NEW BIO OH NO

Diapositiva 1

• Phospholipids:
• Form a thin, flexible sheet.
• Arranged in a bilayer.
• Polar, hydrophillic phosphate heads facing out towards water.
• Non-Polar, hydrophobic fatty acid tails facing each other in the middle of the bilayer.
• Hydrophobic layer acts as a barrier to most molecules, effectively isolating the 2 sides of the membrane.
• Different kinds of membranes can contain phospholipids with different fatty acids, affecting the strength and flexibility of the membrane.
• PROTEINS
• Take up about 50% of the mass of the membranes.
• Responsible for most of the membrane's properties.
• Hydrophillic amino acids in contact with water outside of membranes.
• Hydrophobic amino acids in contact with fatty acid chains inside the membrane.
• Allows them to slide around the membrane very quickly and collide with each other, but never flip from one side to the other.
• Float in the phospholipid sheet like icebergs.

Diapositiva 2

• Integral Proteins:
• Span from one side of the phospholipid bilayer to the other.
• Peripheral proteins: sit on one the surfaces.
• Functions:
• Transport Proteins:
• Most transport of small molecules across the membrane take place through integral proteins.
• This transport includes facilitated diffusion and active transport.
• Receptor proteins:
• Located on the outside of the cell membranes.
• Have a specific binding site where hormones or other chemicals can bind to form a hormone-receptor complex.
• This binding triggers other events in the cell membrane or inside the cell.
• Enzymes:
• Enzyme proteins catalyse reactions in the cytoplasm or outside the cell
• E.g. Maltase in the small intestine.
• Recognition Proteins:
• Glycoproteins often involved with cell recognition.
• E.g. A and B antigens on red blood cell membranes.

Diapositiva 3

• Structural Proteins
• Can be located on the :
• Inside surface of the cell membranes
• attached to the cytoskeleton

Diapositiva 4

• Cell surface membranes
• Surround cells. Partially permeable .Sometimes called the plasma membrane.