A concise and clear overview of the key concepts covered in chapter 5. These notes make biology easy to understand and are a good place to start your revision and boost your grades.
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PLASMA MEMBRANES
CHAPTER 5
Membrane purpose
• Selective permeability
• Separating cells and organelles from
outside environment - Lysosome
compartmentalisation pH 4.5-4.8 Cytoplasm
• Separating the organelles from the pH 7.2
cytoplasm
• Cell recognition and cell signalling
• Regulating transport of materials in and
out of cells
Parts of a plasma membrane
• Phospholipids: hydrophilic heads face out,
hydrophobic tails face in
• Glycoprotein: contain a carbohydrate
(sugar) chain, branch off intrinsic proteins
• Glycolipid: phospholipids with carbohydrate
(sugar) chain attached
• Cholesterol: lipid with hydrophobic end so
embeds between tails
• Extrinsic protein: protein lying on the surface
of the membrane
• Intrinsic protein: Protein spanning the
phospholipid bilayer
Glycoproteins
• Involved in…
• Cell adhesion (joining cells to form
Phospholipids tissues)
• Bilayer is formed as cells are aqueous • Form H bonds with H2O molecules
• Described as FLUID MOSAIC because they are surrounding the cell and thus help
flexible — no bonds between phospholipids stabilise membrane structure
and mosaic due to random positions of • Receptors for cell signalling - peptide
proteins hormones and neurotransmitters
• Phospholipids don’t move due to polarity • Antigens for self recognition by the
• Membrane is 7-10nm thick immune system
•Intrinsic protein
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