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Exam 2 Biology
Terms in this set (65)
What is energy?
The capacity to do work
We discussed five different forms of energy. What are they? Which form of energy is the least "useful" to do work?
Light, Electricity, Heat ***, Kinetic (Movement), Potential (Location)
Why does a cell need energy?
Move things, Metabolism (breaking and making molecules), Transport things across borders (cell membranes).
How does a cell store energy?
A cell stores energy in chemical bonds between atoms of molecules (chemical energy), Chemical energy is a form of potential energy.
What is "chemical" energy? What are some molecules that store a lot of chemical energy?
Certain organisms capture the energy from the sun and convert that into the chemical energy of food, gasoline, and other fuels (photosynthesis). Chemical energy is stored in the bonds between atoms of a molecule.
What are the similarities between the combustion of gasoline of a car and the cellular respiration of food in a cell? What are the reactants and products of these two reactions? Which reaction is more efficient? In what form is the resulting energy in combustion and cellular respiration?
Both take in hydrocarbons and oxygen to make energy that then gives off heat and has the same products given off. The reactants are Hydrocarbons and Oxygen the products are carbon dioxide and water. Cellular respiration is more efficient. Combustion uses the energy for movement, Cellular respiration uses the energy for cellular work.
What are the first and second laws of thermodynamics?
1st=Energy cannot be created or destroyed. It can be converted from one form to another and thus transferred between objects or systems. 2nd= Energy tends to disperse spontaneously. A bit disperses at each energy transfer, usually in the form of heat.
What is the purpose of ATP? Through which process is it made? Where in the cell is it made? What is the structure of ATP? Which bond in ATP stores its energy? What are the products of breaking down ATP to extract its stored energy? Explain the cycle of ATP and ADP + P.
ATP is the energy currency of the cell; "carries". energy Is made through a process called cellular respiration. Is made in mitochondria. Consists of adenosine plus a tail of three phosphate groups (adenosine triphosphate). Energy is stored in the bond to the third phosphate; when that bond is broken energy is released and the resulting molecule is called adenosine diphosphate (ADP). ATP is constantly made from, and broken down into, ADP and phosphate.
What are the definitions of reactants and products of chemical reactions? Is energy needed for or released by chemical reactions?
Reactant-Molecule that enters a reaction. Product-A molecule remaining at the end of a reaction. Some reactions require a net input of energy - others end with a net release of energy.
In a chemical reaction, what happens to the atoms in the reactants as product is formed?
The number of atoms remains constant in a chemical reaction.
Are chemical reactions reversible? Describe the flow of energy as you reverse a chemical reaction.
Yes, the flow of energy to create a product is given off, but in the reversal process, energy is taken in.
What is activation energy? Do reactions that overall release energy still require the input of "activation energy" to get started?
Activation Energy: Minimum amount of energy required to start a reaction. Yes they do.
What is an enzyme? What is the function of an enzyme? How do we name enzymes? What does an enzyme bind, and where does it bind? What is meant by the concept of enzymes specificity?
Enzymes are catalysts that start up a reaction without being changed by it (can be used over and over again). Enzymes are proteins(RNA's). Many enzymes are named for their substrates but with an "ase" ending. Substrates(reactants) bind enzymes to an active site. Each enzyme is very selective; catalyzes specific reactions.
What is the concept of induced fit?
The active site fits to the substrate, and the enzyme changes shape slightly. (wiggles)
How can an enzyme be used over and over again (without being consumed in the reaction it catalyzes?)
The enzyme does not get used up in the reaction. Nothing gets changed to the enzyme. (lock and key)
What are some factors that influence enzyme activity?
Each enzyme works best within a characteristic range of temperature, pH, and salt concentration.
What are the two types of enzyme inhibitors and how do they work?
1."Imposter" inhibitor: pretend to be an enzyme. 2. Remote site inhibitor (allosteric inhibitor): changes the active site for an enzyme to enter.
What is a metabolic pathway? What are the two types of metabolic pathways discussed in class?
Metabolic pathway-Series of enzyme-mediated reactions by which cells build, remodel, or break down an organic molecule. Metabolic pathways can be linear or cyclical.
Describe the concept of selective permeability of the plasma membrane.
Membrane property that allows some substances, but not others, to cross.
What is a concentration gradient?
