Exam Homework #2

Chapter 5 Assignment
1. What is energy? What are the three forms of energy?

Energy is the capacity to do work. There are four types of energy according to the powerpoint. They are Kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat), and chemical energy (potential energy of molecules).

2. State the First and Second Laws of Thermodynamics. Include entropy in your explanation.

The first law states that energy can neither be created nor destroyed it can only change from one type of energy to another, and the total amount of energy remains the same. The second law states that energy conversion goes from high energy forms to low energy forms. This is called disorder and entropy is a measure of disorder in a system. Essentially entropy is increasing as energy flows from high energy to low energy forms

3. What is the difference between endergonic and exergonic reactions?

In endergonic the products contain more free energy than the reactants, they do not occur spontaneously and require the input of energy. In exergonic reactions the products contain less energy than the reactants. These reactions occur spontaneously and release energy.

4. What do the following phases mean: a concentration gradient, down the concentration gradient and up or against the concentration gradient?

A concentration gradient: the number of molecules or ions in one region is different than the number in another region
Down the concentration gradient: In the absence of other forces, a substance moves from a region where it is more concentrated to one one where it’s less concentrated
Up/against the concentration gradient: movement of a substance to where it is more concentrated.

5. What is diffusion and what are factors that affect diffusion?
Diffusion is the net movement of like molecules or ions down a concentration gradient

6. List the participants in metabolic pathways and explain what their function is. Substrates-substance that enters pathways Intermediates-any substance formed between the start and finish of the pathway End products-substances left at the end of the reaction of pathway Energy carriers- ATP activates other enzymes and molecules through phosphate transfers Enzymes-speed rates of reactions Cofactors-coenzymes and metal ions that assist enzymes or pick up electron, atoms, or functional groups from one site and taxi to another

7. What are enzymes? What are four features of enzymes? How do enzymes work? Enzymes are catalytic molecules. They speed the rate at which reactions approach equilibrium. 1. Enzymes do not make anything happen that could not happen on its own. They just make it happen much faster. 2.Reactions do not alter or use up enzyme molecules 3.The same enzyme usually works for both the forward and reverse reactions. 4. Each type of enzyme recognizes and binds to only certain substrates Enzymes contain one or more pockets or clefts called active sites. Substrates bind to enzymes at the active site forming an enzyme-substrate complex. Substrate is then converted to product and the product dissociates from the enzyme.

8. Explain the induced fit model. The induced fit model is when substrate molecules are brought together. Then the substrates are oriented in ways that favor reaction. The active sites may promote acid-base reactions or may shut out water. 9. List and explain the factors that affect enzyme activity.
Temperature, pH, Salt concentration, Allosteric regulators, Coenzymes and cofactors. These things can either act as inhibitors or as activators. An increase in temperature increases molecular collisions, high temperatures disrupts bonds and destroy the shape of the active site.

10. Describe each of the membrane crossing mechanisms: simple diffusion, facilitated diffusion, active transport, and bulk transport.

simple diffusion: Flow of solutes through the interior of passive transport proteins down their concentration gradients. Passive transport proteins allow solutes to move both ways. Does not require any energy input. active transport: Net diffusion of solute is against concentration gradient. Transport protein must be activated. ATP gives up phosphate to activate protein. Binding of ATP changes protein shape and affinity for solute. facilitated diffusion: diffusion across lipid bilayer bulk transport: Exocytosis the proteins move out in bulk; Endocytosis the proteins move in as a group

11. What is osmosis? Distinguish between hypertonic, hypotonic, and isotonic.

Osmosis is the diffusion of water molecules across a selectively permeable membrane. Direction of net flow is determined by water concentration gradient. Side with the most solute molecules has the lowest water concentration. Hypertonic - having more solutes
Isotonic - having same amount
Hypotonic - having fewer solutes

BIO 110
Chapter 7 Homework
1. How are photosynthesis and respiration linked?

Photosynthesis and respiration require the opposite things. Since they compliment each other it makes it easy for each process to provide the materials the other needs through bi-product of their own process. What one emits because it doesn’t need the other takes in because it needs it and in return releases materials valuable to the other process.

2. List the pigments found in plants and indicate the pigment most important for photosynthesis.

Chlorophylls a and b, Carotenoids, Anthocyanins, and Phycobilins. Chlorophyll a is the most important pigment for photosynthesis since it is in all plants and absorbs light and is a source of electrons.

3. What is the function of the photosystem (include harvester pigment and reaction center in your explanation)? Photosystems absorb light and transfer it into energy. When the pigments absorb light they give up electrons which in turn go into electron transport systems. Most pigments in the photosystem are harvester pigments. When excited by light energy, these harvester pigments transfer energy to adjacent pigment molecules. Each transfer involves energy loss. In the reaction center energy is reduced to level that can be captured by molecule of chlorophyll a. This molecule (P700 or P680) is the reaction center of a photosystem. Reaction center accepts energy and donates electron to acceptor molecule.

