detailed digestion of carbohydrates, fats, and protiens

cholesterol is not digested.

-absorbed as is

Chymotrypsin

-activates other protein enzymes as well as does the bulk of protein digestion

Metabolism

-all nutrients eventually end up within a cell where the next step in processing begins

Chylomicrons are filled with dietary fats and circulated throughout the body.

-before it reaches the blood it must first start in the lymphatic system -deposited in the blood at the thoracic duct

bile is released into the small intestine

-bile molecules surround fat droplets and pull them down into digestive liquids.

the oral cavity:

-chewing breaks up food particles. - salivary amylase in saliva begins to break lager starches into smaller starches called dextrins

the destination of lipids depends on the packaging

-chylomicrons deposit lipids (mainly triglycerides) into storage and eventually are recycled in the liver. -VLDL transports triglycerides mainly from the liver to system -LDL transports cholesterol mainly from the liver to system -HDL- collects lipids (mainly cholesterol) from system and brings it to the liver.

first step is emulsification of lipid droplets.

-digestive enzymes (lipase) are found in digestive liquids -fat must be made soluble in water for digestion to occur

once enough free monosaccharide are made available, the intestine begins uptake of each monosaccharide.

-glucose :active transport -fructose: facilitated diffusion -galactose: facilitated diffusion

once absorbed, the fate of each monosaccharide is different

-glucose is deposited into the blood , does not have to go to the liver first -fructose and galactose are sent via the portal vein to the liver where they are both converted into glucose (glucose is either used for energy, stored as glycogen, or converted to fats for storage )

the partially digested bolus is transported to the stomach via the esophagus.

-HCL denatures amylase and shuts off carbohydrate digestion

Enteropeptidase

-is released by the intestine and its role in digestion is to activate Trypsin

once lipids are emulsified...

-lipase begins to remove free fatty acids from triglycerides

another challenge is transport of lipids through the blood

-lipids are hydrophilic

lipids are packaged in structures called lipoprotiens

-made with phospholipids and proteins -act as a transport for lipids in the blood.

Trypsin

-once activated is responsible for the activation of Chymotrypsin

Lipid absorption:

-once digested, both the monoglyceride and the two free fatty acids are absorbed via passive diffusion -once absorption is complete the disassembled pieces of the triglyceride are put back together

Carbohydrate digestion

-the goal of carbohydrate digestion is to reduce starches and disaccarides into free monosaccharide. 1.all three monosaccharide are absorbed by the small intestine

Lipid digestion:

-the goal of lipid digestion is to reduce a triglyceride into monoglyceride and two free fatty acids (FFA) 1.do not completely disassemble macromolecule

Protein digestion:

-the major goal of protein digestion is to break polypeptides down to amino acids. 1. Absorbed as tripeptides, and single amino acids

Small intestine :

-the major site of carbohydrate digestion -pancreatic amylase is added to chyme and continues breaking down starches -disaccharides are broken down by specific enzymes secreted by the intestine: 1.sucrase: breaks down sucrose 2.lactase : breaks down lactose 3.maltase: breaks down maltoe

there are two types of carbohydrate digestion :

-the oral cavity -the small intestine there is no carbohydrate digestion in the stomach or the large intestine.

protein absorption :

-there are portals for: 1.tripeptides (3 amino acids) 2.dipeptides (2 amino acids ) 3. single amino acids -sent in the blood via portal vein to the liver.

carbs, fats, and proteins each take a different route to digestion

-ultimantley each are absorbed -each are sent into circulation to the prime destination (liver)

the major site for lipid digestion is the small intestine

-very little to no digestion in the oral cavity , the stomach or the large intestine

classified based on size and source of lipid it carries

1. chylomicrons: dietary fats 2. VLDL: de novo fats 3.LDL: remnant of VLDL 4.systemic fats

there are multiple enzymes involved in protein digestion:

1. Pepsin (stomach) 2.Enteropeptidase (intestine) 3. Trypsin (pancreas) 4.Chymotrypsin (pancreas) 5.Carboxypeptidase (intestine) -Digest all proteins in the small intestine

there are two major sites of protein digestion

1. the stomach 2.the small intestine -all proteins must be denatured before digested 1. HCL is secreted by the stomach to denature proteins

lipoproteins come in four major varieties :

1.chylomicrons 2.very low density lipoproteins 3.low density lipoproteins 4. high density lipoproteins

two factors contribute to the need for multiple enzymes :

1.protein enzymes must be activated because they come in an inactive form called zymogens 2.protein enzymes are specific for specific peptide bonds

breaks peptide bonds next to phenylalanine, tryosine, methionine, tryptophan, asparagine, and histidine only

Chymotrypsin