Difference in concentration of a substance between adjoining regions of fluid.
What is diffusion?
Molecules move from an area of high concentration to an area of low concentration.
Name two factors that might influence the rate of diffusion.
1. Size, 2. Temperature, 3. Steepness of the concentration gradient, 4. Charge, and 5. Pressure
What is osmosis?
Osmosis is the diffusion of water across a selectively permeable membrane from the region with a lower solute concentration (hypotonic) toward the region with a higher solute concentration (hypertonic).
Describe a hypertonic, hypotonic, and isotonic solution.
A hypertonic solution: Has a higher concentration of solute(shrink). A hypotonic solution: Has a lower concentration of solute(swells). An isotonic solution: Has an equal concentration of solute.
What happens to a cell when placed into a 1) hypertonic solution, 2) hypotonic solution, and 3) isotonic solution?
A hypertonic solution:shrivels up; more water moves out. A hypotonic solution: swells; more water diffuses into. An isotonic solution: does not change; stays the same.
What are transport proteins?
Gases, water, and small nonpolar molecules can simply diffuse across a lipid bilayer (in the case of water this is called osmosis) .Most other molecules and ions cross only with the help of transport proteins, which gives a control over which substances enter and exit.
What are some differences and similarities between passive and active transport?
Passive transport-Concentration gradient drives a solute across a cell membrane through a transport protein. Requires no energy input. Active transport-A transport protein use energy, usually from ATP, to pump a solute across a cell membrane against its concentration gradient.
What is exocytosis and endocytosis? What kind of molecules enter and leave cells through these two processes? What happens to the plasma membrane during these processes?
Endocytosis:Takes molecules into the cell. Exocytosis:Secretes molecules outside of the cell. Exo(Macromolecules), Endo(Microorganisms). Patches of membrane constantly move to and from the cell surface as vesicles that fuse with or pinch off from the plasma membrane.The lipid bilayer reseals itself when the membrane is disrupted.
What is phagocytosis? Name an example of a cell using phagocytosis.
Phagocytosis ("cell eating")Endocytic pathway by which cells like white blood cells engulf particles such as microbes or cellular debris(Amoebas).
What is photosynthesis? What is the purpose of photosynthesis?
Chemical reactions that use the energy in light to make "food" from carbon dioxide and water. Food provides us with energy and "building block" molecules.
What are the three types of organisms that do photosynthesis? Name an example of each.
Almost all plants undergo photosynthesis, as well as some bacteria and protists. Plants(moss, ferns); Bacteria(Cyanobacteria); Protists(Algae, kelp).
What are autotrophs and heterotrophs? Name some examples of each.
Autotrophs: Producers, Organisms that make their own organic molecules (glucose) from inorganic ones (CO2) Photosynthetic organisms. Heterotrophs: Consumers, Organisms that cannot make organic molecules from inorganic ones.Us!
What is a pigment? What part of the pigment molecule absorbs light?
pigments: are organic molecules that can absorb light of certain wavelengths.The most common pigment in photosynthetic organisms is chlorophyll, which absorbs red and blue light.
Why are plants green? Does a longer or shorter wavelength of light carry more energy? Which wavelength (color) of light does chlorophyll use for photosynthesis (absorb) and which wavelength (color) of light is of no use to chlorophyll and thus gets reflected?
Plants are green because they contain a substance called Chlorophyll. Green gets reflected instead of absorbed. The shorter the wavelength, the more energy it carries. It absorbs red and blue.
Which wavelength (color) of light gets used (absorbed) by the pigment beta-carotene and which wavelength of light (color) gets reflected by beta-carotene; i.e.: why do leaves turn red and yellow in the fall?
it absorbs blue and reflects a yellow-orange color. There is a decreased level of green chlorophyll.
In what organelle does photosynthesis occur? This organelle is bound by how many membranes? Be able to label the different parts of this organelle.
Chloroplasts, bound by 2 membranes. Stroma and Thylakoid*KNOW LOCATION.
Memorize the overall equation of photosynthesis. What are the reactants and what are the products? Where is the energy stored after photosynthesis?
(reactants) 6CO2 + 6H2O ------> C6H12O6 + 6O2 (products) convert light energy into chemical energy which can be stored in the molecular bonds of organic molecules (sugars).
