Cell Bio Exam 2: pt. 4 - Transport Across Membranes

0.0(0)
studied byStudied by 0 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/57

encourage image

There's no tags or description

Looks like no tags are added yet.

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

58 Terms

1
New cards

What 3 different mechanisms are involved in the movement of solutes across membranes?

1. simple diffusion 2. facilitated diffusion 3. active transport

2
New cards

What two different kinds of proteins are involved in facilitated diffusion?

channel protein and carrier proteins

3
New cards

What is simple diffusion?

the unassisted net movement of a solute from a region where its concetration is higher to a region where its concentration is lower

4
New cards

What kinds of molecules can undergo simple diffusion?

oxygen, ethanol, water, carbon dioxide

5
New cards

Why can only small and relatively nonpolar molecules undergo simple diffusion?

because membranes have a hydrophobic interior

6
New cards

What size of molecules are small enough to diffuse across membranes by simple diffusion?

up to 180 daltons

7
New cards

Are lipid bilayers relatively permeable to gases?

yes because they are nonpolar molecules

8
New cards

Is glycerol a polar molecule that is not permeable across membranes?

yes

9
New cards

Can ions simply diffuse across membranes?

no because 40kcal/mol of energy is required to move ions from an aqueous environment into a nonpolar environment

10
New cards

How can larger molecules move in and out of cells and organelles?

with the assistance of transport proteins like integral membrane proteins

11
New cards

Is an input of energy (ATP) required for facilitated diffusion?

no because the solute diffuses down the concentration gradient

12
New cards

What types of membrane transport are called passive transport?

simple and facilitated diffusion

13
New cards

What is the role of transport proteins in facilitated diffusion?

to provide a path through the lipid bilayer

14
New cards

How do carrier proteins facilitate diffusion?

bind solute molecules on one side of a membrane, undergo a conformation change, and release the solute on the other side of the membrane

15
New cards

How many solutes can carrier proteins transport?

one or two

16
New cards

What direction can carrier proteins transport solutes?

the directions can vary

17
New cards

What is it called when carrier proteins transport two solutes?

cotransport

18
New cards

What is it called when carrier proteins transport one solute?

uniport

19
New cards

What is it called when carrier proteins transport two solutes in the same direction?

symport

20
New cards

What is it called when carrier proteins transport two solutes in opposite directions?

antiport

21
New cards

What are examples of carrier proteins?

transporters or permeases

22
New cards

What is the glucose transporter?

a carrier protein that is a uniport carrier for glucose

23
New cards

In what direction is glucose transported by a glucose transporter?

inward

24
New cards

What is the glucose transporter called in erythrocytes?

GLUT1

25
New cards

How does GLUT1 work in erythrocytes?

it transports glucose through the membrane by the alternating conformation mechanism

26
New cards

What is the alternating conformation mechanism?

one conformation state, T1, has the binding site for glucose open on the outside of the cell and the other conformation state, T2, has the binding site open to the inside of the cell

27
New cards

What are the 4 steps of GLUT1 acting as a carrier protein?

1. D-glucose collides with and binds to GLUT1 in the T1 conformation

2. GLUT1 shifts to the T2 conformation

3. the conformational change causes the release of glucose

4. GLUT1 returns to the T1 conformation

28
New cards

How do channel proteins facilitate diffusion?

form hydrophilic transmembrane channels to provide a passage route for solutes

29
New cards

What are the 3 kinds of transmembrane protein channels that channel proteins form?

ion channels, porins, aquaporins

30
New cards

What are ion channels?

most of the smaller channels involved in ion transport

31
New cards

Is transport by carrier proteins faster than movement of solutes through ion channels?

no

32
New cards

Why are movements of solutes through ion channels faster than transport by carrier proteins?

because a conformation change is not required

33
New cards

What are porin channels?

large and nonspecific pores formed by transmembrane proteins called porins

34
New cards

What are examples of porin channels?

the pores on the outer membranes of bacteria, mitochondria, and chloroplasts

35
New cards

What molecular weight of solutes can pass through porin channels?

600 daltons

36
New cards

What are the characteristics of other channels besides porin channels?

small and highly selective

37
New cards

What are aquaporin channels?

transmembrane channels that allow rapid passage of water

38
New cards

What types of cell membranes do aquaporin allow rapid passage of water through in plants and animals?

animals: erythrocytes and kidney cell membranes

plants: root cells and vacuolar membranes in plants

39
New cards

What is active transport?

the movement of solutes against the concentration gradient using an input of energy (ATP)

40
New cards

What are the 3 major roles of active transport in cells and organelles?

1. uptake of essential nutrients from outside when their concentration is lower than inside the cell

2. export of various molecules from cell or organelle, even when their concentration outside is greater than inside the cell

3. maintenance of constant intracellular concentration of H+,K+,Na+,Ca++

41
New cards

How are active transport mechanisms differentiated?

by the source of energy and whether or not two solutes are transported concomitantly

42
New cards

What is direct active transport?

the accumulation of solute molecules or ions on one side of the membrane is coupled directly to an exergonic chemical reaction (hydrolysis of ATP)

43
New cards

What is indirect active transport?

depends on the cotransport of two solutes, with the movement of one solute down the concentration gradient driving the movement of the other solute up its gradient (can be symport or antiport)

44
New cards

What does direct active transport depend on?

four types of transport ATPases

45
New cards

What are the four types of transport ATPases required for direct active transport?

P-type, V-type, F-type, ABC-type

46
New cards

How do the different types of transport ATPases differ?

by structure, mechanism, location, and roles

47
New cards

How is P-type ATPase (phosphorylation-type) made?

transporter reversibly phosphorylated by ATP as part of the transport mechanism

48
New cards

Where is P-type ATPase located?

plasma membrane

49
New cards

What do P-type ATPase do?

pump H+ and cations (some are flippases)

50
New cards

What are V-type ATPase (vacuole-type)?

integral membrane protein and a peripheral ATPase

51
New cards

What do V-type ATPase do?

pump H+ into organelles such as vacuoles, vsicles, lysosomes, endosomes, and golgi complex

52
New cards

Where are F-type ATPase (factor type) found?

in bacteria, mitochondria, and chloroplasts

53
New cards

What is the purpose of F-type ATPase?

conserving solar energy (photosynthesis) or substrate oxidation (respiration) as ATP

54
New cards

What makes up the ABC-type ATPases (ATP-Binding Cassette)?

a large superfamily of transport proteins that are related to each other in amino acid sequence and molecular mechanism

55
New cards

What do ABC-type ATPases do?

transport a variety of solutes, the solute transported is specific to the particular ABC transporter of the superfamily

56
New cards

How are ABC-type ATPases used in the medical world?

used as antibiotic pumps or other drugs - pump drugs out of the cells making cells resistant to certain drugs

57
New cards

What are multi-drug resistance transport proteins?

involved in resistance of cancer cells to certain chemotherapeutic agents

58
New cards

Where can ABC-type ATPases be found?

in the cytosol