Bio 160

1. Bio 160 Unit 2 – 1 Week Two- Lecture One

2. Cellular Functions • Thermodynamics and energy • is the capacity to do work • Kinetic - actual work • Potential - stored work • Heat - given off from the movement of molecules • Chemical - stored for cells

3. Thermodynamic laws- energy transformations • 1st law- energy can neither be created nor destroyed, but it may change form • 2nd law- law of entropy- energy transformation results in chaos of randomness. (entropy) • Implication for the 1st law • Energy that comes to us from the sun can be transferred into many different forms through different systems

4. Implications for the 2nd law • As one environment becomes more organized, all around it becomes disorganized • Disorganized energy is heat • A cell creates an ordered space, increasing the entropy around it, so it can not be transfer or transform energy 100% efficiently, therefore energy can not be transferred 100% through a system. Most is given off as heat

5. Chemical reactions store or release energy • Endergonic reactions require energy to be put into the system, then stores energy in the chemical products. (ex. Photosynthesis) • Exergonic reactions release energy out of the system from energy rich bonds being broken in the reactants. (ex. Cellular respiration)

6. Cellular Metabolism- all of the endergonic and exergonic reactions of a cell • ATP- adenosine triphosphate powers nearly all forms of cellular work • Obtained from food molecules • Energy coupling reactions for cellular metabolisms are run by ATP • ATP is a little unstable, so it can be broken down to ADP through hydrolysis • A phosphate is removed, releasing energy (dephosphorylation)

7. Exergonic reaction • Phosphorylation- ADP receives a phosphate converting it to ATP, energizing it to perform work • Dephosphorylated ATP is converted to ADP: adenosine diphosphate by the removal of a phosphate, releasing energy for the cell to do work. • During cell respiration ADP is phosphorylated through dehydration synthesis and converted back to ATP. Therefore it is renewable source.

8. Enzymes control the rate of chemical reactions without being consumed or changed in any way. (Biological catalyst protein) • Works by lowering the energy barrier or the energy of activation energy needed to start a reaction • The enzyme has no effect on the amount of energy content of reactants or products, just on the rate of the reaction. • Enzymes are very specific in where they work • Use a “lock and key” mechanism. The active site on the enzyme must have the appropriate “fit” with receptor site on the protein substrate

9. Enzymes require a specific environment to function optimally. (Temp, pH, salinity, etc.) • Some enzymes also require a non-protein cofactor or coenzyme (organic molecule) to function properly. • Enzymes may be blocked from their substrates by inhibitor chemicals • Competitive inhibitor- competes with the enzymes normal substrate, tying up the enzyme • Non Competitive inhibitor- binds to the enzyme outside of the active site, changing the shape of the enzyme, preventing the enzyme from fitting with its own substrate • Inhibitors regulate cell reaction rates by slowing it down • Negative feedback regulation of metabolism

10. Cellular Membranes • Cellular Membranes control cellular metabolic functioning • Phospholipid bilayer made of a mosaic of different small fragments that can move laterally in the membrane • Membranes are selectively permeable, allowing certain substances in and out, but not others. • Types of movement across cell membranes • Passive Mechanisms allow movement without the use of energy

11. Diffusion- molecules moving from areas of [] to [] through random molecular motion • Passive Transport- diffusion of a substance across a membrane along a [ ] gradient until equilibrium is reached • Osmosis- diffusion of water molecules across a selectively permeable membrane • When water molecules can move across a membrane but the solute cannot, different concentrations of solutes may result • Hypertonic- a solution with a higher [ ] of solutes in it that the surrounding solution is considered to by hypertonic it its solution

12. Hypotonic- A solution with a lower [ ] of solutes in it than the surrounding solution is said to be hypotonic to its solution • Isotonic- the [ ] of solute is the same on both sides of the membrane • In all of the solutions, water will cross the s.p. membrane to reach equal concentrations. The direction of osmosis is determined only by the difference in total solute [ ]. • Water balance is controlled by osmoregulation • Facilitated diffusion- a special protein embedded in the cell membrane called a transport protein regulates the diffusion of larger molecules down their [ ] gradients, thereby facilitating the diffusion

13. Active transport mechanisms require cell energy to move substances across the membrane. Uses ATP phosphorylation to activate transport protein • Exocytosis- cellular expulsion of molecules using cellular energy • Endocytosis- cellular intake of macromolecules using cellular energy • pinocytosis-cellular intake of fluid droplets • phagocytosis- engulfing of large particles from outside the cellular membrane • receptor- mediated endocytosis- engulfing of specific molecules through the use of receptor proteins

14. Cellular Respiration • The process of creating ATP the organism needs by using the materials the body takes in • Overall process

