Chapter 7: Membrane Structure and Function

Question 1

selective permeability

Answer 1

a property of biological membranes that allows them to regulate the passage of substances across them

Question 2

amphipathic

Answer 2

having hydrophilic and hydrophobic regions

Question 3

fluid mosaic model

Answer 3

membrane is a mosaic of protein molecule in a fluid bilayer of phospholipids

Question 4

peripheral proteins

Answer 4

protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer

Question 5

integral proteins

Answer 5

a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein)

Question 6

transport proteins

Answer 6

a transmembrane protein that helps only a certain substance or class of closely relates substances to cross the membrane

Question 7

transmembrane proteins

Answer 7

proteins that span the membrane, hydrophobic

Question 8

enzymatic proteins

Answer 8

a protein built into the membrane with its active site exposed to substances in the solution

Question 9

signal transduction proteins

Answer 9

a receptor protein with a binding site (specific shape) that fits a chemical messenger, like a hormone. The signaling molecule (messenger) may change the proteins shape to allow it to relay the message to inside the cell by binding to a cytoplasmic protein

Question 10

cell recognition protein

Answer 10

some glycoproteins serve as id tags that are recognized by membrane proteins of other cells. short- bond

Question 11

intercellular joining

Answer 11

membrane proteins hook in various junctions (gap junction, tight junction) long lasting bond

Question 12

cytoskeleton attachment proteins

Answer 12

microfilaments or other elements

• noncovalently bound to membrane proteins
• helps maintain cell shape
• stabilizes the location of certain membrane proteins.
• coordinate extracellular and intercellular changes

Question 13

glycolipids

Answer 13

membrane carbohydrates covalently bonded to lipids, used in cell-to-cell recognition

Question 14

glycoproteins

Answer 14

membrane carbohydrate covalently bonded to a protein, used in cell-to-cell recognition

Question 15

aquaporins

Answer 15

channel protein responsible for the passage of water through a cell allows 3Billion (3x 10^9) water molecules per second!

Question 16

passive membrane transport (passive transport)

Answer 16

diffusion of a substance across a membrane, doesnt use energy

Question 17

diffusion

Answer 17

movement of particles from an area of high concentration to an area of low concentration. move down the concentration gradient

Question 18

osmosis

Answer 18

diffusion of water across a selectively permeable membrane

Question 19

equilibrium

Answer 19

TBA

Question 20

Tonicity

Answer 20

the ability of a surrounding solution to cause a cell to gain or lose water

Question 21

hypertonic

Answer 21

hypertonic means there are more solutes inside the cell than in the surrounding solution, the cell will lose solutes in the diffusion, causing the cell to shrivel

Question 22

hypotonic

Answer 22

there are fewer solutes inside the cell than in the surrounding solution, the cell will gain solutes in the diffusion process, causing the cell to rupture due to overload of fluid

Question 23

turgid

Answer 23

very firm, due to turgor pressure

Question 24

flaccid

Answer 24

limp, due to less turgor

Question 25

plasmolysis

Answer 25

in a hypertonic environment, water leaves the plant cell causing the plasmamembrane to pull away from the cell wall

Question 26

facilitated diffusion

Answer 26

passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure

Question 27

ion channels

Answer 27

trans membrane channel that allows a specific ion to diffuse across the membrane, down its concentration gradient

Question 28

gated channels

Answer 28

transmembrane channel that opens and closes in response to specific stimuli

Question 29

carrier proteins

Answer 29

alternates between two shapes, moving a solute across the membrane during the shape change

Question 30

active transport

Answer 30

moves solutes against their concentration gradient, made possible by carrier proteins only (not channel), expends energy

Question 31

sodium-potassium transport pump

Answer 31

exchanges sodium for potassium across the plasma membrane, active transport.

outside cell: high NA+, low K+
inside cell: high K+, low NA+

Moves 2 K+ in for every 3 NA+ out

Question 32

membrane potential

Answer 32

voltage across a membrane (-50 - -200 milliVolts).
Cytoplasmic side if negative and extracellular side is positive due to an inbalance of anions and cations on both sides of the cell

Question 33

electrochemical gradient

Answer 33

combination of electrical force (membrane potential’s effect on ion’s movement) and chemical force (concentration gradient) acting on an ion

