Micro 1113 more practice questions

Which microbial groups are most likely to spoil refrigerated foods?

Any of these groups

Please select all of the foods and beverages from the list below that are produced by microbial fermentation.

Bread Yogurt/Cheese Beer/Wine Pickles

Why is the temperature of the canning process for acidic fruits and pickles not as high as that required for canning beans?

C. botulinum does not grow or produce toxin below pH 4.5, so it is not a danger in highly acidic foods.

What creates the air pockets in bread?

CO2, produced through fermentation by Saccharomyces cerevisiae.

What defines the safe temperature ranges for storage of foods?

Cessation of growth at low temperatures AND cell death at high temperature.

Plasmolysis

Collapse of a walled cell's cytoplasm due to a lack of water

trace elements

Copper, maganese, molybdenum, cobalt, zinc

You have a culture of bacteria in which cells are dying off at a constant rate. This culture is most likely in ______ phase.

Death

Erwinia species

Degrade pectin, cause soft rot of fruits and vegetables.

Please select all methods of food preservation from the list.

Drying Salt/sugar Lowering Ph Pasteurization

T/F: The cytoplasmic membrane is permeable to protons

False

T/F: The location of the photosynthetic pigments that form photosystems is the stroma of the chloroplast.

False

Alcaligenes species

Form a glycocalyx, spoiling raw milk.

Which of the following chemicals is/are suspected carcinogens?

Formaldehyde and Ethylene oxide

Why is an orange more likely to be spoiled by fungi than by bacteria?

Fruits are naturally more acidic than bacteria can tolerate, allowing acid-resistant fungi to grow without competition.

Major elements

Nitrogen, phosphorus, sulfur, carbon, oxygen, hydrogen, potassium, magnesium, calcium, and iron

You observe bacteria growing on the surface of a Petri dish of nutrient agar you left on the counter in your lab. You can be confident that your bacteria are NOT which of the following?

Obligate Anaerobes

Which of the following can be used to make drinking water safe? Check all that apply.

Ozone and halogens

______ is a brief heat treatment that reduces the number of spoilage organisms and destroys pathogens. It can be used on foods or inanimate objects.

Pasteurization

Bacillus and Clostridium species

Pathogens producing endospores that can survive cooking.

With ideal environmental factors, the reproduction rate of bacteria is

extremely rapid

A fermentation process known as ______ originated as a way of preserving vegetables such as cucumbers and cabbage.

pickling

Match the food product with the description of how it is produced.

refer to chart

At freezing temperatures, most bacteria

stop growing, but are not dead.

Storage temperature and atmosphere are both examples of ______ factors, or environmental conditions, that can affect growth of microbes in food.

extrinsic

E. coli cells die at temperatures below 6° C.

false

Lactic acid bacteria are obligate ______ that are responsible for the tart taste of yogurt, pickles, sharp cheeses, and some sausages.

fermenters

An enclosed compartment filled with an inert gas such as nitrogen would be most appropriate for growing ______.

obligate anaerobes

The main environmental factors that affect microorganism growth include chemical inhibitors, oxygen, pH, nutrients, moisture, and ______.

temperature

Production of vinegar from alcohol is carried out by oxidation via

the acetic acid bacteria—Acetobacter and Gluconobacter species.

The tart taste of yogurt, pickles, sharp cheeses, and some sausages is due to

the production of lactic acid as a by-product of fermentation in these foods by bacteria.

Why is ham (aw = 0.91) a common source of S. aureus food poisoning?

-S. aureus is adapted for growth on salty surface. -S. aureus can grow at aw 0.86 -there are few other competitive bacteria on ham.

phases of bacterial growth curve

1. lag phase 2. log phase 3. stationary phase 4. death phase

From which of the following would you be most likely to obtain a pure culture?

A streak growing on an agar slant.

Microbes that grow readily on the bench top or in a temperature-controlled incubator that is not sealed from the atmosphere in the room are ______.

Aerobes

oxygen requirements of bacteria

Aerobic - requires presence of oxygen Anaerobic - requires absence of oxygen Facultative - can grow with or without oxygen but prefers oxygen Microaerophilic - prefers less oxygen than the levels found in the atmosphere.

