Concept 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment

Question 1

Molecules have a type of energy called

Answer 1

thermal energy

Question 2

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

Answer 2

diffusion

Question 3

diffusion of a population of molecules may be

Answer 3

directional

Question 4

In the absence of other forces, a substance will diffuse from where it is more concentrated to where it is

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less concentrated

Question 5

the region along which the density of a chemical substance increases or decreases (in this case, decreases)

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concentration gradient

Question 6

diffusion across a biological membrane is called

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passive transport, since the cell expends no energy to move the molecules

Question 7

oxygen and carbon dioxide molecules into and out of cells by

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passive transport

Question 8

When a substance is more concentrated on one side of a membrane than on the other, there is a tendency for the substance to diffuse across the membrane down its

Answer 8

concentration gradient

Question 9

concentration gradient itself represents

Answer 9

potential energy

Question 10

The diffusion of free water across a selectively permeable membrane, whether artificial or cellular, is called

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osmosis

Question 11

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

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tonicity

Question 12

referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell

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isotonic

Question 13

osmosis is the diffusion, or net movement of water molecules across a

Answer 13

selectively permeable membrane

Question 14

example of osmosis is an artificial system divided in half using a ____________________ with a selectively permeable membrane

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u-shaped glass tube

Question 15

the tube contains water shown in blue and solute molecules which are

Answer 15

sugar molecules as green dots

Question 16

the membrane in the example has pores that are large enough to let ____________________ pass through but too small to let the ________________ through

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water molecules, sugar molecules

Question 17

this is called __________________, because it allows some substances like water to pass through, but blocks others like the sugar molecules

Answer 17

selectively permeable membrane

Question 18

difference in sugar concentration across the membrane means that

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movement of substances will occur to equalize the concentrations.

Question 19

some water molecules cluster around the

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hydrophilic, or water loving sugar molecules

Question 20

these water molecules don’t move around ________ in the solution

Answer 20

freely

Question 21

this means that the more sugar that’s present, the fewer

Answer 21

free molecules that there are to move around and diffuse

Question 22

if the membrane barrier weren’t there in the example the sugar and the free water would both diffuse each down its own concentration gradient until the concentration on both sides were

Answer 22

equal

Question 23

what we have is the conditions that causes ________

Answer 23

osmosis

Question 24

water moves from the area of lower solute concentration to the area of

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higher solute concentrations

Question 25

the volume of water has been adjusted on both sides by

Answer 25

osmosis

Question 26

the solution volume is now much higher on the _________ than on the ________ due to the movement of some much water

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right, left

Question 27

once the solute concentrations on both sides of the membrane are about equal the free water will move

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equally in both directions

Question 28

living cells have

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selectively permeable membranes

Question 29

osmosis is crucial to the function of all

Answer 29

cells

Question 30

the plasma membrane is permeable to ________________ and allows the movement of water into and out of the cells

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water molecules

Question 31

when a cell in a solution that is more concentrated than its cytoplasm it is said to be in a

Answer 31

hypertonic solution

Question 32

the solute molecules attract water molecules so that fewer water molecules are

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free to diffuse across the membrane

Question 33

in a hypertonic solution of free molecules is _________ on the inside of the cell than the __________

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higher, outside

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osmosis occurs as water molecules move down their concentration gradient leaving the cell. as a result the cell

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shrinks

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example the glucose molecules have been distributed evenly inside and outside the cell. the cell is in an

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isotonic solution,

Question 36

where the concentration if the external solution and the cytoplasm are the same

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isotonic solution

Question 37

in isotonic solution the cell neither

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shrinks nor swells

Question 38

example there are more glucose molecules inside the cell than outside. this cell is in a

Answer 38

hypotonic solution

Question 39

the solute molecules attract water molecules, so _________ water molecules are free to diffuse across the membrane

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fewer

Question 40

the concentration of free water molecules is higher on the outside of the cell than the inside

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hypertonic solution

Question 41

osmosis occurs as water molecules move down their concentration gradient, entering the cell. as a result the cell

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swells

Question 42

animal cells lack rigid

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cell walls

Question 43

when animals cells are exposed to a hypotonic environment water rushes into the cell and the cell

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swells

Question 44

if water is not removed from the cell, the pressure will exceed the tensile strength of the cell and it will

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burst open or lyse

Question 45

single-celled protists living in freshwater environments have ________________________ that pump water back out of the cell which maintains osmosis equilibrium and avoids lysis

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contractile vacuoles

Question 46

plant cells are surround by

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rigid cell walls

Question 47

when plant cells are exposed to a hypotonic environment water rushes into the cell, and the cell swells but it is kept from breaking by the

Answer 47

rigid cell wall

Question 48

the pressure of the cell pushing against the cell wall makes the cell _________ which is the desired state for most plant tissue

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turgid

Question 49

since animal cells lack a rigid cell walls, when they are exposed to a hypertonic environment water rushes out of the cell and the cell

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shrinks

Question 50

since plant cells are surrounded by rigid cell walls, when plant cells are exposed to a hypertonic environment, water rushes out of the cell and the plasma membrane does what

Answer 50

pulls away from the cell wall at multiple places, this is called plasmolysis

Question 51

plasmolysis causes the plant to

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wilt and can lead to plant death

Question 52

the control of solute concentrations and water balance is called

Answer 52

osmoregulation

Question 53

he relatively inelastic cell wall will expand only so much before it exerts a back pressure on the cell, called

Answer 53

turgor pressure

Question 54

polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane is called

Answer 54

facilitated diffusion

Question 55

the two types of transport proteins are

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channel proteins and carrier proteins.

Question 56

simply provide corridors that allow specific molecules or ions to cross the membrane

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Channel proteins

Question 57

Channel proteins that transport ions are called

Answer 57

ion channels

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open or close in response to a stimulus

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gated channels

Question 59

some gated channels, the stimulus is

Answer 59

electrical

Question 60

undergo a subtle change in shape that somehow translocates the solute-binding site across the membrane

Answer 60

Carrier proteins