Lect Chapter 3b

Question 1

Two major active membrane transport processes

Answer 1

Active transport and vesicular transport

Question 2

What characteristics must a solute have for active and vesicular transport (requiring ATP to move solutes across the plasma membrane)?

Answer 2

• If the solute is too large for channels
• if the solute is not lipid soluble
• if the solute is not able to move down the concentration gradient

Question 3

In active transport carrier proteins are required ( solute pumps). What do they do and what are two types?

Answer 3

Carrier proteins bind specifically and reversibly with substance being moved two types are
– anti porters
-symporters

Question 4

What do antiporters and symporters transport?

Answer 4

Antiporters transport one substance into a cell while transporting a different substance out of the cell.
Symporters Transport two different substances in the same direction.

Question 5

What are two types of active transport? What are the difference s?

Answer 5

Primary active transport where the energy comes directly from ATP hydrolysis and

secondary active transport where the energy comes indirectly from ionic gradients created by primary active transport.

Question 6

Active transport moves solutes against their concentration gradient (from low to high) requiring energy. True or false

Answer 6

True

Question 7

How does primary active transport happen?

Answer 7

Energy from ATP hydrolysis causes a change in the shape of a transport protein this shape change causes solute’s (ions) bound to protein to be pumped across membrane.

Question 8

Explain the sodium potassium pump.

Answer 8

• leakage channels located in membranes result in leaking of sodium into the cell and leaking of potassium out of the cell both traveling down there concentration gradient.
• The sodium potassium pump is basically an enzyme called sodium potassium ATPase Which works as an antiporter and pumps sodium out of the cell and potassium back into the cell
• this is located in all plasma membrane’s but especially active in excitable cells like nerves and muscles
• this maintains the electrochemical gradient’s, which involve both concentration an electrical charge of ions.

Question 9

How is secondary active transport driven and explain its function

Answer 9

Secondary active transport depends on the ion gradient that was created by the primary active transport.
- The low sodium concentration inside of the cell due to the sodium potassium pump strengthens the sodium drive to want to enter the cell.
-As sodium enters the cell Do to diffusion along its concentration gradient It can drag other molecules with it via carrier proteins (usually symporter’s)
Sugars amino acids and ions usually transported in the cell via secondary active transport

Question 10

What is vesicular transport? Where does it usually get the energy?

Answer 10

• involves transport of large particles, macromolecules, and the fluids across membrane in membrane is sacs called vesicles
• RequiresCellular energy ATP

Question 11

What are the four transport processes in vesicular transport?briefly explain each

Answer 11

Endocytosis - transport into the cell
Exocytosis - Transport out of the cell
Transcytosis - Transport into across and then out of the cell
Vesicular trafficking - transport from one area or organelle in cell to another.

Question 12

What is endocytosis and the three types?

Answer 12

Protein coated vesicles are pulled into the cell. Receptors selectively pull a substance into the cell that binds to the unique receptor.
It does this three ways phagocytosis, pinocytosis, receptor mediated endocytosis.

Question 13

Explain phagocytosis

Answer 13

• cell eating
• pseudopods (membrane projections) flow and form around solid particles that are being engulfed, forming a vesicle which is pulled into the cell
• The New vesicle is called a phagosome.
• phagocytosis used by white blood cells
• they have an amoeboid motion

Question 14

Explain pinocytosis

Answer 14

• cell drinking or fluid phase endocytosis
• Plasma membrane infolds, gulps /bringing extracellular fluid and dissolved solute’s inside cell. Again forming a vesicle.
• Used by some cells to sample Environment
• Mainway nutrient absorption happens in the small intestine
• Membrane components are recycled back to the membrane

Question 15

Explain receptor mediated endocytosis

Answer 15

• Clathrin coated pits embedded with receptors bond with specific molecules and become internalized again as vesicles with the molecule bound to those receptors.
• this can be in endocytosis and transcytosis

Question 16

Explain What is exocytosis?

Answer 16

• Process for material is ejected from the cell
• substances to be ejected are in a secretory vesicle
• that Vesicle Has a V snare protein which attaches to a T snare Protein on the plasma membrane
• They bind and the vesicle and plasma membrane fuse causing a pore to open up and releasing the vesicle contents to the cell exterior

Question 17

What is voltage

Answer 17

The difference in electrical charge between two points.

Question 18

What is resting membrane potential (RMP) and where does the voltage only occur?

Answer 18

RMP is electrical potential energy produced by separation of of oppositely charged particles across the plasma membrane in all cells.
- The voltage occurs only at the membrane surface

Question 19

What is the range of voltages on the membrane, why is it written that way, what is the rest of the cell and extracellular fluid charge

Answer 19

Membrane voltage is range from -52 to -100 MV
The negative sign indicates inside of cell is more negative relative to the outside of the cell
Rest of the cell is neutral

Question 20

What is the key player in RMP And explain how this causes RMP

Answer 20

• K+ defuses out of the cell through K+ leakage channels along the concentration gradient
• This results in the cytoplasmic side of the cell membrane to be more negative because negative charged proteins cannot leave
• The negative interior pulls the positive K+ back in because of its electrical gradient
• when the drive for K+ to leave the cell is balance by the drive to stay, RMP is established
• electrochemical gradient of K+ sets RMP

Question 21

What effect if any does Na+ and CL- Have on the RMP?

Answer 21

• Sodium is also attracted into the cell because of the negative charge and can bring the RMP up to -70 MV but K + is more permeable which is why it’s the primary influence on RMP
• chlorine does not influence RMP because it’s concentration and electrical gradients are exactly balanced

Question 22

How Active transport maintain electrochemical gradient?

Answer 22

• RMP is maintained through sodium potassium pump always ejects three sodium + out of cell and brings to potassium + back in
• steady state is maintained because the rate of the active pumping of sodium+ out of the cell is equal to the rate of sodium+ diffusion into the cell

Question 23

What types of cells will upset the steady state of RMP and how?

Answer 23

Neurons and muscle cells do this by intentionally opening gated sodium+ and potassium + channels

Question 24

What are examples of ligand? What are they

Answer 24

Ligands are chemical messengers examples are neurotransmitters hormones and paracrines.

Question 25

Cell interaction with environment always involves what two things? And what are the sticky proteins called

Answer 25

Sticky proteins are glycocalyx and they are either

• cell adhesion molecules ( CAMs) and
• plasma membrane receptors

Question 26

How does a cell interact with it’s environment indirectly and explain it using the five players involved?

Answer 26

The five players involved are ligands (First messenger)
Receptor
G protein
Enzyme
Second messenger
-ligand outside of the cell (extracellular fluid) binds to a receptor protein embedded in the plasma membrane which changes its shape
- This shape change activates the receptor
-The activated receptor binds to a G protein inside the cell and activates that.
- The G protein changes shape and turns “on“ which causes it to release GDP and bind GTP (energy source)
- The activated G protein either turns on or turns off an effector protein By causing it’s shape to change
- The activated effector enzymes, Catalase reactions that produce second messengers inside the cell
- Second messengers activate other enzymes or ion channels typically activates protein kinase enzymes
- Chinese enzymes activate other enzymes transferring phosphate groups from ATP to specific proteins and activate a series of other enzymes that trigger various metabolic and structural changes in the cell