AP Biology BELL RINGER [3 Minutes] Mark New Vocabulary: K, S, H, or D Write a sentence using 1 AWL Word (Consume, Classify, Concise, or Distinct)

AP Biology MYP Biology: The Cell Membrane

What are the functions of the cell membrane? The cell membrane controls what goes in and out of the cell and helps the cell to maintain homeostasis. The membrane also helps the cell maintain its shape and protects the cell.

What are phospholipids? Phospholipids are molecules with a polar phosphate ‘head’ and two nonpolar fatty acid tails.

Why do phospholipid bilayers form? The polar heads of the phospholipids face outwards to be near polar water molecules (they are hydrophilic). The nonpolar tails of the phospholipids, which do not like to be near water molecules, face within the bilayer (they are hydrophobic).

AP Biology Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads

Label the cell membrane structure Protein Receptor Phospholipids Protein Channel Cholesterol

What are the functions of the parts of the cell membrane? Membrane PartFunction Phospholipids Makes up the basic bilayer structure of the membrane Cholesterol Within the bilayer; gives structure to fluid membrane Protein Channel Helps molecules pass through the membrane Protein Receptor Sends and receives signals to and from other cells

Why is the cell membrane called a “fluid mosaic?” The cell membrane is often described as a fluid mosaic since it is made up of many different molecules and it is flexible, not rigid.

AP Biology What does it mean that the membrane is selectively-permeable? The cell membrane being selectively-permeable means that it allows some types of molecules to pass in and out of the cell space, but not others.

What factors determine how a molecule will cross the membrane? Size Charge / Polarity Concentration Small, nonpolar molecules can pass through the membrane without assistance if they are moving from high to low areas of concentration. All other types of particles need some sort of assistance, such as a protein channel in order to pass across the cell membrane.

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