Exam #2 Review (Chapter 6, 7, 44, & 8) (CA 4&5) (DG 4,5,&6) (Q4)

If an individual is dehydrated, what molecule(s) is reabsorbed from the filtrate as it moves through the collecting duct in the renal cortex? and the collecting duct in the renal medulla? What is one major solute molecule found in urine? Is the urine that leaves the end of the collective duct hyperosmotic, isoosomotic, or hypoosmotic relative to the interstitial fluid at the end of the collective duct? Is the urine hyperosmotic, isoosomotic, or hypoosmotic relative to blood?

(Water) (Water and urea) Urea Isoosmotic Hyperosmotic

If an individual needs to rid the body of excess water, what molecule(s) is reabsorbed from the collecting duct in the renal cortex? and the collecting duct in the renal medulla ? Is the urine that leaves the collective duct hyperosmotic, isoosomotic, or hypoosmotic relative to the blood?

(no molecules) (NaCl and Urea) Generally hypoosmotic

What is osmosis?

- Osmosis is the movement of water molecules across a selectively permeable membrane.

How do most ions move through solutions?. What key functional group plays an important role in the "selectivity" of this ion channel?

- Surrounded by water molecules - A carbonyl group

Cite three functions of peroxisomes in liver cells? Are peroxisomes part of the endomembrane system of the cell?

-1. Breakdown of fatty acids into smaller molecules that can enter the mitochondria as fuel for cellular respiration; 2. Detoxification of alcohol and other harmful compounds in liver cells; 3. Conversion of H2O2 (which is toxic) into water (which is non toxic) -No

How many water molecules can the aquaporin channel accommodate at one time? What biologically relevant ion does the aquaporin channel exclude?

-10 -H3O+

What is the name of the molecule that attaches Integrin to the microfilaments located in the cytoplasm? What is the purpose of this type of signaling?

-Accessory protein, also called a peripheral protein. All of these molecules are involved in mechanical signaling pathways. -To relay mechanical information from the outside of the cell to the inside of the cell.

Cite two symptoms associated with Early Onset Pompe disease. How is this disease treated? Why do you think it was difficult to develop a drug to treat this disease?

-Enlarged heart, weak muscles. -Through enzyme replacement therapy. -The drug has to contain a specific delivery system to the lysosome. It has to be inactive within the general circulation and active within the lysosome. The drug also needs to be able to cross the lysosomal membrane.

What are the two types of water? Which type of water is transported by osmosis? In what direction does water move by osmosis?

-Free water and bound water (H-bonded to hydrophilic parts of solute molecules). -Free water -Water moves from an area of higher to lower free water concentrations or from an area of lower to higher solute concentration.

What is unique about the environment within a lysosome? What is autophagy? Why is this process important in cells?

-It is very acidic and contains many hydrolytic enzymes. -The process where a lysosome fuses with a "double-membrane" vesicle containing damaged organelles. Once fused, the lysosome releases its hydrolytic enzymes, which function to degrade the damaged organelles and the "inner" membrane of the vesicle. The monomers will be released from the vesicle into the cytosol where they will be used to make new macromolecules. -By recycling monomers, the cell does not have to synthesize new ones from scratch (which is very metabolically expensive).

According to the endosymbiont theory, what two organelles may have evolved from prokaryotic species? Cite two pieces of evidence that support this theory.

-Mitochondria and chloroplasts. -1. Both the mitochondria and chloroplasts have double membranes like the ancestral prokaryotes. Most other organelles within the cell have a single membrane. 2. Mitochondria and chloroplast contain their own DNA and ribosomes, and mitochondria and chloroplasts synthesize proteins that function within these organelles.

What is a basic contracting unit of a muscle? Compared to a typical epithelial cell, what is unique about a single muscle fibril (cell)?

-Sarcomere -The single muscle fiber has a tube-like shape and it is composed mostly of myofibrils. It also contains many nuclei.

How much blood flows through the human kidney each day? How much of this volume is filtered through the glomerulus? How much of the filtrate is voided as urine?

1,600 L 180 L 1.5 L

Cite two mechanisms that take place within the active site of an enzyme that function to lower the activation energy of a reaction?

1. Active site provides a template for substrate orientation 2. Active site stresses substrates towards their transition state by stretching and bending critical chemical bonds that must be broken during the reaction 3. Active site provides a favorable micro environment for the reaction (e.g. active site may be more acidic than the neutral cell) 4. Active site can even participate directly in the catalytic reaction by forming brief covalent bonds with the substrate

What are the three transport proteins depicted within this picture?

