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