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53 terms

Biology Ch. 5 - The Working Cell

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According to _____, energy cannot be created or destroyed.
the first law of thermodynamics
Most of a cell's enzymes are
proteins.
Oxygen crosses a plasma membrane by
passive transport.
You are adrift in the Atlantic Ocean, and being thirsty, drink the surrounding seawater. As a result
your cells lyse, due to the excessive intake of salt.
Which of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer?
Na+
In the reaction A = B+C+heat,
the potential energy of the products is less than that of the reactant.
Anything that prevents ATP formation will most likely
result in cell death.
Kinetic energy differs from chemical energy in that
kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.
Which of the following processes can move a solute against its concentration gradient?
Active transport
What is the basic difference between exergonic and endergonic reactions?
Exergonic reactions release energy; endergonic reactions absorb it.
All cells are enclosed by a plasma membrane that is similar in _____ and _____.
structure . . . function
Plasma membranes are selectively permeable. This means that
the plasma membrane allows some substances to enter or leave a cell more easily than others.
The fluid mosaic model describes the plasma membrane as consisting of
individual proteins and phospholipids that can drift in a phospholipid bilayer.
Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell is called
signal transduction.
Substrates bind to an enzyme's ______ site.
active
Which of the following will have no effect on the rate of an enzyme-catalyzed reaction?
net change in energy
Which of the following statements about the ATP molecule is true?
It contains a nitrogenous base molecule called adenine.
Most of the functions of a cell membrane are performed by
proteins.
When an enzyme catalyzes a reaction,
it lowers the activation energy of the reaction.
Which of the following substances could be a cofactor?
a zinc atom
Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment
is hypotonic to the protozoan.
In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The solution in the balloon is _____ relative to the solution in the beaker.
hypotonic
In a hypotonic solution, an animal cell will
lyse.
After the reverse osmosis system has been operating for 30 minutes, the solution in Tank A would (Check paragraph on page B-5)
be hypertonic to Tank B.
Which of the following processes could result in the net movement of a substance into a cell, if the substance is more concentrated in the cell than in the surroundings?
Active transport
Which of the following statements regarding active transport is false?
Active transport is driven by the concentration gradient
The transfer of a phosphate group to a molecule or compound is called
phosphorylation.
Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing
chemical energy into kinetic energy.
In the lab, you use a special balloon that is permeable to water, but not sucrose, to make an "artificial cell" The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur?
Water will leave the balloon
A child is brought to the hospital with a fever of 107oF. Doctors immediately order and ice bath to lower the child's temperature. Which of the following statements offers the most logical explanation for this action?
Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.
(See chart, page B-7) Which figure depicts an animal cell placed in a solution hypotonic to the cell?
Cell A
Phagocytosis is to eating as pinocytosis is to
drinking.
The molecules responsible for membrane transport are
proteins.
Small, nonpolar, hydrophobic molecules such as fatty acids
easily pass through a membrane's lipid bilayer.
Which of the following is a coenzyme?
vitamin B6
A plant cell in a hypotonic solution
is turgid.
Osmosis can be defined as
the diffusion of water.
The process of a white blood cell engulfing a bacterium is
phagocytosis.
Which of the following processes is endergonic?
the synthesis of glucose from carbon dioxide and water
The cholesterol associated with animal cell membranes
helps to stabilize the cell membrane at body temperature.
Living systems
decrease their entropy while increasing the entropy of the universe.
Heating inactivates enzymes by
changing the enzyme's three-dimensional shape.
When physicians perform an organ transplant, they choose a donor whose tissues match those of the recipient as closely as possible. Which of the following cell components are being matched?
cell-surface carbohydrates
The energy required to initiate an exergonic reaction is called
the energy of activation.
Which of the following statements regarding enzyme function is false?
Enzymes are used up in chemical reactions
When a cell uses chemical energy to perform work, it couples a(n) ______ reaction with a(n) ______ reaction.
exergonic . . . endergonic
Cells acquire LDLs by
receptor-mediated endocytosis.
Which part of the ATP molecule brakes free of the rest when an ATP molecule is used for energy? (Model page B-10)
Part E (Phosphate; makes it ADP)
A cell that neither gains nor loses water when it is immersed in a solution is
isotonic to its environment.
Certain cells that line the stomach synthesize a digestive enzyme and secrete it into the somach. This enzyme is a protein. Which of the following processes could be responsible for its secretion?
exocytosis
If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference?
the relative inelasticity and strength of the plant cell wall
A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates
the second law of thermodynamics.
Facilitated diffusion across a biological membrane requires _____ a moves a substance _____ its concentration gradient.
transport proteins . . . down