Unit lll - Membrane Transport and Functions

Question 1

Cell membrane controls what enters and exits the cell to maintain an internal balance called _______.

Answer 1

homeostasis

Question 2

It is a double layer of phospholipids

Answer 2

lipid bilayer

Question 3

Lipid bilayer contains almost proteins called ________

Answer 3

membrane proteins

Question 4

They predicted the bilayer membrane structure as early as 1925.

Answer 4

Gorter and Grendel

Question 5

Structure of Cell Membrane/Lipid Bilayer

Answer 5

a. Phosphate head is polar • (water loving)
b. Fatty acid tails non-polar • (water fearing)
c. Proteins embedded in membrane

Question 6

• Allows some molecules in and keeps other molecules out.
• The structure helps it be selective!

Answer 6

Selectively permeable

Question 7

In 1972, _______ and _______ proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the _________ exposed to water.

Answer 7

S. J. Singer and G. Nicolson
hydrophilic regions

Question 8

Seymour Jonathan Singer and Garth Nicolson proposed the ________

Answer 8

Fluid Mosaic Model

Question 9

• Lateral movements occurs ________
• Flip-flopping across the membrane is rare (_______)

Answer 9

10⁷ times per second

Once per month

Question 10

• Most of the ____, and some _____, drift laterally.
• Rarely does a molecule flip-flop transversely across the membrane

Answer 10

lipids
proteins

Question 11

The fluidity of membranes

Answer 11

a. Unsaturated vs Saturated Hydrocarbon chains
b. Cholesterol within the animal cell membrane

Question 12

Variations in lipid composition of cell membranes of many species appear to be ____________

Answer 12

adaptations to specific environmental conditions

Question 13

Types of Membrane Proteins

Answer 13

Integral Proteins
Pumps
Channel Proteins
Carrier Proteins
Enzyme Protein
Receptor Proteins

Question 14

70% of Cell membrane proteins part and parcel of membrane structure

Answer 14

Integral Proteins

Question 15

They transfer substances against Concentration / Electrical gradients

Answer 15

Pumps

Question 16

Opened and closed by gates

Answer 16

Channel Proteins

Question 17

Involved in transport of substances

Answer 17

Carrier Proteins

Question 18

Proteins takes place in membrane reaction

Answer 18

Enzyme Proteins

Question 19

They bear appropriate sites for recognition of Specific Ligands.

Answer 19

Receptor Proteins

Question 20

Proteins that penetrate the hydrophobic core

Answer 20

Integral proteins

Question 21

Proteins that are bound to the surface of the membrane

Answer 21

Peripheral proteins

Question 22

Functions of Cell Membrane

Answer 22

a. Transport
b. Enzymatic activity
c. Signal transduction
d. Cell - cell recognize
e. Intercellular joining
f. Attachment to the cytoskeleton and extracellular matrix (ECM)

Question 23

Cells recognize each other by binding to ________, often containing carbohydrates, on the extracellular surface of the plasma membrane.

Answer 23

surface molecules

Question 24

Membrane carbohydrates may be covalently bonded to lipids (forming __________) or more commonly to proteins (forming __________)

Answer 24

glycolipids
glycoproteins

Question 25

HIV can infect a cell that has ____ on its surface, as in most people. HIV cannot infect a cell lacking _____ on its surface, as in resistant individuals

Answer 25

CCR5

Question 26

can dissolve in the lipid bilayer and pass through the membrane rapidly, such as hydrocarbons

Answer 26

Hydrophobic (nonpolar) molecules

Question 27

do not cross the membrane easily, such as sugar

Answer 27

Hydrophilic (polar) molecules

Question 28

Allow passage of hydrophilic substances across the membrane

Answer 28

Transport proteins

Question 29

Have a hydrophilic channel that certain molecules or ions can use as a tunnel

Answer 29

Channel proteins

Question 30

Channel proteins called ________ facilitate the passage of water

Answer 30

aquaporins

Question 31

Bind to molecules and change shape to shuttle them across the membrane

Answer 31

Carrier proteins

Question 32

Two types of transport mechanism

Answer 32

Active process Passive process

Question 33

Types of Active process

Answer 33

Primary transport Secondary transport

Question 34

Types of passive process

Answer 34

Simple diffusion Facilitated diffusion Osmosis Bulk flow filtration

Question 35

Substances diffuse down their _____________, the region along which the density of a chemical substance increases or decreases.

