Microbiology Chapter 5 Homework

A broth medium has been inoculated, and microbial numbers will be counted periodically to generate a bacterial growth curve. At 2 hours after inoculation, the culture has progressed through lag phase and is now in log phase. At this point, the population size is 1 million cells. The generation time is 30 minutes. Assuming the continuation of log growth, how many cells would there be at 2 hours of growth in log phase?

16 million

Put the following steps of bacterial replication in the correct order, starting from a parent cell.Cell elongationSeptum formationChromosome replicationSeparation of daughter cells

3, 1, 2, 4

Which of the following equations represents photosynthesis?

6CO2 + 6H2O → C6H12O6 + 6O2 Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.

What two molecules are produced by the light reactions and used to power the Calvin cycle?

ATP and NADPH

What is the correct general equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy

What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?

Carbon dioxide (CO2) Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. This is why plants need to take in carbon dioxide.

Why might some cells uncouple the electron transport chain?

Cells can use the energy from the proton gradient for functions other than producing ATP, such as heat generation.

A chemostat is continuous culture system that is designed to promote and prolong exponential growth and prevent bacteria from entering stationary phase. How might this work?

Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells.

In which of the following organelles does photosynthesis take place?

Chloroplast

Which of the following statements regarding competitive inhibitors is true? Which of the following statements regarding competitive inhibitors is true?

Competitive inhibitors decrease the rate of enzyme activity.

What enables competitive inhibitors to bind to a specific enzyme?

Competitive inhibitors have structures that resemble the enzyme's substrate.

How does cyanide poisoning result in the decrease of ATP production?

Cyanide permanently reduces cytochrome a3, preventing other components to change into the oxidized state. This causes the proton gradient to break down, stopping ATP synthesis.

Why do all enzymatic reactions need activation energy?

Energy is required to disrupt a substrate's stable electron configuration.

Why are enzymes important to biological systems?

Enzymes decrease the amount of activation energy required for chemical reactions to occur.

What is meant by the statement "Enzymes are biological catalysts"?

Enzymes speed up the chemical reactions in living cells.

What provides electrons for the light reactions?

H20 Electrons are stripped from water in the light reactions of photosynthesis. This is one of the reasons plants need water.

After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase.

Harmful waste products may be accumulating. The cells are likely running out of nutrients. The number of cells that are dying is balanced by the number of new cells that are being formed.

What transports electrons from the light reactions to the Calvin cycle?

NADPH NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle.

How long does it take for the daughter cells from one round of replication to replicate themselves?

No time is required -- they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.

When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately?

The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes.

Why does lack of oxygen result in the halt of ATP synthesis?

The chain shuts down and can no longer pump hydrogen ions across the membrane, and the proton gradient cannot be maintained.

What enables the copied chromosomes to separate during binary fission?

The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes.

If high amounts of sulfanilamide are in the presence of an enzyme whose substrate is PABA, what outcome is expected?

The enzyme will stop functioning.

Which statement describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration. In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs.

What would happen if the septum did not form during binary fission?

The parent cell would now have two copies of the chromosome.

How does a competitive inhibitor slow enzyme catalysis?

They compete with the substrate for the enzyme's active site.

Which statement describes the citric acid cycle?

This process produces some ATP and carbon dioxide in the mitochondrion. The citric acid cycle breaks down carbon molecules, releasing carbon dioxide and forming some ATP.

Which statement describes glycolysis?

This process splits glucose in half and produces 2 ATPs for each glucose.

Starting with three cells, how many cells would result from three rounds of replication?

Twenty-four

Bacterial growth curves typically can be divided into four distinct phases: lag phase, log phase, stationary phase, and death phase. Drag the following descriptions to the appropriate location on the bacterial growth curve.

You have correctly labeled the bacterial growth curve, including the axes and the four phases: lag, log, stationary, and death phases. Keep in mind that some microorganisms may still be viable at the end of death phase. Surviving bacteria, even just one bacterium, may begin to divide and restore the population if conditions for growth become favorable again

Where would you expect to find electron transport chains in a prokaryote?

along the plasma membrane

What connects the two photosystems in the light reactions?

an electron transport chain

The reactions involved in producing larger compounds from smaller compounds is called

anabolism

Where does the energy required for anabolic reactions come from?

catabolic reactions

The process of generating ATP using a proton gradient is referred to as

chemiosmosis.

Which of the following processes takes place in the cytosol of a eukaryotic cell?

glycolysis

Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.

glycolysis → acetyl CoA → citric acid cycle → electron transport chain Glycolysis produces pyruvic acid, which enters the mitochondrion. There, it is converted to acetyl CoA, which enters the citric acid cycle. Electron carriers bring electrons from the first three steps to the electron transport chain, and ATP is made.

The use of amino acids to make proteins

is an example of anabolism.

In metabolism, energy that is not used

is given off as heat.

In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?

mitochondrion

This activity asks you to consider various methods of counting or estimating the size of bacterial populations and to select the method that will provide the most accurate data for plotting a bacterial growth curve. Which of the following methods would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases?

plate count A plate count will provide the number of living cells. These data are most appropriate for generating a plot of a bacterial growth curve.

The light reactions take place in the _________ and the Calvin cycle takes place in the _________.

thylakoids; stroma

Which of the following situations does not result in a breakdown of the proton gradient?

uncoupling proteins