LESSON 2b: CELL MEMBRANE TRANSPORT Flashcards
- is the boundary between
inside & outside…
– separates cell from its environment
Cell membrane
Comes in …..
Food:
-carbohydrates
-sugars,
-proteins
-amino acids
-lipids
-salts, O2,H2O
Comes out…..
Waste:
- ammonia
-salts
-CO2
-H2O products
Can cell membrane be an impenetrable boundary?
NO!
Cell membrane permeability is ___________
Selective
– Allows some materials to pass.
àWater, oxygen, carbon
dioxide
– Prevents others from passing.
àProteins, carbohydrates
Differentially (selectively)
Permeable
Factors that determine how a
substance may be transported
across a plasma membrane:
– Size
– Polar or Nonpolar
– charge
-2nd Law of Thermodynamics
governs biological systems
– universe tends towards disorder
(entropy)
PASSIVE DIFFUSION
Movement of molecules in passive diffusion
High —-> low concentration
Only________, _________
molecules are able to
diffuse across a
phospholipid bilayer
at significant rates by
using passive
diffusion
small and relatively hydrophobic molecules
In passive diffusion, Molecules have to
dissolve in _______
lipid interior
Molecules that can pass through plasma membrane by passive diffusion
- 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)
Why is diffusion important to cells
and humans?
Important in:
* Cell respiration
* Alveoli of lungs
* Capillaries
* Red Blood Cells
* Medications: time-release capsules
- Diffusion through protein channels which do not
interact with hydrophobic interior
– For biological mol unable to dissolve in hydrophobic
interior
– no energy needed
Facilitated Diffusion
Facilitated =___________
Open Channel= ____________
-with help
-fast transport
Molecules that transport using facilitated diffusion
- Ions (Na+, K+, Cl-)
- Sugars (Glucose)
- Amino Acids
- Small water soluble molecules
- Water (faster rate)
The passage of material in facilitated diffusion is aided both by ____________ and ___________
concentration gradient and transport protein
Two kinds of protein in facilitated diffusion
-Carrier Protein
-Channel Protein
-bind specific molecules, undergo conformational
change to release molecule
- ex. Glucose transporters
Carrier Proteins
- form open pores for free diffusion
- found in gap junctions
Channel Proteins
Molecules will
randomly move
through the pores
in ____________
Channel Proteins.
Some Carrier proteins ____________
through the membrane
do not extend
Some carrier protein _____________ molecules
through the lipid bilayer and release
them on the opposite side.
bond and drag
Other carrier proteins
___________to move
materials across the cell
membrane
change shape