2.4 Membranes

Question 1

What is the current model of the membrane structure called?

Answer 1

fluid mosaic model

Question 2

What is the bilayer of the membrane structure?

Answer 2

the phospholipid bilayer

Question 3

What is the 3-carbon compound called in the phospholipid bilayer?

Answer 3

glycerol

Question 4

What are two of the carbons in the 3-carbon compound attached to?

Answer 4

non-polar fatty acids

Question 5

What is one of the carbons in the 3-carbon compound attached to?

Answer 5

highly polar organic alcohol group with a phosphate

Question 6

What are the hydrophilic ends?

Answer 6

alcohol-phosphate

Question 7

What are the hydrophobic ends?

Answer 7

fatty acids

Question 8

Which ways do the hydrophilic ends face?

Answer 8

outward

Question 9

Which way does the hydrophobic ends face?

Answer 9

inward

Question 10

Why does the membrane remain fluid and flexible?

Answer 10

Because the fatty acid ends are not attracted to one another

Question 11

What helps maintain the overall structure of the membrane?

Answer 11

Hydrogen bonds with water

Question 12

What are glycoproteins?

Answer 12

composed of carbohydrate chains attached to peripheral proteins; recognize like cells and are involved in immune response

Question 13

What are integral proteins?

Answer 13

completely penetrate lipid bilayer; control entry and removal of specific molecules

Question 14

What does the cholesterol do?

Answer 14

helps regulate membrane fluidity and stability

Question 15

composed of carbohydrate chains attached to peripheral proteins; recognize like cells and are involved in immune responsibility

Answer 15

glycoprotein

Question 16

completely penetrate lipid bilayer; control entry and removal of specific molecules

Answer 16

integral proteins

Question 17

helps regulate membrane fluidity and stability

Answer 17

cholesterol

Question 18

What are the six membrane protein functions?

Answer 18

Hormone binding sites Enzymatic Action Cell Adhesion Cell-to-Cell Communication Channels for Passive Transport Pumps for Active Transport

Question 19

What are the 3 types of passive transport?

Answer 19

diffusion, facilitated diffusion, and osmosis

Question 20

What is diffusion?

Answer 20

Particles moving from a region of high concentration to a region of low concentration

Question 21

What are 3 characteristics of facilitated diffusion?

Answer 21

Involves a carrier protein (non-channel protein) that helps carry substances across membrane Does NOT require energy Rate is dependent on number of carrier proteins available

Question 22

What is osmosis?

Answer 22

Movement of water across a partially permeable membrane to balance solute concentration

Question 23

What proteins does osmosis use?

Answer 23

aquaporins

Question 24

What are the 3 characteristics of a hypertonic solution(concentration, movement, and shape)?

Answer 24

Concentration of solutes is more outside the cell than inside Water flows out of cell The cell shrivels and becomes “flacid”.

Question 25

What are the 3 characteristics of a hypotonic solution(concentration, movement, and shape)?

Answer 25

Concentration of solutes is less outside the cell than in. Water flows in The cell swells with water, becomes “turgid”, and dies.

Question 26

What are the 3 characteristics of a isotonic solution(concentration, movement, and shape)?

Answer 26

Concentration is the same inside and out No net movement The cell stays the same

Question 27

What is water potential?

Answer 27

the tendency of water to leave one place in favor of another place

Question 28

How will water move?

Answer 28

Water will always move from and area of higher (less negative) water potential to an area of lower water potential (more negative).

Question 29

Compare big/polar and small/non-polar in which can cross the membrane passively?

Answer 29

It is difficult (not impossible) for large or polar molecules to cross membranes passively. It is relatively easy for smaller and non-polar molecules to cross membranes passively

Question 30

What are 2 characteristics of active transport(movement and requirement)?

Answer 30

Movement of substances against a concentration gradient Requires energy (ATP)

Question 31

What is step 1 of the sodium-potassium pump?

Answer 31

Specific protein binds to three intracellular sodium ions

Question 32

What is step 2 of the sodium-potassium pump?

Answer 32

Binding of sodium ions causes phosphorylation by ATP

Question 33

What is step 3 of the sodium-potassium pump?

Answer 33

Phosphorylation changes shape of protein, pushing sodium ions out of cell

Question 34

What is step 4 of the sodium-potassium pump?

Answer 34

Two extracellular potassium ions bind to a different part of protein, which causes release of phosphate group

Question 35

What is step 5 of the sodium-potassium pump?

Answer 35

Loss of phosphate group restores original shape causing release of potassium ions into cell

Question 36

What does endocytosis do?

Answer 36

Allows macromolecules to enter the cell

Question 37

When does endocytosis occur?

Answer 37

Occurs when portion of plasma membrane is “pinched” off to enclose a substance, forming a vesicle

Question 38

Where does the vesicle go in endocytosis?

Answer 38

This vesicle enters the cytoplasm and the substance makes its way where it is needed

Question 39

Why do the ends of the plasma membrane reattach after endocytosis?

Answer 39

Ends of the plasma membrane reattach because of the hydrophobic and hydrophilic properties of the phospholipids and the presence of water

Question 40

What is step 1 of exocytosis?

Answer 40

Protein produced by ribosomes of rough ER enters the lumen of the ER

Question 41

What is step 2 of exocytosis?

Answer 41

Protein exits ER and enters the cis side of the Golgi apparatus (vesicle is involved)

Question 42

What is step 3 of exocytosis?

Answer 42

As protein moves through the Golgi apparatus, it is modified and exits on the trans side inside a vesicle

Question 43

What is step 4 of exocytosis?

Answer 43

Vesicle with modified protein moves to membrane and fuses with it; contents are secreted out of cell

Question 44

What are the 4 parts of the membrane?

Answer 44

proteins, carbohydrates, lipids, and cholesterol

Question 45

What is number 1?

Answer 45

peripheral protein

Question 46

What is number 2?

Answer 46

phospholipid

Question 47

What is number 3?

Answer 47

tail

Question 48

What is number 4?

Answer 48

head

Question 49

What is number 5?

Answer 49

peripheral protein

Question 50

What is number 6?

Answer 50

channel protein (integral protein)

Question 51

What is number 7?

Answer 51

cholesterol

Question 52

What is number 8?

Answer 52

glycoprotein