1. SGLT2 (Sodium glucose cotransporter protein 2. Na+/K+ pump 3. Glut 2

What are three functions of the enzymes that are attached to the SER?

1. Synthesis of lipids (oils, new membrane phospholipids, and steroids); 2. Carbohydrate metabolism; 3. Detoxification of drugs, poison, alcohol, etc.

How many types of aquaporins are found in humans?

11

What is the difference between a cortical nephron and a juxtamedullary nephron? Which type of nephron is more common in human kidneys?

A cortical nephron is present mostly in the cortex, while a juxtamedullary nephron crosses the cortex, outer, and inner medulla. Cortical

In general, what is the cause of Lysosomal Storage diseases?

A genetic disease where one of the hydrolytic enzymes within the lysosome is not made or does not function.

What is free energy and how is it measured? What does this value tell you about this reaction? When this reaction is completed, which two molecules are at equilibrium? When a molecule is at equilibrium is it more or less reactive?

A livings system's free energy is the energy that can do work under cellular conditions. A change in fee energy (DG) is measured by subtracting the free energy of the products (Gfinal) from the free energy of the reactants (Ginitial). When glucose and O2 are converted to CO2 and H2O, the DG of the reaction is -686 kcal/mol. The negative value indicates that the reaction is a spontaneous energy releasing (exergonic) reaction. CO2 and H2O Less reactive

What is the signal transduction mechanism within a transport epithelial cell that enables ADH to exert it effect on the collective duct?

ADH binds to its receptor on the plasma membrane of transport epithelial cells. This binding activates the G protein, which in turn activates the membrane protein, adenylyl cyclase, which functions to synthesize cAMP from ATP. cAMP is a secondary messenger that functions to activate protein kinase A. Activated protein kinase A functions to phosphorylate molecules that are critical for the movement (via exocytosis) of aquaporin water channels to the plasma membrane of the collecting duct. Once in the membrane, water molecules can move much more quickly through the transport epithelium.

Why does the hydrolysis of ATP generate energy? In general, what type of cellular work requires energy? How does the addition of a phosphate group affect the molecule?

ATP is a molecule with a large amount of potential energy. This is because the arrangement of the three phosphate groups places negatively charged oxygen atoms right next to each other. This arrangement of atoms makes ATP very unstable and thus very reactive. Mechanical, transport, and chemical work. More specifically, the hydrolysis of ATP is used to transfer a phosphate group to another molecule. The addition of the phosphate group to the molecule makes the molecule less stable and more reactive.

What part of an enzyme binds its substrate? What types of chemical bonds help hold the substrate to the enzyme? What is "induced fit" and how does it alter the catalytic activity of an enzyme?

Active Site Weak chemical bonds such as hydrogen bonds, ionic bonds, and hydrophobic interactions When the substrate forms weak bonds with R groups of AAs in the active site, a slight change in the conformation of the enzyme will occur allowing the substrate to bind more tightly to the active site. The interactions between the substrate the key AAs in the active site will increase the catalytic ability of the enzyme.

Why does life require active transport?

Active transport allows cells to maintain internal concentrations of small molecules that differ from concentrations in the environment. This compartmentalization also occurs within the organelles of cells. These different environments are critical for cell function. For instance oxidative phosphorylation (a process the generates ATP) depends on different chemical environments on either side of the inner wall of the mitochondria.

What is active transport?

Active transport is the movement of molecules across membranes against their concentration gradient. Active transport requires energy and uses carrier proteins.

What is a Low density Lipoprotein (LDL)?

An LDL is a chylomicron that transports cholesterol within the blood stream. It contains a core of cholesteryl ester molecules (very hydrophobic) that is surrounded by phospholipids, unesterfied cholesterol, and proteins.

What is the definition of an enzyme? In general, how do enzymes alter metabolic reactions? Increase reaction rates. What is the activation energy (EA) of a reaction? How does an enzyme alter the EA of a reaction? Decreases the EA Do enzymes affect the DG of a metabolic reaction?

An enzyme is a macromolecule that acts as a catalyst, which speeds up reactions without being consumer by the reaction The amount of energy that reactants must absorb before a chemical reaction will start. No - Enzymes only affect the EA

What is the difference between an osmoregulator and an osmoconformer?

An osmoconformer has an internal osmolarity that is isoosmotic with the surrounding environment, while an osmoregulator has an internal osmolarity that is independent of the surrounding environment.

How does the plasma membrane of animal cells stays fluid at low temperatures?

Animal cells have cholesterol molecules embedded within the hydrophobic part of the membrane. These molecules prevent the hydrocarbon tails from packing close together and solidifying at low temperatures. Animals that live in extremely cold environments (e.g. artic chard) also have both saturated and unsaturated fatty acid in their phospholipids. The unsaturated fatty acids prevent the phospholipids from packing close together and solidifying at low temperature.

