I. Purpose of membranes - cellular and
organelle
A. Continuum of systems - nucleus and endoplasmic reticulum
1. "Flow of metabolites"
B. Isolation - mitochondrion cannot
fuse with nucleus
2. "Independent recognition
sites"
C. Passage of metabolites
1. Diffusion - from high concentration
to low concentration
2. Osmosis - movement of water through
a differentially permeable membrane
a) From high concentration to low
concentration
b) Selectivity - active transport
3. Carrier systems
a) Chloroplast
1) H+ pumped into thylakoid
lumen
2) H+ then transported to
outer stroma and coupled to make ATP
b) Mitochondrion
1) H+ pumped out to
intermembrane space
2) H+ then transported to
inner matrix and coupled to make ATP
II. How
is specific transport accomplished?
A. Biological membranes
1. Recognition of ions
2. What recognizes the ions?
a) Proteins in the membrane - maybe
enzymes
1) Carrier theory
2) Ion pump (ATPase)
3. Model of a membrane - Fluid mosaic
model
a) Lipid bilayer - phospholipids
(cholesterol)
b) Proteins
1) Peripheral - surface (in and out)
2) Integral - usually through
(sometimes partially)
III. Types of transport
A. Within cells
B. Between cells
IV. Transport in vascular tissue
A. Passive transport - mass flow - little or no metabolic
involvement
1. Apoplast (dead)
a) Xylem (tracheids & vessels)
b) Up - diffusion - adhesion (sticking
of unlike) & cohesion (sticking of like)
B. Active transport - selective transport (ENERGY) -
metabolic involvement
1. Symplast (living)
a) Phloem (sieve cells)
b) Down - osmosis
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