Question 34

electrogenic pump

Answer 34

transport protein that generates voltage accross a membrane

Question 35

proton pump

Answer 35

main electrogenic pump in plants, animal, and bacteria that actively transports protons (H+ ions) out of the cell

Question 36

cotransport protein

Answer 36

uses the downhill diffusion of a solute to facilitate and drive the uphill/active transport of a second substance

Question 37

exocytosis

Answer 37

vesicles fuse with the plasma membrane emptying the contents of the vesicle out of the cell

Question 38

endocytosis

Answer 38

cell takes in molecules by making vesicles out of the plasma membrane

Question 39

Pinocytosis

Answer 39

cell continually gulps droplets of ECF into tiny vesicles (the cell obtains molecules dissolved in the fluid)

Question 40

phagocytosis

Answer 40

cell engulfs (eats) a particle by extending pseudopodia around it and packaging it within a food vacuole

Question 41

receptor-mediated endocytosis

Answer 41

type of pinocytosis that enables the cell to swallow bulk quantities of specific substances, even if not very concentrated in the ECF. Receptors bind with solutes and the cell forms vesicles around them.

Question 42

describe the fluid mosaic model that describes the cell membrane

Answer 42

The membrane is a mosaic of proteins floating in a fluid bilayer of phospholipids. Due to the amphipathic nature of proteins are able to make contact with the ECF and the cytosol. Protein distribution not random. Form long-lasting patches to carry out common functions. Phospholipids shift sideways and trade spots a lot.

Question 43

List and define the functions of membrane proteins

Answer 43

Integral proteins:
Peripheral Proteins:

Transport
Enzymatic
Signal transduction (receptor)
Cell-cell recognition
intercellular joining
Attachment to cytoskeleton and ECM

Question 44

List and define the functions of membrane proteins

Answer 44

Integral proteins:
Peripheral Proteins:

Transport
Enzymatic
Signal transduction (receptor)
Cell-cell recognition
intercellular joining
Attachment to cytoskeleton and ECM

Question 45

Explain how the ER an Golgi Apparatus create cell membrane while keeping distinct exterior and interior faces

Answer 45

Look at video in notes. Do not understand.

Question 46

DIscuss how plant cells and animal cells differ in their tonicity

Answer 46

Animal cells require an isotonic state. If placed in a hypertonic solution, water will rapidly leave the cell causing it to shrivel and die. In a hypotonic solution, water will rapidly enter the cell, causing it to burst.

Plant cells require a hypotonic state. Plant cells have turgor pressure, the back pressure from water rapidly entering the cell, making the plant firm. If placed in an isotonic solution, the plant will become flaccid because there will be no turgor pressure. If placed in a hypertonic solution, the plasma membrane will separate from the cell wall and collapse, plasmolysis.

Question 47

discuss th differences between passive and active transport

Answer 47

Simply put, active transport requires work/energy to move a substance up* the concentration gradient.
Passive transport, moving down* the concentration gradient, includes diffusion, osmosis, facilitated diffusion (passive transport aided by channel and carrier proteins).
Active transport exclusively uses carrier proteins to move up the concentration gradient. This requires energy from ATP hydrolysis. Cell maintains internal concentrations of small solutes that differ from external concentrations (does not use tonicity). Examples include: Sodium-Potassium Pump, ion pumps, cotransport.

Question 48

Differences and Similarities among the bulk transport processes or exocytosis and endocytosis.

Answer 48

Similarities:
Vesicles are used to transport materials in and out of the cell
Use the plasma membrane to make or break vesicles
Require energy.

Differences:
Exocytosis- secretion of molecules out of the cell via vesicles
Vesicle makes contact with plasma membrane. Plasma membrane turns vesicle into extension of membrane, contents dump out of cell.

Endocytosis- taking in molecules by forming new vesicles from the plasma membrane (PM)

• Phagocytosis: cell eats big particles in the ECF by forming a membrane around particle, forms food vacuoles
• Pinocytosis: cell sips droplets of ECF continually to absorb molecules that got dissolved in the droplets, make vesicles around droplets from PM
• Receptor mediated Endocytosis: receptors bind to molecules that get coated by a vesicle and become part of the cell