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Ontario Secondary (Grade 9-12) Biology — practice by topic

Browse 124 questions across 8 Biology topics. Choose what you want to revise, then open a question to check its answer and worked solution.

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Biology topics

Structure and Function of Plasma Membranes (62)Metabolism (56)Active Transport (1)Energy and Metabolism (1)Enzymes (1)Passive and Active Transport (1)Passive Transport (1)Tonicity (1)

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Who proposed the fluid mosaic model of the plasma membrane, and in what year?Read the answer and worked solution →What did transmission electron microscopy reveal about the core of the plasma membrane in the 1950s?Read the answer and worked solution →What is the reported thickness range of a plasma membrane?Read the answer and worked solution →A human red blood cell is about 8 micrometres wide. Roughly how many times wider is that than a plasma membrane?Read the answer and worked solution →

Worked practice questions

Who proposed the fluid mosaic model of the plasma membrane, and in what year?

  1. Singer and Nicolson, in 1972
  2. Davson and Danielli, in 1935
  3. Davson and Nicolson, in 1950
  4. Singer and Danielli, in 1915
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Correct answer: A. Singer and Nicolson, in 1972

1. The fluid mosaic model was put forward by S.J. Singer and Garth L. Nicolson in 1972. 2. It replaced an earlier model because it explained both the microscopic observations and the function of the membrane. 3. Hugh Davson and James Danielli proposed the earlier sandwich model in 1935, so that pairing and that date belong to the model being replaced. 4. The 1915 date marks the identification of the membrane's chemical components, not any model. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_

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What did transmission electron microscopy reveal about the core of the plasma membrane in the 1950s?

  1. That it carried branched sugar chains
  2. That it was a double, not a single, layer
  3. That it was rigid rather than fluid
  4. That it held no protein of any kind
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Correct answer: B. That it was a double, not a single, layer

1. Advances in microscopy in the 1950s, notably transmission electron microscopy, sharpened the view of the membrane core. 2. Researchers saw that the core consisted of a double layer rather than a single layer. 3. That observation is what the 1935 sandwich model could not account for, and it drove the search for a better model. 4. Sugar chains and membrane fluidity were established by other lines of evidence, and proteins are in fact a principal component. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_

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What is the reported thickness range of a plasma membrane?

  1. 5 to 10 micrometres
  2. 5 to 10 nanometres
  3. 50 to 100 nanometres
  4. 8 to 10 micrometres
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Correct answer: B. 5 to 10 nanometres

1. Plasma membranes range from 5 to 10 nm in thickness. 2. A nanometre is a thousand times smaller than a micrometre, so the micrometre versions of the same numbers are off by a factor of one thousand. 3. A human red blood cell is about 8 micrometres wide, roughly 1,000 times wider than a plasma membrane, which fixes the scale. 4. Because of that comparison, 8 to 10 micrometres describes a whole red blood cell rather than a membrane. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.1 Components and Structure_

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