Chapter 7

Question 1

Plasma Membrane

Answer 1

Functions: Protection and controlling what goes in and out.

“selective permeability”: transport proteins control what goes in and out. The phospholipid bilayer keeps out hydrophilic substances.

Question 2

Phospholipid bilayer

Answer 2

A bunch of phospholipids with their hydrophobic tails facing each other.

Question 3

Fluid Mosaic model

Answer 3

The plasma membrane is a fluid mosaic model because protein molecules bob in and out and flow around relatively freely. Proteins are not randomly distributed.
Evidence for fluid nature of cell membrane: Proteins and hybrid cells (two cells merging)

Question 4

Fluidity

Answer 4

1. Proteins and lipids can shift about sideways and the such
2. Flip flop: lipids may flip-flop across the membrane
3. Saturated hydrocarbon tails = less fluidity
4. Cholesterol reduces membrane fluidity at moderate temperatures by reducing phospholipid movement, but at low temperatures it hinders solidification by being in the way.

Question 5

Membrane Proteins

Answer 5

1. Integral Proteins (carrier and channel): Includes transmembrane proteins. Penetrate the hydrophobic interior of the lipid bilayer. TransMemP span the membrane, other integral proteins extend only partway into the hydrophobic interior.
2. Peripheral proteins: Found on both ‘faces’ of the plasma membrane. Are not embedded in the lipid bilayer at all; they are loosely bound to the surface of the membrane.
3. ECM: Extracellular matrix. Attach to membrane proteins.

Question 6

Membrane Protein Functions

Answer 6

1. Transport
2. Enzyme activity
3. Signal Transduction
4. Cell-cell Recognition
5. Intercellular Joining
6. Attachment to the cytoskeleton and extracellular matrix (ECM).

Question 7

Cell recognition molecules

Answer 7

Carbohydrates, glycoproteins specifically. They serve as identification tags. Usually short-lived.

Question 8

Passive transport

Answer 8

Doesn’t require energy

Question 9

Diffusion

Answer 9

From high concentration to low concentration.

Question 10

Osmosis

Answer 10

From low concentration to high concentration. Equalize out amount of water molecules/concentration.

Question 11

Water Balance

Answer 11

Maintaining a balance of water. Hypertonic, Isotonic, and Hypotonic

Question 12

Turgid

Answer 12

Firm. More water inside than normal.

Question 13

Flaccid

Answer 13

The cell becomes limp, the plant wilts.

Question 14

Plasmolysis

Answer 14

Causes the plant (protoplast)to wilt and can lead to plant death. As the plant cell shrivels, its plasma membrane pulls away from the cell wall at multiple places, this phenomenon is called plasmolysis.

Question 15

Osmoregulation

Answer 15

Control of solute concentrations and water balance.

The maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations.

Question 16

Facilitated Diffusions

Answer 16

Many polar molecules and ions blocked by the lipid bilayer of the membrane diffuse passively with the help of transport(channel) proteins that span the membrane.

Question 17

Active Transport

Answer 17

Requires cellular energy. Usually pumps against its gradient.

Question 18

Active vs. Passive Transport

Answer 18

Active always require cellular energy, passive transport does not.

Question 19

Bulk Transport across Membrane

Answer 19

Large molecules such as proteins and p-saccharides, generally don’t cross the membrane by diffusion or transport proteins. Instead, they usually enter and leave the cell in bulk, packaged in vesicles.

Question 20

Proton pump

Answer 20

The main electrogenic pump of plants, fungi and bacteria. Actively transports protons (H+) out of the cell. Requires ATP.

Question 21

Cotransport: H+ and sugar

Answer 21

A transport protein (a cotransporter) can couple the “downhill” diffusion of the solute to the “uphill” transport of a second substance against its own concentration gradient.

Use ATP to get H+ out. Use cotransport to bring it back in with a glucose.

Question 22

Exocytosis

Answer 22

Cell secretes certain molecules by the fusion of vesicles with the plasma membrane. An active transport

Question 23

Endocytosis

Answer 23

The cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane. Active transport. Bulk

Question 24

Phagocytosis

Answer 24

Type of endocytosis. “Cellular eating.” A cell engulfs a particle by extending pseudopodia around it and packaging it within a membranous sac called a food vacuole.

Question 25

Pinocytosis

Answer 25

Type of endocytosis. Gulps droplets of extracellular fluid into tiny vesicles, formed by infoldings of the plasma membrane.

Question 26

Receptor-mediated endocytosis

Answer 26

A specialized type of pinocytosis that enables the cell to acquire bulk quantities of specific substances, even though those substances may not be very concentrated in the extracellular fluid(body fluid outside cell).

Question 27

Hypertonic Solution

Answer 27

If a red blood cell is added to a hypertonic solution, there is more water outside the cell, causing water to rush in to the blood cell

Question 28

Hypotonic Solution

Answer 28

If a red blood cell is added to a hypotonic solution, the water concentration will be less outside of the cell, causing water to rush out of the blood cell

Question 29

Isotonic solution

Answer 29

:)

Question 30

Lysis

Answer 30

Hypotonic solution outside of cell causes hemoLYSIS in a red blood cell

Question 31

Crenation

Answer 31

Hypertonic solution outside of cell causes crenation in a red blood cell.
Water rushes into the cell.

Question 32

Electrogenic pump

Answer 32

An ion pump that generates net flow of charge. An important example is the sodium-potassium exchange pump which transports two potassium ions into the cell for every three sodium ions transported out, a net outward current that makes the inside of the cell negative.

Question 33

Contractile Vacuoles

Answer 33

A vacuole in some protozoans(Protists) which expels excess liquid on contraction.