Membrane

Question 1

phospholipid structure

Answer 1

amphipathic molecules that make up the bilayer of the plasma membrane and keep the membrane fluid
consist of a glycerol molecule, two nonpolar hydrophobic fatty acids, and a polar hydrophilic phosphate group

Question 2

cholesterol

Answer 2

embedded in phospholipid bilayer - resists changes in membrane fluidity

Question 3

glycolipid

Answer 3

lipid attached to carbohydrate on surface of membrane that aids in cell-to-cell recognition

Question 4

glycoprotein

Answer 4

protein attached to carbohydrate on the surface of membrane that serves as identification tag, aiding in cell-to-cell recognition

Question 5

integral protein

Answer 5

a transmembrane protein with the hydrophobic region extending into and often completely spanning the hydrophobic interior of the lipid bilayer. The hydrophilic regions are exposed to the aqueous solutions on either side of the membrane.
carry out transmembrane movement (ex, facilitated diffusion, active transport), intercellular joining, signal transduction

Question 6

peripheral protein

Answer 6

not embedded in the lipid bilayer and loosely bound to the membrane or to the exposed parts of integral proteins (ex. enzymes that carry out sequential steps of a metabolic pathway, cell communication, conduct signals from the exterior to the interior or vice versa)

Question 7

hydrophilic end of phospholipid

Answer 7

orientated outwards and exposed to water; polar phosphate head

Question 8

hydrophobic end of phospholipid

Answer 8

nonpolar fatty acid tails in nonaqueous environment

Question 9

cytoskeleton

Answer 9

maintain cell shape, rigidity, and structure

Question 10

lipid bilayer

Answer 10

through selective permeability, the passage of substances across the membrane is regulated (nutrients and solutes and transported in while waste products are eliminated); allows cell to maintain different solution than surrounding environment

Question 11

selective permeability: ions

Answer 11

no permeability because ions are charged

Question 12

selective permeability: large, polar biomolecules

Answer 12

some permeability with difficulty because of polarity and large size

Question 13

selective permeability: small, polar molecules

Answer 13

some permeability because of small size and polarity

Question 14

selective permeability: small, nonpolar molecules

Answer 14

high permeability because of non-polarity and small size

Question 15

Passive transport

Answer 15

Does not require energy: diffusion, osmosis, and facilitated diffusion

Question 16

diffusion

Answer 16

the tendency for molecules of any substance to spread out evenly into the available space; down the concentration gradient from an area of high to low concentration; spontaneous process

Question 17

facilitated diffusion

Answer 17

when a transport protein embedded in the membrane assists in the passive transport of polar molecules and ions impeded by the lipid bilayer

Question 18

active transport

Answer 18

the expenditure of energy (usually from ATP) to pump a molecule across a membrane against its concentration gradient

Question 19

protein pumps

Answer 19

The transfer of the terminal phosphate group of ATP to the transport protein powers active transport, inducing the protein to change its conformation, translocating a solute
ex. sodium potassium pump

Question 20

endocytosis

Answer 20

the transport of macromolecules and particulate matter into the cell through vesicles

Question 21

exocytosis

Answer 21

the transport of macromolecules out of the cell through the fusion of vesicles with the plasma membrane

Question 22

Factors that Affect Fluidity

Answer 22

temperature, saturated v unsaturated tails, cholesterol

Question 23

How does temperature affect fluidity?

Answer 23

As temperature decreases so does membrane fluidity and permeability until solidification occurs
As temperature increases, membrane fluidity and permeability increases until disassociation occurs

Question 24

How does saturated v unsaturated tails affect fluidity?

Answer 24

Phospholipids with unsaturated hydrocarbon tails will remain fluid at lower temperatures because of kink caused by double bond- decreases chance of solidification
In phospholipids with saturated hydrocarbon tails, fluidity decreases because of the absence of double bonds/kinks and the chance of solidification increases.

Question 25

How does cholesterol affect fluidity?

