Nutrient digestion Flashcards
Which two monosaccharides make up lactose?
Glucose
Galactose
Which two monosaccharides make up sucrose?
Glucose
Fructose
Which two monosaccharides make up maltose?
Glucose
Glucose
What are the two components of starch?
Alpha amylose
Amylopectin
Describe the structure of Alpha amylose.
Straight chain
a1-4 glycosidic bonds
Describe the structure of amylopectin.
Highly branched
a1-6 glycosidic bonds link the a-amylose chains
Describe the structure of cellulose.
Straight chain glucose polymers
Unbranched
How is cellulose digested?
Must be digested by bacteria as cellulase is not expressed in animals
Describe the surface structure of the small intestine.
Covered in villi
Columnar epithelial cells
Apical membrane gives increased surface area for absorption
What is a challenge of transporting across the small intestine wall?
Trans-epithelial transport
Must get through both the apical and the basal-lateral membrane
What is the function of the SGLT1 transporter?
Uses Na+ gradient created by Na/K-ATPase to transport glucose against concentration gradient
What is the function of the GLUT-2 transporter
Works in the basal-lateral membrane to move glucose into blood
What is the function of the GLUT-5 transporter?
Transports fructose in the small intestine
What is the difference between endopeptidases and exopeptidases?
Endopeptidases work on interior of peptide chain
Exopeptidases only work on terminal peptides
How are amino acids transported?
Uses Na+ gradient created by Na/K pump to transport amino acid against concentration gradient
How are dipeptides transported?
Sodium hydrogen pumps Na in and pumps H out
PepT1 uses H gradient to bring in dipeptide
What is the primary source of fat digestion in children?
Lingual lipase (fat soluble)
What is the primary source of fat digestion in adults?
Pancreatic lipase (water soluble) Since pancreatic lipase is not fat soluble it can only act on the outside of the molecule
What are some ways we help pancreatic lipase digest fat?
Smooth muscle contracts to mix fats and disrupt larger molecules
Bile salts and phospholipids are amphipathic and act as emulsifying agents
What are micelles?
Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions
Used to transport digested lipids
Like an extra secure taxi
Too big to enter cells
How are fatty acids and monoglycerides sorted in the cytoplasm
Taken up by smooth ER
Triacylglycerol reformed
Coated with amphipathic proteins to not gum up the sER
Taken through golgi apparatus in vesicles to the BL membrane
Exocytosed as chylomicrons
What are chylomicrons?
Lipoprotein particles that consist of triglycerides, phospholipids, cholesterol, and proteins
They transport dietary lipids from the intestines to other locations in the body.
How do chylomicrons enter circulation?
Cannot enter capillaries so must go through lymphatic system
Lacteal in villi
Right lymphatic duct
SVC
Circulatory system
Which vitamins follow the same pathway as fats as they are fat soluble?
A, D, E, K
Which vitamins either follow passive transport or have transporters as they are not fat soluble?
B, C, Folic acid
How is Vitamin B12 processed?
Binds to intrinsic factor
This complex is recognised and taken up in the distal ileum
Stored in liver
What is one thing B12 is essential for?
Maturing red blood cells
How may a gastrectomy affect vitamin absorption?
Lack of intrinsic factor reduces B12 absorption
How is iron processed?
Transported using DMT1 (H+ dependent so needs acid microclimate)
Incorporated into ferritin
Iron in blood binds to transferrin
Too much iron in blood can lead to black stool
