Chapter 7

Front 1

What is the boundary that separates the living cell from its surroundings?

Back 1

The plasma membrane

Front 2

Who were the two men that proposed a sandwich model in which the phospholipid bilayer lies between two layers of globular proteins?

Back 2

Hugh Davson and James Danielli

Front 3

Who were the two men that proposed that the membrane is a mosaic of proteins dispersed within the bilayer, with only the hydrophilic regions exposed to water?

Back 3

S. J. Singer and G. Nicolson

Front 4

As temperatures cool, membranes switch from a ____ to a ____

Back 4

fluid state to a solid state

Front 5

At warm temperatures (such as 37°C) what happens?

Back 5

cholesterol restrains movement of phospholipids

Front 6

What happens at cool temperatures?

Back 6

it maintains fluidity by preventing tight packing

Front 7

What is a collage of different proteins embedded in the fluid matrix of the lipid bilayer?

Back 7

A membrane

Front 8

Bound to the surface of the membrane are called?

Back 8

Peripheral proteins

Front 9

What penetrates the hydrophobic core?

Back 9

Integral proteins

Front 10

Integral proteins that span the membrane are called?

Back 10

transmembrane proteins

Front 11

What are the Six major functions of membrane proteins?

Back 11

-Transport
-Enzymatic activity
-Signal transduction
-Cell-cell recognition
-Intercellular joining
-Attachment to the cytoskeleton an Extracellular matrix (ECM)

Front 12

How do Cells recognize each other?

Back 12

by binding to surface molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane

Front 13

What forms when Membrane carbohydrates covalently bonded to lipids?

Back 13

glycolipids

Front 14

What forms when Membrane carbohydrates covalently bonded to protein?

Back 14

glycoproteins

Front 15

what can dissolve in the lipid bilayer and pass through the membrane rapidly?

Back 15

Hydrophobic (nonpolar) molecules

Front 16

______ do not cross the membrane easily

Back 16

Polar molecules

Front 17

hydrocarbons are examples of which molecules?

Back 17

Hydrophobic (nonpolar) molecules

Front 18

Sugars are examples of which molecules?

Back 18

Polar molecules

Front 19

What allow passage of hydrophilic substances across the membrane?

Back 19

Transport proteins

Front 20

If a cell contains a nucleus, it must be a(n) _____.

Back 20

Eukaryotic cell

Front 21

The plasma membrane exhibits _____________, allowing some substances to cross it more easily than others

Back 21

selective permeability

Front 22

the most abundant lipid in the plasma membrane

Back 22

Phospholipids

Front 23

Phospholipids are ________________, containing hydrophobic and hydrophilic regions

Back 23

amphipathic molecules

Front 24

The ______________ states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

Back 24

fluid mosaic model

Front 25

Membranes have been chemically analyzed and found to be made of ______ and ______

Back 25

proteins and lipids

Front 26

determines most of the membrane’s specific functions

Back 26

Proteins

Front 27

A cell must exchange materials with its surroundings, a process controlled by the _____________

Back 27

plasma membrane

Front 28

Some transport proteins, called _________, have a hydrophilic channel that certain molecules or ions can use as a tunnel

Back 28

channel proteins

Front 29

Channel proteins called __________ facilitate the passage of water

Back 29

aquaporins

Front 30

Other transport proteins, called ___________, bind to molecules and change shape to shuttle them across the membrane

Back 30

carrier proteins

Front 31

the tendency for molecules to spread out evenly into the available space

Back 31

Diffusion

Front 32

At ______________, as many molecules cross the membrane in one direction as in the other direction

Back 32

dynamic equilibrium

Front 33

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

Back 33

concentration gradient

Front 34

Does work need to be done to move substances down the concentration gradient?

Back 34

no

Front 35

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

Back 35

passive transport

Front 36

the diffusion of water across a selectively permeable membrane

Back 36

Osmosis

Front 37

Water diffuses across a membrane from the region of _____ solute concentration to the region of ______ solute concentration until the solute concentration is ______ on both sides

Back 37

lower, higher, equal

Front 38

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

Back 38

Tonicity

Front 39

A solution where the solute concentration is the same as that inside the cell

Back 39

Isotonic solution

Front 40

A solution where there is no net water movement across the plasma membrane

Back 40

Isotonic solution

Front 41

A solution where the solute concentration is greater than that inside the cell

Back 41

Hypertonic solution

Front 42

A solution where the cell loses water

Back 42

Hypertonic solution

Front 43

A solution where the solute concentration is less than that inside the cell

Back 43

Hypotonic solution

Front 44

A solution where the cell gains water

Back 44

Hypotonic solution

Front 45

the control of solute concentrations and water balance, is a necessary adaptation for life in such environments

Back 45

Osmoregulation

Front 46

What helps maintain water balance?

