exam 1 /cell Biology chapter 1-6

In a redox reaction, when one reactant is oxidized, the other A. is reduced. B. is also oxidized. C. is hydrolyzed into a smaller molecule .D. releases chemical energy in the form of ATP .E. becomes a larger, more complex molecule.

A. is reduced.

re working on a project that involves the direct observation of DNA molecules. The microscope that would give you the best information at this time would be thefluorescent microscope.phase-contrast microscope. transmission electron microscope. light microscope.digital video microscope. transmission electron microscope.

transmission electron microscope

Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets? A. cholesterol B. palmitic acid C. triacylglycerol D. isoprene

triacylglycerol

Which fat serves as an animal's major form of energy storage? cholesterol glycerol phospholipid triglycerides

triglycerides

photoautotrophs and chemoautotrophs

two types of autotrophs

The activity of a zymogen is activated by __ _a) covalent modifications b) allosteric regulation c) association/ dissociation of subunits d) proteolytic modification e) none of the above

) proteolytic modification

According to the second law of thermodynamics

, heat energy released by an organism is _____. released into the environment and unusable

Higher free energy

-less stable -more concentrated -more ordered -greater work capacity Higher free energy Decreased entropy

Levels of Biological

Atom, Molecule, Macromolecule, Organelle ,Cell, Tissue ,Organ, Organ System, Organism

o which of the following classes of sugars does glucose belong? tetrose hexose pentose heptose

hexose

Why are biological macromolecules considered organic?

Biological macromolecules are organic because they contain carbon.

The Light Microscope

The standard light microscope (LM) is called a bright field microscope. The best bright field microscopes are capable of 1400x magnification and 200 nm resolution.Bright field microscopes only view dead, processed cells.

function of a terpene? A) cell surface receptor B) vitamin C) enzyme D) motility E) structure

vitamin

mechanical work

which involves a physical change in the position or orientation of a cell or some part of the cell. Mechanical work: the contraction of a weight lifter's muscles

first law of thermodynamics (law of conservation of energy)

. The first law of thermodynamics states that in every physical or chemical change, the total amount of energy in the universe remains constant, although the form of the energy may change. In other words, energy can be converted from one form to another but can never be created or destroyed.

Ultracentrifugation

A method where cell components are separated out using a centrifuge. Ultracentrifugation is capable of much higher speeds and hence much greater centrifugal force than conventional centrifugation.

allosteric site

A specific receptor site on some part of an enzyme molecule remote from the active site.

laws of thermodynamics

All living cells and organisms are open systems that exchange energy with their environment. The flow of energy through these living systems is governed by the laws of thermodynamics

Prions are known to cause A) sickle cell anemia .B) the common cold .C) herpes. D) mad cow disease.

D) mad cow disease.

Homeotherms/Endotherms

Internal heat is created through metabolism

noncompetitive

a _inhibitor binds to a site on the enzyme that is not the active site

plant cell walls contain which of the following in abundance a. starch b. cellulose c. glycogen d. lactose b. cellulose

b. cellulose

Which one of the following biological polymers is mismatched with its monomer? A. cellulose - amino acid B. DNA - nucleotide C. enzyme - amino acid D. chitin - monosaccharide

cellulose - amino acid

A food chain or food web can provide good information like _____.

the flow of energy in an ecosystemthe eating patterns of organisms

Hydrogen bonding is most important in stabilizing the ________ structure of many proteins. primary. Correct! secondary. quaternary. tertiary.

secondary.

The cytosol is best described as the internal contents of organelles. ) fluid within the nucleus. three-dimensional array of interconnected filaments. area of the cell not occupied by the nucleus. semifluid substance in which organelles are suspended.

semifluid substance in which organelles are suspended.

fluorescence

shows specific molecules

A microtome is used to

slice thin sections of specimens.

Starch is

starch are polysaccharides. They are the storage form of glucose. whereas starch is stored in the roots, seeds, and leaves of plants. Starch has two different forms, one unbranched (amylose) and one branched (amylopectin), whereas glycogen is a single type of a highly branched molecule.

Most energy in an ecosystem comes originally from _____.

the Sun

the electron microscopy has over the light microscopy.

Electron microscopy is capable of much greater resolution and hence much higher useful magnification.

The three domains of life are

Bacteria, Archaea, Eukarya

∆G

-change in free energy -change in free energy from the initial state to the final state of a reaction ∆G′, which describes the free energy change under specified conditions, is a measure of how far a reaction is from equilibrium. It represents how much energy will be released as the reaction moves toward equilibrium

A cell's surface area to volume ratio is important because

A cell with a smaller surface area has faster transport of molecules across the cell membrane If a cell has too large a surface area to volume ratio, the plasma membrane is not sufficient to deal with the increased amount of cytoplasm. Cells are limited in size by their surface area to volume ratio. That is, their plasma membrane (surface area) must be large enough to import nutrients and excrete wastes for the entire cytoplasm (volume) of the cell. As cells get larger, their surface area to volume ratio increases, which is why cells are very small.

endergonic

A chemical reaction that requires the input of energy in order to proceed. (energy-requiring)

Closed systems

A closed system cannot exchange energy with its surroundings. ... The first law of thermodynamics states that the total amount of energy in the universe i -the total amount of energy in an organism

Which of the following can only be viewed by electron microscopy?frog eggs DNA mitochondria prokaryotes nuclei

DNA

The central dogma of molecular biology states that

DNA -> RNA -> Protein DNA is used to make RNA, and RNA is used to make protein

A cell biologist wishes to visualize the ribosomes of a cell.

Electron microscopy, preferably transmission electron microscopy, should be used.

________ is the partial measure of the internal energy of a system, also known as the heat content.

EnthalpyAmino Acids

Which of the following is an application of immunofluorescence microscopy? Visualization of the natural fluorescence of a specimen under UV light.Construction of three-dimensional images of structures smaller than 10 nm. Visualization of the surface structures of a specimen. Identification of specific components of the immune system. Identifying which organelle or cellular compartment contains a particular protein.

Identifying which organelle or cellular compartment contains a particular protein.

Second Law of Thermodynamics

In a closed system, usable energy is lost over time to heat, although the total amount of energy remains the same

confocal

Microscope that uses laser illumination uses a laser to view a single plane of a specimen

Specialized Light Microscopes

Phase contrast and differential interference microscopy allows us to view living cells. Fluorescence and confocal microscopy allow us to attach a glowing dye to individual molecules, allowing us to find specific substances within the cell. Digital video microscopy allows for recording and computer processing of microscopic images. Superresolution methods can see beyond what was previously thought possible for LM.يسمح لنا الفحص المجهري لتباين الطور والتداخل التفاضلي بمشاهدة الخلايا الحية. يسمح لنا الإسفار والفحص المجهري متحد البؤر بإرفاق صبغة متوهجة بالجزيئات الفردية ، مما يسمح لنا بالعثور على مواد معينة داخل الخلية. يسمح الفحص المجهري للفيديو الرقمي بتسجيل الصور المجهرية ومعالجتها بالكمبيوتر. يمكن لأساليب الحل الفائق رؤية ما هو أبعد مما كان يُعتقد سابقًا أنه ممكن لـ LM

scanning electron microscopy has over transmission electron microscopy.

Scanning electron microscopy makes it possible to visualize subcellular structures and macromolecules as if in three dimensions.

A virologist is trying to determine the three-dimensional shape of a virus.

Scanning electron microscopy should be used.

An enzyme synthesized in the laboratory is found to have little activity when compared to the enzyme extracted from cell culture. Both enzymes were examined and have identical amino acid composition. What is the best explanation for the lack of activity of the synthesized enzyme? A. The van der Waals radius was altered during laboratory synthesis. B. The synthetic enzyme was not made of amino acids. C. The synthesized enzyme was not folded correctly because molecular chaperones were not present. D. Denaturation of the synthesized enzyme was not complete. C

The synthesized enzyme was not folded correctly because molecular chaperones were not present.

Sucrose is

glucose and fructose

lower free energy

more stable, less concentrated, less ordered, less work capacity Lower free energy Increased entropy

Which type of lipid forms most of the lipid bilayer?

phospholipids

endothermic

(of a chemical reaction or compound) occurring or formed with absorption of heat ice melting

Prokaryotes have __S ribosomes with __S and __S subunits, whereas eukaryotes have __S ribosomes with __S and __S subunits. A) 100, 60, 50; 90, 60, 40 B) 80, 50, 30; 100, 60, 40 C) 70, 50, 30; 80, 60, 40 D) 70, 40, 30; 80, 50, 30 E) 80, 60, 40; 70, 50, 30

) 70, 50, 30; 80, 60, 40

Which of the following is false? A) Phospholipids are important in membrane structure.B) Serine is a molecule that may be part of a phosphoglyceride.C) Phosphatidic acid contains two fatty acids and a phosphate group.D) Sphingolipids are the predominant phospholipid in membranes.E) Phospholipids are amphipathic.

) Sphingolipids are the predominant phospholipid in membranes.

limit of resolution

-how far apart adjacent objects must be to appear as separate entities حد القرار - إلى أي مدى يجب أن تكون الكائنات المتجاورة متباعدة لتظهر ككيانات منفصلة

covalent modification of enzymes

-reversible on and off switch -addition or removal of a chemical group (phosphate, methyl, adenyl) Covalent modification regulates enzymes by adding or removing chemical groups. Common groups added or removed include phosphate, methyl, and acetyl groups.

Which of the following statements is false? All cells arise from preexisting cells. All cells have a membrane-bound nucleus. All organisms consist of one or more cells. Cells come in a wide variety of sizes and shapes. The cell is the basic unit of structure for all organisms.

