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In a lipid bilayer, ___________ fatty acid tails face each other within the bilayer and form a region that excludes water.
hydrophobic
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What is meant by the term �fluid mosaic model�?
It is the movement of lipids and integral proteins within the lipid bilayer.
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Cholesterol within membranes functions as a(n) ____________ through its interactions with both hydrophobic and hydrophilic parts of phospholipids
temperature controller
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Which of the following statements about lipid bilayers is True?
They can fuse with other bilayers.
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A transmembrane protein differs from other membrane proteins because it:
completely extends through the membrane.
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Proteins that are destined to become associated with the inner surface of the plasma membrane are:
made on free ribosomes in the cytoplasm.
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Biological membranes are normally permeable to:
small, hydrophobic molecules.
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The passive movement of a substance along its concentration gradient is termed:
diffusion.
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If the concentration of solutes in a cell is less than the concentration of solutes in the surrounding fluid, then the extracellular fluid is said to be:
hypertonic.
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What kind of organism reaches equilibrium?
a dead organism.
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A patient who has had a severe hemorrhage accidentally receives a large transfusion of distilled water directly into a major blood vessel. You would expect this mistake to:
have serious, perhaps fatal consequences because the red blood cells could swell and burst.
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A plant cell placed in a hypertonic solution will:
undergo plasmolysis.
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Facilitated diffusion:
requires a transmembrane protein.
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A bacterium containing sodium ions at a concentration of 0.1 mM lives in a pond that contains sodium ions at 0.005 mM. Evidently, sodium ions are entering the cell by:
active transport.
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Which of the following statements about the sodium-potassium pump is true?
It transports 3 sodium ions out of the cell in exchange for 2 potassium ions.
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In the cotransport of glucose and sodium ions:
glucose molecules are transported down their concentration gradient.
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A human white blood cell engulfs a bacterial cell by:
phagocytosis.
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Receptor-mediated endocytosis:
brings about the selective uptake of materials by enclosing them in membranous vesicles.
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In cells that are constantly involved in secretion, an equivalent amount of membrane must be returned to the interior of the cell for each vesicle that fuses with the plasma membrane; if this does not occur, then what would happen?
The cell surface will keep expanding.
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Plasmodesmata of plant cells are functionally equivalent to ____________ of animal cells.
gap junctions
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Paracrine signaling is different from other types of signaling in that the signaling molecule:
acts on nearby cells.
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In classical endocrine signaling, hormones are transported to target cells:
in interstitial fluid.
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A receptor on the cell surface usually has several domains. The function of the external domain is:
holding the receptor within the membrane.
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Under which of the following situations would receptor down-regulation\ most likely occur?
The concentration of a hormone is too high.
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When acetylcholine binds its receptor on the surface of a muscle cell, which of the following happens next?
A sodium gate opens.
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The outer part of a G protein receptor binds ______, and its inner part binds _______.
the signaling molecule; a G protein
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An example of a neurotransmitter that opens ligand-gated sodium channels is:
GABA.
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When a receptor binds to its G protein, which of the following happens next?
GDP is replaced by GTP.
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An example of a second messenger is:
protein kinase A.
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Adenylyl cyclase catalyzes the reaction in which:
a protein is phosphorylated.
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In the signal transduction pathway involving cAMP, once cAMP is formed, it then activates:
protein kinase.
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A protein kinase catalyzes the reaction in which:
a protein loses a phosphate group.
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In the cAMP signal transduction pathway, once a protein kinase isactivated, which of the following happens next?
Adenylyl cyclase is activated.
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Calmodulin is a:
calcium-binding protein.
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Most enzyme-linked receptors are:
tyrosine kinases.
-
The main signaling cascade for cell division and differentiation is the _______ cascade.
MAP kinase
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Nitric oxide binds _________ which is ________ target cells.
guanylyl cyclase; inside
-
The function of scaffolding proteins is to:
organize signal molecule complexes.
-
Which of the following responses involves the activation of ionchannels?
serotonin-stimulated transmission of a neural impulse
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When Arabidopsis thaliana is exposed to drought conditions, the concentration of abscisic acid concentration _______ which leads to the ________.
increases; closing of stomata
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The ultimate source of energy for almost all living organisms is:
the sun.
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An organism can exchange matter and energy with its surroundings.Thus, any change in an organism�s energy content must be balanced by a corresponding change in the energy content of the surroundings. As such, an organismis referred to as:
an open system.
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Which word is defined by this phrase: A measure of disorder orrandomness?
entropy
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In order for a cell to maintain a high degree of order, it must:
constantly use energy.
-
The sum of all chemical activities taking place in an organism is:
metabolism.
-
Catabolic reactions involve the:
breakdown of large organic molecules to simple building blocks.
-
An exergonic reaction is considered to be:
spontaneous.
-
A reaction with a negative value of ?G is referred to as an_________________ reaction.
exergonic
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An endergonic reaction can proceed only if it absorbs:
more free energy than is released by a coupled exergonic reaction.
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Energy stored within the molecules of ATP is in the form of ____________energy.
potential
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