Activating Prior Knowledge1. Define the term homeostasis.

2. Give the function of each of the following organelles:

Cell membrane –

Lysosome –

Golgi Apparatus –

3. How does the cell membrane maintain homeostasis?

4. Label and describe as many parts/features of the cell membrane as you can.

5. Distinguish between peripheral and integral proteins. Put in diagram above.

1) Define HOMEOSTASIS Maintaining a relatively constant or stable internal

environment, even when external conditions change dramatically

2) Give the function of each of the following organelles

Cell (plasma) membrane

a flexible boundary between a cell and its environment

allows nutrients into the cell no matter what the external conditions are.

2) Give the function of each of the following organelles

Lysosome

Clean up crew – break down organelles that have outlived their usefulness

Break down lipids, carbs, proteins

Golgi Apparatus

Modifies, sorts and packages proteins and other materials from the ER for storage in cell or release outside of cell

3) How does the cell membrane maintain homeostasis?

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

4) Label and describe as many parts/features of the cell membrane as you can:

Components of Cell Membrane:

Plasma Membrane (5:15)

Key Terms Associated with Transport:

Concentration Gradient - difference in amount of molecules across space

Down the concentration gradient:

Higher Concentration Lower Concentration

Up the concentration gradient:

Lower Concentration Higher Concentration

Equilibrium - when the concentration is the same throughout

Concentration Gradient:

Types of Transport:Passive Transport– movement of

molecules down their concentration gradient without the use of energy

Active Transport- movement of molecules up their concentration gradient with the use of energy

Active, Passive and Bulk Cell Transport (4:33)

Passive and Active Transport

Structure Of The Cell Membrane - Active and Passive Transport (6:52)

Passive Transport:

Determining Factors Size Type of Molecule Chemical Nature of

membrane

Small, nonpolar, hydrophobic molecules

4 Types of Passive Transport

Diffusion

Osmosis

Facilitated Diffusion

(Diffusion) Ion channels

Diffusion:

Diffusion:

Process by which molecules tend to move from an area where they are more concentrated to an area where

they are less concentrated (passive)

Osmosis:

Diffusion of water through a selectively permeable membrane (passive)

from an area of higher water concentration to an area of lower water concentration

Osmosis:

How Osmosis Works (McGraw Hill)

Solutions Can Be:ISOTONIC - solute concentration SAME on each

side of membrane Water diffuses in and out of the cell at the same rate

Effect: No net change in cell size

Water In

Cell size stays the same

Water Out

Solutions Can Be:HYPOTONIC - Solution with a solute

concentration lower than cellWater will diffuse INTO cell until equilibrium

Effect: The cell swells and may burst

Cell size gets LARGER

Water In

Solutions Can Be:Hypertonic - Solution with a solute

concentration higher than the cell Water will diffuse OUT cell until equilibrium

Effect: The cell shrinks

Water Out

Cell Size gets SMALLER

Effects of Osmosis:Water diffuses from a hypotonic to a

hypertonic solution

Egg Demo:

Water

Hypotonic solution

Corn Syrup

Hypertonic solution

The Sci Guys: Science at Home - SE1 - EP14: The Naked Egg and Osmosis

Dealing with Osmosis: Plants (root cells) swell in a hypotonic environment

The swelling stops when the cell membrane is pressed against the cell wall

The cell wall is strong enough to resist the pressure, called turgor pressure

(pressure exerted against the cell wall in a hypotonic environment)

Cytolysis and Plasmolysis Cytolysis – In a hypotonic solution, cells can swell

and eventually burst

Plasmolysis - In a hypertonic environment, water leaves the cell and the cell shrinks away from the cell wall as turgor pressure is lost

Contractile Vacuole Unicellular freshwater organisms (Paramecium) live in a

hypotonic environment

Contractile Vacuole - collects excess water and pumps it out of cell

Review Questions:1. Toward what condition does diffusion eventually lead, in the

absence of other influences?

2. How is osmosis related to diffusion?

3. If the concentration of solute molecules outside a cell is lower than the concentration in the cytoplasm, is the external solution hypotonic, hypertonic, or isotonic to the cytosol?

