Cell Membrane and Transport AP Biology

Phospholipids

Phosphate head, hydrophilic, fatty acid tails, hydrophobic, arranged as bilayer

Semi-permeable

Specific channels allow specific material across the membrane

Proteins within membranes

Nonpolar amino acids, hydrophobic, anchors proteins into membranes

Outer surface proteins

Polar amino acids hydrophobic, extends into extracellular fluid and into cytosol

Determines membranes specific functions

Proteins

Peripheral proteins

Loosely bound to surface of membrane

Integral proteins

Penetrate lipid bilayer, usually across whole membrane, transmembrane protein, channels

Glycolipids and glycoproteins

Lipids and proteins connected to carbs, play a roll in cell regulation, antigens: allows cells to recognize one another, rejection of foreign cells

Cell connections

Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact

Plasmodesmata

Channels allowing cytosol to pass between plant cells

Tight Junctions

Membranes of adjacent cells are fused, forming continuous belts around cells

Desmosomes/ anchoring junctions

Fasten cell membranes together into strong sheets, much like rivets

Gap Junctions/ communicating junctions

Provide cytoplasmic channels between adjacent cells

Diffusion

Movement from high to low concentration

Simple Diffusion

Move from high to low concentration ‘passive transport’ no energy needed

Facilitated Diffusion

Diffusion through protein channels, no energy needed

Active Transport

Cells may need to move molecules against the concentration gradient, protein pump, uses ATP

Bulk transport

Moving big materials in and out of the cell

Endocytosis

Bulk transport inside the cell, triggered by molecular signal

Exocytosis

Bulk transport outside of the cell

Phagocytosis

Cellular eating, fusing with lysosomes for digestion

Pinocytosis

Cellular drinking, non-specific process

Osmosis

The diffusion of water from high to low concentration through a semi-permeable membrane

Direction of osmosis is determined by comparing total….

Solute concentrations

Hypertonic

More solute, less water

Hypotonic

Less solute, more water

Isotonic

Equal solute, equal water

Animal cells in hypotonic solutions:

Lysed

Plant cells in hypotonic solutions

Turgid

Animal cells in isotonic solution

Normal

Plant cells in isotonic solutions

Flaccid

Animal cells in hypertonic solutions

Shriveled

Plant cells in hypertonic solutions

Plasmolyzed

Hypotonic

Cells gain water and can burst, high concentration of water around cell, freshwater, water moves in

Hypertonic

Saltwater, cells lose water, high concentration of water in cell, cell looses water and can die solution: take up water or pump out salt

Isotonic

Equal in and out of cell

Aquaproins

Water moves rapidly in and out of the cell, proves that there were water channels