15. Cells only use 40% of energy released from glucose. Other 60% lost as heat • During the chemical conversion process of the reaction, e- are released from one set of molecules and are attached to others, giving off energy in the process • Accomplished by H atoms moving places (fig. 6.4) • H carried by NAD+ (nicotinamide adenine dinucleotide) through an oxidation-reduction (redox) reaction • 2 hydrogens and 2 e-’s are first peeled off of a glucose molecule in an oxidation reaction (loss of e-)

16. The H and 2 e- are shuttled through the oxidation by NAD+ coenzymes and dehydrogenase enzyme • NAD+ becomes reduced, picking up H+ and 2 e- becoming NADH. The other H+ goes into the fluid surrounding the cell • The energy from the redox reaction is released when NADH releases its e- carriers to become NAD+ again • the NADH stores the energy for the cell • The e- carriers “fall” down a series of energy level carriers like a stair step • Called electron transport chain (e- “dance”) • The e- carrier proteins (levels) are imbedded in mitochondrial membranes of the cristae

17. 2 mechanisms to generate ATP • Chemiosmosis- uses concentration gradients and ATP synthatase proteins found in membranes to generate most of their ATP • Substrate level phosporylation- without a membrane, transfers a phosphate group from an organic molecule to ADP, happens in the conversion of glucose to CO2 in the Kreb’s cycle

18. 3 stages of Cell Respiration (fig. 6.8) • Glycolysis- splitting of sugar anaerobically • Occurs in cytoplasm without oxygen needed\ • Oxidizes glucose into pyruvic acid through 9 chemical steps • 2 separate stages of glycolysis • First stages are preparatory and consume energy • ATP is used to split one glucose into 2 smaller sugars that are primed to release energy • Since the prep phase uses 2 ATP, only 2 ATP are the end product generated by glycolysis • Produced through substrate- level phosphorylation • 2 molecules of NAD+ are reduced to NADH • 2 ATP are available for immediate use by the cell • NADH must enter electron transport system for E to be released • Must have O2 to release E

19. Second stages release energy • Happens in tandem • NADH is produced when a sugar molecule is oxidized and 4 ATP are generated

20. Total end products of glysolysis: 2 ATP + Heat + 2 pyruvic acid • Kreb’s Cycle- aerobic respiration • Pyruvic acid must be groomed to enter the Kreb’s Cycle • It is oxidized while a molecule of NAD+ is reduced to NADH • A C atom is removed and released in CO2 • Coenzyme A joins with what is remaining of the pyruvic acid to form AcetylCoenzyme A • The acetyl part then enters the kreb’s cycle, the coenzyme A splits off and is recycled

21. Kreb’s cycle happens in the cristae of the mitochondria • Acetyl fragment combines with the oxaloacetic acid already in the mitochondria • This forms citric acid. A molecule of CO2 is released and NAD+ is reduced to NADH, which releases an e- to the electron transport system • Citric acid is converted to alpha- ketoglutaric acid, phosphorylated to produce ATP and NAD+ is reduced to NADH, again releasing an e- to the electron dance. Four-carbon succinic acid results.

22. At succinic acid, enzymes rearrange chemical bonds FAD, a related hydrogen carrier similar to NAD, is reduced to FADH, releasing more e- to the electron dance. Malic acid is formed (FAD= flavin adenine dinucleotide) • At malic acid NAD+ is reduced to NADH and a H+ ion, adding more e- to the dance. Malic acid is converted to oxaloacetic acid, which is ready to accept a new acetyl group for another turn at the cycle • End products of Kreb’s: 36 ATP + CO2 + HEAT • 2 ATP are from substrate- level phophorylation

23. Approx 34 ATP are formed by chemiosmotic phosphorylation • The electron transport chains are built into the convoluted cristae of the mitochondria, there are many sites for the electron dance to occur • Electron transport system is third stage of cellular respiration • Pathways for dietary carbohydrates, lipids and proteins • Carbohydrates break down into sugars that eventually break down into glucose and then goes into glycolysis • Quick access energy

24. Lipids are broken down through hydrolysis into fatty acids and glycerol • Fatty acids may be stored as fat, be converted into ketone bodies (acetone) and further broken down to enter the Kreb’s or eliminated, or undergo beta- oxidation and be converted straight into Acetyl Co A • Glycerol may be converted into Acetyl Co A and enter the Kreb’s or be converted to glucose and undergo glycolysis • Yields high energy when used but likes to be stored rather than used • 2x as much ATP as in the same amount of starch

25. Proteins undergo hydrolysis to break into amino acids that are then broken into deaminated portions which can go to fat, glucose, and acetyl Co A to enter glycolysis/Krebs cycles. The other portion of the amino acid is the NH2 (Ammonia) group, which is excreted through urea • Long term energy- takes long time to digest • Food Molecules are used for other stuff besides Kreb’s Cycle • Used for biosynthesis (uses ATP to do so) • Produces proteins, lipids, and polysaccharides • Used for growth and repair