. All cells have a membrane-bound nucleus

The two strands of DNA are held together by ________; thus ________. A. covalent bonds; double-stranded DNA is very stable at a range of temperatures B. ionic bonds; double-stranded DNA separates into two separate strands in water C. hydrophobic interactions; double-stranded DNA separates into two separate strands when dissolved in a hydrocarbon (hydrophobic) solvent D. hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures

. hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures

Which one of the following amino acids has a nonpolar side chain? A. glutamine B. isoleucine C. arginine D. tyrosine B

. isoleucine

Of all 20 standard amino acids, cysteine is special because _____________ A. it has the smallest side chain which allows it to be more flexible than the other amino acids. B. it has a reactive sulfur atom that can form a covalent bond with another cysteine. C. it is less flexible than the other amino acids, so it disrupts protein secondary structure .D. it is used as the first residue of proteins.

. it has a reactive sulfur atom that can form a covalent bond with another cysteine

Under the conditions of a given reaction, a positive ΔG' means A) the reaction is spontaneous .B) no energy needs to be added. C) the reaction is at equilibrium. D) work can be done .E) the reaction will not occur.

.E) the reaction will not occur.

You are working on a project that involves the direct observation of DNA molecules. The microscope that would give you the best information at this time would be the_______________light microscope. transmission electron microscope. phase-contrast microscope. digital video microscope. light microscope. fluorescent microscope.

.transmission electron microscope.

The size range for most plant and animal cells is _____________. Correct! 10-50 micrometers 1 - 5 micrometers 10 - 50 millimeters 1 - 10 nanometers

10-50 micrometers

Which of the following is not a basic need of the cell? chemical catalysts 100% efficiency molecular building blocks energy

100% efficiency

How does brightfield microscopy allow images to be visualized? 1) Electrons strike the specimen being examined. 2) Specimens are illuminated with blue light to visualize internal features of cells smaller than 100 nm. 3) Specimens are viewed under phased light to improve magnification. 4) Specimens are fixed and have bright fluorescent molecules attached to them. 5) Specimens are illuminated with white light.

5) Specimens are illuminated with white light.

feedback inhibition (negative feedback)

A metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway. Feedback inhibition: the final product of a pathway regulates an earlier step in the pathway

Which of the following is true of nanometer?- A nanometer is about the size of a common bacterial cell. - A nanometer is one millionth of a meter.- A nanometer is equivalent to 10 Angstroms. - The nanometer is the most common measurement used in measuring whole cells.- None of the above

A nanometer is equivalent to 10 Angstroms

Which of the following is true of a nanometer? The nanometer is the most common measurement used in measuring whole cells.A nanometer is equivalent to 10 Angstroms (Å).A nanometer is one millionth of a meter.A nanometer is about the size of a common bacterial cell.none of the above A nanometer is equivalent to 10 Angstroms (Å).

A nanometer is equivalent to 10 Angstroms (Å).

Electrophoresis

A process where DNA fragments are separated according to size using electrical charges Electrophoresis separates molecules based on charge differences, thereby making it possible to separate molecules that are similar in size, shape, and density.

A reaction at equilibrium has a ∆G′ = 0

A reaction at equilibrium has a ∆G′ = 0, and no useful work can be done by this reaction. Therefore, a cell with all reactions at equilibrium is a dead cell.

exergonic reaction

A spontaneous chemical reaction, in which there is a net release of free energy.

Matter and energy flow through the biosphere. The flow of matter, however, differs from the flow of energy. Which of the following statements accurately describes these differences? A) Matter flows in cycles, whereas energy flows in one direction. B) Matter does not accompany energy as it enters the biosphere, but it does flow with energy from the biosphere .C) Energy flows from chemotrophs to phototrophs, whereas matter flows from phototrophs to chemotrophs. D) Energy flows as organic molecules are reduced to inorganic molecules, but matter does not. E) Matter and energy flow sometimes in cycles and sometimes unidirectionally.

A) Matter flows in cycles, whereas energy flows in one direction

Which of the following diseases is caused by a peroxisomal defect?A) sickle-cell anemia A) Zellweger syndrome B) sickle-cell anemia C) Tay-Sachs disease D) hypertrophic cardiomyopathy E) I-cell disease

A) Zellweger syndrome

Which of the following would be attributed to a peroxisomal dysfunction? A) accumulation of very long chain fatty acids B) accumulation of glucocerebroside C) accumulation of ganglioside GM2 D) accumulation of complex sugars E) accumulation of N-acetylglucosamine

A) accumulation of very long chain fatty acids

Fireflies have the ability to convert the energy in ATP to light. Which of the following types of work is performed by the firefly?A) bioluminescent B) heat C) concentration D) electrical E) mechanical A) bioluminescent

A) bioluminescent

The extracellular matrix outside the plasma membrane of animal cells is typically composed of A) collagen and proteoglycans. ) lipids. C) cellulose.D) peptidoglycan.E) collagen, proteoglycans, lipids, and peptidoglycan. collagen and proteoglycans

A) collagen and proteoglycans.

Another name for an oxidizing agent is a(n) A) electron acceptor. B) electron donor. C) reductant. D) electropositive metal. E) hydride transfer reagent. A) electron acceptor.

A) electron acceptor.

Which of the following processes would be most likely to occur in the Golgi complex? A) glycosylation of proteins B) synthesis of steroids C) detoxification of drugs D) production and packaging of lipids E) synthesis of DNA

A) glycosylation of proteins (glycosylation of proteins is completed there, and production and packaging of seretory proteins NOT lipids!)

f the surface area of a cell increases by a factor of 100, the volume of that cell will A) increase by a factor of 1000. B) decrease by a factor of 100. C) increase by a factor of 100. D) remain the same. E) increase by a factor of 10.

A) increase by a factor of 1000.

Which of the following is a eukaryotic characteristic? A) membrane-bounded nucleus B) cell fission C) 70S ribosomes D) little processing of RNA E) none of the above a(membrane-bound nucleus)

A) membrane-bounded nucleus a(membrane-bound nucleus)

Which of the following is least likely to be part of a cell membrane?A) proteoglycans B) phospholipids C) transport proteins D) enzymes E) glycoproteins a(proteoglycans occour in the extracellulär matrix, between cells)

A) proteoglycans a(proteoglycans occour in the extracellulär matrix, between cells)

Membrane proteins may function in A) receiving extracellular signals. B) information storage. C) protein manufacture. D) amphipathic modification. E) temperature control.

A) receiving extracellular signals.

Which of the following is not believed to be a virus or to be caused by a virus? A) scrapie B) AIDS C) TMV D) Epstein-Barr E) T 4 phage a(BSE by sheep and goats)

A) scrapie a(BSE by sheep and goats)

The statement, "The total amount of energy in the universe is constant," is a tenet of A) the first law of thermodynamics .B) the second law of thermodynamics. C) thermodynamic spontaneity. D) entropy. E) enthalpy.

A) the first law of thermodynamics.

In a biochemical reaction, reactants may be converted into products. The extent to which this occurs spontaneously is expressed as which of the following? A) ΔG B) Keq C) ΔS D) temperatureE) TΔS

A) ΔG

scientist is examining motile protist. He wishes to determine their direction of movement. Which of the following microscopic techniques is least likely to be used to view these cells? A. electron microscopy B. light microscopy C. fluorescence microscopy D. phase-contrast microscopy

A. electron microscopy

Which of the following is smallest? A. protein B. ribosome C. virus D. prokaryote

A. protein

When NAD+ becomes NADH, it is being A. reduced and gaining chemical energy. B. reduced and releasing chemical energy. C. oxidized and gaining chemical energy .D. oxidized and releasing chemical energy.

A. reduced and gaining chemical energy.

Amino Acids

Amino acids consist of the alpha carbon, amino group, carboxyl group, a hydrogen atom, and a R group.Most amino acids have in 2 stereoisomers.

Fermentation is a process that proceeds without oxygen. Such a process can be described as ________. Anaerobic

Anaerobic

Aerobic refers to what property of chemotrophs? A) Chemotrophs remove carbon dioxide from the air. B) Chemotrophs require oxygen to produce energy. C) Chemotrophs use, but do not require oxygen.D) Fermentation releases great amounts of gas but only in chemotrophs.E) Heat losses occur in the presence of oxygen. B) Chemotrophs require oxygen to produce energy.

B) Chemotrophs require oxygen to produce energy.

In a chemical reaction, the standard free energy change (ΔG°') is calculated to be -3.67 cal/mol. What can be said of the chemical reaction? A) The reaction is at equilibrium under standard conditions. B) The reaction is spontaneous under standard conditions. C) The reaction is not spontaneous under standard conditions. D) Reactants predominate over products at equilibrium under standard conditions. E) There can be no reaction.

B) The reaction is spontaneous under standard conditions.

Bioenergetics can be simply defined a sA) a subdivision of biology. B) applied thermodynamics .C) the units in which energy is expressed .D) the application of biological principles to physics.E) holding constant the variables in the universe.

B) applied thermodynamics.

Animals that regulate their body temperature independently of the environment are called A) heterotherms. B) homeotherms. C) poikilotherms. D) biotherms. E) abiotherms.

B) homeotherms

Which of the following diseases is caused by a prion? A) polio B) mad cow disease C) infantile Refsum disease D) Zellweger syndrome E) Tay-Sachs disease b(=BSE)

B) mad cow disease

Muscle contraction is an example of which of the following types of work? A) heat B) mechanical C) bioluminescent D) electrical E) concentration

B) mechanical

Membrane proteins may function in A) protein manufacture. B) receiving extracellular signals .C) temperature control. D) information storage. E) amphipathic modification.