4. Describe cyclic electron flow? What product is generated?

Electrons are donated by P700 in photosystem I to acceptor molecule. Then they flow through electron transport system and back to P700. Electron flow drives ATP formation. No NADPH is formed.

5. Describe noncyclic electron flow? What product is generated?

Two-step pathway for light absorption and electron excitation. Uses two photosystems: type I and type II. Produces ATP and NADPH. Involves photolysis - splitting of water.

6. Explain the chemiosmotic model of ATP formation?

When water is split during photolysis,hydrogen ions are released into thylakoid compartment. More hydrogen ions are pumped into the thylakoid compartment when the electron transport system operates. Electrical and H+ concentration gradient exists between thylakoid compartment and stroma. H+flows down gradients into stroma through ATP synthesis. Flow of ions drives formation of ATP.

7. Explain the Calvin-Benson Cycle? What are the reactants and products? Where does the Calvin-Benson Cycle take place?

Overall reactants: Carbon dioxide, ATP, NADPH. Overall products: Glucose, ADP, NADP+
Reaction pathway is cyclic and RuBP(ribulose bisphosphate) is regenerated. It can take place in the dark since it is a light independent reaction.

8. Write the equation for photosynthesis.

6CO2 + 6H2O + Energy --> C6H12O6 + 6O

BIO 110
Chapter 6 Assignment
1. Compare anaerobic pathways and aerobic pathways. Anaerobic pathways: Evolved first. Don’t require oxygen. Start with glycolysis in cytoplasm. Completed in cytoplasm. Aerobic pathways: Evolved later. Require oxygen. Start with glycolysis in cytoplasm. Completed in mitochondria. 2. What role does NAD+ and FAD play in respiration?

NAD+ and FAD accept electrons and hydrogen from intermediates during the first two stages. When reduced, they are NADH and FADH2. In the third stage, these coenzymes deliver the electrons and hydrogen to the transport system. 3. Where does glycolysis occur? What molecules are generated from glycolysis? What is the net yield from glycolysis?

Energy-requiring steps: ATP energy activates glucose and its six-carbon derivatives.
Energy-releasing steps.
The products of the first part are split into three carbon pyruvate molecules. ATP and NADH form.

4. What occurs during the preparatory reactions?

Pyruvate is oxidized into two-carbon acetyl units and carbon dioxide. NAD+is reduced.

5. What are the reactants and products of the Kreb Cycle? What molecule is being regenerated during the Kreb cycle?

The acetyl units are oxidized to carbon dioxide. NAD+ and FAD are reduced. One of the carbons from pyruvate is released in CO2. Two carbons are attached to coenzyme A and continue on to the Krebs cycle.

6. Where do the preparatory reaction and the Kreb Cycle occur?

Occur in the mitochondria.

7. What coenzymes, and how many of each, are reduced during glycolysis, the preparatory reactions and the Kreb cycle?

Energy requiring steps: 2 ATP invested
Energy releasing steps: 2 NADH formed 4 ATP formed
Net yield is 2 ATP and 2 NADH

8. Explain the chemiosmotic model of ATP formation.

Some of the energy released as electrons pass along the electron transport chain is used to pump protons (hydrogen ions) across the inner mitochondrial membrane from the matrix into the intermembrane space. The accumulation of protons is a form of potential energy that can be used to synthesize ATP. As the accumulated protons diffuse back through the transmembrane protein ATP synthase, it catalyzes the phosphorylation of ADP, forming ATP.

9. What is the final electron acceptor in aerobic respiration and how much ATP are generated by this process?

The final electron acceptor is oxygen. Per molecule of glucose, 32 ATP formed

10. List two fermentation pathways. Indicate how much ATP each generates and indicate what molecule is generated at the end of each.

Begin with glycolysis. Do not break glucose down completely to carbon dioxide and water. Yield only the 2 ATP from glycolysis. Steps that follow glycolysis serve only to regenerate NAD+

11. List the organic molecules that provide energy?

Fats, proteins, and glycogen.

12. Indicate the order of the evolution of the metabolic processes we have discussed.

When life originated, atmosphere had little oxygen. Earliest organisms used anaerobic pathways. Later, noncyclic pathway of photosynthesis increased atmospheric oxygen. Cells arose that used oxygen as final acceptor in electron transport.

13. How are aerobic respiration and photosynthesis linked?

The products of aerobic respiration are the reactants needed for photosynthesis and the products of photosynthesis are the reactants needed for aerobic respiration.