Macronutrient Digestion and Absorption Review II

fats functions

component in cell walls, source of energy, absorbing fat soluble vitamins (K, E, D, and A), insulate body, make steroid hormones

oral cavity

chewing breaks food up, saliva containing lingual lipase saturates bolus, dietary lipids are generally not water soluble

stomach

chyme mixing in stomach forms large lipid drops, lingual lipase breaks down triglycerides

micelles

transport fat digestion products to intestinal cells for absorption

intestinal cells synthesize

new triglycerides from monoglycerides, fatty acids, and glycerol

chlymoicrons

triglycerides combine w/ absorbed cholesterol, phospholipids, and lipid soluble maters, coated w/ proteins; lipoproteins that contain insoluble lipids

chlymicorns diffuse

into intestinal lacteals

lipids diffuse

across plasma membrane and enter cytosol when a micelle contracts the intestinal epithelium

intestinal cells synthesize new triglycerides

from monoglycerides, fatty acids, and glycerol

chylomicrons broken down

into triglycerides by lipoprotein lipase or transported into liver

triglycerides

diffuse into tissues and are stored in adipose cells or used by muscles for energy

LDL

formed by chylomicrons in liver; carry cholesterol to tissues

released cholesterol

can be used to make steroid hormones; for energy; or form plaques and clog blood vessels

excess cholesterol

carried back to liver to be recycled or excreted in bile by binding to high density lipoproteins (HDL)

having more HDL and less LDL

optimal for cholesterol health

body functions protein is essential for

tissue structure, hormone structure, metabolic structure, transport system, enzymes that regulate metabolism, balancing pH

amino acid subunits

compose proteins

first step of protein breakdown

begins in mouth thru chewing and mixing w/ saliva; mechanical processing continues in stomach thru churning and mixture

stomach environment

acidic environment kills pathogens and breaks down connective tissues and plant cell walls

stomach acid

denatures proteins, disrupting tertiary and secondary structures, which expose peptide bonds for enzymatic action

chief cells

secrete pepsinogen, an inactive proenzyme

HCl

converts pepsinogen to pepsin

pepsin

breaks down complex proteins into smaller peptide and polypeptide chains

release of pancreatic enzymes

released by CCK triggered by acidic chyme in duodenum

enteropeptidase

enzyme from duodenal epithelium that converts trypsinogen to trypsin

trypsin

converts proenzymes to chymotrypsin, carboxypeptidase, and elastase to break down proteins

each enzyme

targets specific peptide bonds

epithelial surfaces in small intestine

contain peptidases, including dipeptidases

dipeptidases

break dipeptides into individual amino acids

amino acids in liver

used to synthesize needed proteins

amino acids leave liver

to go throughout the body and be used for protein synthesis

when glucose levels are deficients

amino acids can be used in gluconeogenesis in liver