What is ADH? Where is it made and where is it stored within the body? What type of signal triggers the release of ADH? What is the name and location of the cell that monitors this signal? When ADH is released where does it act in the body? What is its function in this target tissue? Can ADH alone help an individual overcome dehydration?

Antidiuretic Hormone Made in the hypothalamus and stored in the posterior pituitary. Blood osmolarity > 300 mOsm/L. Osmoreceptor cells in the hypothalamus Collecting duct and distal tubule of the nephron. Increases the reabsorption of water No an individual also needs to drink water. The osmoreceptors in the hypothalamus will trigger "thirst" which stimulates the ingestions of water and also helps bring blood osmolarity back to around 300 mOsm/L

What integral protein helps speed up osmosis?

Aquaporin water channel.

What ion is stored within the lumen of the SER?

Ca2+

Know the steps involved in one cycle (crank) of the Sodium-Potassium pump.

Cells often need to create concentration gradients across membranes. The concentration of a molecule is much higher on one side of the membrane than the other when a concentration gradient exists. In order to create or maintain a concentration gradient, individual molecules must be moved from an area of low concentration to an area of high concentration. This cannot occur through passive diffusion, in fact diffusion will cause the gradient to break down. Only active transport, which requires both specialized transport molecules and the expenditure of energy can drive molecules up a concentration gradient. The sodium potassium pump is an important and well understood example of active transport.

What are the major components of blood? During filtration, which components are pushed through the semipermeable membrane of the glomerulus?

Cells, Proteins, Large Molecules, Water and small solutes such as salts, sugars, AA, buffers (HCO3-) and nitrogenous waste (urea).

What key biological process occurs within mitochondria?

Cellular respiration

What two forces are important for maintaining the electrochemical gradient of a cell?

Chemical force, an ion's concentration gradient, and electrical force, the effect of membrane potential (+ or -) on the ions movement.

What are cofactors of enzymes? Cite an example of an inorganic cofactor? Cite an example of common organic cofactors? What is another name for an organic co-factor?

Cofactors are non-protein molecules that some enzymes require for catalytic activity. The enzyme, Glucose 6 - phosphatase, requires Mg2+ as a cofactor. The enzyme dehydrogenase requires the co-factor NAD+ (an electron carrier). This organic molecule is derived from the vitamin niacin. A coenzyme.

The extracellular matrix (ECM) surrounds cells. Cite an example of two proteins found in the extracellular matrix.

Collagen and proteins found in the proteoglycan complex (this later substance contains mostly carbohydrates and ~5% protein).

When transmembrane proteins move through the endomembrane system, where is the carbohydrate component located (facing inward or facing outward?

Facing inside the lumen of the ER and Golgi, and facing inside the transport vesicles.

What type of membrane channel did Dr. Roderick MacKinnon identify, and what difficult technique did he have to learn in order to determine the structure of this channel?

Dr. Mackinnon discovered potassium ion channels. He used X-ray crystallography to determine the structure of these channels.

There are many (~200) types of cells in the body and each type has a unique function. Similarly each cell type has a unique cell membrane. How do cell membranes differ between the various cell types?

Each membrane has a unique set of proteins that reflects the unique functions of each membrane.

What is a simple definition of energy? What are the two major types of energy? How do these two types of energy differ? What type of energy is heat? What type of energy is light? What type of energy is chemical energy?

Energy is the capacity to cause change. Kinetic Energy and Potential Energy Kinetic energy is energy of motion. The kinetic energy of an object is the energy it possesses because of its motion. Moving mater can preform work by imparting motion to other objects. Potential energy is the energy that is the capacity of the matter to cause change as a consequence of its location or arrangement. Kinetic Potential

When do enzymes become saturated in a metabolic reaction? If you added more reactants, would the reaction rate increase when an enzyme is saturated? Why or why not?

Enzymes become saturated when all the active sites are filled with substrates. No Once an enzyme is saturated, the only way to increase the reaction rate is to increase the amount of enzyme.

Why are the processes of excretion and osmoregulation structurally and functionally linked?

Excretion and osmoregulation are structurally and functionally linked because most metabolic waste must be dissolved in water to be excreted from the body via the kidney.

What is the difference between an exergonic and endergonic reaction in metabolism? What is the significance of the energy that is released during an exergonic reaction?

Exergonic reactions occur spontaneously and release energy. Endergonic reactions are not spontaneous and must absorb energy from the surrounding in order to proceed. The energy released in an exergonic reaction is equal to the energy required in the reverse (endergonic) reaction.

