Contains answers to all LAQs from IB Biology HL past papers from May 2016 to November 2022 for topic 6: human physiology. All checked with respective markschemes and written out as marked bullet points.
Humans rely on carbohydrates for much of their energy. Outline the process of digestion and
absorption of starch in the human digestive system. [4]
− Starch digestion begins in the mouth in the presence of amylase which breaks down the
starch into maltose
− There is also amylase in the small intestine, where starch continues to be broken down
− Maltose is then broken down by maltase into glucose in the small intestine
− Glucose is absorbed in the small intestine
− Villi increases the surface area of the intestinal epithelium for greater absorption
Describe the genetic and hormonal control of male sexual characteristics in a human. [3]
− Male sexual characteristics are coded for by the SRY gene which is present for male babies
during embryonic development
− The SRY gene codes for DNA binding protein TDF, leading to the expression of other genes,
therefore causing testes development
− Testosterone also triggers the formation of secondary sexual characteristics at puberty
Compare and contrast hormonal and nervous communication.[7]
− Both used for communication between cells
− Both controlled by the brain
− Both use feedback mechanisms
Hormonal Nervous
Slower Faster
Chemical Electrical
Long term Short term
Transported in blood Transported in neurons
Explain the production of antibodies in humans. [7]
− Pathogens are ingested by macrophages
− The pathogen’s antigens are displayed on the macrophage’s surface
− T lymphocytes with the specific protein receptor bind to these antigens
− T lymphocyte is activated
− It can then bind to B lymphocytes with the complementary receptor
− The B lymphocytes divide to form plasma cells and memory cells
− Plasma cells secrete antibodies to form immune response
− Memory cells are stored in case of secondary infection
Outline how proteins are digested and the products of protein digestion absorbed in humans. [4
marks]
− Proteins can be broken down by protease
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