BIOL 302, Exam 4

Chloroplast:

a. Purpose: Photosynthesis b. The reason there is increased surface area is for: Absorbing more light

Endoplasmic Reticulum:

a. What is the ER usually attached to? The outside of the nucleus b. Rough ER has ribosomes on it so it can synthesis proteins c. Smooth ER is where lipids are synthesized. (Mentioned above) d. The function of the ER is to be a lattice so cells can build things

Heterotrophs capture free energy present in carbon compounds produced by other organisms.

1. Heterotrophs may metabolize carbohydrates, lipids and proteins by hydrolysis as sources of free energy. 2. Fermentation produces organic molecules, including alcohol and lactic acid, and it occurs in the absence of oxygen.

Modern eukaryotes depend on mitochondria to generate most of the cell's ATP. How many molecules of ATP can a single molecule of glucose generate?

30

Pyruvate must move from the cytosol into the mitochondria, where it oxidized to form CO2 and acetyl CoA by the pyruvate dehydrogenase complex. How many different enzymes and what total number of polypeptides, respectively, are required to perform this oxidation process in the mitochondrion?

3; 60

An antiporter in the inner mitochondrial membrane moves ATP out of the matrix and brings in

ADP

Describe the journey of a carbon dioxide molecule in photosynthesis.

CO2 is important in the light independent reactions. It is taken into the stroma, and from there goes through a series of reactions (including carbon fixation) that utilizes hydrogen from NADPH and energy from ATP to create glucose.

Describe the journey of a single carbon atom from glucose in cellular respiration

Glucose moves into the cell via a protein (glucose is hydrophilic) The chain of carbons are broken from glucose in glycolysis, this takes place in the cytoplasm of the cell. The carbons form pyruvate, a carbon rich molecule. The pyruvate moves into the mitochondrial matrix, where it undergoes change in the Krebs cycle. The pyruvate will eventually be broken down and released as CO2.

Below is a list of breakthroughs in energy metabolism in living systems. Which is the correct order in which they are thought to have evolved? in which they are thought to have evolved? I. H2O-splitting enzyme activity II. light-dependent transfer of electrons from H2S to NADPH III. the consumption of fermentable organic acids IV. oxygen-dependent ATP synthesis

III, II, I, IV

Respiration

During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced Respiration is the controlled released of energy from organic molecules in order to make ATP

Role of nucleus:

Information center, tells other parts of cell what to do

Which of the following best describes the behavior of a gated channel?

It opens more frequently in response to a given stimulus.

Eukaryotic cells maintain internal membranes that partition the cell into specialized regions.

a. Internal membranes facilitate cellular processes by minimizing competing interactions and by increasing surface area where reactions can occur. b. Membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions. c. Archaea and Bacteria generally lack internal membranes and organelles and have a cell wall.

Mitochondria:

a. Purpose: Produces energy b. Why is their folding on the cristae and why is that significant? Space on inside helps build up protons, and make as much ATP as possible. Folded to increase surface area (to make more ATP)

ETC

Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O Proton motive force

The role of NADH

Electrons from organic compounds are usually first transferred to NAD+ to form NADH (a high energy electron carrier) NADH passes the electrons to the electron transport chain O2 pulls electrons down the chain in an energy-yielding tumble The energy yielded is used to regenerate ATP

The Golgi complex is a membrane-bound structure that consists of a series of flattened membrane sacs (cisternae)

Functions of the Golgi include synthesis and packaging of materials (small molecules) for transport (in vesicles), and production of lysosomes.

Explain why red blood cells swell and burst when placed in a solution that is less concentrated than plasma.

If the solution is less concentrated than blood plasma, the water potential of the solution will be higher than that inside the red blood cells. This will cause water to rush into the cells, and since there is no stabilizing cell wall, the swelling cells will burst.

Lysosome:

a. Purposes: Has digestive enzymes, becomes phagosome to break down viruses, can dissolve mitochondria (if not working), can kill cells b. Why is it referred to as the "suicide sack"? Breaks down material

Ribosomes:

a. What are ribosomes made up of? Proteins, RNA b. Where is it synthesized? In the nucleolus c. How many subunits make up a ribosome? 2 = 1small subunit + 1large subunit d. Why does mRNA go through the middle? Translation, transferring messages to proteins

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called

active transport

Describe the journey of a single hydrogen atom from water in photosynthesis.

