Concept 2-Cell Transport

Dynamic equilibrium

Dynamic equilibrium

Maintained within a range, not constant

Static equilibrium

State of rest in the body

Response

Organism's reaction to environmental changes

Positive feedback loop

Intensifies a response (ex human childbirth)

Negative feedback loop

Causes a counter response to maintain stability (ex sweating, controlling blood sugar)

Cell membrane

Controls substance movement in/out of cell

Passive transport

Molecules move from high to low concentration gradient

Active transport

Requires energy to move from low to high concentration gradient

Simple diffusion

(passive transport) Molecules spread across the membrane until equilibrium is reached; molecules run down the concentration gradient (high to low []) EX: for small molecules like oxygen and CO2, other small nonpolar molecules

Ensures that cells are oxygenated by removing CO₂

Simple diffusion Homeostasis connection

Facilitated diffusion

(passive transport) Transport protein aids in molecule diffusion from (down) high to low concentration gradient (acting as a protein channel). Large molecules like sugar, glucose and calcium

regulates blood sugar by transporting glucose into the cell (transport protein is used)

Facilitated diffusion Homeostasis connection

Osmosis

(passive transport) Simple diffusion of water across cell membrane from (down) high to low concentration gradient until equilibrium is reached

changes water volume in the body (↑ or↓ blood pressure)

Osmosis Homeostasis connection

Molecular Pumps

(active transport) Cell uses energy to move molecules across membrane against the concentration gradient through a protein channel

calcium ions released contract and relax muscles

Molecular Pumps Homeostasis connection

Endocytosis

(active transport) Vesicles move large particles INTO the cell (blood cell engulfs bacteria)

Phagocytosis

Endocytosis: cell eating: Cell engulfs solids into vesicle and “digests” them

Pinocytosis

Endocytosis: cell drinking: Cell engulfs liquids into vesicle and “digests them

Exocytosis

(active transport) Vesicles export materials OUT of the cell (nerve cells secrete neurotransmitters)

Types of Passive Transport

Simple diffusion
Fascilitated diffusion
Osmosis

Types of Active Transport

Molecular pump
Endocytosis
Exocytosis

Hypertonic solution

Water [ ] is lower than the cells’ cytoplasm; Net movement of water OUT of the cell → cell shrivels

Hypotonic solution

Water [ ] is higher than the cell’s cytoplasm; Net movement of water INTO the cell → cell swells

Isotonic solution

Equal solute concentration to cell cytoplasm (same size cell)

Homeostasis

Organism's need to regulate internal conditions

Solute

Substance that gets dissolved (lemonade powder)

Solvent

Substance that does the dissolving (water)

Solution

Uniform mixture of two or more substances

Concentration

Amount of solute dissolved in solvent

Concentration Gradient

Difference in concentration of a substance from on location to another