Which of the following cause foodborne intoxications?

S. aureus C. botulinum

When studying microbes, why is it important to separate mixed communities into individual pure cultures of the different species?

So we can understand the biochemical characteristics of one species without confusing it with another species.

Bacillus species

Spoil canned goods and may cause illness

During which stage of growth does cell division equal the rate of cell death?

Stationary phase

Which of the following describes stationary phase of a growth curve?

The number of cells dividing equals the number dying.

Acetobacter species

Transform ethanol to acetic acid, spoiling wine.

Plastoquinone is the primary electron acceptor for electrons leaving photosystem II.

True

T/F: Protons used to set up the proton motive force are generated as macromolecules like glucose are oxidized in the cell.

True

During the production of soy sauce, the initial several days-long step is necessary in order to

allow for production of fermentable sugars, peptides, and amino acids that the salt-tolerant microbes involved in the process can ferment to produce soy sauce.

Spoiled foods are

any foods that have undergone an undesirable change due to microbial growth.

A candle jar is typically used to grow ______.

capnophiles

1. What is oxidation? 2. Early in glycolysis, two phosphates are added to the glucose molecule. These phosphates come from 3. During glycolysis, a single 6-carbon molecule of glucose is converted to two 3-carbon pyruvate molecules. During the later steps in this process, how many molecules of ATP are generated? 4. The two 3-carbon molecules glucose is split into are converted through a series of steps into pyruvate. During these steps 5. After glycolysis, pyruvate can be converted into ______ under anaerobic conditions.

-The loss of electrons from a molecule. -breaking down ATP -4 -NAD+ is converted to NADH. -lactic acid

Select the reasons sugar or salt can be used for food preservation. Check all that apply.

-They may cause plasmolysis-They create a hypertonic environment-They dehydrate the bacterial cells

1. Glycolysis makes products that feed into 2. The two 3-carbon molecules that glucose is split into during glycolysis are converted through a series of steps ending in what 3-carbon molecule? 3. For each glucose molecule broken down by glycolysis, how many net ATP molecules are produced?

-electron transport chain, TCA cycle AND fermentation -Pyruvate -2

1. The terminal electron acceptor in aerobic respiration is ______.2. Glycolysis is the central metabolic pathway that involves the breakdown of ______.3. The energy released during the reactions of glycolysis is used to form ______.4. Cells prefer to use carbohydrates as energy sources because

-oxygen -glucose -adenosine triphosphate -they are such good donors of hydrogen and electrons

You have a culture of bacteria in which cells are actively expressing genes and synthesizing enzymes, but cells are not dividing. This culture is most likely in ______ phase.

Lag

During which phase of growth do researchers measure the generation time of a culture of bacteria?

Log

Aspergillus flavus

Mold on peanuts and grains that produces potent carcinogen aflatoxin.

Rhizopus and Penicillium species

Molds that can grow easily on fruits and breads.

During a one hour time period in a population of approximately a billion cells, ten cells divide, and a hundred thousand cells die. This pattern suggests the population is experiencing which phase of a growth curve?

Phase of prolonged decline

Lactic acid bacteria

Produce lactic acid by fermentation, souring milk.

Leuconostoc species

Produce lactic acid that spoils milk

microorganisms optimal growth temperatures

Psychrophile Psychrotroph Mesophile Thermophile Hyperthermophile

Please match the food type with the pathogen commonly associated with it.

Raw (unpasteurized) milk and cheese = Listeria monocytogenes Poultry, eggs, milk = Salmonella species Oysters = Vibrio vulnificus Rice, meat, vegetables = Bacillus cereus Low-acid canned food = Clostridium botulinum

Identify each of the important areas of the electromagnetic spectrum on the figure.

Refer to chart

Match each of the following methods for preservation of perishable products with its description.

Refer to chart for preservation

Please match the food preservation method with its description.

Refer to chart of food preservation method

Match the organisms with the characteristics that make them important in food spoilage.

Refer to food spoilage picture

Please match the microbe with the type of spoilage it causes.

Rhizopus and Penicillium species Erwinia species Acetobacter species Bacillus and Clostridium species Aspergillus flavus Lactic acid bacteria Alcaligenes species