First, in Photosystem II where light hits a chlorophyll A molecule, electrons are captured at high energy levels. In order to replace the electrons in PSII, water is hydrolyzed into oxygen, H+, and electrons. The H+ ions (like the ones released from water) are pumped through the thylakoid membrane into the thylakoid space, creating a proton motive force. They then flow down the concentration gradient, through an ATP synthase protein, and back into the stroma. In the meantime, NADP+ gains an H+ ion, which creates NADPH, which will in turn be used in the light independent reaction to form glucose. So protons can be used to create a PMF or to create NADPH.

Describe the journey of a single hydrogen atom from glucose in cellular respiration

Glucose enters the cell and goes through a series of decomposition processes. When the hydrogen in glucose is broken off, it is stored in NADH molecules, which creates pyruvate molecules and some ATP. In the Krebs Cycle, hydrogens are again removed and stored in NADH molecules and FADH2 molecules. In the oxidative phosphorylation part of respiration, NADH and FADH2 lose hydrogen molecules to release a lot of energy, which powers the electron transport chain, and creates ATP. The released H from NADH and FADH2 become part of the cytoplasm and could become part of the PMF.

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

Glycolysis ("splitting of sugar") breaks down glucose into two molecules of pyruvate Glycolysis occurs whether or not O2 is present End result: 2 molecules of pyruvate (3 carbons each) 2 molecules of ATP (made by substrate level phosphorylation) 2 molecules of NADH

The Stages of Cellular Respiration

Glycolysis (breaks down glucose into two molecules of pyruvate) The citric acid cycle or Kreb's Cycle (completes the breakdown of glucose) Oxidative phosphorylation via the ETC (accounts for most of the ATP synthesis)

Fermentation: When No Oxygen Is Present

In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first step releasing CO2 and the second step oxidizing NADH to NAD+ In lactic acid fermentation, pyruvate is reduced to lactate as an end product, with NADH being oxidized, but with no release of CO2 If oxygen is not present, the whole Kreb's cycle and ETC shut down which means: only glycolysis can make ATP there is no way for the NADH to be reoxidized to NAD+ (it cannot give its electron to the ETC) Therefore, the role of fermentation is to allow for the oxidation of NADH so that glycolysis can continue

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?

It becomes more positive.

What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase serve as the first step in glycolysis?

It helps drive the uptake of glucose from outside the cell.

CER-Cell size

This is because the cells surface area determines its ability to transport materials in and out of the cell. With a greater surface area, waste materials are more likely to diffuse out of the cell in a given time. However, blindly increasing the size of the cell to increase surface area will not make waste removal more efficient, because the cells volume also increases (ata a faster rate than the surface area), which allows for more cellular processes to take place and waste to be created. As a result, it is not the largest cell but the cell with the largest SA:VOL that is most efficient at removing the waste it produces. That being said, even though the neurons cell body has a lower SA:VOL, the dendrites and axon on the neuron greatly increase its surface area while not increasing the volume of the cell as much. As a result, the neuron's SA:VOL may be higher than that of the liver cell, in which case the neuron would be most efficient at removing its waste products.

Golgi complex: newly made proteins are transported here and can go:

To different parts of the cell, or outside the cell

Substrate Level Phosphorylation

When ADP interacts with a high energy molecule that has a phosphate (the substrate), producing ATP. A small amount of ATP is made this way in both glycolysis and the Kreb's cycle

Why would taking DNP make someone lose weight? Why would taking DNP be dangerous?

When a person takes DNP, the proton motive force that is formed will not go through the ATPase, but rather through the DNP channels that are formed in the membrane. This means that the body produces much less ATP per gram of glucose, and tricks the body into thinking that you need to break down more glucose in order to make ATP. in other words, taking DNP causes a higher rate in metabolism, & a higher rate of breakdown of fat and sugar. Among other problems, the main problem with taking DNP for an extended period of time, is that the heat that is produced by the body when the PMF is released through the uncoupler is simply too much. Many people have reported feeling like they are on fire from the inside and many people have actually died from the results of too much DNP

It is possible to follow the movement of a single molecule or a small group of molecules. This requires the use of antibodies linked to small particles of gold, which appear as dark spots when tracked through video microscopy. What is this method called?

