 Why is it important that muscle cells contain more mitochondria than skin cells do?

The Cell Membrane and Transport

The Plasma Membrane - S.J. Singer proposed the Fluid Mosaic Model to describe the cell membrane The membrane is semipermeable (imagine a fence or screen door) The phospholipid bilayer

Isolate the cytoplasm from the external environment Regulate the exchange of substances Communicate with other cells Identification

1. The plasma membrane is a phospholipid bilayer with embedded proteins.

Phospholipids have both hydrophilic and hydrophobic regions; nonpolar tails (hydrophobic) are directed inward, polar heads (hydrophilic) are directed outward to face both extracellular and intracellular fluid

The proteins form a mosaic pattern on the membrane. Cholesterol - stiffens and strengthens the membrane. Glycolipids - protective and assist in various functions. Glycoproteins - have an attached carbohydrate chain of sugar that projects externally

Proteins embedded in membrane serve different functions Transport Proteins - regulate movement of substance

Channel Proteins - form small openings for molecules to diffuse through Carrier Proteins- binding site on protein surface "grabs" certain molecules and pulls them into the cell Gated Channels - similar to carrier proteins, not always "open" Receptor Proteins - molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins), binding site Recognition Proteins - ID tags, to identify cells to the body's immune system Enzymatic Proteins – carry out specific reactions

Membrane Permeability  Transport Across Membrane *Selectively or Differentially permeable – some things can cross, not others What things can pass? What cannot pass?

 Small lipophilic (lipid soluble) molecules that cross the membrane by diffusion alone  Molecules that cross the membrane due to protein-mediated transport  Molecules, usually of very large size, that do not cross the membrane at all

Passive Transport (no energy) Simple Diffusion - water, oxygen and other molecules move from areas of high concentration to areas of low concentration, down a concentration gradient

Substances that diffuse across cell membranes include gases, such as O 2 and CO 2, and small relatively hydrophobic molecules, such as fatty acids or alcohols. By contrast, it is difficult for water to cross pure phospholipid membranes

Facilitated Transport (Diffusion) - diffusion that is assisted by proteins (channel or carrier proteins)

Facilitated diffusion- movement of specific molecules across cell membranes through protein channels Facilitated diffusion- movement of specific molecules across cell membranes through protein channels There are two types: There are two types: Channel protein- allow water to cross membrane Channel protein- allow water to cross membrane Carrier proteins- bind to specific solutes and “carry” them across Carrier proteins- bind to specific solutes and “carry” them across

Large molecules, such as proteins, polypeptides, polysaccharides, or nucleic acids, do not diffuse across cell membranes at all. These molecules must be broken down into their component monomers

Diffusion is how oxygen enters our bloodstream.

 List and describe two different types of proteins found in the cell membrane.

Osmosis - diffusion of water. Osmosis affects the turgidity of cells, different solution can affect the cells internal water amounts Contractile Vacuoles are found in freshwater microorganisms - they pump out excess water Turgor pressure occurs in plants cells as their central vacuoles fill with water. Salt Sucks! Simple rule of osmosis

See the movement of water molecules through protein channels in the cell membrane in isotonic solution. Note that the number of water molecules on both sides of the membrane remains essentially unchanged

Within the cell, there is a higher concentration of solute (salt) This causes water to be "sucked" into the tube. The solution in the beaker is HYPOTONIC

Hypotonic- “below strength”- when water molecules inside cell increases. Cell will swell as a result

Within the cell, there is a lower concentration of solute (salt) This causes water to be "sucked" out into the beaker The solution in the beaker is HYPERTONIC

Hypertonic- The number of water molecules inside the cell decreases with time, and the cell shrinks as a result.

Isotonic - no net movement Hypotonic - water moves into the cell, cell could burst Hypertonic - water moves out of the cell, cell shrinks

 Matching: 1. Moves small molecules across the plasma membrane using transport proteins 2. Involves water moving across the plasma membrane to the side with the greater solute concentration 3. Occurs when substances move against the concentration gradient; requires energy and the aid of carrier proteins 4. The condition that results when diffusion continues until the concentrations are the same in all areas a. Osmosis b. Facilitated diffusion c. Dynamic equilibrium d. Active transport

Whats the difference?- ACTIVE NEEDS ENERGY!!!

Passive Transport - requires no energy (diffusion, osmosis) Active Transport - requires the cell to use energy (ATP)

 Active transport of molecules across a cell membrane is generally carried out by transport proteins or “pumps” that are found in the membrane

- involves moving molecules "uphill" against the concentration gradient, which requires energy Endocytosis - taking substances into the cell (pinocytosis for water, phagocytosis for solids)

Receptor ‑ mediated endocytosis, a form of pinocytosis, occurs when specific receptor helps substances across

Exocytosis - pushing substances out of the cell, such as the removal of waste

SODIUM POTASSIUM PUMP

 Needs three sections:  Cell membrane  Diffusion  Osmosis  Inside of flap needs  ATLEAST 3 Definitions of terms  Drawings  Needs to be in color