F4 Biology teaching notes Ch 5: NE 19

NE 19

http://biology-animations.blogspot.com/2009/08/protein-structure-animation.html (animation: protein structure)

l  Our body needs 20 types of amino acids to build up various proteins. The amino acids can be classified into:

(66) Non-essential amino acids (非必需氨基酸)	(67) Essential amino acids (必需氨基酸)
can be produced by our body	have to be obtained from the diet

l  Food source: meat, fish, eggs, beans, milk and other dairy product

l  Functions:

n  important component of cell (68)membrane / proteins for:

² growth

² (69) repair

of body tissues.

n  Amino acids are broken down to release (70) energy if the carbohydrates and lipids stored in the body are used up.

n  formation of:                                                             

² functional molecules (功能分子) such as enzymes, haemoglobin, (71) antibodies (抗體) and some hormones (激素)

² structural molecules (結構分子) like collagen (膠原蛋白)

l  Fate of excess proteins:

n  excess amino acids cannot be stored in body but are broken down in the liver by

(72) deamination (脫氨):                                                    

² the removed amino group forms (73)urea which is excreted with urine (尿液)

² the remained parts form carbohydrates and are broken down to release energy in the metabolic pathway of respiration                    

l  A deficiency of protein may lead to (74) kwashiorkor (蛋白缺乏症)