Cell Biology

Help Questions

GRE › Cell Biology

Questions 1 - 10
1

Gram positive bacteria have                      cell wall(s) and Gram negative bacteria have                      cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

2

Gram positive bacteria have                      cell wall(s) and Gram negative bacteria have                      cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

3

Gram positive bacteria have                      cell wall(s) and Gram negative bacteria have                      cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

4

Gram positive bacteria have                      cell wall(s) and Gram negative bacteria have                      cell wall(s).

one . . . one

one . . . two

two . . . one

two . . . two

Explanation

Gram stain is a laboratory technique used to distinguish bacteria. Gram positive and Gram negative bacteria are distinguished based on their cell walls. Gram positive bacteria have a single thick cell wall (outside its cell membrane). Upon Gram staining, these bacteria will hold the Gram stain because of their thick cell wall. The Gram negative bacteria also have only one cell wall; however, it is a lot thinner and is sandwiched between two cell membranes. The thin nature of the cell wall makes it easier for the Gram stain to leak out of the bacterial cell.

5

In the Calvin cycle, carbon is reduced to ultimately form glucose. Where does this carbon come from?

Air

Soil

Sun

Water

Mineralized rock

Explanation

The carbon fixed in the Calvin cycle comes from the air in the form of . This carbon is reduced through the usage of NADPH and ATP, produced in the light reactions of photosynthesis, in order to make glucose.

The soil provides valuable water and mineral nutrients for the plant. The sun provides the energy necessary to drive photosynthesis. And pure water contains only hydrogen and oxygen. Lithotrophs utilize inorganic carbon, usually from rocks.

6

Proteins have many functions. Which of the following can be functions of proteins?

I. Enzymes

II. Transcriptional regulators

III. Structural proteins

IV. Hormones

I, II, III, and IV

I, III, and IV

I and II

I, II, and III

I, III, IV

Explanation

Proteins serve all of these functions and many more. Most enzymes are proteins, which help to catalyze spontaneous reactions. Ribozymes can also serve this function but are instead made out of RNA. Proteins can act as transcriptional regulators which can turn on or off gene transcription. Structural proteins, such as actin, can help to maintain the shape of a cell. Other small proteins, such as insulin, can act as hormones which can diffuse throughout the body relaying important messages.

7

Which phase of mitosis is characterized by the reappearance of the nuclear envelope?

Telophase

Metaphase

Prophase

Anaphase

Explanation

Once the cell has split and transported its sister chromatids to opposite ends of the cell, the nuclear envelopes can begin to regenerate around the genetic material at each pole. This event occurs during the end of mitosis, commonly known as telophase.

8

Which of the following is false with regard to the LDL-receptor?

Once bound to cargo, it enters the cell via COPII-mediated endocytosis

It is shuttled back to the cell surface after it delivers its cargo

It releases its cargo in the low pH environment of the endosome

Its cargo is low density lipoprotein

Explanation

The LDL-receptor enters the cell via clathrin-mediated endocytosis, not COPII. COPII is involved in budding off of the endoplasmic reticulum.

All of the other given answer options are true.

9

Fatty acids can vary in length. Which of the following fatty acids chains cannot not be synthesized in the human body?

A nineteen-carbon fatty acid chain

A twelve-carbon fatty acid chain

An eighteen-carbon fatty acid chain

A twenty-four-carbon fatty acid chain

A fourteen-carbon fatty acid chain

Explanation

Fatty acids synthesized in the human body always have an even number of carbon atoms usually between 12 and 28. Odd-numbered fatty acid chains will occasionally be found in plants and marine animals.

10

Plants such as corn are capable of C4 respiration. In order to undergo C4 respiration, which additional enzyme must the plant utilize?

PEP carboxylase

RUBISCO

Alkaline phosphatase

Kinase

Phosphofructokinase

Explanation

Plants that undergo C4 respiration must also utilize the enzyme PEP carboxylase. This enzyme allows for carbon dioxide to be fixed to PEP to produce oxaloacetate. C4 respiration allows for lower levels of photorespiration, which can cause a decrease in photosynthetic efficiency.

Rubisco is the enzyme that adds carbon dioxide to ribulose bisphosphate to produce two molecules of 3-phosphoglycerate. Alkaline phosphatase is an enzyme that hydrolyzes phosphates from a variety of substrates under alkaline conditions. Kinases are enzyme which add phosphate groups to specific targets, such as fructose-1-phosphate.

Page 1 of 74