The Working Cell: Energy Formation and Usage Energy—The capacity to perform work. Two Types: Potential- stored energy that is not doing work but can. Example: racehorse in starting gate, gas in car tank, couch potato watching tv Kinetic- energy of motion. Example: racehorse running down track, car moving down road, couch potato studying Biology Two Laws of Energy: 1. Energy cannot be created or destroyed, it can only be converted from one form to another. 2. During conversion, some energy is lost as heat. This increases the “entrophy”, or disorder, of the universe.

Ultimate source of all energy is the: SUN Nearly all energy processes can be traced back to the sun. plants start the process by absorbing the light and turning it into sugars that are passed down the food chain.

ATP used to power cellular work. ATP = Adenosine Tri-Phosphate -nucleotide -energy is located in between phosphate bonds -by removing a phosphate the ATP molecule releases energy much like a spring after you have compressed it. - ATP – P = ADP (Adenosine di-phosphate) + a free P Body recycles the entire supply of ATP about 1 x every minute. One teaspoon of ATP provides enough energy to do about 15 minutes of moderately strenuous activity. Average Joe uses about 408 lbs of ATP/24 hr period.

We can recycle the free P by using some of the energy released during the first reaction to reattach it to an ADP molecule. This process is called “phosphorylation” and is important in helping keep the energy process in your body going. Build ATP with energy harvested from fuel molecules in the cell… like glucose. Break down ATP to provide the cell with energy to carry out various cell functions.

Enzymes…Again!! Review: -catalysts…speed up chemical reactions -belong to protein class of macromolecules -lower the activation energy of reactions Specific shapes of enzymes only allow them to catalyze one type of reaction. ENZYMES ARE NOT INTERCHANGABLE.

Each reaction has a specific enzyme that will fit with a SUBSTRATE at the ACTIVE SITE and cause the reaction to happen. Enzyme/Substrate complex is much like a lock and key. Any change in the shape of one prevents the lock from opening. Sometimes products are formed by enzyme- substrate reactions like proteins formed by amino acids joining. Sometimes substrates are broken down by enzyme- substrate reactions (like complex carbohydrates such as table sugar being broken down to glucose)

Inhibitors can block reactions from happening. Competitive Inhibition (a) -inhibitors take the place of the enzyme. They mimic the shape and combine with the substrate at the active site before the enzyme does preventing the enzyme and substrate to combine properly. Example: same key fits two different locks, but only turns one of them Non-Competitive Inhibition (b) -inhibitors attach to the enzyme at a site remote to the active site which doesn’t affect the substrate but does change the shape of the active site so the substrate no longer fits the puzzle. Example: key gets smashed and no longer fits the lock so it cannot turn it ve_inhibit_c_la_784.jpg

Practical Application of Enzymes: Penecillin, the “wonder drug” produces an enzyme that inhibits the formation of a cell wall in bacteria. Without the protection of a cell wall, white blood cells can attack the bacteria. Since humans don’t share enzymes with bacteria, we can use it without causing harm to any body cells. Many insecticides used to kill insects are enzymes that inhibit various functions in the body, such as nervous system functioning. They can do the same thing to the human nervous system that they do to insect nervous systems. Cyanide inhibits O 2 movement in all organisms. p-content/uploads/2011/08/bug- spray.jpg

Using Energy to Move Things Into and Out of the Cell Movement into and out of the cell can happen with or without E. Movement that requires energy is called: ACTIVE TRANSPORT- -use energy to push molecules against the concentration gradient…in other words…you are trying to fill up a space that is already full. -imagine rowing a canoe upriver, against the current -important in keeping the cell “balanced” with some molecules…Sodium/Potassium pump in muscle cells helps keep nerves going. -energy usually comes from ATP -Fig. 5.15, pg. 82

Other movement across the cell membrane requires no E. This is called PASSIVE TRANSPORT. -Movement is with the concentration gradient. No energy is needed to “go with the flow.” -Imagine rowing a canoe down river with the current. Different Types of Passive Transport: DIFFUSION: -movement of molecules from areas of higher concentration to areas of low concentration -Examples: iced tea in a pitcher of water, O2 and CO2 in the blood being exchanged, methane gas moving into the air when released by the bowels, i.e. farting.

Water moves by diffusion in a class of it’s own. It is the only molecule that has free passage across the cell membrane. Thus: OSMOSIS -is the movement of water from areas of higher concentration to areas of lower concentration. -controls both solute concentration and volume in cells. Isotonic cells have equal amounts of solute and water both inside the cell membrane and outside the cell membrane. Thus, there is no net movement of water across the membrane. Most cells desire to be isotonic. APPLICATION: Blood has an isotonic saline concentration of 0.9%. When hospitals give you an I.V., they use 0.9% saline so they don’t upset the isotonicity of the blood.

Solute=50% H2O=50% Solute=50% H2O=50% Equal exchange Isotonic Cell Fluid Exchange

Cells that are: -HYPERTONIC have more solutes outside the cell than inside the cell. Example: salt water in ocean. -by osmosis, water must move from inside the cell to outside in order to balance the solution and volume. -loss of water will cause the cell to shrink or crenate -animal cells will lose shape and become limp -plant cells lose shape and become flaccid…this is when plants wilt

High solute conc. Low water conc. Water will leave the cell in an attempt to create an isotonic situation. Hypertonic Cell Fluid Exchange Low solute conc. High water conc. The cell will shrivel up or “crenate” due to a loss of water.

Cells that are: HYPOTONIC have more solutes on the inside of the cell than on the outside. Thus, water moves into the cell by osmosis. Animal cells will swell and burst or lyse. Plant cells become “turgid” (develop turgor pressure) and look healthy. They cannot burst due to the strength of the cell wall.

High water conc Low solute conc Water will enter the cell very rapidly in an effort to provide an isotonic environment. Hypotonic Cell Fluid Exchange This will cause animal cells to swell and burst. Plant cells just become more turgid. Low water conc High solute conc Low water conc High solute conc

Review: Can you identify the characteristics of each set of cells? Isotonic Hypertonic Hypotonic Explain how you can easily die of thirst if you get lost on the ocean? Sodas usually won’t quench your thirst. Why not? What organelle do plants store water in to make them turgid? How do protists that live in fresh water ponds and lakes avoid bursting because of the environment they live in?