Chapter 7: Membrane Structure and Function

Question 1

Two types of cellular membrane proteins

Answer 1

Integral (transmembrane)

Peripheral (does not go through the bilayer

Question 2

Amphipathic molecules?

Answer 2

Hydrophobic and hydrophilic components

Question 3

Describe the movement of phospholipids across the membrane

Answer 3

Phospholipids in the plasma membrane can mice within the bilayer
Most lipids and some proteins drift laterally
Rarely do they flip flop transversely across the membrane

Question 4

Do proteins move in the membrane?

Answer 4

Some drift within the bilayer
Move slower than lipids
Some moved by motor proteins in the cytoskeleton
Some never move and are anchored by The cytoskeleton

Question 5

Cholesterol regulates the ___________ of a membrane

Answer 5

Fluidity

Cholesterol wedges between plasma membrane of animal cells

Question 6

Two types of membrane proteins

Answer 6

Peripheral proteins- loosely bound, cytoplasmic side and exterior side
Integral proteins- within the membrane

Question 7

Proteins that have a hydrophobic and hydrophilic regions, transmembrane proteins

Answer 7

Integral proteins

Question 8

Covalent attachments of a lipid to an amino acid side chain within a protein

Answer 8

Lipid-anchored proteins

Question 9

Six major functions of membrane proteins??

Answer 9

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

Question 10

Cells recognize each other by binding to surface molecules, often ___________, on the plasma membrane

Answer 10

Carbohydrates

Also glycolipids, glycoproteins, usually branched oligosaccharides with fewer than 15 sugar units

Question 11

The asymmetrical distribution of proteins, lipids and associated carbohydrates in the plasma membrane is determined when the membrane is built by the _________________

Answer 11

ER and Golgi apparatus

Question 12

What can pass through the plasma membrane rapidly, dissolve in the lipid bilayer?

Answer 12

Hydrophobic (nonpolar) molecules and gasses

Question 13

What does not pass through the plasma membrane easily? Mostly transported through transport proteins

Answer 13

Hydrophilic/ polar molecules

Question 14

What diffuses slowly across the PM?

Answer 14

Ions

Question 15

Water enters through the plasma membrane though….

Answer 15

Aquaporins

Question 16

What allows the passage of hydrophilic substances or certain ions across the membrane?

Answer 16

Transport proteins

Question 17

• bind to molecules and change shape to shuttle them across the membrane
• specific for the substances it moves
• how sugar is brought in

Answer 17

Carrier proteins

Question 18

Does facilitated transport require energy?

Answer 18

No

Question 19

With diffusion each substance diffuse ________ their concentration gradient

Answer 19

Down

Question 20

Water diffuses across a membrane from a region of ________ solute concentration to region of ________ solute concentration

Answer 20

Lower, higher

Question 21

The ability of a solution to cause a cell to gain or lose water

Answer 21

Tonicity

Question 22

When cells with walls are in a hypotonic they become….

Answer 22

Turgid(from) this is normal for plants

Question 23

When plants are in a isotonic solution they are…..

Answer 23

Flaccid (limp)- the plant may wilt

Question 24

When a plant cell is in a hypertonic solution what happens?

Answer 24

Plasmolysis - membrane pulls away from the wall, usually lethal

Question 25

What kind of transport always goes from high to low concentrations

Answer 25

Passive

Facilitated transport is passive but needs proteins

Question 26

Corridors that allow a specific molecule or ion to cross the membrane (some are gated)

Energy is not required, molecules follow their concentration gradient

Answer 26

Channel proteins type of facilitated diffusion

Question 27

Undergo a subtle change in shape that translocates the solute-binding site across the membrane

Energy is not required, molecules follow their concentration gradient

Answer 27

Carrier proteins type of facilitated diffusion

Question 28

Sodium-potassium pumps create what type of gradient?

Answer 28

Electrochemical

Question 29

With sodium-potassium pumps, _____ K+ goes ______ the cell and _____NA+ goes _____the cell

Inside the cell the charge is _________
Outside the cell the charge is _______

Answer 29

2, into
3, out

Negative, positive

Question 30

What is membrane potential

Answer 30

The voltage difference across a membrane

Question 31

What is the main electrogenic pump of plants, fungi, and bacteria?

Answer 31

Proton pump

Question 32

Transport protein that generates the voltage across the membrane

Answer 32

Electrogenic pump

Question 33

What is the difference between primary and secondary active transport?

Answer 33

Primary directly uses energy to transport solute, secondary uses pre-existing gradient to drive transport of solute

Question 34

Occurs when active transport of a solute indirectly drives transport of another solute
Ex: plants commonly use the gradient of hydrogen ions generated by proton pumps to drive active transport of nutrients into the cell

Answer 34

Cotransport: coupled transport

Uniport
Symptoport (both of the same direction)
Antiport (go in opposite directions)

Question 35

Large molecules, such as polysaccharides and proteins, cross the membrane via _______

Answer 35

Vesicles

Question 36

• transport vesicles migrate to the membrane, fuse with it, and release their contents
• many secretory cells use this to export their products
• energy is required

Answer 36

Exocytosis

Question 37

Liquids or solids are taken up by the cell by invagination of the plasma membrane
Requires energy

Answer 37

Endocytosis

Question 38

“Cellular eating”

Cell engulfs particles in a vacuole

Answer 38

Phagocytosis

Type of endocytosis

Question 39

Cellular drinking

Cell creates vesicle around fluid

Answer 39

Pinocytosis

Type of endocytosis

Question 40

Binding of ligands to receptors triggers vesicle formation ex: cholesterol

Answer 40

Receptor-mediated endocytosis