Chapter 5-Microbial Metabolism

What are enzymes?

Enzymes are biological catalysts•Enzymes act on a specific substrate and lower the activation energy

Stages of cellular respiration:

Glycolysis, kreb cycle and electron transport chain. (Glycolysis does not require oxygen, but kreb cycle and the electron transport chain do-aerobic processes)

enzymatic activity

(rate of reaction catalyzed by the enzyme) increases with increasing temperature until the enzyme, a protein, is denatured by heat and inactivated. At this point, the reaction rate falls steeply.

Streptococci lack an electron transport chain. How many molecules of ATP can a Streptococcus cell net from one molecule of glucose? 10 YOU WERE UNSURE AND INCORRECT 36 *2 1 38

*2

In the light-dependent reactions of photosynthesis: Oxygen is used to synthesize sugars carbon dioxide is used to synthesize sugars. glucose is oxidized. ADP is converted to ATP.

*ADP is converted to ATP (using energy from light)

Which of the following would you predict to be a feedback inhibitor of the glycolytic enzyme phosphofructokinase? ATP FAD ADP NAD+ fructose

*ATP

Which of the following statements accurately describes the difference between aerobic and anaerobic respiration? Aerobic respiration uses an organic molecule as the final electron acceptor, and anaerobic respiration uses an inorganic molecule as the final electron acceptor. Aerobic respiration uses oxygen as the final electron acceptor, and anaerobic respiration uses either an inorganic molecule, such as nitrate ions or sulfate ions, or an organic molecule, such as an acid or alcohol. Aerobic respiration uses O2 as the final electron acceptor, whereas anaerobic respiration uses H2O. Anaerobic respiration uses oxygen as the final electron acceptor, and aerobic respiration uses either an inorganic molecule, such as nitrate ions or sulfate ions, or an organic molecule, such as an acid or alcohol. Anaerobic respiration uses an organic molecule as the final electron acceptor, and aerobic respiration uses an inorganic molecule as the final electron acceptor.

*Aerobic respiration uses oxygen as the final electron acceptor, and anaerobic respiration uses either an inorganic molecule, such as nitrate ions or sulfate ions, or an organic molecule, such as an acid or alcohol.

Enzymes work most effectively at their optimal __________. amount of substrate temperature pH All of the listed answers

*All of the listed answers

__________ may serve as substrate(s) of glycolysis Sugars Lipids None of the listed answers. Proteins All of the listed answers

*All of the listed answers

At the completion of the Krebs cycle, the carbons from glucose are found in __________. FADH2 pyruvic acid CO2 NADH

*CO2

Which of the following statements is correct about enzymes? Each enzyme has a characteristic three-dimensional shape. Enzymes raise the activation energy of the reaction. Enzymes have active sites that interact with a variety of different molecules. Enzymes are used up in the reactions they catalyze.

*Each enzyme has a characteristic three-dimensional shape.

A coenzyme assists an enzyme by accepting or donating matter. What does NAD+transfer? Phosphate groups ATP Acetyl groups Electrons Acetyl CoA

*Electrons

The addition of phosphate to a chemical compound is called

phosphorylation

Two major types of carbohydrate metabolism:

respiration-sugar is completely broken down fermentation-sugar is partially broken down

Metabolic pathways of energy production

series of enzymatically catalyzed chemical reactions; extracts energy from organic compounds and stores it in chemical form (ATP)

catalyst

substance that speeds up the rate of a chemical reaction without being altered.

Glycolysis produces ATP through __________.

substrate-level phosphorylation

Glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid as an end product. The overall (net) products of glycolysis are: 2 pyruvic acid, 2 ATP, 2 NADH

oxidation-reduction reaction

the removal of electrons from a substrate. Protons (H+) are often removed with the electrons

Metabolism

the sum of all chemical processes that occur in an organism. It is the build up and break down of nutrients within a cell. These chemical reactions provide energy and create substances that sustain life.

When do chemical reactions occur?

when chemical bonds are formed or broken.

Oxidative Phosphorylation

•Electrons are transferred from one electron carrier to another along an electron transport chain (system) on a membrane that releases energy to generate ATP •Chemiosmosis is the term for the process wherein ATP is generated from ADP using the energy derived from the electron transport chain

Photophosphorylation

•Occurs only in photosynthetic cells with light-trapping pigments such as chlorophylls •Light energy is converted to chemical energy in the form of ATP during the transfer of electrons (oxidation) from chlorophyll as they pass through a system of carrier molecules

Carbohydrate Catabolism

The breakdown of carbohydrates to release energy typically occurs in three principle stages •Glycolysis•Krebs cycle•Electron transport chain (system)

The five-carbon sugars of nucleotides are derived from either the ________ or ________. •pentose phosphate pathway; Entner-Doudoroff pathway •pentose phosphate pathway; the Krebs cycle •Entner-Doudoroff pathway; glycolysis •glycolysis; the Krebs cycle

•pentose phosphate pathway; Entner-Doudoroff pathway

Most of a cell's energy is produced from the oxidation of ______.

carbohydrates

Which enzyme catalyzes the reaction: 2H2O2 → 2H2O + O2(breakdown of hydrogen peroxide to water and oxygen)?

catalase

Catabolic and anabolic reactions are linked by______________

energy! Catabolic reactions provide the energy necessary for anabolic reactions.

