transport mechanism

1. Transport
Mechanisms

2. Plasma Membrane
• semi-permeable
Functions:
• Barrier of the cell from the external environment
• Transmit signals by means of complex integral
proteins.
Component Function
Phospholipid Main fabric of the membrane
Cholesterol Dampens effect of temperature
Integral Proteins Transport substance through membrane
Peripheral Proteins Cell recognition
Carbohydrate  Cell recognition
 Effective interaction with the aqueous
environment

4. i. Phospholipids
-consist of a three-carbon glycerol backbone with two
fatty acid molecule attached to carbons 1 and 2; and a
phosphate- containing group attached to the 3rd carbon
Hydrophilic
head
(water-loving)
Hydrophobic
tail
(water-hating)
Phosphate
Glycerol
Saturated fatty
acid
Unsaturated
fatty acid

5. ii. Proteins
-second major component of plasma membrane
• Integral Proteins – proteins that act as tunnels or
channels for the passage of water and other
substance
(uniporter, symporter and antiporter)
• Peripheral Proteins- proteins that act as receptors
for hormones, recognition center and antigens
iii. Carbohydrates
- third major component of plasma membranes ;
- are found at the external surface of the membrane
and are bound to either proteins (forming glycoproteins) or
to lipids (forming glycolipids)

6. Passive Transport
• naturally occurring phenomenon and does not require cell
energy to accomplish the movement
• substances move from an area of higher concentration to
an area of lower concentration
Concentration gradient- a physical space in which there is a
range of concentrations of a single substance
 Diffusion
 Facilitated diffusion
 Osmosis

7. i. Diffusion
 Substances tend to move from an area of
high concentration to an area of low
concentration until the concentration is
equal across the space ( dynamic
equilibrium is reached )

8. Factors that Affects Diffusion
 Extent of the concentration gradient
 Mass of the molecules diffusing
 Temperature
 Solvent density
 Solubility
 Surface area and thickness of the plasma
membrane
 Distance travelled

9. ii. Facilitated Diffusion
 Materials diffuse across the plasma
membrane with the help of membrane
proteins.Transport Proteins- integral proteins involved in the
facilitated diffusion and functions as either channels or
carriers
 Channel Proteins
specific for a substance that is being transported.
 Carrier Proteins
binds a substance and triggers a change in its
own shape, moving the bound molecule from the
outside of the cell to its interior

11.  iii. Osmosis
 is the movement of water through a
semipermeable membrane according to the
concentration gradient of water across the
membrane, which is inversely proportional
to the concentration of solutes
 Tonicity- describes how extracellular solution can
change the volume of the cell by affecting osmosis
 Osmolarity- total solute concentration of the solution.
Low Osmolarity- solvent > solute
High Osmolarity- solvent < solute

12. OSMOLARITY OF THE CELL
Hypertonic Solution- extracellular fluid has
less water concentration than intracellular fluid.
Hypotonic Solution- extracellular fluid has
more water concentration than intracellular fluid
Isotonic Solution- extracellular fluid has same
water concentration than intracellular fluid

14. Active Transport
• requires cell energy to accomplish the movement
• substances move into the cell against its concentration
gradient
Electrochemical Gradient- a physical space in which
there is difference of charge across the membrane
 Primary Active Transport
 Secondary Active Transport

15. Primary Active Transport moves ions
across the membrane and creates a difference in
charge across that membrane which is actually
dependent in ATP
Secondary Active Transport describes
the movement of material that is due to the
electrochemical gradient established by the PAT
and does not primarily require ATP

17. Bulk Transport
 The process by which cell engulfs and removes larger
molecules and particles
Endocytosis
 Phagocytosis
 Pinocytosis
 Receptor-mediated Endocytosis
Exocytosis

18. Endocytosis – is a type of active transport that move
particles, such as large molecule, parts of the cells, and
even the whole cell, into a cell
 Phagocytosis- a condition of cell-eating
 Pinocytosis- cell- drinking process
 Receptor-mediated Endocytosis- a
molecule can bind into a surface (clathrin) of the
membrane and stimulates the internal surface of
the membrane to fold and do the phagocytosis

20. Exocytosis – the reverse process of endocytosis;
its purpose is to expel material from the cell into the
extracellular fluid
Extracellular fluid