Chapter 5

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why?

There is a precise compatibility between the active site and the lactose molecule.

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of

active transport

Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug?

competitive inhibition

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

facilitated diffusion

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

Chemical energy is a form of _____ energy.

potential

Which curve shows the course of the reaction in the presence of an enzyme--the black curve or the red curve? Which line represents the activation energy for that reaction--a, b, or c?

red curve; line b

Structure A is a ________

solute

In the figure below, working from the inside out, what would be the order of components observed?

water, hydrophilic head, hydrophobic tail, hydrophobic tail, hydrophilic head, water

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

In active transport,

molecules move across the plasma membrane against their concentration gradient.

When molecules move down their concentration gradient, they move from where they are ______ to where they are ___________

more concentrated less concentrated

The synthesis of an amino acid follows this pathway: precursor A > intermediate B > amino acid C. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with amino acid C inhibiting the conversion of precursor A to intermediate B. Amino acid C acts as a _____ of the first enzyme in the pathway.

noncompetitive inhibitor

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Diffusion across a biological membrane is called ______________

passive transport

Facilitated diffusion is a type of ________

passive transport

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

1. An enzyme is considered a(n) ____ because it speeds up a chemical reaction without being used up. 2. In a catalyzed reaction, a reactant is often called a(n) ______. 3. An enzyme is specific because the shape of its ________ matches only particular reactants. 4. An enzyme speeds up reactions by lowering the _________. 5. The _______ between an active site and its substrate often strains bonds and helps the reaction proceed. 6. A(n) _______ , which is often a vitamin, binds to an enzyme and plays a role in catalysis. 7. High temperatures or changes in pH can ______an enzyme, causing it to lose its shape and biological activity.

1. catalyst 2. substrate 3. active site 4. activation energy 5. induced fit 6. coenzyme 7. denature

1. vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell 2. form of passive transport. molecules move across the plasma membrane using a transport protein 3. plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell 4. a form of passive transport. molecules move across the plasma membrane by crossing the lipid bilayer 5. requires energy from the cell. molecules move against their concentration gradient

1. exocytosis 2. facilitated diffusion 3. endocytosis 4. diffusion 5. active transport

1. The ideal osmotic environment for an animal cell is a(n) ______ environment. 2. An animal cell placed in a(n) ______ solution will gain water, swell, and possibly burst. 3. There is a net diffusion of water out of an animal cell when it is placed in a(n) ________ solution. 4. The ideal osmotic environment for a plant cell is a(n) _______ environment. 5. A plant cell placed in a(n) ______ solution will lose water and plasmolyze. 6. A plant cell surrounded by a(n) _____ solution will be flaccid (limp).

1. isotonic 2. hypotonic 3. hypertonic 4. hypotonic 5. hypertonic 6. isotonic

Which of the following is a difference between active transport and facilitated diffusion?

Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. Submit

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

In this diagram of the plasma membranes of two adjoining cells, identify the protein indicated by the white arrow, including its function.

a receptor protein that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell

Which of these is exhibiting kinetic energy?

a space station orbiting Earth

Drag the terms to the appropriate locations on the concept map. ENERGY

a. kinetic b. potential c. motion d. chemical energy e. entropy f. heat g. first law of thermodynamics h. second law of thermodynamics

Why doesn't the antibiotic penicillin harm humans?

Human cells do not have cell walls.

Drag the labels to the appropriate locations in this diagram. Drag labels to targets in Group 1 to identify the main functions of membrane proteins. Drag labels to targets in Group 2 to identify some components associated with the plasma membrane

a. phospholipid bilayer b. fibers of extracellular matrix c. enzymatic activity d. microfilaments of cytoskeleton e. attachment to ECM and cytoskeleton f. signal reception and relay g. transport h. intercellular junctions i. cell-cell recognition

Facilitated diffusion

a. plasma mem b, side w/ higher concentration of molecules c. side with lower concentration of molecules d facilitated diffusion causes a net movement of molecules down their concentration gradient e transport protein

Active Transport

a. side w/ lower concentration of square molecules b. transport protein c. energy input from the cell d. plasma membrane e. side with higher concentration of square molecules

Drag the labels to their appropriate locations on the diagram

a. side with higher concentration of molecules b. plasma membrane c. side with lower concentration of molecules d. diffusion causes a net movement of molecules down their concentration gradient

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?

active transport

Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____.

actively pump water back into their cells to counter its loss due to osmosis

Which of these statements is TRUE with regard to this animation?

Sodium and potassium ions are transported against their concentration gradients.

Taq polymerase is an enzyme isolated from the organism Thermophilus aquaticus. This organism has been found living in the hot springs of Yellowstone National Park. This enzyme is used to copy human DNA from crime scenes. Most reactions are performed at ranges similar to those of the human body; however, what considerations should be made for optimum use of this enzyme?

Temperature should be raised

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements.

The diverse proteins found in and attached to membranes perform many important functions. Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

cellular respiration

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 __________.

endocytosis

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

endocytosis

"Conservation of energy" refers to the fact that _____.

energy cannot be created or destroyed but can be converted from one form to another

Use the graph and your knowledge of enzymes to identify the three true statements about enzymes.

-Enzymes lower the overall energy input needed for a reaction to occur. -Reactants cannot convert to products without an initial input of energy to start the reaction. -By binding to reactant molecules, enzymes make it easier for the bonds in the molecules to break apart.

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis?

the difference in water concentration across a selectively permeable membrane

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

the similarity of the drug molecule to other molecules that are transported into the target cells

Which of these are by-products of cellular respiration?

heat and water

This cell is in a(n) _____ solution.

hypertonic

You know that this cell is in a(n) _____ solution because the cell _____.

hypotonic...swelled

water crosses the plasma membrane

through facilitated diffusion or diffusion

Structure B is a ________

transport protein

Aquaporins are proteins that facilitate the transport of __________ across the membrane.

water