Lab #5 - osmoregulation

Question 1

what is a plasma membrane

Answer 1

the outer limit of the cytoplasm responsible for the regulation of substances moving in and out of a cell

Question 2

what is osmosis

Answer 2

the passive transport of water across a selectively permeable membrane in response o solute concentration gradients, a pressure gradient, or both

Question 3

what is an aquaporin

Answer 3

A specialized protein channel that facilitates diffusion of water through cell membranes

Question 4

what is osmoregulation

Answer 4

a process that regulates the osmotic pressure of fluids and electrolyte balance in organisms

Question 5

isotonic

Answer 5

equal solute concentration inside and outside the cell

Question 6

hypotonic

Answer 6

solution containing dissolved substances at a lower concentration than the cell it surrounds

Question 7

hypertonic

Answer 7

solution containing dissolved substances at higher concentrations that the cell it surrounds

Question 8

what is osmolality

Answer 8

a measure of the osmotic concentration of a solution. It is measure n osmoles (the number of solute molecules and ions) per kilogram of solvent

Question 9

what is a semipermeable membrane?

Answer 9

membrane that only allows certain molecules or ions to pass through it during osmosis

Question 10

what is hemolysis?

Answer 10

the rupturing (lysis) of red blood cells (erythrocytes)

Question 11

what is crenation?

Answer 11

describes the formation of abnormal notched surfaces on cells because of water loss through osmosis.

Question 12

what is a metanephridia?

Answer 12

the execratory tubule of most annelids and mollusks

Question 13

How are animal cells affected when osmolality of extracellular fluid varies?

Answer 13

• Higher osmolality on one side of a selectively permeable membrane is said to be hyperosmotic to a solution of lower osmolality on the other side. When the extracellular fluid has higher osmolality relative to the inside of the cell, the cell will shrink as water moves out of the cell.
• A solution of lower osmolality is said to hypoosmotic to a solution of higher osmolality. When the extracellular fluid has lower osmolality, the cell will get larger as the fluid moves in to the cell.
• If the solutions on either side of a membrane have the same concentration, they are isotonic. The gradient maintains equal movement.
• water moves from areas of low concentration to areas of high concentration

Question 14

What are the features of the plasma membrane in animal cells that underpin its role in osmosis?

Answer 14

• The plasma membrane is a semi-permeable barrier composed of a fluid phospholipid bilayer and proteins
• Water molecules move across a selectively permeable membrane (one that lets water through but excludes most solutes) from a region of lesser solute concentration to a region of greater solute concentration
• It maintains differences in solute concentration on either side of biological membranes

Question 15

Explain the role of osmoregulatory organs in maintaining extracellular fluid composition in vertebrates

Answer 15

• The kidneys regulate the fluid and electrolyte balance of the body by continually filtering the blood. This is vital to maintain a constant extracellular fluid volume and composition.
• To perform this important function they are able to:
  1. excrete or conserve salt and water;
  2. control body pH, and
  3. free the body of waste products of metabolism.
• There are three main processes that enable the kidneys to filter the blood. These are Glomerular filtration, Tubule secretion and Tubular resorption.

Question 16

What is the function of aquaporins? where in the human body are these membrane proteins found?

Answer 16

Aquaporins are integral membrane proteins that serve as channels in the transfer of water, and in some cases, small solutes across the membrane. They are found in blood vessels, kidney proximal convoluted tubules, kidney collecting ducts, the kidney, urinary tract, testis, and liver. Mainly found in epithelial cells

Question 17

Why is it bad for humans to drink sea water?

Answer 17

Seawater contains salt. When humans drink seawater, their cells are thus taking in water and salt. While humans can safely ingest small amounts of salt, the salt content in seawater is much higher than what can be processed by the human body.

Question 18

Describe how osmoregulatory challenges differ between the marine, freshwater and terrestrial environments for vertebrate animals.

Answer 18

a. Aquatic habitats with low solute concentrations, such as fish in fresh water environments of rivers, lakes and ponds (the challenge is to retain enough salt while getting rid of excess water)
b. Aquatic habitats with high solute concentrations, such as seawater fish, as well as marine birds whose only source of water is seawater (the challenge is to retain enough water while getting rid of excess salt)
c. Terrestrial habitats with free access to water
d. Terrestrial habitats with limited access to water, such as in dry areas.