Science Concept 2

Dynamic Equilibrium

The steady state of a reversible reaction where the rate of the forward reaction is the same as the reaction rate in the backward direction.

Static Equilibrium

Also known as mechanical equilibrium, means the reaction has stopped. In other words, the system is at rest.

Homeostasis

Need of an organism to stay stable by regulating internal conditions.

Stimulus

Change in Environment

Response

A change in the organism, as a result of stimulus

Stimuli and Homeostasis relationship

Both external and internal stimuli can cause a response from an organism. Organisms respond to external stimuli to maintain homeostasis.

Positive Feedback Mechanism

This feedback loop enhances or amplifies changes; this tends to move a system away from its equilibrium state and make it more unstable.

Examples are human child birth and fruit ripening

Negative Feedback Mechanism

In this feedback loop the output (or product) causes a counter response to return to a set point. Tend to dampen or buffer.

Examples are Human Body temperature regulation and blood sugar regulation

How cell membrane affects homeostasis

The cell membrane controls the movement of things in and out of the cell. The cell membrane is selectively permeable, picky of what goes in and out. It affects homeostasis by controlling the movement of substances across the cell membrane

Passive Transport

This transport requires no extra energy because molecules from high concentration to low, down the concentration gradient.

Ex. Simple diffusion, facilitated diffusion, and osmosis

Active Transport

This transport requires extra energy (ATP) to spend bringing materials in and out of the cell, moving low to high concentration. Against concentration gradient.

Ex. Molecular pumps, exocytosis, and endocytosis

Solute

What gets dissolved (koolaid powder)

Solvent

Does the dissolving (water)

Solution

Uniform mixture of or more substances . EX. Koolaid juice

Concentration

Amount of solute dissolved in solvent

Concentration Gradient

Difference in concentration of a substance from one location to another.

Simple Diffusion

Random movement of a substance from a region of higher concentration to lower concentration until equilibrium.

Facilitated Diffusion

A transport protein helps to facilitate the diffusion of molecules that normally couldn’t pass through cell membrane. Molecules move down a concentration gradient from high [] to low [].

Osmosis

Simple diffusion of WATER across cell membrane. Move down concentration gradient from high [water] to low [water].

Endocytosis

Uses vesicles to move large particles into the cell.

Ex. When white blood cells engulf bacteria in order to fight infections.

Exocytosis

Uses vesicles to export materials out of the cell.

Ex. When nerve cells create neurotransmitters send signals throughout the body.

Molecular Pumps

When a cell uses energy to pump molecules across the membrane, against the concentration gradient through a protein channel.

Hypertonic Solution

Water concentration is lower than cell’s cytoplasm. Water moves out of cell and cell shrivels

Hypotonic Solution

Water concentration is higher then cells cytoplasm. Water moves in and cell swells

Isotonic

Identical Water Concentration to cell cytoplasm and cells stay the same. Move in and out