Unit 3: Membranes

Question 1

Where are membranes found?

Answer 1

Around all cells (plasma membrane)
Around some eukaryotic organelles

Question 2

Membranes are primarily made of

(two types of large biological molecules)

Answer 2

Lipids
&
Proteins

Question 3

What lipids are found in membranes?

Answer 3

Phospholipids and cholesterol

Question 4

Two orientations for how proteins can be embedded in membranes

Answer 4

Peripheral (one side) or
Integral (through)

Question 5

Two faces of a membrane

Answer 5

Cytosolic (or cytoplasmic; toward inside of cell) and
Extracellular (toward environment)

Question 6

Structure of phospholipid

Answer 6

Phosphate-head, which is polar
Two lipid tails, which are nonpolar

Question 7

Hydrophilic

meaning

Answer 7

“Water loving”

Question 8

Hydrophilic substances are

Answer 8

Ionic or polar

Question 9

Hydrophobic

meaning

Answer 9

“Water fearing”

Question 10

Hydrophobic substances are

Answer 10

Nonpolar

Question 11

What would allow a protein to become embedded in a membrane?

Answer 11

Protein with some amino acids with hydrophobic R groups and some with hydrophilic R groups

Question 12

What part of a phospholipid is hydrophobic

Answer 12

Lipid tails

Question 13

What part of a phospholipid is hydrophilic

Answer 13

Phosphate head

Question 14

Phospholipid bilayer

Answer 14

Two layers of phospholipid
- Hydrophobic tails face inward
- Hydrophilic heads face cytosol or extracellular areas

Question 15

Fluid Mosaic Model

Answer 15

A description of cell membranes
Each phospholipid can move freely laterally
Embedded substances (proteins, etc) can also move laterally

Question 16

What factors affect membrane fluidity?

Answer 16

Temperature
Type of hydrocarbon (saturated v. unsaturated) tails in phospholipid
Amount of cholesterol

Question 17

Effect of temperature on membrane fluidity

Answer 17

Higher = more fluid
Lower = less fluid

Question 18

Effect of lipid type (in phospholipid) on membrane fluidity

Answer 18

Saturated fatty acid tails = fluid at higher temperatures
Unsaturated fatty acid tails = fluid at lower temperatures

Question 19

Role of cholesterol in cell membranes

Answer 19

Aids in membrane integrity and fluidity
At low temps - prevent solidification of membranes by preventing

Question 20

What determines the function of a membrane?

Answer 20

The proteins it has in it

Question 21

Define

Integral protein

Answer 21

Protein that goes all the way through the membrane (often transmembrane proteins)

Question 22

Define

Peripheral protein

Answer 22

Protein that is embedded only on cytoplasmic OR extracellular side of membrane

Question 23

List

Functions of membrane proteins

Answer 23

• Transporting materials into/out of cell
• Enzymes
• Cell signaling
• Cell-to-cell recognition
• Joining cells together (connections)
• Attachment to other proteins, such as the cytoskeleton or extracellular matrix

Question 24

Describe

Proteins that transport materials into / out of cell

Answer 24

Have polar amino acids in the center, forming a channel or carrier to connect cytosol and extracellular environment

Question 25

Benefit of having enzymes embedded in membrane

Answer 25

Keeps enzymes that are part of a single chemical pathway together

Ex: Rxn1: A–>B Rxn2: B–>C
Enzyme for Rxn 1&2 can be close

Question 26

What can membrane proteins attach to?

Answer 26

• Carbohydrates (makes glycoprotein)
• Cytoskeleton
• Extracellular matrix
• Other cells’ membrane proteins

Question 27

What part of the membrane is this?

Answer 27

Phospholipid

Question 28

What part of the membrane is this?

Answer 28

Phospholipid bilayer

Question 29

What part of the membrane is this?

Answer 29

Cholesterol

Question 30

What kind of molecule is this?

Answer 30

Glycolipid

Carbohydrates + Lipid

Question 31

What is this?

Answer 31

Integral / Transmembrane Protein

Integral: Embedded in membrane
Transmembrane: Spans whole width

Question 32

What is this?

Answer 32

Peripheral protein

Question 33

What is this? (specifically)

Answer 33

Phosphate head
OR
Hydrophilic head
OR
Phosphate portion of phospholipid

All are often used synonymously

Question 34

What is this? (specifically)

Answer 34

Lipid tail
OR
Hydrophobic tail
OR
Lipid portion of phospholipid

All are often used synonymously