IB1 Biology mock test

More than 90 % of cellular cholesterol is located in the cell’s plasma membrane. What is the main role of cholesterol in the plasma membranes of mammalian cells?

• To regulate membrane fluidity

• To increase membrane solubility

• To increase membrane permeability

• To regulate membrane temperature

What is/are required for facilitated diffusion?

I. A concentration gradient

II. ATP

III. A channel protein

• I only

• I and III only

• II and III only

• I, II and III

Which cell component arose first during the formation of the earliest cells?

• Chloroplast

• Plasma membrane

• Mitochondria

• Cell wall

Pasteur used swan-necked flasks and a nutrient broth to demonstrate that spontaneous generation of organisms does not occur on Earth. Some students performed a similar experiment using two swan-necked flasks, one containing broth which had been previously boiled and another containing broth which had not been boiled. 

The flasks were left in the school laboratory and observed after one week. What is the evidence against the spontaneous generation theory?

• Microorganisms died in flask F due to high temperatures.

• No microorganisms grew in flask F but many grew in flask G.

• No microorganisms grew in either flask.

• Microorganisms grew in flask G.

The micrograph of a section through a plant stem shows at least ten different types of cells.

What explains the differences between these cells?

• Only one gene is expressed in each cell type.

• Different genes are expressed in each cell type.

• Only useful genes remain in the DNA of each cell type.

• Changes in the DNA sequence take place when these cells develop.

How do both mitochondria and chloroplasts provide evidence for the endosymbiotic theory?

• They have 80S ribosomes similar to prokaryotes.

• They contain the same DNA as the nucleus of the cell.

• They have double membranes.

• They exist together in eukaryote cells for their mutual benefit.

The graph shows the mitotic index in the roots of lentil plants at different distances from the end of the root.

What can be deduced from the graph?

• As the distance from the end of the root increases, more cells are undergoing mitosis.

• At 0.5 mm from the end of the root, most of the cells are in prophase.

• There were fewer cells observed at 1.5 mm than at 0.5 mm.

• As the distance from the end of the root increases, the percentage of cells in interphase increases.

The Davson–Danielli model of membrane structure proposed that membranes were composed of a phospholipid bilayer that lies between two layers of globular proteins, as shown in this diagram.

What evidence supported this model?

• An electron micrograph that showed two dark lines with a lighter band in between

• Freeze-fracture electron microscopy

• Evidence that all membranes are identical

• The hydrophobic regions of protein would be in contact with water

A human organ is being prepared for transplant. In what type of solution must it be bathed?

• A hypertonic solution

• A solution with the same osmolarity as the organ tissue

• A hypotonic solution

• Pure water containing no solutes

The electron micrograph shows a section through a cell.

Which feature of the cell in the micrograph is consistent with the endosymbiotic theory?

• X has a single membrane.

• Y has a double membrane.

• X contains 70S ribosomes.

• Y contains 80S ribosomes.