SPT

In which of the four compartments of a mitochondrion are the citric acid cycle proteins located?

Matrix

Vacuole Purposes:

Mostly for storage, cell growth

Which of the following cells rely exclusively on glycolysis to supply them with ATP?

anaerobically growing yeast

Passive transport does not require the input of metabolic energy; the net movement of molecules is from high concentration to low concentration

1. Passive transport plays a primary role in the import of resources and the export of wastes. 2. Membrane proteins play a role in facilitated diffusion of charged and polar molecules through a membrane. 3. External environments can be hypotonic, hypertonic or isotonic to internal environments of cells.

In the reaction centers in photosystem II, low-energy electrons are taken from water and high energy-electrons are given to plastiquinone in a process involving

charge separation

Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)?

2 ATP, 2 NADH

Which of the following has the lowest rate of diffusion across an artificial membrane that does not contain any proteins?

glucose

Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6-phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this enzyme?

ATP

The conversion of fructose 1,6-bisphosphate is catalyzed by a fructose 1,6-bisphosphatase and is one of the final steps in gluconeogenesis. Which of the following molecules is an allosteric activator of this enzyme?

ATP

Energy organelles:

i. Mitochondria for making ATP (found in all eukaryotic cells) ii. Chloroplasts make: Sugar

In humans, glycogen is a more useful food storage molecule than fat because

it can be utilized to produce ATP under anaerobic conditions, whereas fat cannot

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol?

membrane thickness

During an action potential, the membrane potential changes from __________________ to ________

negative; positive

During glycolysis, ATP is produced by

substrate-level phosphorylation

When a transporter moves two ions in the same direction across the membrane, it is considered a(n)

symporter

Cellular respiration in eukaryotes involves a series of coordinated enzyme- catalyzed reactions that harvest free energy from simple carbohydrates.

1. Glycolysis rearranges the bonds in glucose molecules, releasing free energy to form ATP from ADP and inorganic phosphate, and resulting in the production of pyruvate. 2. Pyruvate is transported from the cytoplasm to the mitochondrion, where further oxidation occurs. [See also 4.A.2] 3. In the Krebs cycle, carbon dioxide is released from organic intermediates ATP is synthesized from ADP and inorganic phosphate via substrate level phosphorylation and electrons are captured by coenzymes. 4. Electrons that are extracted in the series of Krebs cycle reactions are carried by NADH and FADH2 to the electron transport chain.

In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast?

thylakoid space

The Role of Saturated/Unsaturated Fatty acids

-As temperatures cool, membranes switch from a fluid state to a solid state due to loss of kinetic energy -The temperature at which a membrane solidifies depends on the types of lipids -Membranes rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids because the kinks prevent tight packing -Organisms will change the ratio of saturated:unsaturated fatty acids to adjust to temperature changes

The processes of endocytosis and exocytosis move large molecules from the external environment to the internal environment and vice versa, respectively.

1. In exocytosis, internal vesicles fuse with the plasma membrane to secrete large macromolecules out of the cell. 2. In endocytosis, the cell takes in macromolecules and particulate matter by forming new vesicles derived from the plasma membrane.

Electron transport is coupled to ATP synthesis in mitochondria, in chloroplasts, and in the thermophilic bacterium Methanococcus. Which of the following is likely to affect the coupling of electron transport to ATP synthesis in all of these systems?

an ADP analogue that inhibits ATP synthase

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell.

oligosaccharide

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes?

switching between lipid layers

Which of the following is required for the secretion of neurotransmitters in response to an action potential?

voltage-gated Ca2+ channels

CER-Thylakoid

ATP synthase functions by harnessing the energy of the proton motive force inside the thylakoid and using it to synthesize ATP. However, because there is a higher concentration of protons outside than inside the thylakoid, there is no proton motive force in the thylakoid to provide energy to produce ATP. Normally this would be a temporary situation because the photosystem number two would energize electrons using sunlight, and pass those electrons to the electron transport chain where the energy would be used to move protons into the thylakoid space and make the thylakoid pH lower than that of the solution, creating a proton motive force. However, the thylakoids are not being exposed to light, so they have no source of energy to harness and use to pull the protons into the thylakoid space to make a proton motive force. As a result, no proton motive force is created and before liquid cannot synthesize ATP.