What transport mechanism functions to move glucose across the basolateral membrane of an epithelial cell?

Facilitated diffusion via the GLUT transport proteins.

Which type of fiber is larger? Intermediate filaments plasma membrane?

Fibronectin

What are the four key functions of the excretory system?

Filtration, reabsorption, secretion, excretion.

What is the function of the enzyme, GAA Breaks 1,6 glycosidic bonds in glycogen and how is this enzyme linked to Pompe disease?

GAA is necessary for the complete degradation of glycogen. Without the enzyme the lysosomes become grossly enlarged with glycogen. The enlarge lysosomes will interfere with normal muscle cell function.

A yellow perch fish is an example of an osmoregulator. If this fish lives in a habitat with an osmolarity of ~7 mOsm/L and its blood osmolarity is ~320 mOsm/L, will it tend to gain or lose water?

Gain. How do yellow perch maintain a relatively constant blood osmolarity while living in a very hypoosmotic environement? A yellow perch will generate large volumes of very dilute urine. It may also actively uptake salts ions via its gills.

Which type of cell junction contains pores that allow molecules and ions to move freely between adjacent cells?

Gap junctions

Normally, where does glucose go after it leaves the basal laminar side of the cell via the GLUT proteins?

Glucose enters the blood stream via the peritubular capillaries.

What two types of macromolecules are modified as they move through the cisterna of the Golgi Apparatus?

Glycoproteins and phospholipids

What molecules/ions are important in maintaining the pH of body fluids? What is the osmolarity of the filtrate at the end of the proximal tubule? Has the volume of the filtrate increased, decreased, or stayed the same as it passed through the proximal tubule?

HCO3- (blood), H+ and NH3 (urine) 300 mOsm/L Decreased

Peroxisomes are small sphere like structures that contain a crystalline core made up of many different enzymes. In general, what occurs during most of the reactions that are catalyzed by the peroxisome enzymes?

Hydrogen atoms from a variety of substrates are transferred to O2, which generates H2O2, a toxic byproduct.

What type of bond holds the phospholipid membranes together?

Hydrophobic interactions

What force moves these molecules across the membrane? Is the filtrate in the Bowman's capsule hyperosmotic, isoosmotic, or hypoosmotic to the blood within the glomerulus?

Hydrostatic pressure (Blood pressure). sosmotic

How does a human obtain most of his daily intake of water? How does he lose most of his daily intake of water?

Ingestion of liquids Through urine production

Molecules can act as reversible and irreversible inhibitors when they bind to enzymes. What type of chemical bond will irreversibly inhibit an enzyme? What type of chemical bonds will reversibly inhibit an enzyme? In terms of reversible inhibition, what is the difference between a competitive and a noncompetitive enzyme inhibitor?

Inhibitors that bind covalently to the enzyme will irreversibly block enzyme activity. Inhibitors that bind to an enzyme via weak bonds or interactions (hydrogen bonds, ionic bonds or hydrophobic interactions). Competitive inhibitors bind to the active site of an enzyme and block the substrate from binding. Noncompetitive inhibitors bind to an allosteric site (site other than the active site) on the enzyme. This binding alters the shape of the active site and decreases the enzyme's ability to bind its substrate.

What are the two major types of membrane proteins?

Integral proteins (e.g. Integrins) and peripheral proteins (e.g. associated proteins)

What is the cause of familial hypercholesterolemia?

LDL receptor proteins are defective or missing in an individual. These receptors are critical for the movement of LDL into the cell via receptor-mediated endocytosis. When cells do not take up LDLs, they remain in the blood and can contribute to the build up of lipid droplets in the blood.

In general having membrane bound organelles allows eukaryotic cells to have several different local environments within the cell. Cite two organelles with dramatically different environments.

Lysosomes have a very acidic environment (pH 4-5) that is useful because this type of organelles functions to digest damaged organelles and recycle monomers. In contrast, the pH of the Endoplasmic Reticulum is neutral (pH 7.1).

What two types of vertebrates have juxtamedullary nephrons? What is an advantage of having a juxtamedullary nephron?

Mammals and birds Only this type of nephron can produce concentrated (hyperosmotic) urine, a key adaption for water conservation in mammals.

Why is fluidity important for membranes?

Membranes must be fluid to function (but not too fluid). Enzymatic proteins in the membrane are inactive when the membrane solidifies. Some of these enzymes also need to move laterally to function.

What is the definition of metabolism?

Metabolism is defined as all the catabolic and anabolic chemical reactions that occur with an organism - the totality of an organism's chemical reactions.