Compare and contrast the two different parts of photosynthesis. Which part "makes" energy? Which part fixes carbon? Where do these two parts take place? What are the light requirements? Are the pathways in each part linear or cyclical?
1. Light Reaction (Light-Dependent Reaction):Thylakoid Membrane, Two pathways: non-cyclical and cyclical, "Make" energy (ATP),Oxygen is a byproduct. 2. "Dark" Reaction (Light-Independent Reaction):Stroma, Calvin-Benson Cycle, Carbon fixation (CO2 to glucose; make building blocks), ATP energy put into glucose. Non-cyclic(linear) is light dependent(light reaction) while cyclic is light independent(dark reaction).
What are photosystems and be able to name two.
Photosystems:The thylakoid membrane has clusters of pigments/proteins. photosystem I and photosystem II. Photosystems contain special chlorophyll pigments that release/excite electrons when hit by light. (Cyclic or non-cyclic)
A. What are the two different pathways of the light reaction? Describe each.
A. Cyclic or Non-cyclic. A cyclic pathway: runs in type I photosystems to make ATP; electrons are cycled back to the photosystem. The non-cyclic pathway: Electrons are excited from photosystem II and then photosystem I, at the end the electrons are "dumped" onto NADP+, Electrons DO NOT cycle, but need to be replaced.
Why is the "dark" reaction called "dark" reaction? Does it always occur at night? What is the product of the dark reaction?
It does not require light for the reaction to occur. No, it doesn't always occur at night. The product is glucose.
What is carbon fixation and by which process does it occur?
Glucose (organic molecule) is made from CO2 (inorganic molecule). Uses the energy of molecules formed in the light-dependent reaction (ATP, NADPH). Carbon is fixed in the Calvin-Benson Cycle.
Describe the Calvin-Benson Cycle. What is the name of the primary enzyme? What are the reactants and the products? How many CO2 molecules get "fixed."
In stroma:The energy from the ATP and NADPH made in the light-dependent reaction is used to make glucose. Rubisco is the primary enzyme. Six carbons from six CO2 molecules make one glucose molecule.
What process do cells use to extract the chemical energy stored in food (specifically glucose)?
Cellular respiration is a chemical process that harvests energy (in the form of ATP) from organic molecules.
Which organisms use cellular respiration? In other words, do plant cells contain mitochondria?
Many organisms (including plants and animals). yes.
Memorize the overall equation of cellular respiration. What are the reactants and what are the products? What is the overall purpose of cellular respiration? What happened to the energy that was stored in glucose? Where does it occur?
(reactants) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy(ATP) (products). To capture energy contained in the bonds of glucose in molecules of ATP. Harvests energy (in the form of ATP) from organic molecules(glucose). Cellular respiration occurs in mitochondria (in eukaryotic cells).
How does cellular respiration compare to photosynthesis?
The formula is reversed and instead of taking in energy for photosynthesis, cellular respiration releases or gives off energy.
How do nutrients cycle and how does energy flow out of a system?
Photosynthesis takes in energy to produce glucose(sugars) and O2. Then we breath out using Aerobic respiration, which gives off energy producing carbon dioxide and water. Which plants can use for Photosynthesis, starting the cycle over again.
After cellular respiration the six carbons that were present in glucose are now in six molecules of_____________.
What is the sole purpose of oxygen in cellular respiration? After fulfilling this purpose oxygen is converted to this molecule
Water(H2O). Oxygen is an electron grabber in chemical reactions. Oxygen atoms have a stronger pull on electrons than almost any other type of atom.
Describe the exchange of molecular oxygen and carbon dioxide between an organism like a human and its environment. What is the purpose of breathing?
Oxygen is taken into the human body through breathing in and is released into the environment by means of exhaling. The primary purpose of breathing is to supply the body with oxygen and to remove excess carbon dioxide.
What are the three parts of cellular respiration and where in the cell do they occur? How much ATP is produced in each step?
Glycolysis: in Cytoplasm, 2ATP; 2nd Stage(Krebs Cycle): in Mitochondria, 2ATP; Electron Transport Chain: in Mitochondria, 32 ATP.
Describe the location of the electron transport chain. What happens to the electrons carried to the electron transport chain by the coenzymes? Describe the involvement of hydrogen ions in the electron transport chain.