Golgi Complex:

b. Purpose: takes information that is made in the ER and ships those to different parts of the cell, or outside the cell

Experimental evidence supporting the chemiosmotic hypothesis was gathered by using artificial vesicles containing a protein that can pump protons in one direction across the vesicle membrane to create a proton gradient. Which protein was used to generate the gradient in a highly controlled manner?

bacteriorhodopsin

Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential?

by opening Cl- channels

A common feature of all integral membrane proteins is that they

cannot be dissociated without disrupting the membrane's integrity

The final metabolite(s) produced by glycolysis is

pyruvate

The Role of Membrane Carbohydrates in Cell-Cell Recognition

Cells recognize each other by binding to surface molecules, often carbohydrates, on the plasma membrane Membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins

Autotrophs capture free energy from physical sources in the environment

Chemosynthetic organisms capture free energy from small inorganic molecules present in their environment, and this process can occur in the absence of oxygen.

Active transport requires free energy to move molecules from regions of low concentration to regions of high concentration

1. Active transport is a process where free energy (often provided by ATP) is used by proteins embedded in the membrane to "move" molecules and/or ions across the membrane and to establish and maintain concentration gradients. 2. Membrane proteins are necessary for active transport.

Selective permeability is a direct consequence of membrane structure, as described by the fluid mosaic model.

1. Cell membranes consist of a structural framework of phospholipid molecules, embedded proteins, cholesterol, glycoproteins and glycolipids. 2. Phospholipids give the membrane both hydrophilic and hydrophobic properties. The hydrophilic phosphate portions of the phospholipids are oriented toward the aqueous external or internal environments, while the hydrophobic fatty acid portions face each other within the interior of the membrane itself. 3. Embedded proteins can be hydrophilic, with charged and polar side groups, or hydrophobic, with nonpolar side groups. 4. Small, uncharged polar molecules and small nonpolar molecules, such as N2, freely pass across the membrane. Hydrophilic substances such as large polar molecules and ions move across the membrane through embedded channel and transport proteins. Water moves across membranes and through channel proteins called aquaporins.

The light-dependent reactions of photosynthesis in eukaryotes involve a series of coordinated reaction pathways that capture free energy present in light to yield ATP and NADPH, which power the production of organic molecules.

1. During photosynthesis, chlorophylls absorb free energy from light, boosting electrons to a higher energy level in Photosystems I and II. 2. Photosystems I and II are embedded in the internal membranes of chloroplasts (thylakoids) and are connected by the transfer of higher free energy electrons through an electron transport chain (ETC) 3. When electrons are transferred between molecules in a sequence of reactions as they pass through the ETC, an electrochemical gradient of hydrogen ions (protons) across the thykaloid membrane is established. 4. The formation of the proton gradient is a separate process, but it is linked to the synthesis of ATP from ADP and inorganic phosphate via ATP synthase. 5. The energy captured in the light reactions as ATP and NADPH powers the production of carbohydrates from carbon dioxide in the Calvin cycle, which occurs in the stroma of the chloroplast.

The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes.

1. Electron transport chain reactions occur in chloroplasts (photosynthesis), mitochondria (cellular respiration) and prokaryotic plasma membranes. 2. In cellular respiration, electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen. In photosynthesis, the terminal electron acceptor is NADP+. 3. The passage of electrons is accompanied by the formation of a proton gradient across the inner mitochondrial membrane or the thylakoid membrane of chloroplasts, with the membrane(s) separating a region of high proton concentration from a region of low proton concentration. In prokaryotes, the passage of electrons is accompanied by the outward movement of protons across the plasma membrane. 4. The flow of protons back through membrane-bound ATP synthase by chemiosmosis generates ATP from ADP and inorganic phosphate. 5. In cellular respiration, decoupling oxidative phosphorylation from electron transport is involved in thermoregulation

In non-cyclic photophosphorylation, how many electrons are required to generate one glucose molecule

48

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion?