B) receiving extracellular signals

All of the following are used as bioluminescent tools for cell biologists except A) luciferase .B) rhodopsin. C) GFP. D) YFP. E) none of the above

B) rhodopsin.

Cell biology emerged from which of the following fields of biology? Biochemistry, Cytology, and Genetics Cytology Biochemistry Genetics

Biochemistry, Cytology, and Genetics

Peroxisomes use the enzyme catalase to

Break down hydrogen peroxide so that it does not harm the cell Peroxisomes are found in all eukaryotic cells and contain oxidative enzymes, such as catalase and oxidase. Oxidase helps in oxidation of certain molecules found in the cell such as fatty acids and amino acids. Catalase, on the other hand, decomposes hydrogen peroxide either by converting it to water or by using it to oxidize another organic compound. Peroxisomes break down organic molecules by the process of oxidation to produce hydrogen peroxide. This is then quickly converted to oxygen and water. Peroxisomes produce cholesterol and phospholipids found in brain and heart tissue. A peroxisome protein is involved in preventing one cause of kidney stones.

Which of the following is true of a lysosome? A) The lysosome may function in glycosylation. B) The lysosome functions in export packaging .C) The lysosome may mature from a late endosome .D) The contents of the lysosome originate in the smooth ER.E) all of the above

C) The lysosome may mature from a late endosome

In a chemical reaction, the standard free energy change (ΔG°') is calculated to be 3.67 cal/mol. What can be said of the chemical reaction? A) The reaction is at equilibrium under standard conditions. B) The reaction goes spontaneously to the right under standard conditions. C) The reaction is not spontaneous under standard conditions.D) Products predominate over reactants at equilibrium under standard conditions. E) There can be no reaction. C) The reaction is not spontaneous under standard conditions.

C) The reaction is not spontaneous under standard conditions.

Which of the following is a heterotroph? A) grass B) a tree C) a mushroom D) a geranium E) a cyanobacterium C) a mushroom

C) a mushroom

The methanobacteria, halobacteria, and sulfobacteria are included in which domain? A) protista B) blue-green algae C) archaea D) eubacteria E) all of the above

C) archaea

The form of energy that is available to living organisms is in the form of A) sunlight. B) radiation. C) chemical bonds .D) nuclear energy. E) heat.

C) chemical bonds.

Which process involves an increase in entropy of the system? A) freezing of ice B) any spontaneous process C) combustion of paper D) formation of raindrops E) synthesis of cellulose

C) combustion of paper

Nerve impulses travel along the neurons by the opening of channels that allow sodium ions to flow inward, followed by an outward flow of potassium ions. In order to ensure that the impulse may be produced at any time, sodium is actively transported out of the cell, and potassium is transported into the cell by the sodium/potassium pump. Which of the following types of work is performed by the sodium/potassium pump? A) mechanical B) electrical C) concentration D) synthetic E) bioluminescent C) concentration

C) concentration

Which of the following types of work involves a change in position of the cell or a cell structure? A) bioluminescentB) electricalC) mechanicalD) syntheticE) concentration C) mechanical

C) mechanical

The major structural elements of the cytoskeleton are A) the extracellular matrix and the cell wall .B) cleavage furrows and G-actin. C) microtubules, microfilaments, and intermediate filaments .D) proteoglycans and cellulose microfibrils. E) the cytoplasm and cytosol.

C) microtubules, microfilaments, and intermediate filaments.

Which of the following is an endothermic process? A) combustion reactions B) adding a strong acid directly to water C) oxidation of metals D) ice melting E) neutralization reactions of the addition of strong acid directly to a strong base

C) oxidation of metals

Kuru is a degenerative disease of the central nervous system believed to be caused by which type of agent? A) virusB) bacteriumC) prion D) viroidE) protozoan

C) prion

When the ΔG°' of a chemical reaction is positive (K'eq < 1.0) under standard conditions, A) reactants and products are at equilibrium. B) work can be done under these conditions. C) reactants predominate over products. D) the reaction is spontaneous to the right.E) the reaction is exothermic. C) reactants predominate over products.

C) reactants predominate over products.

The steady state so vital to life is possible because A) the cell cannot convert energy from one form to another. B) all cells are autotrophic. C) the cell continually takes up energy from the environment. D) all reactions are at equilibrium. E) all reactions are exothermic. C) the cell continually takes up energy from the environment.

C) the cell continually takes up energy from the environment.

Photosynthesis is an important process that A) is performed by heterotrophs. B) produces oxidized products. C) uses water and carbon dioxide as reactants. D) is performed by organisms living near deep-ocean thermal vents.E) only plants can perform.

C) uses water and carbon dioxide as reactants.

The hallmark feature of peroxisomal diseases is the presence of A) amyloid plaques. B) an abundance of myelin. C) very long chain fatty acids. D) long chain gangliosides .E) hydrolases. c(the peroxisome breaks down fatty acids)

C) very long chain fatty acids. (the peroxisome breaks down fatty acids)

The term "metabolism" refers to A. reactions involving the breakdown of complex molecules into simpler ones. B. reactions involving the breakdown of complex molecules or the exchange of atoms between similarly sized reactants. C. all the chemical reactions in the body. D. reactions involving the synthesis of complex molecules from simpler ones. E. digestive system reactions that are either catabolic or exchange reactions.

C. all the chemical reactions in the body.

In a chemical reaction where an electron is exchanged from one reactant to another, the structure that loses an electron is A. analyzed. B. catalyzed. C. oxidized. D. reduced.

C. oxidized.

Catalysts

Catalysts work by lowering the activation energy barrier. This means that more molecules can get past the activation energy barrier, and the reaction can proceed at a faster rate. Enzymes are biological catalysts which lower activation energy by bringing the reactant molecules together at the right orientation for the reaction to proceed.

A metabolic pathway A metabolic pathway Catalyzes chemical reactions L inks several chemical reactions, such that the product of one reaction becomes the reactant of the next reaction Is not required to obey the laws of chemistry and physics Is not relevant to cellular function Catalyzes chemical reactions Links several chemical reactions, such that the product of one reaction becomes the reactant of the next reaction Is not required to obey the laws of chemistry and physics Is not relevant to cellular function

Catalyzes chemical reactions Links several chemical reactions, such that the product of one reaction becomes the reactant of the next reaction Is not required to obey the laws of chemistry and physics Is not relevant to cellular function Links several chemical reactions, such that the product of one reaction becomes the reactant of the next reaction metabolic pathway is a series of chemical reactions that takes a starting molecule and modifies it, step-by-step, through a series of metabolic intermediates, eventually yielding a final product. In the example of sugar metabolism, the first metabolic pathway synthesized sugar from smaller molecules, and the other pathway broke sugar down into smaller molecules. These two opposite processes—the first requiring energy and the second producing energy—are referred to as anabolic pathways (building polymers) and catabolic pathways (breaking down polymers into their monomers), respectively. Consequently, metabolism is composed of synthesis (anabolism) and degradation (catabolism)

exothermic

Chemical Reaction in which energy is primarily given off in the form of heat releases heat (feels hot)

exergonic

Chemical reactions that release energy energy-yielding For a biological example of an exergonic reaction, consider again the oxidation of glucose to carbon dioxide and water: C6H12O6 + 6O2 S 6CO2 + 6H2O + energy An exergonic reaction has a negative ∆G′ and proceeds spontaneously in the direction written, whereas an endergonic reaction has a positive ∆G′ and requires the input of energy to proceed as written.

A ________ is an organism that requires the intake of chemical compounds such as carbohydrates, fats, and proteins. Chemotroph

Chemotroph

Which of the following statements is not true of the value ΔH? A) ΔH is the change in heat content. B) ΔH is the change in enthalpy .C) In biology, ΔH is basically the same as ΔE. D) A reaction with a positive ΔH value is exothermic. E) ΔH = ΔE + Δ(PV) D) A reaction with a positive ΔH value is exothermic

D) A reaction with a positive ΔH value is exothermic.

Which is not true of phototrophs? A) They capture light energy. B) They can be bacteria. C) They store energy as glucose. D) They never function as autotrophs. E) They provide energy for chemotrophs.

D) They never function as autotrophs.

RNA and DNA differ A) in that RNA contains ribose and DNA contains deoxyribose. B) in that RNA contains nucleosides and DNA contains nucleotides. C) in that RNA contains uracil and DNA contains thymine .D) both A and C. E) All of these are correct. D) both A and C.*

D) both A and C.*

A spontaneous reaction A) has to occur immediately. B) will never occur. C) has an overall positive free energy change. D) could occur but might take a very long time. E) is associated exclusively with homeothermic organisms. D) could occur but might take a very long time.

