Weekly quiz questions

Question 1

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and is therefore abundant in liver cells?

Answer 1

Smooth ER

Question 2

The three stages of cell signalling are:

Answer 2

Reception, transduction and response.

Question 3

Why is the mitochondrion NOT classified as part of the endomembrane system?

Answer 3

It has its own DNA.

Question 4

You isolate a cellular structure and determine that it is composed of α-tubulin and β-tubulin. Based on this evidence, you correctly identify this structure as:

Answer 4

A microtubule.

Question 5

Which of the following macromolecules leave the nucleus of a eukaryotic cell through pores in the nuclear membrane?

Answer 5

mRNA

Question 6

Under which of the following conditions would you expect to find a cell with a predominance of free ribosomes?

Answer 6

A cell that is producing cytoplasmic enzymes.

Question 7

Which of the following is a function of a signal peptide?

Answer 7

To direct polypeptides into the ER.

Question 8

The evolution of eukaryotic cells most likely involved:

Answer 8

Endosymbiosis of an oxygen-using bacterium in a larger prokaryotic host cell—the endosymbiont evolved into mitochondria.

Question 9

Which of the following macromolecules enter the nucleus of a eukaryotic cell through pores in the nuclear membrane?

Answer 9

Ribosomal proteins

Question 10

In cells, signal amplification is most often achieved by:

Answer 10

A series (cascade) of enzymes.

Question 11

Which cell would be best for studying lysosomes?

Answer 11

Phagocytic white blood cell

Question 12

If a method were found that could cause the nuclear lamina to fall into disarray, what would you expect to be the most immediate consequence?

Answer 12

A change in the shape of the nucleus.

Question 13

When a protein is glycosylated, what happens to it?

Answer 13

Carbohydrate molecules (oligosaccharides) are added to the protein

Question 14

A _______ is a basic unit of a carbohydrate

Answer 14

monosaccharide

Question 15

How does a ‘scientific theory’ differ from a ‘scientific hypothesis’?

Answer 15

Theories are generally supported by a much greater body of evidence than a hypothesis

Question 16

A controlled experiment is one that

Answer 16

Tests experimental and control groups in parallel.

Question 17

When applying the process of science, what is tested directly?

Answer 17

A prediction

Question 18

A dehydration reaction typically produces:

Answer 18

Polymers

Question 19

What is a hypothesis?

Answer 19

A tentative explanation that can be tested and is falsifiable.

Question 20

Hydrophobic substances such as vegetable oil are:

Answer 20

Nonpolar substances that repel water molecules.

Question 21

What component of amino acid structure varies among different amino acids?

Answer 21

The components of the R group.

Question 22

Is glucose a polymer?

Answer 22

No

Question 23

Polysaccharides, triacylglycerides, and proteins are similar in that they:

Answer 23

are synthesized from subunits by dehydration reactions.

Question 24

At which level of protein structure are interactions between the side chains (R groups) of amino acids most important?

Answer 24

Tertiary

Question 25

Folded biological macromolecules have specific conformations because

Answer 25

Weak interactions bring different parts of the molecule together.

Question 26

Why do the components of the cell membrane assemble the way they do around the contents of the cell?

Answer 26

The hydrophobic portion must be facing the inside of the phospholipid bilayer because these parts of the membrane cannot interact with water.

Question 27

What kinds of molecules pass through a cell membrane most easily?

Answer 27

Small and hydrophobic

This is because small nonpolar molecules are soluble in the lipid bilayer, and therefore can readily cross cell membranes. They can diffuse through membranes, while large uncharged polar molecules cannot.

Question 28

A new DNA strand elongates only in the 5’ to 3’ direction because:

Answer 28

DNA polymerase can only add nucleotides to the free 3’ end.

Question 29

What is meant by the description “antiparallel” regarding the two strands that make up the DNA double helix?

Answer 29

The 5’ to 3’ direction of one strand runs opposite to the 5’ to 3’ direction of the other strand.

Question 30

Homo sapiens have 23 pairs of chromosomes. This implies that ________.

Answer 30

46 double-stranded DNA molecules are present in each somatic cell

Question 31

In E. coli, there is a mutation in a gene called dnaB that prevents activity of the helicase that normally acts at the origin of replication. What would you expect to happen?

Answer 31

No replication fork will be formed.

Question 32

During which phase of mitosis do the chromatids become chromosomes?

Answer 32

Anaphase.

This is because the sister chromatids are separated from each other, and are pulled to opposite ends of the cell. This results in two chromosomes from the sister chromatid.

Question 33

E. coli cells grown on 15N medium (containing a ‘high-density’ isotope of nitrogen) are transferred to 14N medium (containing a ‘lower-density’ isotope of nitrogen) and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

Question 34

What is a karyotype?

Answer 34

Organised images of a cell’s chromosomes in mitosis.

Question 35

In E. coli, which enzyme catalyses the elongation of a new DNA strand in the 5’ → 3’ direction?

Answer 35

DNA polymerase III

Question 36

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely ________.

Answer 36

A plant cell in the process of cytokinesis.

Question 37

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?

Answer 37

Attachment of microtubules to kinetochores.

The microtubules form and grow in the cytosol, and the chromosomes they need to attach to are in the nucleus.

Question 38

Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with

Answer 38

Two nuclei.

Question 39

A group of cells is assayed for DNA content immediately following mitosis and cytokinesis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms of DNA would be found at the end of the S and G2 phases respectively?

Answer 39

16; 16

Question 40

A cleavage furrow is ________.

Answer 40

A groove in the plasma membrane between daughter nuclei.

Question 41

What is a genome?

Answer 41

The complete set of an organism’s genes and other DNA sequences

Question 42

Which of the following events occurs during interphase of the cell cycle?

Answer 42

Replication of the DNA

Question 43

In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis?

Question 44

What is the most critical characteristic for the association between histones and DNA

Answer 44

Histones are positively charged.

Histones are essential for chromosome packing because the DNA backbone is negatively charged and would resist packing if these charges were not able to be neutralised some of the time.

Question 45

In a nucleosome, the DNA is wrapped around

Answer 45

Histones