5.2 The plasma membrane and cell wall

Question 1

What make up the plasma membrane?

Answer 1

phospholipids and embedded proteins

Question 2

What is the plasma membrane?

Answer 2

A fundamental, defining feature of all cells. The boundary that defines the space of the cell, separates internal contents from the surrounding environment.

Question 3

What is a cell wall?

Answer 3

external to the plasma membrane, helps maintain the structure of the cell and protects. made up of carbohydrates and proteins

Question 4

How does the cell maintain homeostasis?

Answer 4

the plasma membrane is semi permeable (lets certain molecules in, lets others in under certain conditions, or prevents molecules) requires a lot of energy

Question 5

How is the plasma membrane selectively permeable?

Answer 5

results from a combination of lipids and embedded proteins.

• hydrophobic interior prevents ions and charged or polar molecules from diffusing freely.
• some macromolecules and proteins are too big to cross PM

Question 6

which molecules can freely. one across the plasma membrane?

Answer 6

gases, lipids and small polar molecules.

Question 7

what is the purpose of protein transporters in the membrane?

Answer 7

allow the export and import of molecules including ions, and neutrons that cannot cross the cell membrane on their own.

Question 8

what is the simplest form of movement in and out of the cell and how does it work?

Answer 8

Passive transport and it works by diffusion

Question 9

how does diffusion work?

Answer 9

a network of movement of a substance through a concentration gradient of high to low.

Question 10

what is the process when a molecule moves by diffusion through a membrane protein and bypasses the lipid bilayer

Answer 10

facilitated diffusion

Question 11

What is the difference between facilitated and simple diffusion?

Answer 11

facilitated diffusion
-the molecule moves through a membrane transporter
simple diffusion (requires no help)
-molecule moves directly through lipid bilayer

Question 12

What are the two types of membrane transporters?

Answer 12

channel and carrier

Question 13

what is a channel protein

Answer 13

provides an opening between inside and outside cell.

some are gated (open in response to a signal)

Question 14

what is a carrier protein

Answer 14

binds to and transports specific molecules.

Question 15

what is the purpose of aquaporins?

Answer 15

specific protein channels that allow water to move more readily across the PM by facilitated diffusion.

• right shape
• polar attracts polar

Question 16

what is the definition of osmosis?

Answer 16

the net movement of a solvent, such as water across a selectively permeable membrane toward the side of higher solute concentration

Question 17

What is active transport?

Answer 17

The uphill (low to high) movement of substances across the plasma membrane, required ATP energy

Question 18

how does the sodium potassium pump work?

Answer 18

actively moves 3 sodium out of cell and 1 potassium into the cell

Question 19

what is primary active transport?

Answer 19

active transport that uses the energy of ATP directly (sodium potassium pump)

Question 20

what is an antiporter?

Answer 20

when molecules are moved in and out of the cell along a protein electrochemical gradient in opposite direction.

Question 21

what are the 3 steps in secondary active transport?

Answer 21

1. protons pumped across membrane by primary active transport
2. protein pump generates electrochemical gradient (higher concentration of protons outside the cell, lower concentration of protons inside the cell)
3. antiporter uses proton electrochemical gradient to move different molecules out of cell against conc. grad.

Question 22

How does a pump generate a concentration gradient?

Answer 22

actively pumping protons (H+) out of the cell.

Question 23

What is an electrochemical gradient

Answer 23

a gradient that has both charged and chemical. components (protons crossing membrane)

Question 24

When is active transport secondary

Answer 24

when the movement of protons in from high to low and movement of coupled molecules is from low to high. the movement of coupled molecule is derived from protons and not ATP directly the process is then secondary.

Question 25

What is secondary active transport

Answer 25

uses potential energy of an electrochemical gradient to drive the movement of molecules.

Question 26

what is the definition for hypotonic, hypertonic and isotonic?

Answer 26

hypotonic- lower solute concentration then that inside the cell
hypertonic- higher solute concentration then that inside the cell
isotonic- same solute concentration then that in the cell

Question 27

what is a vacuole?

Answer 27

a cell structure that absorbed water and contributes to turgor pressure (plant cells)