Introduction to Membranes

Question 1

How can phospholipids spontaneously form membranes?

Answer 1

Through their amphipathic nature

Question 2

How is a micelle formed with phospholipids?

Answer 2

Forms because single-tailed phospholipids are conical and their amphipathic nature

Question 3

Describe phospholipid movement within a bilayer.

Answer 3

Can move freely laterally and quickly

Flip/Flop movement is rare because the polar head is unstable in a hydrophobic environment

Question 4

What are some effects of high temperatures on the phospholipid bilayer?

Answer 4

Kinetic energy is increased to cause increased flexibility and permeability and creates gaps between phospholipids

Question 5

What are some adaptations to high heat on phospholipid bilayers?

Answer 5

i) increase in hydrocarbon tail length
ii) decrease in C=C to increase saturation
iii) increase in cholesterol to increase hydrophobicity and create a pylon to slow down phospholipids

Question 6

What are some effects of low temperatures on the phospholipid bilayer?

Answer 6

Space between phospholipids decreases to cause decreased flexibility and permeability

Question 7

What are some adaptations to low heat on phospholipid bilayers?

Answer 7

i) increase C=C to decrease saturation to make molecules larger
ii) decrease hydrocarbon tail length to decrease hydrophobicity
iii) add cholesterol to act as a spacer between phospholipids

Question 8

What are two types of proteins embedded into the membrane bilayer?

Answer 8

Integral membrane protein and peripheral membrane protein

Question 9

What defines a substance that can freely diffuse across a phospholipid bilayer?

Answer 9

Permeable

Question 10

What is impermeable?

Answer 10

A substance that cannot cross the hydrophobic core because it’s either too large or charged

Question 11

What are the rankings of CO2, glucose and ions from most permeable to least permeable?

Answer 11

CO2
Glucose
Ions

Question 12

Why can ions not cross the plasma membrane?

Answer 12

They cannot cross because of a hydration shell of H2O that surrounds the ion due to polarity

Question 13

What is the movement of molecules from a high concentration to a low concentration?

Answer 13

Diffusion (Passive Transport)

Question 14

What type of solution is a cell in when the solute concentration is higher within the cell than in the solution?

Answer 14

Hypotonic solution

Question 15

What are the risks of a cell being in a hypotonic solution?

Answer 15

Can cause osmotic lysis

Question 16

Describe an isotonic solution.

Answer 16

In an isotonic solution, the concentration of solute is equal inside and outside of the cell

Question 17

What type of solution is when the concentration of solute is higher outside of a cell?

Answer 17

Hypertonic solution

Question 18

What are the risks to a cell in a hypertonic solution?

Answer 18

Plasmolysis may occur

Question 19

What is plasmolysis?

Answer 19

The cell shrinks as water goes to the outside of the cell

Question 20

What form of transport describes molecules moving down their concentration gradient using channel proteins or carrier proteins?

Answer 20

Facilitated diffusion

Question 21

What is a channel protein?

Answer 21

Protein that allows transport of specific solutes without changing shape

Question 22

What is a carrier protein?

Answer 22

Protein that allows transport of specific solutes by changing shape

Question 23

What type of transport requires energy?

Answer 23

Active transport

Question 24

What is the transportation of molecules up their concentration gradient using energy?

Answer 24

Active transport

Question 25

What are the three functions of active transport?

Answer 25

i) to concentrate nutrients in the cell ii) to expel wastes iii) to maintain a voltage/chemical gradient

Question 26

Describe the process of a Sodium/Potassium pump.

Answer 26

i) 3 Na+ bind to a pump from within the cell ii) ATP provides energy for the protein to change shape iii) 3 Na+ are released extracellularly iv) 2 K+ bind to the pump from outside the cell v) ATP provides energy for the protein to change shape vi) 2 K+ are released intracellularly

Question 27

What is the role of an electrogenic pump?

Answer 27

It generates a voltage difference across the membrane

Question 28

What is the electric function of the Na/K pump?

Answer 28

To maintain a charge difference across the membrane called membrane potential which gives an electrochemical gradient

Question 29

What is membrane potential?

Answer 29

A charge difference across the membrane

Question 30

What is an electrochemical gradient?

Answer 30

There is a difference in concentration of a charged molecule across the membrane

Question 31

What is cotransport?

Answer 31

The transport of 2 molecules simultaneously

Question 32

How is Na/K pump an example of cotransport?

Answer 32

2K+ come into the cell down both electro and chemical gradients and 3Na+ go out of the cell down concentration gradient but against a charge

Question 33

What is an antiporter?

Answer 33

The transport of 2 molecules in different directions

Question 34

What is a symport?

Answer 34

The transport of 2 molecules in the same direction

Question 35

Describe the Na/Glucose cotransporter.

Answer 35

Na+ flows down its gradient into the cell but takes glucose with it into the cell (glucose against concentration gradient)

Question 36

What is coupled transport?

Answer 36

The use of one gradient to establish another

Question 37

What are the two types of bulk transport?

Answer 37

Endo and exocytosis

Question 38

What describes bulk transport going out of the cell?

Answer 38

Exocytosis

Question 39

Describe the process of exocytosis.

Answer 39

i) sorted material from Golgi ii) vesicle forms around material to be exocytosed iii) vesicle fuses with membrane iv) secretion of material

Question 40

What is a small membrane-bound compartment that contains cargo in a cell?

Answer 40

Vesicle

Question 41

What is endocytosis?

Answer 41

Bulk transport going into the cell

Question 42

What is phagocytosis?

Answer 42

Bulk transport of non-specific material into the cell

Question 43

Describe the process of endocytosis.

Answer 43

i) material comes to the plasma membrane ii) vesicle forms around the material at membrane iii) vesicle is transported to the lysosome iv) lysosome digests the material

Question 44

What is Receptor-Mediated Endocytosis?

Answer 44

Endocytosis of a specific ligand

Question 45

What is a ligand?

Answer 45

Anything that binds to a receptor

Question 46

What is a receptor?

Answer 46

An integral membrane protein that recognizes and binds a specific ligand

Question 47

Describe Receptor-Mediated Endocytosis.

Answer 47

i) ligand approaches receptor in a clathrin-coated pit ii) ligand binds to its specific receptor iii) a receptor circled vesicle forms carrying ligand iv) lysosome digests ligand v) receptors are recycled