2b- Cell membrane transport Flashcards
in
Food
- carbohydrates
- sugars,
- proteins
- amino acids
- lipids
- salts
- O2
- H2O
out
Waste
- ammonia
- Salts
- CO2
- H2O products
Permeability of plasma membrane
- Differentially (selectively) permable
Materials allowed to pass
Water, oxygen, carbon dioxide
prevents other from passing
Protein, Carbohydrates
Factors that determine how a substance may be transported across a plasma membrane:
- Size
- Polar or nonpolar
- Charge
- 2nd law of Themodynamics
- governs biological systems
– universe tends towards disorder (entropy)
Passive diffusion
movement from high to low concentration
Passive diffusion
Are the molecules are able to diffuse across a phospholipid bilayer at significant rates by using passive diffusion.
Only small, relatively hydrophobic
Gases
- Oxygen
- carbon dioxide
Water molecules
- rate slow due to polarity
Lipid
Steroid Hormones
lipid soluble molecules
- Hydrocarbons
- alcohols
- some vitamins
small nonecharged molecules
- NH3
Why is diffusion important to cells and humans?
- Cell respiration
- Alveoli of lungs
- Capillaries
- Red Blood Cells
- Medications: time
release capsules
Diffusion through protein channels which do not interact with hydrophobic interior
- no energy needed
Facilitated diffusion
with help
facilitated
fast transportation
Open channel
two kinds of proteins
- Carrier proteins
- Channel proteins
bind specific molecules, undergo conformational change to release molecule
Carrier proteins
example of carrier protein
Glucose transporters
- form open pores for free diffusion
- found in gap junctions
Channel proteins
Molecules will randomly move through the pores in ____ ____
Channel proteins
do not extend through the membrane
Some carrier proteins
Other carrier proteins ____ ___ to move materials across the cell membrane
change shape
How do molecules move through the plasma membrane by facilitated diffusion?
- Channel and Carrier proteins are specific:
- Channel Proteins allow ions, small solutes, and water to pass
- Carrier Proteins move glucose and amino acids
- Facilitated diffusion is rate limited, by the number of
proteins channels/carriers present in the membrane.
- provide corridors allowing water molecules to cross the membrane.
- Allow for fast transpor
- water channels
- protein pores used during osmosis
Aquaporins
is the diffusion of water across a differentially permeable membrane.
Osmosis
is the pressure that develops in a system due to osmosis.
Osmotic pressure
Different concentration
Hypertonic
Hypotonic
Isotonic
more solute, less water
Hypertonic
less solute, more water
Hypotonic
equal solute, equal wate
Isotonic
- animal cell immersed in mild saltsolution
- volume of cell is stable
- no net movement of water
isotonic