Chapter 5

Where is the energy stored that cells use for work?
in the arrangement of atoms within molecules
What happens to the chemical energy that is extracted by cellular activities that is not used for cellular work?
The energy contributes to the entropy of the system
What allows simple molecules to assemble into more complex molecules, and also disassemble, in cells but not in other non-biological environments?
Cells couple energy-releasing reactions to energy-requiring reactions.
Which of the following modifications do you predict would increase the amount of energy that could be stored in ATP?
if the negative charge of each phosphate group were increased
What is potential energy?
Energy in Storage
What is kinetic energy?
Energy at work
What is the first law of Thermodynamics?
States tgat the amount f available energy is finite but can be changed from one form to another
What is the second law of Thermodynamics?
states that every energy transformation makes the universe more disordered and that most energy transformations release heat.
What is an exergonic reaction?
Chemical reaction that releases energy
What is an endergonic reaction?
Requires a net input of energy
Describe teh function of enzymes
An enzyme serves as a biological catalyst, increasing the rate of a reaction without being changed into a different molecule. An enzyme does not add energy to a reaction; instead, it speeds up a reaction by lowering the energy barrier.
How does the net amount of energy released during the breakdown of sucrose compare between a spontaneous reaction and one catalyzed by sucrase?
The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction
Which type of enzyme research would be of greatest use to a pharmaceutical company?
Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity.
Which statement regarding enzyme function is true?
Excessive salt ions can cause an enzyme to denature
Consider a hypothetical metabolic pathway for the synthesis of the amino acid arginine: precursor A intermediate B arginine. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with arginine inhibiting the conversion of precursor A to intermediate B. In this case, arginine almost certainly acts as a _____ of the first enzyme in the pathway.
noncompetitive inhibitor
According to the second law of thermodynamics,
The ordering of one system depends on the disordering of another.
an example of the second law of thermodynamics
The aerobic respiration of glucose generates heat.
If the entropy of a system is increasing, this means that
energy input will be needed to maintain organization
Cellular respiration is an example of
an exergonic reaction, Cellular respiration is characterized by the breaking down of complex molecules and the release of energy.
Most cellular work is accomplished by _____ energizing molecules by _____ them.
ATP ... phosphorylating
If the tertiary structure of an enzyme is changed _____.
its substrate may not fit properly in the active site
When does Competitive inhibition occur?
when a molecule mimics the substrate
Which of these statements about enzyme inhibitors is true?
The action of competitive inhibitors may be reversible or irreversible
Why doesn't the antibiotic penicillin harm humans?
Human cells do not have cell walls
Why are phospholipids well suited to be the main structural components of membranes?
They form a selectively permeable structure.
The lipids in a cell membrane are arranged _____.
so that the nonpolar parts of two lipids point toward each other
Phospholipids are well suited to serve as the major component of the plasma membrane because they
have a water-soluble part and a water-insoluble part
Which of the following best describes the general structure of a cell membrane?
proteins embedded in two layers of phospholipid
The membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true? (
The fluid is phospholipid and the mosaic is protein
Stability of the plasma membrane is enhanced by
cholesterol molecules
Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell ___ because _____________.
B ... the diffusion gradient there is steeper
Which of these statements describes what occurs in facilitated diffusion
Facilitated diffusion of solutes occurs through protein pores in the membrane
Which one of the following is NOT involved in facilitated diffusion
an outside energy source
The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? (5.17)
a hypertonic sucrose solution
Which of these situations accurately represents osmoregulation in organisms?
Plant cells need a hypotonic environment for their cells to stay turgid
If the volume of a cell increases when it is placed in an aqueous solution, that solution is said to be __________ to the cell.
a difference between active transport and facilitated diffusion?
Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.
The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when
the concentration of the solute is lower inside the cell than outside it
NOT needed for active transport
a concentration gradient
Which of the following enables a cell to pick up and concentrate a specific kind of molecule?
receptor-mediated endocytosis
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via
Some liver cells ingest bacteria, a function probably accomplished by
Which statement best describes phagocytosis?
A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole.
LDLs enter cells by means of
receptor-mediated endocytosis