D) could occur but might take a very long time

Communication between animal cells is facilitated by A) tight junctions. B) adhesive junctions. C) plasmodesmata. D) gap junctions. E) both choices B and C d(gap junctions, gap = lucka)(plasmodesma in plant cells)(tight and adhesive junctions for linking cells, no communication)

D) gap junctions. d(gap junctions, gap = lucka) (plasmodesma in plant cells) (tight and adhesive junctions for linking cells, no communication)

What are the three general types of amino acids? A) α helices, β sheets, and looped segments B) covalent, noncovalent, and van der Waals forces C) positive, negative, and noncharged D) hydrophobic, polar (noncharged), polar (charged) E) acidic, basic, and neutral

D) hydrophobic, polar (noncharged), polar (charged)

Which of the following fundamental properties of life do viruses not possess? A) metabolismB) irritabilityC) ability to reproduceD) metabolism and irritabilityE) irritability and ability to reproduce metabolism and irritability

D) metabolism and irritability

Mitochondria are thought to have evolved from ancient bacteria. Which characteristics of a free-living bacteria have mitochondria lost over time?A ) an independent genome B) ribosomes C) phospholipid membranes D) motility E) ribosomes, phospholipid membranes, motility, and an independent genome motility

D) motility

Viruses are composed ofA ) DNA and protein.B) only protein.C) RNA and lipid.D) nucleic acid, protein, and sometimes lipid.E) only nucleic acid. nucleic acid, protein, and sometimes lipid

D) nucleic acid, protein, and sometimes li

Which organelle has only a single membrane around it? A) ribosome B) nucleus C) chloroplast D) peroxisome E) mitochondrion d(peroxisome: all others are surroundet by a double membrane, except ribosome which has none)

D) peroxisome d(peroxisome: all others are surroundet by a double membrane, except ribosome which has none)

The chromoplast is an organelle associated with A) ribosome production in primitive plants .B) oxidation of sugars. C) synthesis of secretory proteins. D) plant pigment storage. E) storage of chromium.

D) plant pigment storage d(chromoplasts are pigment containing plastids in plantcells that are responsibel for the characteristic coloration)

Which of the following organelles is not part of the endomembrane system? A) lysosome B) endoplasmic reticulum C) secretory vesicle D) ribosome E) Golgi apparatus

D) ribosome d(ribosomes have no membran, therfore are they not part of the endoMEMBRANE system)

The two strands of DNA are held together by ________; thus ________ .A. covalent bonds; double-stranded DNA is very stable at a range of temperatures B. ionic bonds; double-stranded DNA separates into two separate strands in water C. hydrophobic interactions; double-stranded DNA separates into two separate strands when dissolved in a hydrocarbon (hydrophobic) solvent D. hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures D

D. hydrogen bonds; double-stranded DNA separates into two separate strands at high temperatures

Melvin Calvin and his colleagues used which of the following to deduce the steps in the Calvin cycle? A. Drosophila melanogaster B. electron microscopy C. ultracentrifugation D. radioisotopes

D. radioisotopes

Which of the following can only be viewed by electron microscopy? mitochondria. frog eggs. Correct! DNA. nuclei. prokaryotes.

DNA.

Which of the following is mismatched? A. Escherichia coli - genetics B. Drosophila melanogaster - photosynthesis C. Mus musculus - immunology D. Arabidopsis thaliana - plant gene function

Drosophila melanogaster - photosynthesis

Which of the following is mismatched? A. Escherichia coli - genetics B. Drosophila melanogaster - photosynthesis C. Mus musculus - immunology D. Arabidopsis thaliana - plant gene function B

Drosophila melanogaster - photosynthesis

Which is true of heterotrophs? A) They capture light energy. B) They cannot be unicellular. C) They store energy in the form of heat. D) They can function as autotrophs in an emergency. E) They can obtain energy from consuming phototrophs.

E) They can obtain energy from consuming phototrophs.

The statement, "Energy is neither created nor destroyed," describes A) the first law of thermodynamics .B) the second law of thermodynamics. C) the law of conservation of energy. D) enthalpy. E) both choices A and C E) both choices A and C .......................................... The statement, "Energy is neither created nor destroyed," describesthe first law of thermodynamics. enthalpy.the law of conservation of energy. the second law of thermodynamics. the first law of thermodynamics; the law of conservation of energy.

E) both choices A and C A) the first law of thermodynamics the law of conservation of energy C) the law of conservation of energy. ........................... the first law of thermodynamics; the law of conservation of energy

When ΔG' = 0 in a chemical reaction, under standard conditions, A) reactants and products are at equilibrium .B) work can be done; energy is required. C) the reaction is spontaneous to the left. D) no work can be done; no energy is required. E) both choices A and D

E) both choices A and D

Which of the following organelles is not generally found in animal cells? A) food vacuole B) mitochondrion C) centriole D) endoplasmic reticulumE) central vacuole

E) central vacuole

Energy is important to life forms because A) all life forms require a continuous supply of it. B) it is required to do work. C) it is required to make specific alterations in the cell. D) both choices A and B E) choices A, B, and C

E) choices A, B, and C

Energy is important to life forms because A) all life forms require a continuous supply of it. B) it is required to do work .C) it is required to make specific alterations in the cell. D) both choices A and B E) choices A, B, and C

E) choices A, B, and C A) all life forms require a continuous supply of it. A) all life forms require a continuous supply of it. B) it is required to do work

Which of the following is included as part of the Eubacteria? A) thermacidophiles B) halobacteria C) methanogens D) sulfobacteria E) cyanobacteria

E) cyanobacteria

A(n) ________ is composed of tetrameric protofilaments.A) extracellular matrixB) microtubuleC) bacteriophageD) microfilamentE) intermediate filament

E) intermediate filament

The Electron Microscope EM

EM uses an electromagnetic field to focus a beam of electrons.EM allows 100,000x magnification, 2 nm resolution. 2 major types :Transmission electron microscopy (TEM): sends the electron beam through a thinly sliced specimen. Scanning electron microscopy (SEM): bounces an electron beam off the intact surface of a specimen.

First Law

Energy can neither be created nor be destroyed. It can change from one to another. The total energy of universe remains constant.

Entropy and Free Energy

Entropy and Free Energy Are Two Means of Assessing Thermodynamic Spontaneity

Enzymes are specific to their substrates.

Enzymes are specific to their substrates. Substrate specificity: an enzyme that catalyzes one reaction. Group specificity: an enzyme that catalyzes a small group of reactions. -have a very high substrate specificity-Some enzymes will accept a number of closely related substrates-Others accept any of an entire group of substrates sharing a common feature

Enzymes work by _____.

Enzymes work by reducing the energy of activation (lowering the Ea)

How do eukaryotes differ from prokaryotes?

Eukaryotic cells have a nucleus; prokaryotic cells do not.

Which of the following accurately describes the structure of fibrous proteins? A. Fibrous proteins usually contain a number of different domains with different structural motifs .B. Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure. C. Fibrous proteins have an extensive tertiary and quaternary structure that affects the strength and elasticity of each fiber. D. Fibrous proteins have a simple primary structure and very little secondary structure, resulting in long, thin fibers. B

Fibrous proteins are usually composed of either α helices or β sheets throughout the molecule, giving them a highly ordered, repetitive structure

In every physical or chemical change, energy cannot be created nor destroyed. This is the ________ law of thermodynamics. First

First

An immunologist wishes to determine if a lymphocyte possesses a certain surface protein.

Fluorescence microscopy is often used

What is free energy

Free energy is a measure of energy that is available to do work. The free energy of a system changes during energy transfers such as chemical reactions, and this change is referred to as ΔG or Gibbs free energy. Portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system. G.

Describe the similarities and differences between glycogen and starch.

Glycogen and starch are polysaccharides. They are the storage form of glucose. Glycogen is stored in animals in the liver and in muscle cells, whereas starch is stored in the roots, seeds, and leaves of plants. Starch has two different forms, one unbranched (amylose) and one branched (amylopectin), whereas glycogen is a single type of a highly branched molecule.

A protein is destined to be secreted from a cell. In which organelle would you expect to find the protein immediately after it is produced in the rough endoplasmic reticulum? lysosome Golgi apparatus secretory vesicle endosome

Golgi apparatus

Lysosomes are membrane-bound vesicles that arise from which of the following organelles?

Golgi apparatus

In the metabolism of a cell, why is hydrolysis used? Hydrolysis breaks down polymers. Hydrolysis is used to form linkages in DNA. Hydrolysis is used to produce proteins. Hydrolysis synthesizes new macromolecules.

Hydrolysis breaks down polymers.

proteolytic cleavage

Hydrolysis of a protein by a proteolytic enzyme, eg. trypsin, chymotrypsin Proteolytic cleavage: an enzyme (or another protein) can be activated by cutting off part of the polypeptide chain. This is common in the digestive tract. It is one way that the body helps ensure that the digestive enzymes are only active in the digestive tract rather than digesting the body itself.

What role do electrons play in dehydration synthesis and hydrolysis?

In a dehydration synthesis reaction, the hydrogen of one monomer combines with the hydroxyl group of another monomer, releasing a molecule of water. This creates an opening in the outer shells of atoms in the monomers, which can share electrons and form covalent bonds.

Second Law

In a natural thermodynamic process the sum of the entropies of the interacting thermodynamic systems increases. A spontaneous process is a process that occurs in a system without any input of energy from the surroundings. Hence a spontaneous process is also called an irreversible process. all spontaneous processes are thermodynamically irreversible. entropy of the universe is continuously increasing.

Why is a selectively permeable membrane so important to living things? A. It allows cells to attach to adjacent tissues. B. It provides a good barrier between the inside and outside of the cell .C. Proteins will avoid a selectively permeable membrane. D. The membrane may absorb several times its weight in cholesterol. B

It provides a good barrier between the inside and outside of the cell

Catalyzes hydrolytic reactions

Join molecules together

Lipids are amphipathic molecules

Lipid molecules have both hydrophobic and hydrophilic regions

The Michaelis-Menten reaction describes -Whether a chemical reaction will be spontaneous - The Michaelis-Menten reaction describes -Enzymes have an ideal pH at which they function best. This is important becaus It means that enzymes will only work at the appropriate temperature

Michaelis-Menten Equation. This is the fastest the reaction could go if there is an infinite amount of substrate available. Describes the relationship between the initial velocity of a reaction and the substrate concentration. describing the kinetics of an enzyme-catalyzed reactionmakes which of the following assumptions about the conversion of product into substrate The product is not converted to substrate to any appreciable extent.