What type of cytoskeletal fiber is involved in the contraction of a muscle? What type of motor protein is involved in this movement?

Microfilament Myosine

What type of cytoskeletal fiber is involved in the movement of secretory vesicles within the endomembrane system of the cell? What is the name of the motor protein involved in this movement?

Microtubule (tubulin polymer) Dyneins

What cytoskeletal fiber serves as tracks that help move hCG containing vesicles out of placental cells?

Microtubules

DNA is usually associated with the nucleus of a cell. Cite two other organelles that also contain DNA? .

Mitochondria and Chloroplast

Ammonia (NH3) is a toxic metabolic waste product. How is NH3 generated in cells? Why is it toxic?

NH3 is a waste product of protein and nucleic acid metabolism or breakdown. NH3 is a weak base and it will pick up H+ ions when forming the ammonium ion (NH4+). This loss of H+ ions can change the pH of a cell and disrupt metabolic, cellular, and physiological processes within the body. What is excretion? Process that rids the body of nitrogenous metabolites and other waste products.

Which one of these transport proteins functions to establishes the electrochemical gradient of the cell?

Na+/K+ pump.

What ionic compound is reabsorbed from the filtrate as it moves through the ascending limb of the Loop of Henle? What two transport mechanisms are involved in the movement of this molecule across the transport epithelium? Why does water not move out of this part of the nephron? What is the osmolarity of the filtrate at the top of the ascending limb of the loop of Henle?

NaCl Passive transport in the thin part of the limb, Active transport in the thick part of the limb. This part of the nephron is impermeable to water. 100 mOsm/L (hypoosmotic to blood)

What molecules/ions are reabsorbed from the filtrate as it moves through the distal tubule? What ions are secreted into the filtrate at the distal tubule? What is the osmolarity of the filtrate within the cortex the collective duct?

NaCl, water, HCO3- H+, K+ ~300 mOsm/L

What molecules/ions are reabsorbed from the filtrate as it moves through the proximal tubule? What key molecule is not reabsorbed from the filtrate within the proximal tubule? What molecules/ions are secreted into the filtrate at the proximal tubule?

NaCl, water, nutrients (sugar AA), K+, HCO3- Urea H+, NH3, and drugs/toxins.

Are individual solute concentrations within the hemolymph of an osmoconformer always at equilibrium with the individual solute concentrations in the environment?

No If not, provide a specific example of an organism that is an osmoconformer, but uses active transport to maintain a hemolymph [ion] that differs from the [ion] in the surrounding environment. Atlantic Lobster, Homarus americanus, maintains a hemolymph [Mg2+] of <9 mM. While the [Mg2+] of seawater is much much greater (50 mM).

Would an osmoconformer thrive in a habitat where fresh water mixes frequently with seawater?

No. These organisms usually live in environments that have a relatively stable osmolarity.

What is the function of the G-protein?

Once activated, the α-subunit moves laterally within the membrane to activate the membrane protein adenylyl cyclase

What is omoregulations and why is it considered a homeostatic process?

Osmoregulation is the process by which animals regulate their solute concentrations and balance water gain and loss. It is a homeostatic process because the relative concentration of water and solutes within the body must be kept within a fairly narrow range to keep physiological processes functioning properly.

What is passive transport?

Passive transport is the movement of molecules down a concentration gradient (from high to low concentration). Molecules move by random thermal movements. The three different types are simple diffusion, osmosis, and facilitated diffusion. This process does not require energy and the molecule that are transported are moving towards equilibrium.

What is the major function of the chloroplast?

Photosynthesis

Why is osmoregulation such a costly process from an energetic perspective?

Physiological systems (e.g. nerve cells, muscle cells, etc) require solute gradients across cell and organelle membranes. However, diffusion tends to equalize solute concentrations across membranes. Thus, active transport is needed to maintain the solute gradients across membranes, and active transport requires energy (ATP).

What transport protein indirectly functions in the co-transport of sucrose? Which transport protein generates the [H+] gradient within the plant cell?

Proton Pump Sucrose

What type of nucleic acid is synthesized in the nucleolus?

Ribosomal RNA

Structurally, how does the Smooth Endoplasmic Reticulum (SER) differ from the RER?

Ribosomes are not attached to the SER.

What three cellular structures are present in both prokaryotes and eukaryotes?

Ribosomes, chromosome(s), and a plasma membrane are found in both prokaryotes and eukaryotes.

What type of molecule moves easily through the plasma membrane and what type of molecule does not?

