Chapter Seven

Question 1

What is a phospholipid bilayer?

Answer 1

plasma membrane composed of lipids, proteins, and carbohydrates

Question 2

What is the plasma membrane composed of?

Answer 2

lipids, proteins, and carbohydrates

Question 3

In the “fluid mosaic model,” what does fluid mean?

Answer 3

phospholipids are not locked in place (sideways movement, occasionally flip sides)

Question 4

In the “fluid mosaic model,” what does mosaic mean?

Answer 4

different shapes proteins with different functions in the fluid

Question 5

How does temperatuere influence fluidity?

Answer 5

membrane becomes less fluid as temperature decreases and eventually solidifies

Question 6

What happens if the membrane gets too solid?

Answer 6

• permeability changes and molecules may not cross membrane
• proteins locked in place may not be able to function properly

Question 7

What happens if a membrane gets too fluid?

Answer 7

• may be too permeable and let molecules in that shouldn’t be crossing the membrane
• proteins may move out of position too easily and not function properly

Question 8

What do unsaturated phospholipids do to fluidity?

Answer 8

maintain fluidity in extreme cold

Question 9

What role does cholesterol play in the fluidity of the plasma membrane?

Answer 9

• reduces movement at high temps
• prevent solidification at low temps

Question 10

How did the plasma membrane of organisms in extreme cold adapt?

Answer 10

have lots of unsaturated phospholipid tails to remain fluid

Question 11

How did the plasma membrane of organisms in extreme heat adapt?

Answer 11

have unusual lipids that prevent excess fluidity

Question 12

How did the plasma membrane of organisms in variable environments adapt?

Answer 12

their composition may change with seasonal changes in environment

Question 13

What do integral proteins do?

Answer 13

penetrate the interior of the lipid billayer; most span the entire membrane (transmembrane protein)

Question 14

Peripheral proteins are…

Answer 14

not embedded in the lipid bilayer, loosely bound to surface

Question 15

What are the 6 major functions of proteins in the plasma membrane?

Answer 15

• transport
• enzymes
• signal transduction
• cell-cell recognition
• intercellular joining
• attachment

Question 16

Functions of proteins in the plasma membrane: Transport

Answer 16

hydrophilic channel, may change shape, active and passive types

Question 17

Functions of proteins in the plasma membrane: Enzymes

Answer 17

catalyze reactions, often have reactions in the adjacent fluid

Question 18

Functions of proteins in the plasma membrane: Signal transduction

Answer 18

transfer signal from external messenger to interior of cell

Question 19

Functions of proteins in the plasma membrane: Cell-cell recognition

Answer 19

ID tags to recognize proteins of other cells; temporary binding

Question 20

Functions of proteins in the plasma membrane: Intercellular joining

Answer 20

more permanent joining of cells (communication)

Question 21

Functions of proteins in the plasma membrane: Attachment

Answer 21

maintain cell shape and location; bind to cytoskeleton and ECM

Question 22

The fluid mosaic is both ________ and __________

Answer 22

structural and fuctional

Question 23

What are carbohydrates main function in the plasma membrane?

Answer 23

cell-cell recognition

Question 24

What do carbohydrates do in the plasma membrane?

Answer 24

• reject foreign cells
• sort cells into tissues and organs

Question 25

What does **selective permeability** mean?

Answer 25

plasma membrane allows some substances to cross more easily than others

Question 26

What can easily pass through the plasma membrane?

Answer 26

hydrophobic molecules

Question 27

Polar molecules may be ______ or ______ due to the hydrophobic tails of the bilayer

Answer 27

stopped or slowed

Question 28

________ transport polar molecules and ions that cant easily pass through the membrane

Answer 28

proteins

Question 29

What is **passive transport**?

Answer 29

transport of substances across the plasma membrane without the use of energy

Question 30

What is **diffusion**?

Answer 30

molecules move from high concentration to low concentration until equilibrium is reached

Question 31

What is **osmosis**?

Answer 31

special case of diffusion involving water

Question 32

What do **hypotonic** substances do to plant cells?

Answer 32

cause them to lyse (burst); cells gain water

Question 33

What do **isotonic** substances do to plant cells?

Answer 33

nothing; no net movement of water

Question 34

What do **hypertonic** substances do to plant cells?

Answer 34

cause them to shrivel and die; cell loses water

Question 35

What is **facilitated diffusion**?

Answer 35

passive transport via proteins

Question 36

What is a **channel protein**?

Answer 36

protein that allows the transport of specific substances across a cell membrane

Question 37

What is a **carrier protein**?

Answer 37

proteins that change shape to allow a substance to pass through the plasma membrane

Question 38

What is **active transport**?

Answer 38

transport across the plasma membrane that requires energy

Question 39

Active transport moves _____ molecules

Answer 39

larger

Question 40

What is **exocytosis**?

Answer 40

secretion of molecules (wastes released outside of cell)

Question 41

What is **endocytosis**?

Answer 41

cell takes in molecules and particulate matter

Question 42

What are the 3 types of endocytosis?

Answer 42

- **phagocytosis**- cellular eating - **pinocytosis**- cellular drinking - **receptor mediated cytosis**- take bulk of subtance, bind receptors, take one molecule at a time (saves evergy); pinocytosis