Chapter 5

Question 1

What is membrane asymmetry?

Answer 1

Where proteins and other components of one half of the phospholipid bilayer are different from those that make the other half of the bilayer

Question 2

What are the two pieces of experimental evidence that support the fluid mosaic model of the membrane structure?

Answer 2

Membranes are fluid- experiments where human and rat membrane proteins were mixed
Membrane Asymmetry- freeze fracture technique and electron microscopy used to see the difference in sizes, shape, etc

Question 3

What is the fluid mosaic model of the membrane?

Answer 3

Proposes that membranes are not rigid with molecules locked into place but consist of proteins that move around within a mixture of lipid molecules that has the consistency of olive oil

Question 4

What are lipid molecules?

Answer 4

The foundation or underlying fabric of all biological membranes
Lipid refers to a diverse group of water-insoluble molecules that includes fats

Question 5

What are phospholipids (made of)?

Answer 5

Contains a head group (hydrophilic) that consists of glycerol linked to several typed of alcohols or amino acids by a phosphate group (POLAR)
Contains a tail (hydrophobic) that consists of two long chains of carbon and hydrogen called a fatty acid (NONPOLAR)

Question 6

What does amphipathic mean?

Answer 6

Means the molecule contains a region of hydrophobic (water fearing) and hydrophilic (water loving)

Question 7

What two factors influence the fluidity of the lipid bilayer? Which is more fluid Saturated or unsaturated fats?

Answer 7

1. The type of fatty acids that make up the lipid molecules
2. The temperature

Unsaturated are more fluid since the kink in the carbon bonds prevents them from being squished together

Question 8

How are unsaturated fatty acids formed?

Answer 8

They all start out as saturated fatty acids with no carbon double bonds then desaturases act on these bonds by catalyzing a reaction that removes two hydrogen’s

Question 9

What are sterols?

Answer 9

Act as membrane buffers
Also influence fluidity besides lipids
At high temps they help restrain the movement of lipid molecules which lower the fluidity
EX cholesterol

Question 10

What a re the four major functional categories of membranes?

Answer 10

1. Transport- protein provides hydrophilic channel
2. Enzymatic Activity- a number of enzymes are membrane proteins
3. Signal Transduction- membranes contain receptor proteins that can sense and trigger changes
4. Attachment/recognition- proteins act as attachment points for a range of cytoskeleton elements

Question 11

What are integral membrane proteins?

What are transmembrane proteins?

Answer 11

Proteins embedded into the phospholipid bilayer

Integral membrane proteins that traverse the entire lipid bilayer at least once

Question 12

What is primary structure of proteins?

Answer 12

The amino acid sequence

Question 13

What is the secondary structure of proteins?

Answer 13

The domain that interacts with the lipid bilayer consists predominantly of nonpolar amino acids that collectively form a type of secondary structure
Termed an alpha helix

Question 14

What are peripheral membrane proteins?

Answer 14

Positioned on the surface of a membrane and do not interact with the hydrophobic core of the membrane

Question 15

What is passive transport?

How does the concentration gradient affect the rate of diffusion?

Answer 15

The movement of a substance across a membrane without eh use of ATP
Uses diffusion

Larger the gradient, faster the rate of diffusion

Question 16

What’s the difference between channel proteins and carrier proteins?
What type of channel protein does water use?

Answer 16

Channel- form hydrophilic pathways in the membranes through which molecules can pass
Water uses aquaporins
Carrier- binds a specific solute, such as a sugar molecule or amino acid, and transports it across the lipid bilayer (can only transport one thing so cell can easily determine what’s going in and out)

Question 17

Hypotonic vs hypertonic

Answer 17

Hypo- lower solute concentration relative to something

Hyper- higher solute concentration relative to something

Question 18

What is active transport?

Answer 18

The transport of molecules across a membrane against a concentration gradient that requires the expenditure of energy

Question 19

What are the three main functions of active transport in cells?

Answer 19

1. Uptake of essential nutrients from the fluid surrounding cells even when their concentrations are lower than in cells
2. Removal of secretory or waste materials from cells when the concentration of those materials is higher outside the cell
3. Maintenance of essentially constant intracellular concentrations of H+, Na+, K+, Ca2+

Question 20

What’s the difference between primary active transport and secondary active transport?

Answer 20

Primary- the same protein that transports the molecules also hydrolyzes ATP to power the transport directly. Always pump more positively charged ions
Secondary- the transport is indirectly driven by ATP

Question 21

What is a membrane potential?

Answer 21

The voltage across a membrane

Question 22

What is an electrochemical gradient?

Answer 22

They Store energy that is used for other transport mechanisms

Question 23

What’s the difference between symport and antiport? In active transport

Answer 23

Symport- cotransported solute moves through the membrane channel in the same direction as the driving ion (cotransport)
Antiport- the driving ion moves through the membrane channel in one direction, providing energy for the active transport of another molecule in opposite direction (exchange diffusion)

Question 24

What’s the difference between bulk-phase endocytosis and receptor-mediated endocytosis?

Answer 24

Bulk-phase- extracellular water is taken in as well as any other molecules in the solution (simpler)
Receptor-mediated- the molecules to be taken in are bound to the outer cell surface by receptor proteins

Question 25

What are the three steps that most signal pathways involve?

Answer 25

1. Reception- the binding of a signal molecule with a specific receptor of target cells
2. Transduction- the process whereby signal reception triggers other changes within the cell necessary to cause the cellular response
3. Response- the transduction signal causes a specific cellular response

Question 26

What are signal molecule mimics?

Answer 26

Unrelated molecules that mimic the structure of the normal extracellular signal molecule

Question 27

What is protein kinases?

Answer 27

Enzymes that transfer a phosphate group from ATP to one or more sites on particular proteins

Question 28

What is a phosphorylation cascade?

Answer 28

When protein kinases act in a chain catalyzing a series of phosphorylation

Question 29

What are protein phosphatases?

Answer 29

These balance or reverse the effects of protein kinases in the signal transduction by removing the phosphate groups from target proteins

Question 30

What is amplification in signal transduction?

Answer 30

An increase in the magnitude of each step as a signal transduction pathway proceeds