Small nonpolar molecules such as molecular oxygen, carbon dioxide and molecules consisting of mostly hydrocarbons move through the membrane easily while polar molecules do not. Examples of polar molecules are monosaccharides, ions, AAs, and water. Large biological molecules such as proteins are way too large to cross the membrane. These large molecules are secreted from cells via exocytosis and frequently enter the cell via endocytosis.

Identify the following structures within this picture by drawing a line next to the structure and labeling the line with the correct letter designation (see below). Then, cite one major function of the structure within the cell. SER Free Ribosome Nucleolus Mitochondria

Smooth Endoplasmic Reticulum -Synthesis of Lipids -Carbohydrate Metabolism -Ca2+ Storage -Detoxification of drugs, poisons, alcohol, etc. Free Ribosome -Synthesis of proteins destined to remain in the -cytoplasm. Nucleolus -Synthesis of rRNA -Location where ribosomes are assembled within the nucleus. Mitochondria -Organelle where cellular respirations takes place -Energy production (ATP synthesis)

What is the major electrogenic pump in animal cells? Cite an example of another electrogenic pump that functions within cells (especially the mitochondria)?

Sodium-potassium pump. More + ions (3 Na+) leave the cell then enter the cell (2 K+). Proton pump.

What are substrates? What is the substrate for the enzyme sucrase? Can sucrase catalyze the hydrolysis of maltose? Why or why not?

Substrates are reactants that enzymes act on. Sucrose No. The shape of maltose is different enough that it does not fit into the active site of sucrase.

Plants use a cotransport mechanism to move sucrose into nonphotosynthetic plant cells such as ones found in the roots of a plant. What transport protein directly function in the co-transport of sucrose?

Sucrose-H+ Cotransporter

What factors or conditions are important in determining the optimal activity of an enzyme? Why is it important for an enzyme to function under optimal conditions?

Temperature, pH and the presence of specific co-factors. These optimal conditions allow the enzyme to achieve a shape where it functions at its highest rate (i.e. greatest catalytic ability).

Which of these membrane proteins moves within the membrane?

The G-Protein

The individual phospholipid molecules are "fluid" meaning that they can move within the membrane. In what direction do they usually move?

The adjacent phospholipid molecules will switch position laterally about 107 times/sec enabling them to travel about 2 μm/sec. On very rare occasions (~1 time/month) phospholipid molecules will flip vertically within the membrane.

What is the difference between the cis and trans sides of the Golgi Apparatus?

The cis side is the receiving side (vesicles fuse with Golgi membrane) and the trans side is the transport side (vesicles bud off from Golgi membrane).

The cardiovascular system of the body functions to provide cells with O2 and glucose and to remove CO2 and H2O. Why is the delivery and removal of these substances so important for cell survival?

The delivery and removal of these substances ensures that cells function in open systems where reactant are delivered and products removed. If cellular respiration occurred within a closed system, eventually all reactions would reach equilibrium and the production of ATP would stop. Cells need ATP to drive work within the cell. Without the synthesis of new ATP molecules, a cell will die

What is the function of the enzyme Carbamoyl Phosphate Synthetase I? How many different reactions are involved in the Urea cycle? How many different enzymes are involved in catalyzing reactions within the Urea cycle? Thinking "big", what can you conclude about the function of enzymes?

The enzyme function to catalyze the synthesis of carbamoyl phosphate from CO2 and NH3. 5 5 In general, enzymes catalyze specific reactions. For example the enzyme, Arginase catalyzes the conversion of Arginine to Ornithine but not Ornithine to Citrulline.

Prior to running a marathon, Jack eats and digests two large servings of pasta. How does the first law of thermodynamics apply to this scenario? How does this later scenario apply to the second law of thermodynamics?

The first law of thermodynamics states that energy can be transferred or transformed, but it cannot be created or destroyed. In this scenario, the potential energy stored in starch (pasta) is converted to ATP when starch is hydrolyzed to glucose and glucose is fully oxidized via cellular respiration. This ATP is converted to kinetic energy when Jack's muscles contract. The contraction of the muscles allows him to run. While running, Jack sweats profusely. The second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe. When ATP is generated, waste products, (CO2, H2O, and heat) are generated. Jack releases these waste products into the environment when he exhales and sweats, increasing the disorder of his surroundings.

Why does this process use so much energy?

The motor protein that attaches to the vesicle requires ATP for movement. Each step of the motor protein requires the hydrolysis of ATP.

What in unique about the structure of the nuclear membrane (nuclear envelope)?

