the life function that involves the absorption (taking in) and circulation (moving around) of materials throughout an organism. 

• the process where digested (broken down) nutrients as well as other dissolved materials enter the cells of an organism

• the key organelle that is involved with this life function is the PLASMA (CELL) MEMBRANE

Proteins

Membrane movement animation

Polar heads love water & dissolve.

Non-polar tails hide from water.

Carbohydrate cell markers

Fluid Mosaic Model of the

cell membrane

Cell membranes have pores (holes) in ita.Selectively permeable:

Allows some molecules in and keeps other molecules out

b.The structure helps it be selective!

Size (macro or micro), charge (+ or -) and solubility (lipid-soluble or not) affect a molecule’s ability to cross the cell membrane.

In general, small noncharged, lipid-soluble molecules easily cross the cell membranes

Remember. it is a double lipid layer with floating proteins...

We also can call the plasma membrane the fluid mosaic

model. Fluid because the double layer moves around, it never is motionless. A mosaic

because that is how it appears--a mosaic is a piece of art that is made up of lots of little pieces put together.

a.Phosphate head is polar (hydrophilic or water loving)

b.Fatty acid tails non-polar (hydrophobic or water fearing)

c.Proteins embedded in membrane

• the transport of materials within one cell and/or the transport of materials throughout a multicellular organism

• for unicellular organisms, intracellular (inside the cell) circulation is accomplished by the endoplasmic reticulum, Golgi complex, and CYCLOSIS (cytoplasmic streaming).

• for multicellular organisms, intercellular (between cells) circulation is accomplished by the diffusion or transport through vascular tissues (like xylem, arteries)

* it is called passive transport because NO ENERGY or ATP IS REQUIRED!!!

high

low

Weeee!!!

1. Diffusion2. Facilitated

Diffusion3. Osmosis

TonicityWater Potential

(HighLow)

1. Diffusion 2. Facilitated Diffusion – diffusion

with the help of transport proteins 3. Osmosis – diffusion of water

• *diffusion is where very small particles move from a region of high concentration (a large amount) to a region of lower concentration (a smaller amount). 

• * molecules move in straight lines in a random direction

• * diffusion usually happens until the concentration is the same throughout; this is called EQUILIBRIUM (a balanced state-- HOMEOSTASIS!)

• Note: molecules will still move around but stay spread out.

Occurs in liquid or gas mediumDiffusion of a solute within a solvent is

affected by several factors: Temperature Pressure Density of the solvent Concentration Gradient Solubility of the solute

http://bio.winona.edu/berg/Free.htm

* larger molecules such as polysaccharides, proteins, and lipids cannot fit, because they are too big

2. Facilitated diffusion: diffusion of specific particles through membrane transport proteins to help them move through the cell membranea. Transport Proteins are specific – they “select” only

certain molecules to cross the membraneb.Transports larger or charged moleculesc. Concentration gradient required – can’t transport

from low to high concentrationd. Energy not needede. Rate of transport reaches a maximum when all

membrane transport proteins are used up (saturated)

f. Membrane transport proteins are sensitive to inhibitors that can cause them not to function

Passive Transport: 2. Facilitated Diffusion

• http://bio.winona.edu/berg/Free.htm

There are 2 types of membrane transport proteins involved:

Channel proteins – contain tunnels/openings that serve as passageways of molecules

Carrier proteins – undergo temporary binding to the molecule it carries resulting in conformational change that moves the molecule through the membrane

Facilitated diffusion (Channel Protein)

Diffusion (Lipid Bilayer)

Passive Transport: 2. Facilitated Diffusion

Carrier Protein

A B

• http://bio.winona.edu/berg/Free.htm

the diffusion of water through a semi-permeable membrane

•Water moves freely through pores.

•Solute (green) to large to move across.

Water Potential – term for movement of water molecules as it undergoes osmosis

- The measure of the difference between the “force” that pushes water molecules and the “force” exerted by the membrane

Water solution with less solute (more diluted solution because of more water) = higher water potential

Water solution with more solute (more concentrated solution) = lower water potential

Water Potential Gradient - when 2 solutions of different water potentials are separated by a semipermeable membrane, thus allowing osmosis to occur

Osmotic Pressure – “force” that moves water molecules through a semi-permeable membrane

If the concentration of solute (salt) is equal on both sides, the water will move back in forth but it won't have any result on the overall amount of water on either side.

"ISO" means the same

In this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell, causing it to swell.The cell will gain water and grow larger. As osmosis continues, osmotic pressure builds up inside the cell causing cell lysis.

"HYPO" means less

In plant cells, the vacuoles will fill and the plant becomes stiff and rigid. The pressure exerted by the water molecule is called TURGOR PRESSURE, and the phenomenon TURGIDITY. The turgor pressure in plants will not result in cell lysis as the cell wall keeps the plant from bursting.TURGIDITY is important in maintaining the firm and erect position of a plant.

Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

• Osmosis Animations for

isotonic, hypertonic, and hypotonic

solutions

In this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction.Causes cells to shrink and lose shape because of water loss. In plant cells, the central vacuole loses water and the cells shrink, causing wilting (plasmolysis). In animal cells, the cells also shrink.In both cases, the cell may die.

"HYPER" means more

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)

Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

• Osmosis Animations for

isotonic, hypertonic, and hypotonic

solutions

shrinks

Passive Transport: 3. Osmosis

Tonicity – strength of a solution in relation to osmosis

3 Types:

IsotonicHypotonicHypertonic

Remember: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

What type of solution are these cells in?

A CB

Hypertonic Isotonic Hypotonic

•Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure.

•A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

•Salt water fish pump salt out of their specialized gills so they do not dehydrate.

•Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

* a process where a cell USES ENERGY or ATP to move molecules from a region of low concentration to a region of high concentration

* special proteins called carrier proteins often called pumps are used to move molecules from one side of the membrane to the other

high

low

This is gonna

be hard work!!

Example: Sodium -Potassium Pumps are important in nerve responses. They transfer Na and K ions in and out of the nerve and muscle cells.

Protein changes shape to move molecules: this requires energy!

1. EndocytosisPhagocystosisPinocytosisReceptor-mediated

2. Exocytosis

EXOCYTOSIS – going out of the cell ENDOCYTOSIS - going inside the cell

Pinocytosis:* a process where very large (too big to go through the plasma membrane) particles are "sucked in" to a cell, forming a vacuole.* "cell drinking"--uses energy (active transport)

1. Endocytosis: taking bulky material that can’t use transport proteins (like macromolecules) into a cell • Uses energy• Cell membrane in-folds

around the macromolecule to be transported

• 3 Types: Phagocytosis Pinocytosis Receptor-mediated

Endocytosis

ENDOCYTOSIS - going inside the cellPhagocytosis:* a process where a cell engulfs large undissolved particles, forming a vacuole* "cell eating"--uses energy (active transport)

Receptor-mediated Endocytosis – “cell drinking”

- Compared to pinocytosis, is very specific. The plasma membrane becomes indented and forms a pit. The pit lined with receptor proteins picks specific molecules from its surroundings. The pit will close and pinch off to form a vesicle which will carry the molecules inside the cytoplasm.

2. Exocytosis: Forces material out of cell in bulk• membrane surrounding

the material fuses with cell membrane

• Cell changes shape – requires energy

• EX: Hormones or wastes released from cell