Assessment 3: CH13-16

Recall what organisms require to perform biosynthesis. Which of these is correct?

• Energy to perform biosynthesis

• Reduction of substrate

• All

• Essential elements (such as carbon, oxygen, hydrogen, nitrogen, etc.)

All

Explain how the proton motive force is produced.

Proton motive force is generated by proton pumping through cell membranes.

True/False

True

Recall different means of food preservation and describe how they work. Use one of these keys: chemical; physical.

[A] means of preservation is specific processes that preserve food based on temperature, pressure, water activity. For examples: dehydration and freeze drying, refrigeration and freezing, controlled or modified atmosphere, pasteurization, canning, and ionizing radiation. [B] means of preservation is many kinds of chemicals are used to preserve foods. For examples: acids, esters, other organic compounds, and inorganic compounds.

[A] Physical [B] Chemical

Differentiate between food spoilage and food contamination, and differentiate between rancidity and putrefaction. Use one of these keys: food contamination; food spoilage; putrefaction; rancidity.

[A] is the microbial changes that make a product obviously unfit for consumption. Food may spoil through degradation of enzymes, chemical reactions, and microbial metabolism. [B] (or food poisoning) is when the presence of microbial pathogens cause human disease. The spread of these pathogens can occur through food harvesting, food processing, and shared consumption. [C] is the spoilage of alkaline products, particularly fats, whereas [D] is the spoilage of amino acid spoilage.

[A] Food spoilage [B] Food contamination [C] Rancidity [D] Putrefaction

Define single-celled protein.

Single-celled proteins are proteins derived from single cells of microorganisms such as bacteria.

True/False

True

State how acid and alkaline fermentation preserves food.

Several food fermentations produce acids and bases which serve as an effective preservative because pH change is not likely to be reversed.

True/False

True

Identify some food and industrial applications of microbial fermentation. Which of these is incorrect?

• Making of food ingredients

• All but one

• Making of ethanol

• Preservatives

• Making of dairy products

• Making of beverages

• All but two

• None

None

Name the three main catabolic routes from glucose to pyruvate. Which of these is correct?

• The Embden-Meyerhof-Parnas pathway (EMP); the Calvin cycle ; the Pentose phosphate pathway (PPP)

• The Calvin cycle; the Entner-Doudoroff pathway (ED); the Pentose phosphate pathway (PPP)

• The Embden-Meyerhof-Parnas pathway (EMP); the Entner-Doudoroff pathway (ED); the Pentose phosphate pathway (PPP)

• The Embden-Meyerhof-Parnas pathway (EMP); the Entner-Doudoroff pathway (ED); the Calvin cycle

The Embden-Meyerhof-Parnas pathway (EMP); the Entner-Doudoroff pathway (ED); the Pentose phosphate pathway (PPP)

Describe the structure and function of carboxysomes. Which of these is correct?

• They convert bicarbonates back to CO2 for the use in the Calvin cycle.

• Carboxysomes are found within the CO2-fixing Lithotrophs, as well as within the cyanobacteria and chloroplasts.

• All but two

• All but one

• The carboxysome takes up bicarbonate. Its function is to fix CO2.

• It consists of a polyhedral shell of protein subunits surrounding tightly packed molecules of Rubisco.

• All

All

Identify the fates of glyceraldehyde 3-phosphate in the Calvin Cycle.

One of every six G3P molecules is converted to glucose or amino acids. The other five molecules of G3P undergo reactions to regenerate ribulose 1,5-biphosphate.

True/False

True

Recall the types of microbes that are edible.

• mushroom

• All

• fruiting bodies of fungi

• fronds of marine

• All but one

• spirulina

• All but two

All

Recall the functions of food fermentation. Which of these is incorrect?

• The lactic acid is also what gives fermented foods that very specific tangy or acidic taste.

• Food fermentation breaks down carbs, like starches and sugars by bacteria and yeast to alcohol or organic acids.

• None

• All but two

• All but one

• As the microorganisms divide, lactic acid is formed, which stops the growth of bad bacteria.

• It is used to make dairy and alcoholic products.

None

Define cheese, curds, starter culture and whey.

A [A] is any milk product from a mammal when the protein coagulates to form a semisolid [B]. Curds are dairy products made from curdling milk and contains lactic acid. A [C] is a microbiological culture that performs fermentation. [D] is the liquid remaining after milk has been curdled.

[A] Cheese [B] curd [C] starter culture [D] whey

Name the types of organisms capable of N2 fixation.

• Bacteria

• All

• Arcahea

• All but two

• Plants

• Eukaryotes

All but two

Compare and contrast wine production with beer and bread production.

All three forms of production, wine, beer, and bread, all require a form of ethanolic fermentation. With [A] and [B] production, they require fermentation of grains and yeast. [C] production is from fermentation of fruit, with the most common being grapes.

