Chapter 3: Movements of substances across plasma membrane

Question 1

function of colesterol

Answer 1

make the plasma membrane:

• stronger
• more flexible
• less permeable to water-soluble substance (ions)

Question 2

function of glycoprotein or glycolipid

Answer 2

protein and lipids that have carbohydrate chain attached on it

• act as receptor to hormone
• act as antigen for cell identification
• stabilize the plasma membrane by forming hydrogen bond with the water

Question 3

substance across plasma membrane

Answer 3

Plasma membrane

• CO2, O2, H2O
• lipid-soluble substance

Carrier Protein

• glucose
• amino acid

Channel protein

• ions
• small molecule

Question 4

definition of facilitated diffusion

Answer 4

• transport of substance across the plasma membrane
• with aid of transport protein
• down the concentration gradient
• until the dynamic equilibrium is reached

Question 5

sodium-potassium pump

Answer 5

• 3 sodium ions bind with the specific active site of carrier protein
• ATP molecules decompose into ADP molecule and a phosphate group
• the phosphate group bind with the carrier protein
• phosphate group provide energy and change the shape of carrier protein
• sodium ions is transported out the cell
• 2 potassium ions from outside of cell bind to the specific active site of carrier protein
• phosphate group leaves the carrier protein
• carrier protein lose energy and back to its original shape
• potassium ions is transported into the cell

Question 6

proton pump

Answer 6

• found in epithelial lining of stomach cavity
• energy from ATP allow hydrogen ions to be transported by proton pump toward extracellular fluid
• hydrogen ions accumulate
• acid produce in stomach cavity
• cause the acidic content in stomach

Question 7

how liposome work

Answer 7

• vesicle contain aqueous solution
• surrounded by phospholipid bilayer membrane
• used to protect drugs or active substances
• water-soluble drugs is transported in hydrophilic area
• water-insoluble drugs is transported in hydrophobic area
• can be taken orally and being digested by gastric juices
• thus can reach the target cells

Question 8

reverse osmosis

Answer 8

• extract fresh water from sea water
• using desalination
• exert pressure to push the seawater across a semi-permeable membrane
• only water molecule can pass through but not foreign substance (salt and microorganism)
• ## thus pure fresh water is released

Question 9

how to clean wound

Answer 9

• using flowing tap water
• prevent entrance of foreign particles
• tap water is hypotonic solution to bacteria
• water diffuse into bacteria through osmosis down concentration gradient
• bacteria burst and die