Unit 2 - Ch 5 - Biological Transport Flashcards
Water Potential Definition
amount of free energy in water or energy avialable to do work
Water potential causes
- from gravity (adds to W.P.)
- and/or pressure (add or decrease or no effect on W.P)
- and/or solute (decreases w.p. or no effect - no solute)
Water Movement
water moves from high to low water potentials
Bulk Flow Definition
- overall movement of a substance caused by gravity and/or pressure - movement is all in one direction
= Circulatory system - moves blood via pressure
Diffusion definition
movement of a substance from high concentration to low concentration (there may be a membrane)
Diffusion Cause
random molecular motion
- requires no energy
- passive transport
Dynamic equilibrium
eventually occurs, diffusion ceases, molecular motion continues
Diffusion Rates are influenced by:
- Concentration Gradient - high gradients diffuse faster
- Solute Weight - lighter solute weights diffuse faster
- Solvent Viscosity - thickness - highly viscous diffuse slower
- Temperature - increased temp. increases diffusion rates (temp. is a measure of molecular motion)
Osmosis definition and cause:
A. Definition - diffusion of water across a semi-permeable membrane that excludes solute
B. Cause - random molecular motion - no energy required - passive
Tonicity
refers to the solute concentration
Isotonic
equal solute concentration; equal h2o concentration
Hypertonic
higher solute concentration; lower h2o concentration
Hypotonic
lower solute concentration; higher h2o concentration
Animal cell in Isotonic Solution
- h2o potential on both sides is equal
- water crosses both ways
- no net h2o flow
= Injections/Cell Cultures - normal saline (.85% NaCl) - osmotic balance
Animal cell in Hypertonic Solution
- > .85% NaCl
- cell is hypotonic
- net h2o loss from the cell
- crenation occurs
Crenation
In an animal cell, volume decreases when placed in a hypertonic solution
Animal cell in hypotonic solution
The cell is hypertonic
- net h2o gain into cell
Lysis will occur in deionized water (no solute, 100% h2o)
= hemolysis of red blood cells
Lysis
refers to the breaking down of the cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity
Plasmolysis
due to osmosis in plants, the cell membrane tears away from cell wall
= over fertilize lawn
Turgor Pressure
cell increases in volume up to the limits of the cell wall
- equilibrium occurs due to water potential
- provides rigidity in the stems of herbaceous plants (non-woody; grasses and forbs)
Osmotic Potential
reduction in the free energy of water due to solute presence
- the more solute, the more negative the osmotic potential
- no solute, no osmotic potential
In osomosis, net H2O movement occurs from:
- higher to lower water concentration
- higher to lower water potential
- lower to higher solute concentration
- hypotonic to hypertonic solutions
- less negative to more negative osmotic potentials
Describe the factors that influence the permeability of materials to a cell.
- Lipid solubility - nonpolar substances often pass through the bilayer = o2 gas, co2
- Ionization - ions tend to be excluded by the bilayer
- Size - large molecules pass slower or are excluded by the bilayer = glucose
Carrier Proteins purpose and specificity
A. Purpose - allow passage of impermeable molecules
B. Specificity - high degree of specificity due to tertiary structure
Facilitated Transport OR Carrier Facilitted Diffusion
- diffusion through a carrier protein - no energy required (passive transport)
- transport in or out of cells depending upon the gradient
Active Transport
- passage of a substance through a carrier protein against the gradient - requires ATP
- Irreversible - pumps in or pumps out
- Na+/K+ pump - pump Na+ out of cells - pumps K+ into cells - counteracts facilitated transport
Exocytosis
Transport of material outside of cells via a vesicle
- common in secretory cells
- active (requires energy)
Endocytosis. Definition and types
Definition - movement of material into a cell via a vesicle formation - requires energy
A. Phagocytosis
B. Pinocytosis
C. Receptor-Mediated
Phagocytosis
cells transport solid material into cells
= amoebe, white blood cells
Pinocytosis
cells transport liquid matrial into cells
= capillaries, small intestine
Receptor-Mediated endocytosis
a specific substance binds to a receptor protein on the cell surface and initiates endocytosis = cholesterol transport
Desmosomes
Cell junctions formed from proteins anchored into intermediate filaments within cells - found in tissues that stretch
= skin, stomach
Tight Junctions
protein strands that “stitch” cells together
- forms a semi-permeable sheet of cells
= small intestine
Gap Junctions
cell to cell connection in animal cells
- allow for rapid cellular communication via chemical stimuli
- formed from proteins
= cardiac muscle
Plasmodesmata
cell to cell connections in plants
- allow for rapid cellular communication via chemical signals