Cl-

Mitochondria

Mitochondria have a double membrane that allows compartmentalization within the mitochondria and is important to its function. The outer membrane is smooth, but the inner membrane is highly convoluted, forming folds called cristae. 3. Cristae contain enzymes important to ATP production; cristae also increase the surface area for ATP production.

Stage 1 of oxidative phosphorylation requires the movement of electrons along the electron-transport chain coupled to the pumping of protons into the mitochondrial intermembrane space. What is the final result of these electron transfers?

O2 is reduced to H2O.

Describe the function of the oxygen molecules in cellular respiration

Oxygen molecules are used in the oxidative phosphorylation part of respiration. When NADH and FADH2 release the hydrogen and give up electrons to the electron transport chain, oxygen will be the final electron acceptor on the ETC. When it binds the electrons, it also binds with hydrogen ions, creating H20- a respiration by product.

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity?

Produce lipids with hydrocarbon tails that are shorter and have more double bonds.

Rough ER

Rough endoplasmic reticulum functions to compartmentalize the cell, serves as mechanical support, provides site-specific protein synthesis with membrane-bound ribosomes and plays a role in intracellular transport

ER

Rough has little ribosomes on it ii. Ribosomes function: Produce proteins iii. Smooth ER responsible for making lipids, and breaking down toxins

Describe the journey of a single oxygen atom from water in photosynthesis.

See above for the hydrolysis of water. Since oxygen is highly reactive, it bonds with the oxygen of another oxidized oxygen molecule from water to form O2. Then, it is released from the cell through the stroma as a by product of photosynthesis.

The Kreb's Cycle: When Oxygen is Present

The Kreb's cycle , also called the citric acid cycle, completes the breakdown of pyruvate to CO2 Each turn of the cycle oxidizes one pyruvate, generating: 1 ATP (by substrate level phosphorylation) NADH 1 FADH2 (a slightly lower energy molecule than NADH) Electrons are transferred from NADH or FADH2 to the electron transport chain

Which of the following statements about the carbohydrate coating of the cell surface is false?

The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain.

The Na+-K+ ATPase protein is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the protein hydrolyzes ATP?

The protein is phosphorylated.

Thermoregulation by Uncoupling

There is a protein in the inner mitochondrial membrane that uncouples the process of proton motive force creation and ATP production the hydrogen ions in the inter-membrane space flow back into the matrix of the mitochondrion via this protein, thus bypassing the ATP synthase complex. The energy released by the flow is not coupled to ATP production and released as heat.

Pyruvate is an important metabolic intermediate that can be converted into several other compounds, depending on which enzyme is catalyzing the reaction. Which of the following cannot be produced from pyruvate in a single enzyme-catalyzed reaction?

citrate

The direction of passive transport across a membrane is determined by the __________________ for an uncharged molecule and __________________ for a charged molecule.

concentration gradient; electrochemical gradient.

Which component of the electron-transport chain is required to combine the pair of electrons with molecular oxygen in mitochondria?

cytochrome c oxidase

Lysosomes break

down material when it's not used

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that ________________.

energy can be extracted in usable amounts

On a diet consisting of nothing but protein, which of the following is the most likely outcome?

excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet

In photosynthetic cyanobacteria that grow in long chains, some cells differentiate into heterocysts that specialize in nitrogen fixation which requires a microenvironment with low oxygen. Heterocysts do not make glucose, but instead exchange nutrients with their neighbors. Which of the following components of the electron transport chain is able to be degraded in heterocysts?

photosystem II

The most common lipids in most cell membranes are the

phosphatidylcholine

Transporters, in contrast to channels, work by

specific binding to solutes

Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell?

spectrin

Vacuole is important in

storage (especially for plant cells)

The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use?

stress-gated