BIO Review Ch. 5

________ energy is the type of ________ energy used to power the work of the cell.

chemical; potential

Enzymes ______ the activation energy of a reaction. The energy change between products and reactants is _______ for a reaction that is catalyzed versus one that is not.

lower; the same

What is the function of the sodium-potassium pump in nerve cells?

pump Na+ out of the cell and K+ into the cell

What is meant by the term "enzyme specificity"?

An enzyme catalyzes only one type of reaction.

Which of the following is a CORRECT statement about aquaporins?

Each aquaporin molecule allows billions of molecules of water to cross the plasma membrane each second.

The pesticide malathion and some drugs used as anesthetics both block an enzyme that is critical for transmitting nerve impulses. Why don't patients die like insects when they undergo surgery?

Enzyme inhibition with malathion is irreversible but with anesthetics, reversible.

Imagine a U-shaped tube with a membrane at the bottom of the "U". The membrane is permeable to glucose, sucrose and water. You place a concentrated glucose solution on Side A and an equally concentrated sucrose solution on Side B. Describe the movement of each solute across the membrane during the first few hours.

Glucose will move into Side B down its concentration gradient, and sucrose will move into Side A down its concentration gradient.

What is one way of reducing the effectiveness of a competitive enzyme inhibitor?

Increase the concentration of the substrate.

One model of the cell membrane is that it is a "fluid mosaic." What does this mean?

It consists of proteins suspended in a fluid phospholipid bilayer.

In what way, if any, does osmosis differ from simple diffusion?

Polar water molecules cluster with hydrophilic molecules, so only free water diffuses down its concentration gradient.

When you hear "Substance X is moved against its concentration gradient," what do you think of?

Substance X has moved from a region of lower to a region of higher concentration with the help of ATP.

Imagine a metabolic pathway where: Molecule A → Molecule B → Molecule C → Molecule D → Product X. Enzyme 1 catalyzes the first reaction (Molecule A → Molecule B), Enzyme 2 catalyzes the second reaction (Molecule B → Molecule C), and so on. Product X exerts feedback inhibition on Enzyme 2. What is the consequence of this inhibition as Product X accumulates?

The concentration of Molecule B increases.

Researchers used frog eggs to learn more about aquaporins. What characteristic of normal frog eggs was essential in these studies?

They are largely impermeable to water.

Which of the following statements about coenzymes is correct?

They are organic cofactors with enzymes in reactions.

In what sense are living cells more efficient that internal combustion engines?

They convert a greater proportion of fuel to useful energy.

A plant cell placed into an isotonic solution ________. An animal cell placed into an isotonic solution _______.

becomes flaccid; neither swells nor shrivels.

Before refrigeration, meat was preserved by adding ________. What effect did this have on any contaminating bacteria or fungi?

concentrated salt solutions; plasmolysis

Building a molecule of ATP is an ________process. Hydrolyzing a molecule of ATP is an _______ process. This cycle is an example of _________.

endergonic: exergonic: energy coupling

Photosynthesis is an ______ process. Energy from ______ allow the production of products with __________.

endergonic; the sun; higher potential energy than the reactants.

At what stage of active transport is ATP needed?

for the transport protein to change its shape

Which of the following prevents the cells of a freshwater fish from becoming hypotonic and bursting?

osmoregulation

Both a living cell and an automobile convert fuel and ______ to the waste products ___________. In the process, ______ is produced, which represents the entropy of the reaction.

oxygen; CO2 and water; heat

Which method of transport uses coated pits?

receptor-mediated endocytosis

Endergonic reactions _______ energy and result in products that have _____ potential energy than the reactants.

require; higher

Which is the most inclusive and correct list of substances that use facilitated diffusion to cross cell membranes?

sugars, amino acids, ions, water