Protein Secretion

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Protein Secretion

Higher Biology

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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

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Golgi Apparatus

Group of flattened fluid-filled sacs

Vesicles containing newly synthesised protein pinched off from rough ER

Fuse with outermost sac of Golgi apparatus

Protein passed from sac to sac by means of vesicles

Golgi apparatus processes protein

-e.g. adds a carbohydrate

-form a glycoprotein

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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

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Protein Secretion

Golgi bodies especially numerous and active in secretory cells

-gastric gland cells in stomach walls

-mucus

-pepsin

-pancreas

-insulin

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Elements in a protein

Carbon

Hydrogen

Oxgen

Nitrogen

(sulphur)

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Structure of a protein

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Quaternary structure of proteins

3 different types

-fibrous proteins

-globular proteins

-conjugated proteins

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Fibrous proteins

Several spiral-shaped polypeptide molecules

Linked in parallel by disulphide bridges

Protein has a rope-like structure

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Globular proteins

Several polypeptide chains

folded roughly into a spherical shape like a tangled ball of string

Enzymes are globular proteins