Protein Secretion Higher Biology
Rough Endoplasmic Reticulum (rough ER) System of flattened sacs and tubules Encrusted with ribosomes on the outer surface if their membranes Continuous with outer nuclear membrane Provides a large surface area for chemical reactions Pathway for transport of materials
Golgi Apparatus Group of flattened fluid-filled sacs 1.Vesicles containing newly synthesised protein pinched off from rough ER 2.Fuse with outermost sac of Golgi apparatus 3.Protein passed from sac to sac by means of vesicles 4.Golgi apparatus processes protein -e.g. adds a carbohydrate -form a glycoprotein
Exocytosis Vesicles containing finished product -mucus -digestive enzyme -hormone Pinched off at end of Golgi apparatus Vesicles move towards cell membrane and fuse with it Contents of vesicle discharged to outside
Protein Secretion Golgi bodies especially numerous and active in secretory cells -gastric gland cells in stomach walls -mucus -pepsin -pancreas -insulin
Elements in a protein Carbon Hydrogen Oxgen Nitrogen (sulphur)
Structure of a protein
Quaternary structure of proteins 3 different types -fibrous proteins -globular proteins -conjugated proteins
Fibrous proteins Several spiral-shaped polypeptide molecules Linked in parallel by disulphide bridges Protein has a rope-like structure
Fibrous protein Structural property Tissue rich in this protein Function of this protein ElastinStrong and elastic Wall of large arteries Flexible support CollagenStrong and inelastic -Bone -Tendon and ligament -Rigid support -attachment KeratinStrong and inelastic HairProtection Actin and myosin contractilemusclemovement
Globular proteins Several polypeptide chains folded roughly into a spherical shape like a tangled ball of string Enzymes are globular proteins Also vital component in cell and sub- cellular membranes
Hormones Chemical messengers Globular protein Exert a specific effect on tissues
Antibodies Y-shaped globular proteins Made by lymphocytes Defend body against antigens
Conjugated proteins Globular protein associated with a non-protein chemical Glycoprotein -protein and carbohydrate -mucus
Haemoglobin Oxygen-transporting pigment in blood Conjugated protein -globular protein globin -haem (non-protein containing iron)
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