BIO 151 FINAL EXAM EXAM QUESTIONS WITH CORRECT VERIFIED ANSWERS | 100% PASS (A+ CERTIFIED)

BIO 151 FINAL EXAM EXAM QUESTIONS WITH CORRECT VERIFIED ANSWERS | 100% PASS (A+ CERTIFIED) 1. Understand fermentation as an alternative mechanism to extract energy from glucose (with pyruvate as diversion point): under which circumstances does it occur? What are the advantages/disadvantages of fermentation Correct Answer Fer- mentation is an alternative to cellular respiration. Cellular respiration is dependent on oxygen. Fermentation starts with glycolysis. Pyruvate is something that the cells can use for more than respiration. Cells cannot do glycolysis and collect all of the pyruvates. There is an obstacle: NAD. Without oxygen during respiration, the cell runs out of NAD and glycolysis cannot proceed without the help of NAD. Fermentation is an attempt to regenerate NAD. Fermentation diverts pyruvate oxidation so that it doesn't enter the next steps. Fermentation can be either ethanol or lactic fermentation. Lactic is where pyruvate gets converted to lactate by an enzyme that simultaneously burns off NAD. So NAD that is regenerated can go back to glycolytic pathways that allow glycolysis to continue. Alcohol fermentation is where pyruvate gets converted into a 2-carbon molecule, acetahlyde, which spinoffs CO2, and this 2-carbon molecule gets converted into ethanol. Cells do this in situations where there's no O2. Oxygen is supplying this power to pull electrons away from glucose and to oxidize it into low energy compounds. 2. Under cellular respiration both in terms of its overall chemical equation (C6H12O6 + 6O2, etc) as well as a stepwise conversion process that harvests energy in glucose and stores as ATP Correct Answer The primary function of cellular respiration is to convert the potential energy of glucose into the potential energy of ATP. Glucose is not directly fueling anything in the cell. Glucose is like a 100-dollar bill. It has so much power in it and it's not the right size to fuel smaller reactions in the cell. Rather ATP is more of the right size to fuel these smaller reactions. Cellular respiration is converting the energy of glucose to energy of ATP for more widespread use. 3. Understand photosynthesis as overall the reverse of cellular respiration, and foundation for most life on earth Correct Answer Carbon fixation is photosynthesis absorbing carbon. carbons are used for energy and ATP and it's also used for monomers like amino acids and nucleotides. all forms of life are harnessed by the power of photosynthesis, so taking carbon out of the air and bringing it into glucose where it can be used for all kinds of cellular things. carbons fixation is pulling carbon from unusable form into a useful form for cells which is glucose. glucose can either be respired to make ATP or diverted to make carbon compounds. taking carbon dioxide and converting it into glucose and oxygen also known as photosynthesis is endergonic. cells are experts in doing endergonic things using exergonic things to fuel them. in this case, the exergonic process fueling this process is sunlight. 4. Understand the molecular interactions that hold the plasma membrane together, as well as why it does not fall apart/dissolve in water. (principle of self-assembly) Understand how the structure of the plasma membrane contributes to its selective permeability (semipermeability) Correct Answer The lipid has two layers which is known as lipid bilayer. lipids are largely nonpolar. both prokaryotes and eukaryotes have phospholipid bilayers. lipid bilayers have hydrophilic heads and two hydrophobic tails. hydrophilic heads are on the outside and hydrophobic tails are on the inside. water is on both the inside and the outside of the lipid bilayer. cytoplasms are largely watery and the environment that the cells are in is watery. These hydrophobic tails are the reason why the membrane won't dissolve and the cell won't fall apart. small nonpolar molecules can cross the membrane. oxygen can pass through the plasma membrane because oxygen is nonpolar. any molecule that has oxygen whether it's carbon-oxygen or hydrogen-oxygen bonds it would contribute to that molecule being polar. 5. Understand osmosis as the diffusion of water, that is influenced by the relative tonicity on 2 sides. Know the tonicity of animal cells; also 2 applications of osmosis principles (transport of water across plant roots; requirement for saline in IV bags) Correct Answer Osmosis is the diffusion of water. tonicity refers to the relative concentration of a solution compared to another solution. hypotonic means less concentrated than the solution. hypertonic means more concentrated than the solution. isotonic means similarly concentrated then solution. when cell is hypertonic (more concentrated than solution ), Osmosis occurs in the water will swell. when the cell is hypertonic, so will shrink and shrivel.Animal cells are isotonic with their surroundings. plant cells are hypotonic; In particular their roots are hypertonic. they need to bring in water through their roots. human cells swell and Burst when they are put in water but plant cells are happy if they got the swelling pressure going on. in hypotonic solution plant cell swells and runs up against the cell wall and is happy. plant cells are hypotonic but they like to be hypertonic to acquire water for roots. if plant cells are in isotonic solution, they will wilt. supplying water to the roots will cause water to enter via osmosis, swelling the cells of the plants. 6. Know the relative distributions of K+, Na+ ions across the plasma membrane.- : Proteins are Machines of the cell that get things done and one of the things that they do is to pump stuff back and forth. since ions cannot cross the bilayer, they have to go through a protein. they also need to be moved against the gradient. proteins help with this process by burning fuel to move ions. this process is fueled by atp. Concentration gradients are a form of free energy so to create them the cell will have to spend or burn the energy. potassium is High inside the cell whereas sodium is high outside. to push all the sodium ions out the cell is endergonic. for cells to move ions out requires energy because it's moving up the concentration gradient. maintaining these gradients is also using enormous amounts of energy. cells are Masters at harnessing and using energy including driving endergonic processes such as making large macromolecules and creating and maintaining ion gradients. 2K+ in and 3Na+ out for every ATP. 7. Be able to predict diffusion of substances across membranes, based on both molecular/ion structure and concentrations Correct Answer Diffusion will spontaneously occur when concentration on one side is higher than concentration on the other side. there is going to be the spontaneous movement to low concentration of having an effect of equalization. this process is unstable, is low entropy, and these molecules are essentially pushing to get to the other side. these molecules on the concentrated side want to move to the unconcentrated side. concentration gradient is the difference in solute concentrations across a membrane. solutes move randomly in all directions but when a concentration gradient exists, there is a net movement from regions of high concentration to regions of low concentration. diffusion down a gradient or away from high concentration is spontaneous because it increases entropy. solutes being potassium and sodium ions cannot cross the membrane by themselves. the molecule that has the most difficult time crossing the membrane are ions. Random processes of diffusion will equalize and unseparate the two separated solutes.