Some researchers have hypothesized that type II diabetes mellitus is caused by a mitochondrial defect. Which of the following would be the best way for them to study mitochondrial differences in fresh tissue samples from diabetic and nondiabetic mice?A) Mitochondria could be identified and isolated from other cellular components using immunofluorescence microscopy in both tissues.B) Mitochondria are the only organelles that survive tissue homogenization, thus both tissues could be homogenized to study the mitochondria.C) Mitochondria from both tissues could be isolated from other cellular components by using proteolytic enzymes to break down other cellular structures.D) Mitochondria from both tissues could be isolated from other cellular components by fractionating tissue homogenate using differential centrifugation followed by density gradient centrifugation.E) Mitochondria can not be separated from whole cells without damaging them Mitochondria from both tissues could be isolated from other cellular components by fractionating tissue homogenate using differential centrifugation followed by density gradient centrifugation.

Mitochondria from both tissues could be isolated from other cellular components by fractionating tissue homogenate using differential centrifugation followed by density gradient centrifugation.

An enzyme that is a transferase Moves functional groups to different molecules he secondary structure of proteins most directly results from

Moves functional groups to different molecules Transferases are enzymes that catalyze the transfer of a functional group from one molecule to another. An example is acyl transferases that catalyze the transfer of acyl groups. An example is the peptidyl transferas

Concentration Work

Moving Molecules Across a Membrane Against a Concentration Gradient

Which organelle stores most of the DNA in plant and animal cells? Nucelus. Golgi complex. Mitochondria. Lysosome. Chloroplast.

Nucelus.

Chemoautotrophs

Organisms that use hydrogen sulfide or other chemicals as energy source instead of light. chemotrophs get energy by oxidizing chemical bonds in organic or inorganic molecules. Chemoautotrophs (a few bacteria) oxidize inorganic compounds such as H2S, H2 gas, or inorganic ions for energy and synthesize all their organic compounds from CO2. Chemoheterotrophs, on the other hand, ingest and use chemical compounds such as carbohydrates, fats, and proteins to provide both energy and carbon for cellular needs. All animals, protozoa, fungi, and many bacteria are chemoheterotrophs

Photoautotrophs

Organisms that use light as a source of energy to synthesize organic substances. Photoautotrophs use solar energy to produce all their necessary carbon compounds from CO2 during photosynthesis . Examples of photoautotrophs include plants, algae, cyanobacteria, and photosynthetic bacteria. Photoheterotrophs (some bacteria) harvest solar energy to power cellular activities, but they must rely on the intake of organic molecules for their carbon needs

Disulfide bond formation

Oxidation of pairs of cysteine side chains (cystine) Stabilizes protein structure In proteins, these bonds form between the thiol groups of two cysteine amino acids.

A microbiologist wishes to examine the motility of a bacterium.

Phase contrast or differential-interference-contrast would be most helpful.

Which of the following is true of plant cells? The plant cell has no cell wall. Plant cells may contain chloroplasts. Chromosomes are found only in plant cells. Plant cells are always much larger than animal cells. Only plant cells have a cell membrane.

Plant cells may contain chloroplasts.

which is an accurate description of the flow of energy? h

Producers make their own food. Consumers gain energy from producers. Decomposers break down dead matter into essential nutrients that are then reused by producers. in correct/chemotrophs, who give off energy as heat; phototrophs then capture the heat and use it as energ

A catalyst is most likely to be DNA molecule Carbohydrate Lipid Protein

Protein

Scientists believe that the first self-replicating genetic molecule was

RNA

An oxidation reaction Removes electrons from a substance and consumes energy Adds electrons to a substance and releases energy Removes electrons from a substance and releases energy Adds electrons to a substance and consumes energ

Removes electrons from a substance and consumes energy

The purpose of electrophoresis is to To allow us to alter genes and see what happens. To use radioactivity to trace a molecule's location within a cell Separate molecules based on their size and electrical charge Allow us to view small objects that cannot be seen with the eye alone.

Separate molecules based on their size and electrical charge To use radioactivity to trace a molecule's location within a cell Separate molecules based on their size and electrical

Suggest one advantage that bioinformatics has over sequencing of a genome.

Sequencing of a genome simply provides a large amount of data about the DNA present in the genome, whereas bioinformatics uses computer analysis to aid in understanding and interpreting those data in terms of gene numbers and expression.

Monosaccharides A major function of monosaccharides is

Simple sugars Molecules with the formula CnH2nOn. Classified according to the location of the carbonyl group and the number of carbon atoms in the molecule. Can exist as a chain or a ring.

How does brightfield microscopy allow images to be visualized? Specimens are illuminated with blue light to visualize internal features of cells smaller than 100 nm. Specimens are illuminated with white light. Specimens are fixed and have bright fluorescent molecules attached to them. Electrons strike the specimen being examined. Specimens are viewed under phased light to improve magnification. Specimens are illuminated with white light.

Specimens are illuminated with white light.

How does a transmission electron microscope (TEM) differ from a scanning electron microscope (SEM)?

TEM sends an electron beam through a specimen; SEM bounces an electron beam off the surface of a specimen

Our textbook defines energy as A force exerted across a distance The force that generates diffusion Something proudced by the nucleus of the cell The ability to cause specific physical and chemical changes

The ability to cause specific physical and chemical changes

The active site

The active site is the location where substrates bind to the enzyme. Each enzyme has a characteristic group of amino acids found at the active site. Many enzymes require cofactors for catalytic activity. Organic cofactors are called coenzymes; these are often made from vitamins. Inorganic cofactors (e.g., metal ions) are also common.

Which of the following best describes a metastable state? This state is composed of the difference in activation energy of a catalyzed versus an uncatalyzed reaction. The metastable state is created by the prosthetic group of the enzyme. The metastable state is formed by transient complexes with the substrate. This state changes the position of the equilibrium but not the rate. The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.

The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.

You are researching a cytoplasmic protein associated with a nerve disorder. The native form of the enzyme appears to be globular protein; however, when a sample of the purified protein is treated with a chemical that reduces disulfide bonds, the enzymatic activity decreases dramatically and multiple globular proteins can be detected in the sample. What does this tell you about the protein? A. The primary structure of the protein contains multiple cysteine residues that are hydrolyzed by the chemical reductant. B. The protein is most likely composed of α helices that are held together by disulfide bonds. C. The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds. D. The protein is most likely composed of β sheets that are held together by disulfide bonds

The protein is most likely composed of multiple polypeptide chains that are held together by disulfide bonds.

Activation Energy

The rate at which a chemical reaction occurs depends on the proportion of reactants which can get past the activation energy barrier.

Electrical Work:

The work done on a charged particle by an electric field n electrical potential or a membrane potential, is also established across the membrane

The Michaelis-Menten Michaelis-Menten

This equation describes the rate at which chemical reactions occur. Factors involved in the equation include: The substrate concentration [S] The initial velocity (v) The maximal velocity (Vmax) The Michaelis-Menten constant (Km) Vo=Vmax[S]/Km+[S] cooperative enzymes show a sigmoidal curve relationship between velocity and substrate concentration for an enzyme-catalyzedreaction

A pathologist is trying to examine the cytoplasm of a cell for changes that result from viral infection

Transmission electron microscopy will enable the pathologist to visualize the interior.

Allosteric regulation

When a protein's function at one site is affected by the binding of a regulatory molecule to a separate site. Allosteric regulation alters the conformation of the enzyme to turn it on or off. Allosteric effector: binds to and stabilizes one of the conformations. Allosteric (regulatory) site: the site where the allosteric effector binds; not the active site. Regulatory subunit: the portion of the enzyme containing the allosteric site. Cooperativity: refers to the method by which a conformation change alters affinity for the substrate.

competitive inhibitor

_inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate

Which of the following is an example of energy changing from one form to another?

a fire

The components of a nucleotide are_______________ a six-carbon sugar, an ester linkage, and a four-ringed hydrocarbon. a three-carbon alcohol with a hydroxyl group on each carbon and three fatty acids. a carboxyl group, an amine group, and a variable R group. two six-carbon sugars attached with an α(1→4) glycosidic bond. Correct! a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base.

a five-carbon sugar, a phosphate group, and a nitrogen-containing aromatic base.

Metastable state roducts that are thermodynamically stable but lack sufficient activation ener

a long-lived stable state that is less stable than the most stable (lowest energy) state •Metastable state: reactants that are thermodynamically unstable but lack sufficient activation energy. •Most molecules are in the metastable state. •The fact that molecules remain metastable without catalysts keeps them far from equilibrium and keeps us alive. The metastable state refers to the state in cells where many molecules are thermodynamically unstable, but do not have enough kinetic energy to overcome activation energy and are thus in a state that resembles stability. It plays an important role in preventing the cell from reaching equilibrium.

Fluorescence

a material absorbs light at one wavelength and then emits light at a longer wavelength bioluminescence, the production of light using ATP or chemical oxidation as an energy source, and fluorescence, the production of light following absorption of light of a shorter wavelength.

