Homeostasis and TransportChapter 5

What is Homeostasis??

Why is Transport important within your cells??

What are some things that are transported within you body??

QUESTIONS??

Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells

Movement of substances across the membrane that does NOT require energy “ Passive Transport”

Movement is based on the presence of a concentration gradient

I. Passive Transport

Concentration gradient

Difference in concentrations of the substances. Ratio of solute to solvent

No net movement when there is equilibrium

A condition where the gradient disappears

The process by which substances move from

an area of high solute concentration to an area of lower solute concentration

Diffusion is the simplest type of passive transport

Driven entirely by the kinetic energy the molecules possess

Molecules tend to move “down” their concentration gradient from (high to low conc.)

A. Diffusion

Diffusion

Cell membranes have the ability to control what passes through them

The ability of a molecule to go through a membrane depends on…..

1. The size of the molecule. Molecules can be polar and still move through lipids because they are very small

2. The type of molecule. Can it dissolve in lipids? Ex: CO2 and O2 can dissolve in lipids. Why?

3. The molecular structure of the membrane

The movement of water from an area of high water concentration to an area of low water concentration

Another way to say this is… The movement of water from an area of low

solute concentration to an area of high solute concentration

B. Osmosis

The net direction of water molecule movement

is dependent upon…

Concentrations of water

Solutes dissolved in the solution

Direction of Osmosis

Pics

1. HYPOTONIC:

Outside Cell: low solute, high solvent

Inside Cell: high solute, low solvent

Effect on Cell: Cell will Swell

3 Types of Solutions

HYPERTONIC:

Outside Cell: high solute, low solvent

Inside Cell: low solute, high solvent

Effects on cell: Cell will shrink

ISOTONIC:

Outside Cell: same solute and solvent

Inside Cell: same solute and solvent

Effects on Cell: stays the same

pic

The blood cells

are shriveling up because the water is leaving the cell.

The cells are normal because the water stays in the cell.

Pic

Turgor Pressure- The pressure exerted by water inside the cell against the cell wall.

The net movement of water into a cell can

cause Turgor Pressure When turgor pressure is too high or the cell

takes in too much water the cell can swell But wont “burst”

WHY?? When turgor pressure is lost, the plant wilts-

Plasmolysis

Role of Osmosis

Some organisms live in a hypotonic

environment

---Why is this bad for a single celled organism??

Contractile Vacuoles Specialized organs remove excess water

Uses Carrier Proteins

Specific to what they will transport across the cell membrane

No energy required (Passive process)

Speeds up diffusion

D. Facilitated Diffusion

Facilitated Diffusion

Transport proteins that allow ions to pass

through the cell membrane

Channels are either Open or Closed

Closed channels will respond to different stimuli to allow things to pass through them

C. Ion Channels

PIC

PIC

Examples of Passive Transport

The movement of any substances across a cell

membrane that does require energy

Active Transport Vid

II. Active Transport

Movement of Sodium and Potassium against

the concentration gradient

Uses ATP as energy source

Important for many vital functions: 1. Muscle contractions 2. Nerve impulses 3. Kidney function

A. Sodium Potassium Pump

Sodium/Potassium Pump. Na+/K+ Pump

Processes used for moving substances across

a membrane that are too large to pass through a channel

1. Endocytosis: Process by which cells take in large particles.

Ex: external fluid, macromolecules, and other cells

A. Phagocytosis: - food particles or microscopic organisms

B. Pinocytosis:- solutes or fluids

B. Endocytosis and Exocytosis

2. Exocytosis:

Process that removes large waste products from the cell and large molecules such as proteins.

What organelle produces the vesicles that will eventually fuse with the cell membrane and release its contents?

Endocytosis and

Exocytosis

Formation of vesicles

A protein that binds to a specific signal

molecule

Enables the cell to respond to the signal molecule

The binding of a signal molecule to the receptor protein causes changes in the receiving cell in three ways…..

III. Receptor Proteins

1. Changes in Permeability: Opens channels to allow specific ions to cross

the cell membrane

2. Forming of Second Messenger Acts as a signal molecule in the cytoplasm

which amplifies the signal of the original molecule

3. Activation of Enzymes: Speeds up the reactions of some cell functions

Review Notes- KNOW EVERYTHING!

STUDY for EXAM!!