module 9

Question 1

8 common Membrane characteristics

Answer 1

1) Membranes are sheet-like structures, two molecules thick, that form closed boundaries between compartments.

2) Membranes consist of mainly of lipids and proteins, with carbohydrates linked to these molecules.

3) Membranes are built from amphipathic molecules.

4) Membranes are largely impermeable to polar molecules.

5) Specific membrane proteins mediate biological functions.

6) Membranes are self-assembling, non-covalent structures.

7) Membranes are fluid and dynamic structures.

8) Membranes are highly specialized in their composition and distribution (asymmetric).

Question 2

Membrane formation is a consequence of the __________ nature of the membrane lipids.

Answer 2

-amphipathic

Question 3

Lipid bilayer membranes have _______ permeability to ions and polar
molecules.

Answer 3

-Low

Question 4

What is the fluid mosaic model?

Answer 4

A model that shows lipids and proteins freely diffuse freely and rapidly in the plane of the membrane.

Question 5

Transbilayer Movement Requires _________

Answer 5

-A catalyst

Question 6

Translocation of lipids from one side
of bilayer to the other is catalyzed by
enzymes called _________.

Answer 6

-Flippases

Question 7

Specialization of Membrane Structure and
Function:

Answer 7

• Composition of Membrane Components
• Lipids & Proteins
• Distribution of Membrane Components
• Static & Dynamic
• Specialized Membrane Regions
• Lipid Rafts

Question 8

What are lipid rafts?

Answer 8

Lipid rafts spontaneously arise from the
association of lipid molecules whose
hydrocarbon tails are of similar length.

Question 9

What are the 3 membrane protein categories?

Answer 9

• Peripheral (c and d)
• Lipid-anchored (e)
• Integral membrane proteins (a and b)

Question 10

Peripheral membrane proteins Associate with membrane through ____________ or _________-__________ interactions.

Answer 10

electrostatic or hydrogen-bonding

Question 11

What are lipid anchored membrane proteins?

Answer 11

A protein with a hydrocarbon tail that attach to the surface of the membrane.

Question 12

What are integral membrane proteins?

Answer 12

• Integral membrane proteins are immersed in, and usually span, the membrane.
• Protein positioning within a membrane is specific and directional.
• Integral membrane proteins tend to be of three varieties; single pass helical, alpha helical bundles, and barrels.

Question 13

Membrane spanning regions can be predicted from primary structure. T or F?

Answer 13

True

Question 14

Side chains within the transmembrane region tend to be polar. T or F?

Answer 14

False, they tend to be non-polar (hydrophobic)

Question 15

What are the Categories of Membrane
Transport?

Answer 15

1) Simple Diffusion

2) Facilitated Diffusion
-Carriers
-Channels

3) Active Transport
-Primary
-Secondary

4) Ion Transporters

Question 16

What is simple diffusion?

Answer 16

Non-polar gases (O2 and CO2) and
hydrophobic molecules can cross
directly through the membrane.

Question 17

What is facilitated diffusion?

Answer 17

Membrane transporters lower the
activation energy for crossing the membrane by replacing the hydration shell with interactions with polar groups along the transfer path in the protein interior.

Question 18

What are the 2 different varieties of facilitated diffusion?

Answer 18

Channels and carriers

Question 19

What are the difference between the 2 facilitated diffusions?

Answer 19

Channels:
* Membrane pores to transport molecules down concentration gradient.
* High conductance rates because they bind the substrate very weakly.
* Do not saturate.

Carriers:
* Membrane proteins that undergo substrate-induced conformational change, or membrane repositioning, to release substrate to the other side of the membrane.
* Slower because they bind the substrate quite strongly.
* Can saturate.

Question 20

Transport of a single molecule is called uniport. T or F?

Answer 20

True

Question 21

What are the 2 coupled transporters called and which direction do they go in?

Answer 21

-Antiporters move molecules in opposite directions.
-Symporters move molecules in the same direction.

Question 22

In diffusion, co transport depends on what molecules?

Answer 22

In diffusion, co-transport through antiport or symport depends on the charge of the molecules in order to have a net neutral change.

Question 23

Primary vs secondary active transport differences.

Answer 23

Primary Active Transport
* driven by direct source of energy (ATP)
* Includes P-type, V-type, and ABC Transporters

Secondary Active Transport
* couples the movement of one molecule down its concentration gradient to the movement of a second molecule down its gradient.

Question 24

P-type transporters

Answer 24

This gradient controls cell volume,
electrical excitability, and enables uptake
of nutrients through secondary active
transport systems.

Question 25

V-type and ABC transporters

Answer 25

V-type ATPases - Use the energy of ATP to move protons against a concentration gradient. - acidification of organelles. - Chloroplasts and mitochondria reverse this reaction using proton gradients to generate ATP. ABC Transporters * ATP-binding domains (ATP-Binding Cassette) * Transport of a variety of biomolecules out of the cell against a concentration gradient. * Multi-drug resistance protein pumps drugs out of the cell rendering the drugs ineffective.

Question 26

F-type transporters

Answer 26

In chloroplasts and mitochondria, F-type ATP synthase uses proton gradients to generate ATP.

Question 27

What do Ion channels do?

Answer 27

Ion channels enable rapid movement of ions across the membrane.

