Lecture 2b: Cell Membrane Transport

Question 1

Factors that determine how a substance may be transported across a plasma membrane:

Answer 1

(1) Size
(2) Polarity
(3) Charge

Question 2

Why is diffusion important to cells and humans?

Answer 2

• Cell respiration
• Alveoli of lungs
• Capillaries
• Red Blood Cells
• Medications: time release capsules

Question 3

Diffusion through protein channels which do not interact with hydrophobic interior

Answer 3

Facilitated Diffusion

Question 4

Molecules able to undergo passive diffusion

Answer 4

• Gases (oxygen, carbon dioxide)
• Water molecules (rate slow due to polarity)
• Lipids (steroid hormones)
• Lipid soluble molecules (hydrocarbons, alcohols, some vitamins)
  *Small noncharged molecules (NH3)

Question 5

Molecules undergoing facilitated diffusion

Answer 5

• Ions (Na+, K+, Cl-)
• Sugars (Glucose)
• Amino Acids
• Small water soluble molecules
• Water (faster rate)

Question 6

provide corridors allowing water molecules to cross the membrane in massive amounts

Answer 6

Aquaporins

Question 7

The diffusion of water across a differentially
permeable membrane

Answer 7

Osmosis

Question 8

The pressure that develops in a system due to osmosis

Answer 8

Osmotic Pressure

Question 9

more solute, less water

Answer 9

Hypertonic

Question 10

less solute, more water

Answer 10

Hypotonic

Question 11

equal solute, equal water

Answer 11

Isotonic

Question 12

What happens to an animal cell when placed in freshwater?

Answer 12

Undergoes lysis

Question 13

What happens to an animal cell when placed in saltwater?

Answer 13

Becomes shriveled

Question 14

What happens to a plant cell when placed in freshwater?

Answer 14

Turgid (normal)

Question 15

What happens to a plant cell when placed in saltwater?

Answer 15

Plasmolyzed

Question 16

What happens to a plant cell when placed in balanced solution?

Answer 16

Flaccid

Question 17

Organelle that pumps water out of the cell; found in Paramecium

Answer 17

Contractile vacuole

Question 18

permit the free passage of ions and small polar molecules through the outer membranes of bacteria.

Answer 18

Porins

Question 19

mediate the passage of ions across plasma membranes

Answer 19

Ion Channels

Question 20

Open in response to the binding of neurotransmitters or other signaling molecules

Answer 20

Ligand-gated Channels

Question 21

Open in response to changes in electric potential across the plasma membrane

Answer 21

Voltage-Gated Channels

Question 22

Importance of Active Transport

Answer 22

• Bring in essential molecules: ions, amino acids, glucose, nucleotides
• Rid cell of unwanted molecules
• Maintain internal conditions different from the environment
• Regulate the volume of cells
• Control cellular pH
• Re-establish concentration gradients to run facilitated diffusion.

Question 23

Classifications of Active Transport

Answer 23

(1) Primary Active Transport
(2) Secondary Active Transport

Question 24

ATP is directly used to move substances across the membrane against its concentration gradient

Answer 24

Primary Active Transport

Question 25

involves two channels: the first actively transports a substance out of the cell using ATP, and the second allows that substance to move back into the cell passively, using the energy released to transport another substance against its concentration gradient.

Answer 25

Secondary Active Transport

Question 26

Two substances are transported in the same direction across a plasma membrane

Answer 26

Symporter

Question 27

Two substances are transported across the membrane in opposite directions across the plasma membrane

Answer 27

Antiporter

Question 28

Can transport only
a single molecule
using facilitated
diffusion

Answer 28

Uniport

Question 29

Substances transported using vesicle formation:

Answer 29

(1) Neurotransmitters
(2) Hormones
(3) Digestive Enzymes

Question 30

Vesicles form as a way to transport molecules
into a cell

Answer 30

Endocytosis

Question 31

Vesicles form as a way to transport molecules out of a cell

Answer 31

Exocytosis

Question 32

Transports large, particulate matter (Bacteria, viruses, and aged or dead cells)

Answer 32

Phagocytosis

Question 33

Transport of liquids
and small particles dissolved in liquid

Answer 33

Pinocytosis

Question 34

Ligand receptor complexes trigger infolding of a clathrin pit that forms a vesicle containing ligands such as (LDLs); some vitamins, certain hormones, and antibodies.

Answer 34

Receptor Mediated Endocytosis

Question 35

Are vesicles with tubular extensions, located at the periphery of the cell, that fuse with clathrin-coated vesicles which have shed their coats.

Answer 35

Endosomes

Question 36

are phagosomes fused to lysosomes, contain lysosomal acid hydrolases that digest the ingested material

Answer 36

Phagolysosomes