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.
The image below was taken in 1825 and shows part of the cell cycle.
What type of cells is this and at which stage of the cell cycle?
Cytokinesis occurs after mitosis in plant and animal cells (cell, not nuclear division). The chromosomes are uncoiled.
Plant cells build a new cell wall which divides the cytoplasm.
Animal cells form a cleavage furrow (likes a wasps waist) as they don't have cell walls.
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.
Which one of the statements below best describes the mitotic index?
The mitotic shows the speed of cell division, which can be used as a tool to identify cancer.
It is calculated by dividing the number of cells doing mitosis by the total number of cells.
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).
There are 3 cells in stages of mitosis.
So the mitotic index = 3 divided by 60 cells total = 1 / 20 or 0.05
The graph below shows the % change in mass of carrot parenchyma slices at different concentrations of sucrose.
Which of the following is the best estimate of the molarity of the cytoplasm of these cells?
When a sample of cells show no change in mass, then the net movement of water by osmosis must be zero. This shows the concentration of the cytoplasm of the cells. In this graph it would be about 0.3 mol
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.
What is the term used to describe the smallest distance which two objects can be seen as separate objects in a microscope?
The resolving power, or resolution, is the ability to separate objects, to produce separate images of two objects.
The image below shows erythrocytes and leucocytes.l.
Using the scale bar and the ruler placed on the image, estimate the magnification of the image.
Which answer is the best estimate
Convert the ruler measurement to the same units written on the scale bar, in this case 25mm is 25000µm
Divide the ruler measurement of image size 25000 by the number on the scalebar, 25.
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 could be used to distinguish a living from a non- living object
Comment: Inanimate objects can move, produce and utilise energy but the process of respiration is exclusive to living systems
The diagram is of a plasma membrane. Which label corresponds to a protein channel?
Protein channels cross the membrane to allow hydrophilic substances to pass through the membrane.
The diagram is of a plasma membrane. Which label corresponds to the hydrophilic area of an amphipathic molecule?
Protein channel (2) has both hydrophilic and hydrophobic areas to act as an integral protein. The central channel is hydrophilic.
The microphotograph is of stratified epithelium. Cells are produced by mitosis in the area marked by the arrow and eventually reach the surface to replace lost cells. Which biological processes does this represent?
The cells produced by mitosis differentiate into mature cells and replace the cells lost at the surface.
The image is of a ion channel protein. What is the function of a membrane channel protein?
Channel proteins are used for facilitated diffusion down the concentration gradient.
Which means of transport across a plasma membrane requires the molecule shown in the picture?
Which property of stem cells is important for embryonic development?
Stem cells can divide and differentiate along different pathways. For a single fertilised egg cell to grow into an embryo both these processes are necessary.
Which of the following contributed to the acceptance of the fluid mosaic model of membrane structure of Singer and Nicholson in place of the original Davison-Danielli model?
I Hydrophobic membrane proteins
II Irregular sizes of membrane proteins
III Increased magnification of light microscopes.
IV Fluorescent antibody tagging.
The irregular sizes and insolubility of hydrophobic membrane proteins indicated that they could not be a surface layer as proposed by Davison-Danielli. This was confirmed by fluoresecent antibodies showing that proteins were both within and on the membrane.
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.
A tissue is placed in an isotonic bathing solution. Which of the following is the best description of water movement between the tissue and the bathing solution?
There is no net water movement, gain and loss from the tissue is equal in both directions.
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