Chapter 5 Quiz- Bio

Why doesn't penicillin harm human cells?

Microorganisms have cell walls, humans have cell membranes. Penicillin attacks the cell wall

What is the second law of thermodynamics?

!!Every transfer or transformation makes the universe more disordered (increases entropy) -in the form of heat -although order increases locally, universe as a whole is increasing in entropy

Which of the following statements regarding active transport is false?

Active transport is driven by the concentration gradient.

Which characteristic promoted the utilization of lipids as the first cell membrane A.spontaneous degradation of the intracellular environment B. self-assembly into a simple membrane C. ability to form an impermeable membrane D. formation of a semi-solid membrane E. utilization of the hydrophilic nature of lipids

B. self-assembly into a simple membrane

Membrane phospholipids A) have hydrophobic heads that face the center of the membrane and are shielded from water. B) have hydrophilic tails that face outward and are exposed to water. C) are able to drift about in the plasma membrane. D) remain fluid because they are tightly packed against one another.

C) are able to drift about in the plasma membrane.C) are able to drift about in the plasma membrane.

ATP can be used as the cell's energy exchange mechanism because A) endergonic reactions can be fueled by coupling them with the formation of ATP from ADP. B) ATP is the most energy-rich small molecule in the cell. C) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP. D) the regeneration of ATP from ADP can be fueled by coupling it with endergonic reactions. E) ATP is a disposable form of chemical energy, used once and then discarded by the cell.

C) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP.

Inhibition of an enzyme is irreversible when

Covalent bonds form between inhibitor and enzyme

Which of the following statements regarding membrane function is false? A) The plasma membrane forms a selective barrier around the cell. B) The plasma membrane plays a role in signal transduction. C) The plasma membrane has receptors for chemical messages. D) The plasma membrane is the control center of the cell. E) The plasma membrane is involved in self-recognition

D) The plasma membrane is the control center of the cell.

White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, what could you do to reduce interference from RBCs?

Mix the blood in a hypotonic solution, which will cause the RBCs to lyse.

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAID)inhibit inflammation by inhibiting an enzyme in the prostaglandin pathway, but by inhibiting this enzyme and this pathway they also inhibit pathways that protect the stomach from damage by stomach acid and that prevent aggregation of blood platelets to form blood clots. What can you conclude from this?

The enzyme is found in many different types of cells

Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline.

This is an example of Feedback inhibition

Heating inactivates enzymes by a. changing the enzyme's three-dimensional shape. b. breaking the covalent bonds that hold the molecule together. c. removing phosphate groups from the enzyme. d. causing enzyme molecules to stick together. e. None of the choices are correct.

a. changing the enzyme's three-dimensional shape

What is the basic difference between exergonic and endergonic reactions? a. In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.b. Exergonic reactions involve the breaking of bonds; endergonic reactions involvethe formation of bonds.c. Exergonic reactions release energy; endergonic reactions absorb it.d. Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds.e. Exergonic reactions involve the formation of bonds; endergonic reactions involve the breaking of bonds

c. Exergonic reactions release energy; endergonic reactions absorb it

Which figure depicts an animal cell placed in a solution hypotonic to the cell? (see figure)

cell A

Which statement regarding enzyme function is true? a. higher temperatures allow greater contact between enzymes and substrates; therefore, the higher the temperature the better the enzyme will function b. enzymes cannot function at a pH lower than 6 c. most coenzymes are inorganic substances such as ions of iron or potassium d. excessive salt ions can cause an enzyme to denature.

d. excessive salt ions can cause an enzyme to denature

When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane, and osmosis is allowed to take place, the water will...

exhibit a net movement to the side with lower water concentration

Which of the following energy transfers is impossible in living systems?

heat to light energy.

An energy barrier -prevents the spontaneous breakdown of molecules in the cell. -can only be overcome with the use of enzymes. -is higher than the activation energy of a reaction. -is the amount of energy that must be produced by the reactants to end a chemical reaction.

prevents the spontaneous breakdown of molecules in the cell.

LDLs bind to

receptor proteins and then enter cells by endocytosis

Facilitated diffusion across a biological membrane requires _____ a moves a substance _____ its concentration gradient

transport proteins . . . down