Download Cell Processes

Cell Processes
Transport
I. Transport
Cell Membrane helps maintain homeostasis by
regulating what substances enter and leave
the cell
1. Passive Transport - movement of materials
across a membrane which requires no cellular
energy
-Due to a difference in concentrationmolecules move down concentration gradient
a. Diffusion
- movement of materials from an area of high
concentration to area of low concentration
- may or may not include a membrane
-only small, non-polar molecules diffuse through
membrane
Driven by: kinetic energy
Diffusion naturally leads to: equilibrium
Equilibrium: when all the movement of
molecules is equal
B. Osmosis
- passive transport of water across a membrane
from high concentration to low concentration
1.Hypertonic:
Plasmolysis- shrinking of a cell from loss of water
2. Hypotonic:
Cytolysis- swelling and bursting of a cell caused by
internal pressure
Turgor Pressure- pressure that builds up in a cell due to
the inward flow of water
3. Isotonic:
C. Channel Proteins
-Used when molecules have a charge (they
would get stuck in middle)
D. Facilitated Diffusion
-Used when substances are too large to pass
through
-Diffusion through carrier proteins
Contrast Channel Protein vs. Facilitated
Diffusion
2. Active Transport
-Requires cellular energy ( ATP)
-Sometimes the cell must move materials
against their concentration gradient
a. Cell Membrane Pump
-Uses carrier proteins to transport substances
against the concentration gradient
B. Endocytosis
• -Ingestion of: fluid or macromoleucules
-Two Types:
• Pinocytosis: cell drinking
• Phagocytosis: cell eating
-Forms a vesicle from
cell membrane
• Ex: White blood cell
c. Exocytosis
-Vesicles in cytoplasm fuse with the membrane
and release contents outside cell