Chapter 5, 6, 7 Homework

Question 1

Biologists use the fluid mosaic model to describe membrane structure. Which statements about the fluid mosaic structure of a membrane are correct? (3)

• The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together.
• 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.
• Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.
• The diverse proteins found in and attached to membranes perform many important functions.
• Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer.

Answer 1

• 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.
• Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.
• The diverse proteins found in and attached to membranes perform many important functions.

Question 2

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?
a) the similarity of the drug molecule to other molecules that are transported into the target cells
b) the nonpolar, hydrophobic nature of the drug molecule
c) the phospholipid composition of the target cells’ plasma membrane
d) the concentration of the drug molecule that is transported in the blood

Answer 2

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

Question 3

Working from the inside out what would be the order of components that make up the phospholipid bilayer?

Answer 3

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

Question 4

When molecules move down their concentration gradient, they are moving from ______ concentrated to _______ concentrated.

Answer 4

more to less

Question 5

Diffusion across a biological membrane is called?

Answer 5

passive transport

Question 6

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

Answer 6

facilitated diffusion

Question 7

How does water cross the plasma membrane?

Answer 7

through facilitated diffusion or diffusion

Question 8

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?

Answer 8

active transport

Question 9

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

Answer 9

endocytosis

Question 10

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

Answer 10

osmosis

Question 11

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

Answer 11

the difference in water concentration across a selectively permeable membrane

Question 12

What is the ideal osmotic environment for an animal cell and what is it for a plant cell?

Answer 12

An animal cell is an isotonic environment and a plant cell is a hypotonic environment.

Question 13

In a which osmotic environment is there too much water to where the animal cell swells and possibly explodes?

Answer 13

hypotonic

Question 14

In which osmotic environment is there a diffusion of water out of the cell and it shrivels up?

Answer 14

hypertonic

Question 15

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 _____.

Answer 15

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

Question 16

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 _____.

Answer 16

B…the diffusion gradient there is steeper

Question 17

What type of transport is facilitated diffusion?

Answer 17

passive transport

Question 18

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

Answer 18

water

Question 19

What is active transport?

Answer 19

When a solute is moved against its concentration gradient

Question 20

Which of the following is a difference between active transport and facilitated diffusion?
a) Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot.
b) Facilitated diffusion involves transport proteins, and active transport does not.
c) Active transport involves transport proteins, and facilitated diffusion does not.
d) Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

Answer 20

d) active transport required the expenditure of cellular energy, and facilitated diffusion does not.

Question 21

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?

Answer 21

active transport, because this can move substances against their concentration gradient

Question 22

Endocytosis moves materials _____ a cell via _____.

Answer 22

into…membranous vesicles

Question 23

You can recognize the process of pinocytosis when _____.

Answer 23

the cell is engulfing extracellular fluid

Question 24

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

Answer 24

phagocytosis

Question 25

When does phagocytosis occur?

Answer 25

When a cell engulfs a large particle

Question 26

A vesicle inside the cell fuses with the plasma membrane and releases its contents outside of the cell.

Answer 26

exocytosis

Question 27

A form of passive transport. Particles move across the plasma membrane using transport proteins.

Answer 27

facilitated diffusion

Question 28

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

Answer 28

endocytosis

Question 29

A form of passive transport. Molecules move across the plasma membrane by crossing the lipid bilayer.

Answer 29

diffusion

Question 30

Requires energy from the cell. Molecules move against their concentration gradient.

Answer 30

active transport

Question 31

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 __________.

Answer 31

endocytosis

Question 32

What is kinetic energy?

Answer 32

the energy associated with motion

Question 33

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

Answer 33

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

Question 34

Chemical energy is a form of _____ energy.

Answer 34

potential energy

Question 35

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

Answer 35

cellular respiration

Question 36

What are so by-products of cellular respiration?

Answer 36

heat and water

Question 37

An enzyme is considered a(n) ______ because it speeds up a chemical reaction without being used up.

Answer 37

catalyst

Question 38

In a catalyzed reaction, a reactant is often called a(n) _____.

Answer 38

substrate

Question 39

An enzyme is specific because the shape of its ______ matches only particular reactants.

Answer 39

active site

Question 40

An enzyme speeds up reactions by lowering the _______.

Answer 40

activation energy

Question 41

The __________ between an active site and its substrate often strains bonds and helps the reaction proceed.

Answer 41

induced fit

Question 42

A(n) _______, which is often a vitamin, binds to an enzyme and plays a role in catalysis.

Answer 42

coenzyme

Question 43

High temperatures or changes in pH can ________ an enzyme, causing it to lose its shape and biological activity.

Answer 43

denature

Question 44

Explain the advantage of feedback inhabitation to a cell.

Answer 44

it prevents the cell from wasting valuable resources by synthesizing more of a particular product than needed

Question 45

What is a competitive inhibitor?

Answer 45

Reduces and enzymes productivity by blocking substrate molecules from entering the active site. They can be overcome by increasing the concentration of the substance.

Question 46

What is a noncompetitive inhibitor?

Answer 46

A noncompetitive inhibitor does not enter the active site. Instead, it binds to a site elsewhere on the enzyme which changes the enzymes shape therefore the active site can no longer fit the substrate.

Question 47

Why doesn't the antibiotic penicillin harm humans?

Answer 47

Penicillin blocks the active site of an enzyme that many bacteria use in making cell walls. But humans do not have cells walls so it does not harm humans.

Question 48

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?

Answer 48

the temperature should be raised due to enzymes not being denatured by high heat and work better in higher heat. If the temperature is not raised, then the reaction will occur at a much slower pace.

Question 49

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

Answer 49

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

Question 50

By binding to reactant molecules, enzymes make it _______ for the bonds in the molecules to break apart.

Answer 50

easier

Question 51

Enzymes _______ the overall energy input needed for a reaction to occur.

Answer 51

lower