Biology Chapter 5: The Working Cell- Guided Reading Activities

d. When there exists a difference in the amount of a substance across a distance: ____________

d. concentraion gradient

In the following reaction, *star* the enzyme.

*Lactose*--> Gluclose + Galatcose

The relationship between an enzyme's active site and its substrate is most like which of the following?

-A key and a lock

The phosphorylation of ADP creates________.

-ATP

You are sailing on Lake Superior from Copper Harbor, Michigan, to Isle Royale National Park. A sudden storm causes your sailboat to spring a leak. You immediately grab a bucket and begin bailing water out of the boat. Briefly explain how your predicament could be used as an analogy to help explain both active and passive transport.

-If you simply let the water flow into the boat, then water will travel down its concentration gradi-ent (into your boat) until the gradient is abolished (your boat sinks). If you want your boat to stay afloat, then you simply bail water out of the boat. In effect, you are moving water against its con-centration gradient in order to maintain that gradient (keeping your boat afloat).

In pole vaulting, the higher the bar is placed, the more difficult it is to clear it. Explain why this is a good analogy to help students understand enzymes and activation energy.

-In this analogy, the bar represents the activation energy necessary for the reaction to occur. The higher the bar, the harder it is to jump. The more activation energy that is required, the harder it will be for the reaction to occur.

Energy is never created or destroyed. What happened to the energy that was stored in your gas tank after your lawnmower comes to a stop as a result of running out of gas?

-It was converted to heat

Sucrase is the enzyme that breaks down sucrose into glucose and fructose. Will sucrose also catalyze the breakdown of the disaccharide maltose? Briefly explain your answer.

-No, because maltose will have a different structure than sucrose and so it will not fit into the active site of sucrase

Which of the following statements regarding transport across a plasma membrane is false?

-Passive transport requires an input of energy fro the cell

Which of the following best describes the structure of a plasma membrane?

-Proteins embedded in two layers of phospholipids

Use Figure 5.15B on page 85 of your textbook to answer this question. Assume that a toxin is introduced to the cell that binds to and removes substance C from the pool of molecules par- ticipating in the reaction. Briefly explain what would happen to the amount of substance B.

-The amount of substance B would increase because there would no longer be any feedback inhibition.

Dr. Agre's research into aquaporins hinged on two key observations. List both observations.

-The antibody they made did not bind to any part of the Rh antigen and the antibody bound to red blood cells in large quantities.

What feature does diffusion, osmosis, and facilitated diffusion all share?

-They are all types of passive transport.

Biologists have described a cell's plasma membrane as being a fluid mosaic. Briefly explain why this is an accurate description. Use the figure on page 74 to help with this.

-This is an accurate description because a plasma membrane is made of multiple types of molecules with many different functions (the mosaic) and the molecules are in constant motion around each other (fluid).

Penicillin is a drug that affects bacterial cells and not human cells. How is this possible?

-This is possible because the drug is targeting a structure not found in eukaryotic cells.

A cell pumps certain ions against their concentration gradient in order to maintain those gradients. What type of cellular work is this?

-This would be considered transport work.

True or false: Aquaporins form the specific protein channel through which water diffuses. If false, make it a correct statement.

-True

True or false: The fact that all cells have a plasma membrane supports the evolutionary linkage of all life. If false, make it a correct statement.

-True

The food we eat has chemical energy. Is it possible for a candy bar to have potential energy for two different reasons at the same time? Briefly explain your answer.

-Yes, it is. The candy bar has potential energy due to the bonds within the molecule, but it could also have potential energy if you placed it near the edge of a table.

The graph on page 83 in your textbook illustrates the difference between a chemical reaction with and without an enzyme. Can the reaction represented by the black line still occur without the enzyme? Briefly explain your answer.

-Yes, it would just take more energy to get the reaction started

A chemical reaction is determined to be endergonic. If you were trying to get that reaction to occur using a separate reaction, what would you do?

-You would couple it to an exergonic reaction.

The energy needed to initiate a chemical reaction is the ____________.

-activation energy

d. A reaction that requires an input of energy: _________________

-endergonic reaction

c. A reaction that gives off energy: _________________

-exergonic reaction

b. A series of reactions that either build or break down a molecule: ________________

-metabolic pathway

a. The sum of all chemical reactions in an organism: ____________

-metabolism

a. Diffusion of water across a semi-permeable membrane: ____________

-osmosis

b. Movement across a cell membrane that requires no energy from a cell: _______________

-passive transport

Every cell has a(n) ________________ that allows it to maintain a cellular environment that is separate from the environment in which it is found.

-plasma membrane

Nonpolar is to diffusion as ____________ is to facilitated diffusion.

-polar

Anything that inhibits ATP synthesis in a cell most likely

-results in the death of the cell

c. Movement of a substance from high to low concentration: ______________

-simple diffusion

In contrast to passive transport, active transport pumps a stubstance _________ its gradient.

-up