3.3

Question 1

What is carrier-mediated facilitated diffusion?

Answer 1

a carrier moves a solute down its concentration gradient across the plasma membrane. Since this is a passive process, no cellular energy is required.

Question 2

What are the two processes of transportation across the plasma membrane?

Answer 2

passive and active processes

Question 3

What is passive process?

Answer 3

a substance moves down its concentration or electrical gradient to cross the membrane using only its own kinetic energy (energy of motion)

Question 4

What is active process?

Answer 4

cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient. The cellular energy used is usually in the form of adenosine triphosphate (ATP).

Question 5

What are vesicles?

Answer 5

Another way that some substances may enter and leave cells is an active process in which tiny, spherical membrane sacs referred to as vesicles are used. Examples include endocytosis and exocytosis.

Question 6

What are the several factors that influence diffusion?

Answer 6

Steepness of the concentration gradient, temperature, mass of the diffusing substance, surface area, diffusion distance.

Question 7

What is simple diffusion? What molecules go through simple diffusion?

Answer 7

a passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins. Nonpolar, hydrophobic molecules move across the lipid bilayer through the process of simple diffusion.

Question 8

What is facilitated diffusion?

Answer 8

Solutes that are too polar or highly charged to move through the lipid bilayer by simple diffusion can cross the plasma membrane by a passive process called facilitated diffusion.

Question 9

What is channel-mediated facilitated diffusion?

Answer 9

a solute moves down its concentration gradient across the lipid bilayer through a membrane. Most membrane channels are ion channels, integral transmembrane proteins that allow passage of small, inorganic ions that are too hydrophilic to penetrate the non polar interior of the lipid bilayer.

Question 10

Is the concentration of K+ higher in extracellular fluid or cytosol?

Answer 10

The concentration of K+ is higher in the cytosol of body cells than in extracellular fluids.

Question 11

How does glucose enter the body cells?

Answer 11

Glucose, the body’s preferred energy source for making ATP, enters may body cells by carrier-mediated facilitated diffusion as follows

1. Glucose binds to a specific type of carrier protein called the glucose transporter (GluT) not the outside surface of the membrane.
2. As the transporter undergoes a change in shape, glucose passes through the membrane
3. The transporter releases glucose on the other side of the membrane.

Question 12

During osmosis, water molecules pass through a plasma membrane in two ways:

Answer 12

1. by moving between neighbouring phospholipid molecules in the lipid bilayer via simple diffusion
2. by moving through aquaporins, or AQPs, integral membrane proteins that function as water channels.

Question 13

What productions are AQPs responsible for?

Answer 13

cerebrospinal fluid, aqueous humour, tears, sweat, saliva, and the concentration of urine.

Question 14

The higher the solute concentration, …………

Answer 14

the higher the solution’s osmotic pressure.

Question 15

What is tonicity?

Answer 15

A solution’s tonicity is a measure of the solutions ability to change the volume of cells by altering their water content

Question 16

Will a 2% solution of NaCl cause hemolysis or crenation of RBCs? Why?

Answer 16

NaCl will cause crenation because there is more solute concentration at the outside of the RBC than inside.

Question 17

What is active transport?

Answer 17

Active transport is considered an active process because energy is required for carrier proteins to move solutes across the membrane against a concentration gradient.

Question 18

What are the two sources of cellular energy used to drive active transport?

Answer 18

(1) Energy obtained from hydrolysis of adenosine triphosphate (ATP) is the source in primary active transport; (2) energy stored in an ionic concentration gradient is the source in secondary active transport.

Question 19

What is primary active transport?

Answer 19

energy derived from hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against its concentration gradient.

Question 20

What are pumps?

Answer 20

carrier proteins that mediate primary active transport

Question 21

What is secondary active transport?

Answer 21

the energy stored in a Na+ or H+ concentration gradient is used to drive other substances across the membrane against their own concentration gradients.

Question 22

What are symporters?

Answer 22

These transporters move two substances in the same direction

Question 23

What are antiporters?

Answer 23

Move two substances in opposite directions across the membrane.

Question 24

What is a receptor-mediated endocytosis?

Answer 24

A highly selective type of endocytosis by which cells take up specific ligands.

Question 25

What are the three types of endocytosis?

Answer 25

Receptor-mediated endocytosis, phagocytosis, bulk-phase endocytosis.

Question 26

Receptor-mediated endocytosis of LDLs occurs as follows:

Answer 26

Binding, vesicle formation, uncoating, fusion with endosome, recycling of receptors to plasma membrane, degradation in lysosomes.

Question 27

What are phagocytosis?

Answer 27

a form of endocytosis in which the cell engulfs large solid particles, such as worn-out cells, whole bacteria, or viruses

Question 28

What are phagocytes?

Answer 28

Body cells, termed phagocytes, are able to carry out phagocytosis

Question 29

What are pseudopods?

Answer 29

Phagocytosis begins when the particle binds to a plasma membrane receptor on the phagocyte, causing it to extend pseudopods, projections of its plasma membrane and cytoplasm.