Digestion and Absorption of Carbohydrates and Lipids (BIC 222)

Vocabulary flashcards covering the enzymatic digestion, absorption mechanisms, glucose transporters, and clinical disorders associated with carbohydrates and lipids based on the lecture notes.

Digestion

A process by which macromolecules in food are broken down into small molecule subunits that the body will absorb into the bloodstream for energy, repair, and growth.

Mechanical digestion

The process in which food is broken down into smaller pieces by chewing with teeth and continuing in the stomach through peristalsis contraction.

Chemical digestion

The process of breaking down large food molecules into their chemical building blocks, such as simple sugars and amino acids, achieved by digestive enzymes.

Salivary amylase

An enzyme in the mouth that breaks down long glucose molecules of starch into shorter chains by hydrolyzing internal $\alpha 1 \rightarrow 4$ glycosidic linkages.

$\alpha$-Dextrinase

A brush border enzyme in the small intestine that breaks down $\alpha$-Dextrins into glucose.

Sucrase

A brush border enzyme in the small intestine that breaks down sucrose into glucose and fructose.

Maltase

A brush border enzyme in the small intestine that breaks down maltose into two units of glucose.

Lactase

A brush border enzyme in the small intestine that breaks down lactose into glucose and galactose.

Lingual lipase

A salivary enzyme secreted by the lingual gland that breaks down triglycerides into free fatty acids and monoglycerides.

Gastric lipase

A gastric enzyme secreted by chief cells in the stomach that breaks down triglycerides into fatty acids and monoacylglycerides.

Active transport

The movement of a substance across a cell membrane going from an area of lower concentration to an area of high concentration.

Facilitated diffusion

The movement of substances from an area of higher concentration to an area of lower concentration using a carrier protein in the cell membrane.

Co-transport

A process that uses the movement of one molecule through the membrane from higher to lower concentration to power the movement of another from lower to higher concentration.

SGLT1

Sodium Glucose Cotransporter 1; the protein transporter responsible for absorbing glucose and galactose into enterocyte cells.

GLUT5

A glucose transporter expressed predominantly in the small intestine that facilitates the diffusion of fructose.

GLUT2

A transporter that exports glucose, galactose, and fructose out of enterocytes into the blood; also removes excess glucose from the blood in the liver and kidney.

Micelles

Products of lipid digestion consisting of bile salts, fatty acids, monoglyceride, and cholesterol coated by phospholipid, which diffuse into mucosal cells.

Enterohepatic circulation

The process where bile salts are reabsorbed in the ileum and return to the liver via portal circulation to be recycled and re-secreted.

Chylomicron

A water-soluble lipoprotein made of triglycerides and cholesterol formed inside mucosal cells to transport lipids into the lymphatics.

GLUT1

A transporter for basal glucose uptake in erythrocytes and the blood-brain barrier; defects in this protein cause brain-related symptoms like seizures.

GLUT3

A neuronal glucose transporter found in the brain, placenta, and kidneys with a higher affinity for glucose than GLUT1, -2, and -4.

GLUT4

A transporter in muscle, fat, and heart cells whose activity is increased by the presence of insulin.

GLUT6

A lysosomal membrane transporter that does not mediate glucose uptake but modulates inflammatory responses in macrophages.

GLUT8

A transporter expressed in neurons and the acrosomal part of spermatozoa, playing a role in the energy metabolism of sperm cells.

Lactose intolerance

A digestive disorder caused by a deficiency of the enzyme lactase, leading to the accumulation of undigested lactose in the gut.

Irritable Bowel Syndrome (IBS)

A condition involving irritation of the small intestine leading to abdominal pain, flatulence, and unpredictable bowel movements like diarrhea or constipation.

Crohn's disease

A type of inflammatory bowel disease (IBD) affecting the large intestine that causes abdominal pain, severe diarrhea, and malnutrition.

Glucose-galactose malabsorption (GGM)

An inherited metabolic disorder caused by a mutation in the SGLT1 gene, preventing the small intestine from absorbing simple sugars.

Classic galactosemia (Type 1)

The most common and severe form of galactosemia characterized by a complete deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT).

Galactokinase deficiency (Type 2)

A deficiency of galactokinase 1 that typically causes the development of cataracts.

Hyperlipidemia

Also known as dyslipidemia; a condition of excess lipids or fats in the blood that increases the risk of heart attack and stroke.