Extended answers

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Expected extended questions answers – Unit 1

Unicellular and multicellular organisms

· Many different types of cells exist. Plants and animals can be either unicellular or multicellular. (1)

· Unicellular organisms are single cells. (1)

· All the functions of life are performed within a single cell. (1)

· Components within the cell are called organelles and perform the different functions. (1)

· An example of a unicellular organism is yeast. (1)

· Multicellular organisms are made of many different types of cells and function more efficiently than unicellular organisms. (1)

· They are organized into cells, tissues, organs and systems. (1)

· Each cell has a particular function. The structure of the cell is related to its function. (1)

· An example of structure and function of an animal cell or tissue is skeletal muscle cells are involved in contraction and contain lots of protein fibers’. (1)

· An example of structure and function of a plant cell or tissue is xylem cells are hollow and transport water - lignin adds strength for support. (1)

ATP production


o Glycolysis is an anaerobic process that occurs in the cytoplasm. (1)

o Glucose (6C) is split into two molecules of pyruvic acid (2 x 3C). (1)

o The NADH2 is available for ATP production in the final stage of cellular respiration. (1)


o The Krebs cycle is an aerobic process that occurs in the matrix of the mitochondrion. (1)

o Pyruvic acid (3C) is initially converted to acetyl CoA (2C), with the release of CO2. (1)

o In the process, both carbon (in the form of carbon dioxide) and hydrogen are released. (1)

o Hydrogen becomes bound to NAD to form NADH2. This will be used in the next stage of respiration for ATP production. (1)


o Hydrogen transfer through the cytochrome system is an aerobic process and occurs on the surface of the cristae of the mitochondrion. (1)

o The hydrogen from NADH2 is transferred to the cytochrome system where energy is released and used in the production of ATP (oxidative phosphorylation). (1)

o Three molecules of ATP are made from each molecule of NADH2. (1)

o Oxygen is the final


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