Bio 156 Chapter 5A, part 1

Which of the following can move across membranes by diffusion?

- carbon dioxide - water - oxygen - all of the above

Which of the following can move across membranes by passive transport?

- oxygen - carbon dioxide - water - all of the above

Which of the following is a function of membrane proteins?

- some proteins function as receptors for chemical messengers from other cells - some proteins are enzymes involved in catalytic reactions - some proteins are involved in transport, and help move substances across the membrane - some proteins are receptors involved in signal transduction - all of the above

facilitated diffusion.

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

phagocytosis

A white blood cell engulfing a bacterium is an example of _____.

exocytosis

A white blood cell is capable of producing and releasing thousands of antibody molecules every second. Antibodies are large, complex protein molecules. How would you expect them to leave the cell?

Do fish drink?

Although freshwater fish do not drink, saltwater fish must drink because they lose too much water through their gills.

Why are they called "reverse osmosis filters?"

Because high pressure is used to push water through a filter, against the concentration gradient.

Which of the following is NOT a true statement about diffusion?

Diffusion occurs when particles spread from areas of low concentration to areas of high concentration.

Exocytosis

If a large hormone molecule is produced inside a cell, the hormone can be released out into the extracellular environment by:

hypertonic

If the solution outside of a cell has a greater concentration of solutes than the solution inside the cell, the solution outside the cell is ___ in relation to the cell.

Hypotonic

If the solution outside of a cell has a lower concentration of solutes than the solution inside the cell, the solution outside the cell is ___ in relation to the cell.

isotonic

If the solutions both inside and outside of a cell have an equal concentration of solutes, the solution outside the cell is ___ in relation to the cell.

a hypotonic

In a plant cell, if there is a net inflow of water keeping pressure exerted against the inside of the cell wall, the cell must be in ___ environment.

Why does jelly last so long in the frig?

Jelly contains so much sugar that it creates a hypertonic environment, inhibiting the growth of bacteria and mold.

freshwater lakes and ponds.

Paramecium is a genus of protists that lives in water. It has organelles called contractile vacuoles that continually eliminate the excess water gained through osmosis. Knowing that Paramecia gain water through osmosis, we can deduce that they normally live in

Why might a salty laxative help relieve constipation?

Salty laxatives in the large intestine help pull water out of cells and into the intestine by osmosis, thereby relieving constipation.

hypotonic

Some protists (like Paramecium) have special organelles called ontractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment is ___ to the protist.

Exocytosis

The export of macromolecules out of the cell by means of a membrane-enclosed vesicle moving to the plasma membrane is called:

diffusion

The movement of molecules from higher concentration to lower concentration is called:

osmosis

What name is given to the process by which water crosses a selectively permeable membrane?

animals

What type of organism has cholesterol in it's membranes?

active transport

Which of these processes can move a solute against its concentration gradient?

active transport

Which of these processes requires energy?

If you are going to bake potatoes, and your potatoes are soft and dehydrated, they can be soaked in __________ to make them more firm before baking.

a hypotonic solution such as tap water

In facilitated diffusion, a molecule cannot cross a biological membrane unless ___ is present.

a transport protein

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of

active transport

Which of the following is a difference between active transport and facilitated diffusion?

active transport requires energy from ATP and facilitated diffusion does not

When diffusion across a membrane stops because a state of dynamic equilibrium is reached, it means that:

an equal number of molecules are moving in and out, so there is no net movement.

A cell that neither gains nor loses water while sitting in a solution is probably sitting in

an isotonic environment.

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

endocytosis.

Which of the following requires specific transport proteins?

facilitated diffusion and active transport

Which of the following best describes the plasma membrane?

fluid mosaic

Which of the following function as cell identification tags that can be recognized by other cells?

glycoproteins and glycolipids

What is the role of cholesterol molecules that are embedded in the membranes of some living things?

help stabilize the phospholipids at body temperature

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

In a hypertonic environment, a plant cell will:

lose the water from the central vacuole, and the cell membrane will pull away from the cell wall

A human cell placed into a hypertonic solution is likely to

lose water by osmosis

In active transport,

molecules move across the plasma membrane against their concentration gradient.

What type of molecules pass most easily through plasma membranes?

nonpolar molecules because they are soluble in lipids

If the salt concentration inside a cell is 0.9%, and the salt concentration outside a cell is 9%, in which direction will there be a net movement of water by diffusion?

out of the cell

Facilitated diffusion is a type of _____.

passive transport

Which type of molecule is the main component of cell membranes?

phospholipids

Which of the following describes a phospholipid molecule?

polar head, hydrophobic tail

Sodium ions require energy to move across a plasma membrane. The movement of sodium ions across a membrane:

requires a transport protein

In an aqueous environment, phospholipids tend to organize into a bilayer because the formation of a bilayer:

shields the hydrophobic tails from water.

When a person is dehydrated, his or her IV fluids

should be isotonic, because either a hypertonic or hypotonic IV would damage red blood cells.

What does it mean if the plasma membrane exhibits selective permeability?

some substances can cross the membrane more easily than other substances

A human cell placed in a hypotonic environment would

take up water through osmosis.

Many bacteria and fungi have a difficult time surviving on our food if the food is very salty. The best explanation for this is

that the salt in the food creates a hypertonic environment for the bacteria and fungi.

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

Which of the following will happen to an animal cell if placed in a hypotonic environment?

the cell will become larger, and may burst

What is osmoregulation?

the control of water balance

If a cell is in equilibrium with its environment:

the environment is probably isotonic to the cell

Which of the following has the greatest effect on the ability of polar molecules to pass through membranes?

the protein carriers that are present in the membrane

If placed in distilled water, an animal cell will burst, whereas a plant cell will not. What accounts for this difference?

the relative inelasticity and strength of the plant cell wall

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

the similarity of the drug molecule to other molecules that are transported into the target cells

Water crosses the plasma membrane

through facilitated diffusion or diffusion.

Facilitated diffusion across a biological membrane requires ___, and moves a substance from ___ concentration.

transport proteins; high to low