The nuclear membrane exists as a double membrane, and it contains pores that allow proteins to easily move into the nucleus and ribosomes to easily move out of the nucleus

During reabsorption, the electrochemical gradient enables Na+ to move passively into the epithelial cell through SGLT2. However, because glucose concentration within the cell is high, glucose is actively transported into the cells through SGLT2. Where does the energy come from that enables glucose to enter the epithelial cell?

The passive flow of Na+ into the cell via the SLGT2 releases energy that is used to actively transport glucose into the cells. However, the Na+ gradient is established by the Na+/K+ pump that requires ATP. So, ATP indirectly provided the energy that drives the active transport of glucose into the cell.

A fluid mosaic model is use to describe the plasma membrane. What part of the membrane contributes to its fluidity, and what part of the membrane contributes to the mosaic component?

The phospholipids assembled in a bi-layer arrangement provide the fluidity, while the proteins that are embedded or transvers the membrane are the mosaics components. Remember, that both the phospholipids and many of the integral proteins move laterally within the plasma membrane.

The plasma membrane of a cell exhibits selective permeability. What does this mean and why is selective permeability a critical property of a cell?

The plasma membrane allows some substances to cross more easily than other substances, which enables the cell to have a unique internal environment.

What is excretion? Why is this process linked to osmoregulation?

The process by which the ammonia (NH3) and other metabolic waste products are removed from the body. It is linked to osmoregulation because the kidney performs both processes.

Pancreatic Amylase is made in pancreatic cells and is secreted into the lumen of the small intestine where it acts to digest small polysaccharides to disaccharides. Are the ribosomes that direct the synthesis of pancreatic amylase most likely found within the cytoplasm or attached to the endoplasmic reticulum (ER)? Why?

The ribosomes that synthesize pancreatic amylase are attached to the ER. Pancreatic amylase is a secreted enzyme, and its synthesis must be connected to the endomembrane system of the cell.

Which one of the four mechanisms listed in Question 1a is critical in establishing the osmotic gradient across this membrane?

The sodium/potassium pump established the concentration gradient across the membrane. The other three mechanisms work to equalize the concentration of solutes across the membrane.

What are the three most common destinations for the transport vesicles that bud off from the Golgi Apparatus?

The transport vesicles will: 1. Move to other parts of the cell or the plasma membrane; 2. Move back to the ER; 3. Back to the cis side of the Golgi Apparatus

If alcohol inhibits the release of ADH, would an individual's urine be hyperosmotic, isosmotic, or hypoosmotic relative to blood?

The urine would be hypoosmotic because without aquaporin molecules in the transport epithelium cells of the collecting duct, water would not be reabsorbed as efficiently.

Why is the membrane potential of a cell -70 millivolts?

There is an unequal distribution of ions across the membrane, more negative ions inside than outside the membrane. This difference favors the transport of cations (+) into the cell and anions (-) out of the cell.

Why are High Density Lipoproteins (HDLs) considered "good" cholesterol?

These chylomicrons can remove fat from macrophages in the walls of arteries

Why are LDLs considered the "bad cholesterol"?

They transport and deposit cholesterol into the walls of arteries which will attract macrophages and drive atherosclerosis (clogged blood vessels)

Where within the nephron is the greatest amount of energy consumed? What two solutes are most important for determining the osmolarity within the nephron?

Thick portion of the Ascending limb of the Loop of Henle because this is where a great deal of active transport take place. NaCl and urea

Why do phospholipids form a bi-layer in an aqueous environment?

This arrangement places the hydrophilic heads in contact with water, while the hydrophobic tails are in contact with each other and away from water.

Based on your understanding of SGLT2 function within the kidney, why were the researchers (and several drug companies) excited about these finding?

This data showed that the drug remoglifozin etabonate increased glucose elimination from the kidney. This implies that less glucose was reabsorbed as the filtrate passed through the proximal convoluted tubule. Less reabsorption of glucose into the blood = lower blood glucose levels.

What is the function of adenylyl cyclase?

This enzyme functions to generate cAMP from ATP.

Based on data from this and other studies, the drug company Avolynt, Inc is pursing the use of remogliflozin etabonate to treat diabetes in humans. In general, why are several different drug companies excited about the use of SGLT2 inhibitors to treat diabetes?

This is another tool that individuals that suffer from hyperglycemia might use to control their blood glucose levels. This is especially exciting because it utilizes a mechanism that does not involve insulin signaling.

How do cells manipulate solute concentrations in the extracellular fluid? Cite an example of an organism that expends over 30% of its resting metabolic rate to maintain its internal osmolarity?

Through active transport. Passive transport favors the equalization of solute and water concentrations across membranes, which would impede the functions of these physiological systems. Brine shrimp that lives in extremely salty lakes such as the Great Salt Lake in Utah.