Answer 35

concentration gradient

Question 36

The diffusion of a substance across a biological membrane is _________ because no energy is expended by the cell to make it happen.

Answer 36

passive transport

Question 37

Factors that influence diffusion rates

Answer 37

• Distance • Molecular size • Temperature • Steepness of Concentration Gradient • Membrane of Surface Area

Question 38

______________ ___________ can enter cells easily because they diffuse through the lipid portion of the membrane

Answer 38

Simple diffusion Lipophilic substances

Question 39

Membrane channels are transmembrane proteins Used by ions, very small water-soluble compounds Much more complex than simple diffusion.

Answer 39

Channel-Mediated Diffusion

Question 40

Diffusion Through the Plasma Membrane (3)

Answer 40

• Simple diffusion • Channel-mediated facilitated diffusion • Carrier-mediated facilitated diffusion

Question 41

It is the diffusion of water across a selectively permeable membrane

Answer 41

Osmosis

Question 42

Water Balance of Cells Without Walls

Answer 42

Tonicity Isotonic solution Hypertonic solution Hypotonic solution

Question 43

is the ability of a surrounding solution to cause a cell to gain or lose water

Answer 43

Tonicity

Question 44

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

Answer 44

Isotonic solution

Question 45

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

Answer 45

Hypertonic solution

Question 46

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

Answer 46

Hypotonic solution

Question 47

Effects of tonicity in animals and plants

Answer 47

a) animal cell (lysed, normal, shriveled) b) plant cell (turgid, flaccid, plasmolyzed)

Question 48

• A plant cell in a hypotonic solution swells until the wall opposes uptake; the cell is now ______ (firm)

Answer 48

turgid

Question 49

• If a plant cell and its surroundings are isotonic, there is no net movement of water into the cell; the cell becomes ______ (limp), and the plant may wilt

Answer 49

Flaccid

Question 50

In a hypertonic environment, plant cells lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called ________.

Answer 50

plasmolysis

Question 51

In __________, transport proteins speed the passive movement of molecules across the plasma membrane

Answer 51

facilitated diffusion

Question 52

moves substances against their concentration gradients

Answer 52

Active transport

Question 53

allows cells to maintain concentration gradients that differ from their surroundings

Answer 53

Active transport

Question 54

The __________ is one type of active transport system.

Answer 54

sodium-potassium pump

Question 55

Process of active transport

Answer 55

1. Insert Na 2. Insert ATP 3. Release Na 4. Attach K 5. Attach ATP 6. Attach K

Question 56

is the voltage difference across a membrane

Answer 56

Membrane potential

Question 57

is created by differences in the distribution of positive and negative ions across a membrane

Answer 57

Voltage

Question 58

Two combined forces, collectively called the ___________, drive the diffusion of ions across a membrane

Answer 58

electrochemical gradient

Question 59

the ion’s concentration gradient

Answer 59

Chemical force

Question 60

the effect of the membrane potential on the ion’s movement

Answer 60

electrical force

Question 61

It is a transport protein that generates voltage across a membrane.

Answer 61

Electrogenic pump

Question 62

The main electrogenic pump of plants, fungi, and bacteria is a ________.

Answer 62

proton pump

Question 63

It maintains membrane potential

Answer 63

Ion pumps

Question 64

occurs when active transport of a solute indirectly drives transport of other solutes.

Answer 64

Cotransport

Question 65

Bulk transport across the plasma membrane occurs by _______ and _______

Answer 65

exocytosis endocytosis

Question 66

• Small molecules and water enter or leave the cell through the ______ or via _________ • Large molecules, such as polysaccharides and proteins, cross the membrane in _____ via ______ • Bulk transport requires energy

Answer 66

• lipid bilayer or via transport proteins • bulk via vesicles

Question 67

In _______, transport vesicles migrate to the membrane, fuse with it, and release their contents • Many secretory cells use ________ to export their products

Answer 67

exocytosis

Question 68

In _______, the cell takes in macromolecules by forming vesicles from the plasma membrane

Answer 68

endocytosis