4. Sea water has a higher concentration of solutes than do human body cells. Why might drinking large amounts of sea water be dangerous to humans?

Facilitated Diffusion Movement of specific molecules across cell

membranes through protein channels

Passive transport

diffusion of materials across a cell membrane assisted by carrier proteins

Facilitated Diffusion (1:18)

Facilitated Diffusion Move molecules, (that cannot diffuse easily), down

their concentration gradient

Move into or out of cell

Examples: Glucose, Amino Acids, Ions,

Polar molecules (water)

Assisted by carrier proteins on the membrane

Specific to one type molecule

More protein=faster diffusion

Protein Channels and Carrier Proteins

molecules pass through channel proteins that span

the membrane

Gated Channels are able to regulate the passage of particles

by opening and closing gates that prevent passage

Some gated channels open in response to the difference in ion concentration across the membrane. Other gated channels open when a specific substance binds to the channel protein.

carrier proteins allow molecules to pass through when their shape

changes

the carrier protein changes shape and releases the molecule to the

side of the membrane that has the lower concentration

Facilitated Diffusion of Glucose through a carrier protein:

Ion Channels—Na+, K+, Ca2+, Cl-

Provide protein channels for ions to diffuse

Specific to Ion

Two types

1. Open

2. Gated—open and close in response to specific stimuli

Channel Proteins (2:25)

Passive and Active Transport

Membrane Transport (6:13)

Active Transport: Cells use energy to move up concentration gradient

ATP supplies energy

Carrier proteins act as pump

Active and Passive Transport (6:12)loud background music

SODIUM-POTASSIUM PUMP: In animal cells transport Na+ and K+ up

the Concentration Gradient 3 Na+ moved outside of cell

2 K+ moved inside cell

Builds up a chemical and electrical gradients for each ion.

These gradients can be used to drive other transport processes. In nerve cells these gradients are used to

propagate electrical signals that travel along nerves.

Therefore the action of nervous tissue requires ATP to generate resting potentials.

How the Sodium Potassium Pump Works

[Microbiotic] 2:01

ATP – Adenosine Triphosphate• Cells release energy from ATP molecules by subtracting a

phosphate group• The energy of ATP is locked in the bonds between the

phosphate groups.• When the terminal phosphate group of the ATP molecule

is removed by hydrolysis, energy is released and adenosine diphosphate (ADP) and phosphate are formed.

Steps for Transport1. 3 Na+ bind to carrier

protein in cytoplasm Carrier protein splits

phosphate group from ATP

2. P group binds with carrier protein—shape changes—releases Na+

3. Now protein can pick up 2 K+ on outside

4. Carrier protein changes shape releases K+

Sodium Potassium Exchange Pump

Exocytosis and Endocytosis: Transport large molecules across membrane

Transport a large amount of small molecules

Energy (ATP) used

Endocytosis and Exocytosis (1:15)

Exocytosis Exporting large molecules

outside of cell

Process

Packaged in Golgi Apparatus

Vesicle transports to cell membrane

Vesicle fuses to membrane

Contents released

Vesicle becomes part of membrane

Endocytosis Cells take in (ingest) substances

Process

Depression in cell membrane folds in enclosing material from outside of the cell

Pinched off forming a

membrane-bound vesicle

Vesicle fuses with lysosomes

Fuse with other organelles

3 Types of Endocytosis: Pinocytosis—”Cell Drinking”

Ingestion of tiny droplets

Phagocytosis-”Cell Eating”

Engulfs large, solid molecule or whole cells

(like bacteria)

Receptor-mediated—Specific

Ingestion of specific substances that bind to receptor proteins on specialized areas of cell membrane

3 Types of Endocytosis:

Review - Membrane Transport : Animation 3:18

Review Questions:1. Explain the difference between passive and active transport.

2. What provides the energy that drives the sodium-potassium pump?

3. Explain the difference between phagocytosis and pinocytosis.

4. During intense exercise, potassium tends to accumulate in the fluid surrounding muscle cells. What membrane protein helps muscle cells counteract this tendency? Explain your answer.