How does a kangaroo rat obtain most of its daily intake of water? How does it lose most of its daily intake of water?

Through cellular metabolism of food. Evaporation

Tight junctions, desmosomes, and gap junctions are the three types of cell junctions that function to connect two adjacent animal cells. Which two types of cell junctions help form a strong seal between the cells?

Tight junctions and desmosomes

What is osmolarity? What is the osmolarity of human blood?

Total solute concentration expressed as moles of solute/liter of solution. How is it measured? Osmolarity is measured in milliOsmoles/liter or mOsm/L, where 1 mOsm/L = total solute concentration of 10-3 (moles/L) or M. 300 mOsm/L. What is the osmolarity of seawater? 1000 mOsm/L.

In addition to the synthesis of proteins that are secreted from the cell or embedded within a membrane, what are two other functions of the rough endoplasmic reticulum (RER)?

Two additional functions of the RER are: 1. Glycosylation of proteins, which describes the process by which sugar(s) are attached to proteins; and 2. Synthesis of phospholipids that become part of the ER membrane.

Cite two ways that prokaryotes differ from eukaryotes?

Unlike eukaryotic cells, prokaryotic cells are much smaller and they do not have a membrane bound nucleus or membrane bound organelles.

What molecule is reabsorbed from the filtrate as it moves through the descending limp of the loop of Henle? What transport mechanisms enables this molecule to cross of the transport epithelium? Why does this molecule move so quickly?

Water Osmosis Aquaporin channels are present in the descending limb of the Loop of Henle, which move water much faster than by diffusion through the plasma membrane.

Explain how you determined the direction of water movement.

Water moves via osmosis (a type of diffusion) from a hypoosmotic to a hyperosmotic solution.

Where does the energy come from to drive the movement of this molecule into the cell?

When H+ flow into the cell (e.g. down their concentration gradient), the energy that is stored across the membrane is released and this energy is used to cotransport sucrose into the cell (against its concentration gradient).

Many cells have transmembrane glycoproteins in which the carbohydrate component is located on the extracellular side of plasma membrane. Where within the endomembrane system of the cell are monosachharides added to these proteins?

Within both the ER and Golgi.

Why does Dr. Robert Stroud, believe that aquaporins are so important for normal kidney function?

Without aquaporins, urine volume would increase substantially (50 gallons/day) and an individual would be severely dehydrated.

Describe this gradient in terms of [Na+] in the lumen of the nephron relative to the [Na+] in the cell.

[Na+] concentration in the lumen is high and the [Na+] within an epithelial is low.

Which one of the following cytoskeletal elements functions to move chromosomes during mitosis and meiosis? a. Microtubules that are made up of actin proteins. b. Microtubules that are made up of tubulin proteins. c. Microfilaments that are made up of actin proteins. d. Microfilaments that are made up of tubulin proteins.

b. Microtubules that are made up of tubulin proteins.

When blood glucose levels are high, glucose passively flows into the β-cells of the pancreas. In order for this to occur: a. Glucose levels in the β-cells of the pancreas must be lower, and an ATP-driven carrier protein must be present in the plasma membrane. b. Glucose levels in the β-cells of the pancreas must be higher, and a carrier protein must be present in the plasma membrane. c. Glucose levels in the β-cells of the pancreas must be lower, and a carrier protein must be present in the plasma membrane. d. Glucose levels in the β-cells of the pancreas must be higher, and an ATP-driven carrier protein must be present in the plasma membrane.

c. Glucose levels in the β-cells of the pancreas must be lower, and a carrier protein must be present in the plasma membrane.

What is the function of cAMP within the cell?

cAMP is the "secondary messenger" molecule that functions to initiate a cascade of enzymes that ultimately stimulate glycogenolysis within a liver cell. Within muscle cells, glucose is oxidized via cellular respiration to generate ATP that is used in the "fight or flight" response.

Which one of the following associations is not correct? a. Golgi Apparatus: Modification of glycoproteins and phospholipids b. Peroxisome: Transfer of hydrogen atoms from various substrates to O2 c. Transport Vesicle: Transport of proteins and membrane lipids to the plasma membrane d. Rough Endoplasmic Reticulum: Autophagy

d. Rough Endoplasmic Reticulum: Autophagy

Explain why a phospholipid is an amphipathic molecule. Amphipathic molecules have both hydrophilic and hydrophobic regions.

he head (choline, phosphate, and glycerol) of a phospholipid is hydrophilic while the tail (hydrocarbons) is hydrophobic.

What is the function of this nucleic acid?

rRNA is found in ribosomes which function in protein synthesis (translation).