some organisms can change their composition in places where temperatures vary)

Question 5

Transmembrane Protein

Answer 5

Span the whole membrane

Question 6

Integral Proteins

Answer 6

penetrate the bilayer but do not go all the way through

Question 7

N-terminus

Answer 7

On the extracellular side of a transmembrane protein

Question 8

C-terminus

Answer 8

On the cytoplasmic side of the transmembrane protein

Question 9

Transport

Answer 9

Can consist of a transport channel protein or a protein that changes shape to move molecules across the membrane

Question 10

Enzymatic activity

Answer 10

A protein in the membrane could be an enzyme with the active site exposed to the substances in the adjacent solution

Question 11

Signal transduction

Answer 11

A membrane protein may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone which may cause the protein to change shape, allowing it to relay a message to the inside of the cell

Question 12

Cell-cell recognition

Answer 12

some glycol-proteins serve as identification tags that are specifically recognized by membrane proteins of other cells (Shorter bonding)

Question 13

Intercellular joining

Answer 13

membrane proteins of adjacent cells may hook together in various kinds of auctions (gap junctions or tight junctions) (Longer bonding)

Question 14

Attachment to cytoskeleton and extracellular matrix (ECM)

Answer 14

Microfilaments or other elements of the cytoskeleton may be noncovalently bound to membrane proteins which helps maintain cell shape and stabilizes the location the location of certain membrane proteins. Proteins bound to ECM molecules can coordinate extracellular and intracellular changes

Question 15

Peripheral Proteins

Answer 15

Proteins bound to the surface of the membrane

Question 16

glycolipid

Answer 16

A membrane carbohydrate that is bound to a lipid

Question 17

glycoprotein

Answer 17

A membrane carbohydrate that is bound to a protein

Question 18

Synthesis and sidedness of membranes

Answer 18

Membranes have distinct inside and outside faces (the two lipid layers may differ in composition and each protein has directional orientation)

Question 19

Selective permeability

Answer 19

The ability to allow some substances to cross the membrane more easily than others

Question 20

Transport Proteins

Answer 20

allows the passage of hydrophilic substances through the membrane

Question 21

aquaporins

Answer 21

Channels proteins that greatly facilitate the transport of water molecules

Question 22

Carrier proteins

Answer 22

Bind to molecules and change their shape to get them across the membrane

Question 23

Passive transport

Answer 23

Uses diffusion and requires no energy

Question 24

diffusion

Answer 24

The movement of any substance so that they spread out into the available space

Question 25

Concentration gradient

Answer 25

The region along which the density of a chemical substance increases or decreases

Question 26

Osmosis

Answer 26

the diffusion of water across a selectively permeable membrane

Question 27

Tonicity

Answer 27

the ability of a surrounding solution to cause a cell to gain or lose water.The tonicity of a solution depends on its concentration of solutes that cannot cross the membrane relative to that inside the cell

Question 28

Isotonic

Answer 28

Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Question 29

Hypertonic

Answer 29

Solute concentration is greater than that inside the cell; the cell loses water

Question 30

Hypotonic

Answer 30

Solute concentration is less than that inside the cell; the cell gains water

Question 31

Osmoregulation

Answer 31

the control of solute concentrations and water balance

Question 32

Facilitated diffusion

Answer 32

transport proteins speed the passive movement of molecules across the plasma membrane

Question 33

Ion channels

Answer 33

channels that transport ions

Question 34

Gated channels

Answer 34

open or close in response to a stimulus

Question 35

Active transport

Answer 35

requires energy, usually in the form of ATP hydrolysis, to move substances against their concentration gradients

Question 36

Sodium-potassium pump

Answer 36

an animal cell has a much higher potassium (K+) and a much lower sodium (Na+)concentration compared to its surroundings. This is controlled by the sodium-potassium pump, a transport protein that is energized by transfer of a phosphate group from the hydrolysis of ATP

Question 37

Membrane potential

Answer 37

the voltage across a membrane (-50 to -200 millivolts (mV) and is negative relative to the outside). Voltage is created by differences in the distribution of positive and negative ions across a membrane. The cytoplasmic side of the membrane is negative in charge relative to the extracellular side

Question 38

Electrochemical gradient

Answer 38

drive the diffusion of ions across a membrane (A chemical force [the ion’s concentration gradient] An electrical force [the effect of the membrane potential on the ion’s movement])

Question 39

Proton pump

Answer 39

The main electrogenic pump of plants, fungi, and bacteria which actively transports hydrogen ions (H+) out of the cell

Question 40

Cotransport

Answer 40

occurs when active transport of a solute indirectly drives transport of other substances

Question 41

Exocytosis

Answer 41

When the cell secretes certain molecules by the fusion of vesicles with the plasma membrane

Question 42

Endocytosis

Answer 42

The cell takes. in molecules and particulate matter by forming new vesicles form the plasma membrane

Question 43

Phagocytosis

Answer 43

A cell engulfs a particle by extending pseudopodia around it and packaging it within a membranous sac called a food vacuole. The particle will be digested when the vacuole fuses with a lysosome containing hydrolytic enzymes

Question 44

Pinocytosis

Answer 44

A cell continually "gulps" droplets of extracellular fluid into. tiny vesicles, formed by infolding of the plasma membrane. The cell obtains to molecules dissolved in the droplets. Nonspecific for the substances it transports

Question 45

Receptor-mediated cytosis

Answer 45

A specialized type of pinocytosis that enables the cell to acquire bulk quantities of specific substances. Proteins with receptor sites in the membrane react when specific solutes bind to the receptors. The receptor proteins then cluster into coated pits and form vesicles containing the bound solute