module 1

Question 1

list structural elements of the cell membrane

Answer 1

lipids and proteins

Question 2

what is the model used to describe the cellular membrane

Answer 2

fluid mosaic model - membrane is a fluid with a “mosaic” of proteins embedded in it

Question 3

phospholipid bilayer components

Answer 3

made up of amphipathic molecules (hydrophilic head and hydrophobic tail)

Question 4

how is phospholipid bilayer fluid

Answer 4

• constantly moving due to (mostly) lateral movement and flip-flop
• kinks in hydrocarbon tails reduces viscosity

Question 5

role of cholesterol in cell membrane

Answer 5

changes composition of the phospholipid membrane (buffering portion)

Question 6

list 6 major functions of membrane proteins

Answer 6

• transport
• enzymatic activity
• signal transduction
• cell-cell recognition
• intercellular joining
• attachment to the cytoskeleton and extracellular matrix (ECM)

Question 7

describe how membrane structure results in selective permeability

Answer 7

• phospholipid bilayer= impermeable to most essential molecules and ions e.g. ions, hydrophilic molecules and macromolecules -> what is able to pass= lipid-soluble
• some permeability to water molecules and small uncharged molecules e.g. oxygen + carbon dioxide

Question 8

passive transport

Answer 8

• diffusion of a substance across a membrane
• no work + ATP required
• free movement
• goes along concentration gradient

Question 9

diffusion

Answer 9

passive net movement of particles from high concentration to low concentration that requires no work and occurs with time

Question 10

osmosis

Answer 10

diffusion of water through selectively permeable membrane from low to high solute concentration

Question 11

osmotic pressure

Answer 11

pressure to drive water towards non-permeable solutes

Question 12

osmotica

Answer 12

solutes that are osmotically active i.e. cannot cross membranes themselves
e.g. ions, sugars, proteins + nutrients

Question 13

isotonic solution

Answer 13

solute concentration = inside of cell; no net water movement (~300mOsm/L)

Question 14

hypotonic solution

Answer 14

solute concentration > inside of cell ; cell loses water/shrinks
(<300mOsm/L)

Question 15

hypertonic solution

Answer 15

solute concentration < inside of cell ; cell gains water/bursts
(>300mOsm/L)

Question 16

facilitated diffusion

Answer 16

• passive transport aided by proteins
• speeds up the passive movement of molecules across plasma membrane
• no ATP req
• provides passage for hydrophilic substances

Question 17

transport proteins for facilitated diffusion

Answer 17

• channel protein
• carrier/transport protein

Question 18

channel proteins

Answer 18

ligand-gated channels that open/close in response to a stimulus

Question 19

carrier/transport proteins

Answer 19

bind to molecules and change shape to shuttle across membrane

Question 20

active transport

Answer 20

• only carrier/transport proteins
• works against the concentration gradient
• req work + ATP

Question 21

electrogenic pump

Answer 21

transporter that generates voltage across a membrane

Question 22

sodium-potassium pump

Answer 22

major electrogenic pump of animal cell
creates negative voltage inside of the cell b/c 3 Na+ OUT, 2 K+ IN

Question 23

cotransport

Answer 23

coupled transport by a membrane protein - occurs when active transport of a solute indirectly drives transport of another solute e.g. Na+/K+-ATPase

Question 24

draw diagram of cotransport - sucrose and H+

Answer 24

Question 25

2 types of bulk transports across plasma membrane

Answer 25

- endocytosis - exocytosis

Question 26

endocytosis

Answer 26

bulk transport into cell - phagocytosis: engulfing particles - pinocytosis: drinking - receptor-mediated endocytosis

Question 27

exocytosis

Answer 27

exiting particles = packaged in vesicles to leave cell

Question 28

2 types of cell to cell communication

Answer 28

- local signaling - long-distance signaling

Question 29

local signaling

Answer 29

allows cell to communicate with immediate neighbours via short-range chemical messages or direct contact

Question 30

long distance signaling

Answer 30

signals produced by specialised cells and released into bloodstream -> carries to target cells in distant parts of body

Question 31

list and describe 3 stages of cell signalling

Answer 31

1. reception - signaling molecule binds to receptor 2. transduction - signal amplification via 3 relay molecules in a signal transduction pathway 3. response - activation of cellular response

Question 32

2 types of families of receptors

Answer 32

- plasma membrane receptors - intracellular receptors

Question 33

4 families of receptors

Answer 33

- ion channel receptors - G protein coupled receptors - receptor tyrosine kinases (RTK) - steroid receptors

Question 34

ion channel receptors

Answer 34

ligand-gated ion channel opening of channels -> lets ions in/out of the cell

Question 35

G protein-coupled receptors

Answer 35

- 7 TM-spanning regions - largest family - >1000 variations - most abundant - activated by variety of stimuli - interact with heterotrimetric G proteins to control enzyme activity, ion channels + intracellular signal transduction pathways

Question 36

draw and label diagram of GPCR communication (5 steps)

Answer 36

Question 37

receptor tyrosine kinases (TKR)

Answer 37

- responsible for metabolism, cell growth + cell reproduction - inactive monomers bind into dimers post signaling molecule -> activates tyrosine kinase regions and form "docking sites" for relay proteins - e.g. insulin receptors

Question 38

steroid receptors

Answer 38

crosses cell membrane of target cell and binds to intracellular receptors