Unit 1 - Cell Membrane

Question 1

Cell Membrane

Answer 1

separates inside of the cell from the extracellular fluid
- double layer
- thin barrier = less than 10nm thick

Question 2

What does the cell membrane control + made of what

Answer 2

traffic in and out of the cell
- selectively permeable
- allows some substance to cross easier then others
Phospholipids and proteins

Question 3

Non-polar mol

Answer 3

r able to diffuse readily across the cell membrane

Question 4

Small an uncharged polar mol

Answer 4

can also diffuse into cell

Question 5

Large polar or charged mols

Answer 5

CANNOT diffuse through the membrane on its own

Question 6

Fluid Mosaic Model idea and who discovered it

Answer 6

• Jonathan Singer and Garth Nicolson in 1972
• the idea that a biological membrane consists of a fluid phospholipid bilayer, in which proteins r embedded and float freely

Question 7

Fluid (fluid mosaic model)

Answer 7

Dynamic due to week intermolecular force between lipids. Lipids and proteins mol r generally free to move withing 2 layers

Question 8

Mosaic (fluid mosaic model)

Answer 8

wide assortment of proteins

Question 9

Phospholipids

Answer 9

arrange themselves into a bilayer structure due to properties (Amphiphilic) withing fatty acid tails and heads
= spontaneously in aqueous environments

Question 10

Fluid

Answer 10

lipid mol may vibrate/flex back and forth, spin around their long axis, move sideways and exchange places within bilayer.

Question 11

Glycolipids

Answer 11

• carb chains attached to phospholipids
• serve as recognition sites for other mol and join cells to form tissues
• cellular recognition and interaction
  ie. A, B, O blood groups = antigens
  Oligosaccharide attached to Lipid

Question 12

Glycoprotein

Answer 12

• Carb chain attache to the protein
• serve as markers for anchors to other internal structures like the cytoskeleton
• structural support, cell recognition
  ie. musins (mucus production) or antibodies (immune system)

Question 13

Factors affecting Membrane Fluidity

Answer 13

the dynamic nature of the lipid bilayer dependent on how densely the individual lipid mol can back together . must be fluid and flexible as thick salad oil
a) temp
b) fatty acid tails
c) fatty acid tail length

Question 14

Temp (membrane fluidity)

Answer 14

high temp = bilayer bc increasingly more fluid and is no longer semi permeable
low temp = cell membrane bc solid

Question 15

Fatty acid tails (membrane fluidity)

Answer 15

fatty acids composed of saturated hydrocarbons = straight shape can pack together tight.
unsaturated hydrocarbons = more loosely packed

Question 16

Fatty acid tails length (membrane fluidity)

Answer 16

the longer the fatty acid tail of the phospholipid, then more intermolecular interactions with surrounding mol the more stable the membrane

Question 17

Fluidity Cholesterol

Answer 17

• rigidity and allows cell membrane to function properly at a range of temp
• prevents cell death by maintaining structure of membrane
• in plants sterols

Question 18

Fluidity Cholesterol (high vs low temp)

Answer 18

high= cholesterol stabilizes the membrane (less fluid)
low= cholesterol prevents close packing of phospholipids (prevents membrane from freezing)

Question 19

Membrane Proteins

Answer 19

integral membrane protein
- all contain at least one region that interacts w hydeophobic core
- most cross membrane (transmembrane)
ie. insulin receptors

Question 20

Permanent

Answer 20

a protein that is embedded in lipid bilayer

Question 21

Transmembrane

Answer 21

protein are easy to identify bc they have a segment of non-polar amino acids that r hydrophobic and anchor and stay within the membrane, as well as polar hydrophilic regions that extend into the extracellular fluid and cytosol

Question 22

Peripheral Membrane Protein

Answer 22

temporary a loosely bound protein on surface of membrane
- noncovalent bonds (hydrogen bonds and ionic bond)
- usually found in cytosol
Ie. cytochrome c in electron transport chain

Question 23

Integral Proteins vs Peripheral Proteins

Answer 23

found embedded in lipid bilayer vs found in the periphery of the lipid bilayer

Question 24

Functions of Membrane Proteins

Answer 24

• Transport
• Enzyme activity
• Cell surface receptor
• Cell surface identity marker
• Cell adhesion
• Attachment to the cytoskeleton

Question 25

Role of Membrane Proteins

Answer 25

Can be separated into 4 categories
a) transport
b) enzymatic activity
c) triggering signals
d) attachment and recognition

Question 26

Transport

Answer 26

many substances cannot freely diffuse through membranes. instead, some compounds require a specific hydophilic protein channel. alternatively some proteins change shaoe to shuttle mol from one side to another

Question 27

Enzymatic activity

Answer 27

proteins act as enzymes to perform chemical rxn

Question 28

Triggering signals

Answer 28

membrane proteins may bind to specific mol (hormones) binding to these chemical triggers changes on the inner surface of the membrane starting a cascade of events within the cell

Question 29

Attachment and recognition

Answer 29

proteins exposed to both the internal and external membrane surfaces act as attachment points fro cytoskeleton elements as well as components involved in cell recognition and bond to extracellular matrix