Transcript Transport Across the Membrane

Transport Across the Membrane
(Summary of Protein Mediated Transport)
SEC 4.2, 4.4 4.5, PAGES 72- 79
Transport can be PASSIVE or ACTIVE

PASSIVE With Concentration Gradient, No ATP needed,
like “rolling down a hill
 Diffusion
 Facilitated

 Channel Proteins or  Carrier Proteins
ACTIVE Against Concentration Gradient, Requires ATP
 With
Proteins  “Pumps”
 With
Vesicles  Exo and Endocytosis
A. Transport by Carrier Proteins Sec 4.4
 Specific
proteins that combine with specific
molecules
•
Carrier changes shape upon when combines
then returns to initial shape
•
Involved in both Passive (Facilitated) Transport
& Active too!
B. Transport by Vesicles Sec 4.5

EXOCYTOSIS export OUT of cell

ENDOCYTOSIS  INTO cell
3 types
P- Passive?
A- Active?
PASSIVE
PASSIVE
Name of
Process
Direction
Requirements
Examples?
Diffusion
High
Conc. Gradient
concentration to Only
Low
Gases- O2
Small
Lipid soluble
Water (osmosis)
Facilitated
Transport
High Conc. To
Low
Conc. Gradient &
Channel or Carrier
Protein
Some sugars
ex) glucose
Amino acids
OUT of Cell
VESICLE fuses with
P.M
Macromolecules
ACTIVE
Exocytosis
ACTIVE
Endocytosis
i) Phagocytosis
Into Cell
Vacuole formation
Cells, Sub-cellular
materials
ii) Pinocytosis
Into Cell
Vesicle Formation
Smaller molecules, liquids
iii) Receptor
Mediated
Into Cell
Receptor Protein,
PM to form vesicle
ex: hormones, cholesterol
Pump Proteins
(Facilitated)
AGAINST
Gradient
Carrier Protein & ATP Other sugars, amino acids,
ions
ACTIVE
ACTIVE
ACTIVE
Fig 4.13 pg 79
 Look at picture & Make own notes
Receptor Mediated Endocytosis
 BIG
A
IDEAS
form of pinocytosis
Very
Specific
Used
for vitamins, peptide hormones,
lipoproteins  transport of Cholesterol
Used
to move substances IN & to TRANSFER
substances between cells (eg move from
mother’s blood to baby’s blood at placenta)
1.
Solute binds to receptor & receptors gather

Formation of a coated pit with fibrous protein
2. Vesicle forms & fibrous protein covering is released
3a. Vesicle releases solute into cytoplasm
b. Vesicle fuses with lysosome for break down
c. Vesicle transports solute to other location
4. Receptors & Membrane of vesicle return to PM
Ex. Hyper-Cholesterolemia
Ex. Hyper-Cholesterolemia

Genetic Disorder

Low density lipoproteins (LDLs) transport
cholesterol in the blood

Reduced # or Defective LDL receptors on
PM

Cholesterol can’t enter cells normally &
builds up in arteries

RESULT: High Blood Pressure, Blocked arteries,
Heart Attacks