Two key players in metabolism are:

enzymes and the molecule adenosine triphosphate (ATP) Enzymes catalyze reactions for specific molecules called substrates. During enzymatic reactions, substrates are transformed into new substances called products.

The pentose phosphate pathway provides a means to break down glucose and:

five-carbon sugars.

A molecule that undergoes reduction

gains one or more electrons

turnover number

maximum number of substrate molecules an enzyme molecule converts to product each second

All of the following steps are involved in the aerobic electron transport chain. Which step happens last? Electrons are transferred to O2. Electrons flow between membrane-bound electron carriers. NADH is oxidized. Protons move to the outside of the membrane. NAD+ is formed.

*Electrons are transferred to O2.

The complete oxidation of glucose in aerobic and anaerobic respiration involves which three stages? Chemiosmosis, photophosphorylation, and reduction Photosynthesis, fermentation, and oxidation Glycolysis, Krebs cycle, and the electron transport chain Substrate phosphorylation, pentose phosphate shunt, and the Calvin cycle

*Glycolysis, Krebs cycle, and the electron transport chain

One of the sites of allosteric regulation of the Krebs cycle is the conversion of pyruvic acid to acetyl CoA. Which of the following conditions would you expect to inhibit the conversion of pyruvic acid to acetyl CoA? Low ATP and low NADH High ATP and low NADH Low ATP and high NADH High ATP and high NADH High ADP and low NADH

*High ATP and high NADH

All of the following are considered cofactors except catalase NAD+ some vitamins iron

*NAD+

During glycolysis, electrons from the oxidation of glucose are transferred to __________. ADP FAD NADH FADH2 NAD+

*NAD+

Which of the following molecules carry electrons during various stages of glucose catabolism? Pyruvic acid NADH and FADH2 Acetyl CoA Glucose

*NADH and FADH2

Which of the following pairs is NOT correctly matched? Catabolism; breakdown of organic compounds Anabolism; building of complex molecules Metabolism; sum of all chemical reactions Oxidation; reaction in which electrons are gained Metabolic pathways; sequences of chemical reactions

*Oxidation; reaction in which electrons are gained

Which of the following four stages of glucose oxidation during aerobic respiration requires molecular oxygen? Oxidative phosphorylation Krebs cycle Production of acetyl CoA Glycolysis

*Oxidative phosphorylation

Which of the following statements is accurate concerning glucose metabolism? Pyruvic acid, the product of glycolysis, is the starting block for both the Krebs cycle and fermentation. Fermentation produces large amounts of ATP. Glucose is split in glycolysis and produces large amounts of ATP. The electron transport chain is the final step for both fermentation and aerobic respiration.

*Pyruvic acid, the product of glycolysis, is the starting block for both the Krebs cycle and fermentation.

Which of the following mechanisms does NOT generate ATP using an electron transport chain? Substrate-level phosphorylation Aerobic respiration Photophosphorylation Anaerobic respiration

*Substrate-level phosphorylation

The complete oxidation (catabolism) of glucose typically involves three stages. The greatest number of ATPs is produced in which stage? The electron transport chain Krebs cycle Glycolysis Photosynthesis

*The electron transport chain

Metabolic pathways that function in BOTH anabolism and catabolism are called ________pathways. •intermediate •reversible •redox •amphibolic

*amphibolic

The proton motive force is __________. ATP accumulation in the mitochondria the movement of water across a membrane an electrochemical gradient formed across a membrane the movement of flagella the accumulation of water formed in respiration

*an electrochemical gradient formed across a membrane

In anaerobic respiration, the final electron acceptor is: •oxygen. •ATP. •an inorganic molecule other than oxygen. •an organic molecule.

*an inorganic molecule other than oxygen.

The chemical reactions involved in synthesizing proteins and cell wall peptidoglycan are examples of __________ reactions. autotrophic anabolic photosynthetic catabolic

*anabolic

Enzymes are important in living organisms because they __________. catalyze the covalent bonding of NAD⁺ molecules to substrates bring together reactants or properly orient a molecule for a reaction bind irreversibly to substrates and remove them from the cellular pool interact with and destroy unwanted cellular substrates increase environmental temperatures to increase rates of reactions

*bring together reactants or properly orient a molecule for a reaction

Competitive inhibition of enzyme action involves __________. irreversible binding to the enzyme's active site competition with the substrate for binding at the active site alteration of the enzyme's active site competition for binding at the enzyme's allosteric site destruction of the enzyme's substrate

*competition with the substrate for binding at the active site

All of the following are required for the generation of ATP by chemiosmosis EXCEPT __________. formation of a proton motive force conversion of pyruvic acid to lactic acid passage of electrons through electron carrier chains use of proton flow by ATP synthase active transport of protons across a phospholipid membrane

*conversion of pyruvic acid to lactic acid

In __________ an end-product of an anabolic pathway inhibits the activity of one or more enzymes in a pathway. negative feedback feedback inhibition inhibition positive feedback