[A] beer [B] bread [C] wine

Describe what distinguishes a pathogen from a spoilage organism.

Spoilage organisms don’t cause life-threatening infections. Food pathogens will make you sick, and even cause death. A pathogen is a biological agent that causes disease or illness to its host.

True/False

True

Assess the ecological importance of microbial N2 fixation. Which of these statements is correct?

• Nitrogen is an essential element of all living things, but most organisms do not have the ability to acquire nitrogen through N2 fixation.

• All living organisms, directly or indirectly, depend on N2-fixing prokaryotes within the biosphere.

• All other organisms that do not retain the ability to fix their own N2 depend on reduced or oxidized forms of nitrogen, which ultimately derive from N2.

• All

All

Recall which organisms conduct the Calvin Cycle. Which of these is correct?

• Photoautotrophs such as cyanobacteria

• All but two

• photosynthetic organisms

• lithoautotrophic bacteria.

• facultatively anaerobic purple bacteria

• All but one

• All

All

Identify different types of fermented foods. Which of these is not a type of fermented food.

• None

• Cheese

• Yogurt

• Beer

• Thousand-year eggs

• Milk

• Kimchi

• Soy sauce

Milk

Compare and contrast the three minimum components of a respiratory ETS. Use one of these keys: initial substrate oxidoreductase; mobile electron carrier; terminal oxidase.

Respiratory electron transport is essential in in generating ATP molecules. Respiratory electron transport systems include three components known as initial substrate oxidoreductase, mobile electron carrier, and terminal oxidase. Respiratory ETS begins with the [A] which receives a pair of electrons from an organic substrate. The [B] do just as the name would suggest; they are responsible for transporting electrons from one carrier to another. A(n) [C] complex receives electrons from a quinol and transfers them to a terminal electron acceptor.

[A] initial substrate oxidoreductase [B] mobile electron carrier [C] Terminal oxidase

Define energy carriers and provide examples.

Energy carriers are a molecule in the cell, such as ATP or NADH, that serves as energy currency. Energy carriers are produced during catabolic reactions and can be used to drive energy-requiring reactions. Examples of energy carriers are ATP and NADH.

True/False

True

State the role of cytochromes and oxidoreductases in an ETS. Use one of these keys: cytochromes; oxidoreductases.

[A] are membrane proteins that donate and receive electrons. [B] are electron transport system proteins that accept electrons from one molecule, and donate electrons to a second molecule, thereby reducing the second molecule.

[A] Cytochromes [B] Oxidoreductases

Recall why metabolic reactions require enzymes. Which of these statements is correct?

• All but two

• Enzymes act as catalysts.

• Enzymes are proteins.

• Enzymes assist in the transferring of electrons from one molecule to another.

• All but one

• Enzymes speed up the rate of a chemical reaction.

• Enzymes lower the activation energy by bringing the substrates in proximity to one another and they correctly orient them to react.

• All

All

Describe the function of membranes in an ETS.

The membrane embeds the ETS and separates it into two compartments. Two aqueous compartments must be separated to maintain an ion gradient generated by the ETS. This enables the formation of proton motive force and the generation of ATP by the ATPase protein.

True/False

True

Recall the conditions required for the standard Gibbs free energy change, ΔG°, and the biochemical Gibbs free energy change, ΔG°′. Which of these is the correct conditions required for the biochemical Gibbs free energy change, ΔG°′.

• 298 K, 1 atm, and all concentrations of substrates and products are 1 molar, plus the biochemically relevant conditions of pH 7 and water.

• 298 K, 1 atm, and all concentrations of substrates and products are 1 molar.

298 K, 1 atm, and all concentrations of substrates and products are 1 molar, plus the biochemically relevant conditions of pH 7 and water.

Define CO2 fixation.

Carbon dioxide fixation is the enzymatic reduction and covalent incorporation of inorganic carbon dioxide into an organic compound. It is carried out by the Calvin cycle.

True/False

True

Outline the key steps of the Calvin cycle; where possible include relevant enzymes and substrates. Which of the following is correct?

It takes place in this 3-stepwise sequence:

Carboxylation and splitting: 6C -> 2[3C]). Ribulose 1, 5-biphosphate condenses with CO2 and H2O. mediated by Rubisco. Rubisco generates a six-carbon intermediate, which immediately hydrolyzes. The split produces two molecules of PGA, one of which contains the CO2 fixed by this cycle.

Reduction of PGA to G3P: the carboxyl group of each PGA molecule is phosphorylated by ATP. The phosphorylated carboxyl group is then hydrolyzed and reduced by NADH, forming G3P.

