chapter seven

Question 1

function of plasma membrane

Answer 1

• protects cell from external environment
• mediates cellular transport
• transmits cellular signals

Question 2

selective permeability

Answer 2

controlled flow of substances in/out of the cell
- some cross more easily than others

Question 3

staple ingredients of membranes

Answer 3

lipids and proteins

Question 4

phospholipid bilayers

Answer 4

hydrophilic head, hydrophobic tails
- 2 phospholipids held together by hydrophobic interactions

Question 5

amphipathic molecules

Answer 5

both polar and nonpolar

Question 6

fluid mosaic model

Answer 6

membrane is a mosaic of protein molecules bobbing in a fluid layer of phospholipids

Question 7

evidence for fluid nature of membrane

Answer 7

1. cell fusion (hybrid cell)
2. movement of proteins

Question 8

cell fusion (hybrid cell)

Answer 8

mouse and human cells fused, proteins on membranes mixed laterally

Question 9

movement of proteins

Answer 9

• shifts laterally (sideways)
• slower than lipid movement because larger
• many proteins immobile by attachment to cytoskeleton and ECM

Question 10

flip flops

Answer 10

lipid can switch from 1 phospholipid layer to another
- need flippers/floppers
- phospholipids can’t do on own

Question 11

unsaturated hydrocarbons

Answer 11

double bonds (kinked tails) prevent packing and enhance fluidity

Question 12

saturated hydrocarbons

Answer 12

hydrocarbon tails pack together and decrease fluidity

Question 13

cholesterol

Answer 13

effects membrane fluidity
- fluidity buffer - resists change
- high temp - membrane less fluid by restraining phospholipid movement
- lowers temp required for membrane to solidify

Question 14

2 types of membrane proteins

Answer 14

integral and peripheral

Question 15

integral proteins

Answer 15

penetrate hydrophobic interior of lipid bilayer
- includes transmembrane proteins (span membrane)
- hydrophobic regions consist of 1+ stretches of nonpolar amino acids coiled in a helices

Question 16

peripheral proteins

Answer 16

not embedded in lipid bilayer, loosely bound to surface

Question 17

ECM

Answer 17

non-cellular componente of tissues and organs
- contains macromolecules

Question 18

functions of membrane proteins

Answer 18

• transport
• enzymatic activity
• signal transduction
• cell-cell recognition
• intracellular joining
• attachment to cytoskeleton/ECM

Question 19

what does cell-cell recognition require?

Answer 19

one protein to be a glycoprotein

Question 20

importance of cell recognition

Answer 20

sorting of cells/tissues in embryo, rejection of foreign cells

Question 21

molecule structure of cell recognition

Answer 21

cells bind to molecules (often containing carbohydrates) on ec surface

Question 22

glycolipids

Answer 22

carbohydrates bonded covalently to lipids

Question 23

glycoproteins

Answer 23

carbohydrates covalently bonded to proteins

Question 24

what substances pass by “free” diffusion (passive)

Answer 24

• gases
• small greasy molecules (steroids, non polar substances, hormones)

Question 25

passive transport

Answer 25

diffusion that requires no energy and travels down the concentration gradient - gradient represents potential energy

Question 26

diffusion

Answer 26

movement of particles of any substance so they spread out into available space

Question 27

net movement

Answer 27

more movement in one direction, down concentration gradient for passive diffusion

Question 28

osmosis

Answer 28

diffusion of free water across selectively permeable membrane (artificial/cellular)

Question 29

salt sucks

Answer 29

solute (salt) will "suck" water towards it

Question 30

3 types of tonicity

Answer 30

hypertonic, hypotonic, isotonic

Question 31

hypertonic

Answer 31

concentration outside of cell greater so water leaves cell - cell shrivels and becomes crenated

Question 32

hypotonic

Answer 32

concentration inside of cell is greater, so water enters cell - cell swells and bursts

Question 33

isotonic

Answer 33

no net movement of water across membrane, same rate both directions

Question 34

osmoregulation

Answer 34

control of solute concentrations and water balance

Question 35

types of osmoregulation states

Answer 35

turgid, flaccid, plasmolyzed

Question 36

turgid

Answer 36

- very firm, healthy state for plants - cell swells w/ water by cell wall exerts pressure back (turgor pressure)

Question 37

flaccid

Answer 37

- when plant cells are isotonic - no water enters (limp)

Question 38

plasmolysis

Answer 38

if cell is in hypertonic environment, water lost to environment causes PM to pull away from cell wall

Question 39

plasmolyzed

Answer 39

shrunken plant cell membrane, inward/away from cell wall

Question 40

facilitated diffusion

Answer 40

polar molecules and ions diffuse with the help of transport proteins

Question 41

what are transport proteins specific for?

Answer 41

the substances they move

Question 42

2 types of proteins in facilitated diffusion

Answer 42

1. channel proteins 2. carrier proteins

Question 43

channel proteins

Answer 43

have hydrophilic channel that certain molecules/ions use as tunnel through membrane - ion channels - some function as gated channels in response to stimuli - aquoporins

Question 44

aquaporins

Answer 44

function to pass water molecules through membrane in certain cells

Question 45

carrier proteins

Answer 45

hold on to passengers and change shape in way that shuttles them across membrane

Question 46

active transport

Answer 46

pumping a solute across a membrane against the concentration gradient, uses energy from ATP hydrolysis - carrier proteins

Question 47

why is active transport necessary?

Answer 47

enables cell to maintain internal concentration of small solutes that differ from environment concentrations

Question 48

how does ATP activate active transport?

Answer 48

transfers terminal phosphate group to transport protein

Question 49

ex. of active transport

Answer 49

sodium-potassium pum, ion pump w. hydrogen ion concentration, cotransport

Question 50

sodium-potassium pump

Answer 50

exchanges Na+ for K+ across PM of animal cells

Question 51

membrane potential

Answer 51

voltage across membrane - inside of cell compared to outside

Question 52

ion pump that uses hydrogen ion concentration

Answer 52

electrogenic pump that transports protons (H+) out of cell and transfers + charge from cytoplasm to ec solution

Question 53

electrogenic pump

Answer 53

transport protein that generates voltage across membrane

Question 54

cotransport (H+ and sugar)

Answer 54

- transport protein couples downhill diffusion to uphill - transport of 2nd substance against own concentration gradient - (plant cell) gradient of H+ generated by ATP-powered protein pumps drive active transport of amino acids and sugars into cell

Question 55

2 types of bulk transport

Answer 55

exocytosis and endocytosis

Question 56

exocytosis

Answer 56

cell secretes certain molecules by fusion of vesicles with PM

Question 57

3 types of endocytosis

Answer 57

1. phagocytosis 2. pinocytosis 3. receptor-mediated endocytosis

Question 58

endocytosis

Answer 58

cell takes in molecules by forming vesicles w/ PM

Question 59

phagocytosis

Answer 59

engulfs/eats particle by extending pseudopodia around its and packaging it in food vacuole

Question 60

pinocytosis

Answer 60

gulps/drinks droplets of ec fluid, vesicles (tiny) formed by infolding of PM

Question 61

receptor-mediated endocytosis

Answer 61

special type of pinocytosis that enables cell to acquire bulk quantities of specific substances even if substances are concentrated in ec fluid

Question 62

oligosaccharide

Answer 62

short chain

Question 63

difference between cytoplasm and cytosol

Answer 63

- cytoplasm - includes organelles except nucleus - cytosol - just the liquid

Question 64

is bulk transport active or passive?

Answer 64

active

Question 65

what is a Na/K pump also called?

Answer 65

Na/K ATPase