The Cell Membrane and Homeostasis
Jan 19, 2016
The Cell Membraneand Homeostasis
Homeostasis
Maintain an internal balance
Cells keep the proper concentration of nutrients and water inside and push wastes outside.
Living Barrier
The cell membrane is selectively permeable (or semi-permeable) allows some things to pass through, while blocking
others
Membrane Structure
Lipid bilayer – two sheets of lipids (phospholipids).
Found around The cell, the nucleus, vacuoles,
mitochondria, and chloroplasts.Embedded with proteinsStrengthened with cholesterol
molecules.
What’s a Phospholipid?It’s a pair of fatty acid chains and a
phosphate group. Polar (water-loving) phosphate heads face out nonpolar (water-hating) fatty acids hang inside.
Membrane ProteinsDetermine what particles can pass through
the membrane (gates).
Serve as enzymes(may speed reactions).
Act as markers for recognition(the immune system).
Fluid Mosaic Model
Transport Across the Membrane
No Energy
Passive transport – no energy is needed to move particles.
Types Diffusion Facilitated Diffusion Osmosis
Energy
Active Transport – energy is required to move particles
Types Carrier Proteins Endocytosis Exocytosis