In the Mitochondrion. The reduced coenzymes give up electrons and hydrogen ions to electron transfer chains in the inner mitochondrial membrane. Energy lost by the electrons as they flow through the chains is used to move H+ across the membrane. The resulting gradient causes H+ to flow through ATP synthases, which drives ATP synthesis.
What is the fundamental difference between cellular respiration and fermentation?
Cellular Respiration requires Oxygen unlike Fermentation.
What are the two types of fermentation pathways we discussed? Name some organisms that use these fermentation pathways.
Lactic Acid Fermentation(Human muscle cells and bacteria) and Alcoholic Fermentation(yeast).
Which results in more energy for our muscle cells: glucose undergoing cellular respiration or glucose undergoing fermentation? Exactly how much more efficient is the one process over the other? Why do we then even bother with the other process?
Cellular respiration. 18x more efficient than the other(36 to 2). Bacteria produce lactic acid during fermentation, which gives cheese, yogurt, and sour cream their sharp or sour flavor. Also in Alcoholic Fermentation makes bread, beer, and wine.
What is the reactant and product of lactic acid fermentation? What happens to the electrons that got placed onto NAD+ (making NADH)? How many ATP result from lactic acid fermentation? Which one of the three processes of cellular respiration is also used for lactic acid fermentation?
Reactants= 2 pyruvic acid, 2 NADH.
Products= 2 NAD+, 2 lactic acid. It's oxidized to NADH and then reduced to NAD+ by removing two electrons., It's reduced to NADH and then oxidized NAD+ by removing one electron. A net two ATP result from lactic acid fermentation. Glycolysis is the process used for lactic acid fermentation.
What is the reactant and what are the products of alcoholic (ethanol) fermentation? How many ATP get produced? Which molecule accepts the electrons from the NADH produced in glycolysis? Follow the fate of the six carbons in glucose as they go through alcoholic fermentation.
Reactants= 2 pyruvic acid, 2 NADH. Products=CO2, ethanol. It produces two moles of ATP. Pyruvate accepts the NADH produced in glycolysis.
What are some commercial uses of lactic acid and alcoholic fermentation?
Bacteria produce lactic acid during fermentation, which gives cheese, yogurt, and sour cream their sharp or sour flavor. Also in Alcoholic Fermentation makes bread, beer, and wine.
Compare and contrast lactic acid and alcoholic fermentation.
Lactic Acid Fermentation: Without enough oxygen, muscle cells break down glucose to produce lactic acid; Lactic acid is associated with the "burn" associated with heavy exercise; If too much lactic acid builds up, your muscles give out. Alcoholic fermentation: Anaerobic pathway that converts pyruvate to ethanol and produces ATP. Both ethanol and lactic acid fermentation results in only 2 ATP (through glycolysis).
Compare and contrast cellular respiration and fermentation.
Cellular respiration(Aerobic):Starts with glucose.Uses oxygen."Dumps" electrons onto oxygen to make water. Uses glycolysis, Krebs Cycle, and electron transport chain. Yields a net 36 ATP per glucose. Fermentation (Anaerobic):Starts with glucose.Uses no oxygen."Dumps" electrons onto pyruvate to make lactic acid or ethanol. Uses glycolysis. Yields a net 2 ATP per glucose.
Why is oxygen so important?!?
Oxygen Makes Complex Life Possible.
B. What are the products of each? Which photosystems are involved in each?
B. ATP and NADPH as well as O2 are the energy products of light-dependent reactions in the noncyclic pathway.
C. Which one includes photolysis? What is photolysis? What is the purpose of photolysis and what is the revolutionary byproduct? What happens to the "spent" electrons in each pathway?
C. Electrons lost from photosystem II are replaced by photolysis of water molecules - the process by which light energy breaks down a water molecule into hydrogen and oxygen. Photolysis plays an important role in photosynthesis, during which it produces energy by splitting water molecules into gaseous oxygen and hydrogen ions. After the electrons are "spent," they jump onto photosystem I.
D. What is NADPH? What is the purpose of NADPH? Which molecule has more energy, NADPH or NADP+?
D. The energy from the second ETC is used to make the coenzyme NADPH from NADP+ , electrons, and H+. NADPH is used for reductive reactions in anabolism, especially in fatty acid synthesis. NADPH is much stronger.
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