Back 46

Cell walls

Front 47

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

Back 47

turgid

Front 48

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

Back 48

flaccid

Front 49

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

Back 49

plasmolysis

Front 50

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

Back 50

facilitated diffusion

Front 51

provides corridors that allow a specific molecule or ion to cross the membrane

Back 51

Channel proteins

Front 52

What 2 things do channel proteins include?

Back 52

aquaporins & ion channels

Front 53

Is facilitated diffusion passive or active & why?

Back 53

Facilitated diffusion is still passive because the solute moves down its concentration gradient, and the transport requires no energy

Front 54

_____________ moves substances against their concentration gradients

Back 54

Active transport

Front 55

Active transport requires energy, usually in the form of ________

Back 55

ATP

Front 56

____________ allows cells to maintain concentration gradients that differ from their surroundings

Back 56

Active transport

Front 57

the voltage difference across a membrane

Back 57

Membrane potential

Front 58

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

Back 58

Voltage

Front 59

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

Back 59

electrochemical gradient

Front 60

What are the two combined forces that drive the diffusion of ions across a membrane?

Back 60

-A chemical force (the ion’s concentration gradient)

-An electrical force (the effect of the membrane potential on the ion’s movement)

Front 61

a transport protein that generates voltage across a membrane

Back 61

electrogenic pump

Front 62

the major electrogenic pump of animal cells

Back 62

sodium-potassium pump

Front 63

The main electrogenic pump of plants, fungi, and bacteria

Back 63

proton pump

Front 64

_______________ help store energy that can be used for cellular work

Back 64

Electrogenic pumps

Front 65

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

Back 65

Cotransport

Front 66

How do small molecules and water enter or leave the cell?

Back 66

through the lipid bilayer or via transport proteins

Front 67

How do large molecules, such as polysaccharides and proteins, cross the membrane?

Back 67

in bulk via vesicles

Front 68

Does bulk transport requires energy?

Back 68

yes

Front 69

In _________, transport vesicles migrate to the membrane, fuse with it, and release their contents

Back 69

exocytosis

Front 70

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

Back 70

endocytosis

Front 71

What are the three types of endocytosis?

Back 71

- Phagocytosis (“cellular eating”)
- Pinocytosis (“cellular drinking”)
- Receptor-mediated endocytosis

Front 72

When a cell engulfs a particle in a vacuole, it's called ___________

Back 72

phagocytosis

Front 73

What do vacuoles fuse with to digest a particle?

Back 73

lysosome

Front 74

In ___________, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles

Back 74

pinocytosis

Front 75

In _________________, binding of ligands to receptors triggers vesicle formation

Back 75

receptor-mediated endocytosis

Front 76

any molecule that binds specifically to a receptor site of another molecule

Back 76

ligand

Front 77

In a chloroplast, the stacks of membranous sacs are called _____.

Back 77

grana

Front 78

Because cells have a watery environment both inside and outside, the polar ends of the phospholipids in the plasma membrane form ____ layers

Back 78

double

Front 79

The fluid mosaic model describes a structure with ____.

Back 79

polar layers on the outside and nonpolar layer on the inside

Front 80

Because the phospholipid molecules and some proteins are free to move, the plasma membrane is said to be a ____.

Back 80

fluid mosaic

Front 81

A cell's contents would be the same as its surrounds, were it not for ____.

Back 81

selective permeability

Front 82

A plasma membrane is made up of a(n) _____.

Back 82

phospholipid bilayer

Front 83

In a cell, the sites of protein synthesis are the _________.

Back 83

ribosomes

Front 84

What are the Channel proteins that facilitate the passage of water called?

Back 84

aquaporins

Front 85

What are the transport proteins that bind to molecules and change shape to shuttle them across the membrane called?

Back 85

carrier proteins

Front 86

What is the tendency for molecules to spread out evenly into the available space?

Back 86

Diffusion

Front 87

Cellular membranes are fluid mosaics of ________ and ________

Back 87

lipids and proteins

Front 88

Membrane structure results in selective ___________

Back 88

permeability

Front 89

___________ is diffusion of a substance across a membrane with no energy investment

Back 89

Passive transport

Front 90

_____________ uses energy to move solutes against their gradients

Back 90

Active transport

Front 91

Bulk transport across the plasma membrane occurs by ___________ and _____________

Back 91

exocytosis and endocytosis