Midterm 1-6

Question 0

How is the protein arranged in the membrane

Answer 0

Amino acid r groups vary in their affinity for water. Non polar amino acids are stable in membranes due to hydrophobic interactions with hydrocarbon tails and polar or charged amino acids are stable next to the polar heads in the surrounding water

Question 1

Can amphipathic proteins be added to the lipid bilayer

Answer 1

Yes

Question 2

What do cell membranes containe

Answer 2

Both proteins and phospholipids. Proteins come in varying shapes and sizes, some form channels or pores

Question 3

What is the fluid mosaic model

Answer 3

A model that suggest many proteins are inserted within the lipid bilayer, making the membrane a fluid dynamic mosaic of phospholipids and proteins

Question 4

What are membrane spanning protein

Answer 4

Integral membrane proteins or transmembrane proteins

Question 5

What are peripheral membrane proteins

Answer 5

Proteins that are located on the membrane surface and often attached to integral membrane proteins

Question 6

Why are detergents used

Answer 6

To separate integral membrane proteins

Question 7

How do detergents work

Answer 7

They have short hydrophobic tails that interact with membrane phospholipid tails, breaking apart the bilayer. Detergents then surround hydrophobic parts of membrane proteins, forming water soluble detergent protein complexes

Question 8

How do ions cross through the bilayer

Answer 8

Ions move from areas of like charges to areas of unlike charges and from areas of high concentration to areas in low concentration. It is in response to the electrochemical gradient. Their charge doesn’t allow them to pass through phospholipid bilayers

Question 9

What is the function of CFTR

Answer 9

A chloride channel that helps with cystic fibrosis. Without it, no current would flow with the ions

Question 10

How do ions cross through the bilayer

Answer 10

They cross through proteins called ion channels that form tunnels across e bilayer. Because of their charge, they cannot freely move through the lipid bilayer

Question 11

Why do ions move in channels

Answer 11

They move in response to the electron gradient:

Areas of like charges to unlike charges, high concentrations to low concentrations

Question 12

What does the amount of water passed by osmosis dependent on

Answer 12

It depends on the amount of extra cellular ions. Example: defective CFTR prevents Cl- from leaving cells. Thus, less water leaves cells by osmosis and cell secretions are too thick

Question 13

What are channel proteins

Answer 13

This is a type of membrane channel. They are highly selective and only allow only a certain type of ion or molecule to cross through the membrane

Question 14

What are aquaporines

Answer 14

They allow a tenfold in the rate at which water crosses the protein

Question 15

What is the protein tunnel comprised of

Answer 15

This is where hydrophobic r-groups on the exterior side of the protein tunnel interact with membrane hydrocarbon tails,, but the interior is designed with polar amino acid residue that is oriented to specifically interact with water

Question 16

What are gated channels

Answer 16

An example would be aquaporines and other ion channels that only open when a specific molecule binds to the protein, or it is in the presence of a specific electric charge

Question 17

How does k+ pass through the membrane

Answer 17

This passes through a specific potassium channel. They pass through when the inside of the cell, relative to the outside, has a positive charge causing the cell to change shape and open up

Question 18

What do channels allow membranes to do?

Answer 18

Channels allow membranes to have some control over the transmembrane flow of the molecules or ions. It also creates a mechanism to allow small charged molecules

Question 19

What is passive transport?

Answer 19

Facilitated diffusion. When substance diffuse down their electrochemical gradient. There is no need for an energy input (spontaneous)

Question 20

What are carrier proteins

Answer 20

These are the proteins that change the shape of the membrane to allow molecules to pass through or ions (it facilitates diffusion). These proteins work to reduce differences between the outside and inside of a cell vesicle.

Question 21

Why is glucose important

Answer 21

Glucose is an energy source and a subunit for important macromolecules, although the lipid bilayers are not very permeable to glucose

Question 22

How does GLUT-1 work

Answer 22

It is hypothesized that glucose binds to GLUT-1 that causes the shape of the protein to change that transports the glucose through the membrane. It aids diffusion down a down a concentration gradient(if glucose concentrations were similar on interior and exterior the there would be no movement)

Question 23

What is active transport

Answer 23

This is transportation of ions or molecules against the concentration gradient which requires a large input of energy. This is called a pump.

Question 24

What can power active transport

Answer 24

Adenosine triphosphate (ATP) because it leaves a phosphate group that binds to the pump. The negative energy interacts with the protein causing the protein to change shape and increase in potential energy. It interacts with the pump of the amino acids

Question 25

What is the sodium potassium pump

Answer 25

Na+\K+_ATPase, this uses energy from the ATP phosphate to allow for the transfer of potassium ions and sodium ions. This is due to the immediate shape change when the phosphate group is attached to the protein.

Question 26

How does the sodium phosphate pump work

Answer 26

three Na+ ions attaché themselves to the inside of the cell. Then a phosphate from ATP binds to the protein causing the shape to change and making the sodium ions leave. This opening allows two potassium ions to attach themselves to the protein and once the phosphate detaches from the protein, the potassium ions are released into the cell

Question 27

How do other pumps work

Answer 27

Other pumps move other ions or molecules across the cell membrane against the electrical gradient and concentration

Question 28

How does sodium potassium pump create a chemical and electrical gradient

Answer 28

This is due to the fact at it return two positive potassium ions for three sodium ions.

Question 29

What is secondary active transport

Answer 29

The energy used from the stored energy of the chemical/electrical gradient. This energy is used to move other molecules affected by the gradient (also known as cotransport

Question 30

Give an example of secondary active transport

Answer 30

Gut cells bring glucose cells along with sodium ions. The energy in the sodium ion gradient that is created by the sodium phosphate pump powers glucose transport against a concentration gradient (glucose concentration is higher in the cell.