Answer 25

Cholesterol between phospholipids acts as a temperature buffer
• Prevents solidification at low temperatures
• Restrains fluidity at body temperature

Question 26

Membrane Protein Functions

Answer 26

Transport
• Enzymatic Activity
• Signal Transduction
• Cell-cell recognition
– Glycoproteins and
glycolipids
• Intercellular joining
• Attachment to
cytoskeleton &
extracellular matrix

Question 27

Transport

Answer 27

provides hydrophilic channel that allows molecules to pass through cell membrane that otherwise could not
- passive (facilitated) and active (protein pump) transport

Question 28

Enzymatic Activity

Answer 28

proteins are embedded in the sequence of the metabolic pathway, increasing efficiency and productivity

Question 29

Signal Transduction

Answer 29

protein receptor binds to chemical messenger; the signal may cause the conformational change in the protein (receptor) that relays the message to the inside of the cell

Question 30

Cell to Cell recognition

Answer 30

glycoproteins and glycolipids act as markers that indicate information to surrounding cells
ex. blood type

Question 31

Intercellular Joining

Answer 31

proteins of adjacent cells hook/join together

Question 32

Attachment to cytoskeleton and ECM

Answer 32

microfilaments of cytoskeleton bond to proteins, maintaining cell shape
protein attaches to extracellular matrix to stabilize location of certain membrane proteins

Question 33

Surface Area to Volume

Answer 33

volume increases at a greater rate than surface area

a greater surface area to volume ratio is ideal for efficient transport of solutes, nutrients,and elimination of waste

Question 34

Why are animal cells basically spherical whereas plants and fungi are filmentous?

Answer 34

Animals are comprised of specialized organ systems dedicated to the transport of substances throughout the body, so a greater SA/V ratio is not necessary. In plants, the xylem (water & solutes) and phloem (sugars), transport substances. In fungi, there is greater need for larger SA/V ratio because all environmental interaction is with soil, which fungi are entirely dependent on for nutrients and waste storage.

Question 35

Water Potential

Answer 35

A property that predicts the direction of water flow based on solute concentration & physical pressure (measured in bar or Mpa)

Question 36

Water moves from _____ to _____, so water will move towards the more ________
water potential

Answer 36

high; low

negative

Question 37

pure water has Ψ of

Answer 37

0

Question 38

at standard atmospheric pressure Ψ of hypertonic is __ Ψ of hypotonic solution so net movement is __________ → __________

Answer 38

Ψ of hypertonic
is < Ψ of hypotonic solution
hypotonic → hypertonic

Question 39

equation for water potential

Answer 39

Ψ= Ψs + Ψp

Question 40

Ψs

Answer 40

water movement is influenced by the solute concentration on either side (always -)
• Proportional to the amount of dissolved solute
• As solutes are added the Ψs decreases because solute molecules are binding with water as solutes dissolves and water forms hydration shells, preventing it from doing work (free water)

Question 41

Ψp

Answer 41

water movement is directly proportional to pressure (maybe be +,-,0)
• Pressure potential is the physical pressure on a solution
if pressure is applied, Ψp increases, if no pressure, Ψp=0, if pressure is decreased (more volume), Ψp decreases

Question 42

how to calculate solute potential

Answer 42

Ψs = -iCRT
i: ionization constant (1 for sucrose, 2 for NaCl)
• C: concentration in moles/L (molarity)
• R: pressure constant (0.0831)
• T: temperature in Kelvin

Question 43

Electrochemical Gradient

Answer 43

The different gradient of an ion across a membrane
– Cytoplasm is negative compared to the extracellular fluid so cations (+) move in and anions (-) out
Each positive charge removed from cytoplasm is stored energy as voltage
-chemical force (ion’s concentration gradient) and electrical force (effect of membrane potential on the ion’s movement)

Question 44

electrogenic pumps

Answer 44

proteins that generate voltage across a membrane (Na+/K+ pumps in animals; 3Na+ out, 2K+ in)

Question 45

Proton pumps

Answer 45

actively transport H+

ions out of the cell (in plants, fungi, & bacteria)

Question 46

Cotransport

Answer 46

A pump transports a molecule that drives the active transport of others
• The cotransporter protein couples diffusion of a pumped substance to the transport of a second substance up the concentration gradient
• Example: Sucrose-H+
transporter

Question 47

Types of Endocytosis

Answer 47

phagocytosis, pinocytosis, receptor-mediated endocytosis

all are bulk transport

Question 48

phagocytosis

Answer 48

cell eating

cell engulfs a particle collecting food which is digested by lysosome

Question 49

pinocytosis

Answer 49

cell drinking
cell gulps droplets of extracellular fluid
• Non specific type of transport

Question 50

receptor-mediated endocytosis

Answer 50

cell acquires bulk quantities of a specific substance

• Ligands attaches to receptors inducing vesicle creation