Question 28

Ion channels differ from ion transporters (like the Na+,K+ATPase) in three ways:

Answer 28

1) Faster 2) No saturation limits 3) Gated/Regulated (open and close in response to signal)

Question 29

Specificity of Ion Channels (K+ Channel)

Answer 29

K+ channel allows rapid movement of K+ ions out of cell. * Although Na is smaller, the channel is 100-fold more permeable to K+.

Question 30

wat small non polar gases can pass directly through the cell membrane.

Answer 30

-O2 and CO2

Question 31

Bacteria grown at a higher temperature would tend to have higher or lower amounts of saturated fatty acids?

Answer 31

As the temperature increase there tends to be an increase in saturated fatty acids.

Question 32

what is the Composition of Membrane Components?

Answer 32

-Lipids and proteins

Question 33

Name a specialized region in the cell membrane

Answer 33

-Lipid rafts

Question 34

Whats an example of facilitated diffusion through a carrier?

Answer 34

Glucose permease of the red blood cells. Glucose binds to a carrier and brings in the glucose into the red blood cell.

Question 35

What is an example of primary active transport?

Answer 35

Na+,K+ ATPase uses the energy of ATP hydrolysis to pump three Na+ out of the cell and two K+ into the cell.

Question 36

What is an example of secondary active transport?

Answer 36

In intestinal epithelial cells, glucose uptake from the gut is driven through symport with Na+.

Question 37

Which is an example of symport? -Glucose uptake into red blood cells. - ABC transporters. -Na K ATPase. -None of these are examples of symport. -Glucose uptake into intestinal epithelial cells.

Answer 37

-Glucose uptake into intestinal epithelial cells.

Question 38

Which modification of the hydrocarbon tails of membrane lipids would help bacteria adapt to higher temperatures? -Decreased length, increased number of double bonds. - Increased length, decreased number of double bonds. - cut-off jeans and a cool drink -Decreased length, decreased number of double bonds. - Increased length, increased number of double bonds.

Answer 38

-Increased length, decrease number of double bonds.

Question 39

The fluid mosaic model refers to: -the freedom of movement of membrane proteins and lipids within the plane of the membrane. -the ability of membrane proteins to spontaneously change their orientation across the plane of the membrane. -changing the composition of membranes in response to changing conditions. -passive diffusion of gases through the membrane. -maintaining the membrane at the phase transition point.

Answer 39

-The freedom of movement of membrane proteins and lipids within the plane of the membrane.

Question 40

Which of the following is an example of secondary active transport? -Glucose uptake into intestinal epithelial cells. -ABC transporters. -None of the answers are correct. -Na K ATPase. -Glucose uptake into red blood cells.

Answer 40

-Glucose uptake into intestinal epithelial cells.

Question 41

The primary difference between primary and secondary active transport is: -Whether molecules can be transported against a concentration gradient. -Source of energy driving transport. - Specificity of molecules to be transported. -Speed of transport. -The direction of transport of the transported molecules.

Answer 41

-Source of energy driving transport

Question 42

Integral membrane proteins: -can differ in the number of transmembrane regions they contain. - can differ in the types of secondary structure within the membrane-spanning region. - have membrane-spanning regions that are enriched in non-polar residues. -All of the answers are correct. - can be predicted from primary structure.

Answer 42

-All of the answers are correct.

Question 43

Specialization within biological membranes can include: -different faces of a membrane having unique membrane component compositions. - changing the protein composition of a membrane in response to changing conditions. -All of the answers are correct. - formation of lipid rafts. - different organelles having unique membrane component compositions.

Answer 43

-All of the answers are correct

Question 44

Uptake of glucose into intestinal epithelial cells is an example of: - Simple diffusion. - Secondary active transport. - Facilitated diffusion through a channel. - Primary active transport. -Facilitated diffusion through a carrier.

Answer 44

-Secondary active transport.

Question 45

Which statement about lipid-linked proteins is FALSE? -GPI anchors are associated with extracellular lipid-linked proteins. -Lipid anchors bury themselves in the hydrophobic core of the protein. - The attachment of the lipid anchors is reversible. -Intracellular lipid-linked proteins have specialization of the types of hydrocarbon tails that are attached. -Intracellular lipid-linked proteins have specialization of the points of attachment of the hydrocarbon tails.

Answer 45

-Lipid anchors bury themselves in the hydrophobic core of the protein. -Instead, they insert into the hydrophobic core of the lipid bilayer (membrane)

Question 46

Facilitated diffusion through carriers and channels differ in that: - Channels are slower and do not saturate. -Carriers are slower and do not saturate. -Channels are slower and saturate. -Carriers are slower and saturate.

Answer 46

-Carriers are slower and saturate

Question 47

Discuss the difference in uptake of glucose into red blood cells and intestinal epithelial cells.

Answer 47

-The uptake of glucose into red blood cells occurs through facilitated diffusion through a carrier. - The uptake of glucose into intestinal epithelial cells through secondary active transport where glucose is co-transported into the cells against its concentration gradient with Na+.

Question 48

Discuss the mechanisms for predicting integral membrane proteins.

Answer 48

-Prediction of integral membrane proteins occurs by scanning the primary sequence for stretches of hydrophobic amino acids in a row. (24 hydrophobic residues).