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Below is an essay on "Active Transport" from Anti Essays, your source for research papers, essays, and term paper examples.

Previous IB Exam Essay Questions: Unit 2
Biology IB HL 1
Previous IB Exam Essay Questions: Unit 2
Use these model essay question responses to prepare for essay questions on your in class tests, as well as the IB Examination, Paper 2. These questions have appeared on recent IB examinations, exactly as shown below. Following each question is the markscheme answer which was used to evaluate student answers on the examination paper.
1. Draw a diagram to show the structure of a cell membrane 5 marks
phospholipids labelled with hydrophillic (heads) and hydrophobic (tails)
phospholipid bilayer clearly shown and labelled
proteins shown in the bilayer and labelled
transmembrane and peripheral/extrinsic proteins shown and labelled
glycoproteins shown and labelled
cholesterol shown and labelled
glycolipids shown and labelled
thickness shown as 10 nm/ + or - 2 nm
2. Explain how the structure and properties of phospholipids help to maintain the structure of cell membranes. 9 marks

phospholipid structure

hydrophobic tail/hydrophilic head
head made from glycerol and phosphate
tail made from two fatty acids
saturated/ unsaturated fatty acid (in tail)
arrangement in membrane
phospholipids form a bilayer
heads face outside the membrane/ tails face inside the membrane/ hydrophic interior/ hydrophilic exterior of membrane
A suitable annotated diagram may incorporate all or many of the above points. Award 5 marks maximum for a suitable diagram that is labelled correctly.
phospholipids held together by hydrophobic interactions
phospholipid layers are stabilized by interaction of hydrophilic heads and surrounding water
phospholipids allow for membrane fluidity/ flexibility
fluidity/ flexibility helps membranes to be (functionally) stable
phospholipids with short fatty acids/ unsaturated fatty acids are more fluid
fluidity is important in breaking and remaking membranes (e.g. endocytosis/ exocytosis)
phospholipids can move about/ move horizontally/ "flip...

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Active Transport. Anti Essays. Retrieved April 21, 2019, from the World Wide Web: https://www.antiessays.com/free-essays/Active-Transport-761136.html