Bacteria developed specialized membranes that could perform metabolic functions Photosynthesis and cellular respiration Oxygen revolution ( billion years ago) Led to the rise of eukaryotes

2.1 billion years ago Endosymbiosis and Genetic Annealing Resulted in cells with organelles Result – Bigger cells with membrane bound organelles

Selectively Permeable Phospholipid bilayer Held together by hydrophobic interactions 1 2 Function and Structure

Fluid structure with proteins embedded and/or attached Allows for movement within and across

Integral Proteins embedded in the membrane Peripheral Proteins loosely bound to the surface

Transport Enzymatic activity Signal Transduction Cell-cell recognition Important in embryo development Glycolipids and glycoproteins Ex. blood type determination (glyco-proteins)

Intercellular joining Attachment to cytoskeleton Give cell shape

Hydrophobic molecules (CO₂, O₂) move easily across Polar molecules (glucose, sugars, and water) pass slowly across

Passive Transport No input of energy Result of a concentration gradient Examples: diffusion and osmosis and facilitated diffusion 5

Active Transport Uses energy and transport proteins Moves solutes against concentration gradients. Example: Sodium Potassium Pump Maintains membrane potential

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Exocytosis: Vesicles fuses with PM and release contents Examples: excreting insulin, nerve cell releasing neurotransmitters. 7

PM pinches in and forms a vesicle Phagocytosis = cell eating Pinocytosis = cell drinking 8