Entropy

a measure of the disorder of a system

Which of the following is a chemoheterotroph? a mushroom a tree grass a photosynthetic bacterium

a mushroom

Which of the following molecules is most likely to cross the cell membrane directly by passive diffusion? A. Na+ B. a steroid hormone (a hydrocarbon) C. fructose (a sugar) D. insulin (a polypeptide) B

a steroid hormone (a hydrocarbon)

A scientific hypothesis is __________ .a testable explanation of a natural phenomenonthe same as a theorya test in which only specific conditions are allowed to varya theory that has been confirmed a testable explanation of a natural phenomenon

a testable explanation of a natural phenomenon

Which of the following is a phototroph a tree a mushroom soil bacterium an earthworm

a tree

Which of the following is closest to a micrometer in size? the size of a ribosomethe length of a plant cellthe length of a chicken egga typical prokaryotic cellthe width of a strand of DNA a typical prokaryotic cell

a typical prokaryotic cell

during the breakdown of polymers, which of the following reactions takes place? a. hydrolysis b. dehydration c. condensation d. covalent bond a. hydrolysis

a. hydrolysis

falsifiable

able to be disproven by experimental results theory is possible to reject Describes a hypothesis that can be ruled out by data that show that the hypothesis does not explain the observation.

Which of the following would be attributed to a peroxisomal dysfunction? A) accumulation of very long chain fatty acids B) accumulation of glucocerebroside C) accumulation of complex sugars D) accumulation of ganglioside GM2 E) accumulation of N-acetylglucosamine phosphotransferase

accumulation of very long chain fatty acids

he minimum amount of energy necessary to start a chemical reaction is _____. a. enthalpy b. entropy c. activation energy d. kinetic energy

activation energy

Acetylation

addition of acetyl group Acetylation is the addition of an acetyl or ethanoyl group; usually, the group is added to a lysine. The forward reaction is driven by the strong amide bond that results.

Covalent modification ent modificationaffects the activity of an enzyme by adding or removing a chemical group .produces modifications that can sometimes be reversed .can involve the addition of phosphate groups. can activate an enzyme.all of the above all of the above

all of the above

The primary structure of a protein is important both genetically and structurally. is the linear sequence of amino acids that are linked together by peptide bonds. all of these statements are true is simply the order of amino acids from one end of the protein to another. is important for determining the secondary and tertiary structure of a protein

all of these statements are true

Complementary relationships between purines and pyrimidines allow adjacent bases in a nucleotide chain to stack tightly, stabilizing the DNA double helix. provide highly ordered, repetitive bonding to form α helices and β sheets within proteins. Correct! allow adenine to form two hydrogen bonds with thymine (or uracil) and guanine to form three hydrogen bonds with cytosine to form double-stranded nucleic acids. allow the interaction of the oppositely charged amino acids to form the tertiary structure of proteins.

allow adenine to form two hydrogen bonds with thymine (or uracil) and guanine to form three hydrogen bonds with cytosine to form double-stranded nucleic acids

dehydration synthesis

also, condensation; reaction that links monomer molecules together, releasing a molecule of water for each bond formed التوليف الجفاف أيضا ، التكثيف. تفاعل يربط جزيئات المونومر معًا ، مما يؤدي إلى إطلاق جزيء من الماء لكل رابطة تتشكل

kinase

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule. Phosphorylation is typically carried out under the control of another enzyme called a kinase

A student drops his notes, and his papers scatter. The fact that the papers scatter and do not remain neatly stacked is an illustration of the first law of thermodynamics. an increase in entropy. the second law of thermodynamics. Correct! an increase in entropy as predicted by the second law of thermodynamics.

an increase in entropy as predicted by the second law of thermodynamics.

Bioenergetics can be simply defined as the application of biological principles to physics. a subdivision of biology. the units in which energy is expressed. applied thermodynamics.

applied thermodynamics.

The methanobacteria, halobacteria, and sulfobacteria are included in which domain? blue-green algae protista archaea bacteria

archaea

lactose is a disaccharide formed by the formation of a ________ bond between glucose and _______________ a. glycosidic; lactose b. glycosidic; galactose c. hydrogen; sucrosed. hydrogen; fructose b. glycosidic; galactose

b. glycosidic; galactose

allosteric activator

binds to allosteric site and increases enzyme activity

All of the following are common functional groups found in biological molecules except __________ A. phosphate groups. B. carbonyl groups .C. butyl groups. D. amino groups.

butyl groups.

Proteolytic cleavage Alters the conformation of an enzyme to turn it on or off Activates an enzyme by cutting off part of the polypeptide chain Results when the final product of a pathway regulates an earlier step in the pathway Regulates enzymes by adding or removing chemical groups

by cutting off part of the polypeptide chain is basically the process of breaking the peptide bonds between amino acids in proteins. This process is carried out by enzymes called peptidases, proteases or proteolytic cleavage enzymes

dehydration synthesis leads to formation of a. monomers b. polymers c. water and polymersd. none of the above c. water and polymers

c. water and polymers

Cellulose belongs to which of the following groups of macromolecules? lipids carbohydrates nucleic acids proteins

carbohydrates

What inorganic precursors are needed to synthesize proteins? A. carbon, water, oxygen, nitrogen, and sulfur B. carbon, water, oxygen, nitrogen, and phosphate C. carbon, water, oxygen, and phosphate D. carbon, water, and oxygen A

carbon, water, oxygen, nitrogen, and sulfur

Which of the following is a structural polysaccharide? cellulose glycogen fructose starch

cellulose

Which of the following organelles is not generally found in animal cells? mitochondrion endoplasmic reticulum central vacuole food vacuole centriole

central vacuole

You wish to obtain a purified sample of mitochondria from lysed cells. The best way to obtain this sample would be centrifugation. chromatography. agarose gel electrophoresis. polyacrylamide gel electrophoresis.

centrifugation

polymer

chain of monomer residues that is linked by covalent bonds, polymerization is the process of polymer formation from monomers by condensation

Synthetic work refers to

changes in chemical bond,making something (photosynthesis) synthetic work is basically biosynthesis where new bond are formed and new molecules are synthesized. an example of this would be the process photosynthesis. mechanical work. this involves a physical change of the position or orientation of a cell or some part of the cell.

The term amphipathic refers to those molecules that are _____________________ A. hydrophilic .B. hydrophobic. C. charged at both ends but with opposite charges. D. charged at one end and nonpolar at the other.

charged at one end and nonpolar at the other.

What form of energy do all living organisms use? chemical bonds sunlight radiation nuclear energy

chemical bonds

Bioluminescence is:

chemical energy converted to light energy in biological organisms Bioluminescence and Fluorescence: The Production of Light. bioluminescence, the production of light using bioluminescence, the production of light using ATP or chemical oxidation as an energy source, and

Binds to the active site, blocking the substrate from binding

competitive inhibitor

Which of the following types of light microscopy improves the resolution of thick specimens by illuminating one plane of the specimen at a time? brightfield microscopy fluorescence microscopy confocal microscopyphase-contrast microscopy differential interference contrast microscopy

confocal microscopy

Experiments by Stanley Miller in the 1950s demonstrated that the first organic molecules on earth A) were nucleic acids such as RNA and DNA. B) most likely formed in an extraterrestrial environment and were deposited on earth via asteroids. C) could have formed abiotically in a reducing atmosphere containing hydrogen, methane, ammonia, and water vapor. D) were catalysts composed of simple amino acids. E) were catalysts composed of simple amino acids and most likely formed in an extraterrestrial environment and were deposited on earth via asteroids. could have formed abiotically in a reducing atmosphere containing hydrogen, methane, ammonia, and water vapor

could have formed abiotically in a reducing atmosphere containing hydrogen, methane, ammonia, and water vapor

A spontaneous reaction has an overall positive free energy change. could occur but might take a very long time. has to occur immediately. will never occur.

could occur but might take a very long time.

an example of monosaccharide is a. fructose b. glucose c. galactose d.all of the above

d. all of the above

When the size of a cell increases, the surface area/volume ratio decreases initially and then begins to increase. increases. remains the same. increases initially and then begins to decrease. decreases.

decreases.

scanning electron microscopy

detects electrons deflected from the surface of the specimen an electron microscope in which a beam of electrons is sent across the surface of a specimen and the reflected electrons are focused to produce a three dimensional image of the specimen surface.

transmission electron microscopy

detects electrons passing through a specimen electrons penetrate an ultrathin section of tissue to strike a photographic plate

Intermediate filaments are A) different in different cell types.B) smaller than actin filaments.C) composed of tubulin.D) composed of globular proteins only .E) None of these are correct. different in different cell types

different in different cell types.

Bioluminescence can be driven by ATP. either ATP or chemical oxidation. green fluorescent protein. chemical oxidation.

either ATP or chemical oxidation.

Which type of microscopy has the greatest resolving power?fluorescence microscopydigital video microscopyphase-contrast microscopyconfocal scanning microscopyelectron microscopy electron microscopy

electron microscopy

Which of the following biochemical techniques uses an electrical field to separate macromolecules based on their mobility through a semisolid gel? electrophoresis. light microscopy. mass spectrometry. ultracentrifugation. chromatography.

electrophoresis.

Which of the following statements about selfassembly is false? A. The noncovalent interactions that drive supramolecular assembly processes are similar to those that dictate the folding of individual protein molecules. B. Self-assembly only occurs in structures composed of protein. C. Self-assembly requires specific chemical conditions. D. Molecular chaperones are sometimes required for the proper folding and assembly of complex proteins. B

elf-assembly only occurs in structures composed of protein

Any process that results in an increase in the free energy of the system is called ________. endergonic

endergonic

Free Energy

energy that is available to do work

Which of the following is defined as "heat content"? entropy heat loss enthalpy energy output

enthalpy energy output

The lysosome contains which type of enzymes?

enzymes that break down large molecules into smaller molecules

Any process that results in a decrease in the free energy of the system is called ________. exergonic

exergonic

Energy-requiring reactions can occur in biological systems because they can be coupled with reactions that are unlikely. endergonic. not spontaneous. exergonic.

exergonic.

