Homeostasis and Cell Transport

5.1 Passive Transport

5.2 Active Transport

Homeostasis Biological balance with the environment Dynamic Equilibrium

- occurs when the concentration of

molecules of a substance is the same across

a space Works to control what enters and exits the

cell.

Permeability Allowing a substance to pass through

a membrane. Selectively Permeable

- only allowing some substance to pass

through the membrane

- based on size, shape, type

- important in maintaining homeostasis

Passive Transport NO CHEMICAL ENERGY IS USED Spontaneous Examples:

- osmosis- diffusion- facilitated diffusion- gated channels

Diffusion Moving from high concentration to low

concentration Concentration Gradient

- difference in concentrations of a substance across a space Osmosis

- diffusion of water

Example of Diffusion

Example of Osmosis

Hypertonic Solutions Concentration of solute in the

environment is greater than that of the cell

- higher concentration of water inside the cell

- water moves outside of the cell Plasymolysis: plant cells Crenation: animal cells

Hypotonic Solutions Concentration of solute in the environment

is less than that of the cell

- higher concentration of water outside

the cell

- water moves into the cell Cytolysis: animal cell Turgid: plant cell (homeostasis) Contractile Vacuole for protists

Isotonic Solutions Concentration of solutes inside and

outside the cell are equal No net movement of water

Flaccid: plant cells (fatal) Animal cells: homeostasis RBC’s .9% saline

RBC…what type of solution?

RBC…what type of solution?

RBC…what type of solution?

Keep in mind…

Passive Transport (2) Facilitated Diffusion

- use of carrier molecules or transport

proteins

-molecules are too large or not soluble in

lipidsEX. Glucose and Insulin

Ion Channels- protein controlled passage

- solutes enter on an “as needed” basisEX. Nerve Cells

Facilitated Diffusion

Diffusion vs. Facilitated Diffusion

Ion Channel

Active Transport Requires the use of CHEMICAL ENERGY (ATP) Examples:

- Sodium-Potassium Pump- Endocytosis

(pinocytosis and phagocytosis)- Exocytosis

Sodium-Potassium Pump

Occurs in muscle cells

Found in the plasma membrane

3 Sodium (Na+) leave and 2 Potassium (K+) enter AGAINST the concentration gradient

Uses carrier molecules

Sodium-Potassium Pump

Endocytosis Allows large molecules to enter the cell without

passing through the cell membrane

Phagocytosis solid particles Ex. white blood cells

Pinocytosis liquid particles Ex. Electrolytes entering the cell

Endocytosis

Exocytosis Allows large molecules to exit the cell without

passing through the cell membrane

Uses vacuoles and vesicles-proteins made in the ribosomes are

released in this fashion after they travel to the golgi apparatus

-contractile vacuoles

Exocytosis