Cell Structure - Membranes

Cell Structure - Membranes

Cell Membranes Cell and organelle membranes are made of two layers - lipid bilayers. Cell membranes are

semipermeable- acts like a screen by letting some chemicals in & stopping others.

It is like the doors of the cell. Passive Transport The random movement of particles from a greater to a lesser concentration. Uses no energy.

Three types: Diffusion Osmosis Facilitated diffusion Diffusion

The random movement of particles from a greater to a lesser concentration.. Uses no energy. A molecule will slide through the membrane only if it will fit. Simple Diffusion.

Things just naturally want to spread out. That is what these red particle are doing. They Are DIFFUSING. The red particle and the blue particles are diffusing in this picture. They have to cross a permeable membrane to do it.

Osmosis Osmosis is the diffusion of water. In this case, the membrane is SEMI-permeable. Only the small particles (the water) can get through. When only water diffuses, it is called OSMOSIS.

Facilitated Diffusion The molecules that are too big to get through the membrane use proteins. Requires no energy! There are different types of proteins: carrier and channel

A big molecule can use a CHANNEL PROTEIN to get through. CARRIER PROTEIN are shaped just like specific molecules.

They grab molecules, suck them in, and spit them out on the other side of the membrane. This uses no energy. Glucose molecules

To review Simple Diffusion, Osmosis, and Facilitated Diffusion 1. Use no energy (Passive Transport) 2. Move particles from greater to a lesser concentration

But what if you want to concentrate a chemical on one side of a membrane? Active Transport A process that requires energy Proteins move molecules across the membrane from

lesser to greater concentration. Except for the above two points, it is the same as facilitated diffusion. 2 Types: Molecular transport Bulk transport Endocytosis

Exocytosis ACTIVE TRANSPORT! Active Transport is ACTIVE. It uses energy. Ex. Sodium Pump and minerals entering root cells

Molecular Transport: occurs when small molecules are carried across the membranes by pumps made of proteins. This is an example of Molecular Transport

Bulk Transport Movement of large molecule or clumps of material by movement of the cell membrane. Two main types: Endocytosis

exocytisis Endocytosis process of taking material into the cell by infoldings or pockets of the

cell membrane A specific type of endocytosis is phagocytosis (cell eating) During phagocytosis, extensions of cytoplasm surround the particle and package it to a food vacuole. The cell engulfs it!

Exocytosis Larger molecules are released by the cell in a process called exocytosis. the membrane of the vacuole surrounding the

material fuses with the cell membrane forcing out its contents. Other terms to know about: Hypotonic

Isotonic Hypertonic Isotonic: Concentration of solutes(molecules) is the same inside and out of the cell. Water moves equally in and out of cell. Equilibrium

Hypertonic: Solution has higher solute concentration than the cell. Water moves out of cell. Hypotonic: Solution has lower solute concentration than the cell. Water moves into

cell.

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