Bio ch 5

Which statement best describes phagocytosis? Cells use this process to export products such as insulin or thyroxine. A receptor on the plasma membrane binds to a molecule, and the cell engulfs both the receptor and the molecule. A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole. Small droplets of extracellular fluid and all the dissolved solutes enter the cell by this process.

A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole.

Which of the following statements regarding diffusion is false? Diffusion requires no input of energy into the system. Diffusion occurs even after equilibrium is reached and no net change is apparent. Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated. Diffusion is a result of the thermal energy of atoms and molecules.

Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated.

A child is brought to the hospital with a fever of 107°F. Doctors immediately order an ice bath to lower the child's temperature. Which of the following statements offers the most logical explanation for this action? Elevated body temperatures cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions. Elevated body temperature will increase reaction rates in the child's cells and overload the limited number of enzymes found in the cell. Elevated body temperatures will increase the energy of activation needed to start various chemical reactions in the body. This will interfere with the ability of enzymes to catalyze vital chemical reactions. Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.

Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions.

Which of the following statements regarding enzymes is true? All enzymes depend on protein cofactors to function. An enzyme's function is unaffected by changes in pH. Enzymes catalyze specific reactions. Enzymes are inorganic.

Enzymes catalyze specific reactions

Which of the following statements regarding membrane protein function is false? Membrane proteins form junctions between cells. Membrane proteins act as receptors to molecules like hormones. Membrane proteins serve as enzymes. Membrane proteins transfer genetic information to the cytoplasm.

Membrane proteins transfer genetic information to the cytoplasm.

Which of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer? a small, nonpolar molecule such as butane (C4H10) CO2 O2 Na+

Na+

Which of the following statements is true about passive transport? Passive transport requires no expenditure of cellular energy. Passive transport phenomena can never reach equilibrium. Passive transport operates independently of diffusion. Passive transport operates independently of concentration.

Passive transport requires no expenditure of cellular energy.

Which of the following statements is true for all types of passive transport? Proteins are needed to transport molecules across the membrane. The concentration gradient is the driving force. Ions never cross the plasma membrane by passive transport. Only small polar molecules are able to cross the plasma membrane.

The concentration gradient is the driving force.

Which of the following substances could be a cofactor? a polypeptide a zinc atom a ribosome a protein

a zinc atom

Substrates bind to an enzyme's ________ site. allosteric active phosphate inhibitory

active

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This molecule rapidly enters the cell regardless of whether its concentration is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane? exocytosis passive transport phagocytosis active transport

active transport

Which of the following processes can move a solute against its concentration gradient? facilitated diffusion active transport osmosis passive transport

active transport

Aquaporins are found in all cells. allow for the active transport of water. allow water to cross the plasma membrane against its concentration gradient. allow water to cross the plasma membrane via facilitated diffusion.

are found in all cells

Heating inactivates enzymes by changing the enzyme's three-dimensional shape. removing phosphate groups from the enzyme. breaking the covalent bonds that hold the molecule together. causing enzyme molecules to stick together.

changing the enzyme's three-dimensional shape.

Phagocytosis is to eating as pinocytosis is to drinking. osmosis. chewing. lysis.

drinking.

Through an _____ reaction, ATP is hydrolyzed into ADP by _____ and _____ energy. exergonic ... losing a phosphate group ... releasing endergonic ... gaining a phosphate group ... releasing exergonic ... gaining a phosphate group ... releasing endergonic ... losing a phosphate group... requiring

exergonic ... losing a phosphate group ... releasing

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 competitive inhibition. feedback inhibition. noncompetitive inhibition. irreversible inhibition.

feedback inhibition

The cholesterol associated with animal cell membranes is attached to membrane proteins and extends into the watery environment surrounding the cell. is an abnormality resulting from a diet high in cholesterol. helps solidify the membranes when the room temperature is below freezing. helps to keep phospholipids from being too close to one another.

helps solidify the membranes when the room temperature is below freezing

When an enzyme catalyzes a reaction, it is used once and discarded. it acts as a reactant. it lowers the activation energy of the reaction. it raises the activation energy of the reaction.

it lowers the activation energy of the reaction.

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. kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement. kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat. chemical energy is a particular form of kinetic energy.

kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules.

The process of a white blood cell engulfing a bacterium is pinocytosis. phagocytosis receptor-mediated endocytosis. osmosis.

phagocytosis

Anything that prevents ATP formation will most likely force the cell to rely on lipids for energy. force the cell to rely on ADP for energy. result in cell death. have no effect on the cell.

result in cell death

According to ________, energy cannot be created or destroyed. the first law of thermodynamics the second law of thermodynamics Aristotle's first principle the third law of thermodynamics

the first law of thermodynamics

Plasma membranes are selectively permeable. This means that glucose cannot enter the cell. anything can pass into or out of a cell as long as the membrane is intact and the cell is healthy. the plasma membrane allows some substances to enter or leave a cell more easily than others. plasma membranes must be very thick.

the plasma membrane allows some substances to enter or leave a cell more easily than others.

The active site of an enzyme is the highly changeable portion of an enzyme that adapts to fit the substrates of various reactions. the region of a product that detaches from the enzyme. the region of an enzyme that attaches to a substrate. the region of a substrate that is changed by an enzyme.

the region of an enzyme that attaches to a substrate.

Which of the following processes is endergonic? the burning of wood the synthesis of glucose from carbon dioxide and water the breakdown of glucose cellular respiration

the synthesis of glucose from carbon dioxide and water

Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient. energy and transport proteins; against transport proteins; down transport proteins; against energy and transport proteins; down

transport proteins . . . down

Which of the following is a coenzyme? iron vitamin B6 iodine zinc

vitamin B6