Regeneration of ribulose 1,5-biphosphate: of every six G3P, resulting from three cycles of fixing CO2, five G3P enter a complex series of reactions to generate. The net conversion of five G3P molecules to three molecules of ribulose 1, 5-biphosphate releases 2H2O, restoring two of the 3H2O fixed with 3CO2. The remaining sixth G3P exits the cycle, available to be used in the biosynthesis of sugars and amino acids. Thus, three fixed carbons lead to one three-carbon product.

Explain why different foods are subject to different types and rates of spoilage.

Different foods spoil in different ways depending on their nutrient content, the microbial species, and environmental factors such as temperature.

True/False

True

Define catabolism, energy, enthalpy, and entropy.

[A] is the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy; destructive metabolism. [B] is the ability to do work. [C] is a measure of the heat energy in a system. [D] is a measure of the disorder in a system.

[A] Catabolism [B] Energy [C] Enthalpy [D] Entropy

State the changes that occur in foods post-harvest. Use one of these keys: food contamination; food spoilage; putrefaction; rancidity.

Several chemical changes occur. [A] is microbial changes that render a food unfit or unpalatable for consumption. [B] is food spoilage due to the oxidation of fats; it may or may not involve microbial activity. [C] is food spoilage due to the decomposition of proteins and amino acids. [D] or food poisoning is food contamination, the presence of human disease-causing microbial pathogens or toxins in food.

[A] Food spoilage [B] Rancidity [C] Putrefaction [D] Food contamination

Categorize microbes based on how they acquire energy. Use one of these keys: chemolithotrophy; chemoorganotrophy; phototrophy.

[A] is organic compounds donate electrons. [B] is inorganic compounds donate electrons. [C] is light absorption that provides electrons.

[A] Chemoorganotrophy [B] Chemolithotrophy [C] Phototrophy

Recall the definitions of oxidation and reduction.

[A] means a reaction in which electrons are added to a compound; the compound that gains electrons is said to be reduced. [B] is an energy-producing reaction in living cells, and it is coupled with a reduction reaction.

[A] Reduction [B] Oxidation

Identify the fates of fatty acids and polyketides.

Fatty acids condense with glycerol to form the phospholipids of cell membranes and the lipid components of envelope proteins. Polyketide antibiotics are synthesized by modular enzymes.

True/False

True

Recall the major forms of catabolism. Which of these is incorrect?

• anabolism

• All but three

• fermentation

• All but two

• Respiration

• Glycolysis

• metabolism

All but three

Compare various types of fermentation. Use one of these keys: ethanolic; heterolactic; lactic acid; propionic acid.

There are various types of fermentation. [A] fermentation is when glucose is fermented to lactic acid by lactic acid bacteria such as Lactobacillus- this is in cheese and sausages. [B] fermentation is a second-stage fermentation when lactic acid goes to propionic acid by the bacteria Propionibacterium- this adds the special flavor of Swiss cheese. [C] fermentation involves production of lactic acid, CO2, and some acetic acid and ethanol. This process is conducted by Leuconostoc- takes place with certain vegetables like sauerkraut. [D] fermentation, conducted by yeast, is fermentation to ethanol plus carbon dioxide without lactic acid- as with alcoholic beverages.

[A] Lactic acid [B] Propionic acid [C] Heterolactic [D] Ethanolic

Name two examples for each of these food preservation process:

physical:

chemical:

Which of these is correct?

• Physical means: dehydration and freeze drying; refrigeration and freezing.

     Chemical: acids and esters.

• Physical means: acids and esters.

     Chemical: dehydration and freeze drying; refrigeration and freezing.

Physical means: dehydration and freeze drying; refrigeration and freezing.

Chemical: acids and esters.

Explain why most bacteria cannot be eaten.

Most bacteria cannot be eaten due to the fact that their small cells contain high proportions of DNA and RNA (purine rich in particular). The high nucleic acid content can serve as a problem because nucleic acids contain purines which the human digestive system converts to uric acid leading to joint pain/gout.

True/False

True

Express the relationship between the reduction potential and ΔG.

In oxidation-reduction reactions, the ΔG values are proportional with the reduction potential (E). A positive value of E has a negative ΔG, meaning that gaining electrons yields energy; the reaction favors the formation of product. On the flip side, a negative value of E has a positive ΔG and energy is gained through losing electrons; the reaction favors the formation of reactant.

True/False

True

Compare and contrast fermentation and respiration; include substrates, products, mode of ATP production and ATP yield. Use one of these keys: fermentation; respiration.

They are similar because they both begin with a series of reactions, known as glycolysis, and they also both produce ATP for the cell to use. They are different because [A] doesn’t require oxygen and [B] does. Water molecules are not produced during [C] but are during [D]. [E] produces a net gain of 2 ATPs, while [F] produces a net gain of 32 ATPs.

[A] fermentation [B] respiration [C] fermentation [D] respiration [E] fermentation [F] respiration