*feedback inhibition

Unlike chemiosmosis in eukaryotes, prokaryotes chemiosmosis __________. occurs at the plasma membrane and not the mitochondria electrons are eventually passed to organic molecules instead of inorganic acceptors does not require a membrane moves iron instead of protons across the membrane does not require ATP synthase

*occurs at the plasma membrane and not the mitochondria

All of the following pairs are correctly matched EXCEPT __________. anabolism—building of complex molecules catabolism—breakdown of more complex organic compounds metabolic pathways—sequences of chemical reactions oxidation—reaction in which electrons are gained metabolism—sum of all chemical reactions

*oxidation—reaction in which electrons are gained

NADH molecules formed during glycolysis and in the Krebs cycle are __________. stored in the mitochondria oxidized when electrons are needed in anabolic pathways oxidized when electrons are passed to the electron transport chain oxidized when electrons are passed to NADP+ transported out of the cell during oxidative phosphorylation

*oxidized when electrons are passed to the electron transport chain

All of the following are potential end-products of fermentation EXCEPT __________. lactic acid pyruvic acid ethanol acetic acid carbon dioxide

*pyruvic acid

Which of the following processes does not generate ATP? the Calvin-Benson cycle photophosphorylation substrate-level phosphorylation oxidative phosphorylation

*the Calvin-Benson cycle (this process uses ATP. It does not generate it)

Fermentation differs from anaerobic respiration in that fermentation does NOT __________. use an electron transport chain oxidize NADH require molecular oxygen oxidize glucose

*use an electron transport chain

Fermentation

A catabolic process that makes a limited amount of ATP from glucose (sugar) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid. O2 is not required in fermentation.

The generation of ATP:

ATP is generated by the phosphorylation of ADP with the input of energy. ATP is generated when high-energy is added to ADP The energy from catabolic reactions is used to produce ATP

Components of a holoenzyme.

Apoenzyme-protein portion of an enzyme Cofactor-(nonprotein portion),activator Together, the apoenzyme (protein portion) and cofactor (non protein component) form a : Holoenzyme(whole, active enzyme). Apoenzymes are not active by themselves. They must be activated by cofactors. If the cofactor is removed the apoenzyme will not function.

Light Independent Reactions (Calvin Cycle)

C02 is used to synthesize sugars.

Anabolism

Chemical reactions in which simpler substances are combined to form macromolecules.These reactions REQUIRE energy. The energy stored in ATP is released during catabolic reactions and then used to create anabolic reactions. Anabolic processes often involve reactions that release water and are endergonic-consume more energy than they produce. Example of anabolic reaction-formation of proteins from amino acids, nucleic acids from nucleotides, and polysaccharides from simple sugars.

Competitive and noncompetitive inhibitors

Competitive inhibitor-inhibitor binds to enzyme somewhere on active site and competes with the normal substrate. Non competitive inhibitor-inhibitor binds to enzyme somewhere other than active site. Changes shape of active site.

Photosynthesis

Conversion of light energy from the sun into chemical energy. That chemical energy is used for carbon fixation.

Acronym to remember this: LEO-GER

Loses an electron---oxidation Gains an electron---reduction

Catabolism

Metabolic pathways that break down macromolecules into simpler components, RELEASING energy along the way. Catabolic reactions are used to drive anabolic reactions. Energy for chemical reactions is stored in ATP. Catabolic Reactions are generally hydrolytic reactions (reactions which use water and in which chemical bonds are broken). They are exergonic-produce more energy than they consume. Example -when cells break down sugars into carbon dioxide and water

Lipid and Protein Catabolism

Microbes can oxidize lipids and proteins as a source of energy

In an enzymatic reaction involving oxidation of a substrate, which of the following would be required?

Nad+

In what process does the aerobic electron transport chain participate?

Oxidative phosphorylation

types of chemical reaction catalyzed

Oxidoreductase-oxidation-reduction, in which oxygen and hydrogen are gained or lost Transferase-Transfer of functional groups, such as amino group, acetyl group, or phosphate group Hydrolase-hydrolyosis (splitting of water. Hydro meaning water and lysis meaning seperate) Lyase-removal of groups of atoms without hydrolysis Isomerase-rearrangment of atoms within a molecule Ligase-Joining of 2 molecules (using energy usually derived from the breakdown of ATP)

Photosynthesis in plants, algae, and cyanobacteria produces:

Oxygen

In which one of the following processes is light energy converted to ATP, which is then used to synthesize organic molecules?

Photosynthesis

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Carbon Fixation

The synthesis of sugars by using carbon atoms from CO2 gas.

Glycolysis is carried out by cells in both respiration and fermentation.

True

Why is energy important in cell metabolism?

Without energy, certain reactions will never occur, even if enzymes are present. ATP is a molecule that microbes and other cells use to manage energy needs. If a reaction results in too much energy, some can be captured in the form of ATP bonds. ATP stores energy derived from catabolic reactions and releases it later to drive anabolic reactions and perform other cellular work. A cell can then break down those bonds and use the released energy to fuel other reactions.