Bio exam #2
You measure the concentration of a polar molecule inside and outside of a cell. You find that the concentration of the molecule is higher in the cell and is gradually increasing. You also measure the ATP concentration inside the cell and find that it is dropping. What is occurring?
Active transport
Diffusion stops once a solution is at equilibrium
F
The rate of diffusion decreases as temperature decreases,
F
20. Solution "A" contains less dissolved solute than solution "B". Therefore, solution "A" is ____compared to solution "B"
Hypotonic
Integral membrane proteins are proteins that
Partially penetrate or completely span the phospholipid bilayer of the membrane
14Diffusion refers to the tendency of molecules to move about randomly in space.
T
AsNet diffusion refers to the directional movement of molecules from an area of high concentration to one of lower concentration
T
Diffusion occurs whether or not a concentration gradient is present
T
Net diffusion continues once a solution is at equilibrium.
T
The rate of diffusion of a molecule depends on the kinetic energy of the molecule.
T
The unregulated movement of ions and other charged or large, polar molecules across biological membranes is prevented by
The hydrophic core of the lipid bilayer
Which of the following is false about noncompetitive inhibition?
The inhibitor binds to the active site of the enzyme
The movement of ions and large polar molecules across membranes is made possible by
The integral membrane proteins present in the membrane
Paramecium is a unicellular organism that lives in fresh water. Suppose you are studying two populations of this organism: one population lives in a pond in northern Ontario, Canada, and the other lives in a pond in southern Florida. If you examined the plasma membranes of both of these populations at the same time of year, which of the following would likely be true
The paramecia in FL would have more saturated fatty acid side chains in the phospholipids of their membranes compared to those in canada
Glycogen synthase is an enzyme that builds glycogen molecules by connecting individual glucose molecules to one another through glycosidic linkages. Which of the following correctly describes the reaction carried out by glycogen synthase?
The reaction is an anabolic, endergonic reaction
Which of the following statements about metabolic pathways is false?
They always release energy stored in organic compounds
Which of the following do gap junctions and desmosomes have in common with each other?
They both depend on the function of integral membrane proteins
the initial "investments" of energy required for a chemical reaction to proceed is called the _____
activation energy
As the number of double bonds in the fatty acid side chains of phospholipids decreases, the fluidity of the membrane ______
decreases
Desaturase are enzymes that add double bonds (unsaturated) to existing hydrocarbon chains, such as the fatty acids in membrane phospholipids. now imagine that you are studying plant homeostasis in NC, and you are particularly interested in seasonal changes in desaturase activity. Which of the following would you expect to observe?
desaturase activity would increase as temp decreased with the onset of winter
.Cells engulf particles and bring them into the cytoplasm using a process called
endocytosis
Water enters unicellular organisms that live in fresh water at a faster rate than it leaves because the cytoplasm of these organisms is ____ compared to the freshwater environment outside the cell.
hypertonic
movement of substances across a membrane by active transport requires which of the following ?
integral membrane proteins and ATP
the insulin receptor is an integral membrane protein that crosses the plasma membrane. Part of the receptor protein extends outside of the cll and another portion extends into the cytoplasm of the cell interior. Which of the following is TRUE about the amino acids of the insulin receptor that are present in the transmembrane portion of the protein (that is, the part of the protein that resides in the phospholipid bilayer)
many of the amino acid side chains of the transmembrane domain are hydrophobic
The lipid components of cellular membranes include
phospholipids and cholesterol
A fatty acid with no double bonds between carbon atoms is
saturated and had the maximum number of hydrogen atoms bonded to the carbon atom
The fluidity of cellular membrane is influenced by several factors, including
temp, saturation of fatty acid side chains, and cholesterol
The denaturation of an enzyme occurs when
the active site is destroyed, the tertiary structure of the enzyme is altered, and environmental conditions deviate substantially from the enzymatic optimum conditions
which of the following statements concerning enzymes is true
the active site of an enzyme is determined by the primary, secondary, and tertiary structure of the protein
The graph at the right shows that the rate of transport of glucose across a membrane changes as the concentration of glucose increases. The curve eventually flattens out because...
the carrier proteins in the membrane have reached the maximum rate of sugar transport
Which of the following correctly describes osmosis?
the diffiusion of water across a semipermeable membrare from a region of high water Concentration to a region of lower water concentration
Some bacteria are metabolically active in hot springs because
their enzymes have high optimal temps