Topic 1: Cell biology 
This page contains multiple choice questions in the style of Paper 1 of the Biology exams.
They test the breadth of your knowledge of the understandings and skills about cell biology.
To spend more time reviewing the topic before answering these questions, use the revision resources.
Cell biology revision resources
This page lists the understandings and skills expected for Topic 1 and links to the sub-topic pages which contain detailed revision notes, activities and past paper style questions. Great for revision.
Learn from any mistakes. Every question has an examiner's explanation that appears when you check your answers.
What is the best definition of endosymbiosis?
Endosymbiosis is where a cell engulfs another cell and it continues to live inside the cell.
The engulfed cell provides something for the host cell, and gets something in return. Both cells benefit.
During interphase of the cell cycle what happens to the DNA in the nucleus?
Under the microscope there is little change during interphase.
However interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm. (It is subdivided into G1, S, G2 phases of the cell cycle)
DNA replication occurs during the S-phase.
The image below shows two cells undergoing mitosis.
Which of the following correctly identifies the stage of mitosis for each of the cells?
Identification of the phase of mitosis is an important skill.
The position of the chromosomes gives the best clue.
In Prophase, they are spread around the cell, and double stranded.
In Metaphase, the chromosomes are lined up on the spindle equator.
In Anaphase, the chromosomes are moving to opposite poles of the cell.
In Telophase, the two groups of chromosomes are separate, sometimes with a nuclear membrane.
The microscope image shows cells in a tissue sample taken from a growth suspected of being cancerous.
What is the best estimate of the mitotic index of this tissue?
Assume that there are exactly 60 cells (for simplicity).
Skill: Determination of a mitotic index from a micrograph
There are 3 cells in stages of mitosis.
So the mitotic index = 3 divided by 60 cells total.
Keeping it simple = 1 / 20 or 0.05
The photograph is from an electron microscope image of a membranes.
Parallel dark lines are clearly seen.
In electron micrography, heavy metal stains are often used to enhance contrast. DNA and Proteins often show as dark areas because these molecules can attach to the stain.
Which of the following interpretations is most similar to the proposal of the Daveson-Danielli model of membranes?
Students are expected to know how to use evidence from electron microscopy to support an idea about membranes. One illustration of this is the proposal of the Davson-Danielli model.
Further evidence lead to the falsification of the Davson-Danielli model and the proposal of the fluid mozaic model.
The illustration shown below is of a protein (green) attached to a membrane.
What is the most likely function of this membrane protein?
This protein is found in the human liver, where the hormone adrenaline indirectly stimulates it to mobilise stored energy inside liver cells in the "fight or flight" response.
The fact that it is a transmembrane protein is essential for this function.
It is interesting to note that this protein is also secreted by Anthrax bacteria as a toxin.
It upsets the metabolism of host cells when it enters them.
Cell theory covers most, but not all cases.
Which one of these statements is an exception?
Exceptions to cell theory are : multinucleated striated muscle the giant single celled Acetabularia algae?
Also, organisms consisting of only one cell carry out all functions of life in that cell. e.g. Paramecium, Chlorella.
What is the importance of surface area to volume ratio to cells?
Surface area to volume ratio is important in the limitation of cell size. The lager the volume, the greater the need for materials which have to be exchanged over the surface of the cell.
Which of the following are methods by which molecules can move across membranes?
- Simple diffusion
- Facilitated diffusion
- Cytokinesis
- Active transport
There are actually four types of membrane transport which are required in DP Biology, Simple diffusion, facilitated diffusion, osmosis and active transport.
The diagram shows the transport of sodium ions across a membrane.
Which explanation gives the best description of the type of membrane transport shown?.
Facilitated diffusion does not require energy from ATP so this process is active transport. It can move sodium ions against the concentration gradient, but this is not always the case.
Which of the following are methods by which molecules can move across membranes?
I. Simple diffusion
II. Facilitated diffusion
III. Cytokinesis
IV. Active transport
There are actually four types of membrane transport which are required in DP Biology, Simple diffusion, facilitated diffusion, osmosis and active transport.
What best describes the organism in the light microscope image?
It is unicellular (one cell) and a eukaryote (has a nucleus) and not autotrophic.
Which organelle in a eukarytotic animal cell synthesises proteins for exocytosis?
The RER synthesises proteins for exocytosis.
The image is of a prokaryotic cell. Which feature defines the cell as prokaryotic?
The lack of a membrane bound nucleus (nucleoid) classifies a cell as prokaryotic.
The diagram is of a plasma membrane. Which label corresponds to the hydrophilic area of an amphipathic molecule?
Protein (5) has both hydrophilic and hydrophobic areas to act as an integral protein. The central channel is hydrophilic.
The image is a ribbon model of a channel protein. Where would this be found in a plasma membrane?
Channel proteins penetrate the membrane and have a central hydrophilic area (yellow in the diagram which is shown from above).
What tonicity should a saline drip have in comparison to human blood?
The saline drip must be isotonic to human blood to not cause water gain or loss from tissues.
Which organelles in a plant cell are believed to have originated as free-living prokaryotic cells?
Both the mitochondria and the chloroplast in plant cells are thought to have been free-living prokaryotes which evolved in a symbiotic relationship with a eukaryotic cell.
Which of the following is the best description of an organelle?
The "wrong" answers are correct statements but are distractors, not the best description.
Why is the cell component in the image regarded as an organelle?
The organelle is a cell component with a membane, the mitochondrion, it is adapted to aerobic respiration.
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