BIOC192 Lecture 23 - Metabolism: Digestion of Food Molecules Flashcards
what are the main macronutrients contributing to the energy production in. the body?
- carbohydrates
- proteins
- fats
- nucleic acids
what are carbohydrates broken down into?
monosaccharides
what are proteins broken down into?
amino acids
what are nucleic acids broken down into?
nucleotides
what are fats broken down into?
FFAs, MAG, and cholesteral
what do salivary glands contain and what do they start?
saliva (neutral pH) contains mucous and amylase which starts the digestion of carbohydrates
what 3 things does the stomach secrete?
1) secretes acid (0.1 M of HCI) causing denaturing
2) secretes pepsinogen –> pepsin causing protein digestion
3) secretes mucous layer for protection against the acids conditions
what does the liver secrete?
secretes most digestive enzymes including amylase, lipase and several proteases
what does the liver synthesis and what is this important for?
synthesis of bile salts/acids (stored in the gall bladder) that is important for fat digestion
where is the final phase of digestion and absorption?
the small intestine
what are the two main phases of digestion?
1) hydrolysis of bonds connecting monomer units in food macromolecules
2) absorption of products from GI tract?
what occurs during the hydrolysis of bonds connecting monomer units in food macromolecules?
1) carbohydrates: glycosidic bonds - starch –> disaccharides
2) proteins: peptide bonds
3) fat: triacylglycerol ester bonds
how many percent of energy intake does the digestion of dietary carbohydrates provide?
40-50%
what are the 3 dietary carbohydrates?
1) starch
2) simple sugars i.e sucrose, lactose, fructose, glucose
3) fibre i.e cellulose
what is the main component of plant starch?
amylopectin
what is the relationship between the functional groups in monosaccharides and orientation?
the functional group in monosaccharides can be in either of 2 orientations
what are the 6 enzymes involved in carbohydrate digestion?
1) salivary amylase
2) pancreatic amylase
3) maltase
4) lactase
5) sucrase
6) isomaltase
what is amylose?
a linear polymer of alpha (1->4) liked glucose units
what is amylopectin?
a branched polymer of alpha (1->4) and alpha (1->6) linked glucose units
what has a similar branched structure to amylopectin?
glycogen
where can glycogen be present?
can be present in consumer foods such as liver and muscle
what occurs during the hydrolysis of starch?
- starch digestion is when the enzyme amylase hydrolyses alpha (1->4) glycosidic bonds
the repeated internal attack yielding smaller and smaller oligosaccharides producing maltose/isomaltose disaccharides as end products
what does the digestion of dietary protein supply?
supplies amino acids to make body proteins
what is the digestion of dietary fibre a source of?
source of nitrogen for purines, pyrimidines and haem
what are the 8 essential amino acids required for the human body that are acquired from the environment?
1) leucine
2) lysine
3) threonine
4) tryptophan
5) isoleucine
6) methionine
7)
phenylalanine
8) valine
what form are all proteases in the human body secreted as?
secreted as inactive forms (zymogens or proenzymes)
how are all proteases in the human body activated by?
activated by the cleavage of peptides from their structure
how is protease specificity determined?
determined by adjacent amino acid side chains
what are the 2 types of peptidases involved in protein digestion?
1) endopeptidase
2) exopeptidase
what is the function of endopeptidases?
attack peptide bonds WITHIN the protein (peptide) polymer
what is the function of exopeptidases?
attack peptide bonds at the end of the protein (peptide) polymer
how is pepsinogen activated to pepsin?
pepsinogen, the inactive zymogen (proenzyme) is activated to pepsin following the exposure of pepsinogen to HCI in the stomach
-in the acidic stomach environment, part of the pepsinogen protein unfolds, which activates the pepsin protease and results in hydrolysis of part of the pepsinogen protein sequence to generate a stably activated pepsin protease
