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