Mr. Jones, the science teacher, tells his students that energy cannot be created; it must be captured from the environment. He is talking about the _____.

first law of thermodynamics

Eukaryotic cells are believed to have arisen independently from prokaryotic cells. from the fusion of multiple archaeal cells into a larger, more complex cell. from a symbiotic relationship between primitive nucleated cells and bacterial cells. ) independently from prokaryotic cells by mutations that lead to changes in plasma membranes, leading to internal membrane-bound organelles.

from a symbiotic relationship between primitive nucleated cells and bacterial cells.

Reduction gain of electrons

gain of electrons ddition of hydrogen atoms (and a loss of oxygen atoms). Reduction reactions require an input of energy, as when carbon dioxide is reduced to glucose during photosynthesis, energy + 6CO2 + 6H2O S C6H12O6 + 6O2

Reduction involves the gain of electrons. increase in oxidation state. gain of electrons and an increase in oxidation state. loss of neutrons.

gain of electrons.

Which of the following processes would be most likely to occur in the Golgi complex? production and packaging of lipids synthesis of DNA synthesis of steroids detoxification of drugs Correct! glycosylation of proteins

glycosylation of proteins

Double-Reciprocal Plot

graphic method for analyzing enzyme kinetic data by plotting 1/v versus 1/[S] Shown here is an equation called the Lineweaver-Burk equation and the Double-Reciprocal Plot. Basically, by using the reciprocals of v, [S], and Vmax, we get a graph that forms a line, making it easier to understand.

which of the following is not a major functional class of proteins? A. hereditary proteins B. enzymes C. regulatory proteins D. structural proteins

hereditary proteins

To which of the following do Mendel's observations relate? gravity. thermodynamics. heredity. active transport.

heredity.

Hydrogen bonds are the principal force that _________________. A. connects amino acids into a polypeptide B. holds the two strands of DNA together C. allows Na+ and Ca2+ ions to bind proteins D. stabilizes fatty acid chains within a membrane

holds the two strands of DNA together

Which of the following is important in protein folding after the formation of a polypeptide? A. hydrogen bonding B. ionic bonding C. van der Waals interactions D. hydrogen bonding, ionic bonding, and van de Waals interactions.

hydrogen bonding, ionic bonding, and van de Waals interactions.

Energy is released as a result of which of the following chemical reactions? condensation dehydration synthesis hydrolysis dissolution

hydrolysis exergonic reaction

Scientists use various terms to describe conclusions reached through the scientific method. Which of the following terms conveys the least degree of certainty?law hypothesis theoryboth hypothesis and theoryboth theory and law hypothesis

hypothesis

Which of the following is an endothermic process? adding a strong acid directly to water combustion reactions You Answered oxidation of metals Answer ice melting

ice melting

Prions are simple viruses composed of protein. infectious circular RNA molecules that replicate in host cells. primitive protein particles that are believed to be an ancient precursor of living cells. infectious misfolded proteins that cause normal protein molecules to misfold. the site of protein synthesis in prokaryotic cells.

infectious misfolded proteins that cause normal protein molecules to misfold.

A peptide bond is a noncovalent bond that dictates the tertiary structure of a protein. is a covalent bond between the functional R groups of adjacent amino acids. is a covalent bond between adjacent glucose molecules in a peptide. Correct! is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid. is a covalent bond between the NH group of one polypeptide and the CO group of an adjacent polypeptide that holds together multimeric proteins.

is a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of a second amino acid.

An enzyme _____.is a source of energy for endergonic reactionscan bind to nearly any moleculeis an organic catalystis a inorganic catalystincreases the EA of a reaction

is an organic catalyst-Enzymes are proteins that behave as catalysts

Once a hypothesis becomes a scientific theory, it __________________ cannot be changed. cannot be challenged. becomes static. is subject to modification.

is subject to modification.

Proline is referred to as the "helix breaker" because _____________________ A. its only found in the L form, which is incompatible with helical protein structure. B. it lacks a charged functional groups for ionic bonding .C. it lacks the hydrogen atom needed for hydrogen bonding. D. it has a polar functional group.

it lacks the hydrogen atom needed for hydrogen bonding

In biological systems, work

k is the use of energy to drive any process other than heat flow. For example, work is performed when the muscles in your arm expend chemical energy to lift this book, when a corn leaf uses light energy to synthesize sugar, or when an electric eel creates the ion concentration gradients to deliver a shock. We will be primarily interested in the amount of useful energy available to do cellular work when we begin calculating energy changes associated with specific reactions in cells

Viroids differ from viruses in that they A) are acellular.B) lack capsid proteins.C) are self-replicating.D) have latent forms that exist in some genomes.E) are associated with plant diseases.

lack capsid proteins.

biological macromolecule

large molecule necessary for life that is built from smaller organic molecules

brightfield

light passes directly through specimen

As used in microscopy, the limit of resolution

limit of resolution refers to how far apart adjacent objects must be to appear as separate entities. For example, if the limit of resolution of a microscope is 400 nm, objects must be at least 400 nm apart to be recognizable as separate entities. The smaller the limit of resolution, the greater the resolving power, or ability to see fine details of structure, of the microscope. Therefore, a better microscope might have a resolution of 200 nm, meaning that objects only 200 nm apart can be distinguished from each other

Which of the following macromolecules is insoluble in water? A. lipids B. amino acids C. disaccharides D. nucleic acids

lipids

The smooth endoplasmic reticulum functions in synthesis of polysaccharides. DNA. Correct! lipids. lipids, polysaccharides, proteins, and DNA. proteins.

lipids.

Fatty acids are ________; they function in the cell as ________. A. long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids B. short chains of double-bonded carbon molecules; storage lipids C. short chains of double-bonded carbon molecules; vitamins and cofactors D. four-ringed hydrocarbon molecules; key components of membranes

long, unbranched hydrocarbon chains with a carboxyl group at one end; building blocks for other lipids

Which one of the following amino acids would most likely be important for forming ionic bonds with negatively charged DNA? A. glutamic acid B. lysine C. proline D. tyrosine

lysine

The main role of the central vacuole in plant cells is to synthesize and store proteins. store glycogen for seed growth. digest trapped food particles. catalyze photorespiration in association with chloroplasts. maintain turgor pressure in plant tissue.

maintain turgor pressure in plant tissue.

The steps of the scientific method, in the correct order, are______ make observations, formulate the hypothesis, design experiments, collect data, interpret results, and draw conclusions. design experiments, draw conclusions, collect data, interpret results, make observations, and test the hypothesis. collect data, interpret results, test the hypothesis, design experiments, make observations, and draw conclusions. collect data, interpret results, test the hypothesis, make observations, and design experiments.

make observations, formulate the hypothesis, design experiments, collect data, interpret results, and draw conclusions. make observations, formulate the hypothesis, design experiments, collect data, interpret results, and draw conclusions.

negative change in free energy

means that the products of the reaction have less free energy than the reactants, because they release some free energy during the reaction. Reactions that have a nega

Which of the following is characteristic of eukaryotic cells? membrane-bounded nucleus binary fission 70S ribosomes peptidoglycan cell wall

membrane-bounded nucleus

second law of thermodynamics states that In a closed system, every spontaneous physical or chemical change increases entropy All chemical reactions can occur without the input of energy Energy can change forms but is never created nor dest

n a spontaneous process, the entropy of the universe increases all spontaneous processes are thermodynamically irreversible. B entropy of the universe is continuously increasing. In a closed system, usable energy is lost over time to heat, although the total amount of energy remains the same First Law- Energy can neither be created nor be destroyed. It can change from one to another. The total energy of universe remains constant. Second Law- In a natural thermodynamic process the sum of the entropies of the interacting thermodynamic systems increases

Nucleotides

nucleotides consist of a sugar, a base, and phosphate groups.2 types of sugar: ribose and deoxyribose5 types of base: adenine, guanine, thymine, uracil, and cytosine.1-3 phosphate groups

The hierarchical nature of cellular structure is accurately illustrated in which of the following lists of substances (from smallest to largest)? A. nucleotides, DNA, chromosome, nucleus, cell B. nucleotides, chromosome, DNA, nucleus, cell C. cellulose, glucose, cell wall, cell D. protein, membrane, amino acids, chloroplast, cell A

nucleotides, DNA, chromosome, nucleus, cell

Which of the following pairs correctly matches the monomer with its polymer? A. amino acids; polysaccharides B. glucose; proteins C. nucleotides; nucleic acids D. terpenes; nucleic acids

nucleotides; nucleic acids

Spontaneous processes

occur without energy input; they can happen quickly or slowly are always accompanied by an increase in the entropy of the universe and a decrease in the free energy of the system

Oxidation occurs when an atom accepts electrons. occurs when oxygen atoms are added to a molecule and energy released. involves the removal of oxygen atoms from a molecule is endothermic.

occurs when oxygen atoms are added to a molecule and energy released.

Oxidation occurs when an atom accepts electrons. occurs when oxygen atoms are added to a molecule and energy released. involves the removal of oxygen atoms from a molecule is endothermic.

occurs when oxygen atoms are added to a molecule and energy released. Oxidation is the removal of electrons from a substance. In biology, oxidation usually involves the removal of hydrogen atoms (a hydrogen ion plus an electron) and the addition of oxygen atoms. Oxidation reactions release energy, as when either glucose or methane is oxidized

Open and Closed Systems.

open systems interact with other systems (closed systems do not interact with other systems) Open and Closed Systems. A system is that portion of the universe under consideration. The rest of the universe is called the surroundings of the system. (a) An open system can exchange energy with its surroundings, whereas (b) a closed system cannot. All living organisms are open systems, exchanging energy freely with their surroundings.

Phototrophs

organisms that get energy from light Phototrophs are producers that use solar energy to convert carbon dioxide and water into more reduced cellular compounds such as glucose during photosynthesis. These reduced compounds are converted into other carbohydrates, proteins, lipd

Removes electrons from a substance and releases energy

oxidation

The cell membrane can be described most accurately as ____________________ A. impermeable to all polar molecules .B. permeable to all small molecules and ions. C. permeable to some molecules and impermeable to others. D. permeable to all molecules except water.

permeable to some molecules and impermeable to others.

Glyoxysomes play an important role in the germination of fat-storing seeds and are considered to be specialized A) peroxisomes .B) lysosomes.C) vacuoles.D) centrioles.E) ribosomes.

peroxisomes

Which type of microscope can detect density differences and thereby see organelles in living cells? phase contrast SEM TEM fluorescence

phase contrast

Lignin is an important component in tight junctions. plant cell walls. plasmodesmata. bacterial cell walls. fungal cell walls.

plant cell walls.

hydrolysis

reaction causes breakdown of larger molecules into smaller molecules with the utilization of water التحلل المائي يؤدي التفاعل إلى انهيار الجزيئات الكبيرة إلى جزيئات أصغر باستخدام الماء

Membrane proteins may function in amphipathic modification. protein manufacture. temperature control. information storage. receiving extracellular signals.

receiving extracellular signals.

Phosphatase enzymes

remove phosphate groups phosphate group can be removed again via another enzyme called a phosphatase

Which sequence reflects the locations that a secretory protein will visit on its way from its production to its secretion outside the cell? Correct! rough ER, ER vesicle, Golgi complex, secretory vesicle nucleus, Golgi complex, rough or smooth ER, secretory vesicle rough ER, Golgi complex, smooth ER, ER vesicle smooth ER, rough ER, Golgi complex, secretory vesicle rough ER, secretory vesicle, Golgi complex, ER vesicle

rough ER, ER vesicle, Golgi complex, secretory vesicle

Which sequence reflects the locations that a secretory protein will visit on its way from its production to its secretion outside the cell? A) rough ER, secretory vesicle, Golgi complex, ER vesicle B) rough ER, Golgi complex, smooth ER, ER vesicle C) nucleus, Golgi complex, rough or smooth ER, secretory vesicle D) rough ER, ER vesicle, Golgi complex, secretory vesicle

rough ER, ER vesicle, Golgi complex, secretory vesicle

Enzyme regulation may occur by several methods. Which of the following is not a means of enzyme regulation?saturationallosteric regulationsubstrate-level phosphorylationcovalent modificationfeedback inhibition saturation

saturation

In every physical or chemical change, the universe tends toward greater disorder. This is the ________ law of thermodynamics, or the law of thermodynamic ________. second; spontaneity

second; spontaneity

Hydrogen bonding is most important in stabilizing the ________ structure of many proteins. A. primary B. secondary C. tertiary D. quaternary

secondary

The cytosol is best described as the A) three-dimensional array of interconnected filaments. B) semifluid substance in which organelles are suspended. C) internal contents of organelles. D) area of the cell not occupied by the nucleus. E) fluid within the nucleus. b(cytosol i a semifluid substance, while interconnected filaments build upp the cytoskeleton)

semifluid substance in which organelles are suspended b(cytosol i a semifluid substance, while interconnected filaments build upp the cytoskeleton)

monomer

smallest unit of larger molecules called polymers

a negative ∆G corresponds to an ________________(increase/decrease) in free energy?

spontaneous

negative ∆G

spontaneous

Cholesterol is a ________, which ________. ! steroid; is a component of eukaryotic membranes and is the basis for many animal and plant hormones fatty acid; functions in energy storage steroid; is the basis for many animal and plant hormones steroid; is a component of eukaryotic membranes

steroid; is a component of eukaryotic membranes and is the basis for many animal and plant hormones

Cytology

study of cells

What name is given to the reactants in an enzymatically catalyzed reaction?products EAactive sites substratereactors substrate

substrate

What is Michaelis constant (Km)?

substrate concentration at which an enzyme-catalyzed reaction is proceeding at one-half of its maximum velocity

energy the ability to do work

the ability to do work is the capacity to cause specific physical or chemical changes. Because life is characterized first and foremost by change, this definition emphasizes the total dependence of all forms of life on the continuous availability of energy

The steady state vital to life is possible because the cell cannot convert energy from one form to another. all cells are autotrophic. all reactions are at equilibrium. Correct! the cell continually takes up energy from the environment.

the cell continually takes up energy from the environmen

The limit of resolution can best be defined as Correct! the distance that two objects must be apart to be distinguished as separate objects. the distance that an object must be moved to be distinguished from its background. the magnification power of a microscope. the inverse of the wavelength of light; it is greatest for black light.

the distance that two objects must be apart to be distinguished as separate objects.

The scientific work that established DNA, rather than protein, as the molecule of heredity was performed prior to ________________ Mendel's work on heredity. Antonie van Leeuwenhoek's observation of internal cell structures. . the elucidation of the double helix structure of DNA. the formation of the chromosome theory of heredity.

the elucidation of the double helix structure of DNA.

"The total amount of mass-energy in the universe is constant," is a statement of the second law of thermodynamics. entropy. the first law of thermodynamics. thermodynamic spontaneity.

the first law of thermodynamics.

allosteric inhibition

the mechanism for inhibiting enzyme action in which a regulatory molecule binds to a second site (not the active site) and initiates a conformation change in the active site, preventing binding with the substrate

DNA sequencing

the process of determining the precise order of nucleotides within a DNA molecule DNA sequencing has over nucleic acid hybridization. DNA sequencing makes it possible to determine the order of individual nucleotides along a DNA strand.

Synthetic Work (biosynthesis)

the process of photosynthesis

-The Michaelis-Menten reaction describes

the rate of catalysis of the enzyme at some particular substrate concentration.

A negative free energy change indicates that A) the reaction is not possible. B) energy must be added to the reaction before it can proceed .C) the reactant is predominant at equilibrium. D) the reaction is exothermic. E) the reaction is at equilibrium

the reaction is exothermic

A negative free energy change indicates that the reaction is not possible. energy must be added to the reaction before it can proceed. the reactant is predominant at equilibrium. the reaction is exothermic.

the reaction is exothermic.

internal energy

the sum of the kinetic and potential energies of all particles in the system

which is an accurate description of the flow of energy?

the sun, to chemotrophs, who give off energy as heat; phototrophs then capture the heat and use it as energy.

Viruses are important in the study of cell biology because they are the simplest form of cellular life. they are the simplest form of cellular life and are used as model organisms to study molecular biology and genetics. they cause disease and are used as model organisms to study molecular biology and genetics. they cause disease. they are used as model organisms to study molecular biology and genetics.

they cause disease and are used as model organisms to study molecular biology and genetics.

The function of triglycerides is__________________ store information. to store energy. to transport substances in and out of cells. to form semipermeable membranes.

to store energy

phase-contrast

transforms subtle changes in light waves passing through the specimen into differences in light intensity, best for observing intracellular structures amplifies variation in density

In which of the following properties are the archaea more like eukaryotes than the bacteria? A) size B) microtubules and microfilaments C) translation initiation D) mode of cell division E) both translation initiation and mode of cell division

translation initiation

You are working on a project that involves the direct observation of DNA molecules. The microscope that would give you the best information at this time would be the_______________light microscop transmission electron microscope. phase-contrast microscope. digital video microscope. light microscope. fluorescent microscope.

transmission electron microscope.

Which of the following is found exclusively in RNA? A. thymine B. uracil C. guanine D. adenine

uracil

What is structurally different about cellulose when compared to starch? an extra hydrogen atom is left on the monomer ββ-1,4 glycosidic linkages are used αα-1,6 glycosidic linkages are used an extra hydroxyl group is removed during synthesis

ββ-1,4 glycosidic linkages are used

•Substrate activation provides the right environment for catalysis •

• •Common mechanisms •Bond distortion: makes the bond more susceptible to catalysis •Proton transfer: increases substrate reactivity •Electron transfer: results in temporary covalent bonds between enzyme and substrate

Regulation may also act on the enzyme

•Amount of enzyme •Feedback inhibition •Allosteric regulation •Covalent modification

Common properties of all catalysts

•Common properties of all catalysts: •They speed the rate of chemical reactions •They lower the activation barrier •They form transient, reversable complexes with substrate molecules •They stabilize the transition state. •They do not change spontaneity. •Common properties of biological catalysts: •They are either protein enzymes or RNA ribozymes. •They are more specific than inorganic catalysts. •They can be regulated by cells.

•Substrate-level regulation:

•Substrate-level regulation: regulation which depends on interactions of substrates and products. •Changing substrate and product concentrations •Changing temperature and pH •Presence and concentration of inhibitors •

•Ribozymes are catalytic RNA molecules •Examples include:

•Tetrahymena •Ribonuclease P Ribosomal RNA

•The overall sequence of eventsr catalysis is as follows: •.

•The overall sequence of events is as follows: •The substrate and active site randomly collide •The substrate binds to the enzyme •A conformational change tightens the enzyme-substrate bond •The chemical reaction occurs •The products are released •The original conformation is restored •The enzyme can now bind another molecule.